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thesis entitled

PALEOENVIRONMENTAL STUDY OF THE HELDERBERG
GROUP OF WEST VIRGINIA AND VIRGINIA

presented by

Jack Watson Travis

has been accepted towards fulfillment
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ABSTRACT

PALEOENVIRONMENTAL STUDY OF THE HELDERBERG GROUP
OF WEST VIRGINIA AND VIRGINIA

BY

Jack Watson Travis

The variations of stratigraphic, petrographic, and
paleontologic attributes of the Helderberg Group, Lower
Devonian, of West Virginia and Virginia have been systema-
tically analyzed for meaningful environmental indicators
so that logical inferences concerning conditions of deposi-
tion of Helderberg sediments can be made.

Data have been-derived from a detailed field
study of 22 Helderberg outcrops, from a petrographic study
of 425 randomly and purposely collected rock samples, and
from fossil population studies along 260 sampling lines in
14 outcrops.

In outcrops north of Monterey, Virginia the Coey-
mans Limestone can be subdivided into lower, middle, and
upper limestone members. The middle limestone member is
a thin-bedded, finely crystalline crinoidal limestone with
chert nodules and shows a general thinning from north to

south.

Jack Watson Travis

possibly existed in the Virginias during deposition of New
Scotland sediments and the communities trended northeast-
southwest with the species diversity gradient increasing
from northwest to southeast.

There is a direct relationship between the number
of strOphomenids in a sample and the amount of fine-
grained sediments, in that those sampling sites with a
high proportion of strophomenids generally contain a larger
percentage of fine-grained sediments.

Since the Helderberg Group appears to represent a
transgressive phase of deposition and the various strati—
graphic units are rock-stratigraphic units, a stratigraphic
unit overlying another unit in a Helderberg outcrop grades
laterally into a subjacent or superjacent unit. This indi-
cates that the sediments of the various rock-stratigraphic
units were deposited simultaneously under differing envir-
onmental conditions in different parts of the depositional
basin.

The occurrence of mud cracks in some micritic beds
of the upper Keyser Limestone suggests that deposition
occurred in a supratidal, mud-flat environment. These
sedimentary structures also can serve as references in
reconstructing the environmental gradient.

Stratigraphic and petrographic evidence suggest
that the Coeymans Limestone and the crinoidal limestone
and sandstone faciesLof the New Scotland Formation were

deposited in a high energy beach environment. However,

Jack Watson Travis

Overall the Helderberg Group represents a trans-
gressive phase of deposition during early Devonian time in
West Virginia and Virginia and the formations comprising
the Helderberg Group are rock-stratigraphic units rather
than time-stratigraphic units.

Based on the type of grain support and the propor-
tion of grains, matrix, and cement the following rock types
can be recognized in the Helderberg Groups: micrite, bio-
micritic wackestone, biomicritic packstone, biosparitic
packstone, biosparitic grainstone, pelsparitic grainstone,
and intrasparitic grainstone. Most of the sparry calcite
occurring in the packstone and grainstone is a primary
pore filling cement. However, microsparry calcite repre-
sents recrystallized grains of microcrystalline calcite.
Chert, which is common in the New Scotland Formation,
appears to be a replacement phenomenon.

A chi-square test for independence identifies 33
interspecific fossil associations which involve 10 of
the 34 fossil species identified in the field. These
associations can be grouped into a primary recurrent group
and a related secondary recurrent group. All species,
with the exception of g. strictum, which is associated
with another species, have a positive association with
limestone and all species have a negative association with
chert.

The spatial distribution of the computed indices

of species diversity suggests that three fossil communities

Jack Watson Travis

sediments of the limestone and chert facies of the New
Scotland Formation and the Shriver Chert-Licking Creek
Limestone interval were deposited in an open marine envir-

onment probably below wave base.

PALEOENVIRONMENTAL STUDY OF THE HELDERBERG GROUP

OF WEST VIRGINIA AND VIRGINIA

BY

Jack Watson Travis

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Geology

1971

PLEASE NOTE:

Some Pages have indistinct
print. Filmed as received.

UNIVERSITY MICROFILMS

n‘

L.

"A
“U

.1.)
l 4
(T)

ACKNOWLEDGMENTS

The author wishes to express appreciation to Dr.
Chilton E. Prouty for guiding this research project; to
Dr. Robert Ehrlich for many discussions concerning the
use of statistics for solving geological problems; to
Dr. Jane E. Smith, Dr. Harold B. Stonehouse, and Dr. James
H. Fisher for offering time to discuss various aspects of
this investigation. The author is also indebted to these
individuals for their reading this report and offering
constructive suggestions.

Gratitude is also expressed to Dr. Frank M. Swartz,
Professor Emeritus, the Pennsylvania State University; Dr.
Alan C. Donaldson, Department of Geology, West Virginia
University; and Dr. John M. Dennison, Department of Geology,
University of North Carolina for some enlightening discus-
sions concerning various aspects of the Helderberg Group.

The writer owes thanks to the following fellow
graduate students at Michigan State University: Dr. Donald
Merritt and Dr. Donald Hill for assistance in computer
programming and to Carlton Babb for verifying the techni-
que for determining fossil recurrent groups in the New

Scotland Formation.

ii

Field work was partially supported through a grants-
in-aid from the Society of the Sigma Xi. Partial financial
support for thin sections was provided by the Department of
Geology, Michigan State University. Both means of finan-
cial assistance are gratefully acknowledged.

Finally, the author is especially indebted to his
wife, Patricia, for her constant, but pleasant, encourage-

ment during all phases of this investigation.

iii

TABLE OF CONTENTS

Page
ACKNOWLEDGMENTS . . . . . . . . . . . . . . ii
LIST OF TABLES . . . . . . . . . . . . . . vi
LIST OF FIGURES . . . . . . . . . . . . . . vii

LIST OF PIIATES o o o o o o o o o o o o o 0 ix

Chapter
I 0 INTRODUCTION 0 O O O O O O O O O O O 1
Location of Study Area . . . . . . . 3
General Stratigraphy . . . . . . . . 4
II 0 STMTIGWHY . O O O O O O O O O O O 7
Previous Investigations . . . . . . 7
Stratigraphy of the Helderberg Group
in Virginia and West Virginia . . . . 10
Coeymans Limestone . . . . . . . 12
New Scotland Formation . . . . . . 15
Construction of Stratigraphic
Cross-Sections . . . . . . . . 22
Interpretation of Stratigraphic
CIOSS'SeCtiODS o o o o o o o o o 28
III. PETROGRAPHY AND PETROLOGY . . . . . . . 36

Method of Study . . . . . . . . 37
Petrographic Aspects of the

Helderberg Group . . . . . . . . 38
Mineralogical Composition . . . . . 39
Textural Components . . . . . . . 47

Origin of Helderberg Rock Types . . . . 67
Origin of Rock Components . . . . . 67
Origin of Helderberg Cherts . . . . 73

iv

Chapter

Origin and Environmental Signifi-

cance of the Helderberg
Types . . . . . .

IV. PALEONTOLOGY . . . . . . .
V. PALEOSYNECOLOGY . . . . . .

Method of Determining Species
Associations . . . . .
Method of Sampling . . .
Method of Analysis . . .
Results of the Analysis . .
Recurrent Groups . . . .

Analysis of Species-Lithology
Associations . . . . .
Species Diversity . . . .
Species Diversity Map .
Results . . . . . .

Environmental Significance

VI. PALEOENVIRONMENTAL SYNTHESIS .
VII. CONCLUSIONS . . . . . . .
VIII. SUGGESTIONS FOR FURTHER RESEARCH

BI BLIOGWHY . O O O O O O O O C

APPENDICES O O O O O O O O O O

A. O O O O O O O O O 0

Rock

Page

76
82
84
85
87
94
96
98
101
105
106
107
110
121
131
135
136
147

148

LIST OF TABLES

Table Page
1. Helderberg Fossils . . . . . . . . . . 83
2. New Scotland species combinations showing

positive associations . . . . . . . 97

3. Affinity between pairs of New Scotland

fossil species . . . . . . . . . . 99
4. Percent occurrence of New Scotland fossils . . 109
5. Relationship between the amount of lime

mud and the index of species diversity
in the New Scotland Formation . . . . . 116

6. Relationship between the amount of lime

mud and the brachiopod ratio in the
New Scotland Formation . . . . . . . 118

Vi

Figure

l.

10.

11.
12.

13.

LIST OF FIGURES

Outcrop map of the Helderberg Group
in West Virginia and Virginia .

Generalized columnar section of the
Helderberg Group . . . . .

Historical summary of the Silurian-
Devonian boundary . . . . .

Stratigraphic interpretation of
Helderberg Group . . . . .

Arrangement of crinoidal lenses in
Coeymans Limestone . . . .

Stratigraphic cross-section of
Helderberg Group . . . . .

Stratigraphic cross-section of
Helderberg Group . . . . .

Stratigraphic cross-section of
Helderberg Group . . . . .

Stratigraphic cross-section of
Helderberg Group . . . . .

Stratigraphic cross-section of
Helderberg Group . . . . .

Hypothetical transgressive-regressive cycle

Hypothetical random sampling point on

gently dipping strata . . .

Species-Length of line curve . .

vii

Page

11

15

23

24

25

26

27

31

88
93

Figure Page

14. Species associations in the New
Scotland Formation . . . . . . . . 102

15. Species diversity map of the New

Scotland Formation . . . . . . . . 108
16. Percent fossil fragmentation or disarti-

culation versus index of species

diversity . . . . . . . . . . . 112
17. Percent microcrystalline calcite and

microsparry calcite versus ratio
of spirifers and orthids to
strophomenids . . . . . . . . . . 119

18. Vertical variation of rock components in
the Helderberg Group . . . . . . . . 123

19. Lateral variation of rock components in
the Helderberg Group . . . . . . . . 125

20. Interpretation of depositional environments

of the Helderberg Group in Virginia and
west Virginia 0 O O C O C C O O O 130

viii

LIST OF PLATES

Plate Page

1. Figure A. Laminated micrite . . . . . . . . 53
Figure B. Bioturbated micrite . . . . . . . . 53

2. Figure A. Biomicritic wackestone . . . . . . . 56
Figure B. Bioturbated biomicritic wackestone . . . 56

3. Figure A. Biomicritic packstone . . . . . . . 60
Figure B. Biosparitic grainstone . . . . . . . 60

4. Figure A. Pelsparitic grainstone and layers

of micrite . . . . . . . . . . 63
Figure B. Pelsparitic grainstone . . . . . . . 63

ix

CHAPTER I

INTRODUCTION

Rocks in the Appalachian region have been studied
extensively and are generally considered to typify most
of the Paleozoic systems recognized in North America.
Much of the research conducted on this sequence of rocks
has been concerned with their stratigraphic, structural,
and paleontological aspects resulting in their being sub-
divided into numerous stratigraphic units. More recently
the emphasis in some Appalachian studies has been con-
cerned with gathering information and interpreting data
relative to paleoenvironments of some of these strata.1

The Lower Devonian Helderberg Group is a strati-
graphic unit in the Appalachians which is amenable to the
latter type of study. It is a lithologically diverse rock
unit consisting of limestone, chert, sandstone, and shale.

Many Helderberg outcrops have been measured, described,

and subdivided by previous investigators. In the course

 

1Some of the recent paleoenvironmental studies in
the Appalachians are Pelletier, 1958; Donaldson, 1960;
Folk, 1960; Alling and Briggs, 1961; Yeakel, 1962; Weber
and others, 1965; Matter, 1967; Johnson and Friedman, 1969;
Laporte, 1969; and Bretsky, 1970.

of such studies several facies have been recognized.
Stratigraphic relationships and equivalencies have been
generally established between various outcrops and type
sections. Few previous investigations have dealt with
the petrographic and paleoecologic aspects of these rocks
even though the occurrence of different lithologies sug:
gest that more than one type of environment prevailed at
any given time during deposition of Helderberg sediments.

The purpose of this investigation is to systemati-
cally analyze variations of stratigraphic, petrographic,
and paleontologic attributes of the Helderberg Group for
meaningful environmental indicators and to make logical
inferences from these analyses concerning environmental
conditions during deposition of these sediments in the
central Appalachians.

Composition, texture, sedimentary structures, and
fossil content are all possible indicators of a given
sedimentary environment. But certain diagenetic processes
can produce compositions or textures which are character-
istic of entirely different environmental conditions.
Also the observable fossil content probably is not a true
representation of the total suite of organisms that were
indigenous to the site of deposition due to postmortem
transport of skeletal material, non-preservation, or
(dbliteration of head parts by diagenetic processes.

Since the original lithologic and paleontologic

character of a local sedimentary deposit is a product of

its depositional environment, it can be said that areal
variations of the lithology and paleontology of a strati-
graphic unit in a given time interval represent different
local depositional environments within a basin of sedimen-
tation. Lateral shifts in facies with time point to
corresponding changes in the depositional environments of
a given area.

It is, therefore, important to look for indicators
of the original environments and evaluate their temporal
and spatial distributions before depositional conditions

can be inferred for the Helderberg Group.

Location of Study Area

Outcrops of Lower Devonian rocks occur mainly in
the Ridge and Valley physiographic province between the
Blue Ridge Mountains and their continuations to the east
and the Allegheny Front on the west. Helderberg outcrops
are practically continuous from the Hudson River in New
York to the southwest corner of Virginia. The best expo-
sures are restricted to road cuts, railroad cuts, quarries,
and occasional stream beds.

This study is restricted to Helderberg outcrops of
jparts of West Virginia and Virginia. In this area the
.Helderberg Group displays several facies and a number of
available outcrops contain various portions of these
facies so their areal and temporal distributions can be
:studied. The northern extent of the study is along a line

running from New Creek, Mineral County, West Virginia

through Romney, Hampshire County, West Virginia. The
southern-most Helderberg exposure investigated is in the
vicinity of Bluefield, Virginia. The distribution of
Helderberg rocks and outcrops which were studied are

shown in Figure 1.

General Stratigraphy

The Devonian System has been divided into the
Ulsterian, Erian, Senecan, Chautauquan and Bradfordian
Series by Cooper and others (1942). They further sub-
divided the Ulsterian Series into the Helderberg, Deer-
. park, and Onesquethaw Stages. The Helderberg Stage was
to include the Helderberg Group and its correlatives.

A generalized columnar section of the Devonian
System is presented in Figure 2 to show the relative
stratigraphic position of the Helderberg Group in West

Virginia and Virginia.

 

 

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Group.

CHAPTER II

STRATIGRAPHY

This section of the report is primarily concerned
with evaluating previous stratigraphic studies of the
Helderberg units and re-evaluating the vertical and lateral
relationships of lithologic units of the Coeymans Lime-

stone and New Scotland Formation in the study area.

Previous Investigations

Many stratigraphic studies have been conducted on
Helderberg rocks since Conrad (1839) designated an inter-
val of rocks in New York as the Helderberg limestones and
sandstones. Today these presumably include the interval
from the base of the New Scotland Formation through the
Schoharie Grit and possibly the Onondaga Limestone (Berdan,
1964).

Berdan (1967) has summarized the geological reason-
ing and conclusions of various stratigraphers concerning
the Helderberg Group and the position of the Silurian—
Devonian boundary in North America, from Conrad's work
through that of Rickard (1962). Figure 3 summarizes these

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Some of these investigations have been concerned
with redefining the Helderberg interval and determining
the age of the Helderberg formations. Clarke and Schuchert
(1899) subdivided the Helderbergian interval as designated
by Hall (1859) into the Coeymans Limestone, New Scotland
Formation, Becraft Limestone, and Kingstone Limestone
(Alsen and Port Ewen limestones of modern usage). Later,
Chadwick (1908) suggested the terms Kalkberg Limestone and
Port Jervis Limestone for beds between the Coeymans Lime-
stone and New Scotland Formation and above the Port Ewen
Limestone respectively. Some investigators (Hall, 1859
and Williams, 1900) have considered the Helderberg as
Silurian, others have considered the Helderberg as
Devonian (Clarke, 1889; Clarke and Schuchert, 1899; Weller,
1900 and 1903; Schuchert, 1900 and 1903; Ulrich, 1911;
Stose and Swartz, 1912; Schuchert and others, 1913;

Swartz, 1929 and 1939; Butts, 1940; Cooper and others,
1942; Woodward, 1943; Rickard, 1962; Bowen, 1967; Boucot
and Johnson, 1967).

