A MINERALOGICAI. STUDY OF SOILS DEVELOPED
ON TERTIARY AND RECENT LAVA FLOWS
IN NORTHEASTERN NEW MEXICO

Thesis for the Dogm of Ph. D.
MICHIGAN STATE UNIVERSITY
Bonnie L Allen
1959

 

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This is to certify that the
thesis entitled

A Mineralogical Study of Soils Developed on
Tertiary and Recent Lava Flows in
Northeastern New Mexico

presented by

B. L. Allen

has been accepted towards fulfillment
of the requirements tor

PhoDo degree in 5011 SCienCe

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A MINERALOGICAL STUDY OF SOILS DEVELOPED ON TERTIARY AND

RECENT LAVA FLOWS IN NORTHEASTERN NEW MEXICO

BY

Bonnie L. Allen

AN ABSTRACT
Submitted to the School of Graduate Studies of Michigan
State University of Agriculture and Applied Science
in partial fulfillment of the requirements for

the degree of

DOCTOR OF PHILOSOPHY

Department of Soil Science

1959

Approved ” ///// //L/ //"£t //’L£<f/

Bonnie L. Allen

ABSTRACT

Field studies were made of five soils in northeastern New Mexico
and one soil in southeastern Colorado which overlie basalts that vary in
age from probable late Pliocene to Recent. The climate ranges froa cool
subhunid to warm semiarid. Laboratory investigations were made on five
of the soils.

Field observations showed profile 1 to be a transitional Brunizem.
Profiles 2, 3, 4, and 5 were classed as Brown soils while profile 6 was
classed as a Calcisolic Brown soil.

A density separation of the sands and coarse silts was made at the
2.90 level using tetrabromoethane and centrifugation. A further separa-
tion was made at the 3.35 level using thallous formate as the heavy
liquid. The varied mineralogical composition of these fractions deter-
mined by petrographic analyses showed that most of the material in each
profile was not derived from the basalts.

lechanical analyses showed a very high silt content throughout nest
of each profile. This was interpreted as evidence of deposition of much
aeolian material.

Volcanic glass was found in some of the thin sections of the soils
as well as in some of the density separates.

Thin section studies on the basalts showed olivine to be highly altered
to iddingsite in the older rocks but to have suffered barely detectable
alteration in the youngest rocks. Plagioclase (labradorite) showed practi-

cally no alteration in the youngest flows when compared to the older ones.

 

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Bonnie L. Allen

Pyroxene (augite) remained remarkably fresh appearing through all the
sections studied.

The high total specific surface and high cation exchange capacity of
the unfractionated soils were interpreted as being indicative of much
expanding lattice clay. The silts and even the total sand of some of
the horizons of profile 1 possessed remarkably high exchange capacities.
This property was thought to be due to silt and sand sized clay aggre—
gates which had resisted dispersion and/or to transitional products of
a composition between primary minerals and expanding clay minerals. Ex-
change capacity neasurements were not made on the silt fractions from the
othersoils because there were insufficient quantities of some of the silts
from key horizons and also because of the limited time after discovery
of the phenomenon.

Profound differences were found to exist between the mineralogy of
the coarse (2.0 - 0.2 microns) and the fine ((10.2 micron) clays. These
differences were apparent from the results of the K20 analyses and the
x-ray diffraction patterns. The coarse clays were found to consist pri—
marily of quartz, illitic minerals, and kaolinite. The fine clays were
found to be mainly interstratified expanding lattice types. Soae showed

broad, but distinct, peaks between 14 and 17 I.

lost of the fine clays are thought to have been formed ig_gi£2 as
a result of weathering of volcanic ash and other materials of similar
weatherability. In the lower part of profile 1 they have foraed from
the basalt. Possibly some of the coarse clay as such was added in the

aeolian laterials. It is also quite possible that some of the illite

‘

 

Bonnie L. Allen

in the coarse clay may have formed through alteration of micas. Still

another possibility is the formation of illitic clays from the expanding

lattice types through the addition of potassium released in the weathering

of primary minerals. If the kaolinite was not added as a sediment, then

it may have formed through a desilication of the eXpanding lattice minerals

and/or illite. The formation from illite would also require a loss of

interlayer potassium.

The clay mineralogy indicated that these soils have been subjected

to weathering processes of moderate intensity.

A IINERALOGICAL STUDY OF SOILS DEVELOPED ON TERTIARY AND

RECENT LAVA FLOWS IN NORTHEASTERN NEW MEXICO

BY

Bonnie L. Allen

A THESIS
Submitted to the School of Graduate Studies of Michigan
State University of Agriculture and Applied Science
in partial fulfillment of the requirements for
the degree of

DOCTOR OF PHILOSOPHY

Department of Soil Science

1959

 

 

 

preting the results of the x-ray analyses. The author is indeed grate-

during the academic year 1954-1955 was sincerely appreciated.

Who helped without pay in the profile sampling, taking photographs, and

some of the routine laboratory work, profound thanks are extended.

In Memorium

Lon A. and Ida P. Allen

 

TABLE OF CONTENTS

Page
I NTRODUCT I ON 0 o e o o o o o o o o o o o o o o o o o o o o o o 1

REVIE' 0’ LITERATURE . . . . . . . . . . . . . . . . . . . . . . 3

Basic Weathering Studies . . . . . . . . . . . . . . . . . 3
Weathering of Basaltic Rocks . . . . . . . . . . . . . . . 13
Soils Formed from Basalts . . . . . . . . . . . . . . . . . 22
Weathering of Volcanic Ash . . . . . . . . . . . . . . . . 36
Natural Features of the Region. . . . . . . . . . . . . . . 40

[Geology . . . . . . . . . . . . . . . . . . . . . . . 40

Climate . . . . . . . . . . . . . . . . . . . . . . . 53

FIEI‘D STUDIES 0 O O O O O O O O O O O C O O O O O O O O O O O O 56
vegetation O O O O O O O C 0 0 O O O O I O O O O O O O O O 56
Sampling Procedures . . . . . . . . . . . . . . . . . . . . 57

Profile Descriptions . . . . . . . . . . . . . . . . . . . 65

umMTORY PRWEDURES O O O O O O O O O O O O O O O O I O 0 O O O 7 1-

Iechanical Analyses and Size Fractionation . . . . . . . . 71

Density Separations . . . . . . . . . . . . . . . . . . . . 76
Bulk Density fleasurements . . . . . . . . . . . . . . . . . 78
Organic Matter Determination. . . . . . . . . . . . . . . . 79
pH Measurements . . . . . . . . . . . . . . . . . . . . . . 79
Cation Exchange Capacity. . . . . . . . . . . . . . . . . . 79
Surface Area Measurements . . . . . . . . . . . . . . . . . 80
Total Potassium in Clay Fractions . . . . . . . . . . . . . 80
X-Ray Diffraction Procedures . . . . . . . . . . . . . . . 81
Differential Thermal Analyses . . . . . . . . . . . . . . . 85
Mineralogical Analyses of Sands and Coarse Si ts . . . . . 85
Thin Section Studies. . . . . . . . . . . . . . . . . . . . 87
DISCUSSION OF FIELD STUDIES . . . . . . . . . . . . . . . . . . 89
Profile 1 . . . . . . . . . . . . . . . . . . . . . . . . . 89
Profile 2 . . . . . . . . . . . . . . . . . . . . . . . . . :0
Profile 3 . . . . . . . . . . . . . . . . . . . . . . . . . 92
Profile 4 . . . . . . . . . . . . . . . . . . . . . . . . . 94
Profile 5 . . . . . . . . . . . . . . . . . . . . . . . . 95
Profile 6 . . . . . . . . . . . . . . . . . . . . . . . . .

DISCUSSION OF LABORATORY RESULTS . . . . . . . . . . . . . . . 96

Mechanical Analyses . . . . . . . . . . . . . . . . . . 96
Mineralogical Analyses of Sands and Silts . . . . . . . . 109
Thin Section Studies . . . . . . . . . . . . . . . . . . 127
Profilel.....................127
Weathered Basalt . . . . . . . . . . . . . . . 127

C1 Horizon-~Slide A . . . . . . . . . . . . . . 129

C1 Horizon-~Slide B . . . . . . . . . . . . . . 129

32 Horizon . . . . . . . . . . . . . . . . . . 130

Profile 3--Basa1t . . . . . . . . . . . . . . . . . 131

Site 4--Basa1t . . . . . . . . . . . . . . . . . . 138
Profile 6--Basa1t . . . . . . . . . . . . . . . . . 139
Basalt Encrusted with Caliche. . . . . . . . . . . . 141
Summary . . . . . . . . . . . . . . . . . . . . . . 143
Chemical Studies . . . . . . . . . . . . . . . . . . . . 144
Organic Matter . . . . . . . . . . . . . . . . . . . 144

PH . . . . . . . . . . . . . . . . . . . . 145
Total and External Specific Surface of
Horizon Samples . . . . . . . . . . . . . . . . . 145

Cation Exchange Capacity . . . . . . . . . . . . . . 149

Clay Investigations . . . . . . . . . . . . . . . . . . . 152
K20 Content . . . . . . . . . . . . . . . . . . . . 152
X—Ray Analyses . . . . . . . . . . . . . . . . . . . 154
Differential Thermal Analyses . . . . . . . . . . . 159
Summary of Clay Studies . . . . . . . . . . . 160
X-Ray Studies of Silts, Sands, and Weathered Basalt . . . 161

SMARY O O 0 O o o o o o o o o o o o e o e o o o e o o o o o l 75

BIBL-Immpm o o o o o o o o o o o o o o o o o o e o o o o e o 180

LIST OF FIGURES

1. Map of northeastern New Mexico showing the different

lava flows and sampling sites . . . . . . . . . .

f lava flows and vegetation on mesas:

2. Photographs 0
AlBictnyEgFoooooooooooc

3. Photographs of lava flows: A, B, C, D, E, F . . .

4A0 PrOfile NO. 1 o o o o o o o o o o o

4B. PrOfile NO. 2 o o o o o o o o O 0

4C. Weathering basalt on west end of Johnson

4D. Weathering basalt boulders in borrow pit
end Of JOhnson Mesa. 0 O O O O O O O O O O O

5A. Clayton flow scarp . . . . . . . . . . . .

SB. Surface of Capulin flow near Folsom . . . . .

6. Photomicrographs of Profile 1 . . . . . .

7. Photomicrographs of a weathered ash fragment and

caliche encrustations on basalt . . . . .

8. Photomicrographs of basalts . . . . . .
9. x-ray diffraction patterns of clays from profile 1 .

10. X-ray diffraction patterns of clays from profile 3 .

11. X-ray diffraction patterns of clays from profile 4 .

12. X-ray diffraction patterns of clay fractions from
profile 6 plus total clay from the AB horizon of
profile 1 and fine silts from profile 3. . . . . .

l3. Differential thermal diagrams of fine clay, coarse
clay, or total clay from profiles 1, 3, and 6 . .

14. X-ray diffraction powder patterns of silts, sands,

clays, and weathered basalts with a plated out
fine silt for comparison . . . . . . . . . . . .

Page

42

44
46
60
60

60

60

62

62

133

135
137
163
165

167

169

171

173

LIST OF TABLES

I. Climatic data from stations in the region .

II. Mechanical analyses, heavy mineral contents
().2,90 sp. gr.) of sand fractions and

bulk densities . . . . . . . . . . . . .

III. Relative percents of heavy and very heavy
fractions of sands and coarse silts . . .

IV. Mineralogical analyses of heavy fractions
of sands and coarse silts . . . . . .

V. Mineralogical analyses of light fractions
of very fine sand and coarse silt in

prOIile 1 O O . O O O C C C C C C O O 0

VI. Mineralogical analyses of light fractions
of very fine sands in profiles 3, 4, and 6

VII. Chemical prOperties of total samples and
K20 contents of clay fractions from

horizons . . . . . . . . . . . . . . . .

Page
53

98

103

115

125

126

147

INTRODUCTION

Basaltic lava flows occur extensively in northeastern New Mexico.

Most of the high mesas which are a striking feature of the landscape

are capped by these flows which vary in thickness from a few feet to as

much as 500 feet. Other flows are present which cap mesas that are per-

ceptibly lower. In addition, flows are present which occupy the lowest

portions of the landscape, i.e., stream valleys. The ages of these flows

range from Pliocene for the high level flows to Recent for the youngest

low lying flows. This appeared to be an ideal situation in which to

study the effect of time on soil formation.

Preliminary field studies showed that variables other than time

would have to be considered when studying the genesis of the soils over-

lying the various flows. The climate on the high mesas is obviously cooler

and more moist than that obtaining in the areas of the low lying flows.

Field studies showed also that there was reason to suspect that

extraneous materials had been added to the developing soils. This was

confirmed abundantly by the laboratory studies.

Because of the complicating factors it seemed improbable that an

adequate evaluation of the time factor could be made, and so the objectives

of the study were revised. Mineralogical and genetic studies of the soils

plus weathering studies of the underlying basalts were made. Special

attention was given to the determination of the types of foreign material

which have contributed to the soils.

2
It is hoped that the present study will clarify the nature of the
primary materials* in the area as well as present some worthwhile ideas
concerning the alteration of these materials and the underlying basalt

to form soils.

I"Primary materials as used in this work does not necessarily mean
the underlying basalt but the actual materials giving rise to the soil,
i.e., the initial state of the soil system.

REVIEW OF LITERATURE

Basic Weathering Studies

The literature concerning weathering in general, and crystalline

rocks in particular, is voluminous and no claims are made for the com-

pleteness of the review. However, an attempt has been made to review

some of the fundamental work, as well as some of the recent studies.

Goldich (22) has reported the study of the alteration of igneous

rocks, including diabase, in Massachusetts and Minnesota. In the Massa-

chusetts diabase most of the alteration was believed due to deuteric and

hydrothermal alteration. The plagioclase had altered to a felty mass of

sericite fibers, the pyroxene to hornblende, and the magnetite had a

rim of reddish-brown biotite surrounding it. In the Minnesota diabase

pronounced mineralogical changes were not evident in the relatively short

post-glacial period. However, it was noted that a small amount of chemi-

cal change in the early stages of weathering was effective in bringing

about a striking change in coherence and coloration. As a result of his

studies Goldich proposed the folowing stability series.

Calcic Plagioclase

Olivine
Augite Calcic-alkalic Plagioclase
Hornblende Alkali-calcic Plagioclase

Biotite Alkalic Plagioclase

Potash Feldspar
Muscovite

Quartz

4

Magnetite and ilmenite could be classed as moderately stable, prob-
ably of the same order as muscovite. Zircon could be classed as most
stable. Goldich theorized that the differential between equilibrium
conditions existing at the time of formation and those existing at the
surface is the factor governing the order of stability.

Dryden and Dryden (16) studying the weathering of the Wissahickon
schist from Pennsylvania and Maryland proposed the following values for

resistance to weathering of the various heavy minerals, using garnet as

a basis.
Zircon 100 Kyanite 7
Tourmaline 80 Green Hornblende 5
Sillimanite 40 Staurolite 3
Monzonite 40 Garnet l
Chlorotoid 20 Hypersthene l

The most surprising result of this study is the susceptibility of
garnet and the relative positions occupied by it and hornblende. The
authors concede that varietal differences may alter greatly the posi-
tion of a mineral in the order. Zircon showed no evidence whatever of
weathering.

Jackson and Sherman (36) in an extensive treatment of chemical
weathering of minerals in soils give a weathering sequence from least
to most stable for colloidal size minerals as follows.

(1) Gypsum (also halite, sodium nitrate, ammonium
chloride, etc.)

(2) Calcite (also dolomite, aragonite, apatite,
etc.)

(3) Olivine—hornblende (also pyroxenes, diopside,
etc.)

(4) Biotite (also g1auconite,magnesium chlorite,
antigorite, nontronite, etc.)

(5).A1bite (also anorthite, stilbite, microcline,
orthoclase, etc.)

(6) Quartz (also cristobalite, etc.)

(7) Muscovite (also 10 A zones of sericite, illite,
etc.)

(8) Interstratified 2:1 layer silicates and vermi-
culite (including partially expanded hydrous
micas, randomly interstratified 2:1 layer sili-
cates with no basal spacings, and regularly
interstratified 2:1 layer silicates)

(9) Montmorillonite (also beidellite, saponite,
etc.)

(10) Kaolinite (also halloysite, etc.)

(11) Gibbsite (also boehmite, allophane, etc.)

(12) Hematite (also goethite, limonite, etc.)

(13) Anatase (also zircon, rutile, ilmenite, leu-
coxene, corundum, etc.)

The mineral listed first is given as a representative type mineral
for that stage. This sequence has been derived primarily from an earlier
published work of Jackson, et a1 (35). However, Sherman and Jackson
have incorporated the results of studies made by some additional investi-
Sators in listing some of the above minerals.

In the earlier work of Jackson and co-workers (35), the following

generalizations concerning the weathering sequence are made.

(1) From three to five minerals of the weather-
ing sequence are usually present in the
colloid of any one soil horizon. There is
a tendency for the compositions of the col-
loid to be in the form of a distribution
curve, being dominated (40—60%) by one or
two minerals with other adjacent minerals
of the sequence decreasing in amounts with
remoteness in the sequence.

(2) The percent of minerals in the early stages
of the weathering sequence in a soil clay
fraction decreases and the percent of the
successive members increases, with increas-
ing intensity of weathering.

(3) One to three intermediate stages may occa-
sionally be absent from the normal sequence,
particularly those following quartz, giving,
for example, a quartz-kaolinite-gibbsite

colloid.

(4) One or more stages may occasionally occur
out of sequence as secondary deposits,
particularly gypsum and calcite.

Jackson (35) expresses mathematically his idea of weathering stage

being determined by several factors as:

Weathering stage
T

H20

.5

H
6.5

zrcr, H20, if , as, s, k... t)

temperature
rate of leaching or water movement

acidity of the solution

degree of oxidation (electron
density) and its fluctuation
(oxidation-reduction)

specific surface of the'particles

specific nature of the mineral
being weathered

time

Jackson, et a1, (37) have set forth the following principles for

recognizing successive stages in chemical weath

ering of the layer lattice

silicates from stages 4 and 7 to 9 as follows:

(1) In X-ray analysis a decreasing in intensity
and a broadening of angle of basal diffrac-
tion while the llO-lines are retained. This
is interpreted as indicating disorder along
the 001 planes.

(2) Appearance of intermediate basal spacings

(3) Increase in internal surface as exemplified
by montmorillonite having approximately
800 mZ/gm as compared to the ideal mica
having none.

(4) Loss of K from between mica crystal layers
(mica / expanded spacings 3 illite, sericite,
glauconite, etc.). This is called "depotas-
sication." The necessary decrease in inter-
layer charge density may occur through the
oxidation of trioctahedral ferrous to ferric
iron in the biotitic micas. It may occur in
dioctahedral micas by hydroxylation or dealumi-
nation.

(5) A higher H20 or OH content than theoretical,
called hydroxylation.

(6) A decrease in the alumina content of the tetra-
hedral layer--dealumination.

(7) The removal of silica from 2:1 layer silicates
to form kaolinite and gibbsite—-desilication.

Jackson and associates make some generalizations regarding the
interaction of chemical weathering reactions with other soil forming

processes. Calcification and salinization proceed under neutral to slightly
alkaline conditions, and are accompanied mainly by the mica weathering
reactions of depotassication, stages 7 to 9 and deposition of Ca003 and

CaSO4 plus other salts of weathering stages 2 and 1.

8

Barshad (5) states that the relative stability of minerals to weather-

ing and decomposition with acids appear to be related to the degree of

basicity, degree of linkage of the tetrahedrons, relative number of alumina

and silica tetrahedrons, and other factors that induce a lowering of the

basicity of the mineral and a destruction of bonds linking the tetrahe-

drons. In addition Barshad gives the following factors as affecting the

stability of minerals:

(l)

(2)

(3)

(4)

(5)

The presence of ferrous iron or other cations
that may oxidize during weathering greatly
reduces the structural stability, for upon
oxidation some other cation must leave the
structure to maintain the electrostatic neu-
tality of the crystal lattice.

The more closely the oxygens are packed about
the cation other than in tetrahedral positions
the more stable is the mineral. The great
resistance of zircon, with a unit cell of

231 A3 as compared to olivine with a unit

cell of 291 A is cited as an example.

The greater the number of empty positions
in the lattice the easier it is for ions
to enter and depart from the lattice. This
will facilitate breakdown.

Since breakdown in weathering is primarily
due to the exposure of unit cells at the
surface in minerals not having channels or
defects the more of such cells exposed the
more unstable is the mineral. The number
of such cells exposed is reflected in the
shape of the particle--plates, rods, etc.--
and their sizes.

The relative stability of a given mineral
may be affected by the nature of the other
minerals associated withit through their
effect on the composition of the solution
in contact with the mineral. Contact
between the solid phases may also enter in.

9
Barshad (5) generalizes further concerning the breakdown of silicate

structures as follows:

(1) In silicates with independent silica tetrahedra,
81:04 ratio, the weakest bond (through the
metallic cation) binds the tetrahedra together.

(2) In the chain structures, pyroxenes, with a
81:03 ratio, and amphiboles, with a 814:011
ratio, the weakest bonds bind the chains to
each other.

(3) In the sheet structures, micas, with a 814:010
ratio, the weakest bond binds the sheets together.

(4) In structures with three dimensional linkage
of the tetrahedra, i.e., feldspars, feldspa-
thoids, etc., with a (A1, Si):02 ratio, the
weakest bond binds the cations that balances
the charge deficiency created by alumina tetra-
hedra.

Fields and Swindale (21) have arranged a silicate stability series,
consisting of five groups, along with their successive weathering prod-
ucts. The conclusions are based primarily on their investigation of a
variety of New Zealand soils along with some tropical soils from the
Cook Islands. In Group 1 are listed olivine, augite, hypersthene, and
hornblende. These silicates have discrete tetrahedra, single chains,
or double chains. In Group 2 basic volcanic glass (amorphous) and zeo~
lites (three dimensional structure*) occur. Biotite and muscovite (three

layer sheet structures with hexagonal linkage) are in Group 3. Acidic

*Swindale and Fields refer to the three dimensional silicate struc-

tures as linked tetrahedra.

10

volcanic glass (amorphous) and feldspars (a three dimensional structure)
are listed in Group 4. Quartz (three dimensional structure with no tetra-
hedral substitution) comprises Group 5.

Fields and Swindale found that in mature basaltic soils the mineral
colloids consisted primarily of geothite, gibbsite, boehmite, and ana-
tase with small quantities of kaolinite. Clays from immature basaltic
soils were found to contain high amounts of amorphous oxides and little
crystalline material. Silica not leached was believed to combine with
alumina to form kaolinite. It was conceded that montmorillonite also
could be formed by resilication during weathering of basalt; however, it
was not found in soils from basalt or andesite, but was detected in a
hand specimen of weathering andesite. It was concluded that these mater-
ials are the principal weathering products of Group 1 silicates.

By using evidence from soils showing different degrees of maturity
deve10ped primarily from basic volcanic glass (Group 2), it was concluded

that allophane and amorphous oxides of iron, aluminum, and silicon were

intermediate products. Kaolinite and montmorillonite, believed to form

by resilication, were found in older ash derived soils. x-ray diffrac-
tion, differential thermal analysis, petrological examination, electron
micrography, and chemical determinations were used as criteria.

Group 3 minerals, the micas, were found primarily in sediments,
shales, and schists. Fields and Swindale make the following conclusions

regarding the alteration of these minerals. It will be noted that they

are not in complete agreement with Jackson (37).

11

(1) Hydrogen ions are required to remove inter-
layer potassium to form illite and expand-

ing micas.

(2) When both hydrogen and calcium ions are in
appreciable concentration, the hydrogen ion
is effective in making interlayer surfaces
accessible to calcium which in turn assists
the development of a fully expanded montmoril-

lonite.

(3) Under acid leaching at high pH* the high
concentration of hydrogen ions accelerates
the alteration to clay-vermiculite.

(4) Continued weathering under acid conditions
is capable of degrading either kaolinite
or montmorillonite and thence to form second-
ary silica. This is believed to occur through
the action of the acid solution, which per-
meates the interlayer region, on the alumina
in tetrahedral coordination. Probably these
processes do not happen simultaneously on
both tetrahedral sheets. Therefore, kaolinite,
a more stable structure, is the result. Con-
tinued acid action dissolves the octahedral

alumina.
(5) Under conditions of high alkalinity, the
alkaline earth cations are effective in

converting any hydrous mica to fully
expanded montmorillonite.

(6) Except in extreme conditions a combination
of processes produces mixed clay minerals.

X-ray analysis showed that the micaceous clays contained structures

with appreciable interstratification.

The acidic volcanic glass, which fields and Swindale tentatively

Place in Group 4, weathers to amorphous hydrous oxides like the basic

 

*It is believed that "high pH" here means "low pH" as used in America.

12

glass but at a much slower rate. Feldspars are believed to be first
reduced to a gelatinous amorphous material. This is thought to occur
slowly in soils, but then this material is resilicated rapidly to form
kaolinite. The fact that clays produced from primary material high in
feldspar consist mainly of kaolinite is explained thusly.

Quartz is the only mineral in Group 5. It was concluded that semi-

mature ash soils contained amorphous secondary silica but that soils of

greater age contained a material called "chalcedonite,' a material resem-

bling chalcedony but with a lower refractive index. Fields and Swindale
concluded that the amorphous hydrous silica or colloidal silicic acid
was likely to be an intermediate between any of the crystalline silicates
and the "chalcedonite." The reader should note that these authors con-
sidered quartz a silicate, probably for convenience, when in reality it

does not meet the definition of a silicate.

Stephen (71), as a result of studies on crystalline rocks in England,

states that the following sequences occur in the weathering of an appinite.*

Hornblende-éChlorite-eflixed layer chlorite-vermiculits-)Vermiculite

Peldspar -----------
}-9 Illite

Hydromuscovite -----

In the study on "ivy—scar" rock (composed of 22% hornblende and 48%

plagioclase feldspar), Stephen (71) found the weathering sequence of

 

IAppinites are generally composed almost entirely of hornblende and
andesine or oligoclase. The rock studied by Stephen contains considerable
Quantities of clinozoisite, chlorite, and hydromuscovite which are thought
to be hydrothermal alteration products.

l3
hornblende to be similar as that in the previous study and the plagio-

clase feldspar weathered as shown below:

Under acidic conditions: Feldspar-alllite-exaolinite
Under alkaline conditions: Feldspar-§Illite-)lontmorillonite
It was also suggested by the study on the ivy—scar rock that born-

blende was a less stable mineral than feldspar. The basis for this con—
clusion was the 1:1 ratio of the chlorite-vermiculite to illite-kaolinite
in the overlying soil as compared to 1:2 ratio of hornblende to feld-
spar in the parent rock. It should be noted that illite formation from
plagioclase necessitates the addition of potassium ions. In the study
of the ivy-scar rock Stephen does not account for this; however, in the
study of the appinite, it is presumably explained by the addition of

potassium in the hydrothermal alteration of the plagioclase to form

hydromuscovite.