'Other stratigraphic studies have been concerned
primarily with recognizing lateral equivalents of the
Helderberg Group of New York in other regions. Schuchert
(1903) correlated an interval of rocks in Maryland and
VWest Virginia with New York Helderberg formations based
cu: stratigraphic position and similarity of faunal content.
Swartz (1929) correlated Helderberg outcrops throughout

\kirginia and West Virginia and was able to demonstrate

10

facies changes occurring within the Helderberg Group,
especially a sandstone facies in the southwestern outcrops.
Later Swartz (1939) correlated Helderberg outcrops through-
out Pennsylvania and was again able to show some facies
changes; for example, Stormville (Elbow Ridge) Sandstone-
Coeymans Limestone, Falling Springs Sandstone-New Scot-
land Formation, Mandata Shale-New Scotland Formation, and
Licking Creek Linestone-Shriver Chert. Recently Epstein
and others (1967) have re-evaluated correlations of the
Helderberg Group from New York through New Jersey to
eastern Pennsylvania.

Prior to 1962 most investigators have considered
the Helderberg formations to represent time-stratigraphic
units (see Figure 4a). For example, Cooper and others
(1942) elevated the Helderberg Group to a stage rank
(Helderberg Stage) with the type section in the Helderberg
Mountains of New York. From detailed stratigraphic stu-
dies of Rondout Formation, Manlius Limestone, and Helder-
berg formation outcrops in New York, Rickard (1962) has
been able to show that these formations are rock-strati—
graphic units rather than time-stratigraphic units because
they transgress time lines and interfinger laterally with
(one another (see Figure 4b).

Stratigraphy of the Helderberg Group
in Virginia and West Virginia
The following formations comprise the Helderberg

Group in the study area: (1) Keyser Limestone (at least

 

 

 

 

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Dk
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Figure 4a.

West
r

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Figure 4b.

Figure 4.--Stratigraphic interpretation of Helderberg Group.
Figure 4a represents a time-stratigraphic inter-
pretation for the Helderberg Group prior to 1962.
Figure 4b shows a rock-stratigraphic interpreta—

 

11

 

 

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tion for the Helderberg Group since 1962.
Rickard, 1962 and Laporte, 1969).

 

 

 

12

the upper part, based on the results of a paleontological
investigation by Bowen, 1967); (2) Coeymans Limestone;

(3) New Scotland Formation--Healing Springs Sandstone; and
(4) Shriver Chert-Licking Creek Limestone (Port Ewen Chert
and Port Jervis Limestone as employed by the West Virginia
Geological Survey). However, this study is primarily con-
cerned with the Coeymans Limestone and the New Scotland

Formation.

Coeymans Limestone

Generally speaking, the Coeymans Limestone is a
massive, coarsely crystalline, crinoidal limestone charac-
terized by Gypidula coeymanensis. Schuchert (1903) corre-
lated the presently recognized Coeymans Limestone of Mary-
land with that of New York primarily on similarities of
lithology and the presence of G. coeymanensis.

Recently, Bowen (1967) presented some arguments
for changing the name of the Coeymans Limestone of Mary-
land and adjacent areas to New Creek Limestone. His reasons
for proposing a new formational name are (1) the unit can
not be traced entirely to the type area because of many
complex facies changes and unconformities, and (2) the
fossils must be re-examined because they have not been
studied in 50 years.

This investigator does not believe that a name
cahange is justifiable because the name, Coeymans Limestone,

is Well established in the geological literature for a

13

given formation in the central Appalachians as well as in
the vicinity of the type area.

In a vertical sequence the Coeymans stratigraphi-
cally overlies the Keyser Limestone. In most outcrops
studied the Keyser-Coeymans contact is lithologically dis-
tinct but in some outcrops (Trinity Road, Thrasher Springs
School, Bull Pasture Mountain, Gala, Island Ford, and Blue-
field sections) a gradational contact is present. In most
outcrops the Keyser beds adjacent to the contact are thin-
bedded, fine-grained, silty or dolomitic limestones.
Fragments of the underlying Keyser beds were observed in
the basal beds of the Coeymans Limestone at New Creek I
and New Creek II sections.

In outcrops north of Monterey, Virginia the Coey-
mans Limestone can be subdivided into three members: (1)

a lower limestone member which is a massive—bedded,
coarsely crystalline, crinoidal limestone containing

G. coeymanensis; (2) a middle limestone member which is

a thin-bedded, finely crystalline, crinoidal limestone
with chert nodules and lenses containing G. coeymanensis
in the basal beds only; and (3) an upper limestone member
which is a massive-bedded, coarsely crystalline, crinoidal
limestone containing G. coeymanensis.

Overall there is an increase in size of pelmatozoan
stem debris from north to south and from west to east. The
average diameter of the stems in the northwestern outcrops

.iS 1/4 inch; whereas, in the southeastern outcrops it is

14

3/4 inch. Also, the average diameter of the stems is
larger in the lower limestone member than the upper member.
Poor to well developed cross-bedding occurs in the
lower and upper limestone members but it is better devel-
oped in the lower member. The cross-bedding is best
developed in accumulations of stem fragments where the
stems have a larger diameter. These accumulations of
stem fragments are lens shaped and are surrounded by finer
grained crystalline limestone. One lens of pelmatozoan
debris is generally situated adjacent to two other lenses
and above the finer grained crystalline limestone occupy-
ing the area between the lower lenses. The arrangement
of the lenses develops somewhat of a diagonal pattern to
the bedding (see Figure 5). The cross-bedding displays
two general trends, southeast and northwest. However,
there does not appear to be any preferred orientation of
the long axis of the pelmatozoan stems. Generally arti—

culated shells of G. coeymanensis are associated with the

 

crinoidal lenses and disarticulated shells of the species
occur in the interareas between lenses. The cross-bedding,
lens-shaped accumulations of pelmatozoan stems and distri-
bution of articulated and disarticulated shells of Q.
coeymanensis are best developed in the Thrasher Spring
School section.

The middle limestone member is a thin-bedded, fine
grained limestone. Lenses of black chert parallel to the

Ixadding occur randomly throughout this unit. G. coeymanensis

15

 

 

 

 

Figure 5.--Arrangement of crinoidal lenses in Coeymans
Limestone. The thicker limestone symbol
represents the coarser pelmatozoan debris.
Scale: 1 inch represents 2 feet.

was observed only in the basal beds of the member. This
member shows a general thinning from north to south, even
though two adjacent outcrops might show local thickening
or thinning. The member is not present in the Island Ford
or Gala sections. It is not possible to determine if the

member is present in the faulted Millboro Springs section.

New Scotland Formation
Based on fossil content and stratigraphic position

Swartz (1929 and 1939), Butts (1940), and Woodward (1943)

16

have suggested that four facies or members2 comprise the
New Scotland Formation in the study area. Regionally
there are four facies (l) crinoidal sandstone (Healing
Springs Sandstone) which occurs in the southern most out-
crops of the New Scotland interval in Virginia and West
Virginia, (2) crinoidal limestone which occurs between the
crinoidal Coeymans Limestone and Licking Creek Limestone
in the vicinity of Fordwick, Augusta County, Virginia,

(3) limestone and chert beds, and (4) calcareous shale
(Mandata Shale). The third and fourth facies occur in
the northern most outcrops of the study area with the
calcareous shale facies overlying the limestone and chert
facies.

In this study each of these lithologic units is
interpreted as a facies of the New Scotland Formation.
Three of the units may be demonstrated at the Millboro
Springs section. This section displays beds typical of
the crinoidal sandstone, crinoidal limestone, and lime—
stone and chert facies interbedded. The contact between
one lithologic type and another is gradational. Also,
crinoidal limestone beds interbedded with limestone and
chert beds at the Bull Pasture Mountain section possibly

indicate that the crinoidal limestone facies comprises

 

2Swartz considered each entity as a facies of the
New Scotland Formation; whereas, Woodward only recognized
the crinoidal limestone and sandstone beds as facies of
the New Scotland. Butts considered each entity as a
member.

17

part of the New Scotland Formation. In the northermost

 

outcrops of the study area the limestone and chert beds
generally become more argillaceous toward the top of the
interval and then grade upward into a calcareous shale.
These observations suggest that the calcareous shale unit
is also a facies of the New Scotland Formation.

The limestone and chert facies, crinoidal lime-

stone facies, and crinoidal sandstone facies of the New

 

Scotland Formation in their respective locations are
stratigraphically above the Coeyman Limestone. The Coey-
mans-New Scotland contact is gradational and all outcrops
studied in this investigation.

The spiriferid brachiopod, Macrgpleura macropleura,
has been considered as the "index fossil" for the New
Scotland Formation. Schuchert (1903) correlated the
presently recognized New Scotland Formation of Maryland
with the type section of New York, primarily on strati-
graphic position and the presence of M. macrgpleura. M.

macropleura is fairly abundant in the limestone and chert

 

facies outcrops but is rare in outcrops of the crinoidal
limestone facies. During this study no occurrence of M.

macropleura was observed in any of the crinoidal sandstone

 

or calcareous shale facies outcrops in the study area.
Swartz (1929 and 1939) indicates that fragments of M.
Inacropleura occur in the crinoidal sandstone facies in
the vicinity of Healing Springs, Virginia and in the cal-

careous shale facies in central Pennsylvania.

18

Crinoidal Sandstone Facies

The crinoidal sandstone facies of the New Scotland
Formation has been designated as the Healing Springs Sand-
stone by Swartz (1929) with the type section in the vici-
nity of Healing Springs, Virginia. The facies occurs in
the southern most outcrops (Bluefield, Gala, Island Ford,
Howards Creek, and Healing Springs sections) of the study
area.

This facies is predominantly a cross-bedded, cal-
careous sandstone. The sandstone beds in the lower portion
of the Healing Springs Sandstone (as displayed in the Gala
and Island Ford sections) are generally lens-shaped and
interbedded with thin beds of shale which are generally
thicker between lenses of sandstone. The sandstone beds
in the upper portion of the interval are also cross-bedded
but the bedding is massive and several conglomeratic beds
are present. With the exception of imprints of crinoid
stems on the bedding planes and an occasional calyx of
Edriocrinus pocilliformis, fossils are rare in the Healing

Springs Sandstone.

Crinoidal Limestone Facies

The crinoidal limestone facies of the New Scotland
.Formation which occurs in the vicinity of Fordwick, Vir-
ginia is very difficult to distinguish from the underlying
(Joeymans Limestone. The contact was arbitrarily placed at
‘the base of the crinoidal limestone bed containing the

lcwwast observed specimen of M. macropleura. With the

19

exception of an abundance of pelmatozoan fragments, fossils
are rare in this interval. Though disarticulated ossicles
of pelmatozoan stems are scattered throughout the interval
the mass of the unit consists primarily of fine, sand-
sized prismatic crystals of calcite which probably are

disarticulated plates and ossicle prisms of pelmatozoans.

Limestone and Chert Facies

The limestone and chert facies is characteristic of
the northern-most outcrops of the study area. A vertical
sequence from bottom to top in any of the limestone and
chert facies outcrops is generally as follows: (1) coarse
to very fine-grained, fossiliferous limestone and chert
lenses without M. macropleura; (2) thick- to medium-bedded,
very fine-grained, fossiliferous limestone containing M.

macropleura and irregular-bottomed chert lenses; (3)

 

medium— to thin-bedded, very fine-grained, fossiliferous,
argillaceous limestone containing M. macropleura and irreg-
ular-bottomed chert lenses interbedded with thin shale

beds; (4) thin-bedded, fossiliferous, argillaceous lime-
stone containing M. macropleura and irregular-bottomed
<3hert lenses interbedded with thin shale beds; and (5) thin-
.bedded, fossiliferous, argillaceous limestone with M.

Inacropleura restricted to the basal layers if present and

 

.irregular-bottomed chert lenses interbedded with thin
shale beds.
The thickness of the limestone and chert facies

\nxries from 21.5 feet at the Thrasher Spring School section

20

to 32.5 feet at Petersburg Gap section. The observed
thickness of the facies at Thrasher Spring School section
is somewhat low as surrounding outcrops display thicknesses
of 25 feet or greater for the interval in question. There
is no evidence of faulting in the facies at Thrasher Spring
School section to account for the thinning of the facies.

A gradational contact occurs in all limestone and
chert facies outcrops in the study area between the facies
and the underlying Coeymans Limestone. The contact inter-
val shows a textural gradation from coarse grained lime-
stone beds at the bottom to very fine grained limestone
beds at the top. Lenses of white chert occur parallel to
the bedding. Neither G. coeymanensis nor M. macropleura
was observed in the gradational zone at any of the out-
crops studied.

Occasional lenses of crinoidal limestone showing
textural similarities with that of the underlying Coeymans
Limestone occur in the basal portions of the limestone
and chert facies. These are best developed in the Bull
Pasture Mountain section. In this section one crinoidal
limestone bed also occurs above the lowest limestone bed
containing M. macropleura.

Within the limestone and chert facies at Smoke
Hole Cavern section nineteen asymmetrical sedimentary cycles
are well develOped and plainly visible in the exposed por-
tions of the section. Each cycle consists of the follow-

ing lithologic units from bottom to top: (1) very

 

 

 

21

fine-grained argillaceous limestone with a low fossil
density; (3) very fine-grained cherty limestone with a
very low fossil density; and (4) irregular-bottomed white

chert lens or layer.

Calcareous Shale Facies
Swartz (1939) designated a unit of siliceous shale

beds occurring between the New Scotland Formation and the

 

Shriver Chert in the vicinity of Mandata, Northumberland 9.
County, Pennsylvania as the Mandata Shale. He considered 1
the lower portion of the unit to be a facies of New Scot-
land age, based on the occurrence of M. macropleura, and
the upper portion to be post-Becraft in age. He was also
able to trace the Mandata Shale throughout most of the
Helderberg outcrops of Pennsylvania and into the vicinity
of Cumberland, Maryland.
Woodward (1943) recognized shaly beds lying between
the New Scotland limestone and chert beds and the Shriver
(Port Ewen) Chert but had reservations for applying the
term Mandata Shale to these beds. He considered the shaly
beds as an upper member of the New Scotland Formation.
In most outcrops of the study area a calcareous
shale unit occurs between the limestone and chert facies
of the New Scotland Formation and Shriver Chert (Port Ewen
Chert). This shale unit is considered as a facies of the
New Scotland Formation and probably correlates with the
Mandata Shale which occupies the same stratigraphic posi-

tion in central Pennsylvania.

22

The shale is thickest in the northern outcrops
(18 and 33 feet thick at New Creek I and Rocks sections
respectively) of the study area and thins southward (1.5
feet at Monterey). The contacts between the shale and
the underlying limestone and chert beds of the New Scot-
land Formation and the overlying beds of the Shriver Chert
are generally gradational. The lower and upper contacts
of the shale unit were arbitrarily placed at the uppermost
white chert horizon and the lowermost black chert horizon
respectively.

Throughout the study area the shale is olive green
on fresh surface. Also, the shale is calcareous and breaks
with a fissile to hackly parting. In some of the northern
outcrops phosphatic nodules occur one to two feet above
the base of the shale but in southern outcrops lenses of
coquinal limestone consisting primarily of fragments of

Anoplotheca concava occur in the shale unit.

Construction of Stratigraphic Cross-Sections

The stratigraphic horizon which appears to repre-
sent the most plausible time plane for this study occurs
.at the midinterval of the middle limestone member of the
Coeymans Limestone. Five stratigraphic cross-sections
‘were drawn using this stratigraphic horizon as the datum
jplane so vertical and lateral relationships of Coeymans
and.New Scotland lithologic units can be evaluated (see
Figures 6, 7, 8, 9, and 10). Three cross-sections were

drawn essentially parallel to the trend of the depositional

23

 

 

FIGURE 6

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SIIATIGRAPHIC CROSS-SECTION OF HELDERBERG GROUP

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24

 

 

 

 

 

 

 

 

 

 

 

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25

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FIGURE 8
:
STRATIGRAPHIC CROSS-SECTION OF HELDERBERG GROUP "—
2
I
43., MONTEREY :
roaowlcx :
‘L BULL PASTURE /:
MOUNTAIN // -—I
I» // :I
// __
// __
v // ’—1
g/fl :
// ~——
31' NELSON // t:
aocxs /// F
If / I——‘
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an — —— r-—-I
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PLANE ___ _. , " —- ‘\ \
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4. )—— ——
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31.

 

 

26

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FIGURE 9
STRATIGRAPHIC CROSS-SECTION OF HELDERBERG GROUP
3*” NEW CREEK ROCKS
n
m
.. a
1
HI I
I
10+ [
7
-
-
w =
-
-
-
-
«r !
DATUM :
PLANE ;
~ :
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MIIOSrL V v v v 1 fi 1 r 1 “I 1 Y ' J‘

 

 

27

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FIGURE 10
STRATIGRAPHIC CROSS-SECTION OF HELDERBERG GROUP
.9
“00‘s TRINITY ROAD
\ THRASHER spamcs
0 SCHOOL
= t:
= = b
= = F:
= =
= = Z
13..
0T
‘4»
DATUM
PLANE
'——1
:
I:
.——J
[350!
miles:

 

 

28

basin as recognized by Woodward (1943) and the others were
drawn more or less perpendicular to the trend of the basin.

(See Figure l for the location of the five cross sections).

Interpretation of Stratigraphic Cross-Sections

 

The validity of any conclusions regarding the
vertical and lateral relationships of Coeymans and New
Scotland lithologic units recognized in the study area is
dependent upon two assumptions. The first one is that the
datum plane used in the construction of the stratigraphic
cross-sections actually represent a time plane. Secondly,
we assume that any changes in the geometry of the basin
floor were not tectonically controlled during deposition
of sediments overlying that time plane.

The choice of a datum plane within the middle
limestone member of the Coeymans Limestone is based on
(1) the repetition of coarsely crystalline, cross-bedded,
crinoidal limestone beds in the Coeymans interval; (2)
the regional variation of thickness of the middle member;
and (3) the vertical distribution of G. coeymanensis
within the Coeymans Limestone.

The repetition of the coarsely crystalline, cross-
bedded, crinoidal limestone beds of the Coeymans could
have resulted from a minor regressive phase of deposition
superimposed on the overall transgressive conditions of
deposition. Then the finer grained, thin-bedded limestone

beds of the middle member would represent a deeper water

29

facies of the transgressive and regressive phases of
deposition.

The general thinning of the middle limestone member
from north to south could have resulted from erosion or
nondeposition in the southeastern portion of the study
area, or from transgressive and regressive phases of
deposition of Coeymans sediments superimposed on an over-
all transgressive mode of deposition of Helderberg sedi-
ments. If the thinning resulted from erosion or nondeposi-
tion one would expect to find some evidence of this, such
as fragments of the underlying beds encased in the over-
lying beds or discordant relationships of the beds. How-
ever, no evidence to support this hypothesis appears in
any of the outcrops where the three members occur. The
contacts between the middle limestone member and the lower
or upper limestone members are gradational and lack frag-
ments of the underlying beds. Also, the beds within the
middle limestone member are essentially parallel.

Previous investigators (Swartz, 1929; Butts, 1940;
and Woodward, 1943) have considered G. coeymanensis as an
"index fossil" of the Coeymans Limestone. As mentioned

previously, G. coeymanensis is more or less restricted to

 

the coarsely crystalline, crinoidal lower and upper lime-
stone members of the formation in the study area. This
distribution suggests that G. coeymanensis is a facies
fossil which preferred a coarse pelmatozoan debris substra-

tum when it was alive. Also, since G. coeymanensis is more

 

30

or less restricted to the lower and upper members this
again suggests transgressive and regressive phases of
deposition for Coeymans sediments.

As regional thinning of the middle limestone mem-
ber, repetition of coarsely crystalline limestone units,

and distribution of G. coeymanensis are suggestive of

 

transgressive and regressive phases of deposition for
Coeymans sediments, sediments of the lower and upper halves
of the middle limestone member probably represent syn-
chronous deposition with sediments of the respective lower

transgressive and upper regressive limestone members.

Izraelsky (1949) has demonstrated that inherent
time planes occur in transgressive-regressive cycles (see
Figure 11). Barring tectonic complications, the time
lines coincide with lines passing through points corres-
ponding to maximum depths of deposition for each unit of
the transgressive-regressive cycle (Izraelsky, 1949).
Thus, if the lower, middle, and upper members of the
Coeymans Limestone represent a transgressive-regressive
cycle, then the sediments of the middle member probably
were deposited in somewhat deeper water.

Based on the above lines of evidence and the
absence of any evidence for tectonic complications occur-
ring within the Coeymans Limestone interval in the study
area the likelihood that the boundary between the lower
and upper halves of the middle limestone member at each

outcrop represents a time plane is high. Therefore, the

 

Nonmarine

/
/

I
I

  

I
poi

\\\\\\\\\‘

C

        

 

 

 

 

 

 

 

 

Figure ll.--Hypothetical transgressive-regressive cycle.
A,B,C,D,E,F, and G represents hypothetical
stratigraphic sections. Zones I, II, III, IV,
and V represent brachish water, beach, shallow
neritic, deep neritic, and bathyal environments
respectively. (After Izraelsky, 1949).

assumption that the datum plane corresponds to a time plane
probably is a valid one.

There are no other obvious stratigraphic horizons
in each outcrop of the Coeymans or New Scotland formations
which can be used as subordinate datum planes which corres-
pond to time planes. Therefore, it is also necessary to
assume that tectonic deformations did not alter the geome-
try of the basin floor significantly during deposition of
the sediments comprising these formations so the lateral
and vertical relationships of the various lithologic units

involved can be evaluated.

32

Admittedly, the occurrences of a crinoidal bearing
quartzose sandstone facies and a calcareous shale facies
in an otherwise non-detrital interval suggest that some
tectonic activity occurred during deposition of Helderberg
sediments in the study area. Dennison (1961) believes
that the source area for the detrital material of Cayugan,
Helderbergian, and Deerparkian sandstones resulted from
tectonic activity during post-Clinton and pre-Oriskany
times in the vicinity of Smyth and Washington counties,
Virginia. According to Swartz (1939) the source area for
the detrital material comprising the Madata Shale probably
ranged from eastern Pennsylvania to Massanutten Mountain,
Virginia.

However, it is questionable if the tectonic acti-
vity which possibly accounted for the detrital fraction
of the Helderberg Group affected the geometry of the basin
floor because there are no other tectonic structural attri-
butes in any of the Helderberg outcrops of the study area.
Field relationships suggest that there was continuous
deposition of Coeymans and New Scotland sediments in the
study area. This is based on the predominance of grada-
tional contacts between different lithologic units, the
general parallelism of the major bedding, and the general
lack of conglomeratic beds in any of the non-detrital
units. Therefore, the assumption that tectonic activity

did not significantly affect the geometry of the basin

33

floor during deposition of Coeymans and New Scotland sedi-
ments appears to be valid.

Since the two assumptions involved in the strati-
graphic analysis of the Coeymans and New Scotland forma-
tions do not conflict with the observations, subordinate
time lines drawn parallel to the datum plane can be super-
imposed on the stratigraphic cross-sections above and below
the datum plane to show the vertical and lateral relation—
ships of the various lithologic units.

Previously, it was concluded that the upper
crinoidal limestone member of the Coeymans Limestone repre—
sented regressive deposition. However, based on the fine-
grained texture and poor sorting of fossiliferous beds in
the overlying New Scotland limestone and chert facies, the
sediments comprising the facies are believed to have been
deposited in somewhat deeper water than those of the upper
limestone member of the Coeymans. This suggests that the
sediments of the limestone and chert facies were deposited
during transgressive conditions. Therefore, the upper
limestone member probably represents both regressive and
transgressive phases of deposition.

If subordinate time planes (lines) are drawn on
the stratigraphic cross-sections parallel to and above the
datum plane it is apparent in most cross-sections that a
stratigraphic unit overlying another unit in a vertical
section grades laterally into an underlying or overlying

unit in another location. This indicates that sediments

34

of the different stratigraphic units were deposited
simultaneously in different portions of the depositional
basin. For example, while sediments comprising the upper
limestone member of the Coeymans Limestone were being
deposited at a given time in the vicinity of Monterey,
Virginia, other sediments making up some of the strati-
graphic units recognized in the New Scotland limestone
and chert facies were being deposited contemporaneously
in different portions of the basin (see Figures 6, 7, and
8).

As mentioned previously, beds of the limestone
and chert facies, crinoidal limestone facies, and crin-
oidal sandstone facies are intercalated at Millboro Springs
section. This is strong evidence that these three facies
of the New Scotland Formation are lateral equivalents.
Since a complete section of the Coeymans Limestone is
lacking at this outcrop because of faulting, the vertical
position of the columnar section on the stratigraphic
cross-section is questionable. The columnar section for
this outcrop was arbitrarily positioned so the Coeymans-
New Scotland contact corresponded with an extended line
passing through the same points in the columnar sections
for the Hively Gap and Monterey sections. If subordinate
time planes (lines) are drawn so they extend from the
limestone and chert facies to the sandstone facies, they
further suggest that sediments of the sandstone facies are

time equivalent to those of the different stratigraphic

35

units comprising the limestone and chert facies (see Figure
6). Similar lateral relationships are apparent between the
crinoidal limestone facies and the sandstone facies or the
limestone and chert facies (see Figures 7 and 8, respec-

tively).

CHAPTER III

PETROGRAPHY AND PETROLOGY

According to Krynine (1948) sedimentary rocks
possess three basic properties: composition, texture, and
structure. These properties may reflect depositional con-
ditions. However, the character of a given rock unit may
have resulted from (1) original constituents, textures,
and structures; (2) predominance of diagenetic features;
or (3) mixture of original features and diagenetic fea-
tures. Therefore, it is necessary to distinguish between
primary and secondary characters if the petrographic
aspects of a given rock unit are to be used, in part, to
delineate the depositional environment.

If any two adjacent formations of the Helderberg
Group observed in an outcrop of the study area actually
represent lateral facies of each other, as concluded in
the previous section; then, the textural or lithologic
differences between these two formations probably reflect
spatial variations of depositional conditions during a

given time interval.

36

37

A petrographic investigation of the Helderberg
Group was undertaken to (1) determine relative proportions
of constituent particles; (2) classify rock types present
and outline their vertical and horizontal distribution;
(3) relate particle form and arrangement to possible mode
of origin; (4) note relationships between diagenetic
alteration and specific particle type; and (5) establish
sequence of diagenetic changes. Data for these variables
are necessary for making inferences concerning the deposi-

tional environments of Helderberg sediments.

Method of Study

 

Twenty-two partial and complete Helderberg outcrops
were measured and described in Virginia and West Virginia
during the summer of 1966. A total of 425 rock samples
were randomly and purposely collected from these outcrops
for further petrographic studies.

Each sample was cut into three pieces perpendicular
to the bedding and polished. The samples were categorized
into groups representing different textures, colors (hues),
and stratigraphic units. At least one sample from each
category was selected for thin section studies. A total
of 80 thin sections were made. Also, plexiglass peels were
made on each sample following the procedures outlined by
Frank (1965) for additional textural and compositional
analyses.

Relative proportions of constituent particles of

each thin-section were determined from 300 point counts

38

following the method outlined by Chayes (1949 and 1956).
Then, point counts were made on plexiglass peels corres-
ponding to the samples from which the thin sections were
made. There was a maximum of 4 percent difference in the
relative proportions for any of the constituent particles
between the two counts for a given sample. Since there
was good agreement between counts on thin sections and
plexiglass peels, the relative proportions of the consti-
tuent particles of the remaining samples were determined

by point-counting plexiglass peels of these samples.

Petrographic Aspects of the Helderberg Group

 

From a mineralogical and textural standpoint the
Helderberg Group is composed of the following basic litho-
logies; limestone, sandstone, shale and chert. Limestone
is the dominant lithology of all the stratigraphic units
of the group except in the Shriver Chert, Mandata Shale,
and the Healing Springs Sandstone. Sandstone is predomi-
nantly restricted to the Healing Springs Sandstone. Shale
occurs as the dominant lithology of the Mandata Shale and
thin beds of calcareous shale occur in the limestone and
chert facies of the New Scotland Formation and in the
Shriver Chert-Licking Creek Limestone interval. Chert
occurs as lenses or nodules in the Coeymans Limestone, New
Scotland Formation, Shriver Chert, and Licking Creek Lime-

stones.

39

Mineralogical Composition

 

Analysis of polished sections and thin sections
reveal that one or more of the following are the dominant
mineral components of all Helderberg rock types: calcite,
quartz, illite(?), and chert. Dolomite, collophane,
tourmaline, feldspar, zircon, and organic material are
generally present in some samples as accessory components.

The characteristics of some of these components
probably are indicative of the depositional and post-
depositional history of the rock units. The following
section is concerned with the petrographic aspects of the

Helderberg mineral components.

Calcite

Calcite is the dominant mineral component of the
carbonate rock units and the second most abundant mineral
of the sandstone unit. Several different varieties of
calcite can be recognized in most samples of the Helderberg
rock types. These different calcite varieties are bio-
skeletal calcite, microcrystalline calcite, microsparry

calcite, and sparry calcite.

Bioskeletal Calcite.--This variety of calcite

 

includes all bioskeletal material, either entire, or frag-
ments of calcareous hard parts. Generally it was possible
to identify the type of material in thin section by shape,
internal morphology or by a combination of both of these

criteria, even though some fossil material had been

4O

fragmented, abraded or diagenetically altered to a con-
siderable extent. However, some calcite crystals which
were classified as sparry calcite in this study may
actually represent bioskeletal calcite, such as disarticu-
lated calcite prisms of gastropod or pelecypod shells or
plates of crinoid calyces. ‘Also some sparry calcite
possibly represents bioskeletal calcite which has under-
gone recrystallization to such an extent that any evidence
of bioskeletal material is lacking.

Bioskeletal calcite is a major constituent of most
of the Helderberg carbonate units and also commonly occurs

in samples from the crinoidal sandstone unit.

Microcrystalline Calcite.--According to Folk
(1959 and 1962) microcrystalline calcite includes all
carbonate grains smaller than four microns and lacks
clarity when viewed in thin section. In this study, how—
ever, microcrystalline calcite includes those calcite
particles smaller than ten microns because all grains
smaller than this lacked clarity.

As seen in thin section the grains appear to be
subtranslucent and display a faint brownish cast. Under
higher magnification (above 250x) individual microcry-
stalline calcite crystals are generally subtranslucent and
the crystals appear to be anhedral to subhedral, interlock-
ing grains.

In hand specimens and polished sections microcry-

stalline calcite has a dull and opaque appearance. Generally

41

the colors of this ultrafine—grained material varies from
grayish-white to gray in Coeymans samples, from gray to
bluish and brownish-gray in New Scotland samples, and
from gray to grayish-black in Shriver-Licking Creek samples.
Microcrystalline calcite is one of the major con-
stituents of the fine-grained limestones of the New Scot-
land limestone and chert facies and the middle member of
the Coeymans Limestone. It is also present in lesser
amounts in the lower and upper members of the Coeymans
Limestone and the crinoidal limestone facies of the New

Scotland Formation.