Weathering of Basaltic Rocks

Humbert and Marshall (34) in their studies of the weathering of a
granite and a diabase in southeastern lissouri reported that changes

occurred in the minerals of the diabase as follows:

Plagioclase (labradorite) to saussurite

Augite to uralite (amphibole) associated with
secondary magnetite, epidote, chlorite, and cal-
cite. Purther alteration produced a micaceous-

like mineral.

Olivine to a pleochloric green material appear-
ing to be fibrous hornblende or actinolite

14

Titaniferous magnetite and ilmenite to leu—
coxene

Epidote was reported as a secondary mineral

in the rock and was explained as an alteration
product of plagioclase with the necessary iron
coming from the breakdown of the ferromagnesian

minerals.

In the heavy mineral studies on the diabase profile, a relative

decrease in magnetite and ilmenite and in augite in the fine and very

fine sand with depth was reported. There was an increase with depth

in the compound aggregates (composed of magnetite, ilmenite, augite,

feldspar, etc.). Biotite showed an increase in the 82 and the upper C

horizons in the same size fractions. In the coarse silt fraction there

was a decrease in the black Opaque, epidote, tourmaline, and zircon con-

tents with depth. There was somewhat of a decrease in rutile with depth,

although this was not a constant relationship. There was a marked in-

crease downward in the profile of augite, hornblende, apatite, and chlo-

rite. Biotite increased with depth until the lowest horizon recorded

was reached, and then a decrease was noted. The increase in hornblende

was attributed in part to that formed from augite. In an analysis of the

light minerals from the diabase, quartz decreased markedly with depth

in every size fraction. The same was true for chalcedony excepting the

0.25 - 0.05 mm fraction. There was a pronounced increase in the feldspar

content. (No mention was made of the relative proportions of potash and

Plagioclase feldspars.) It was believed that the labradorite was changed

to more sodic plagioclase feldspars as calcium was lost from the lattice.

Also, alteration to sericite and clay minerals was reported as occuring

15

in these fragments. In the 0.25 - 0.05 and 0.05 - 0.02 fractions, the
mica content increased several fold as the lower horizons were reached.
This was thought to be due to the weathering of the hornblende. This
mica in turn was reported as altering to clay minerals. The clays in
the diabase profile were interpreted as being essentially "beidellite"
with some "micaceous crystals" and lesser quantities of halloysite. These
interpretations were based principally on studies of electron micrographs.

Marshall and Humbert interpreted the relative increases and decreases
in the diabase profile as being strictly a weathering phenomenon. No
mention was made of possible admixture of foreign materials. Neither
was deuteric alteration of minerals in the parent rock discussed.

One of the features of weathering basalt that has held the attention
of investigators for some time has been the alteration of olivine to
the mineral iddingsite. There has been a divergence of opinion, even up
to the present time, whether it is an alteration product of deuteric
action, of weathering, of neither process, or a combination of both.
Since the basalts studied in this investigation show conspicuous pheno-
crysts of iddingsite or olivine rimmed with iddingsite, the literature con-
cerning iddingsite was searched rather thoroughly.

Ross and Shannon (64) in an early study of basalts from New Iexico,

Colorado, and Idaho concluded that it was an alteration product formed

near or Just after the close of crystallization and after the magma came

to rest. Their conclusion was based upon the following thin section obser-

vations:

16
(1) It was not confined to weathered surfaces.

(2) Its deve10pment showed no proximity to join
cracks.

(3) Evidence of weathering in associated minerals
was absent.

(4) Normal products of weathering such as limonite
were absent, but spinel--a mineral not ordi-

narily produced by weathering--was present in
considerable quantities.

Ross and Shannon stated that in order for iddingsite to form, an
olivine of suitable composition must be present. A concentration of
mineralizers, principally water, oxidizing conditions, and heat are
also necessary.

Edwards (17) studying basalts from Victoria, Australia, believed
that not only was it necessary for the magma to be rich in water vapor,
but that it was necessary for it to have differentiated in such a manner
as to give rise to an iron-rich final fluid. He found that those basalts
rich in iddingsite possessed iron-rich glasses, while in those in which
the iron oxides had completely crystallized, no iddingsite was found.

Obviously, Edwards believed it to be formed through a process of

deuteric alteration.

Stearns (69) reported extensive iddingsite occurrence in vitric

tuffs and basaltic flows from Oahu, Hawaii. He found that in the flow

from Kuwala Ridge the olivine in the upper part had largely altered to

iddingsite, but in that collected near the base, iddingsite was nearly

absent, and the olivine had undergone extensive alteration to pale green

serpentine.

 

17

Stearns and MacDonald (70) found that in basalts of the Wailaku
volcanic series from Maui, Hawaii, the olivine around edges and along
fractures was altered to iddingsite, but that other olivine grains exhi-
bited only a faint greenish stain resulting from incipient alteration.
In one specimen finely granular iron ore was found to be closely asso-
ciated with rims of iddingsite around the olivine phenocrysts. Stearns
and MacDonald interpreted the presence of calcite and zeolite (7) in the
vesicles of some cavities along with extensive alteration of olivine to
iddingsite to suggest that the flows had been exposed to volatiles.
However, the occurrences of the iddingsite along cracks and edges of
crystals and near the top of flows may suggest a weathering influence.
The age of the Wailaku series is given as probably Pliocene and early
Pleistocene.

Ming-Shan Sun (74) in a study on iddingsite in basalts from New
Mexico and Colorado believed the alteration to be largely accomplished
in the deuteric stage and stated that it may or may not be continued in
the weathering process. He concluded from the results of x-ray powder
analyses that geothite was the only crystalline substance present and
that the other substances shown by chemical analyses were largely amor-
phous magnesia and silica. One of the requirements set forth for the
formation of iddingsite in the late deuteric stage is for the olivine to
contain appreciable amounts of iron. This iron of the olivine, which
is in the lower oxidation state, is oxidized to Fezoa.

Wilshire (83) recently has stated that chlorites and "smectite"

Occurring in soils derived from basic volcanic rocks cannot be assumed

18

to have originated by weathering.* In studying basalts from California,
the freshest rocks were found to contain green alteration products of
olivine consisting of trioctahedral smectite—chlorite aggregates while
the most highly weathered rocks contained oxidized "smectite~chlorite"
and goethite. By studying the 060 X-ray lines it was found that the
higher the degree of weathering the more closely the material approached
a dioctahedral structure. Wilshire believes that structural types repre-
sented by deuteric alteration products (smectite-chlorite) are stable in
the weathering environment, and the conversion of these to dioctahedral
structures will lag behind the alteration of the plagioclase and pyroxene.
This was based upon the observations of iddingsite in highly weathered
porous specimens. Wilshire believes iddingsite to be a mixture of chlo-
rite-smectite and goethite and that it is formed from the "smectite-
chlorite" by leaching iron which is being deposited in it as goethite or
by weathering of the included magnetite. There is a loss of magnesium
relative to iron during this process. According to Wilshire, iddingsite
represents at least two minerals and possibly as many as three or four,
and this accounts for the variable eray results and indefinite optical
properties.

In addition to the smectite-chlorite and goethite, quartz and cal-

cite are common constituents; talc and mica are listed as rare constituents.

*Grim (25) states that minerals described as smectites have been
shown to be montmorillonites and although smectite is an earlier name,
it has fallen into disuse and should be discontinued. However, the term
will be used in reviewing Wilshire's work.

19

Wilshire states that orthopyroxene, as well as olivine, alters to
iddingsite. In many of the vesicles a material very similar in Optical
and x-ray properties to the smectite-chlorite was identified.

lilshire studied a colorless clay pseudomorphing clinopyroxene-
plagioclase aggregates in some of the basalts and found it to be com—
posed in part of smectite—chlorite but also had kaolinite as part of the
pseudomorph.

Brown and Stephens (71) have made an excellent very recent study
on iddingsite from Australia. A number of new concepts regarding the
structure of iddingsite are brought out in their study. In the basalts
studied some olivine grains had been altered completely to iddingsite,
but most still had a core of olivine. They believed the iddingsite was
probably of deuteric origin.

Brown and Stephens found the iddingsite to have a tabular habit with
one well developed cleavage and to extinguish parallel to the cleavage
trace. It was found to be optically negative, to have a 2V of 30-400
and have distinct dispersion with r<v. The refractive indices were:

91- 1.67 - 1.68 and f = 1.71 - 1.72 which gave a birefringence of
approximately 0.04. The homogeneous Optical characteristics occur be-
cause the small crystals Of both components are strictly aligned through-
out the structure due to the inheritance (only partially in the case of
the layer silicate) of the framework of the olivine.

The x—ray analysis showed a reflection at 15.6 A and the character-
istic reflection of goethite. This basal spacing could not be increased

with water, ethylene glycol, or glycerol, but it could be decreased to

20
1013 after heating for one hour. These properties were interpreted as
indicating a vermiculite or "smectite" structure. In the layer lattice
silicate much disorder appeared to be present in the stacking.

Brown and Stephens believe that the alteration of the olivine struc—
ture occurs layer by layer and that little structural change is neces-
sary to form goethite since both structures are based on a hexagonal close
packing of oxygen sheets. The cation replacements and rearrangements can
occur by ionic diffusion. The alteration to a layer lattice structure is
more complex since some breaking up of the close packed framework of the
olivine is necessary. However, only a few of the 81—0 bonds would need
to be broken. Little is known concerning the chemical changes which
occur; but since the density of the iddingsite is lower than that of the
olivine, obviously some material is lost. They think that some magnesium
and silicon is lost relative to iron and that H20 is added.

Hay (29) in a recent study of Pleistocene andesitic ash deposits
on St. Vincent, B. V. 1., has found the primary minerals to weather as

described below.

Vitric material. Halloysite.4H20 is the princi-
pal silicate clay present in most samples with
kaolinite present in a small percentage of the
samples and predominating in a few. Montmoril-
lonite is present in small quantities in several
samples. The clay minerals were identified by
X-ray diffraction patterns. The halloysite which
has migrated to coat and fill cavities in the
ash appears as waxy, visibly crystalline, and
yellowish orange (stained with limonite?) in
both transmitted and reflected light.

Plagioclase. The crystals are etched and re-
placed by halloysite. The contact between

21

plagioclase and halloysite is sharp, and the
plagioclase adjacent to the etched surfaces
and pseudomorphs appears unaltered. Petro-
graphic evidence suggests that halloysite has
precipitated in cavities created or enlarged
by solution of the plagioclase.

Pyroxene. Alteration consists of etching prin-
cipally with many crystals having coatings of

a silky fibrous material of unknown composition
covering the prismatic faces.

Olivine. Many crystals are completely or partly
replaced by iddingsite while others consist of
etched nuclei of fresh Olivine enclosed by a

mantle of iddingsite. "The latter is absent in
olivine crystals of unweathered deposits and its
thickness is proportional to the overall weather-
ing of the ash, hence it is a product of weather-
ing, not of deuteric alteration," Hay reports.

It is believed that the nature and degree of altera-
tion depends principally on the composition of the
olivine. The more ferriferous (F074) are generally
altered more than those higher in magnesium (F073-85);
this is believed due to the presence of unstable
ferrous ions. Petrographic evidence suggests that
iddingsite is a direct replacement of olivine and
was not precipitated in solution cavities.

Hay calls the soil derived from the ash a "Yellow Earth" and believes
it to represent an early stage in the development of "lateritic" red

soils.

It is obvious from the preceding discussion that there is still
considerable disagreement concerning the formation of iddingsite. It
is noteworthy that the last four works cited, in which there is considerable
disagreement, have all been published since 1957. There seems to be some
agreement that there is a tendency for the plagioclase feldspars to weather
into kaolinite, especially if there are no basic cations from the adjacent

ferromagnesian minerals. There is a paucity of information concerning the

22
singular weathering products of augite. There is general agreement that

it does not weather as readily as many of the other ferromagnesian minerals.

Soils Formed from Basalts

 

Basaltic soils have interested pedologists for many years because
of the great areal extent of basaltic lavas in many parts of the world
and because of the unusual properties of many of the soils derived there~
from. However, very little work on the genesis and mineralogy of such
soils has been conducted in the continental United States. Most of the
work has been done in tropical regions; although, some excellent studies
have been made in Australia and, recently, considerable interest has been
shown in the basaltic soils of Iceland.

Betzer (60, 61) has studied some of the basaltic soils of Western
Colorado. The first report consisted principally of a field examination
with some particle size studies and a cursory mineralogical examination
of the sands. The basalt was of late Tertiary age. The east end of the
mesa had been glaciated but the west end on which the study was made showed
no evidence of glaciation. Profile examination showed that the soils have
restricted internal drainage due to the presence of a dense clay pan which
is often several feet thick. Mechanical analyses showed silt to be the
dominant textural separate in each horizon excepting the 82 where sand
and silt were 35% each. The clay content was surprisingly low in the
upper horizons, being only 4 and 8%, respectively. In the sands mica,
hornblende, quartz, limonite, magnetite, and opal were observed. There

was no evidence of volcanic glass. Retzer does not satisfactorily explain

23

the presence of quartz or, for that matter, hornblende and mica. He
states, "quartz suggests wind deposited material," (but it) "seems doubt-
ful that wind deposited dust has been greater on the mesa than can rea—
sonably be expected for nearly all land surfaces of the earth." Large
quantities of basalt fragments were found through the solum which indi-
cates that the soil probably developed mostly from basalt.

In Retzer's later work (61) a mineralogical study was made of the
fine silt (2 - 5 microns) and three size fractions of clay in the B
horizon of a soil profile derived from basalt at 12,400 feet near Lead-
ville, Colorado. The fine silt consisted of illite, orthoclase, chlo-
rite, and quartz mainly. A trace of montmorillonite was present. The
coarse clay(2.0 - 0.2 microns) was found to be made up mostly of montmoril—
lonite—vermiculite (40%), kaolinite-chlorite (20%) intermediates, and
illite (20%). Lesser quantities of quartz and orthoclase were reported.
In the medium sizes (0.2 - 0.08 microns) clay the montmorillonite-vermi-
culite intermediate was estimated at 30%, a "hydrous clay intermediate"
at 25% and lesser quantities of illite (20%), kaolinite-chlorite, and quartz.
In the fine clay ((0.08 microns) respective estimates were made of mont-
morillonite, "hydrous clay intermediate," and illite at 30, 25, and 20%.
Quartz and kaolinite were the other minerals reported. NO explanation
is offered regarding the origin of the quartz or orthoclase. It is of
interest to note the reported occurrence of such large quantities of the
intermediates in the larger size fractions.

Among the Australians, Hosking (31) has made some fundamental miner-

alogical studies on the clays of soils formed from basalt and associated

 

25

Carroll (12) in a study of soils overlying basalts in the 0rd
River Valley of Western Australia stated that the soil could not have
been derived from the basalt with the heavy mineral suite containing
such minerals as blue-green hornblende, tourmaline, garnet, and anda-
lusite. This is worthy of note in the light of the conclusions drawn
by Humbert and Marshall (34) that a similar suite of minerals was of
residual origin. It is believed that the blue-green hornblende of
Carroll is the same as the "uralite" of Humbert and Marshall.

Hallsworth, et a1, (26) have made a study of the complex catenary
relations and of the clay mineralogy of the soils on basalt in New South
Wales. The catenary and climatic relations between soil groups are

summarized below:

Moderate Rainfall High Rainfall
Part of Low Rainfall (25-35 in.) (35—55 in.)
Catena (17—25 in.) (Colder Temperatures) (Low Temperatures)
Upper Reddish Grey Chocolate Alpine Humus
Chocolate
Middle Normal Grey Chocolate Alpine Humus
Chocolate
Lower Chernozems Prairie and Meadow Bog
soils
(Moderate temperatures) (Moderate tempera-
tures)
Upper Normal Chocolate Krasnozems
Middle Normal Chocolate Krasnozems
Lower Grey Chocolate, Prairie and

Prairie and Meadow Meadow

Part of
Catena

Upper

Middle

Lower

26

Moderate Rainfall High Rainfall
Low Rainfall (25-35 in.) (35-55 in.)
(17-25 in.) (High Temperatures) (High Temperatures)

Some Chocolate and Krasnozems or

Reddish Chocolate Transitional
Krasnozems

Black and brown Normal

Chernozom-like soils Chocolate
Prairie

With rainfall greater than 55 inches in the high temperature regions,

the Xrasnozems occupy all positions of the catena.

The clay mineralogy of the soils studied by Hallsworth, et al, is

summarized below:

Chernozems: Montmorillonite is dominant with a
small amount of kaolinite and traces of illite

and quartz.

Reddish Chocolate: There is about twice as much
montmorillonite as kaolinite.

Normal Chocolate: There is less montmorillonite
and a corresponding rise in illite with kaolinite

remaining about the same.

Grey Chocolate: Kaolinite is dominant with mont-
morillonite remaining about the same. No illite

is present.

Krasnozems: Kaolinite is dominant and considerable
quantities of iron and aluminum oxides are present.
No illite or montmorillonite is present.

The following statement was made regarding illite. "The presence

of illite in soils derived from basalt is surprising but it is presented

without comment at this stage."

27

Hallsworth, et a1, postulates that increased leaching and deple-
tion of the bases promote kaolinite formation. Conversely, accumu-
lation of drainage water (may be through downslope seepage) plus dis-
solved bases encourage the synthesis of montmorillonite. Topographic
and climatic relations both influence these relations.

Ferguson (20), studying soils on Tertiary basalts in southeastern

Queensland reported similar topographic relations between the red"

and "black" soils. Black soils were also reported as occurring on
slopes where little weathering could occur and on savannah areas. The
black soils were found to contain a dominantly montmorillonitic clay
which was thought to be nontronite. The red soils were found to be
primarily kaolinitic but with variable amounts of montmorillonite
depending upon the horizon within the profile as well as the prevailing
climate. Ferguson proposes that the black soils tend to change into

the red soils, accompanied by a decomposition of montmorillonitic
minerals to kaolinitic materials. At the same time there is a loss

of alkaline earths (presumably exchangeable cations) and iron from the
montmorillonitic minerals with the iron becoming stabilized as oxides
in the upper horizons. Although kaolinite may be protected from rapid
decomposition, it may eventually decompose to produce gibbsite which is
also stabilized in the ferruginous zone. Ferguson postulates that once
the climate succeeds in producing a red lateritic soil there is little
chance of a change occurring in the reverse direction owing to the diffi-
culty of resynthesis of montmorillonite in the absence of alkalis and

excess silica. Radoslovich (59) has reported somewhat similar mineralogical

28

data for some red—brown earths of South Australia. He found the
basalts to contain more kaolinite and less illite than associated
alluvium. He found two sons developed from dolerite* to have no il-
lite. He found the illite in basaltic soils to be deficient in struc-
tural potassium, containing only about 2.5 - 4.1%.

Colwell (14) has recently completed a study of the surface hori-
zons of the Krasnozems on basalts in New South Wales. The free Fe203
content of these soils ranged from 14.2 to 22.2% and these represented
from 69 to 86% of the total iron. In contrast the free A1203 values
ranged from 1.4 to 5.7 and this represented only about 20% of the
total aluminum. ,As would be expected, the clays were found to consist
predominantly of kaolinite, hematite, goethite, and gibbsite. Some
illite was found in most of the profiles. Small amounts of quartz,
lepidocrocite, ferric oxide gel, and vermiculite or chlorite was pre-
sent in some of the soils. Amorphous material was believed to be promi-
nent in several soils. The presence of illite and quartz is not ex-
plained. As would be expected, the cation exchange capacity of the
inorganic component was found to be very low, ranging from zero to
8.6 me/100 gm.

Tiller (77) has very recently reported on a study of the geochemistry
of basaltic materials and associated soils of South Australia. It was
found that olivine weathered readily to a light brown unidentifiable

isotropic material on the edges and sometimes along fractures of the

l"The American equivalent of dolerite is diabase.

 

29

crystal.* Magnetite was reported as being a weathering product of
olivine, even to the point of being pseudomorphous after it. The soil
consisted of reddishbrown to yellowish brown sandy clays with the
clay content ranging up to 25%. Quartz, mostly in the coarse sand
fraction, was found throughout the profile but decreased with depth.
It was believed to have been mixed into the profile from the surface.
A question arises as to how much of the soil was derived from the under-
lying basalt. Augite was found in the sands throughout the profile
and appeared to be more resistant to weathering than the olivine and
plagioclase. The clays consisted principally of kaolinite, formed
from the feldspar, and hematite, a product of magnetite decomposition.

On the basaltic tuff consisting mainly of volcanic glass, parti-
ally altered to montmorillonite, and of lesser amounts of kaolin, oli-
vine, and highly weathered lapilli, it was found that the montmoril-
lonite was the first important weathering product regardless of drain-
age conditions. In the soils from the tuff there was evidence that
montmorillonite increased and goethite decreased with depth. This is
explained by the tendency of montmorillonite to break down tolaolinite
and goethite with depletion of the bases due to weathering and leach-
ing. The presence of kaolin in the underlying tuff is not commented
upon.

Somewhat similar to the results reported from Australia are those
from Africa. Ellis (18) studied a soil formed on an olivine-dolerite

sill in southern Rhodesia, under a climate with alternating wet and

*This material is probably iddingsite which Tiller failed to identify.

30
dry seasons and with an annual rainfall of 30 to 35 inches. The rock
was composed of augite, labradorite, olivine, iron ore, and biotite.
The iron ore, principally titano-magnetite, remained practically un-
weathered in the soil. The labradorite gave evidence of weathering to
kaolinite. Rounded concretions of sesquioxides were present from 5
to 9 feet although no information is given on their genesis or compo-
sition. Van der Merwe and Heystek (80) found montmorillonite to be
present in decomposing basaltic material in a soil in the temperate
region of south Africa. In the A horizon the clay consisted princi-
pally of kaolinite with some illite. In the deepest sampled horizon
of a soil formed from dolerite, kaolinite with some montmorillonite
was found to occur. No sample of decomposing dolerite was analyzed.
The silicate clay in the B horizon was entirely kaolinite. These
studies seem to indicate that montmorillonite is the first weathering
product but in time it is altered mainly to kaolinite.

McAleese and associates (47, 48, 49, 50, 51, 52) have made a
thorough study of the cation exchange properties and the clay mineralogy
of the soils derived from basaltic materials in northern Ireland. An
interesting feature of these soils is the increasing clay content with
depth in most of the soils, including those with poor drainage. The
exchange capacity of the total soil, varying between 30 and 57 me/lOO gm.,
was generally found to be lower in the B horizons (G in poorly drained
members) than in either the A or C horizons. Some of the better drained
soils are formed from basaltic glacial drift while the poorly drained

soils are overlying deep basaltic "boulder clay." The exchange capacities

31
of the clays were determined to be from 41 to 70 me/lOO gm. The ex-
change capacity of the silts (2 - 20 n) were shown to range from 14
to 59 me/100 gm. The capacity increased with depth consistently. The
fine sands (20—200 p) were found to have exchange capacities of 16.5
to 31 me/lOO gm. and the coarse sands (<.200 p) to have capacities
ranging from 11 to 19.5 me/lOO gm. There was an overall, but not
consistent, trend for the exchange capacity of the sands to increase
with depth.

MeAleese (50, 51) explains the interesting exchange capacity
property of the fine sands and silts by: (a) a small contribution
from clay minerals present in the size range of the silts and fine
sands as the result of aggregation and cementations by free sesqui-
oxides, and (b) a major contribution from the "pseudo-aggregates," which
have cation exchange capacities from 90-110 me/lOO gm. Pseudoaggre-
gates, evidently individual particles as indicated by their resistance
to dispersion after prolonged reduction treatment, were isolated from
the light fraction (< 2.85 sp. gr.) of the fine sands. No chlorites
could be detected in the X-ray analyses despite the fact that the aggre-
gates appeared chlorite—like under the microscOpe. McAleese is of the
firm opinion that the silt and sand particles showing these properties
are not merely undispersed aggregates of clay minerals but are indi-
vidual particles representing an intermediate stage in the weathering

of ferromagnesian minerals to the clay minerals, vermiculite or mont-

morillonite.

32

The pseudo-aggregates were determined to comprise more than 50%
of the light minerals in the lower horizons but to decrease with ascent
in the profile. Quartz was the predominant mineral in the surface
horizons, and it decreased with depth; the converse was true for plagio-
clase. Orthoclase was present in small amounts in two of the profiles.
Small quantities of zeolites were reported. Among the heavy minerals,
augite was found to be the most common in all horizons. The opaque
minerals, principally magnetite, with lesser amounts of hematite,
were reported as being very common. Hornblende and hypersthene were
found to increase slightly with depth. Traces of zircon and rutile
appeared in the heavy fraction of some horizons. The presence of such
minerals as quartz, orthoclase, hornblende, zircon, etc., is not ex-
plained but is presumably due to glacial contamination. In the studies
of McAleese, et al, no information is given regarding the mineralogical
nature of the primary material.

McAleese (49) found that kaolinite was the predominant clay mineral
in the surface soils. Vermiculite was found to be very common in the
well drained soils while montmorillonite was present in greatest amount
in the lower horizons of soils with impeded drainage. In most of the
soils illite was absent, or else, was a minor constituent. This was
explained by the fact that these soils formed from basaltic materials
which were low in potash. Quartz and feldspar, undetermined as to spe-
cies, were reported in many of the clays.

It is noteworthy that Mitchell and Irmak (53) report the cation

exchange capacity of the clay (<.1.2,n) of Turkish forest soils developed

 

 

011C

((1

131'.

not

33
on diabase and basalt as ranging from 105 to 113 me/lOO gm. The clay
(<.2 p) percentage ranged from 19 to as high as 43. It is unfortu-
nate that exchange capacity determinations on the silts and sands were
not made to see if they had capacities similar to those reported by
McAleese (50, 51). The soils were classed as Brown Earths and occurred
under a Mediterranean type climate. The clays from two profiles were
almost entirely montmorillonitic. However, those from another profile
were estimated as containing 75% mixed layer minerals. Some quartz
was present in one soil. Five percent lepidocrocite was recorded in
one sample.