Sparry Calcite.--Sparry calcite includes most of

 

the clear calcite crystals whose shortest dimension is
greater than ten microns. Some of these crystals show
polysynthetic twinning, especially the larger crystals.
The crystals are usually subhedral to euhedral in shape
and interlocking. The smaller crystals of sparry calcite
were primarily distinguished from microcrystalline calcite
by their clarity.

In hand specimens and polished sections sparry cal-
cite appears clear with a vitreous luster. In most cases
it appears as a simple pore-filling cement. The samples
containing greater amounts of sparry calcite generally dis-
play a lighter color.

In thin section sparry calcite crystals were
observed occurring as cementing material filling the pore

spaces between allochem carbonate grains and as

42

recrystallized microcrystalline calcite or calcite prisms
of some fossils. Two types of sparry calcite cement were
recognized in thin sections: (1) corona sparry calcite
crystals as radiating overgrowths on allochem carbonate
grains and (2) interstitial sparry calcite in the pores.

Crystals of the corona type are usually subhedral
to euhedral, elongated crystals that radiate approximately
normal to the surface of the allochem grains. The corona
overgrowths include only one layer of crystals that sur-
round the grains. The crystals ranged from ten microns
to 0.1 mm in width and from ten microns to 0.2 mm in
length. The crystals were generally in optical continuity
with the allochem grains they were enclosing. All allochem
carbonate grains were not surrounded, however, by corona
sparry calcite crystals.

Interstitial sparry calcite crystals occur in void
spaces between allochem carbonate grains or corona calcite
crystals which are surrounding these carbonate grains.

The interstitial sparry calcite crystals are generally
larger than corona sparry calcite crystals and display good

polysynthetic twinning.

Microsparry Calcite.--Microsparry calcite refers

 

to crystals of clear calcite ranging in size from four
microns to 0.6 mm and do not show any relationship to
allochem carbonate grains or pore spaces. These crystals

generally occurred as isolated patches or grains incased

43

in microcrystalline calcite. The crystal shape was gener-
ally subhedral to euhedral.

This variety of calcite was most common in samples
of the New Scotland limestone and chert facies. However,
occasional microsparry calcite crystals occurred in some

of the samples from the Coeymans middle limestone member.

Quartz

Quartz is a common constituent in the Helderberg
Group but it is most common in the New Scotland sandstone
facies. Both detrital and secondary varieties of quartz
were noted in thin sections.

Generally the quartz grains observed in carbonate
samples were angular to subangular silt-sized particles;
however, in sandstone samples the grains were subangular
to rounded sand-sized particles.

Secondary quartz occurred as overgrowths on detri-
tal quartz grains. Secondary quartz overgrowths were
distinguished from the detrital grains in most cases by
the presence of a "dust" ring between the detrital grain
and the overgrowth. However, if a "dust" ring was absent
the secondary quartz could generally be distinguished from
the detrital grain by difference in clarity in plain light.
The detrital grains often had a turbid appearance due to
inclusions: whereas, the secondary quartz generally lacked
inclusions.

Secondary overgrowths were observed on many of the

detrital quartz grains in samples from the New Scotland

44

sandstone facies. In some thin sections of the sandstone
samples occasional detrital quartz grains were surrounded
by two or more cycles of secondary quartz overgrowths, as
indicated by two or more "dust" rings. There were no

secondary quartz overgrowths observed on any of the detri-

tal quartz grains in the carbonate samples.

Illite(?)

Argillaceous material is finely disseminated
throughout much of the New Scotland limestone and chert
facies. McCue and others (1939) indicate that the argilla-
ceous material in the New Scotland limestone beds is pro-
bably illite. Illite(?) is the dominant mineral of the
New Scotland shale facies. The remainder of the Helder-
berg units generally do not contain much argillaceous

material.

Chert

Chert is a microcrystalline variety of quartz and
was readily recognized in thin section by its pin-point
extinction. Chert occurred as disseminated particles and
nodular or lens-shaped masses. The disseminated chert
particles occurred encased in microcrystalline calcite.
Nodular or lens-shaped chert aggregates vary in size.
Some of the chert masses were developed solely within a
bioskeletal fragment; whereas, others were much larger
and no evidence of clastic carbonate grains was apparent.

Of those bioskeletal fragments which had been partially

45

replaced by chert the punctate brachiopod shells were gen-
erally the least affected.

Chert is most common in the limestone and chert
facies of the New Scotland Formation but it is also a
significant component in the middle limestone member of
the Coeymans Limestone. Chert was not observed in any

samples or outcrops of coarse grained limestone units.

Dolomite

Dolomite generally occurs as isolated rhombohedral
crystals in Helderberg carbonate samples. The crystals
were most common as replacement crystals in bioskeletal
material other than punctate brachiopod shell fragments;
however, they also were occasionally embodied in microcry—
stalline calcite. The total amount of dolomite in any

Helderberg sample ranged from zero to about 4 percent.

Collophane

Nodules of collophane occur in some Helderberg
units, particularly in the upper portion of the New Scotland
limestone and chert facies and in the lower part of the
Mandata Shale. These nodules are generally elliptical with
their longest axes being parallel to the bedding, but some
nodules display irregular forms.

In polished sections and thin sections occasional
grains of oolitic collophane were observed in some samples
as well as the nodular masses. The size of these colitic

collophane grains was similar to that of other associated

46

allochem carbonate grains. Occasional shell fragments or
detrital quartz grains were encased in the massive collo-
phane nodules.

In thin section the collophane displayed a dark
amber color in plain light but with crossed nicols the
collophane showed no or very weak birefringence colors.

No evidence of concentric layering was observed in any of
the collophane portions of the thin sections except in the

oolitic grains of collophane.

Tourmaline

Detrital grains of tourmaline were observed in most
thin sections of the New Scotland sandstone facies; however,
none was observed in any of the Helderberg carbonate sam-
ples. The grains are generally well rounded but some of
the grains were subangular. In plain light the grains are
pleochroic in shades of green and brown. The amount of
tourmaline present in the sandstone slides was always less

than 2 percent.

Feldspar

A very small amount of detrital feldspar grains
were noted in thin sections of samples from the New Scot-
land sandstone facies but none was observed in any of the
carbonate slides. Microcline was the most abundant vari-
ety of feldspar noted, followed by orthoclase, albite,
and oligioclase. The grains were subangular to rounded

and usually highly altered to give a cloudy appearance.

47

The amount of feldspar content in any of the sandstone

samples was less than 1 percent.

Zircon

Detrital grains of zircon were present in all sand-
stone thin sections but none was noted in any of the car-
bonate samples. These grains, however, constitute less
than 1 percent of any of the sandstone samples. The grains
are generally rounded but some subangular shaped grains

were observed.

Organic Material

(Streaks, patches, and specks of opaque material,
presumably carbonaceous material, occurred in some Helder-
berg samples. In reflected light the material has a dull,
"sooty" appearance. This material was most common in
those samples where the collophane content was highest,
particularly in samples from the upper units of the New
Scotland limestone and chert facies and from the lower beds

of the Mandata Shale.

Textural Components

 

The following section is concerned with the petro-

graphic aspects of the Helderberg textural components.

Carbonate Textural Elements
Grain, matrix (microcrystalline calcite), and cement
(sparry calcite) are the primary textural elements of all

Helderberg carbonate rocks. Different carbonate textures

48

are characterized by varying proportions of these

elements.

Grains.--Grains are discrete particles capable of
forming a rock framework. Four basic grain types were
recognized in Helderberg carbonate samples. They are (l)
terriginous; (2) bioskeletal; (3) intraclasts; and (4)
pellets.

Terriginous grains include all grains which were
derived outside the basin of deposition. The most common
type of terriginous grains observed in the carbonate sam-
ples were quartz and illite(?). The quartz grains were
generally angular, silt-sized fragments. In most samples
the clay content was low enough to be masked by microcry-
stalline calcite in thin section. Terriginous grains,
particularly quartz, were observed in most carbonate sam-
ples but they generally did not occur in abundance.

Bioskeletal grains are the remains of hard parts
secreted by organisms. They may occur as broken, abraded
fragments or as whole shells. It was generally possible
to identify the various kinds of skeletal material from
their internal structure and overall morphology as outlined
by Johnson (1951). Pelmatozoa, brachiopod, bryozoa, coral,
trilobite, ostracod, sponge, gastropod, and pelecypod bio-
skeletal grains were recognized in Helderberg carbonate
samples. Pelmatozoan debris and fragments of bryozoa and

brachiopods were the most abundant skeletal grains in the

49

Coeymans samples. Brachiopod and bryozoa fragments com-
monly occurred in New Scotland carbonate samples.

Intraclasts are allochem carbonate grains which
range in size from fine sand to pebbles or boulders. Pre-
vious investigators have called these pebble or boulder
sized intraclasts "edgewise conglomerates" or "flat pebble
conglomerates." Intraclasts were observed at the base of
the Coeymans Limestone at New Creek I and New Creek II
sections. The majority of the intraclasts were rounded
but some were subrounded to subangular. The intraclasts
consisted of some bioskeletal fragments encased in micro-
crystalline calcite. Lithologically, the intraclasts
were similar to the carbonate beds of the underlying Keyser
Limestone.

Pellets are rounded to avoid homogeneous aggregates
of microcrystalline calcite, without any internal structure.
They range between 0.03 and 0.2 mm in size. They are dis-
tinguished from intraclasts by the lack of internal struc-
ture, small size, and general uniformity of shape. Pel-
lets were observed in only two samples which were collected
from the lower member of the Coeymans Limestone at the
Pendleton-Grant county line section. These allochem car-
bonate grains were not recognizable before the samples were
slabbed and polished. Therefore, it is possible that some

beds containing pellets were not recognized in the field.

50

Matrix.--Matrix refers to a natural material in
which allochem carbonate or terrigenous grains were
embedded. The matrix material is generally several powers
smaller than the grains. In carbonate rocks microcrystal-
line calcite is the common matrix material if the rock
contains any matrix material.

Microcrystalline calcite is the common matrix
material of all Helderberg carbonate samples. The amount
of matrix material varies, however, from one sample to
another. Matrix material is more common in samples from
the New Scotland limestone and chert facies than the other

carbonate units.

Cement.--Cement refers to clear, crystalline mater-
ial which occurs in the interstices between grains and
matrix material. In carbonate rocks sparry calcite is a
common cementing material if the rock contains any cement.

Sparry calcite is the common cementing material of
all Helderberg carbonate samples. Cement is more common
in samples from the Coeymans Limestone and from the New
Scotland crinoidal limestone facies than the other carbon-

ate units.

Carbonate Rock Types

From the standpoint of textural elements the Held-
erberg carbonates can be classified according to a lime-
stone classification proposed by Folk (1959 and 1962).

This classification is descriptive and places primary

51

emphasis on the relative proportions of grains, matrix
(microcrystalline calcite), and cement (sparry calcite).
The classification system, however, does not necessarily
consider whether the grains are in mutual contact with one
another or not.

The fabric of carbonate rocks is another important
indicator of depositional conditions. Dunham (1962) has
advanced a descriptive carbonate classification that is
primarily concerned with the grain fabric of such rocks.
Carbonate rocks of the Helderberg Group can also be
classified according to these criteria. This scheme does
not, however, provide a means of differentiating carbonate
rock types which contain both matrix material and cement.

Since both classifications are applicable to the
carbonates of the Helderberg Group and both are descrip-
tive approaches from which genetic interpretations can be
drawn, a combination of the two is probably adequate for
classifying the carbonate rocks in this study. Based on
the type of grain support and the proportion of grains,
matrix, and cement the following carbonate rock types have
been recognized in the Helderberg Group: (1) micrite; (2)
biomicritic wackestone; (3) biomicritic packstone; (4)
biosparitic packstone; (5) biosparitic grainstone; (6)
pelsparitic grainstone; and (7) intrasparitic grainstone.
The terms wackestone, packstone, and grainstone were first

proposed by Dunham (1962). The terms micrite, biomicritic,

52

biosparitic, pelsparitic, and intrasparitic were first

introduced by Folk (1959).

Micrite.-—Micrite is defined as a carbonate rock
that is comprised of crystals of microcrystalline calcite
and contains less than 10 percent allochem carbonate grains.

Micrite is the dominant carbonate rock type of the
Shriver Chert-Licking Creek Limestone and the upper beds of
the Keyser Limestone. It also makes up a portion of the
limestone and chert facies of the New Scotland Formation.
In the New Scotland it generally occurs beneath the chert
lenses or layers which corresponds to the third unit of
the previously mentioned asymmetrical sedimentary cycles.

In polished sections, peels, and thin sections both
laminated and bioturbated micrites were recognized (see
Plate 1, Figures A and B). Disseminated chert commonly
occurred in greater abundance in the disturbed portions
of bioturbated micrite samples. Occasional grains of
microsparry calcite were randomly scattered in the micro-

crystalline calcite.

Biomicritic Wackestone.--Biomicritic wackestone is

 

a type of limestone that contains more than 10 percent
allochem carbonate grains and they are supported by micro-
crystalline calcite. Bioskeletal grains are the dominant
type of allochems in this category.

This is the dominant carbonate rock type in the New

Scotland limestone and chert facies, corresponding to the

53

Plate 1

Figure A.--Laminated micrite. Print of thin section shows
suggestion of bedding in otherwise uniform tex-
ture (6X). Up is toward top of bed. Shriver
Chert.

Figure B.—-Bioturbated micrite. Print of thin section shows
evidence of disrupted bedding, probably due to
burrowing organisms (6X). Up is toward top of
bed. New Scotland Formation.

54

4%.?

,I
u
..\

u

...
5..
m...

_
v

 

55

first and second sedimentational units of the asymmetrical
cycle. This rock type is also common in the Shriver Chert-
Licking Creek Limestone interval.

Shells and shell fragments of brachiopods are the
most common type of bioskeletal grains in samples from
both stratigraphic units; however, fragments of bryozoa,
crinoids, trilobites, and ostracods are common in some
samples. Bioskeletal grains of corals, sponges, gastro-
pods, and pelecypods occasionally occur in some of the
samples, especially in the New Scotland samples. In some
samples most of the disarticulated shells display a pre-
ferred convex upward orientation; whereas, in other samples
the shells have a spiral orientation which suggests that
the sediments were possibly disturbed after deposition by
burrowing organisms (see Plate 2, Figures A and B). In
both situations the bioskeletal material was usually com-

pletely encased in microcrystalline calcite.

Biomicritic Packstone.--Biomicritic packstone

 

refers to a type of limestone in which the allochem car-
bonate grains are grain supported and more than 50 percent
of the interstitial material is microcrystalline calcite.
Bioskeletal fragments are the dominant allochems in this
category (see Plate 3, Figure A! page 50).

This rock type comprises a portion of the Shriver
Chert-Licking Creek interval and the New Scotland limestone

and chert facies.

56

Plate 2

Figure A.--Biomicritic wackestone. Print of thin section
with brachiopod shell debris being the dominant
bioskeletal material and embedded in a lime mud
matrix (6X). Note preferred orientation of
shell material. Up is toward top of bed. New
Scotland Formation.

FigurejBrmBioturbated biomicritic wackestone. Print of
thin section (6X) with brachiopod bioskeletal
material displaying a random orientation and
embedded in a lime mud matrix. Up is toward
top of bed. New Scotland Formation.

57

t. ,. y:
, “n .4113.
s. v" '

 

58

The framework grains are predominantly bioskeletal
material and are of the same types that characterize the
biomicritic wackestones. Sparry calcite occurs in the
interstices between some shell fragments to produce a geo-
petal structure. Usually the sparry calcite adjacent to

the shells is of the corona variety.

Biosparitic Packstone.—-Biosparitic packstone is

 

defined as a type of limestone in which the allochem car-
bonate grains (predominantly bioskeletal grains) are grain
supported and less than 50 percent of the interstitial
material is microcrystalline calcite.

This type of limestone is the dominant type com-
prising the Coeymans Limestone and the crinoidal limestone
facies of the New Scotland Formation. Individual beds of
this type of limestone also occur near the boundary between
the Oriskany Sandstone and the Shriver Chert in some out-
crops (Petersburg Gap section) of the study area.

Fragments of pelmatozoan stems and bryozoa are
.the dominant bioskeletal material in samples belonging to
this rock type. Occasional fragments of brachiopod shells
occur in the samples. Except at the points of grain con-
tact most grains were surrounded with crystals of the
corona variety of sparry calcite and the remainder of the
pore space was filled with the interstitial variety. How—
ever, microcrystalline calcite was patchily distributed
in some of the interstitial areas of all samples, ranging

from 3 to about 13 percent.

59

Biosparitic Grainstone.--The term biosparitic

 

grainstone refers to a type of limestone in which the
allochem carbonate grains (predominantly bioskeletal grains)
are grain supported and no microcrystalline calcite occurs
in the interstices between the grains (see Plate 3, Figure
B).

This carbonate rock type is restricted to the Coey-
mans Limestone and even then it is not too common. The
bioskeletal grains have undergone some recrystallization
and the pore spaces between the grains are completely

filled with the interstitial variety of sparry calcite.

Pelsparitic Grainstone.--Pelsparitic grainstone is

 

a type of limestone in which the allochem carbonate grains
(pellets) are grain supported and no microcrystalline cal-
cite occurs in the interstices between the grains.

Only two samples are representative of this type
of limestone. These samples were collected from the Coey-
mans Limestone at an outcrop near the Pendleton-Grant
counties line. The textural attributes of this rock type
were not recognized until the samples had been cut and
polished; therefore, there may have been more beds of this
type of limestone which were not recognized in the field.

One sample consisted of layers of microcrystalline
calcite interbedded with the pellets. The pellets appear
to consist of microcrystalline calcite similar to that
comprising the micrite layers (see Plate 4, Figure A, page

I

63). The second sample consisted of well sorted, fine

60

Plate 3

Figure A.—-Biomicritic packstone. Print of thin section (6X)
consisting primarily of pelmatozoan stem debris
and lesser proportions of bryozoan fragments.
Note that the bioskeletal material is grain sup-
ported. Some microcrystalline calcite occurs in
the interstices between the bioskeletal grains.
Coeymans Limestone.

Figure B.--Biosparitic grainstone. Print of this section (6X)
consisting principally of pelmatozoan stem debris
and lesser amounts of bryozoan fragments. Note
that the bioskeletal grains are grain—supported.
Coeymans Limestone.

61

‘ ' ‘ " a." v'
s. 7' fur»:‘,. . «- .

' " ‘5 V ‘ _ . ,
3‘! ~.‘)§:§Q!‘.. ‘1'.\§. A
‘¢i?*.vx" .’

:‘r‘

 

62

sand sized pellets which are cemented with sparry calcite
cement (see Plate 4, Figure B). Even though the pellets
are in contact with adjacent pellets there is no evidence
of grain penetration. Also, none of the pellets display
any internal structures. The pellets are generally sur-

rounded with a layer of corona variety of sparry calcite.

Intrasparitic Grainstone.--Intrasparitic grainstone

 

refers to a type of limestone in which the allochem car-
bonate grains (intraclasts) are grain supported and no
microcrystalline calcite occurs between the grains.

This type of limestone was recognized in the basal
portion of the Coeymans Limestone at two outcrops (New
Creek I and New Creek II sections).

The intraclasts consist of micrite which is very
similar to that of the underlying Upper Keyser beds in
this area. Dimensionally the intraclasts were generally
a half inch thick and ranged from one to two inches in
length. Most of the grains were rounded, however, some
were subangular. Some bioskeletal debris (coral and

bryozoa) were mixed with the intraclasts in these beds.

Terrigenous Textural Elements

According to Krumbein and 81055 (1963) there are
six properties of the particles that influence the final
character of a terrigenous rock. These properties are
(1) size, (2) shape, (3) roundness, (4) surface texture,

(5) orientation, and (6) mineralogical composition. All

63

Plate 4

Figure A.--Pelsparitic grainstone and layers of micrite.
Print of thin section (6X) consisting of
layers of grain supported pellets interbedded
with thin layers of micrite. Note the simi-
larity of appearance between the pellets and
the microcrystalline calcite which comprises
the micrite layers. Coeymans Limestone.

Figure B.--Pelsparitic grainstone. Print of thin section
(6X) consisting of grain supported pellets

which are cemented with sparry calcite cement.
Coeymans Limestone.

64

mu
)3

4.x '
1“. f"

b
. " “

fi’ffi'léfi.” ‘
c’. -
‘2 ‘.

 

65

of these textural properties, except grain orientation,
were analyzed primarily in thin section because of the
lithified character of the samples. The mineralogical
components of the terrigenous rock units have been dis—

cussed in a previous section of this report.

Sigg.--The true grain size is underestimated when
measured in thin section (Griffiths and Rosenfeld, 1950).
In an attempt to keep this underestimation at a minimum
the longest dimension of 40 grains per thin section of
each sandstone sample were measured.

In some sedimentational units the grains ranged
from silt- to very fine sand-sized particles (1/32 mm to
1/8 mm). Most sedimentational units, however, consisted
of fine- to medium-sized grains (1/8 mm to 1/2 mm) with
the average being medium sand-sized grains (1/4 mm).
Occasionally the coarses sedimentational units would con-
tain some individual grains having a diameter up to 4 mm.
Within any given sedimentational unit the sorting was

generally good.

Shape, Roundness, and Surface Texture.--In hand

 

specimen most of the grains appear to be somewhat spheri-
cal. At times it is impossible to determine, however, in
a thin section whether a well-rounded grain has a spherical
or cylindrical shape.

In thin section the shape of the original terri-

genous grains comprising the New Scotland sandstone facies

66

varies from sub-rounded to rounded. Some grains show
authigenic overgrowths which also show sub-rounded to
rounded surfaces.

Some of the grains, as seen in the weathered por-
tions of hand specimens, have pitted surfaces which give
the grains a frosted appearance. In thin section this
pitted surface appears to be a corroded surface of the

quartz grains due to embayments of calcite cement.

Terrigenous Rock Types

From the standpoint of terrigenous grain size rocks
of the New Scotland sandstone facies can be classified as
siltstones, sandstones, and conglomeratic sandstones.

The sandstones, with few exceptions, can be classi-
fied as an orthoquartzite (Krynine, 1948). Quartz accounts
for more than 95 percent of the terrigenous grains in the
sand-sized sedimentational units. Some bioskeletal grains,
such as pelmatozoan stem debris, is associated with the
terrigenous grains. The grains are cemented with sparry
calcite cement.

The pebbles occurring in the conglomeratic sand-
stone units are generally polymineralic in content. They
are composed of interlocking crystals of quartz and feld-
spar.

The siltstones can be classified as feldspathic
siltstone (Pettijohn, 1957) since feldspars constitute

about 10 percent of the terrigenous fraction. Both the

67

quartz and feldspar grains are subangular to sub-rounded.
The terrigenous grains are cemented with sparry calcite

cements

Origin of Helderberg Rock Types

 

The compositional and textural aspects of a sedi-
mentary rock are a product of its origin, the environmental
conditions pertaining at the time of deposition and any
post-depositional processes that affected the rock.

This section of the report is concerned with the
origin of the various rock types of the Helderberg Group,
a postulated relationship to plausible depositional envir-
onments and later diagenetic alterations. Inferences con-
cerning the origin of Helderberg rock types, especially
the carbonates, are somewhat speculative but plausible
conclusions can be made by comparing the various textures
of these rocks to similar characteristics which have been
observed and studied in areas of recent carbonate deposi—

tion.

Origin of Rock Components

The basic components of terrigenous and carbonate
rocks are grains, matrix, and cement. Grains can be encased
in matrix, cement, or a combination of both. The origin of
the components is significant to the overall understanding

of the rock.

68

Grains

As mentioned previously, grains can be either
terrigenous or allochems. The term terrigenous, as used
in this report, refers to grains of minerals and rock
fragments which have been derived from outside the basin
of deposition; whereas, allochem refers to carbonate
grains which originated within the basin of deposition
and were transported to a site of accumulation in a solid

state.

Terrigenous Grains.--Quartz, illite(?), feldspar,

 

tourmaline, and zircon grains plus granitic pebbles are
the common terrigenous grains recognized in the Helderberg
terrigenous rock types. Quartz and illite(?) occur in
some of the carbonate rock types.

These types of terrigenous grains suggest that
the original source area for the sediments of the sand-
stone facies was a granitic source area. The occurrence
of some quartz grains which show at least two stages of
rounding suggest, however, that some of the sediments were
derived from preexisting sedimentary rocks.

Also the preponderance of well-rounded grains of
the more stable minerals suggest that rather intensive
chemical weathering conditions occurred in the source area
and the sediments were deposited in a high energy environ-

ment.

69

Allochems.--Bioskeletal grains, intraclasts, and

 

pellets are the common allochems recognized in the Helder-
berg carbonate rocks. Since the origin of bioskeletal
material is beyond the scope of this study this will not
be discussed; however, the environmental significance of
bioskeletal material is considered in other sections of

this report.

Intraclasts: Illing (1954) indicates that intra-

 

clasts (grapestones and encrusted lumps) are formed from
the accumulation of chemically precipitated lime mud and
silt by accretion and agglutination.

Folk (1959 and 1962) suggests a mechanical origin
for most intraclasts which involves penecontemporaneous
erosion of weakly consolidated calcareous sediments in
some area of the basin of deposition and then abrasion
and redeposition in some adjacent portion of the basin.
Folk (1962) further suggests that exposed, mud-cracked,
carbonate flats may provide much of the intraclast material.

The lack of any rolled layering which would result
from accretionary and agglutinating processes and the high
degree of lithologic similarity between the intraclasts
observed in the base of the Coeymans Limestone and the
micrite beds of the subjacent Keyser Limestone suggest a

mechanical origin for the intraclasts.

70

Pellets: Four basic processes have been suggested
for the origin of pellets. These processes are as follows:
(1) fecal excretions of organisms (Thorp, 1939; Illing,
1954; Newell and Rigby, 1957; and Folk, 1959 and 1962); (2)
auto-agglutination of formerly homogeneous calcareous mud
(Folk, 1962); (3) flocculation of suspended particles of
colloidal calcium carbonate (Hobbs, 1957); and (4) current-
worn fragments of poorly consolidated sediments of micro-
crystalline calcite (Laporte, 1969).

The pellets observed in some Coeymans Limestone
samples probably represent current-worn fragments of weakly
consolidated micrite. This conclusion is based on the
general absence of any shell fragments within any of the
pellets and the lithologic similarity between pellets and

subjacent micrite beds.

Matrix

Clay minerals are the dominant matrix material in
Helderberg terrigenous rocks. Most clays probably have
resulted from chemical breakdown of alumino- and ferromag-
nesium silicates in the source area.

Microcrystalline calcite is the dominant matrix
material in allochem carbonate rocks. Several theories
have been proposed for the origin of microcrystalline cal-
cite and these may be listed as follows: (1) physico—
chemical precipitation from waters of abnormally high
salinity and carbonate saturation (Black, 1953 and Cloud,

1962); (2) precipitation through bacterial metabolism and

71

decay (Lalou, 1957; Oppenheimer, 1961; and Greenfield,
1963); (3) skeletal disintegration by removal of binding
organic matter (Lowenstam, 1955, and Stockman and others,
1967); (4) skeletal disintegration resulting from activity
of boring organisms (Ginsburg, 1957); and (5) breaking and
abrasion of skeletal material in turbulent water (Cloud,
1959; Chave, 1964; Folk and Robles, 1964; Matthews, 1966;
and Force, 1969). Even though several modes of origin
have been proposed for the origin of microcrystalline cal-
cite (lime mud) there are no methods of detecting the
origin of a given crystal grain. However, the conditions
in which microcrystalline calcite can be deposited is of
environmental significance. Deposition of these clay-

sized particles requires quiet water conditions.

Cement

Sparry calcite cement is the dominant cementing
material in the terrigenous and carbonate rocks of the
Helderberg Group. Sparry calcite cement can result from
the following: (1) calcite precipitation from carbonate-
rich solutions; (2) inversion of aragonite precipitated
from sea water into the void spaces; or (3) recrystalli-
zation of microcrystalline calcite occurring between the
framework grains.

Before any plausible inferences can be deduced
regarding the depositional environments of carbonate rock

types, particularly the packstones and grainstones, it is

72

necessary to recognize the origin of the sparry calcite
cement.

The following petrographic observations have been
interpreted as being useful criteria in this study for
recognizing primary sparry calcite cement that was precipi-
tated from a carbonate-rich solution: (1) occurrence of
corona variety of sparry calcite around the grains and
interstitial variety filling in the remainder of the void
space, and (2) presence of sharp boundaries between grains
and cement.

If both conditions were observed in a given portion
of a thin section or plexiglass peel it was assumed that
the sparry calcite represented a primary pore filling. If
recrystallization of microcrystalline calcite had occurred
the boundary between the grain and the cement would pro-
bably not be sharp and clearly defined. In addition, the
fact that crystals of the corona variety radiate normal to
the surface of the allochem carbonate grain suggests that
original grain growth was unobstructed in the pore space.
Bathhurst (1958) and Cotter (1966) believe that this type
of crystal growth indicates a primary origin for the sparry
calcite cement.

If, however, sharp and well-defined boundaries
occur between the grains and cement but the corona crystals
are lacking this may indicate that aragonite was originally
precipitated into the void spaces from sea water and later

underwent inversion to form a sparry calcite cement.

73

Gevirtz and Friedman (1966) have presented conclusive evi-
dence that aragonite cement can be precipitated in pore
spaces from sea water. Berner (1966) has shown that
aragonite readily inverts to calcite when it comes in con-

tact with either brackish or fresh water.

Microsparry Calcite

Crystals of microsparry calcite are silt-sized
particles that generally were randomly distributed in a
groundmass of microcrystalline calcite. These particles
may represent either recrystallized grains of microcry—
stalline calcite or finely comminuted bioskeletal material.
Since the grains generally exhibit a random distribution
in thin sections and peels, it is assumed that these par-
ticles are recrystallized grains of microcrystalline cal-

cite.

Origin of Helderberg Cherts

 

Chert occurs as nodules, lenses, stringers, and
beds or as disseminated silica in the middle limestone
member of the Coeymans Limestone, in the limestone and
chert facies of the New Scotland Formation, and in the
Shriver Chert-Licking Creek Limestone interval.

In some cases the origin of a cherty mass, such
as a silicified brachiopod shell, is readily apparent.
However, other massive chert bodies, as well as dissemi-

nated chert, can have a primary or replacement origin.

74

Therefore, it is important to determine the origin of the
chert occurring in the Helderberg units.

The bedded chert layers generally show an irregular-
bottomed surface, an occasional faint trace of relict bed-
ding, encased masses of limestone, and occasional ghosts
of fossils. These observations suggest that the chert
lenses, beds, and nodules represent a replacement origin.

In thin section shell fragments were observed in
varying stages of being replaced by chert. Some shells
which had been completely replaced with chert were also
completely surrounded by chert to produce a nodular mass.
In other thin sections there were no evidence of preexist-
ing bioskeletal material in the chert nodules. This is a
further indication that the chert masses are of a replace-
ment origin.