In another investigation of the soils on the basalts of northern
Ireland, Smith (67) has given the weathering sequence of the primary
minerals in the basalt as olivine, labradorite, augite. The rock is
of Tertiary age but is believed to have been scoured by Quaternary
glaciers. The soil profile, overlying shattered basalt, is about 20
inches thick. An examination of a rock thin section showed some of the
augite crystals to be slightly altered to an olive-green product. The
olivine had altered along curved fractures to produce a yellow-brown
crystalline substance. (This description fits that of iddingsite so
commonly reported by others.) Secondary minerals, identified as vermi-
culite and kaolinite, were identified in the thin section. Sand sized
grains of olivine in the weathered crust of basalt fragments gave a
spacing of 14 3 units in an.X-ray pattern but could not be expanded
with glycerol. Since it collapsed with heating to 9.6 X it was inter-
preted as vermiculite. X-ray photographs of crushed weathered grains

of basalt showed that the ophitic labradorite laths had weathered to

34
kaolinite as shown by the presence of the 7.06 2 line and the absence
of the strong feldspar line of 3.19 8 units. Augite and magnetite
grains appeared relatively fresh in the crust. Most of the clay-
appearing material in the crust was amorphous to X-rays.

In the overlying soils augite and labradorite were found abundantly
in the sands and silts throughout the soil, whereas olivine was res-
tricted to the lowest horizon. Quartz was common in the sands and
silts and caused Smith to conclude that the 20 inch profile had devel-
Oped from a mantle of glacial drift of a dominantly basaltic composi-
tion instead of directly from the basalt. Aeolian contamination was
discounted because of the quartz being present in all size fractions.
The silicate clays of the soil were principally vermiculite with lesser
amounts of kaolinite. Extractable A1203 and Fe203 were high.

The weathering of basalts in tropical climates have long inter-
ested pedologists. Among such studies those conducted in Hawaii are
especially noteworthy; Hough and Byers (32) and Hough (33) have made
extensive chemical studies of the weathering products. Titanium was
reported to be the most soluble constituent of the parent basalt and
to show pronounced accumulation during soil formation (33). It was
likened to quartz in temperate regions in this tendency. In the ear-
lier study, it was found that dispersion was exceedingly difficult in
the silt size aggregates which were composed of clays, hematite, ilmenite,
and "related minerals." Magnetite and ilmenite appeared to be the most
resistant of the original minerals as indicated by their presence

throughout the soil. A.litt1e quartz was reported.

35

Tamura, et al, 06) has reported on the complex genetic relations
of the great soil groups and on the mineralogical composition of the
clays in some of the soils of Hawaii. Most of the soil was found to
be of clay size when thorough disperdon was effected. The mineralogy
of the clays is reported as being exceedingly complex. Of special
interest is the composition of the clays from the Hydrol Humic Latosols,
soils representing an advanced stage of mineral weathering in the most
humid areas of Hawaii. AllOphane, gibbsite, magnetite, and goethite
were found to be the main constituents, along with lesser quantities
of anatase, mica, hematite, quartz, and "free silica." It should be
pointed out that many of these minerals are reported on the basis of
an elemental analysis. For example, iron which was removed by reduc-
tion procedures was allocated to goethite and/or hematite while that
not so removed was allocated to magnetite. This latter procedure is
Open to question since the reports of magnetite in quantity in clays
are not numerous. However, there was some indication of magnetite in
the X-ray patterns, also. It is not clear how the percentages of ana-
tase and quartz, both rare in truly residual basaltic soils, are
derived. Another interesting feature of the report is the presence
of some interstratified layer silicates in one of the humic Latosols.

More recently Uehara and Sherman (78) have studied the altera-

tions of olivine" in the Hawaiian basalts on Oahu. They found that

 

I"The material called olivine may be dunite inclusions instead of
individual olivine phenocrysts.

36
olivine was altering to montmorillonite in the interior of the inclu-
sion but that the montmorillonite in turn was being converted to a
kaolinitic material near the outside of the inclusions. Differential
thermal techniques principally were employed in the study.

It is obvious from the varied results shown in the different works
cited that basalt can weather into several different products and give
rise to a variety of soils with diverse mineralogical composition.
Iontmorillonite and kaolinite are common silicate clays. lllite is
somewhat rare, as should be expected from the low K20 content of most
basalts. Hematite, goethite, and gibbsite are common products. Allo-
phane is not rare. Quartz is often reported, but rarely is its presence

satisfactorily explained.

Weathering of Volcanic Ash

 

It was not until this study was almost completed that it was
determined that some volcanic ash was present in the soils. This was
found during the course of the optical studies. Because of this late
finding the literature concerning the development of soil from ash,
with consequent mineralogical changes, has not been extensively re—
viewed. The results of Hay (29) and Hosking (31) concerning ash have
already been mentioned.

Bonnet (7) has reported on the deve10pment of a lateritic soil
from andesitic tuff in Puerto Rico. The unweathered ash was composed
principally of augite and andesine plagioclase. The quartz, abundant
through the profile is explained as being secondary since the original

tuff contained no quartz. According to Bonnet, the results do not

37
point to the leaching of free silica from the solum. The highest
concentration of silica and alumina was found to be in the C1 hori-
zon (10 feet) while the highest content of iron was in the C2 hori-

zon (20 feet).

Rios and Garcia (63) have made a study of the alteration of ande—
sitic ash beds in Spanish Morocco and have proposed theories regard-
ing the genesis of montmorillonite in these beds. They propose that the
montmorillonite is formed from andesine which begins with the hydra-
tion of basic cations in the crystalline net. This permits the loosen-
ing of the internal bonds which makes it possible to establish an equi-
librium between the crystal interior and the surrounding solution.

Ions from the crystal, principally calcium and silicate groups, then
may pass into solution while some ions from solution, principally mag-
nesium, are incorporated into the lattice at the same time. Evidently
these workers do not believe a complete breakdown is necessary to change
the three dimensional structure of feldspar into the layer structure

of montmorillonite. They do not eXplain how the proposed structural
rearrangement takes place.

In work done on New Zealand soils formed from volcanic ash Birrel
and Fields (6) found allophane to be the principal mineral in the clay
fraction. It is considered to be the factor mainly responsible for the
high exchange capacity (54 me/lOO gm.) and the characteristic physical
properties, i.e., high water holding capacity, high shrinkage, and ir-

reversible drying. The ash was of andesitic and rhyolitic composition.

38

In another study on New Zealand soils formed from volcanic ash
Gradwell and Birrell (23) found allophane, gibbsite, kaolinite, halloy—
site, and montmorillonite, and small amounts of iron oxides. The clay
content ((2 u) ranged up to 81 percent. In the soil with 8.1% clay
about 40% of the particles were less than 0.2 u in diameter. This is
especially interesting as this clay appears to be mainly kaolinitic,
as shown by cation exchange capacity of 15 me/lOO gm. and an internal
surface area of 33 mz/gm. for the whole soil. Usually kaolinite particles
are larger. The exchange capacity of another clay, described as being
made up mainly of a110phane and halloysite, was determined as 107 me/lOO gm.
No data are given concerning the mineralogical composition of the ash
or of the weathering changes which had taken place.

Kanno (41) working on Japanese volcanic ash soils has proposed
the following mineralogical sequence under intensive leaching condi-
tions: g1ass-~allophane--hydrated halloysite. It will be noted that
the position of allophane here, as an intermediate product,differs
from the place in the weathering sequence given it by most investigators.
Kanno also has found a correlation between soil colors and the ash com-
position as shown below:

(1) Ash containing olivine (basaltic)--Brown
soils

(2) Ash containing abundant acidic glass--
Light colored "ashy" soils

(3) Ash containing abundant hornblende (ande-
sitic)--Light yellowish brown soils

39
(4) Ash containing predominantly pyroxene
(andesitic)--Yellowish brown soils.

Sudo (73) has extensively studied the alteration of Quaternary
volcanic ash beds of Japan. In one such bed he found the dominant
minerals to be, in order, allophane, hydrated halloysite, kaolinite,
with descent in the deposit. Allophane was considered to be a material
on the way toward a final crystallized product. lixed layer minerals,
including random mixtures of halloysite and hydrated halloysite, were
reported, also. This material gave broad basal x-ray reflections and
in extreme cases the basal reflections were almost totally absent.

In some of the acid clays randomly mixed clays of a kaolinite-mont-
morillonite combination were reported. In tuffs older than Pleisto—
cene kaolinite was found to be the dominant silicate clay.

[any volcanic ash deposits are known which have given rise
to bentonite, a geologic material composed principally of montmoril-
lonite. Several such beds are found in the United States. It, there-
fore, is quite commonly taken for granted that volcanic ash gives rise
to montmorillonite. Undoubtedly this is often the case. In many other
cases montmorillonite may be one of the first products formed in the
devitrification of the glass, often a major component. The results
presented in the foregoing review indicate that many other minerals,
especially allophane, halloysite, and kaolinite are common alteration
products. There is nothing inherent in the physical nature of ash which

would restrict its weathering products to one or two minerals. The

 

40

resulting clay mineral suite is due to the mineralogical and chemical
makeup of the glass, climate, topography, especially as it influences
drainage conditions, and time. Vegetation, also, may be a factor

occasionally.

Natural Features of the Area Studied

Geology
In order to effectively study the genesis of the soils of North-
eastern New lexico, a rather thorough knowledge of the geology is
necessary. This is due to the complex geomorphic relations, the di-
verse stratigraphy, the chronological relations of the basalts and the

material overlying them.

Hill (30), an early worker in the area, briefly described some of
the geology including some of the lava flows and volcanic features.
However, it remained for Lee and Iertie (44) to make the first thorough
investigation in the area. They studied and mapped the Baton-Bdlliant-
Koehler Quadrangles, an area which is only partly included in the pre-
sent study. Sedimentary rocks exposed in the three quadrangles were
mapped as belonging to the Cretaceous, Tertiary, and Quaternary systems.

Parker (57) studied the origin and mineralization of the elastic
dikes and plugs in the Cimarron Valley in Union County with particular
emphasis on the stratigraphy and structure of the sedimentary rocks in
the area.

Collins (13) has published the results of an extensive study on

the petrology of the region. Collins lists a variety of sedimentary

41
rocks, including sandstone, shale, limestone, and unconsolidated sedi-
ments as well as giving the igneous petrology.

Striking features of the landscape are the numerous mesas capped
by basaltic flows and the volcanic cones which abound in the area (See
Fig. 1). .Also, intrusive rocks which form large complex masses occur
in the southern part of the region. In the western part of the area,
to the north and east of the town of Baton, there is about 2,000 feet
of relief between the surface of the high mesas and the surrounding
lowlands. Lee and Hertie conclude that these mesas are the erosional
remnants of formerly more extensive flows. They envisioned the flows
as being extensions of fissure type extrusions. They believed two
distinct series of flows to be present and dated both as early Pleis—
tocene (See Fig. 2A), principally on the basis of physiographic evi-
dence. Bartlett Hess and the west end of Johnson Mesa were classed
as being of the earlier stage. Later Griggs (24) gave the age of these
early flows as late Pliocene and the latter as Quaternary. In both of
the above publications the authors stated that the distinction could
be made on the basis of the alteration of the olivine phenocrysts. The
problem of olivine alteration will be discussed later in considerable
detail. However, Griggs realized the difficulty of distinguishing
these two groups of flows and mapped them as one unit. Collins grouped
the two series into one because of the uncertainty of distinguishing
them in certain portions of the area. He gave the age as Quaternary
although recognizing that they rested immediately over late Tertiary

gravels in some places. Collins includes both of these early series

42

mtmezjazg v cm W. Lo m.

mzoo mmozG s 3...: 2. 33m

 

 

 

 

 

 

 

 

 

    
   

 

 

:zmowm >4m<mom$ mBOJm hmmw230> Z 359.. 289;. 1...-lnll
.mzuooemfima >Jm<momav mgomu mc< m._.<_om2mm.rz_ . e z. n.
.mzwuoja PE... >4m<mom3 meson“. me040 .....c... .O 0 < m— o 21:.
_..!.J
I. u
3 _ :0qu . ,5 i
X . .zmozEam
w. .o o x < a o o
. 205.530 T»;
. jmsxasi 205.3... f
n 0
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7 .
v _
H“
0_
V "

  

. at!

Q Q Q Q Q .7 N Q U “Wade‘s
00.xw2 BMZ ZKMPM<MIPKOZ
mgoqm <><.._ 0_._.l_<m<m

H flmDOHh

OX‘sm MG 3%th

43

FIGURE 2
PHOTOGRAPHS OP LAVA FLOIS
North rims of Fisher's Peak Mesa (foreground) and Johnson Mesa

(background) Baton age flows.

Surface of Blosser Mesa. (Clayton age) with Johnson Mesa in
distanct background.

Edge of Barilla Mesa. Raton age. Relief is about 800 feet.

Edge of Blosser Mesa along encroaching canyon. Flow is about
75 feet thick.

\

Canyon working into the north rim of Johnson Mesa. Note type
of vegetation.

Surface of flow near Chico P. O. (Capulin age flow)

44

 

45

FIGURE 3
PHOTOGRAPHS 0F LAVA FLOWS
Edge of flow along stream bed. (Capulin flow). Note effect of

flow on stream development and type of vegetation.

Land surface over Clayton flows near Grenville. Dark line in
background is encroaching canyon.

Surface of flow near Folsom. (Capulin age). Note vegetation on
outcrops.

Tongues of Clayton flows (Center of photograph) to the west of
Capulin Mountain. Note volcanic structures in background.

Dacite cone and surface of Johnson Mesa. Photographed in late
March, 1958.

Tongues of Clayton flows to the southwest of Capulin Mountain.
Parts of same flows pictured in D.

 

 

47
in his "Baton" basalts (Figs. 2A, 20, 23, 3E, 4). This name will be
used henceforth in this study to designate the two older series of
flows. Levings (45) has recently made an outstanding study on the
erosinal and geomorphic history of the Raton Mesa group. He agrees
with the original analysis of Lee and Mertie that two distinct series
of flows are represented among these older flows but differs greatly
in the ages which he assigns. He envisions an age possibly as old
as Miocene and certainly no later than Pliocene for the earlier of the
two series. Although not stating so directly, it is believed that
Levings meant for the later series to be assigned to the Tertiary, also.

Wood, et a1 (84), in a recent mapping study of parts of Colfax
County recognized two separate series of the older flows but mapped
all of Johnson Mesa as belonging to the earlier series because of the
difficulty in accurately separating the two series. They followed the
lead of some of the preceding workers in assigning both series to the
Quaternary.

The lavas shown on the map as intermediate age flows are called the
"Clayton" basalts after Collins (13), Figs. 23, 20, as, 30, 3F, 5A.
There are a number of individual flows distinguished on the basis of
physiographic relations and petrology, but they are believed to consti-
tute a distinct chronological unit of outpourings. This series is the
most diverse petrologically of the four series. In addition to normal
basalts Stobbe (72) has described olivine free basalts, feldspathoid
basalts, basanites, and basalts with quartz inclusions in a petrographic

study of igneous rocks from the area. Most of the authors cited (13,

48

24, 44) have listed this undifferentiated series as intermediate in
age of the four (or three) series and have classed them as Pleistocene.

The Clayton basalts (of Collins) are the most extensive of the four
units discussed. The amount of relief exhibited by the mesas and table-
lands capped by the flows is variable. It appears to be determined by
the stratigraphy (the difference in the susceptibility of the various
exposed beds surrounding the flows), and the areal relations, as well
as the chronological relations of the flows themselves. Possibly the
susceptibility of the basalt to weathering may enter in, also; however,
this is not obvious from field observations. The elevation difference
between the lavas and the surrounding area most generally is between
100—500 feet. When occurring adjacent to each other the Clayton flows
can often be separated from the Raton flows with comparative ease
because of their topographic relations. Muehlberger (56) has recently
proposed that some of the Clayton basalts of Central Union County prob-
ably are close in age relationships to the late Raton basalts. He
thinks the age is very late Pliocene or earliest Pleistocene. This is
based to some extent on admittedly inconclusive paleomagnetic evidence
obtained in the field and reported earlier (55). The correlation of
some so-called Clayton basalts as being contemporaneous (second-period
of Lee and Mertie) with the late Raton flows is based primarily on
geomorphic and petrographic evidence. Muehlberger* has recently stated

that he believes the Pliocene-Pleistocene boundary to be somewhere about

 

*Written communication from Dr. Villiam R. Muehlberger, Geology
Department, University of Texas, Austin, Texas.

49

the middle, chronologically speaking, of the Clayton basalts. To

avoid confusion, the name, Clayton, is retained for all the basalts in
this study which Collins so named. Baldwin (3) working with Muehlberger
on a mapping study of Union County concurs with his age relationship
interpretations.

Most of the workers in the area have described the flows as being
of volcanic vent origin (13, 56). However, the source of much of the
material is not readily apparent from field observations. Baldwin (3)
describes the tongue of lava which underlies the town of Clayton as
being from 10~50 feet thick with a probable source in the volcanic
centers near Mt. Dora (See Fig. 1). It is believed that many of the
present tongues are a result of the basalt flowing down confining val-
leys which ended to the southeast. Baldwin also describes a tongue
shown by well logs which is overlain by about 40 feet of outwash gravel
and sand similar to the Ogallala (Pliocene) formation which underlies
much of the lava of Clayton age. This is shown on the map in Fig. 1.

Collins (13) reported that Quaternary loess had been added to the
decomposition products of the basalt on many of the lower mesas. This
is assumed to mean those of Clayton and younger ages. Baldwin and
Bushman (4) have stated that in some places the basalt of Clayton age
is covered by 20 feet of soil and caliche.

To the west of the towns of Springer and Wagon Mound (extreme
southwest part of map in Pig. 1), a group of basaltic tablelands are
found. The high level flows are believed by Griggs (24) to be contem-

poraneous with the early Raton flows. Those at lower levels are thought

50

to be Pleistocene in age and are roughly correlative with the Clayton
flows . Smith and Ray (68) consider the lower flows, as well as some
of the higher flows, thought by Griggs to be Pliocene, to be Pleisto—
cene. The general age and geomographic relationships of the flows

in this area has had little attention and no adequate maps of the area
are available.

The youngest series of flows are known as the "Capulin" flows
(13), Figs. 2?, 3A, 33, SB. They will be referred to as such in this
study. They are caned this because they are found extensively in the
vicinity of Mt. Capulin, Fig. 5A, a national monument which is probably
the best example of a little changed extinct volcano within the conti-
nental United States. Flows of Capulin age cover a much smaller area
than either the Raton or Clayton flows, Fig. 1. The Capulin flows
generally have been classed as Recent (3, 13, 24, 45, 54, 55). Muehl-
berger (54) gives a date of 2500-8000 B. C. as the age of these rocks.
This dating is based on the stratigraphic relations of a flow from Mt.
Capulin which is overlain and underlain by alluvium along the Dry
Cimmaron River. Radiocarbon datings have been made on materials con-
tained in the alluvium. Muehlberger (56) recognizes four distinct
flows of the Capulin sequence based on petrographic and geomorphic

evidence, with that from Mt. Capulin being the oldest in the series.

 

I"Written communication from Dr. J. Paul Pitzsimmons, Geology
Department, University of New Mexico, Albuquerque, New Mexico.

I""‘Iritten communication from William R. Muehlberger.

51

The Capulin flows occupy the lowest topographic positions in the
areas where they are found. For the most part they have flowed into
present day depressions and valleys including one tongue that flowed
down the Dry Cimmaron Canyon for 21 miles. Baby Capulin Mountain is
the source for this flow. The thickness of the Capulin flow varies
from 5 to 25 feet or more. The soil cover over most of these flows
is very thin. In fact, the basalt is exposed in many places where flow
ridges normal to the direction of flow are visible. Another interest-
ing type of exposure is present. These are "islands" of broken basalt
surrounded by fairly level areas which have some soil cover. This is
not a common occurrence on the Clayton or Baton flows.

There are some lithologic differences between the flows of various
ages; however, exact trends, if they exist, remain to be worked out.
Lee and Mertie (44) reported increasing fineness of texture and de-
creasing crystallinity with decreasing age of the flows, i.e., from
Baton to Capulin age. They also mentioned that olivine was generally
the only phenocryst in the Raton flows but that augite and plagio-
clase phenocrysts were found in increasing amounts in the Clayton
and Capulin flows. They also report an increasing degree of olivine
alteration to iddingsite with age. It is implied that it is a weather-
ing product of olivine. In general Muehlberger (56) has found that this
holds true with the exception of the Capulin basalts. He believes the
latter to belong to a new cycle or to be a regeneration of the original
magma type. The chemistry of the Capulin rocks is similar to that of

the early Baton flows, the principal differences are the formation of

 

52
local flows and cinder cones in the Capulin sequence in contrast to
the extensive early Baton sheet flows. Muehlberger also reports in-
creased development of feldspathoids in the Eaton and into the Clayton
flows. He relates that thin sections of the Raton flows show olivine
has almost completely been altered to iddingsite and that some altera—
tion has occurred in the Clayton and Capulin rocks, this usually con-
sisting of iddingsite rims around the olivine crystals. No statement
is made regarding the mode of this alteration. Stobbe (72) has re-
ported fewer and smaller olivines in the Capulin basalts. She also
reports iddingsite, and serpentine as alteration products of olivine,
in the Raton basalts. Iddingsite rimming olivine in the Clayton flows
and only a suggestion of iddingsite in the Capulin flows was found.

Among the other igneous rocks in the area dacite, hornblende
andesite, trachyte and phonolite has been reported by Collins (13)
and Stobbe (72). In addition Stobbe reported the presence of tingu-
aite and analcime microfayaites. Frequent dikes cutting the country
rock are found in the area. Their relations are exceedingly complex.
Lee and Mertie (44) described the alteration of some of the lampro-
phyric dikes of basaltic composition. The rock is now a greenish
appearing material composed principally of chloritic material, ser-
pentine, and calcite. It appears that the olivine has been altered
principally to serpentine. This appears to be the case with the olivine
in the intrusive rocks while that in theextrusive rocks has altered to

iddingsite.

53
Age relationships of the rocks described in the preceding para-
graph are in doubt. Griggs (24) states that the intrusive sill complex,
which he described as monzonitic, is post—Cretaceous and pre-Ogallala
in age. Collins (13) gives the age of the dacites of Toundrow Mountain
and Red Mountain which have intruded the Raton flow as being interme-

diate between Raton and Clayton age basalts.

Climate
The present climate of most of the area studied is classed as
warm semi-arid. However, the climate of the high mesas probably should
be classed as cool sub-humid.
The following table gives precipitation and temperature data
for selected locations in the area (27). Some of these locations are

shown in Fig. 2.

TABLE I

CLIMATIC DATA PROM STATIONS IN THE IIGION

 

 

 

Length
of Length
Ave. Annual Ave. Temperatures Growing of
Precipitation Jan. July Season Record
Clayton 15.79 34.3 74.2 177 31
Raton 15.94 30.3 69.1 146 40
Ft. Union* 18.34 32.2 68.8 141 20
Capulin 19.19 30.8 68.4 145 15
Lake Alice 20.18 141 30

 

*Ft. Union is the nearest climatological station to the sampling
site of Profile No. 4.

54

Of the stations listed the conditions at Lake Alice most closely
approximate those on the high mesas. However, the Lake Alice station
is probably from 1000-1500 feet lower in elevation than the sampling
site on Barilla Mesa and from 750-1200 feet lower than the site on John-
son Mesa. From this information it does not seem out of line to con-
clude that the annual precipitation is somewhere between 22 and 25
inches on the high mesas. Of course, the temperatures are considerably
lower, also. Light frosts may occur in any month of the year.*

Another notable feature of the climate is the high wind velocity.
Windstorms with velocities reaching as much as 60 miles per hour are
common in the late winter and spring. In addition many days occur through-
out the year when the average velocity is 20 miles per hour. The high
mesas are not subjected to more frequent severe windstorms but it is
believed from personal observation that the average wind velocity is
greater there than on the lower lying areas. Undoubtedly these high
wind velocities reduce the amount of effective precipitation and cause
some uneven distribution of snow drifting into potected places.

In making a study of weathering and soil genesis considerations
must be given to past climates which existed in the area as well as
the present climate. It is generally believed that the Pleistocene
in the Southwest was a time of alternating wet and dry periods. The

wet periods were probably appreciably wetter than the present day

climate.

 

I"Data supplied by Ralph G. Miller, Soil Conservation Service,
Raton, New Mexico.

55

This is in agreement with the opinion of Bretz and Horherg (10).
In addition they believe the Recent epoch to have been characterized
by four periods of alternating relatively humid and relatively arid
climates and that the present period is a relatively arid one. Their
opinion is based principally on a study of caliche formation in eastern
New Mexico. Antevs (1) divides the Postpluvial period in the South-
west (which started somewhat earlier than the Post—glacial) into three
periods with the middle period (5500-2000 B.C.) being the warmest.

The following material from Judson (40) is pertinent.

During the Pleistocene southwestern United States under—

went more or less rhythmic fluctuations of climate which varied

from extreme aridity to a climate moister and probably somewhat

cooler than that of the present . . . . Evidence, however, mar-

shalled by numerous workers points to a correlation between the

climate of the Southwest and the glaciations and deglaciations

of Canada, northern United States, and the western mountains.

With the advance of ice in the north and in the higher moun-

tains the arid and semi-arid zones were displaced southward

and supplanted by moister and somewhat cooler climates . . . .

Winters were more rigorous, and summers cooler. Conversely,
temperatures increased, and effective rainfall decreased with

periods of deglaciation.

Evans (19) assigns an age of early Pleistocene to the Blanco
formation of west Texas on the basis of faunal evidence. The beds
consist of an almost unbroken sequence of lacustrine deposits. These
were deposited in lakes which were ponded in the underlying Ogallala
(Pliocene) formation. This reflects a sustained period of a moist
climatic condition. Overlying the lacustrine deposits are deposits of

loess-like dust, unaltered volcanic dust, and surface soil which reflect

a return of arid conditions.

 

FIELD STUDIES

Vegetation

 

The vegetation of the relatively level surfaces of the high mesas
is composed mainly of herbaceous plants, especially grasses (See
Figs. 38 and 3C). Among the grasses western wheatgrass, Agropyron
smithii, and various grammas, Bouteloua spp., are especially common.

Sedges, Cyperaceae, are found over most of the area. Boraginaceae

 

appears to be well represented, also; at least, in the early summer when
the field studies were made. The steep slopes surrounding the high
mesas support an entirely different flora (See Figs. 3A and 3E). Here

pine, Pinus ponderosa and P. edulis, spruce, Picea pungens, some fir

 

Abies spp., aspen, Populus tremuloides, juniper, Juniperus spp., oak,

Quercus spp., and many shrubby species as well. In places around the

 

heads of canyons where the slope is somewhat greater and near the edges
of the mesas the woody species have encroached upon the basaltic table-
land (See Figs. 2 and 4D). It appears that the woody species cannot
compete effectively with the herbaceous species where the surface is
level and the soil is deep.