Disseminated silica was noted in all samples
collected from a horizon subjacent to a chert lens or bed.
These samples are generally a bioturbated micrite. Those
samples which displayed the greatest amount of bioturba-
tion generally contained larger amounts of disseminated
silica than samples which were less disturbed. This sug—
gests that the more disturbed portions of the carbonate
sediments possibly acted as avenues for movement of silica-
rich solutions. On this basis the overlying massive chert
layer may represent an accumulation of chert where the

sediments were more disturbed by burrowing organisms. This

75

could also explain the sparseness of fossils or fossil
ghosts in the more massive chert layers.

In a given sample or sample locality the amount of
microcrystalline calcite should theoretically decrease as
the amount of chert increases. A rank correlation coeffi-
cient was calculated so the microcrystalline calcite-chert
relationship could be evaluated. This type of statistic
was used since the population distribution is unknown.

The rank correlation coefficient value is -0.16 but is not
significant at the 0.05 level of significance. However,

if the amount of microsparry calcite is included with that
of microcrystalline calcite the rank correlation coefficient
value for the matrix (microcrystalline calcite plus micro-
sparry calcite)- chert relationship is -0.97 which is sig-
nificant at the 0.05 level of significance. This suggests
that microsparry calcite is recrystallized microcrystalline
calcite; and that at least disseminated and fossil replaced
chert were more favorable at those sites where recrystal-
lization had occurred.

Field and petrographic evidence suggests that most
of the chert occurring in the Helderberg units is of a
replacement origin. Therefore, the presence and character-
istics of the chert can not be used to infer conditions at

the time of deposition of Helderberg carbonate sediments.

76

Origin and Environmental Significance
of the Helderberg Rock Types

The Helderberg Group displays several facies of
both carbonate and terrigenous rocks implying a diversity
of local environments at the time of origin. The follow-
ing discussion is concerned with the origin or mode of
deposition of the various terrigenous and carbonate

Helderberg rock types and their environmental significance.

Terrigenous Rock Types

Variations in grain size (clay versus silt versus
sand) and mineral composition suggest that sediments of
the various terrigenous rock types were deposited under

somewhat different depositional conditions.

Orthoquartzite.--The very high percentage of quartz

 

grains comprising the orthoquartzitic beds, their high
degree of roundness, and their good sorting suggest that
rather slow rates of sediment influx occurred during depo-
sition and the sediments were deposited in a high energy
environment such as a beach.

The flat-bottomed, lens-shaped nature of the ortho-
quartzitic beds and the presence of some cross-stratifica-
tion further indicate that the sediments represent migrating

sand bar deposits.

Feldspathic Siltstone.--The smaller grain size,

 

greater angularity, and lower percentage of quartz grains

in the siltstones suggest that these sediments were deposited

77

in an entirely different depositional environment than
those of the orthoquartzitic beds. The smaller grain size
of the siltstones indicate that deposition occurred in an
area where water turbulence was not as intense as that
associated with the sand-sized particles of the ortho-
quartzites. Siltstone beds are, however, laterally adja-
cent, superjacent, and subjacent to orthoquartzitic beds
in the New Scotland sandstone facies (Healing Springs Sand-
stone) and this indicates that sediments of the two rock
types were deposited simultaneously in the same general
area. Therefore, the silt-sized sediments were probably
deposited in an area that was somewhat protected from
intense water turbulence, such as in basins on the lee

side of the sand bars.

Shale,--Deposition of very small clay-sized parti-
cles comprising a shale requires calm water conditions.
Therefore, the shale units of the Helderberg Group were
deposited in either deeper water environments or more

protected environments.

Carbonate Rock Types

Even though studies of recent carbonate sediments
indicate that depositional conditions producing different
types of carbonate deposits are complex, it is possible
to make two generalities concerning the accumulation of
carbonate particles. They are as follows: (1) deposition

of microcrystalline calcite generally occurs in areas

78

lacking persistent strong currents, and (2) deposition of
allochems having higher degrees of grain contact require
more agitated water conditions.

Assuming that diagenetic textures can be differ-
entiated from primary depositional textures, it is possi-
ble to formulate logical depositional conditions for the
various Helderberg carbonate rock types by referring to
the two generalities, mentioned above, since the rock
types are based on the relative amounts of microcrystalline
calcite present and the number of grains having grain

contacts.

Micrite and Wackestone.--Microcrystalline calcite

 

is the dominant component of micrite and wackestone varie-
ties of limestone. This implies that deposition probably
occurred in areas lacking strong currents. Microcrystal-
line calcite can be deposited in the following conditions:
(1) in protected lagoons (McKee, 1949); (2) in broad,
shallow platforms on the lee side of barriers (Fairbridge,
1950); (3) on the slope of a geosyncline or basin below
wave base (Tyrrell, 1969); (4) in basinal portion of geo—
syncline (Garrison and Fischer, 1969; Thomson and Thomasson,
1969; Wilson, 1969; and Tyrrell, 1969); (5) in fairly high
energy environments where organic material, such as marine
grasses or algal growths, act as baffles (Ginsburg and
Lowenstam, 1959); and (6) in carbonate tidal flats (Laporte,

1967).

79

If micrites and wackestones display mud-cracked
surfaces this suggests that deposition occurred in a
supratidal, mud-flat environment (Laporte, 1967 and 1969).
Based on the occurrences of mud-cracked surfaces and
micritic beds the uppermost beds of the Keyser Limestone
were deposited in a supratidal, mud-flat environment.

Micrite and wackestone beds of the New Scotland
Formation and the Shriver Chert-Licking Creek Limestone
interval were probably deposited below wave base. This
conclusion is based on the stratigraphic relationship of
the two units to the Coeymans and Keyser limestones and
on the high faunal diversity (see section on paleosyne-
cology) of the New Scotland which suggests an open marine
environment.

Many of the micrite and wackestone beds do not
show distinct bedding or laminations, but disrupted bed-
ding. This could be a result of burrowing organisms or
slumping. The absence of slump structures (Potter and
Pettijohn, 1963) further indicate that the activity of
burrowing organisms accounts for most of the disrupted

bedding.

Packstone and Grainstone.--Packstones and grain-

 

stones are limestones that are characterized by self-
supporting allochems with little or no microcrystalline
calcite occurring in the interstices. This type of grain
arrangement is generally a property of rocks deposited in

agitated water. This type of depositional condition

80

occurs on the margins of carbonate banks and platforms
(Newell and others, 1951; Illing, 1954; Ginsburg, 1956;
Newell and Rigby, 1957; and Newell and others, 1960).

Packstone and grainstone beds comprising the
Coeymans Limestone and the crinoidal limestone facies of
the New Scotland Formation were deposited in more strongly
agitated water conditions than other Helderberg carbonate
beds. They represent marginal or shelf deposits asso-
ciated with an overall transgressive sea. These conclu-
sions are based on the degree of sorting these rock types
display and their stratigraphic relationships to the other
Helderberg units.

Pelmatozoan stem debris is the dominant type of
clastic carbonate grain in most Helderberg packstones and
grainstones. It is not certain whether these rock types
resulted simply from physical removal of smaller grains
to form a lag deposit or the durrent-swept areas provided
favorable sites for the development of crinoidal meadows.
Since most of the packstone and grainstone beds are lens-
shaped and cross-bedded, this probably indicates that the
deposits are lag deposits.

Theoretically, packstone varieties of limestone
should not occur because grain-support and muddiness
require entirely different modes of deposition. The occur-
rence of microcrystalline calcite in the interstices of
grain-supported carbonate rocks (packstones) could result

as follows: (1) compaction of wackestone; (2) infiltering;

81

(3) mixing due to burrowing organisms; (4) incomplete
winnowing; or (5) partial leaching (Dunham, 1962).

If a packstone resulted from compacting a wacke-
stone, one should observe the development of styolites
or microstyolites, evidence of grain penetration, or
both. Microstyolitic surfaces were observed in some thin
sections of packstones; but no evidence of grain penetra-
tion was observed.

If the occurrence of microcrystalline calcite in
the interstices of a grain-supported carbonate rock was
due to infiltering, the minute crystals should be concen-
trated in the bottom portion of the interstices. This
type of evidence was not recognized in all Helderberg
packstone samples.

If a packstone resulted through partial leaching
of the microcrystalline calcite comprising a wackestone,
one would expect to observe some evidence that the allo-
chem were also affected. Evidence of this type observed
was not in any of the Helderberg samples.

It is almost impossible to differentiate between
a localized mass of microcrystalline calcite resulting
from the mixing activity of burrowing organisms and one
resulting from incomplete winnowing unless the material
has a vertical orientation. Most of the matrix material
in the interstices of Helderberg packstones is due to
either burrowing organisms or incomplete winnowing. How-

ever, some occurrences may be due to compaction.

CHAPTER IV

PALEONTOLOGY

Woodward (1943) lists 32 Coeymans and 91 New
Scotland fossil species which have been identified in
outcrops of these formations in West Virginia. However,
he did not indicate their relative abundance, species
associations, or species-rock type associations. Also,
Swartz (1929 and 1939), Butts (1940), and Woodward fre-

quently mention the G. coeymanensis or the M. macropleurus

 

faunal assemblages without indicating what other species
comprise these assemblages.

In this study 18 fossil species from the Coeymans
Limestone and 32 fossil species have been identified sub-
jectively, plus numerous crinoid stems and undifferentiated
bryozoa from both formations. Table 1 is a listing of those
species identified in this study and their relative per-
centage of occurrence. Generic nomenclature of sponges,
corals, brachiOpods, crinoids, gastropods, and trilobites
follows the Treatise on Invertebrate Paleontology for the

respective phylum.

82

83

TABLE l.--Helderberg Fossils.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Formation
New
Fossil Coeymans Scotland
Porifera
Hindia sphaeroidalis 0.00 0.09
Coelenterata
Streptelasma strictum 0.41 4.06
PleurodICtyum lenticulare 0.00 0.09
Favosites conicus 3.83 0.44
Crinoidea
Edriocrinus pocilliformis 0.00 **
Trilobita
Phacops logani 0.14 0.18
Dalmanites pleureptys 0.00 0.18
Gastropods .
Platyceras trilobatum 0.14 0.18
Brachiopoda
Dalmanella perelegans 0.00 0.18
Platyorthis planoconvexa 0.00 0.09
Rhipidomella assimillis 0.00 0.71
5. oblata 3.55 9.36
Gypidula coeymanensis 33.06 0.00
Camarotoechia Iitchfieldensis 0.27 0.18
Eatonia_peculiaris 0.00 0.26
Eatonia singularis 0.00 0.26
Uncinulus abruptus 0.27 0.26
Anoplotheca concava 0.00 0.09
Atrypa_"reticu1arIS" 5.87 6.27
Atrypina imbricata 0.00 0.09
Delthyris perlamellosus 4.37 8.91
Macropleura macropleurus 0.00 18.18
Meristella lata 1.64 11.56
Nucleospira elegans 0.00 0.35
WSpiriferficoncinnus 0.00 0.35
_S.' cyclopterus 0.00 3.35
Trematospira equistriata 0.00 0.62
T. multispriata 0.00 0.97
Leptaena "rhomboidalis" 3.28 9.36
Schellwienella woolworthana 8.74 14.03
Stropheodonta planulata 0.27 5.21
Rensselaeria subglobosa 0.27 0.88
Rhynchospirina species 0.00 0.09
Crinoid stems 33.61 2.47
Undifferentiated Bryozoa 0.00 0.79

 

**Observed in some outcrops of Healing Springs Sandstone.

CHAPTER V

PALEOSYNECOLOGY

Paleosynecology is the study of living communities
of the past, their relationships with their physical and
chemical environment, and their interrelationships among
themselves (Ager, 1963). This section of the report is
concerned with the interspecific associations and environ-
mental significance of 34 species of New Scotland inverte—
brate macrofossils observed at 14 outcrops in West Virginia
and Virginia.

The knowledge of the ecology of fossil species pro-
vides a means of interpreting the physical and biological
conditions of the geologic past. Ideally, if a group of
fossils shows no evidence of abrasion or breakage and dis—
plays a certain growth orientation it is possible to infer
a life assemblage for this group of fossils. However,
fossil assemblages are rarely found where preservation and
orientation of the fossils indicate a primary association
(Craig, 1954).

Preliminary field observations showed that most New

Scotland fossils had been transported to some degree.

84

85

Therefore, some other criterion is necessary to determine
their interspecific associations.

When a fossil shell or fragment of a certain species
occurs in close proximity with a fossil shell or fragment
of another species at a given location in an outcrop it
usually does not have much paleoecologic significance. But
if this same association recurs at several locations within
many outcrops throughout a large area this fossil relation-
ship probably is significant. A basic assumption utilized
in this portion of the study is that the probability of
having two fossil species associated with each other is
much higher if they originally lived together than if they
did not. Some fossil associations may be due to factors
influencing accumulation and preservation, samples repre-
senting two or more unrecognized environments, or chance.
If a large number of random samples from lithological
similar units are evaluated, it should be possible to sta-
tistically exclude some, if not all, of the extraneous
associations. Johnson (1962a) used this approach in a
study to determine the interspecific associations of Penn-
sylvania fossils. Also Valentine and Mallory (1965) found
that fossil species associations based on many samples
corresponded to recent living associations even though

some transportation of shells had occurred.

Method of Determining Species Associations

 

Several statistical and empirical methods have been

utilized to analyze interspecific association of natural

86

ecological units (Forbes, 1907 and 1925; Jaccard, 1908;
Cole, 1949; and Fager, 1957) and paleoecological units
(Beerbower, 1957; Beerbower and McDowell, 1960, Johnson,
1962a; Ellison, 1963; and Valentine and Mallory, 1965).

The empirical method, such as the one proposed by
Jaccard (1908), does not provide a means of excluding
those associations which might be due to chance.

Beerbower (1957) used a correlation statistic to
study the faunal association of the Centerfield coral zone
in Pennsylvania. However, the frequency distribution of
fossil abundances in unknown and is probably not normal.
Moreover, two species may occur together frequently in
marine communities and have no constant relationship between
their numbers (Johnson, 1962a). Since the use of a corre-
lation statistic is questionable, one was not used to
determine interspecific associations for the New Scotland
fossils.

A chi square test was used to test the independence
of the distribution of two species from 260 samples.1 The
results of the chi square test are interpreted to indicate
that two species are or are not associated at a stated level
of significance (Johnson, 1962a). The chi square test has
been used previously by Beerbower and McDowell (1960),
Johnson (1962a), and Valentine and Mallory (1965) to deter—
mine the interspecific associations of Devonian, Pennsyl-

vania, and Pleistocene strata respectively.

87

.Method of Sampling

 

All statistical methods of data analysis assume that
the data are random and independent. The chi square test
for independence is no exception.

To insure that the data were random and independent,
two groups of random numbers were generated for each out-
crop by the use of random number tables in the appendix of

Introduction to Statistical Analysis (Dixon and Massey,

 

1957). The first group of random numbers represented a
stratigraphic thickness, in inches, above the base of the
formation. Each section had been previously measured so
the largest possible number to be generated for each out-
crop was controlled by the thickness of the formation.

The second group of random numbers represented some dis-
tance, in inches, from the base of the outcrop if the
strata were steeply dipping or from the left side of the
outcrop, as viewed when facing the outcrop, for horizontal
or gently dipping strata. The largest random number to be
generated for the second group of numbers depended on the
extent of the outcrop or the accessibility of the entire
outcrop. The point on the outcrop located by the inter-
section of the first random number in group one, and the
first random number in group two, is the first random
sampling point for the outcrop. The remaining random
sampling points were established in the same manner.

Figure 12 is a diagramatic drawing to illustrate the

88

 

\ Shriver Chert

   
 

\
4. 1— \ New Scotland Formation

  

 

 

 

 

 

 

\
\
\
\ extent of safe
\ access
+4
'I‘ \
\
‘F \
Concealed \
\
\
+_7' \
.1. \
’ +4= ix \
F u = . /
DCALE l 5 // \ \ Coeymans
4 / \ Limestone
/ \
/// \
/ \.>
Fossil Sampling Line
IN ‘\ L ‘ ‘444“%7=J* ‘”“1 ‘f::=‘&
'\ Random sample
Scale 1" = l' ‘ POint

 

 

 

Figure 12.--Hypothetical random sampling point on gently
dipping strata. The upper drawing diagramati-
cally illustrates the location of 20 random
sampling points in a Helderberg outcrop. The
bottom drawing depicts the relationship of the
sample line to the location of a given random
sample point. Note that the sample line starts
on a fossil nearest to the sample point and is
parallel to the bedding.