On the flows of Clayton age the grasses are by far the most common
plants. The grammas, Bouteloua spp., are the dominant plants. Buffalo

grass, Buchloe daytyloides, is a common species. Three-awns, Aristida

 

£22., are found, especially in disturbed areas. Woody species are

confined to the broken areas around the edges of the flows, ravines,

57

and other basalt outcrop areas. Pinyon pine and juniper occur most
commonly. Occasionally some ponderosa pine appears. A few plants
which belong to Cactaceae along with some yucca, XEEE§.§EE°' are found.
However, it might be pointed out that these latter plants are less
common on the soil overlying the basalt than on surrounding soils.

The vegetation on the Capulin flows differs from that on the Clay—
ton flows in one principal aspect. Where the islands of broken up
basalt are exposed to the surface juniper, pinyon, oak shrubs, Quercus
spp., and other shrubs occur (Figure 2F, 3A, 3C, 5). Also, some of
the tall bluestem grasses, Andropogon E223, abound on such "islands."
This is interesting in view of the fact that the normal range of the

Andropogons is in a considerably wetter climate than obtains here.

 

Species of Bouteloua, Buchloe, and Aristida are the grasses most com-

 

monly found on the areas which have some soil cover.

In summary, it may be said that vegetation has had little in—
fluence on the type of soil developed in this study since only grass-
land areas were sampled. In the area it seems rather that vegetation

has been determined by climate, topography, age, and soil, including

the underlying rock.

Sampling Procedures

Considerable time was spent in the field becoming familiar with
the geology and the topographic relations of the various lava flows.
Since no soils maps were available it was necessary to have a good

overall knowledge of these relations in order to select suitable

sampling sites.

 

58

Sites were avoided where obvious contamination from surrounding
country rock had taken place. Likewise, those sites were avoided
where the underlying flow did not appear to approximate the "normal"
basalt of the area. .Also, only those sites were sampled with a slope
varying from 1% to 3%. In this way it was hoped to select profiles
with good, but not excessive, drainage, and at the same time those
which had not been subjected to appreciable water erosion nor to have
received alluvium.

Six profiles were sampled. The sites of these are marked on
Fig. 1.

Dr. David Bartlett of the Soil Conservation Service, Clayton,
New Hexico, believes that Profile 3 is a member of the Capulin series
and that Profile 6 is probably a member of the Apache series.

According to Mr. Ralph G. Hiller of the Soil Conservation Ser-
vice, Raton, New Hexico, the soil on Barilla Mesa, Profile 1, is
classed as the Barilla series and that on Jehnson Mesa, Profile 2,

as a member of the JOhnson series.

Mr. Arthur G. Sherrel of the Soil Conservation Service, Springer,

New Mexico, is of the opinion that Profile 4 is a member of the Capulin

series, also.

It should be emphasized that none of these areas have been mapped

in detail.
It was deemed worthwhile to sample Profile 4 although it was some-
what removed from the area under investigation in order to determine

the variation in mineralogy with areal spread. Complete laboratory

59

FIGURE 4

SOILS ON BARILLA AND JOHNSON IESAS

Profile 1. Note large basalt fragment at about
26 inches.

Profile 2. Color is unnaturally tinted purplish.

Weathering basalt and overlying soil on west end
of Jehnson Mesa. Upper part of profile has been
removed during road construction.

Basalt and soil in bottom and along side of borrow
pit near east end of Jehnson Mesa. Note dark color
of soil and Ponderosa pine in background.

 

 

 

61

FIGURE 5

FEATURES OF LAVA FLOWS

A. Picture shows scarp edge of one of the Clayton

flows. Cinder cone in background is Capulin

Mountain.

Surface of a Capulin age flow along Dry Cimmaron

River. Note overturned boulders which are cali-

che encrusted.

 

62

63

studies were made on Profiles 1, 3, 4, and 6; some studies were made

obtained on Profile 5. It is

on Profile 2. No laboratory data were

included in the descriptions because it is believed to show deposi—

tional influences observablein the field.

The profiles were sampled by digging pits large enough for a

be the characteristics exposed in the

person to observe and descri

vertical faces of the pit.

file 1 and Figure 4B shows the sampling pit of

Figure 4A shows Pro

Profile 2. Figure 4C shows a weathering basalt boulder on a road cut

on the west end of Johnson Mesa. The upper part of the profile had

Much of the rock can be

been removed during the road construction.

crumbled by hand. Figure 4D shows the weathering basalt on the east

end of Johnson Mesa. This is at the edge of a borrow pit and the

slumped down over the rest of the

dark soil from the A horizon has

profile, hence, the dark color. The relation and depth (3-4 feet)
of the overlying soil to the weathering basalt is well portrayed here.
Much of this material is

The pit is floored with weathered basalt.

weathered to the point where it is quite soft. The vegetation aspect
shown in Figure 4D is worthy of note. This site is about 200 yards
from the edge of the mesa and is gently sloping. There are no woody

en where the terrain is somewhat

plants in the interior of the mesa ev

e development), but trees have en-

broken (because of beginning ravin

croached onto the top of the mesa from the edges for some distance.

The terminology used in describing these soils is chiefly that

outlined in the Soil Survey Ianual (79). The genetic designations

64
in parentheses are those recently proposed by Whiteside (82). Des-

criptions of the six profiles studied follow.

65

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LABORATORY PROCEDURES

Mechanical Analyses and Size Fractionations

 

Basically the method described by Kilmer and Alexander (42) was
used in making the mechanical analyses. However, since an iron oxide
removal treatment was added and fractionation for mineralogical analysis
was combined with the mechanical analysis the detailed procedure is
outlined below.

1. Organic Matter Removal. Between 10 and 12 gms. of air dry
soil was used and an approximate 10 percent H202 solution added. After
a considerable portion of the organic matter was destroyed 30 percent
3102 was added and the mixture was digested on the hot plate and this
process repeated until the sample appeared to be practically free from
organic matter.

2. Free Iron Oxide Removal. Essentially the method of Deb (15)
with modifications by Kilmer* was used. Four gms. of sodium hyposul-
fite (hydrosulfite) (Na28204 ' 2H20) were added, the volume diluted
to approximately 50 m1., and the mixture shaken for at least six hours.
N328204 - 2H20 is a strong reducing agent and effectively reduces the
iron to the soluble ferrous state in which it can be washed from the
system.

3. Adjustment of pH using HCl. The pH was lowered to 4.5 using

1.0 N HCl. (In some cases this was unnecessary since the pH was already

below this point after the iron reduction treatment.) In some other

 

b—O—

*Vritten communication from V. J. Killer, U.S.D.A., Beltsville, Id.

72
samples several hours were required before all the CaCO3 was destroyed
and the pH would remain at the desired level.

4. Filtering. The suspensions were then filtered and washed with
distilled H20 using suction until the filtrate was free of chlorides.
(A lead acetate paper test for sulfides was made on some of the samples
when all chlorides were removed. Since all tests were negative it was
assumed that all of the sulfides were removed by the time the chlorides
were and the test was discontinued on the succeeding samples.) Great
difficulty was encountered in filtering many of the samples. When
filtering was first begun, some fine clay would go through the hardened
filter paper (No. 50). Then as most of the large pores of the paper
would become clogged, the filtrate would become clear. Also, as wash-
ing progressed, the clays would become dispersed and since the clays
were composed of expanding materials in varying degrees, this added
to the difficulty of filtering. In some cases as much as twenty-four
hours were required to filter and wash the samples.

Centrifugation was tried in order to solve the filtering problem.
However, the practice did not seem advisable since dispersal occurred
before the suspension could be washed free of chlorides and filtering
would still have to be resorted to for the final washings.

5. Adjustment of pH using NaOH. The material was removed from

the filter paper, 50 ml. of H20 added, and the suspensions adjusted

to pH 9.5 with 0.1 N NaOH (the dispersing agent). At this level there

appeared to be excellent dispersion. The suspensions were then shaken

for at least twelve hours.

73

6. Separation of Sands From Silt and Clay. After shaking the sam«
ples were carefully washed through a SOD-mesh sieve. A special effort
was made to avoid leaving particles on the screen which had diameters
small enough to go through.

The sands (and coarse silt between 0.047 and 0.050 mm.) were then
oven dried and weighed.

7. Pipette Analysis. The material passing through the sieve was
transferred to a sedimentation cylinder. The suspension was brought
to a volume of 1 liter and placed in the constant temperature bath.

After allowing sufficient time for the suspensions to attain the
temperature of the bath pipetting was begun. One pipetting was made
immediately following a vigorous stirring with a hand stirrer. This
was used to calculate the total silts and clays in the suspension.
This was done at the 10 cm. depth as were all succeeding pipettings.

Pipettings were made for the 20, 5, and 2,p particles at the
apprOpriate time according to calculations made using Stoke's law.

The 25 ml. aliquot of suspension was emptied into a weighing bottle,

one washing with distilled H O was made and this emptied into the

2
weighing bottle, and then this suspension was dried overnight in an
oven at 105°. After this procedure, the pipette was washed with ace-
tone to facilitate drying and thereby not affect the volume of the next
sample.

8 Determination of Total Sand, Silt, and Clay. Each fraction was

calculated as a percent of the total obtained by adding the amount of

sand to the total silt and clay obtained by the first pipetting. These

74

are thus expressed on an organic matter free, carbonate free, and
iron oxide free basis and given in Table II. It was necessary to
remove organic matter, CaCOa, and free Fe203 to effect thorough dis-
persion and to clean the grains for a mineralogical study of the
various fractions.

9. Sand Fractionation. Before the sands were sieved into size
fractions, a density separation at specific gravity 2.9 was made using
a symmetrical tetrabromoethane. This procedure is described later.
Since the total sand content of many of the samples was quite low,
it was feared that the heavy mineral fraction of any one separate might
be too small to work with; consequently, the density separation was
made before sieving. After sieving, it could be seen that the very
fine sand fraction would have been adequate on which to have made the
density separation. The light sand fractions were separated into only
three size fractions since most of the sand was the fine sand and very
fine sand fractions. These results are given in Table II.

10. Separation of Pine Silt (2-5 m), Coarse Silt (5-50 p), and
Clay by Sedimentation. .After the pipettings were completed, fractiona-
tion procedures were begun on the silts and clays. It was decided
to separate the silts at the 5 u level principally to determine the
types, if present, of layer silicates in the 2-5 m fraction.

Fractionation of the two silt sizes and the total clay was made
using a glass siphon with a 1800 book in the glass at the inlet end;
consequently, the Opening pointed upward and was about 1 cm. above the

lowest part of the bend. This was done in order to decrease the dis-

turbance of the sedimented portion when siphoning. After the initial

75
siphoning, the material was usually diluted to a volume which was
either 10 or 15 cm. above the siphoning depth. In this way the volume
of liquid was kept low. lAll calculations of settling velocity were
made using Stoke's law. It was found while working with the first
set of samples that five siphonings were sufficient to remove all
but negligible amounts of a particular size fraction.

11. Fractionation of Clays by Centrifugation. Since it was
thought probable that significant mineralogical differences would show
up between the coarse and fine clay fractions, it was decided to make
a separation at 0.2 p equivalent diameter. This was done using the
centrifuge head with trunion fittings. Essentially the procedure
described by Jackson (38) was employed to make this separation.

Stoke's law may be applied to the velocity of fall of particles

during centrifugation according to the following equation:

17 log ._._
Bl

 

3.81 Nzrz (up - d1)
where: t = time
R1 - distance from center of centrifuge head to top of the liquid
R2 = distance from center of head to given depth in the liquid

N = revolutions per second

’1
ll

radius of particles
dp - density of particles

d1 = density of the liquid

3
I

viscosity

*Tor derivation of the eguation, see Baver, L. 0., 8011 Physics,
1956. Third Edition, pp. 59-6 . John Wiley and Sons, Inc., New York.

76

The density of the clays used was 2.5.

It was possible to decant the material still in suspension at the
end of the centrifugation period off of the material which was thrown
down without apparent disturbance._ After decantation the material

left in the tube was diluted and stirred thoroughly by using a plunger
k

made from a whittled rubber stopper fitted on a glass rod. Usually

four centrifugations were made before the supernatent liquid was suf-

ficiently free of fine clay.
12. Evaporation. After the fractionation was complete, the coarse

silts (5-47 p) were dried and put in vials. The fine silts (255 n)

and both clay fractions were reduced in volume by using low heat (an
infra—red bulb) for evaporation and put in flasks for mineralogical

analysis. Care was taken not to dry any of the clays or fine silts

because of possible irreversible collapse of expanding lattice minerals

or irreversible dehydrations.

Density Separations

A density separation at specific gravity 2.9 was made of the sands

and coarse silts using tetrabromoethane. The method has been des-

cribed by Bourne*. Briefly it is given below with a few modifications.

{A small quantity of the reagent was put into a small conical plastic

centrifuge tube containing the sediment. The mixture was centrifuged

using a small hand centrifuge until there was a distinct separation

 

*Iritten communication from W. C. Bourne, Mentana State College,

Bozeman, lbntana.

77

between the light and heavy fractions. Usually this required about a

minute. Then the tubes were placed in dry ice into which a small hole

had been reamed. The reagent would then freeze in the tube up to the

surface of the dry ice. The unfrozen portion containing the light

fraction was then poured onto filters and the upper portion rinsed
thoroughly with acetone and the rinse added to the filter. It was
necessary for the operator to work rapidly to complete the rinsing
before the frozen bromoethane in the bottom of the tube melted. As
the frozen portion melted away from the sides of the tube, it was emptied
onto a filter and the tube rinsed with acetone. This completed the
separation.

It was decided that an additional density separation at the 3.35-
3.40 level using thallous formate, ThHCOz, would be desirable. The
use of this chemical is discussed by Krumbein and Pettijohn (43).
This would separate the minerals, augite and magnetite, two important
components of the basalts, and would facilitate the counting of the
heavy minerals. The salt could not be obtained commercially and was

prepared by dissolving technical grade thallous carbonate, Th2C03*,

in formic acid, evaporation to remove excess formic acid and water,

and crystallization by cooling to room temperature. Since thallous

formate, ThHCOz, is very soluble in water, it was necessary to add
water dropwise until the desired density was reached. The density

adjustment was done using the minerals dumortierite and tepaz, for

*Obtained from Fielding Chemical Company, Jersey City, New Jersey.

78

which the densities were known, by the "sink or float" method. It
was necessary to adjust the density of the liquid each time before
using and to work at a room temperature of at least 25° C. (The solu-
bility of ThHCOZ decreases markedly with decreased temperature.) The
same procedure, including the use of dry ice to freeze the portion
of the liquid containing the heavier particles after centrifugation,
as described previously, was used. However, distilled H20, instead of
acetone was used for rinsing.

There are several obvious inherent difficulties involved in
using ThHCOz for density separations. However, it can be used effect-
ively to save time if there are a number of samples to be analyzed.

The use of the procedures described above resulted in the fol-
lowing density fractions: (2.90, 2.90-app. 3.4” )app. 3.4. The terms,
"light," "heavy," and "very heavy," respectively, will be used in the
succeeding discussion to describe these fractions.

The relative percentages of the heavy and very heavy fractions

are given in Table III. It must be remembered that these percentages

are only approximate.
Bulk Density Measurements

Bulk density measurements were madeusing the oven dry weights of
core samples taken from selected horizons in the profiles as indicated
in Table II. The values given are the means of four replicates. The
taking and preparation of cores, especially in the lower horizons, of

profiles 3 and 4 were exceedingly difficult because of the dryness

79

and the dense blocky structures exhibited. Too much significance should

not be given to these values because of this problem.
Organic latter Determination

Organic matter determinations were made on the uppermost horizons

of profiles 1, 4, and 6 and the A41 horizon of profile 3 using the wet

combustion method given by Prince (58). The A12 horizon of profile 3

was selected instead of the All horizon since the latter was a very

thin horizon with a high concentration of grass roots. In this regard
it should be mentioned that the bulk samples for the other surface

horizons were taken at depths greater than two inches to get away from

the high concentration of grass roots. The results are shown in Table

VII.

Organic matter determinations were made principally to test the

effects of climate and/or age on such accumulations.
pH Keasurements

Twenty gms. of soil in 50 ml. water was used as the mixture for

pH determination. A Beckman Zeromatic pH meter was used. The results

are listed in Table VII.

Cation Exchange Capacity

The cation exchange capacity of the horizons was determined using

ammonium acetate as the replacing solution in the method described in

the U.S.D.A. Agriculture Handbook No. 60 (62). Four gms. of soil,

80

corrected for moisture content, were used in the determinations.

The results are shown in Table VII. Only one or two gm. samples were
used on the determination of the exchange capacity of the silt fractions.
Furthermore, no correction was made for moisture content. The small
amounts of silt available necessitated these modifications. The re-

sults are given in Table VII.

Surface Area Measurements

The method of Bower and Gschwend (8) using the retention of
ethylene glycol as a measure of total surface area and internal sur-

face was employed. The results are listed in Table VII.
Total Potassium in Clay Fractions

The modified procedure of Webber and Shivas (81) was used in the
determination of potassium contents. A total of 0.5 gms. of air dry
clay was weighed into a platinum crucible and this dried in an oven
at 105° c. After weighing 1 m1. of 1:5 H2804 was added and the mix-
ture stirred with a platinum wire. Five m1. of concentrated HF was
added and the solution evaporated to dryness. The residue was re-
moved by immersing the crucible in a 1:20 solution of HNO3. After
heating almost to boiling the crucible was removed and rinsed. The
solution was then evaporated to dryness and the residue taken up with
0.1 N HCl. Filtering was unnecessary.

Standard solutions of 5, 10, 20, 30, and 40 ppm potassium in 0.1 N
301 were prepared. The potassium content of the extracts and standards
were determined using the flame photometer. The results are given in

Table VII.

 

81

x-Ray Diffraction Procedures

Clays. The methods currently used in the Soil Science Depart—

 

ment at Michigan State University for determination of clay minerals
were employed. The methods consist of the following steps. To an
aliquot of suspension containing approximately 40 mgms. of clay, 10
draps of a 3% glycerol and 0.1 N CaC12 solution is added to eXpand the
swelling clays. The suspension is then poured into a well over a
porous ceramic plate mounted over a suction flask. The suction aids
in effectively orienting the clay particles parallel to their 001*
planes and removing the liquid.

After orientation the plates are dried over Ca012 and then X-rayed
using Culflradiation and scanned between 2 and 310 2 9. A slit system
of i0, 0.003 ins. and 3° was used in these determinations.

The plates are then leached with three increments of N KCl, fol-
lowed by several increments of distilled H20, dried over CaC12, and
then heated at 105° C. for two hours. The plate is scanned again
over the same angular range. This treatment causes collapse of the
swelling clays and effectively converts them to structures with 001
spacings (6001 = 10 3) similar to the micas. Chlorite will retain
an 002 spacing of app 14 X.

The plate is then heated to 550° C. for two hours and scanned

again over the same angular range. This last treatment removes the

*The conventions employed by Bragg and Bragg (9) to denote the
h k 1 indices will be used here when discussing the X-ray and optical
work and in discussing the crystallographic properties of the minerals.
The indices of a face will be put in brackets (h k l) and the indices
of a reflection will be given as h k 1 without brackets.

 

_ ——-—-———-———_ - 'ufiL-m — ‘7' W- “-
__

24

soils. The soils studied are found under variable climates. The Red
Loam soils, with an annual rainfall of 69 to 43 inches and mean annual
temperatures of 66° to 52° 1., contain principally kaolinite with asso—
ciated hydragillite, goethite, and hematite as shown by X-ray analyses.
The Red Brown Earth, occurring under a climate of 23.4 inches annual
rainfa11_and 63° F. mean annual temperature were found to contain
dominantly montmorillonite together with some quartz. The same was
true for a Chestnut Earth found in an area with 14.8 inches rainfall
and an annual temperature of 63° F. In the Black Earths with moderate
rainfall (26.3 to 31.3 inches per year) and temperatures ranging from
56° to 71° F. montmorillonite appeared to be the only crystalline com-
ponent present. It is believed by Hosking that internal moisture condi-
tions play an important role in determining the kind of clay mineral
formed. Where the soil is subjected to droughts each year or where
internal drainage is impeded montmorillonitic clays are developed. In
soils where the moisture is excessive and leaching conditions prevail,
kaolinite, with associated iron oxide minerals, predominate. It should
be mentioned that in every soil the clay fraction constituted more than
50% of the mineral solids.

Hosking also studied the 2 p fractions of relatively fresh volcanic
ash and a soil formed from similar material from New Guinea. Tropical
weathering conditions obtained. In the ash a 15 X and a 742 line were
present indicating both montmorillonite and kaolinite where present;

whereas, in the soil only the 7 2 line was present.

82
kaolinite peak since the kaolinite lattice is generally destroyed

by the loss of structural 0H ions at a slightly lower temperature.
This series of treatments will generally detect the presence of
the silicate clay minerals, montmorillonite, vermiculite, chlorite,
illite, and kaolinite, as well as mixed lattice clays.
Preliminary studies of the total clay fraction from the 82 horin
zon of Profile 1 gave poor 001 reflections so it was decided to remove
Deb's method as modified by Kilmer and previously

the free iron oxide.

described was used. In addition, the method of iron removal reported

by Aguilera and Jackson (2), which incorporates the use of cheleting

agents along with sodium hyposulfite was tested for possible increased

resolution of the diflraction patterns of the clay. No improvement

over the untreated samples could be seen so this method was not used
It was decided to use Kilmer's method for iron oxide removal

further.

as a standard pretreatment for all the soils before making mechanical
analyses and subsequent fractionations.

It was thought that treatments with the strong hydrogen peroxide
solution to rid the clay of organic matter might be partially destroying
the clay mineral lattices. Patterns were run on clays not subjected
to H202 treatment and once again no improvement in resolution could
be obtained.

It was then decided to treat the suspensions with more highly

concentrated solutions of glycerol and to subject them to longer periods

of glyceration before orienting them. Once again no significant changes

could be detected.

84

After most of the clay fractions were mounted and scanned, it
was suggested that a solution of beta-napthalamine hydrochloride
(CIOH7NHZHC1) be used to expand the clays. This was tried on both
a coarse and fine clay (the fine clay shattered upon drying following
the K saturation). No marked improvement in obtaining longer spac-
ings could be seen so the use of the chemical was discontinued.

The diffraction patterns obtained by the standard treatments

herein described are shown in Figs. 9, 10, 11, and 12.

Ellis. It was decided to check the fine silt (2-5 a) samples
for possible content of silicate layer minerals since some investi-
gators (65) have reported a notable content of these minerals, especi-
ally kaolinite, in this fraction. These were plated out in the same
manner described previously for clays. The results are shown in
Figs. 12 and 14, lower right. Only very small quantities of layer
lattice silicates are indicated in these patterns so the orientation
of the fine silts on plates was discontinued.
Powder diffraction patterns were obtained on some of the fine
silts by using the spinner mechanism. These are shown in Fig. 14.
In addition powder diffraction patterns were run on some coarse
silt (5-50 u)samples. Fig. 14 also shows these results. The lack
of sufficient amounts of both the coarse and fine silts of many hori—
zons precluded their being used in the spinner to obtain powder patterns.
When the spinner was used a slit system of 1°, .003 ins., i0 was

employed.

85

After learning that some of the coarser fractions in some of the
soils had some exchange capacity it was decided to check these (where
enough of the unused fraction remained) for the presence of layer

silicates by using the common 110 and/or 020 planes. Fig. 14 shows

these patterns.
At the same time some patterns were obtained on some of the

weathered basalts to determine if layer lattice silicates were being

formed from the primary minerals. Fig. 14 shows these patterns.

Differential Thermal Analyses

Differential thermal analyses were done on most of the clay
samples using equipment built by Kr. R. L. Stone of Austin, Texas.
Analyses would have been run on some additional samples if sufficient

quantities of clay had remained after doing X-ray analyses and deter-

mining K20 content. Results of the available DTA analyses are shown

in Fig. 13.

Mineralogical Studies of Sand and Coarse Silts

.As stated previously the entire sand portion was separated into
three density fractions since it was feared that there was not enough
of the very fine sand to give adequate quantities of heavy minerals for
detailed study. Slides were prepared by mounting a portion of the

fraction to be studied on gelatin coated slides.* These, as well as

 

*The slides were obtained from the Eastman Kodak.Company, Rochester,
New York.

86
the thin section studies, were made using a Leitz research model polariz-
ing microscope, Ibdel Kl—POL. By using this method it was possible to
prepare semipermanent mounts and determine the refraction index, by
comparison with oils, of a specific grain. A word of caution on this
point seems to be in order. The observer must use the utmost care not
to immerse the grains in the gelatin solution on the slide when mount-
ing. Even with care it is sometimes quite difficult to determine the
refractive index of some grains because of the interference of the gela-
tin.

After the slides were prepared considerable time was spent studying

the various suites of minerals. It was felt that this was essential
in order to do an adequate job of counting. In the words of Jeffries
and Jackson (39) regarding the mineralogical examination of sands and
silts, "Knowledge of the theory and continued practice are essential
for optical identification of crystalline materials. This cannot be
overemphasized." Counting was done on approximately 300 grains of the
very heavy, 200 grains of the heavy, and 100 grains of the light frac-
tions. It was felt that it was necessary to count a greater number of
the grains in the very heavy fraction to get a true representation of
those present since this fraction was dominated by magnetite. It is
admitted that more than 100 grains of the light fraction should have
been counted but minerals in this fraction, quartz, potassium feld-
spars (especially orthoclase), and plagioclase feldspars could only
be separated accurately by determing their Optical preperties, including

refractive indexes, of each grain. It was found that separation on

 

87
the basis of albite twinning in the plagioclases in which the twin-
ning plane and composition face is the (010) plane, was not entirely
satisfactory, even though it is reported as generally having the
(001) cleavage best developed. It was found that interference figures
were very often necessary to distinguish the quartz from much of the
plagioclase. Because of the time consuming nature of such work only
approximately 100 grains were counted.

In the very heavy fraction the metallic luster under reflected
light and octahedral habit of the magnetite were the criteria used
in differentiating it from the other Opaques. The determination of
optic sign, size of 2V, pleochroic formula, the estimation of bire-
fringence, and other optical determinations were often necessary in
order to correctly identify the mineral grain in question. It should
be emphasized that the accurate determination of Optical properties
of mineral grains, although possible, is considerably more difficult
than thin section work. The results of the mineral grain studies

are shown in Tables IV, V, and VI.

Thin Section Studies

 

Thin sections were made of the basalt underlying each of the soils.
Where possible, additional thin sections were made when obvious dif-
ferences in degree of weathering existed. Also, a few sections were
made of indurated peds in the solum. An examination of the pad thin
sections were made principally from a mineralogical viewpoint. In
addition one other thin section was studied which was cut from a sur-

face exposure of basalt showing caliche encrustation. This was taken

'-' 88
just outside the village of Grenville. The thin sections were prepared
by the Cal-Brea Corporation of Brea, California. Photographs of repre-
sentative portions of the thin sections studied are shown as Figs.

6, 7, and 8.

DISCUSSION OF FIELD STUDIES

[any field observations have already been mentioned in the sections
concerning the geology and vegetation of the region and the field

studies.

Profile 1

In the field Profile 1, which overlies Raton basalt, appeared to
be exclusively a product of basalt weathering. On many slopes the
basalt is exposed. Commonly boulders are found on nearly level surfaces.
These appear to be more resistant weathering remnants. Fragments of
weathered basalt were found in the solum. The light gray basalt at
the bottom of the profile was highly weathered and could be crushed
easily by hand. Only on the underside of some of the weathered frag—
ments was there any lime (CaC03) deposition. In fact this feature was
missed in the field. It was in a laboratory inspection of the frag-
ments that the coating was discovered. In the 82 and B3 horizons
some soft manganese segregations were present. These were beginning
to form in the Cl horizon, in many cases very near to the surfaces of
the weathering basalt fragments. This is believed to indicate slightly
restricted drainage.

Profile development was pronounced both from the standpoint of
texture and structure. Differences in color were not marked except
between the A and B horizons. The rather acid reaction of all the

horizons should be noted. There was no evidence of an A2 horizon.

90
Because of the climate it was thought some evidence of an A2 might be
present.
It should be kept in mind that the climate at this site is cold.
It is also quite moist, an estimated 25 inches annually, when compared
to the surrounding area. The elevation is approximately 8,500 feet.

The soil can be classed as a Brunizem.

Profile 2

This profile has probably developed under quite similar conditions
to those for Profile 1. It is also formed on the older flows. Because
of a little lower elevation, approximately 8,000 feet, the climate is
a little drier and warmer. This was indicated by some of the profile
characteristics. There appeared to be somewhat redder hues in this
profile as compared to Profile 1. Possible differences in primary
material cannot be discounted, though. The pH throughout the profile
was higher than in Profile 1. The reaction was distinctly basic in
the lower horizons.

One of the outstanding features of this profile was the presence
of many small spherical concretions of a manganese containing material.
These were found throughout the solum but were considerably more in-
durated and more numerous in the B horizon. These probably indicate
impeded drainage. The manganese concretions were more striking in

this trofile than in any of the others sampled.

91

Although basalt pebbles were found in the solum the transition
from the soil to the underlying rock was quite abrupt. Many of the
pieces of weathered basalt in the Cca horizon had thin coatings of
lime. The abruptness of this transition may be an indication of depo-
sition of transported material over the basalt. There is a dacite
cone about three miles to the east. The cone is not composed of
Cinders, however, but is made up of disintegrating dacite blocks.

Many of the pieces of weathered basalt in the Cl horizon have
thin coatings of lime. It should be understood, though, that there

is no distinct caliche horizon. This soil appears to have most of

the features of a Brunizem with some chernozemic properties.
Profile 3

This profile occurs in an area with a distinctly warmer and
drier climate than that prevailing at the sites of Profiles 1 and 2.
The elevation here is an estimated 5600 feet. The climate is reflected
in certain profile features, i.e., lighter colored A horizon, more
reddish hues, and higher pH values, when compared to the previously
discussed profiles. It overlies Clayton basalt.

Horizon A was separated into an All and an A12 principally to
determine if there were laboratory detectable characteristics in the
surface few inches which would indicate recent wind deposited material.
The A11 horizon seemed to be somewhat more silty in the field.

There were many fragments of basalt in the B horizon. These

3ca

fragments were possibly lapilli, as indicated by roundness, rather than

92

weathering fragments of the underlying basalt. This cannot be deter-
mined with certainty at this time. A few manganese concretions were
found in the B3ca horizon.

There was an abrupt transition from the B303 horizon into the
broken vesicular basalt below. Much of the broken basalt had been
recemented with lime, forming an indurated caliche horizon or croute
calcaire. Hany of the basalt fragments had a soft weathered rim which
could be flaked off with the fingernail. But a megasc0pic inspection
of the interior of these fragments revealed them to be relatively un-
weathered. The question arises as to whether the abrupt transition
between the solum and the basalt—caliche layer is due in part to the
caliche formation, thereby protecting the basalt somewhat from wea-
thering, or to the presence of considerable wind deposited material

in the solum.

The profile was not as deep as Profiles 1 and 2. This is believed
to reflect the differences in age. Regardless of whether the soils
have formed directly from the basalt or from a combination of basalt
weathering and weathering of wind blown material, the soils formed
on the older flows could be expected to be deeper. This soil probably

belongs in the Brown great soil group.

Profile 4

This profile probably occurs under a climate very similar to that
obtaining at the site of Profile 3, even though the elevation is some-
what higher, being approximately 6,300 feet. The basalt underneath is

believed to be of intermediate age (Clayton).

93

Profile 4 showed considerable differences from the above des-
cribed profiles. Redder hues were present through most of the profile.
The textures of the horizons were somewhat coarser. There is prob-
ably a correlation between these two features. The coarser textures
should promote more rapid oxidation thereby giving redder colors.

After a little work around the site and after observing the pro-
file, it was fairly certain that contamination from outside sources
had taken place. Many large sand particles of quartz could be detec-
ted by an inspection with a hand lens. However, many fragments of
basalt were found in the solum. In fact, one piece of basalt, 6 x
10 cm., was found in the Bl horizon. This anomaly cannot be readily
explained by field studies. Nowhere in the profile could any depo-
sitional layering be detected. Evidently thorough mixing of the out-
side material with the weathering basalt has been effected. Another
interesting occurrence was noted near this site. In several ant hills
many fine gravels of varied mineralogy, including quartz, were present.
A high percent of the gravels were between 2 and 5 mm. in diameter.

There was a layer of very indurated caliche at approximately

30 inches. Some basalt fragments were cemented into the caliche.

It was not possible to dig through the caliche but it was believed to

be rather thin and that the basalt was immediately underneath it.

The profile appeared to be quite mature in most respects. It is

believed to be a Brown soil, also.

94

Profile 5

This site was selected with the idea of obtaining samples from
another soil on Clayton age basalt. This site was between sites 3
and 4. However, in digging the pit, it was apparent that this profile
was not developed from a one storied primary material. An inspection
of the profile description showed that there were several B horizons.
These appeared to be depositional horizons which had been altered
through pedogenic processes. The presence of much ash and Cinders
in some of the lower horizons was apparent. Because of the obvious
complexity of this profile, it was decided not to make laboratory
analyses. Detailed studies of each horizon are needed to determine
the source and composition of the material added and to evaluate the
pedogenetic changes involved.

The soil was calcareous throughout the profile with the exception
of the A1 and A3 horizons. This is believed to reflect late additions
of basic materials. There has not been enough time elapsed since depo-
sition to leach the profile to a depth greater than 8 inches. This is
in contrast to Profile 4 which is leached to a considerably greater

depth probably because of the addition of more silicic materials.

The dark colors appearing deep in the profile, horizons B31ca

and BSan are noteworthy. It is possible that these horizons repre-

sent some buried soils.

The climate prevailing at this site is comparable to that at sites

3 and 4. The elevation is between 6,000 and 6,400 feet. It would be

classed as a Brown soil.

 

 

95

Profile 6

This soil overlies the Youngest basalts (Capulin). The climate
of the area is comparable to that prevailing at sites 3, 4, and 5. The
elevation is around 6,400 feet.

The profile appeared to be immature in most respects. It was
calcareous to the surface and horizon differences are slight both from
a textural and color standpoint. Boundaries were very indistinct.
Although the slope at this site was somewhat greater (3-4%) than that
at the other sites, it was believed to be quite typical of the deeper
soils found on the younger basalt. As mentioned previously, much lava
is exposed on the younger flows.

It is thought that this soil has formed mainly from volcanic
ash and aeolian material, the latter probably coming in part from sur-
rounding soils. At the base of the solum scoriaceous basalt appeared.
This appears to be the fractured surface of the flow. Much lime coated
the fragments; however, this horizon was not indurated as in the older

soils.

This soil should probably be classed as a calcisolic (28) Brown soil.

 

DISCUSSION OF LABORATORY RESULTS
Mechanical Analyses

The most striking feature of the data given in Table II is the
high silt content. The total silt content ranges from a low of 30.53%

in the B of Profile 4 to a high of 62.77% in the All of Profile 1.

320a
With the exception of Profile 4 every horizon of each profile has a

silt content of greater than 44%. In most horizons it is more than

50%. This is believed to be of special significance in that it strongly
suggests the presence of loess-like material in appreciable quantities.
The silt content in some of the surface horizons is almost as high

as that reported by Smith (66) for some of the loess deposits of
Illinois. They have about the same content of silt as the Portneuf

soil described by Harper (28). Another feature that indicates such

an origin for much of the material is the high pr0portion of sand
composed of very fine sand. In many cases this is greater than 85%.
The amount of sands making up the medium, coarse, and very coarse
fractions was so small that they were combined for weighing and are
expressed as one percentage. The reader is reminded that all the

results are expressed on an organic matter free, CaCO3 free, and

removable 39203 free basis.

Profile 1. This profile shows a fairly constant total sand con-

tent until the B3 horizon is reached where there is a slight increase.

 

97

The Cl horizon shows a marked increase. This increase is due to the
presence of many fragments of disintegrated basalt. Much of the basalt
is weathered to the point where it was easily crushed in preparation
for the analyses, but not to the point where it was further dispersed
during the chemical pretreatments. The same was true for the 83 hori-
zon, but to a lesser degree. This observation was confirmed in the
mineralogical grain analysis conducted later. The increasing propor-
tion of heavy minerals in the B3 and C1 also is due to this feature.

The total silt content in Profile 1 is appreciably higher in the
A horizons when compared to the B and C horizons. The higher silt

content is believed to be due to two factors:

(a) Deposition of a very silty aeolian mantle
which has contributed much of the material
for the formation of the A horizons.

(b) The translocation of some of the clay
formed in A horizons to the B zones, there—
by leaving the A with a higher percentage
of silt.

It is also recognized that some of the soluble weathering products
formed in the A have probably been removed from the solum and that those
formed in the B would not suffer this removal to such an extent. An
increase in clay and a consequent decrease in silt would be the end
result in the B horizon. The depositional difference is also reflected
in the sands. The proportion of very fine sand in the A horizons is
notably higher than in the B horizons.

The 31 horizon has a higher clay content than the 82. In light

of this, the Bl designation perhaps is incorrect, since the 82 is

 

 

 

 

 

 

 

 

 

98
TABLE II
MECHANICAL ANALYSES, HEAVY IINERAL CONTENTS (>2.90 SP. 65.) OF
SAND FRACTIONS AND BULK DENSITIES OF PROFILES STUDIED
Profile 1
Silt
Total Coarse Medium Fine
Horizon Sand Total 50-20 m 20-5 n 5-2 u Clay
All 9.41 62.77 28.22 29.65 4.90 27.65
A12 9.83 62.69 23.98 31.85 6.88 27.42
AB 8.85 64.71 24.82 31.65 8.24 26.40
B1 9.18 47.82 11.30 28.20 8.32 42.95
32 8.86 50.42 19.45 13.95 17.02 40.70
83 10.47 54.64 22.95 22.70 8.99 35.00
91 29.20 43.10 15.75 21.75 5.60 27.45
*Single determinations.
Bulk
Percent of Total Sand Density
Very
Over Fine Fine
Horizon 0.25 mm Sand Sand Heavy
A12 1.69 8.43 87.80 2.00 1.20
AB 3.97 12.12 80.85 3.01
Bl 1.76 10.00 83.40 4.82
33 6.02 11.36 74.20 8.50

99

TABLE II (CONTINUED)

 

 

 

 

 

 

 

Profile 2
Silt
Total __ Coarse Medium Fine
Horizon Sand Total 50-20 m 20-5 n 5-2 m Clay
A1 10.62 61.13 32.55 23.15 5.43 28.42
A3 9.44 58.06 24.25 27.75 6.06 32.45
321 5.33 51.29 27.05 20.60 3.64 43.65
822 5.89 45.58 17.75 22.55 5.28 48.50
B3ca 5.90 51.13 19.42 23.75 7.96 42.95
Cca 8.83 50.14 17.85 25.83 6.48 41.05
Bulk
Percent of Total Sand Density
Very
Over Fine Fine
Horizon 0.25 mm Sand Sand Heavy
Al 2.86 5.96 89.95 2.18 1.31
B 5.78 8.25 82.50 3.15 1.58

22

TABLE II (CONTINUED)

100

 

 

 

 

 

 

 

 

 

Profile 3
__¥ Silt
Total Coarse Medium r15?
Horizon Sand Total 50-20 m 20-5 p 5-2 m Clay
A12 11.28 61.87 34.10 23.15 4.62 26.92
B3ca 10.05 51.04 25.15 18.42 7.47 38.92
Bulk
___, Percent of Total Sand Density
Very
Over Fine Fine
Horizon 0.25 mm Sand Sand Heavy
A11 12.55 21.95 63.20 2.34
A12 7.86 21.55 68.50 2.04 1.31
32 6.67 17.85 72.20 3.13 1.58
7.88 17.68 71.40 2.88

i...

 

TABLE II (CONTINUED)

101

 

 

 

 

 

 

 

Profile 4
Silts 9*—
Total Coarse Medium Fine——
Horizon Sand Total 50-20 m 20-5 u 5-2 p Clay
A11 42.15 41.55 22.65 13.02 5.88 16.35
A12 36.15 42.52 24.60 12.50 5.42 21.25
Bl 30.85 40.19 29.20 9.07 1.97 28.80
Bz 25.06 35.06 19.80 13.48 1.78 40.00
B31 33.85 31.20 17.10 11.98 2.12 35.05
832ca 36.85 30.53 18.55 11.15 0.83 32.58
Bulk
Percent of Total Sand Density
Very
Over Fine Fine
Horizon 0.25 mm Sand Sand Heavy
A11 16.25 24.60 58.20 0.90 1.57
A12 15.86 27.15 55.80 1.13
Bl 16.09 25.54 57.25 1.10
32 14.05 25.68 59.40 0.88 1.62
B31 17.70 23.92 57.20 1.32 1.76
19.58 29.03 50.25 1.13

 

TABLE II (CONTINUED)

102

 

 

 

 

 

 

 

Profile 6
Total Coarse Medium Fine
Horizon Sand Total 50-20 m 20-5 u 5-2 m Clay
A 20.85 45.78 22.20 16.05 7.53 33.40
821 11.16 46.82 21.15 17.61 8.16 41.75
822 11.35 47.64 20.32 18.74 8.58 41.00
Cca 17.83 53.32 23.65 20.25 9.42 28.95
Percent of Total Sand

Very

Over Fine Fine
Horizon 0.25 mm Sand Sand Heavy
A 21.82 16.02 48.42 13.72
B21 19.14 20.12 43.35 17.36
822 22.10 19.92 40.02 17.87
C 32.70 19.00 32.05 16.34

 

 

103

TABLE III

RELATIVE PERCENTS OF HEAVY AND VERY HEAVY FRACTIONS
OF SANDS AND COARSE SILTS

 

 

 

 

Clea

Sand Coarse Silt fi_

Profile Very Very
Number Horizon Heavy Heavy Heavy Heavy
A12 52.3 47.7 40.2 59.8
AB 38.4 61.6 34.5 65.5
B1 48.6 51.4 46.4 53.6
32 58.9 41.1 49.4 51.6
B3 60.5 39.5 55.3 44.7
C1 50.1 49.9 71.2 28.8
All 36.6 63.4 55.3 44.7
A12 33.8 66.2 33.6 66.4
BBca 23.9 76.1 49.9 50.1
Clca 30.4 69.6 53.6 46.4
All 56.2 43.8 57.2 42.8
A12 56.5 43.5 76.6 23.4
B1 51.6 48.4 67.3 32.7
32 55.0 45.0
A 17.7 82.3 44.6 55.4
821 18.2 81.8 34.2 65.8
822 14.1 85.9 43.9 56.1
6.3 93.7 30.8 68.2

104

generally regarded as the zone of maximum clay accumulation. The
lower silt content of the Bl relative to the Bz is a reflection of the
higher clay content.

The ratios between the various silt fractions remain fairly con-
stant until the Bl horizon is reached. Here the coarse silt is much
less abundant. In the BZ horizon the fine silt fraction is much
greater with a consequent reduction in the proportion of medium silt.
The results obtained for the silts in the Bz are highly questionable
because this is the only horizon in any of the profiles which shows
anything approaching this value for the fine silt. Only single deter-
minations were made so no check could be made on this value. It is
believed that an error in sampling or weighing was made. The calcu—
1ations were thoroughly checked. Disregarding the 32, there is a con-
sistent increase of the fine silts with depth until the Cl is reached.
This would seem to indicate that the same processes which cause an
accumulation of clays in the B horizons would promote the accumula-
tion of fine silt. Since the X-ray results, to be discussed later, show
only exceedingly small quantities of discrete layer silicate particles
in the fine silts, the formation of such in the A and their transloca-
tion into the B does not seem to be a factor. Perhaps some of the fine
aeolian material, such as quartz, deposited in the A has moved down-
ward by illuviation, however. The lower amount of fine silt in the C
is due to the presence of many partially weathered grains of basalt.

The relative proportions of sand, silt, and clay in the C1 is

believed to be typical of weathering basalt. The origin of the material

105
which has given rise to the B horizons is not evident from the mechan-

ical analyses.

Profile 2. Much the same distributional pattern is shown among
the various fractions shown in Profile 1. It should be remembered that
these profiles are similar in many field characteristics and that they
have both formed over Raton basalts. One interesting feature is the
higher sand content of the A1 and the A3 horizons relative to the
B horizons. This is believed to be due mainly to the very high com-
bined content of silt and clay and consequent lower sand content;
however, the possibility of an aeolian smear having a little greater
sand content than that deposited at the site of Profile 1 cannot be
discounted. It is believed that a similar silty mantle has been de-
posited at this site as indicated by the high amount of silt in the
A horizons. Once again the high percentage of very fine sand in the
total sand should be noted. Since it was decided during the course
of the study not to make a mineralogical study of this soil, the sands
from only two horizons were sieved and weighed.

The high clay content of the B horizons is evidence of a very
mature soil. In fact, there are indications of some clay pan develop-
ment. Just why this soil should have greater clay accumulations when
compared to Profile 1 is not known. Perhaps it is due to the composi-
tion of the wind—deposited material overlying the basalt. The propor-
tion of the various fractions in the Clca is believed to indicate that

much of the material even in this horizon is not residual from the basalt.

This is in contrast to the 01 of Profile 1.

 

106

Profile 3. The overall size distribution pattern exhibited by
Profile 3 is quite similar to the two previously discussed profiles.
As was mentioned earlier in the section on field studies, the divi-
sion of the A horizon in this profile into an All (2 inches thick) and
an A12 was done primarily to determine possible depositional differences.
There is some indication of this being the case as shown by the higher
clay and fine silt content of the All zone. Perhaps enough fine mater-
ial has been deposited during historic time to cause this feature.

This soil, also, has a very high clay content in the 82 horizon.
This is evidence that some of the features of a clay pan have been
developed. The lower clay content of the B3ca is due to less clay
illuviation and/or formation in the horizon. Once again the fine silt

content in the B horizons is higher.

The proportion of the various sand fractions shows some inter-
esting differences when compared to profiles 1 and 2. The very fine
sand fraction is less, varying from 63.2% in the A11 to 72.2% of the
total sand in the B2 horizon. The fine sand contents in this profile
are appreciably higher. These data are believed to show depositional
differences in the materials making up this profile when contrasted
to l and 2. The >?0.25 mm fraction percentage of the total sand in
the A11 is considerably higher than that in the A12. This is thought

to be further evidence of a recent aeolian smear on the surface.

Profile 4. Profound differences in the textures of this profile
as compared to the previously discussed profiles are evident. The sand

content is markedly greater and the clay content correspondingly less.

107

The silt content is somewhat lower, but still quite high in the upper
part of the profile. It is obvious that this soil has not developed
from primary materials very close in textural composition to those
giving rise to Profiles 1, 2, and 3. It should be remembered that
climatic conditions prevailing at this site are comparable to those
at the site of Profile 3. Likewise, both overlie Clayton age basalts.

A high percentage of the primary material in this soil is believed
to be of aeolian origin, but it is of a coarser nature than that in
Profiles 1, 2, and 3. Some water deposited sediments may be present
in this area. Of course, such an event would have had to occur before
the mesa was isolated by erosion. As pointed out in the discussion
on field studies, no evidence of water-laid sediments was found on the
mesa. An apparently uniform thickness of soil materials overlie the
basalt. The nearness of sedimentary country rock of this profile site
should be noted (See Fig. 1). Perhaps the basalt after flowing out
on the existing sedimentary rock formed flows with thin edges. Aeo-
lian sediments derived from the existing rock could have moved onto the
flow by saltation and/or surface creep, as well as by actual transport
through the air. The surface creep phenomenon could be a possible
explanation of the large quartz fragments in nearby ant hills. Since
the deposition of the sediments the escarpments of 50-100 feet on the
side could have formed as a result of erosion.

Not only is the total sand content higher in this soil, but the
proportion of fine sand is somewhat greater than in Profile 3, and much
greater than in Profiles 1 and 2. The percentage of sands in the >h0.25 mm

fraction is much greater. The percentage of sands in the heavy fraction

108

is consistently lower throughout the profile, also. They range in
percentage (of the total sands) from 0.9 to 1.3. In none of the other
soils was the percent of heavies less than 2.0; usually it was some-
what higher than that.

From the data, depositional differences within the profile are
not apparent. It seems that the soil has developed from a rather
uniform material and the textural differences shown between horizons
are primarily due to pedogenetic processes. It is possible that the
somewhat higher sand content of the All, in contrast to that of the
A12, is partially due to the addition of a late smear of aeolian material.

The low content of fine silt in the B layers is a direct contrast to

the high contents shown in Profiles 1 and 3.
Profile 5. No mechanical analyses were made on Profile 5.

Profile 6. Many differences in the size distribution pattern are
evident when the data from Profile 6 are inspected. It should be remem-
bered that this soil has developed on the Capulin (youngest) lavas and
that it is quite immature in most respects. The total silt content
is not as high in most cases as that in comparable horizons in Profiles
1, 2, and 3; while the sand contents are somewhat higher. The fine
silts are consistently the highest through the profile of any of the

soils studied. This is believed to reflect a difference in the nature

of the aeolian material.

The clay content in the soil is somewhat surprising in view of its

immaturity. However, as pointed out in the field studies discussion,

109

it is quite possible that some of the clay has been derived from soils
already existing in the area through wind deposition of a local nature.
In addition, it is believed, principally because of other laboratory
studies, that much volcanic pyroclastic material has been incorporated
into this profile.

The higher clay content of the 3 layers relative to the Cca and A
is undoubtedly due, in part, to pedogenetic processes, but it is thought
to be due partly to depositional differences, as well.

The sands which are larger than 0.25 mm make up a higher percent-
age of the total sands in this profile than in any other. This is due
to the presence of many large particles of basaltic composition which
may or may not be of volcanic origin. It is not believed that much of
the soil above the Cca horizon is derived from the basalt below.

The very high percentage of heavy minerals here reflects the
immaturity of this profile, because the coarser fragments of basaltic
material have not decomposed. (These aggregates were thrown down in
the heavy fraction.) However, it is believed that even under a com—
parable formation time the heavy mineral content would be greater in
this profile than some of the others due to a different mineralogical

composition. This is discussed later in the secion on mineralogical

analyses.

Mineralogical Analyses of Sands and Silts

The mineralogical grain investigations produced the most informa-

tive data of any of the studies concerning the nature of the materials

110

giving rise to the soils. The data must be considered as only semi-

quantitative in nature. Despite the fact that a great amount of time

was spent on this phase of the work, it was not possible to identify a

number of the grains on each slide. In the tabulated results these

are labeled as "others." It was felt that it was better to group these

minerals of uncertain identity in such a group than to take additional

time to name each of them. .Analyses were made of selected horizons

only because of the very time consuming nature of the study.

The most revealing information brought out in the mineralogical

analyses is that showing the great diversity of minerals present in

all the profiles. The results are shown in Tables IV, V, and VI.

In the author's opinion, the presence of such minerals as zir-
con, garnet, tourmaline, green amphibole, quartz, and microcline is
conclusive evidence of the admixture of materials from outside sources.

This will be considered a recognized fact in further discussion.

It is obvious from the data in the tables that several mineral

species appear in both the very heavy and heavy fractions.

As was pointed out previously, several difficulties were encoun-

tered in making the 3.35 sp. gr. separation. It is believed that the

preponderence of magnetite hindered the separation markedly. Also, the

fact that some minerals, i.e., iddingsite, had a density very close to
3.35 caused them to appear in appreciable amounts in both fractions.
Among the minerals labeled "others" in the >3.35 sp. gr. sepa-

rates of both sands and silts, sphene (titanite) and epidote were very

common and were identified in every slide. Excellent interference

111

figures were obtained from both in most of the slides. Staurolite,

monazite(?), brookite(?), and corundum(?) were found infrequently.

Among the "others" in the heavy fraction (sp. gr. 2.9-3.35) epidote

was again very common. Euhedral apatite and grayish-brown hypersthene

were often found. Kyanite, andalusite, and Sillimanite were more rare.

Chlorite was very rare.

Among the other Opaques such minerals as hematite (probably often
a weathering product of magnetite), leucoxene (probably often an altera-

tion product of ilmenite), pyrite, marcasite, and some unidentified

metallics were included.

Profile 1. One of the most interesting facts shown by the data

given in Table IV is the decreasing content of magnetite with depth in

the very heavy sands. This relation does not hold true for the very

heavy silts where the C horizon has the highest magnetite percenta e.
t 1 3

Why this discrepancy between the size fractions exists is not readily

explainable. It would appear from the sand percentages that it could

be explained on the basis of magnetite being more resistant to weather-

ing than some of the other minerals. This does not explain the rela—

tionship in the silt, however. The overall high magnetite content in

this profile may be interpreted as an indication that basaltic materials

have been contributed in quantity to the primary materials. This con-

tribution could have come about by:

(a) The deposition by wind of finely divided
sediments of basaltic composition, prin—

cipally volcanic ash, in the upper part of
the profile.