 

89

location of some hypothetical random sampling points on
gently dipping strata.

If the random sample point did not coincide with
a fossil or fragment, the distance from the sample point
to the nearest fossil or fragment, either in a strati-
graphically vertical, horizontal, or oblique direction,
was recorded. If the closest specimen was in a different
rock type than that of the random sample point another set
of random numbers were generated. This was continued until
a random number and the closest fossil were in the same type
of lithology.

A chalk line was stretched parallel to the bedding
along the face of the outcrop starting at the random sample
point, if it coincided with a fossil, or at the nearest
specimen. Every specimen which the line crossed was iden-
tified to species, of possible, and recorded. This method
of sampling is called the line transect method. The follow-
ing information was also recorded: (1) whole fossil or
fragment, (2) if fossil was a bivalve which valve was
present where disarticulated, (3) distance between speci-
mens, and (4) type of lithology. Twenty sample lines were
investigated in each section.

McIntyre (1953) indicates that the line transect
method is well established in theory and practice as giv-
ing a level of precision in the estimate for a given effort
which compares very favorably with other methods of sampl-

ing. There are, however, some limitations with the line

90

transect method. The main deficiencies are (1) the counts
made along the line will be proportional not only to
abundance but also to the size (diameter) of the specimens
and (2) the practicality of the method is void below a cer-
tain specimen density (McIntyre, 1953 and Ager, 1963). This
method of sampling has been employed successfully by John-
son (1962b) in a paleoecological study of the Millerton
Formation at Tomales Bay, California.

In order to compare one section quantitatively with
another section a standard unit of sampling length or area
must be used. Johnson (1962b) used a sample line of four
meters in the Millerton Formation study. Preliminary
attempts to use a sample line of four meters in this study
proved to be unfavorable because some portions of the out-
crops were inaccessible, some lines crossed different
lithologies, or some lines extended into highly weathered
or concealed portions of the outcrop. Since the length of
any sample line is controlled by the accessibility of the
outcrop, uniformity of lithology or degree of weathering
the longest line possible was used. Each line was roughly
evaluated by a species-length of line method, which is
discussed below. If a useful minimum length of line was
not-attained another random point was established.

A species-length of line method was used to deter-
mine the necessary minimum length of sample line in this
study. This is a modification of the species-area method

introduced by Cain (1938).

91

Braun-Blanquet (1932) introduced an empirical con-
cept for determining the minimum sampling area required to
describe a plant community. This method involves plotting
the number of species found in a stand on the y-axis coor-
dinate of a graph and the area of the stand on the x-axis
coordinate. After several stands of various sizes have
been plotted the curve generally rises rapidly from the
origin of the graph and then gradually becomes asymptotic
with the x-axis. According to Braun-Blanquet (1932) the
minimum area corresponds to the point where the species—
area curve becomes nearly straight and horizontal.

Cain (1938) has shown, however, that the character-
istic shape of the species-area curve depends on the x-y
ratio which has been plotted. Therefore, if the same data
is plotted twice, but with different x-y ratios, different
values for the minimum area will be suggested by the
method proposed by Braun-Blanquet (1932). In order to
standardize the use of the species-area method Cain (1938)
proposed the use of a point on the curve which represents
a rate of increase of 10 percent in the total number of
species and an increase of 10 percent of the total sample
area as the representative minimum sampling area. The
location of the point is not affected by the ratio of x
to y. This point can be located easily by placing the
edge of a triangle so that its edge passes through the
origin of the graph and the point which corresponds to 10

percent of the area and 10 percent of the species. Then

92

place a ruler along the right side of the triangle and slide
the triangle up or down until its edge is tangent to the
curve. The point of tangency corresponds to the minimum
area which would contain an adequate representation of an
association.

Since a line transect method was utilized in this
study rather than a quadrant method, the length of the line
was plotted on the x-axis instead of the area of a quadrant.
Figure 13 is a diagrammatic drawing to illustrate how the
minimum length of line was determined for each sample
line.

The minimum length was determined for each sample
line. Then the average minimum length was determined for
each outcrOp. The range of the average minimum length of
line for the outcrops was from 1.0 foot for Maysville Gap
section to 5.0 feet for Bull Pasture Mountain and New
Creek I sections. The average minimum length for the 12
complete sections in the study area is 3.0 feet with a
standard deviation of $.06 foot.

One could use the largest minimum value as a stan-
dard length but 114 of 240 lines were not 5 feet in length.
Therefore, it was decided to use a line segment of 3.6
feet. This value is the average minimum length for 12
sections plus the positive standard deviation. By using
a length of 3.6 feet only 31 lines were shorter. Admittedly

some of the data is lost by using the smaller value but

 

 

j 1 l T \1 9 t ' ' ' '
10 15 20 25 3b 35 4o 4 so 55 60
Length of Samp - Line (in eet)

Figure 13.--Species-Length of line curve, showing how the

minimum length of line was determined for an
adequate sample.

94

for comparison purposes 3.6 feet is more representative in

the study area.

Method of Analysis

 

Interspecific associations were determined by the
use of the chi-square test for independence. Since 34
species were identified there are 561 possible combinations
to be analyzed for independence. A computer program1 which
formed a contingency table for each possible combination and
then computed the expected values for each cell of the table
and the chi square value was used.

Each species was assigned a number from one to 34.
Columns one through 34 on the data cards represented a
species or variable. Each card represented a sample line
or observation. Every species on a sample line was recorded
on the data cards by key-punching a one in the appropriate
column for the particular species.

The contingency table that the program generates
from the input data is a 2 x 2 table based on the presences
or absences of two species. Two species are not considered
to be associated unless they meet the following requirements:
(1) the computed chi square value is greater than x2.95
for 1 degree of freedom (for 1 degree of freedom x2.95 =

3.84), (2) the minimum expected value for any cell is

 

1The computer program used in analyzing the inter-
specific associations is entitled Analysis of Contingency
Tables (ACT 1.01) and was written by Alan M. Lesgold of the
Computer Institute for Social Science Research at MSU.

95

greater than 5, and (3) the observed value is greater than
the expected value for the cell representing the presence of
both species.

If the computed chi square value is greater than the
theoretical chi square value the hypothesis of independence
is rejected and the result of the chi square test is taken
to indicate that two species are associated at the stated
level of significance. A relatively low level of signifi-
cance (a = 0.05 and a = 0.01) was arbitrarily selected so
the rejection of extraneous associations would be increased.

According to Dixon and Massey (1957) the minimum
expected frequency for the 2 x 2 table should not be less
than 5. Cochran (1954) indicates, however, that the expected
frequency of a 2 x 2 table can be less than 5 in certain
situations. But it was decided to utilize a minimum
expected frequency of 5 as an additional means of excluding
extraneous associations.

Some combinations may appear to be associated using
a chi square statistic. However, if the expected value
exceeds the observed value in the cell representing the
presence of both species, a negative association is indi-
cated. Johnson (1962a) indicates that a negative associa-
tion may reflect the relations of two species with different
environmental preferences or the circumstances where the
presence of one species excludes the other. It was there-
fore decided to consider only those statistically associ-

ated combinations with the observed value greater than the

96

expected value so that a positive association would

result.

Results of the Analysis

 

Table l is a listing of the 34 fossil species
identified in this study. No attempt was made to identify
crinoid stems and bryzoa to species level. Of the 561
combinations analyzed for interspecific associations 33
combinations were significantly associated at the 0.05
level of significance and 27 combinations were highly
significant at the 0.01 level of significance. Ten species
plus the undifferentiated crinoid stems account for the
33 significantly associated combinations. The ten species
.showing positive associations are Streptelasma strictum,

Rhipidomella oblata, Atrypa "reticularis," Meristella lata,

 

 

Stropheodonta planulata, Spirifer cyclgpterus, Delthyris

 

perlamellosus, Macropleura macropleurus, Schellwienella

 

 

woolworthana, and Leptaena "rhomboidalis."

 

 

M. macropleurus and L. "rhomboidalis" are both

 

associated with eight species. R. oblata, M. lata and

S. woolworthana are associated with seven species each.

 

S. strictum and D. perlamellosus are both associated with

 

 

six species. S. planulata is associated with five species.

A. "reticularis" and S. cyclOpterus are both associated

 

with two species. Table 2 is a listing of the species

combinations showing positive associations.

 

97

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98

Recurrent Groups

 

Recurrent groups were assembled from those species
found to be significantly associated by a systematic
method of grouping proposed by Fager (1957). Any dichoto-
mous index of relationship between species can be used as
a basis for grouping by this procedure (Fager, 1957).
Therefore, it is permissible to use the chi square statis-
tic as a basis for grouping.

A recurrent group, as defined by Fager (1957) and
recognized in this study is one which satisfied the follow-
ing requirements:

1. The evidence for affinity (association) is

significant at the 0.05 level for all pairs
of species within the group.

2. The group includes the greatest possible
number of species.

3. If several groups with the same number of
members are possible, those are selected
which will give the greatest number of
groups without members in common.

4. If two or more groups with the same number
of species and with members in common are
possible, the one which occurs as a unit
in the greatest number of samples is chosen.

Table 3 is a trellis diagram displaying the affin-
ity'information for the species concerned in this study.

Thirty-one groups satisfy requirements 1 and 2. Of the

99

 

 

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Axe Axe x Axe Axe Axe Axe ssuofluum .m
Axe x x Axv Axe Axv Axv mcmnuuozaooz .m
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100

31 groups only three groups satisfy requirements 3 when
the species interrelationship is examined in detail. The
three groups contain the following species:

Group 1. M. macropleurus, L. "rhomboidalis,"

 

S. woolworthana, D.pperlamellosus, S.

 

strictum, and S. planulata.

 

Group 2. R. oblata, L. "rhombodalis," S. wool-

 

worthana, D. perlamellosus, S. strictum,

 

 

and S._planulata.

Group 3. M. lata, L. "rhomboidalis," S. wool-

 

worthana, D. perlamellosus, S. strictum,

 

and S. planulata.

 

The original field data were checked to see which
group occurred most frequently as a unit. Species of the
first group occurred as a unit in 14 sample lines; whereas,
those of the second group were present nine times and
those of the third group occurred only three times. Based
on this information the species of the first group satisfy
requirement 4 and are considered as a recurrent group.

After checking the affinity table it is apparent

that S. cyclopteris is associated with M. macropleurus and

 

L; "rhomboidalis" of the recurrent group and is not asso-
<xiated with any other species. S. cyclopteris is considered,
tlierefore, as an associate of the recurrent group.

A secondary recurrent group contains R. oblata, M.

'£EEEJ A. "reticularis" and undifferentiated crinoid stems.

 

‘All species of the secondary recurrent group are associated

 

101

with one or more species of the basic recurrent group.
Figure 14 diagramatically shows the associations of all

the species.

Analysis of Species-Lithology Associations

The chi square test for independence was also used
to analyze species-lithology associations. Only those
species which showed a positive association with another
species were involved in this analysis. Those species not
showing an association with another species were excluded
because it is not certain whether their presence was due
to chance or transportation.

Even though several textural differences are
visible in polished sections from the different rock types,
they are generally not noticable on weathered surfaces at
the outcrop. Therefore, only five general lithologies were
recorded during the time of sampling. They are (l) lime-
stone, (2) chert, (3) shaly limestone, (4) siliceous lime-
stone, and (5) limestone with chert nodules or small chert
lenses.

Columns 35 through 39 represented the five litholo—
gies on the data cards. A one was punched in the appro-
priate column for the particular lithology that coincided
\vith the sample lines.

The same computer program which was used to gen-
earate contingency tables and compute chi square values in
éuialyzing species associations was utilized in analyzing

Species-lithology associations.

102

S. cyclopterus

  
 

Streptelasma—-——————————— Stropheodonta
/ I

 

Macropleura Leptaena

  
  

flaw—is

Crinoid stems

f //
Trematospira

Figure 14.--Species associations in the New Scotland
Formation. Lines indicate significant
associations.

103

Before a species was considered to be positively
associated with a particular lithology the same require-
ments had to be met as those designated for determining
positive species associations. However, a 0.10 level of

significance (x2 for 1 degree of freedom = 2.71) was

.90
used rather than a 0.05 level of significance. Since
several textural differences, which are not noticeable
at the outcrop, occur for each lithology it was decided
to use a larger level of significance.

Of the eleven species concerned in this portion of
the study, all except S. strictum have a positive associa-

tion with limestone at the 0.10 level of significance.

S. strictum is, however, positively associated with lime-

 

stone beds containing chert nodules or lenses at the 0.10
level of significance. R. oblata, A. "reticularis," M.

lata, D. perlamellosus, and M. macropleurus are also posi-

 

tively associated with limestone beds containing small
nodules or lenses of chert at the 0.10 level of signifi-
cance. The fact that all species with the exception of

S. strictum have a positive association with limestones

 

suggests that they favored a lime mud substrate. ‘S.
strictum was, however, always found in the limestone facies
of the beds. Therefore, S. strictum probably favored a
lime mud substrate also.

All concerned species are negatively associated
with beds or large lenses of chert at the 0.10 level of

significance. This fact could be explained by either

 

 

104

environmental or diagenetic factors. If the chert was a
result of primary precipitation the environmental condi-
tions could possibly have been such that the organisms did
not live in the vicinity during deposition. Outlines of
some fossils were occasionally visible in the chert beds
or lenses. Some shells could have been transported into
the area of precipitation and deposited or trapped in the
silica gel. But, if the chert is a result of replacement
the diagenetic processes could have partially or totally
obliterated most of the shell material during replacement.
As mentioned previously, a replacement origin is favored
for the occurrence of chert beds, lenses, and nodules.

On this basis the negative association between the species
and chert is probably due to diagenetic processes. The
negative association could be due to sampling. If more
samples had coincided with chert beds a negative associa-
tion may not have resulted.

None of the species are associated with siliceous
limestone beds at the 0.10 level of significance. Based
on these samples it is not possible to say whether the
occurrence of the concerned species in siliceous limestone
horizons is due to environmental factors, transportation
or chance.

8. strictum, R. oblata, A. "reticularis," M. lata,

 

 

D.pperlamellosus, and M. macropleurus are negatively asso-

 

 

ciated with shaley limestones. This negative association

probably indicates that these species preferred another

105

type of substratum. The other species are not associated

with shaly limestone.

Species Diversity

 

From the analysis of species associations and
recurrent groups it is not apparent whether the fossil
species are homogeneously distributed or not in the New [
Scotland Formation. At present, we know that the number
of species varies from one organic community to another.

By making two assumptions it is possible to evaluate the

 

complexities of species distribution in the New Scotland
Formation using the concept of species diversity. First,
one assumes that those fossils which are positively asso-
ciated now occur, at or near their original habitat.
Secondly, each outcrop represents a portion of an ancient
homogeneous, mixed population or community center.
According to Margalef (1957) the distribution of
individuals by species is related to a definite corres-
pondence between the total number of individuals and the
total number of species, and the relationship between the
number of species and the number of individuals varies
according to the type of distribution as the size of the
sample increases. Several empirical mathematical expres-
sions have been proposed to describe the distribution of
individuals by species. Frequently quoted expressions
found in biological literature are the "eometric progres-
sion rule" (Yoshirata, 1951), the "lognormal distribution"

(Preston, 1948), the "logarithmic series" (Fisher, Corbert,

106

and Williams, 1943) and the indices based on information
theory (Margalef, 1957). The parameter obtained from any
of these mathematical expressions is called an index of
diversity which represents the wealth of species in a
given organic community. Margalef (1957) indicates that
an index of diversity must be independent of the sample
size and the data must be from a homogeneous, mixed popu-
lation or community.