112

(b) The weathering basalt leaving behind its

less weatherable components such as mag-
netite and augite.

It is believed that both of these processes have contributed some

of the magnetite in each horizon because of mixing but that the rela-

tive proportion varies greatly.

The idea expressed in (a) does not rule out the hypothesis regard—

ing the deposition of a loess-like material previously proposed. Both

have probably occurred, but at different periods of time. It seems

very improbable that it could have been due to an ash which was both

high in quartz and magnetite. Basaltic ashestsually have no quartz,

while those high in quartz have little or no magnetite.

The distribution of iddinsite in the profile is revealing. It

makes up a high percentage of the very heavy sands in the C1 and a

fairly high percent in the 83. Although present, it was not found

among the very heavy sand grains counted in the 82. However, in the

heavy fraction it was recorded in every horizon in both sands and silts.

It has been pointed out previously that this mineral occurs in both

density separates. The very high content in the C1 and B3 horizons is

evidence that much of the material in these horizons is residual from

the basalt below. The presence of iddingsite in much decreased quanti-

ties in the upper horizons may be due to the following:

(a) Mixing from the underlying B and C

(b) Deposition in basaltic ash

(c) Relicts from basalt fragments which have weathered away.

 

113
In any case, it appears that iddingsite is more resistant to decompo-
sition than the parent olivine. Olivine is in weathering stage 3 of
Jackson, et a1 (36). It has been proposed that olivine attains greater
stability when transformed into iddingsite (81). It is of interest
to note that only in a very few of the iddingsite grains was there
any evidence of olivine remaining. These few were in the Cl horizon.

The appearance of much amphibole, especially the green variety,
above the C1 layer in the heavy sands and silts is significant. It
is the opinion of the author that the green amphibole is definitely
of extraneous origin and that it has not formed from the augite inthe
basalt. Humbert and Marshall (34) have been proponents of this latter
idea in their weathering studies of diabase. The presence of tourma-
line in both silts and sands in the 33, the bulge of green amphibole
sands in the 82, and the higher amounts of brown amphibole in the 82
and B3 are other noteworthy observations. These distributional fea—
tures in the profile are thought to be indications of aeolian deposi-
tion of materials of different mineralogical composition at different
times. Much mixing has occurred since.

The percentage of augite is high throughout the profile, but
especially so in the C1. Most of that in the Cl horizon is probably
derived from the basalt. However, that which is in the upper horizons
has probably been derived in part from the basalt, with subsequent
mixing, and part from basaltic ash.

The mineralogical composition of the light fraction of Profile 1
is given in Table V. The data are probably not as accurate as those

for the very heavy and heavy fractions because of the fewer grains counted.

114

Generally speaking, itmay be said that quartz and potassium feld-
spars decrease with depth while the converse is true for the plagio-
clase. No attempt was made to distinguish the plagioclases, a diffi-
cult procedure, even in thin sections. Much of the plagioclase, especi-
ally in the C1, was cloudy and without well defined characteristics.

It was identified as labradorite by having a biaxial positive inter-
ference figure and an occasional grain showing albite twinning. The
idea is proposed that these cloudy fragments are the pseudo—aggregates
of McAleese (50, 51). This would account in part for some of the
chemical properties to be discussed later. Aggregates of true layer
silicates (clays) were not identified, although it is possible that
they were present in small quantities.

There is no doubt that the quartz and microcline are of aeolian
origin. This can be said because of their abundance and shape. They
are mostly sharp angular particles; a few rounded frosted grains of
quartz are in the sand.7

It appears that Profile 1 has a very complex hidbry. Much of the
lower profile, 33 and C1, is composed of products derived from the
basalt. Much of the primary material in the upper horizons is of
aeolian origin. Loess-like material and volcanic ashes of different
composition have been added. Much mixing of the different components
has occurred due to plant roots, the soil fauna, and physical processes

such as swelling, cracking etc.

The mineralogical analyses of the sands and silts in Profiles 3,
4, and 6 will not be discussed in as much detail as were those of

Profile 1 since they are similar in many respects.

115

TABLE IV
MINERALOGICAL ANALYSES 0F HEAVY FRACTIONS
0F SANDS AND COARSE SILTS

Profile l

>3.35 Density Separates of Horizons

 

 

 

Sand* Silt**

Mineral A11 A12 B2 85?, C1 A11 82 B3 C1
Magnetite 80.5 72.7 80.2 62.6 55.8 64.2 65.3 63.2 79.1
Other

Opaque 6.5 12.6 7.4 13.9 3.3 17.5 16.0 19.8 3.9
Zircon 1.4 1.4 0.8 4.5 1.0 2.5 0.4
Garnet 0.9 2.3 1.0 0.8 0.3 1.5 0.7 2.8 0.4
Rutile 0.6 0.3 0.4 0.3
Amphibole 1.4 0.9 1.0 0.8 1.1 0.7 1.3
Pyroxene 4.7 0.9 1.5 2.9 2.3 3.0 0.3 . 5.1
Iddingsite 15.2 38.0 8.6

Others 4.7 8.6 8.1 3.7 0.3 7.1 16.0 10.0 2.7

 

*Entire sand fraction.

**The silt fraction ranging from 5 to 50 u.

Profile 1 (Continued)

3.35-2.90 Density Separates

of Horizons

116

 

 

 

 

 

__¥ Sand __¥ Silt

“fineral A11 B2 B3 c1 All 32 33 5;—
Augite 38.4 42.7 37.2 47.5 23.9 26.6 26.2 74.1
Amphibole

Green 20.0 31.2 12.4 0.5 29.5 26.6 19.0 7.4

Brown 3.7 9.0 1.6 5.5 10.2 8.6 2.8
Opaque 27.9 8.1 10.8 27.0 21.2 17.2 9.0 10.6
Iddingsite 2.1 3.0 17.8 23.2 1.8 0 8 0.5 1.4
Tourmaline 1.6 1.4 2.9
Glass-Garnet 0.4 4.1 0.5
Zircon 1.8 1.2
Biotite 0.5 0.4 1.6 0.5 0.5
Other 7.4 5.1 17.0 1.9 14.3 13.1 33.3 3.2

TABLE IV (CONTINUED)

Profile 3

117

 

 

>3.35 Density Se

 

¥

 

 

 

 

 

parates of Horizons

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sand Silt

Ear“ A1 1 A12 {32 33 ca A11 A12 132
Magnetite 50.4 49.1 59.8 46.4 50.0 49.3 61.6 48.8
Other

Opaque 15.7 22.3 19.3 21.0 17.4 25.8 13.4 21.9
Zircon 1.3 3.6 0.9 1.5 2.9 0.9 3.9
Garnet 0.9 1.6 0.7 2.9 2.9 0.4 2.3
Rutile 0.4 1.9 0.9 0.7 0.4 0.5
Pyroxene 2.2 0.3
Other 27.8 20.9 18.7 27.5 24.3 21.3 20.4 22.4

3.35-2.90 Density Separates of Horizons
‘7 Sand y 5111: ‘

.Elneral A11 A12 B2 B303 A11 A12 82 B§Q§
Augite 46.0 45.9 27.6 32.5 24.8 21.6 11.3 17.5
Amphibole

Green 4.2 2.8 15.6 15.0 33.7 38.4 42.6 40.3

Brown 0.4 1.9 2.0 1.3 7.5 3.4 6.4 13.4
Opaque 33.4 39.7 37.6 33.3 20.6 12.0 18.5 9.0
Tourmaline 1.1 0.8 2.6 1.8 3.0 1.6 1.1
Glass-Garnet 0.9 1.1 0.8 3.4 2.2 0.4 2.0 0.8
Zircon 0.4 1.7 0.9 0.4 2.8 1.5
Biotite 0'4
Rutile 0.4 0.4 0.4 0.4
Other 14.7 7.5 15.4 9.8 8.3 20.2 15.1 16.0

 

 

118

TABLE IV (CONTINUED)

Profile 4

 

>3.35 Density Separates of Horizons

 

 

 

 

 

 

 

 

 

 

 

Sand Silt
Hagnetite 46.3 53.0 56.9 49.0 40.4 51.5
Other Opaque 19.8 14.8 19.4 24.1 18.7 25.9
Zircon 7.5 2.4 1.4 4.4 3.4 5.9
Garnet 3.2 6.4 2.9 2.0 3.8 1.7
Rutile 0.8 0.3 0.3 0.9 1.5 1.3
Amphibole 3.0 1.2 1.2 1.2 5.8 0.4
Pyroxene 0.4
Other 18.2 21.8 17.9 18.5 26.3 13.0
3.35-2.90 Density Separates of Horizons
Sand Silt

liner“ A11 B1 Bszca A11 31 B32ca
Augite 2.3 2.5 11.8 2.0 4.3
Amphibole

Green 21.7 30.4 26.8 45.4 46.7 22.3

Brown 9.3 9.5 7.8 11.6 8.7 7.2
Opaque 27.9 17.7 20.3 15.9 10.0 27.3
Tourmaline 3.1 4.4 2.0 2.4 4.0 0.7
Glass-Garnet 0.8 2.5 2.0 0.5 0.7 2.2
Zircon 2.3 0.6 1.3 0.5 0.7 4.3
Biotite 0.8 0.6 0.7
Other 31.8 31.6 27.4 23.1 27.3 30.1

 

119

TABLE Iv (CONTINUED)

Profile 6

 

 

>3.35 Density Separates of Horizons

 

 

 

 

 

 

 

 

 

 

Sand Silt __
Miner§1 A B22 Coal A B22 Ccal
Magnetite 64.6 77.0 71.6 61.3 73.5 71.4
Other Opaque 12.8 6.3 5.9 10.9 10.9 17.4
Zircon 0.9 2.7 2.6 0.5 0.4
Garnet 0.4 2.0 0.9
Rutile 0.4 0.4 0.9
Amphibole 0.9
Pyroxene 2.1 3.2 18.0 0.4 0.5 7.6
Other 18.8 10.8 2.4 23.5 13.7 2.2
3.35-2.90 Density Separates of Horizons
Sand ___ Silt ‘_
Mineral A. 822 Ccal A .322__ C25;
Augite 68.8 75.1 88.3 50.8 56.8 72.3
Amphibole
Green 16.3 8.0 2.7 25.4 24.0 15.0
Brown 4.0 2.3 0.9 1.9 4.5 2.3
Opaque 3.0 10.6 6.3 18.3 6.1 4.5
Tourmaline 1.0 0.5
Glass—Garnet 0.4
Biotite 0.5 0.5 0.5
Other 6.4 4.2 1.3 12.5 7.3 5.9

 

120

Profile 3. The magnetite content of both sands and silts in the
very heavy fraction is markedly lower throughout the profile than in
Profile 1. This is probably due mainly to a difference in primary
material, the lithology of which was somewhat less basaltic. .Although
the younger age of this profile, with less accumulation of resistant
minerals as a consequence, could be a factor. The 82 Of this soil
shows a bulge in magnetite content relative to both upper and lower
horizons. This would not be due to pedogenetic accumulation but to
an influx Of aeolian material high in magnetite which has been added
to the magnetite derived from the underlying basalt.

In the heavy mineral suite Of both sands and silts, the augite
content is much greater in the A horizons as compared to the B layers.
In view of the data concerning magnetite, the augite figures cannot
be readily explained. If it were due to differential weathering the
magnetite should increase in the surface layers along with the augite.

The greater amount of green amphibole in the heavy (3.35-2.90)
sands and silts in the B2 and B3ca horizons relative to the A layers
is believed to substantiate the contention that the lower part Of the
profile has formed from materials differing from those giving rise to
the All and A12. It does not seem possible that it is due to the in-
creased weathering Of the green amphibole in the A horizons in view of
the data concerning augite. It is unlikely that there is that much
differential existing between the weathering rates of the two minerals.
The much greater amount Of green (and brown) amphibole in the silts

than in the sands is believed to be indicative Of the silty nature

of the added materials. Possibly the abundant green amphibole was

121

deposited in volcanic ash of andesitic and/or dacitic composition.

Only very fine sands were analyzed in the light fraction. NO
silts were counted. The data presented in Table VI concerning Profile 3
may be somewhat erroneous. The counts on the slides from this hori-
zon were made when the principal criterion being used for distinguishing
plagioclase was the showing Of albite twinning. Since there were no
grains counted in which albite twinning could be seen, none were counted.
The difficulty Of using albite twinning as a distinguishing criterion
has been pointed out already. The only noteworthy feature shown by
the data is the abundance of quartz in all three horizons. The greater
amounts shown for lower horizons may or may not be significant.

In summary, it can be said that this profile has developed from
materials which are more homogeneous than those giving rise to Profile
1. Probably fewer stages of deposition are represented. Either the
basalt has weathered and contributed minerals to the solum or else some
of the aeolian material was of basaltic composition. Much mixing has
subsequently occurred. The gradual diminution of some of the mineral
species with depth is not nearly so apparent as in Profile 1. This is
believed to indicate that the underlying basalt has contributed less

to the lower horizons in this profile.

Profile 4. The magnetite in the very heavy sands and silts of
this profile is somewhat higher in the B 320ihorizon than in the over-
lying horizons. This is believed tO indicate more mixing of the wea-
thering residue Of the basalt with the sediments in this horizon than
in the upper zones. The content of zircon, garnet, and tourmaline is

higher throughout this profile than in Profiles 1 and 3; conversely,

122
the percentage of augite in the various horizons is much lower. This
indication of a different overall composition (and origin) for this
material bears out the results of the mechanical analyses.

The higher content of garnet in the very heavy sands and silts and
of green amphibole and tourmaline in the heavy sands and silts in the Bl
horizon is indicative of a material of different composition influ-
encing this horizon.

The distribution of green amphibole from the standpoint of size
throughout the profile is odd. It occurs in very high quantities in
the silts of the All and El, being 45.4% and 46.7%, respectively, but
drops off to 22.3% in the B32ca. However, in the sands it is actually
higher in the B3203 than in the A11--26.8% as compared to 21.7%. The
reasons for this distribution are not readily apparent. It is not likely
that it is due to weathering, or else the content in the silt of the
A11 would be lower. It is perhaps due to a deposit of a somewhat coarser
material first and then this followed by a siltier deposit; this could
greatly affect the distribution of any one mineral species between
size fractions.

The light fraction of the very fine sands was analyzed for only
two horizons as shown in Table VI. The silt fraction of the 832‘:a
horizon was also analyzed in order to compare its composition to that
of the very fine sand. It is very similar. The quartz decreases with
depth and the plagioclase increases. This trend was expected; that is,
if the underlying basalt has contributed more to the lower horizon-~a
premise already presented. However, the increase of potassium feldspar

in the lower horizon is not explainable on this basis.

123
From the available mineralogical data, it would seem that this

profile has deve10ped mainly from transported material that is fairly
homogeneous but in which some variation occurs due to differences in
origin and/or the velocity of the transporting media. The latter would
affect the mean particle size. Basaltic materials are present, espe-
cially in the lowest horizon. This is believed to be derived mainly
from the underlying basalt; however, some sediments of basaltic composi-

tion could have exerted an influence. Much mixing has occurred.

Profile 6. The results presented in Table IV are significant
in several ways. The magnetite content is very high in all horizons
analyzed, being almost as high as in Profile 1. It should be remembered
that this soil is quite immature. A noteworthy feature of the magne-
tite distribution is its greater percentage in both sands and silts in
the 822 horizon than in either the A or Clca' Zircon, garnet, and ru-
tile are present but in amounts so low that they were not among the
grains counted in some of the slides.

The percentage of augite in the heavy fraction is very high in
both sands and silts; but, in each horizon it makes up a higher pro-
portion of the sand than it does the silt. lany of the sand particles
counted as augite were, in reality, basalt fragments, but which con-
tained enough augite to throw them into the heavy fraction during the
density separation. This is evidence of a low state of weathering
of this soil and explains partially the higher quantity of augite in
the sand. Green amphibole is present but in not such quantity as in

Profiles 3 and 4, or in the upper horizons of Profile 1. The percentage

124
in the silt is higher than that found in the sands. However, in both
cases it decreases consistently with depth.

The quartz and microcline-orthoclase content in this profile,
Table V1, is much lower than in Profiles 3 and 4. Both decrease con-
sistently with depth; the quartz comprises only 11.9% of the lights in
the Clca horizon. The plagioclase percentage is high throughout the
profile and increases with depth, reaching a percentage of 79.4 in
the Clca- Rarely, muscovite and glass were recorded. The rarity of
the glass is surprising considering the immaturity of the profile.

It would appear from the results of the mineralogical and mechani-
cal analyses data that this soil has formed principally from the basalt.
This may very well be true, especially for the Clca horizon, but it
is believed that much of the upper part owes its origin to pyroclastics
of basaltic composition. It appears that a rather thick blanket of
basaltic ash and Cinders was laid down first and then more recently
other materials have been added, hence the greater frequency of quartz,
potash feldspars, green amphibole, etc., as the surface is approached. It
is quite possible that the basaltic ash deposit was followed by a thin-
ner deposit of andesitic or dacitic ash. Also, it seems probable that
deposition of materials, probably loess-like, has followed the basaltic
material. Whether this was before, after, or contemporaneous with the
andesitic (or dacitic) ash is not discernable from the available data.
Of course, deposition of sediments derived from already exbting soils
in the area could account for much of the quartz, microcline, etc.,

in the upper solum. Since the materials were deposited, much mixing

of the sediments has been effected.

125

TABLE V

MINERALOGICAL.ANALYSES OF LIGHT FRACTION
((2.90) VERY FINE SAND AND SILT (5-50 u)

Profile 1 Horizons

 

 

 

 

Very Fine Sand Silt

Mineral A12 §§:_ Cl A12 ,_§£ C1
Quartz 66.9 38.1 11.2 75.0 48.8 2.0
Microcline 14.1

Orthoclase 29.6 1.1 8.3 11.4 1.6
Plagioclase 7.5 20.0 85.6 10.0 22.7 93.7
Glass 2.8 3.2 4.1 1.6
Muscovite 1.9 3.2 1.1 6.5 0.8

Other 6.6 5.8 1.1 6.7 6.5 0.4

 

126

TABLE VI

MINERALOGICAL COMPOSITION or LIGHT FRACTION
((2.90) or VERY FINE SANDS OI' PROFILES 3, 4, AND 6

 

 

 

 

Profile 3 Horizons Profile 4 Horizons Profile 6 Horizons
Mineral A11 A12 B3ca B1 B32ca B32ca* A B22 Clca
Quartz 59.8 71.9 77.6 75.6 53.8 57.0 36.8 19.3 11.9

Orthoclase—
Microcline 35.5 25.2 14.6 10.2 26.5 23.9 16.4 9.2 1.7

Plagioclase 7.1 17.9 12.4 36.8 63.3 79.4
Glass 0.8 0.9 0.9
Muscovite 0.9 - 0.8 0.8 0.9
Biotite 0.8 1.7 1.7
Opaque ”1.9 0.9 2.9 2.5 2.8 2.6
Other 1.9 1.9 4.8 4.7 1.7 5.8 4.9 2.8 0.9

 

*This Bgzca sample is a silt sample (5-50 m). It was included
for a comparison with the very fine sand from the same horizon.

127

Thin Section Studies

It is emphasized at the outset that the thin section studies were

made on the basalt principally to determine composition and to study

the weathering of the components. It was necessary to study the compo-

sition in order to properly determine the origin of the minerals in the

overlying soil. Another aim of the study was to obtain information

regarding the weathering of the basalt under the prevailing conditions.
The thin section studies of the soils were carried out primarily

from a mineralogical standpoint. Some studies of the microstructure

of these soils would be desirable, but it was felt that such could

not be incorporated into this work at this time. In order for such a

study to be really informative, the complex relations of the soil pri-

mary materials should be worked out. It is hOped that the present study

will aid considerably along that line.

The observations made on the individual slides follow.

Profile 1

Weathered Basalt. A photomicrograph is shown in Fig. 6A. Thin

 

section observations show the rock to be holocrystalline and to have an

aphanitic groundmass with the phenocrysts reaching a maximum size of

0.5 mm.
Composition:
Labradorite——70%
Augite--20%
Olivine-Iddingsite--7%

lagnetite-Hematite--3%

128
Mineral Characteristics:

Labradorite. Positive. Low birefringence. A few euhe-
dral phenocrysts present but mostly in the form of subhedral laths in
the groundmass. Albite and Carlsbad twinning common, pericline rare.
Highly altered——indications of some sericite and much clay. Altera-
tion is considerably more pronounced where the mineral is in contact
with a vesicle.

Augite. Positive. 2v est. at 70°. ZAc 50°. High
birefringence. Brown, indicating an iron—rich variety. Non-pleochloric.
Mostly subhedral. Twinning uncommon. Appears remarkably fresh.

Olivine-Iddingsite. Olivine occurs as euhedral pheno-
crysts of 0.9 mm maximum size and as much smaller subhedral particles
in the groundmass. Both are drastically altered to iddingsite. How-
ever, the iddingsite pseudomorphing the phenocrysts is redder than that
developed from the groundmass olivine. Practically all the phenocrysts
are entirely altered. A few have small relatively unweathered cores.
The optical properties of the olivine were not determined since none could
be found which showed the proper orientation.

Very faint optic axis figures were obtained on the iddingsite.
Some appeared to be almost uniaxial; however, one particle showed a
figure with an estimated 2V of 40°. Optical sign was undeterminable.
Wavy extinction was evident. The deep red, almost opaque, appearance
of the iddingsite prevented the determination of most optical prOperties.
It was found, though, that the Optical orientation and properties dif-

fered from those in the olivine core of the same phenocryst.

129

The iddingsite shows some characteristics which may be interpreted
as evidence of two-stage alteration (See Fig. 6A). The outer rim of the
red iddingsite may have been formed by deuteric alteration while the more
yellow hazy interior rim and alteration along fractures is indicative
of weathering. This internal alteration appears to be in concentric layers
which decrease in frequency toward the center of the phenocryst. This
supports the results of Steven (71) and Sun (74) who have reported idding-
site being a sheet structured silicate. The optical properties of the

internal rim could not be determined accurately.

4
*1

C Horizon-~Slide A. This thin section was cut from very highly

weathered basalt; it is considerably more weathered than the previously
discussed slide. Some portions of the section are slightly brownish due
to iron oxide, either hematite or goethite, stains. Some black stains
are present along fractures. This may be secondary magnetite, some
manganese oxides, or even organic matter. The latter was found in the
cracks of some of the hand specimens of weathered basalt. The grinding
compound, used in making the thin section, could be imbedded in the
crevices of the section, also. No photomicrographs were made from this
slide.

C1 Horizon--Slide B. The material from which this section was made

 

has the characteristics common of the solum. However, it may be relict

material left from the basalt representing a more advanced weathered con-

dition. Figure GB is a photomicrograph taken from this section.
Labradorite is identifiable which gives a good biaxial positive

interference figure. Augite with high birefringence (second order) is

130
present. An occasional very small pleochloric green fragment is found.
It may be amphibole, but chlorite is a possibility. Iddingsite is common.
No unaltered olivine was found. At least one grain of quartz, confirmed
by a uniaxial positive interference figure, is present. Probably several
grains could be found in the slide; however, it undoubtedly is rare at
this depth. One grain thought to be microcline was found.

Some of the clay encountered is sufficiently oriented to give second
order green interference color. Illite, montmorillonite, and vermicu-
lite have sufficient birefringence to give this color; neither kaolinite
nor chlorite do have (25). In one mass of clay a good pseudouniaxial
interference figure is obtainable. The figure is not centered so the
2V cannot be estimated. In one instance the clay appears to have been
deposited along channels, but in another instance it appears to have
weathered in place from a subhedral mineral. Around many crystal frag-
ments, iddingsite, plagioclase, etc., a rim of clay appears (See Fig. 68).

g2 Horizon. The outstanding characteristic of this slide is the

 

abundance of small angular fragments (See Fig. 6C). Many of these are
quartz which was confirmed by interference figures. Many other minerals
such as microcline, basaltic hornblende, green amphibole, the latter
being common, are present.

Pinkish banded shards of glass were definitely Identified. They
appear to be markedly similar to those given by Swineford (75) for the
Pliocene ash deposits of western Kansas.

Aggregates of basaltic material which are rounded and appear to be

coarse ash (or lapilli) are common (See Fig. 7A). Much of the material

131
has been removed from the interior of these fragments, either by wea-
thering or abrasion during preparation of the thin section. In some cases
only skeletons remain.

Several rounded iddingsite fragments are found in the section (See
Figs. 6C and 6D). It is postulated that these fragments are pseudo—
morphs after olivine deposited in ash. It was not possible to determine
whether the fragments were already iddingsite when deposited or whether
they are products of weathering. The fact that the parent olivine was
not recorded may be of significance.

At least one mass of clay is present which gives a good pseudo-
uniaxial negative interference figure. Other masses are present which
show maximum second order green interference color. Elongate shreds
of clay which are somewhat pleochroic (light brown-reddish brown) are

common. It is possible that these have formed from glass shards.

Profile 3--Basalt
The specimen is a vesicular porphry with a very fine aphanitic
groundmass. Probably the crystallinity can best be described as hypo-
crystalline (some glass) although it may be holocrystalline with magne-
tite dust disseminated through the matrix which imparts the appearance
of black glass. Some vesicles have coatings of clay stained red with

iron oxide. Others have some calcite deposition. A photomicrograph

is shown in Fig. 8D.
Composition:

Labradorite (assuming no g1ass)--64%

Augite--20%

132

FIGURE 6

PHOTOMICROGRAPHS OF PROFILE 1

Profile 1. Weathered basalt showing olivine partially altered to
iddingsite and partially altered labradorite. Brown fragments
are augite. Magnification x 85. Nicols not x.

Profile 1. C1 horizon showing iddingsite undergoing further altera—
tion when embedded in the soil matrix. Labradorite at lower left.
Magnification x 85. Nicols x. ‘

Profile 1. Hz horizon showing soil matric containing iddingsite
and angular quartz fragments. The quartz is mainly of silt size.
Magnification x 85. Nicols x.

Profile 1. Bz horizon. Same in part as C, but magnification is
x 225. Shows disintegration of iddingsite and some clay deposition
along channels (middle lower right). Note the red stains in the

clay. Nicols x.

e.

1.
. \s.
a.

z
.w
v

w

e
...

 

A.

134

FIGURE 7

PHOTOMICROGRAPHS OF SOIL AND CALICHE ENCRUSTATIONS ON BASALT

Profile 1. B Horizon showing a highly weathered coarse ash frag-
ment which contains a small iddingsite particle. Notice soil pores.
Magnification x 40. Nicols not x.

Basalt from Grenville, New Mexico, showing edge of caliche crust.
Labradorite (gray-white laths) is slightly altered. Augite is the
highly birefringent material. Magnification x 40. Nicols x.

Caliche crust with embedded basalt fragments. The large altered
particles (middle left) are olivine-iddingsite. This section is
approximately 3 mm. further into the caliche crust than in B. Magni-

fication x 85. Nicols x.

 

A.

136

FIGURE 8

PHOTOGRAPHS OF BASALTS

Basalt from site 4 showing olivine alteration in varying degrees.
The red iddingsite splotches in the groundmass are in contrast to
the brown augite. Magnification x 85. Nicols not x.

Same as A but with nicols x.

Scoriaceous basalt from profile 6 showing partially resorbed quartz
inclusion and much black glass. Magnification x 85. Nicols x.
The area at upper left border is a vesicle.

Basalt from Profile 3 with very fine aphinitic texture. Large pheno-
cryst (along right margin) is olivine with slight alteration around
margin. Phenocryst in upper middle is augite. Some clay formation
around vesicle (lower left corner). Magnification x 85. Nicols x.

 

138

Olivine--12%

Magnetite—-4%

Mineral Characteristics:

Labradorite. Occurs principally as microclites. Shows
very slight alteration.

Augite. Light yellowish green. Positive. 2V = 60°. A
few euhedral phenocrysts (0.4 mm size) are present but mostly occur as
subhedral to anhedral crystals in the groundmass. NO apparent alteration.

Olivine. Occurs mostly as euhedral phenocrysts (maximum
size 1.2 mm). Excellent Optic axis figures. Negative. 2V about 880.
This indicates a fayalite content of approximately 12%. Only a slight
indication of iddingsite formation along the borders--otherwise unaltered.
Some magnetite inclusions. Some anhedral to subhedral crystals in the

groundmass. NO optical properties determined.

Site 4*--Basalt
The rock may be described as a coarse aphanitic porphry. Photomi-
crographs are shown in Fig. 8A--nicols not crossed and in Fig. SB--nicols
crossed. It is holocrystalline.
Composition:

Labradorite--58%

Augite-—22%

Olivine--15%

Magnetite--5%

Mineral Characteristics:

II“This specimen was not obtained from the profile since it was not

possible to reach the underlying basalt because of indurated cahche. It
was obtained from the surface of the flow in a nearby roadcut.

139

Labradorite. Positive. 2V est. at 70°. Carlsbad twinning
is very common. Some alteration. Zoning not evident. Subhedral.

Augite. positive. 2v est. at 60°. Slightly pleochloric
(greenish brown—-pinkish gray). The pinkish tint probably indicates more
titanium than usual. Subhedral. Fresh appearing.

Olivine. Large (1.6 mm) euhedral phenocrysts present.
Positive. 2V est. at 86°. Many inclusions of euhedral magnetite present.
Many are rimmed with iddingsite; others are replaced completely (See
Fig. 8A). Many of those with rims have partially altered interiors. This
interior alteration product appears to be quite different from the idding-
site. However, this may very well be incipient iddingsite formation.
The other possibility is that it represents both deuteric alteration and
alteration due to weathering.

Some of the subhedral to anhedral groundmass Olivine is entirely
altered to iddingsite while other crystals may have an iddingsite band
with less altered interiors and a surrounding external rim which is also
less altered. This is believed to reflect differences in composition
of different portions of the crystal. The more ferrous portions are thought
to be more susceptible to alteration. Successive stages of crystalliza-

tion would cause the difference in composition.

Profile 6-—Basa1t
This section was cut from a specimen which is probably a volcanic
bomb (or block) found at the bottom of the profile; however, there is no
proof of this. This problem has been discussed already. The specimen

is highly vesicular and is hypocrystalline. The groundmass is dense,

fl_wi—i flew...» -~--- -—~~ —— -— — —

 

140
aphanitic, and contains much dark glass, labradorite microlites, and an-
hedral to subhedral augite. Olivine, augite, and plagioclase all occur
as phenocrysts. Several quartz inclusions are present. These have been
reported before for some of the Capulin basalts (72). A photomicrograph
is shown in Fig. 8C.

One mass of clay is present on which a hazy pseudouniaxial negative
interference figure was obtained. It is not clear whether this has
formed in place from devitrified glass or is a vesicle filling. Some
glass in the process of devitrification is present. Some of the vesicles
are lined with clay.

Composition:
Glass-~30%
Labradorite-~47%
Augite-~15%
Olivine--5%
Quartz--2%
Magnetite (as crystals)-- 1%
Mineral Characteristics:
Labradorite. That in groundmass occurs as microlites.
Shows mainly Carlsbad with some albite twinning. Some phenocrysts present
(as large as 2.5 mm). A positive interference figure was obtained on one
from which the 2V was estimated at 700. Some phenocrysts Show well
defined zoning. Others have an interior composed of a black and clear
blebby mass. The black material is probably glass, but the clear dots
show birefringence. Stobbe (72) considers this material a groundmass

inclusion. However, in the slide studied, the difference between these

141
inclusions and the regular groundmass is obvious. In one instance the
large phenocryst is surrounded by the above described material rather than
it being an inclusion. Regardless of the composition of the material
the large phenocrysts represent early plagioclase crystals which later
reacted with the magma as its composition changed.

Augite. Brown with light greenish tinge. Positive.
2V est. at 55°. Subhedral to anhedral. Occasionally occurs as inclu-
sions in plagioclase.

Olivine. Positive. 2V est. at 86° for phenocrysts;
indicates high MgO content. Optic sign for anhedral groundmass olivine
is positive. 2V could not be estimated.

Glass. Occurs in two forms—-re1atively large masses which
are in various stages of devitrification and much dark groundmass material.
The dark color is thought to be due to disseminated magnetite dust.

Quartz. Confirmed by uniaxial positive interference figure.
All grains show partial resorption (See Fig. SC). In most cases the
inclusion is rimmed by black glass but in others a rim of small augite

crystals occurs.

Basalt Encrusted with Caliche
A specimen obtained near the village of Grenville was cut in order
to determine possible weathering changes with caliche deposition. Some
revealing features are shown. The basalt is a holocrystalline aphanitic
porphry. Two photomicrographs are shown in Figs. 73 and 7C. The percentage
composition was not estimated.

Mineral Characteristics:

142
Labradorite. Mostly in the form of laths which show
albite and Carlsbad twinning. One large phenocryst, with Carlsbad twin-
ning, present; does not have inclusions like the specimen from Profile 6.
Slight alteration. No noticeable change in degree of alteration of
laths out in caliche rim.
Augite. Positive. 2V est. at 650. Light brown. Rela-
tively unweathered, but exhibits occasional development of Back stains.
Olivine. Some exceptionally large euhedral phenocrysts
with good dome and pinacoidal develOpment are present. (one has a length
of 4 mm. measured parallel to the c axis.) Optic sign is negative
and 2V is estimated at 88°.
Studies made on the subhedral to anhedral groundmass olivine showed
the optic sign and optic angle to be very close to that in the phenocrysts.
Alteration of the phenocrysts to iddingsite appears similar to that
from site 4; however, the alteration rim is not as sharply separated (See
Fig. 7C). Good Opportunities were afforded by this slide to study the
change in Optical prOperties in the same phenocryst as olivine is altered
to iddingsite. In one the hazy Bxa interference figure of the iddingsite
appears with a small 2V (determined to be negative by using a quartz
wedge). Obviously, the optic axis of the iddingsite and olivine cannot
coincide, which indicates a different optic orientation. In another
fragment of iddingsite, embedded in the caliche rim, a better Bxa figure
was obtained which was negative and had an estimated 2V of 35°. Probably

this fragment is made up of purer iddingsite than the previous one.

143

The olivine in the groundmass appears to be olivine which is wea-
thering somewhat differently to that in the phenocrysts. The first
stage appears to be a yellow stain development. This stain is probably
due to an iron oxide dust (goethite?) released by the altering olivine.

The end result of the alteration appears to be the same iddingsite as

that formed from the phenocrysts.

This slide seems to hold the most convincing evidence that idding-
site is, at least, partially a weathering product. This is indicated
by the distinctly identifiable iddingsite (not just stains) developed
along fractures. (See fragment in middle left of Fig. 7C).

Caliche encrustation. There is a rough banding of disintegrated
basalt fragments out in the rim. The process may be described as a
"spalling off" process. It appears that the calcite enters fractures,
which parallel the outside of the basalt boulder, begins to grow and

pushes the fragments progressively further away from the parent boulder.

Summary

The following conclusions may be drawn as a result of the thin

section studies:

(a) The primary components of the basalt show increasing resis-

tance to alteration according to the following sequence.

Glass—solivine-eLabradorite->Augite-9Magnetite (probably)

(b) Iddingsite is more nearly in equilibrium with its environ-

ment than is the parent olivine; greater stability is the result.

(c) Iddingsite is formed, at least, in part because of weathering.

144

Deuteric alteration may be the cause of the outer rims often observed.

(d) Caliche encrustation causes a "peeling" of basalt due to
crystal growth (calcite) along concentric surface fractures.

(e) A high percent of the larger particles in the B2 of Profile 1
is composed of angular quartz and feldspar of silt size. Glass, green
amphibole, basaltic hornblende, iddingsite, and lapilli were identified.

Mixed materials have contributed to the formation of the profile.
Chemical Studies

Organic Matter

The quantity of organic matter was determined for the surface hori-
zons only, except that in the case of Profile 3, it was determined for
the A12 horizon. The very thin All of this profile would have had an
abnormally high content due to the abundance of grass roots in the sur-
face two inches. The determinations were made principally to determine
the effect of climate and/or time on accumulation. It was not intended
to study the effect of organic matter on the pedogenetic processes in
the soils.

The amount in Profile 1 is significantly greater than that in the
other profiles. This is a direct influence of the cooler, more moist
climate. It is doubtful if time is of much influence in causing this
difference. It is generally conceded that only a short time is required,
in terms of soil formation, for the organic matter content to become
constant. The difference in the species of grasses growing at this

site compared to the others may have exerted a minor influence.

145
The reason for the slightly higher percentage shown by Profile 6
as compared to 3 and 4 is somewhat surprising since prevailing climates
at the sites are believed to be closely comparable. It should be remem-
bered that this is the youngest soil. The sampling procedure, already
described, in sampling Profile 3, may account for its slightly lower
percentage when compared to 4. The somewhat higher elevation at site
4 may also enter in, only in that it affects temperature, however. Site

3 probably receives more precipitation annually than site 4.

pH
The values obtained in the laboratory show the same trends as those
determined in the field; even though they differ as much as 0.8 of a
unit (near the neutrality point). Since the field values have been

discussed in detail, no further discussion is necessary.

Total and External Specific Surface of Horizon Samples

Specific surface determinations were made on the total samples from
selected horizons. The results are reported in Table VII.

There is a good correlation between the percent clay and total surface
in Profile 1 down through the Bl horizon. Starting with the 52 horizon,
there is a sharp increase in surface area even though mechanical analyses
shows the clay content to progressively decrease. This would seem to
indicate a change in clay mineralogy. At the extreme in the Cl horizon
a surface area of 242 mZ/gm was determined and yet the clay content was
only 27.5%. It can readily be seen that the clay would have a surface

area similar to that listed for montmorillonite (46). Some of the clay

146

investigations to be discussed later aid in the explanation of these high
values. It was very difficult to determine the true end point in the
reduction of the ethylene glycol to a monomolecular layer after heating
the samples to 600°. Consequently, the external surface measurements

are erratic as can be seen in the data obtained on Profile 1. All that
can be said for certain when considering the external surface data is
that there is considerable swelling clay in each horizon as shown by

the lower values after heating and that there is considerably more in

the lower part of the profile.

The values obtained for total surface for Profile 3 Show the same
trends as the clay content in the profile. This is also reflected in the
values for external surface. The external values are probably high, which
is an indication that the end point in the ethylene glycol removal had
probably not been reached, when the final weighing was made. The values
obtained indicate some expanding clay in each horizon but the differences
between horizons appear to be due almost entirely to the amount of clay
rather than to mineralogical differences.

Bower and Gschwend (8) have reported that the presence of much
alkaline earth carbonate affects the values of external surface measure-
ments and that variable results are obtained. This may have affected
some of the external values; however, it could not have been a factor
in Profile 1 where no free carbonates were present.

Determinations were made only on selected horizons in Profile 4.
The results compare closely with those obtained for Profile 3 and appear

to be correlated closely with the clay content. On the basis of these

147

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149
data, it seems possible to conclude that the clay mineralogy is much the
same throughout the profile. Some expanding clay is present as indicated
by a marked decrease in values upon heating.

The data from Profile 6 are interesting. Although the clay content
of the B horizons is about the same as that in the B horizons of Pro—
file 4, the total surface is considerably higher. Some differences within
the profile are apparent although they can be explained principally on
the differences in clay percentage. However, the lower value obtained
for the A horizon when compared to the Clca cannot be so explained.

A has a clay content of 33.4% compared to 29% for the C1ca' It appears

that the lowest horizon may have considerably more swelling clay.

Cation Exchange Capacity
When considering the results of the cation exchange capacity work,
it is well to remember that organic matter was not removed. Such was not
recommended in the method used (62). The capacity added by the organic
matter is of no consequence, except in the A horizons where it is slight.

The values obtained for Profile 1 are consistently high. If it is

assumed that all the exchange capacity is due to the clays, it can be

readily seen by dividing the mechanical analyses percentages into the

CEC that each gram of clay would have approximately 1 me exchange capacity.

This would hold true until the C1 horizon is reached where the CEC would

be 1.4 me/gm clay. All these values approach, or are higher, than those

given for pure montmorillonite.

 

150

Since it has been reported recently (50, 51) that the silts and
sands from some soils on basalts have considerable exchange capacity, it
was decided to test some of the silts and sands. The very interesting
results are given in Table VII.

Unfortunately this problem came up late in the course of the study
after fractionation into the various separates had already been made.
Consequently, there was not sufficient quantities of most of the fractions
to permit a determination on all the silts or sands. The implications
of the spot studies made are obvious, however. It is not possible to
assign all the CEC to the clay fraction. Whether this is a property unique
to soils influenced by basaltic primary materials (either hard rock or
pyroclastics) is not known.

The high values obtained for the silt fractions, and sand, for the 01

of Profile 1 are amazing. These results could be due to the presence
of:
(a) Undispersed aggregates Of expanding layer
lattice silicates, or
(b) The pseudoaggregates, partially weathered
primary minerals, of McAleese (50, 51).
It is not known whether thorough dispersal was accomplished, but it will
be recalled, that these samples were subjected to rather drastic pretreat-
ments. Despite this, the possibility of aggregates cannot be ruled out.
As pointed out in the mineralogical data discussion, there are some frag-
ments in the light fraction of the lower horizons which were listed as
plagioclase but did not show some of the characteristics. These may be

the so-called "pseudoaggregates." Only further investigation can solve

this problem satisfactorily.

151

The CEO values obtained for the various horizons in the silts are
believed to be indicative of: (a) differences in the nature of the pri—
mary materials with the basalt contributing much to the lower horizons,
(b) the more drastic weathering of the materials in the upper solum.

The idea expressed in (a) has already been suggested by the data obtained
in other phases of the work.

The CBC values obtained for Profile 3 are high but do not show
great variations between horizons. The decreased value of the Alzrelative
to the All horizon can be explained on the basis of the higher amount of
clay and the probable greater organic matter content. The value shown by
the 82 is not as high as would be expected from the increased clay con-
tent relative to the A12 and the BBCa' The higher value of the 830a,
in view of the lower clay content, is noteworthy. The lower value of the
B2 of this profile, when compared to the 32 of Profile 1, probably indi-
cates a lower quantity of swelling clay, considering the fact that it has
a higher clay content. The problem of the silt contribution complicates
matters, though, and made it difficult to make comparisons.

The higher value obtained for the coarse silt in the surface hori-
zon compared to the 33ca is probably not significant because the dif-
ference is small (6 and 4 me/lOO g), and the tests were not made in dupli-
cate. The zero value obtained for the very fine sand is in striking con-
trast to the value obtained for the sand in the C1 of Profile 1.

The values obtained for the three selected horizons of Profile 4
are not unique. It is believed because of the nature of the parent

materials of this profile that the particles larger than clay conuibute

152
little, if any, to the exchange capacity. Of course, this is conjecture
since no tests were made. If the premise is true, it indicates that the
amount of expanding clay in this profile is not especially high. No
mineralogical differences in the clays of the different horizons can be
detected from these data. .

The results obtained for Profile 6 are surprisingly low, and no
ready explanation is available. The results are at variance with the
surface area data. The results indicate a low content of expanding clays
except in the Clca horizon. This horizon has a considerably lower clay
content (29%) but the highest CEC value. It is not known what contribu—
tion, if any, is made by the silts and/or sands, but it is thought that
it may be considerable because of their mineralogical nature. This would

further reduce the values for the clays.

Clay Investigations

 

K20 Contents

The K20 content was determined on aliquots from both coarse and fine
clays from selected horizons in Profiles 1, 3, 4, and 6. The results
are shown in Table VII.

The K20 content is higher in the coarse clay than in the correspond-
ing fine fraction in every case, although the difference is much smaller
in some horizons than others. This, of course, indicates that the con-
tent in illitic clays is greater in the coarse clays. The possibility
of potassic feldspars in the coarse clays can be discounted since in only

one instance was there even a slight indication of any feldspar, including

153
plagioclase, in the X-ray analyses of the clays.

Profile 1 shows consistently decreasing K20 content with depth in
both coarse and fine fractions. This should not be unexpected in view
of the results of the other studies already discussed. Determinations
were not made on the 32 and 83 samples because the clay suspensions from
these horizons were spilled. The trends are evident even without determi-
nations on these horizons, however. The very low content in the C1
horizon is notable. It is barely higher than the content of the under-
lying basalt, determined to be 1.04%. The increasing content upward
through the solum is believed to be indicative of deposition of micaceous
minerals in the upper solum. These have since been altered into illitic
clays. Also, illitic material, which was already of clay dimensions, could
have been deposited at the same time. If the decomposition of potassic
feldspars, with consequent recrystallization into illitic clays, had
been much of a factor, the K20 content would probably be higher in the
Bl horizon. The latter process would entail a synthesis of a different
silicate, clay, and would be expected to show accumulation in the B.

The more drastic weathering expected in the A horizons does not appear
to be a factor in light of the results obtained on Profiles 3 and 4 to
be discussed subsequently.

The All of Profile 3 shows a higher quantity in both coarse and fine
fractions. This reflects the depositional difference mentioned several
times previously. The higher content of the B horizon cannot be so easily
explained. Some depositional difference may enter in here also; however,

pedologic processes are probably the principal cause. It seems likely

154

that potassication of expanding lattice minerals has occurred. The latter

were probably the first products formed during the breakdown of the vol-

canic ash thought to be a major component of the primary materials. If

it is assumed that much micaceous material was deposited in the primary
materials originally, then the possibility of greater breakdown occurring

in the upper solum, whbh would leave it deficient in illite, must be con-

sidered.

The results obtained for Profile 4 show the same characteristics

as those for Profile 3.

The K20 contents in Profile 6 decrease slightly with depth in a

general pattern. The fine clay of the 821, however, has a slightly higher
content than the fine clay of the A horizon. Although relatively high,
the K20 content of these clays cannot account entirely for the low CBC

values obtained for this soil. The markedly lower potassium content of

the Clea horizon probably indicates less weathering, i.e., less conversion

of expanding lattice minerals. The slight changes in the values between

the A and B horizons reflect the immaturity of this profile.

x-Ray Analyses

In this discussion it will be assumed that the reader is familiar

with the laboratory procedures previously described.
Profile 1. The x-ray diffraction patterns obtained for the clays
of Profile 1 are reproduced in Fig. 9. Six patterns, with appropriate

labels, for each horizon are combined into one unit. The patterns from

four horizons are shown on the page.

155

It is readily apparent that considerable differences throughout the

profile exist in the mineralogical composition of the two fractions. The

0 o
coarse clays are much higher in quartz, as shown by the 3.35 A and 4.26 A

(the latter not marked) lines. These are reflections from the 101 and 100

planes, respectively. Quartz is either absent or very low in the fine clays.

It should be remembered that the 003 reflection of illites cannot be

distinguished from the quartz line at 3.35. The coarse fractions are

appreciably higher in illitic material and kaolinite. There is only a

slight indication of kaolinite in the fine fractions. The fine fractions

are much higher in expanding lattice silicates. These clays may be vermi-

culite, montmorillonite, or randomly interstratified materials, in vary-

ing amounts. The results are far from conclusive. The presence of much

0 .
expanding clay is indicated by the marked increase in the 10 A peak with

K saturation and further increase with heating to 550°. The latter could
not be due to the destruction of some of the crystalline components, i.e.,
kaolinite, with a consequent increase in the intensity of the remaining
components since kaolinite is indicated as being very low at the outset.
The fact that there is a marked increase with heating to the high tempera—
ture indicates that the K01 leaching and heating to 1100 is not completely
effective in closing the interlayer Spacings.

The lack of discrete lines corresponding to the longer spacings in

the fine clay is somewhat puzzling. This may be due to the factors listed

below:

(a) Much randomly interstratified material is

present. Units of montmorillonite, vermiculite,

156

and illite, or a combination of any two,
are disordered along the c axis. Ordered
interstratification may be present, but
it could not be detected.

(b) The very small size of the particles which
would increase scattering and cause a
poorer degree of orientation.

(c) The poor crystallinity of the clays.

It is believed that the above factors all enter in but that they are
listed in order of decreasing importance.

Some differences in the clay mineralogy within the profile show
up. The quartz content of the coarse clays decrease, as shown by the
4.26 2 line, with depth. The same is true for illite and kaolhite.

Even though they undoubtedly exist, differences in the fine clay miner-
alogy within the profile are not so apparent. There is some indication
that a material with a spacing between 14 and 173 is more common in the
lower profile than in the A11 horizon. This difference between horizons
may be due to orientation of the clays on the plate, however. This material
with the spacing between 14 and 17 X may be montmorillonite which is not
fully expanded, an 002 (or higher order) reflection from ordered inter-
stratified minerals or mixtures of vermicuhte-montmorillonite.
Interstratification is indicated in all the fine clays of this pro-
file by the broad platform between 17-14- and 10 X in the glycerated
samples. The platform is lowered by the K saturation and heat. Using
the same criterion, interstratification is also indicated in the coarse

clays but to a much lesser extent.

157

The coarse clays show a broad peak between 14 and 17.7 X. It prob-
ably indicates the presence of montmorillonite in various degrees of
expansion. Vermiculite-montmorillonite intermediates are also a possi-
bility. A slight amount of chlorite may be present as indicated by the
failure of the floor of the platform between 17.7 and 10 R to drop after

heating to 550°.

The peak at 32 2 (not lined) in the AB horizon may or may not be
significant. In the course of the investigation, many such broad peaks
at the low angles showed up, but they could not be reproduced. If this
peak is significant, it may indicate an ordered interstratification of
vermiculite and montmorillonite since it comes at approximately 32 2.

Patterns made from the total clay fraction of the AB horizon are
shown in Fig. 12 for comparison.

Profile 3. The overall patterns (See Fig. 10) are quite similar
to those obtained for Profile 1. The 10 X peaks in the glycerated samples
in both fractions and the 7.2 2 peaks in the coarse clay are stronger than
in Profile 1. Again the tremendous increase in the 10.2 peaks of the fine
clays upon K saturation and heating attest to the presence of much swel-
ling clay. The fact there is only a diffuse bump in the lines around 17.7
2 suggests that most of the swelling clay is randomly interstratified.

The slight increase in the 7.2 2 line with K saturation is interesting.
The only eXplanation which comes to mind is that there is some halloysite
present and that the heating removes the water, thereby collapsing the

o
mineral to a material with a co spacing of 7.2 A. It is also possible

that heating because of removal of water from between discrete particles

158
increases the degree of orientation so that the kaolinite present shows
up better. K saturation cannot increase the kaolinite content.

No differences in the clay mineralogy within the profile can be
determined. It is interesting to note that the 10 3 peak heights of the
coarse clays of the A11 and B3Ca horizons are about the same although
the K20 content of the 830a is markedly greater (See Table VII).

Profile 4. Patterns for the coarse and fine clays of Profile 4
are shown in Fig. 11. The patterns are like those for Profile 3 in
practically all respects. There is possibly somewhat less interstrati-
fied material in the fine clays as shown by the sharper descent of the
pattern from the beginning point (20 20).

Profile 6. Diffraction patterns are shown in Fig. 12 for the fine
and coarse clays from two horizons of Profile 6. Both horizons show
considerable amounts of material with spacings between 14 and 17.7 X
in the coarse clays. Some random interstratification is also sug-
gested. It appears that the coarse clays in the profile contain more
swelling clay than any of the other profiles excepting the lower portion
of Profile 1. Illite and kaolinite contents are high in the coarse clays.

It appears that most of the clays in the fine separate are randomly
interstratified. There is a small bulge at 17.7 X in both patterns,
however. It should be mentioned that between the times runs were made
on the glycerated samples and the K saturated samples, about two-thirds
of the intensity of the X—ray unit was lost. The reason for this loss
in intensity was not determined. The glycerated samples were run with

a scale factor of 8 and 4 (the switch was made where the break in the

159
line occurs) while the K saturated and 5500 heated samples were run
with a scale factor of 2.

The evidence concerning the swelling clay further complicates the

explanation of the low CEC results (See Table VII).

Differential Thermal Analyses

Differential thermal patterns were obtained on the coarse, fine,
and total clays for selected horizons in Profiles 1 and 3. Patterns
were obtained for the fine clays in each horizon of Profile 6. No thermal
analyses were made on the clays from Profile 4. A resistance of 150 ohms
in the recording unit was used. It is realized now that a lower resis-
tance should have been used. At the time of the determinations it was
hoped that comparisons could be made between the two fractions. The results
of these analyses are shown in Fig. 13.

The fine clays of Profile 1 all show endothermic peaks between 100-
2000 C, which corresponds to the loss of the interlayer water in the
expanding clays. The peaks increase until the C1 horizon is reached where
there is a sharp decrease. This seems very odd since all the other
data indicate an abundance of swelling clay in this horizon. The fine
clays also show a distinct endothermic peak between 500 and 600°. This
endothermic reaction is caused by the loss of structural 0H ions from
the crystal lattice. It often is interpreted as a kaolinite peak; however,
some other clay minerals, especially illite, have a similar endothermic
reaction (25). In light of the data obtained from other studies includ-
ing X-ray, it seems unlikely that the destruction of kaolinite contributes

much to the intensity of this peak, especially in the C1 horizon. The

160

question arises whether many of the properties of the Cl horizon are
due to poorly organized crystalline or partially amorphous materials.

The differences shown between the coarse and fine clays of Profile 3
are marked. The lack of sharp peaks in the coarse clay patterns suggest
that a high percent of the material is quartz. Layer lattice silicates
in this size range gives more pronounced thermal reactions than quartz.
The exothermic peak in the fine clay of the A11 horizon is due to unoxie

dized organic matter left after the H202 treatment.

If the 100°— 200° peak is taken as a criterion for expanding lattice
minerals, the indications are that the percentage of these minerals in
the fine clays increase with depth.

Another fact pointed up by the patterns of Profile 3 is that the
fine clay reaction determines the patterns of the total clay. The patterns
for the total clay and fine clay for the All and 82 horizons are remark-
ably the same.

The thermograms obtained for the fine clays of Profile 6 are very
similar to those obtained for the upper horizons of Profiles 1 and 3.

No difference can be seen within the profile.

Summary of Clay Mineral Studies
Pronounced differences occur between the mineralogy of the coarse
clays (2.0-0.2 u) and the fine clays ((10.2 n). These differences show
up in the K 0 analyses, in the X-ray diffraction, and in the differential

thermal analyses.

161

The coarse clays are higher in quartz, illite, and kaolinite
while the finer clays are higher in vermiculite-montmorillonite and
randomly interstratified expanding material. In some of the fine clays
no discrete mineral species can be detected, after glyceration, in the
X-ray patterns.

Differences in the clay mineralogy within Profile 1 are evident
(See Fig. 9). They are less pronounced in Profile 6. The only signi-
ficant differences that can be detected within Profile 3 and 4 are from
the K20 contents. X—ray patterns of the clays throughout the profiles

are much the same.

X—Ray Studies of Silts, Sands, and Weathered Basalt

 

Patterns obtained after an attempted orientation of fine silt from
the All of Profile 3 particles on a ceramic plate are shown in Fig. 12.
The amount of layer silicates in the fraction, indicated by 001 reflec-
tions, is very low. The same thing is shown in the fine silts from the C1
of Profile 1 in Fig. 14 (lower right). These results appear to eliminate
the possibility of discrete particles of layer lattice silicates being the
principal cause of the CEC of the silts.

Powder diffraction patterns for the coarse silts from 5 horizons
of Profile 1 are shown in Fig. 14. Some interesting trends are evident.
The quartz (4.26 and 3.35 X lines) decreases and the feldspar (4.1 and
3.2 2 lines) increases with depth in the profile. It is not possible
to clearly distinguish between the plagioclase and potash feldspars but

it is fairly certain that most of the peak area in the lower horizons

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162

FIGURE 9

X-RAY DIFFRACTION PATTERNS OF CLAYS FROM PROFILE 1

Upper left-~All Horizon
Lower left--AB Horizon
Upper right-~81 Horizon

Lower right——Cl Horizon

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

164

FIGURE 10

X-RAY DIFFRACTION PATTERNS OF CLAYS FROM PROFILE 3

Upper left--A11 Horizon
Lower left--A12 Horizon
Upper right--82 Horizon

Lower right--BBca Horizon

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166

FIGURE 11

X-RAY DIFFRACTION PATTERNS OF CLAYS FRO! PROFILE 4

Upper 1eft--A11 Horizon
Lower left--A12 Horizon
Upper right--B1 Horizon

Lower right--B31 Horizon

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Lower

Upper

Lower

FIGURE 12

DIFFRACTION PATTERNS OF CLAYS AND FINE SILTS

1eft--Profile 6--A Horizon, Coarse Clay and
Fine Clay

left--Profile 6--B22 Horizon, Coarse Clay
and Fine Clay

right--Profile 1--AB Horizon, Total Clay
(See also Fig. 9)

right—-Fine Silt (Plated out) of Profile 3--
All Horizon (See also
Fig. 10)

168

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FIGURE 18

DIFFERENTIAL THERMAL DIAGRAHS 0F CLAYS

Left-~Profile l
Hiddla~~Profile 3

Right-~Protilo 6

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172

FIGURE 14

X-RAY DIFFRACTION POWDER PATTERNS OF SILTS,
CLAYS, SANDS, AND WEATHERED BASALT
WITH A PLATED OUT FINE SILT
FOR COMPARISON

Upper left-—Profile l-—Coarse Silts (See also Fig. 12,
upper right)

Lower left-—Profile 6-—Powder Patterns of Coarse and
Fine Clay from A Horizon
(See also Fig. 12, upper right)

Middle upper-—Profile 1--C1 Horizon Sands and
Weathered Basalts

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and Fig. 12, upper right)

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174
can be attributed to the plagioclase. The significant 4.47 2 line is
the so-called "common" clay line. It is due to 110 and/or 020 reflections.

Powder diffraction patterns for the fine silts of the Bl, B3, and
C1 horizons from Profile 1 are shown in Fig. 14 (upper right). The same
trends pointed out above are evident but the quartz content in the C1
is much greater. This is thought to be confirming evidence of mixing from
above; the fine silt particles work down in the profile easier than the
coarse silts and sands. Note the presence of the 4.47 clay line in all
horizons and its much greater height in the C1 horizon.

Some noteworthy resuhs were obtained on the powder diffraction pat-
terns of two samples of weathered basalt from the bottom of Profile 1.
These are shown in Fig. 14 (upper middle) along with patterns from the
total sands and very fine sands. There is absolutely no indication of
Quartz (4.26 and 3.35 2 lines) in the samples. This would seem to eliminate
the possibility of quartz being in the profile as a weathering residue or
product. The plagioclase line (3.2 and 4.1 X) is intense. The 020, 110
clay line (4.47 X) is evidence that layer silicates are a direct weather-
ing product of the basalt. The same line is very prominent in both the
coarse sand and very fine sand patterns. This is evidence that layer
lattice silicates are present either in undispersed aggregates or in parti-
ally weathered primary minerals (pseudoaggregates). The CEO of the coarser
fractions Of this horizon can be explained, at least in part, by the pre-
sence of the layer silicates. They did not show up in the "oriented"

fine silts since they are not in discrete flaky particles.

SUMMARY

The soils studied have developed from heterogeneous primary
materials. The lower horizons of Profile 1 have developed mainly
from basalt. The upper part of the profile has deve10ped principally
from volcanic ash and loess-like material. Profiles 2 and 3 have
developed from fine aeolian materials which have been deposited at
different times. Much of this material was of basaltic composition.
The primary materials are more homogeneous, however, than those giv-
ing rise to Profile 1.

Profile 4 has developed from considerably coarser aeolian
materials than the other profiles. It appears that the primary material
was of rather homogeneous composition.

Profile 5 (field observations only were made) has apparently devel-
0ped mainly from pyroclastics.

Profile 6 has developed from aeolian materials, principally of
basaltic and andesitic (possibly dacitic and/or trachytic) composition.

Profiles 1, 2, 3, and 4 exhibit the characteristics of relatively

mature soils. Profile 6 is an immature soil.

Mechanical analyses show a high proportion of silts in all the
soils (somewhat lower in Profile 4) which is believed to be indicative
of deposition of loess-like materials. Some textural differences within
the profiles are probably due to depositional differences; however,
pedogenetic processes have been very active in effecting the deve10p-
ment of B horizons with a high clay content in each soil. At least one

horizon in each soil has a clay content of more than 40%.

176

The mineralogical analyses of the sands and silts were instruc-

tive in revealing depositional differences within the profiles. These

analyses show that much mixing has occurred in all the profiles, but

some horizons show much more than others. The mineralogical analyses

give worthwhile data concerning the types of sediment from which these

soils have been produced. The sediments have been admixed with weather—

ing products of basalts in some cases. A very diverse suite of very

heavy and heavy minerals is present in these soils. Minerals which
could not possibly have formed from the underlying basalt are preva-

lent. Volcanic glass, indicative of ash deposition, was found deep

in some of the soils.
Thin section studies reveal the underlying rocks to be normal

olivine basalts with variable amounts of glass. The following weather-

ing sequence (ease of weathering) of the primary mineral components can

be listed. The most stable minerals are listed last.
G1ass-’01ivine-9Plagioclase-aAugite-aMagnetite?

It is not certain that primary olivine is less susceptible to

weathering than glass. However, iddingsite, a common alteration pro-

duct of olivine, is probably more resistant than glass.

The studies strongly indicate that iddingsite may be formed, at

least in part, as a result of weathering of the olivine. It appears

that the ease of alteration is somewhat conditioned by the composi-

tion of the olivine. The higher the fayalite content the greater the

likelihood of iddingsite formation.

177

Thin section studies of indurated soil aggregates show the common
occurrence of well oriented clay aggregates which give good optical
'interference figures. Some of these are oriented along channels indi-
cating deposition. Others appear to have formed as pseudomorphs in
place.

Organic matter determinations of surface horizons show Profile 1
to have an appreciably higher content, indicative of the cooler, more
moist climate. The pH values obtained for Profile 1 indicate a much
higher leaching rate. More drastic weathering is the result.

Specific surface and cation exchange capacity data indicate that
considerable quantities of swelling clays are present throughout the
profiles. Most of the clay in Profile 1, especially in the lower hori-
zons, seems to be of an expanding type. The silts, and even sands,
in the C1 horizon of Profile 1 show amazingly high CEC values. The fine
silts in selected upper horizons of Profile 1 and in the B3ca and All
of Profile 3 have small CEC values. This exchange capacity is due either
to the presence of undispersed aggregates or partially decomposed primary
minerals in which secondary layer silicates are being formed as deter-
mined by X-ray powder diffraction studies.

The CEC of the horizons of Profile 6 are surprisingly low, con-
sidering their high clay content and immaturity of the soil.

The K20 content of the coarse clays is higher in every case than
the corresponding fine clay. This is evidence of a higher illitic clay

content in the coarse clays since no indications of potash feldspar

178

were shown in the X—ray analyses. The B2 horizon clays have the high-
est KgO contents except in Profile 1 where the A horizons have a markedly
higher content.

The X-ray analyses show profound differences between the mineral-
ogical composition of the coarse and fine clays. The coarse clays are
very high in quartz and quite high in illite and kaolinite. 0n the
basis of the x-ray diffraction results, the illite appears to be higher
than or equal to the kaolinite content. The fine clays are composed
mostly of expanding lattice minerals.

The differential thermal studies bear out the results of the X-
ray studies in most cases. However, the indicated low content of
expanding material in the fine clay of the Cl horizon is completely
at variance with all the other data. The possibility exists that there
is a considerable quantity of poorly crystallized material in the C1
of Profile 1 which could have high exchange capacity, high total speci-
fic surface, etc., but still be so poorly organized that it gives poor
thermograms and diffraction patterns.

The mineralogical analyses indicate that most of these soils are
in an intermediate state of weathering. The lower part of Profile 1
and most of Profile 6 show evidence of being considerably less weathered
than the other soil horizons. Evidently the expanding lattice material
in Profile 1 collapses with the addition of potassium in the upper part
of the profile; hence the higher illite content. Of course, deposi-
tional differences, i.e., more micaceous materials, have probably been

added to the upper part of Profile 1 which undoubtedly affects the

mineralogical composition.

179

Just why the B horizons of Profiles 3, 4, and 6 have higher illi-
tic contents is not clear. The X—ray and the DTA analyses do not show
that other mineral species increase in the A relative to the B. It
is quite possible, however, that kaolinite and quartz have increased
relatively, but not in quantities that can be readily detected. There
is no evidence whatever that montmorillonite increases in the surface
horizons.

X—ray powder diffraction patterns of the weathering basalts under-

lying Profile 1 show the formation of layer silicates in_situ. No quartz

is present.

BIBLIOGRAPHY

l. Antevs, Ernst. Postpluvial Climatic Variations in the Southwest.
.Am. leteor. Soc. Bull. 19:190-193, 1938.

2. Aguilera, N. H., and Jackson, H. L.

Iron Oxide Removal from Soils
and Calys.

Soil Sci. Soc. Amer. Proc. 17:359-364, 1953.

3. Baldwin, B. GeolOgy of Union County. Bull. 63 Part I New Hex.

Bureau of Mines and Mineral Resources (In Press).

and Bushman, F. X. Guides for Development of Irrigation

Wells near Clayton, Union County, N. Mex. Circ. 46 N. Mex.
Bureau of lines and Mineral Resources (In Press).

5. Barshad, I. Chapt. I Soil Development.

Bear, F. E., Ed.
of the Soil.

Chemistry
Rheinhold Publ. Co., New York, 1955.

e. Birrel, x. s., and Fields, u. Allophane in Volcanic Ash Soils.
Jour. Soil Sci. 3:156-166, 1952.

7. Bonnet, J. A. The Nature of Laterization as Revealed by Chemical,
Physical, and Mineralogical Studies of a Lateritic Soil Pro-

file from Puerto Rico. Soil Sci. 48:25-40, 1939.

8. Bower, C. A., and Gschwend, F. B. Ethylene Glycol Retention by

Sons as a Measure of Surface Area and Interlayer Swelling.
Soil Sci. Soc. Amer. Proc. 16:342-345, 1952.

9. Bragg, W. H. and Bragg, W. L. The Crystalline State Vol. I G.
Bell and Sons, Ltd. London, 1955.

10. Bretz, J. H., and Horberg, L. Caliche in Southeastern N. Mex.
Jour. Geol. 57:491-511, 1949.

11. Brown, G., and Stephen, 1. A Structural Study of Iddingsite from
New South Wales, Australia. Am. Mineralogist. 43:120-147,
1958.

12. Carroll, D. Some Aspects of Soil Mineralogy. Roy. Soc. W. Australia
Jour. 23:7—11, 1936.

13. Collins, R. F. Volcanic Rocks of Northeastern New Mexico.

Bull.
Geol. Soc. Amer. 60:1017-1040, 1949.

14. Colwell, J. D. Observations on the Pedology and Fertility of Some
Krasnozems in Northern New South Wales. Jour. Soil Sci.
9:46-57, 1958.

181

15. Deb, B. C. The Estimation of Free Iron Oxides in Soils and Clays
and Their Removal. Jour. Soil Sci. 1:212—220, 1950.

16. Dryden, L., and Dryden, C. Comparative Rates of Weathering of Some
Common Heavy Minerals. Jour. Sed. Petrol. 16:91—96, 1946.

17. Edwards, A. B. The Formation of Iddingsite. Amer. Min. 23:277—281,
1938.

18. Ellis, B. S. Genesis of a Tr0pica1 Red Soil. Jour. Soil Sci. 3:
52—62, 1952.

19. Evans, G. L. Geology of the Blanco Beds of West Texas. Bull.

20. Ferguson, J. A. Transformations of Clay Minerals in Black Earths
and Red Loams of Basaltic Origin. Aust. J. Agric. Res. 5:
98-108, 1954.

21. Fields, H, and Swindale, L. D. Chemical Weathering of Silicates
in Soil Formation. New Zealand Jour. Sci. and Tech. 36:140-
154, 1954.

22. Goldich, S. S. A Study in Rock Weathering. Jour. Geol. 46:17-58,
1938.

23. Gradwell,‘l., and Birrell, R. 6. Physical Properties of Certain

Volcanic Clays. New Zealand Jour. Sci. and Tech. 36:108-122,
1954.

24. Griggs, R. L. Geology and Ground Water Resources of the Eastern
Part of Colfax County, New Mexico, Ground Water Report I,
New Mex. Bur. Mines and Min. Resources, 1948.

25. Grim, R. E. Clay Mineralogy. McGraw-Hill Book 00., Inc. New York:
1953.

26. Rallsworth, E. G., Costin, A. B., Gibbons, F. R., and Robertson,

G. K. Studies in Pedogenesis in New South Wales. II The Choco-
late Soils Jour. Soil Sci. 3:103-124, 1952.

27. Hardy, E. L. Climate of New Mexico. pp. 1011-1024. U.S.D.A. Year-
book, Climate and Man, 1941.

28. Harper, N. G. Morphology and Genesis of Calcisols. Soil Sci. Soc.

29. Ray, R. L. Oirgin and Weathering of Late Pleistocene Ash Deposits
on St. Vincent, B.W.I. Jour. Geol. 67:65—87, 1959.

182

30. Hill, R. T. Notes on the Texas-New Mexico Region. Bull. Geol. Soc.
Amer. 3:85-100, 1891.

31. Hosking, J. S. The Soil Clay Mineralogy of Some Australian Soils
Developed on Granitic and Basaltic Parent Material. Austra-

32. Rough, G. J., and Byers, H. G. Chemical and Physical Studies of
Certain Hawaiian Profiles. U.S.D.A. Tech. Bull. No. 584, 1937.

33. Gile, P. L., and Foster, Z. C. Rock Weathering and Soil
Profile DevelOpment in the Hawaiian Islands. U.S.D.A. Tech.
Bull. No. 752, 1941.

34. Humbert, R. P., and Marshall, C. E. Mineralogical and Chemical
Studies of Soil Formation from.Acid and Basic Igneous Rocks
in Missouri. Mo. Agr. Exp. Sta. Res. Bull. No. 359, 1943.

35. Jackson, M. L., Hseung, Y., Correy, R. B., Evans, E. J., and Vanden
Heuvel, R. C. Weathering Sequence of Clay Size Minerals in
Soils and Sediments. 11 Chemical Weathering of Layer Sili-
cates. Soil Sci. Soc. Amer. Proc. 16:3-6, 1952.

36. and Sherman, G. D. Chemical Weathering of Minerals in
Soils. Norman, A. 0., Ed. Advances in Agronomy. 5:221-309
Academic Press Inc., New York, 1953.

37. Tyler, S. A., Willis, A. L., Bourbeau, G. A., and Pennington,
R. P. Weathering Sequence of Clay Size Minerals in Soils and
Sediments I Fundamental Generalizations. J. Phys. Coll. Chem.
52:1237-1260, 1948.

38. Whittig, L. D., and Pennington, R. P. Segregation Pro-
cedures for the Mineralogical Analysis of Soils. Soil Sci.
Soc. Amer. Proc. 14:77-85, 1949.

39. Jeffries, C. D., and Jackson, M. L. Mineralogical Analysis of Soils.
Soil Sci. 68:57-73, 1949.

40. Judson, S. Depressions of the Northern Portion of the Southern
High Plains of Eastern New Mexico. Bull. Geol. Soc. Amer.
61:253-274, 1950.

41. Kanno, I. A Pedological Investigation of Volcanic Ash Soils. Sixth
lnt. Cong. of Soil Sci. Vol. 2:105-109, 1956. '

42. Rilmer, V. J., and Alexander, L. T. Methods of Making Mechanical
Analyses of Soils. Soil Sci. 68:15-29, 1949.

43. Krumbein, W. C., and Pettijohn, F. J. Manual of Sedimentary Petro-
graphy. Appleton-Century-Crafts, Inc., New York:1938.

183

44. Lee, W. T., and Mertie, J. B., Jr. Geologic Atlas of the United
States. Raton-Brilliant-Koehler Folio No. 214, 1922.

45. Levings, W. S. Late Cenozoic Erosional History of the Raton Mesa
Region. Quart. of the Col. School of Mines. 46:1-111, 1951.

46. Martin, R. T. Ethylene Glycol Retention by Clays. Soil Sci. Soc.
Amer. Proc. 19:160-164, 1955.

47. McAleese, D. M., and McConaghy, S. Studies on the Basaltic Soils of
Northern Ireland. 11 Contributions from the Sand, Silt, and
Clay Separates to Cation-Exchange Properties. Jour. Soil Sci.
8:135-140, 1957.

48. Studies on the Basaltic Soils of Northern
Ireland 111 Eschangeahle-cation Contents of Sand, Silt, and
Clay Separates. Jour. Soil Sci. 9:66-75, 1958.

 

49. and Mitchell, W. A. Studies on the Basaltic Soils of
Northern Ireland IV Mineralogical Study of the Clay Sepa—
rates ( 2 microns) Jour. Soil Sci. 9:76-80, 1958.

50. Studies on the Basaltic Soils of Northern Ireland
V Cation-Exchange Capacities and Mineralogy of the Silt Sepa-
rates (2-20 microns) Jour. Soil Sci. 9:81-88, 1958.

 

51. Studies on the Basaltic Soils of Northern Ireland VI
Cation-Exchange Capacities and Mineralogy of the Fine Sand
Separates Jour. Soil Sci. 9:289-297, 1958.

52.‘McConaghy, 8., and McAleese, D. M. Studies on the Basaltic Soils
of Northern Ireland I Cation-Exchange Preperties Jour.
Soil Sci. 8:127-134, 1957.

53. Mitchell, W. A., and Irmak, A. Turkish Forest Soils. Jour. Soil
Sci. 8:184-192, 1957.

54. Muehlberger, W. R. Relative Age of Folsom Man and the Capulin Mountain
Eruption, Colfax and Union Counties, New Mexico. (Abstract)
Bull. Geol. Soc. Amer. 66:1600-1601, 1956.

55. ' and Baldwin, B. Field Method for Determining Direction of
‘Magnetization as Applied to Late Cenozoic Basalts, Northeastern
New Mexico. Jour. GeOphys. Res. 63:353-360, 1958.

56. Volcanic Rocks of Des Moines Quadrangle. Bull. 63 Part II
N. Mex. Bureau of Mines and Mineral Resources (In Press).

57. Parker, B.R. Clastic Plugs and Dikes of the Cimarron Valley Area
of Union County, New Mexico. Jour. Geol. 41:38-41, 1942.

184

58. Prince, A. L. Appendix: Methods on Soil Analysis. Bear, F. E.,
Ed. Chemistry of the Soil. Reinhold Publ. Co., New York:
1955.

59. Radoslovich, E. W. Clay Mineralogy of Some Australian Red Brown
Earths. Jour. Soil Sci. 9:242-251, 1958.

60. Retzer, J. L. Soils Developed from Basalt in Western Colorado.
Soil Sci. 66:365-375, 1948.

61. Alpine Soils of the Rocky Mountains. Jour. Soil Sci.
7:22-32, 1956.

 

62. Richards, L. A., Ed. Diagnosis and Improvement of Saline and Al-
kali Soils. U.S.D.A. Handbook No. 60, 1954.

63. Rios, E. G., and Garcia, F. G. Genesis de la Montmorillonita de
Marruecon Espanol. Anal. Edaf. 8:537-561, 1949.

64. Ross, C. L., and Shannon, E. V. The Origin, Occurrence, Composi-
tion, and Physical Properties of the Mineral, Iddingsite.
‘Proc. U. 8. Nat. Museum No. 2579, pp. 1-19, 1925.

65. Schmel, W. R. and Jackson, M. L. Mineralogical Analyses of Soil
‘ Clays from Colorado Surface Soils. Soil Sci. Soc. Amer.
Proc. 21:373-380, 1957.

66. Smith, G. D. Illinois Loess: Variation in its Properties and
Distribution. A Pedologic Interpretation Ill. Agr. Exp.
Sta. Bull. 490, 1942.

67. Smith, J. A Mineralogical Study of Weathering and Soil Formation
from Olivine Basalt in Northern Ireland Jour. Soil Sci.
8:225-239, 1957.

68. Smith, J. F. Jr., and Ray, L. L. Geology of the Cimarron Range,
New Mexico. Bull. Geol. Soc. Amer. 54:891-924, 1943.

69. Stearns, H. T. Supplement to the Geology and Ground Water Re-
sources of the Island of Oahu, Hawaii. U.S.G.S. Bull. No. 5.
The Advertiser Publishing Co., Honolulu, Hawaii, 1941.

70. and MacDonald. Geology and Ground Water Resources of the
Island of Maui, Hawaii. U.S.G.S. Bull. N0. 7, The Advertiser
Publishing Co., Honolulu, Hawaii, 1942.

71. Stephen, 1. A.Study of Rock.Weathering with Reference to the Soils
of the Malvern Hills 11 Weathering of Appinite and Ivy Scar
Rook. Jour. Soil Sci. 3:219-237, 1952.

72.

73.

74.

75.

76.

77.

78.

79.

80.

81.

82.

83.

84.

185

Stobbe, H. R. Petrology of Volcanic Rocks in Northeastern New
Mexico. Bull. Geol. Soc. Amer. 60:1041-1095, 1949.

Sudo, T. Mineralogical Study of Clays of Japan. Maruzon Co. Ltd.
Tokyo, 1959.

Sun, M. S. The Nature of Iddingsite in Some Basaltic Rocks of
New Mexico. Am. Mineralogist 42:525-533, 1957.

Swineford, A., Frye, J. C., and Chapman, J. Petrographic Compari-
son of Pliocene and Pleistocene Volcanic Ash from Western
Kansas. Kan. State Geol. Survey Bull. No. 64, 1946.

Tamura, T., Jackson, M. L., and Sherman, G. D. Mineral Content of
Low Humic, Humic and Hydrol Humic Latosols of Hawaii. Soil
Sci. Soc. Amer. Proc. 17:343-346, 1953.

Tiller, K. G. The Geochemistry of Basaltic Materials and Associ-
ated Soils of Southeastern Australia Jour. Soil Sci. 9:225-
241, 1958.

Uehara, G., and Sherman, G. D. The Nature and Properties of the
Soils of the Red and Black Compbx of the Hawaiian Islands.
Hawaii Agric. Exp. Sta. Res. Bull. No. 32, 1956.

U. S. Department of Agriculture Soil Survey Manual, U.S.D.A. Hand-
book No. 18, 1951.

Van der Merwe, C. B., and Heystek, H. Clay Minerals of South African
Soil Groupi. IV Soils of the Temperate Regions. Soil Sci.

81:399-414, 1956.

Webber, L. B., and Shivas, J. A. The Identifbation of Clay Minerals
in Some Ontario Soils: I. Parent Materials, Soil Sci. Soc.,

Amer. Proc. 17:96-99, 1953.

Whiteside, E. P. A Proposed System of Genetic Soil-Horizon Desig-
nations, Soils and Fert., 22:1-8, 1959.

Wilshire, H. G. Alteration of Olivine and Orthopyroxene in Basic
Lavas and Shallow Intrusives. Amer. Mineralogist 43:120-147,

1958.

Wood, G. H., Northrup, S..A., and Griggs, R. L. Geology and Strati-
graphy of Koehler and Mount Laughlin Quadrangles and Parts
of Abbott and Springer Quadrangles, Eastern Colfax County,
New Mexico. Oil and Gas Investigation Map OM 141 (In Two

Sheets) U. S. Geol. Survey, 1953.

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