An index of diversity was calculated for each
outcrop, assuming that each outcrop represented a center
or near center of an ancient homogeneous, mixed organic
community, using the logarithmic series which was proposed
by Fisher, Corbert and Williams (1943). Margalef (1957)
indicates that the logarithmic series is a good first
approximation of species diversity. The equation used

in obtaining the diversity value for each outcrop is

d = (S - l)/1nN

where d is the index of diversity, S represents the number
of species, and 1nN represents the natural logarithm of

the number of individuals.

Species Diversity Map

As soon as the index of species diversity has been
computed for each sampling location, these values can be
recorded next to their respective control points on a map.
Isopleths can be drawn through points having equal species

diversity values. These isopleths can also represent

107

ecotones or boundaries between different natural communi-
ties. In this study a contour interval of 0.5 was arbi-

trarily used.

Results

Figure 15 shows the spatial distribution of the
index of diversity of associated species computed from
data on all sample lines at each outcrop of the New Scot-
land Formation. Two isopleths or ecotones are present
which separate three fossil communities. Due to the
limited number of favorable outcrops for this type of
study the actual position of the ecotone has to be inferred
at some localities. The two ecotones appear to be parallel
to sub-parallel with each other and display an undulant
northeast-southwest trend. The viersity gradient shows
a general increase from the northwest toward the south-
east.

The relative abundances, expressed as percentages,
of each associated species at each Outcrop is shown in
Table 4. The western-most faunal community is character-
ized by an abundance of the strophomenid brachipod,
Schellwienella woolworthana. Spirifers and a strophomenid,
Macropleura macropleurus, Meristella lata, and S. wool-
worthana, are distinctive fauna of the eastern-most faunal
community. The intermediate faunal community between the
eastern- and western-most communities is characterized by
M. macropleurus, S. woolworthana, and Leptaena

"rhomboidalis."

 

 

 

108

 

3. W

 

 

    

 

 

 

 

 

 

 

 

 

 

 

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109

 

 

 

 

 

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110

Environmental Significance

 

The concept of species diversity is a means of
evaluating quantitatively the degree of structural com-
plexity of each type of community (Margalef, 1957). A
large diversity value indicates a faunal community with
a high degree of structural complexity. The more com-
plex a community is, as suggested by larger index of
diversity values, the more stability that community has
attained (MacArthur, 1955). The stability of a given
community is a function of the number of species inter-
actions (MacArthur, 1955) and the presence of favorable
physical environmental conditions (Odum and others, 1960).

The species diversity map indicates the variation
of computed species diversity indices of associated
species present. Hypothetical ecotones delineate those
areas which possibly had similar environmental conditions.
Before any conclusions can be drawn from species diversity
.concepts, one should consider whether it is possible for
two different areas or outcrops to have similar species
diversity values but have entirely different species
which demand different physical environmental conditions.
After checking Table 4 it is apparent that most outcrops
in each given fossil community are characterized by the
same particular combination of species. Therefore, this
does not appear to be a problem. However, certain species
appear to be concentrated in a given area and this may

represent a transported assemblage of fossils rather than

 

 

111

a native population of organisms peculiar to that environ-
ment. Figure 16 is a scatter plot on which are plotted

the percentage of disarticulation and fragmentation (hori-
zontal axis) and the indices of species diversity (vertical
axis). The correlation coefficient value for this data is
0.43 which is not significant at the 0.05 level of signifi-
cance. Therefore, it may be possible to obtain a high
percentage of disarticulated shell material in some loca-
tions, and have only a few, if any, of the shells trans-
ported. Also, since the species diversity values were
computed from those species showing a positive association
with one another and associations were determined by the

x2 statistic using data from random sample lines in each
outcrop of the study area, the likelihood of the indices

of diversity being affected by transport and depositional
conditions should be small.

Another possibility is that some areas have had more
favorable conditions for the preservation of shell material
than others. No foolproof method exists for evaluating
this problem. However, as mentioned in the section con-
cerning petrography and petrology of New Scotland rocks,
there is a high degree of similarity with respect to
lithology and textures between any two outcrops in the
study area, even though each individual outcrop shows some
heterogeneity of lithology and texture in both vertical
and lateral directions. This similarity of lithology

and textures between outcrOps suggests that depositional

 

112

 

 

3c—

.5"

.5.) o e (c)

“2- o

8 0 o

-H

D

3 O o

-H

O

(D

63‘ O

“.4

O

X

(D

'2-

H 1“
I I f I I
20 4o 60 80 100

Percent Fossil Fragmentation or Disarticulation

Figure l6.--Percent fossil fragmentation or disarticulation
versus index of species diversity.

113

and post-depositional conditions were similar for the pre-
servation of shell material.

On a larger scale, the index of species diversity
in tropical regions at the present time is large compared
with that of cooler climatic regions (Fischer, 1961).
Superimposed on this hemispheric or worldwide diversity
gradient are more localized gradients such as those deter-
mined from sampling supratidal through an open marine
environment. There is a general increase in the diversity
index from supratidal environmentsthrough sublittoral
environments followed by a decrease in deeper environments
for benthonic organisms (Tappan, 1960; Odum and others,
1960; and Ager, 1963).

It is doubtful if any correlation between the dis-
tribution of ecotones and paleo latitudes can be estab-
lished from the species diversity map. (See Figure 15.)
However, there is a good correlation between the overall
trend of the New Scotland ecotones of this study and the
axis of the Devonian depositional basin in this area
defined by Woodward (1943). The pattern and distribution
of the ecotones may represent irregularities in the basin
floor, the geometry of the basin of deposition, and vary-
ing ecological conditions within the basin.

Of the many physical and biological factors con-
trolling the diversity of species there are three which
can be evaluated with respect to a paleoenvironment. These

factors are (l) depth of water, (2) proportion of mud

114

content which is a function of current velocity or proximity
to shore and (3) gross salinity.

With respect to water depth low species diversity
values can be interpreted two different ways. Low species
diversity values can represent either the outcrops (samp-
ling stations) were near the vicinity of the littoral-
supralittoral zones or near the edge of the basinal zone. a

If the outcrops with low species diversity values show a

 

paucity of desiccation features, algal laminations, colites, .
cross-bedding, and high degrees of sorting this suggests '
that the outcrops were not near the vicinity of ancient
littoral-supralittoral zones. With the exception of one

thin bed of cross-bedded crinoidal limestone in the Bull

Pasture Mountain section none of these sedimentational

features were observed in sections of the New Scotland

Formation used in evaluating species diversity. On this

basis those outcrops with lower indices of species diver-

sity were not in the vicinity of Helderberg littoral-

supralittoral zones. The presence of occasional tabulate

corals (Favosites species) and ramose or encrusting

 

bryozoan species showing growth orientations in some of
the sections with low diversity values suggest, however,
that water depth was not excessive. Therefore, it is
questionable if those sections showing lower indices of
Species diversity can be analogous to modern environments
near the edge of the outer sublittoral zones. Since some

fossil entities suggest that New Scotland sediments were

115

deposited in a shallow epicontinental marine environment,
local irregularities of the basin floor in a sublittoral
zone could have possibly altered current conditions and
produced slight environmental differences favorable for
larger populations of some species. Areas where environ-
mental conditions favored larger populations of certain
types of species would show lower species diversity values
than other areas with less favorable conditions, even
though the same types of species occur in both areas.
Purdy (1962 and 1964) suggests that distribution
patterns of aquatic benthos can be correlated with the
amount of mud content in a given sedimentary deposit. It
is conjectured that most epifaunal benthos, especially
brachiopods (Rudwick, 1965) prefer a stable substrate.
Substrates with lower proportions of mud content are less
stable (Purdy, 1964), but there probably is an upper limit
to the amount of mud a sediment can contain and still sup-
port epifaunal benthos. Table 5 shows the relationship
between the percentage of mud (micrite) content and indices
of species diversity for each outcrop of the New Scotland
Formation. The linear regression equation for this data
as computed by the least squares method, is YX = 2.223 -
0.0112X and the value of the correlation coefficient is
-0.41 which is not significant at the 0.10 level of signi-
ficance. Since there is a possibility that the data was
not from a population with a normal distribution a rank

correlation coefficient was also calculated. The value of

 

116

TABLE 5.--Relationship between the amount of lime mud and
the index of species diversity in the New Scotland

 

 

 

 

Formation.
Index of
Percent Species Rank Rank 2
Outcrop Lime Mud Diversity Mud Index d d
New Creek II 65.83 1.66 3 9 -6 36
New Creek I 79.67 1.43 l 10 -9 81
Maysville Gap 60.07 1.98 4 5 -l 1
Smoke Hole
Cavern 66.17 2.14 2 3 -1 1
Rocks 53.44 2.13 7 4 3 9
Trinity Road 59.83 1.95 5 6 -l l
Thrasher
Springs School 42.67 1.70 10 8 2 4
Petersburg Gap 53.00 2.27 8 l 7 49
Hively Gap 57.11 1.93 6 7 -l l
Monterey 48.85 2.15 9 2 7 49
ZdZ=232
Note:

d = difference between index rank and mud rank
percent lime mud includes microcrystalline calcite and
microsparry calcite.

Rank Correlation Coefficient

_ _ 2
rank — 1 6 2d /N(N2-l)

l - 6(232)/10(99)

1 - 1.406

= -0.406 not significant at a = 0.10

117

the rank correlation coefficient is -0.19 which is also
not significant at the 0.10 level of significance. Even
though the correlation coefficient and the rank correla-
tion coefficient do not suggest a statistically significant
relationship between the indices of species diversity and
mud content a general linear trend occurs for these data
which is somewhat similar to that obtained by Sanders
(1958) for suspension feeders and their relationship to
substrate, in that both show a negative slope. A negative
slope for the regression curve is not surprising because
most of the species involved in calculating the indices

of species diversity are brachiopods, which are suspension
feeders.

Based on this regression curve there is a possibi-
lity that certain benthonic assemblages can be recognized
at higher taxonomic levels which show a relationship to
amount of mud contained in a given rock unit. Rudwick
(1965) suggests that most strophomenids were capable of
inhabiting soft muddy substrates whereas most other orders
of articulate brachiopods inhabited firmer substrates.
Table 6 shows the relationship between the percentage of
micrite and the ratio of spirifers and orthids to strop-
homenids. The value of the rank correlation coefficient
for this relationship is -0.509 which is significant at
the 0.10 level of significance. When the values for the
ratios of spirifer-orthid/strophomenid and percent micrite

are plotted on a graph (see Figure 17) there is a general

 

118

TABLE 6.--Relationship between the amount of lime mud and
the brachiopod ratio in the New Scotland

 

 

 

Formation.

Percent Brachio- Rank Rank 2
Outcrop lime mud pod ratio mud ratio d d
New Creek II 65.83 1.54 3 7 -4 16
New Creek I 79.67 0.75 l 10 -9 81
Maysville Gap 60.07 1.03 4 9 -5 25
Smoke Hole Cavern 66.17 2.00 2 3 -l l
Rocks 53.44 1.20 7 8 -1 1
Trinity Road 59.83 1.93 5 5 0 0

Thrasher
Springs School 42.67 3.13 10 l 9 81
Petersburg Gap 53.00 2.75 8 2 6 36
Hively Gap 57.11 1.94 6 4 2 4
Monterey 48.85 1.89 9 6 3 9
{d2=254

Note:

Percent lime mud includes microcrystalline calcite and
microsparry calcite.

Brachiopod ratio is equal to number of spirifers plus
number of orthids divided by number of strophomenids.

d = difference between ratio rank and mud rank.

Rank correlation coefficient 1-6 ZdZ/N(N2-1)

1 - 6(254)/10(99)

-0.539 significant at 0.068d

 

119

3-1

 

90

Ratio of Spirifers and orthids to strophomenids

 

 

l I I l I
20 40 60 80 100

Percent Microcrystalline Calcite and Microsparry
Calcite

B‘igure l7.--Percent microcrystalline calcite and microsparry
calcite versus ratio of spirifers and orthids to
strophomenids.

120

negative trend of the data points. From an environmental
standpoint this could possibly mean that those areas with
larger prOportions of fine grained sediments making up
the substrate supported larger populations of strophomenids
than other areas with lower percentages of fine grained
sediments in the substrate.

Differences in species diversity values may be
due to extreme differences of water salinity in different
portions of the basin. Odum and others (1960) have been
able to show from a study in the coastal region of the
Gulf of Mexico that higher saline water bodies have lower
indices of species diversity than normal marine water
bodies. The absence of dolomitic or gypsiferous beds,
collapse structures, or salt crystal imprints in any of
the New Scotland outcrops of the study area suggest that
environmental conditions were more open marine rather than

Jhypersaline or hyposaline during deposition.

 

CHAPTER VI

PALEOENVIRONMENTAL SYNTHESIS

Viewed from a fossil faunal standpoint the sedi-
ments of the Helderberg Group were deposited in a marine
environment (Woodward, 1943). It is possible, however,
to further define the depositional environment by com-
bining petrographic, paleontologic, and stratigraphic
evidence. The lithologic and fossil faunal attributes
are indicative of specific environments; whereas, the
temporal and spatial distributions of the various rocks
types are indicative of the areal arrangement of these
differing environments at any given time.

In any vertical sequence the Helderberg Group can
be subdivided into several smaller stratigraphic units on
the basis of lithologic and paleontologic differences.
Different rock types or faunal content suggest that
depositional conditions changed with time.

The different rock types could be due to mineralo-
gical differences, but since the Helderberg Group is pre-

<flominantly a carbonate unit in the study area most of the

121

 

122

differences are textural ones. As indicated previously,
textural differences in carbonate rocks are due primarily
to varying proportions of rock components. Figure 18 shows
the variation of the rock components plus any significant
mineralogical changes displayed in any outcrop containing
lithologies typical to each of the Helderberg units.
Admittedly there are more compositional variations within
a given formation than this diagram depicts, but there are
definite trends of textural or lithologic changes from
lower to upper Helderberg units in all outcrops of the
study area. The most significant aspect of this, with
regard to depositional environment, is the varying propor-
tions of microcrystalline calcite contained in the various
stratigraphic units. The sediments of those units con-
taining larger amounts of microcrystalline calcite were
probably deposited in areas lacking persistent strong
currents.

In a vertical section there is also a general
increase in the variety of species occurring in the Helder-
berg units, particularly from the basal units through the
New Scotland interval. Few fossils occur in the uppermost
micritic beds of the Keyser Limestone. The Coeymans Lime-
stone is characterized by tabulate corals, bryozoa,
pelmatozoan debris, and some brachiopods. Spiriferid and
strophomenid brachiopods are the dominant fossils of typi-
cal New Scotland beds. Fossils are not too common in the

Shriver Chert or Licking Creek Limestone.

 

 

123

 

 

 

 

 

Helderberg Group.

r----\‘ .w”'----—--‘--- I.--—
\\""_—-
Fossils
L._ --
\\ _.
\ /\
\\ / \
/ \
\\ / \ /
\ / \
’ /’\\ \ //
. . /
Microcrystalline / I \ \y/
Calcite , ’ “\V
\i‘\ [I/ W
2 \
I
/ Sparry \
/
,r Calcite \
\
\
\
/
/
/
/
________ x
New Scotland Coeymans Keyser

 

Figure 18.--Vertical variation of rock components in the

100

80

60

40

20

 

 

124

A reevaluation of the vertical and lateral rela—
tionships of the Helderberg units reveals that these units
are rock-stratigraphic rather than time-stratigraphic
units. Therefore, a stratigraphic unit overlying another
unit in a vertical section grades laterally into a subja-
cent or superjacent unit in another section, and time lines
cut through facies. This also indicates that sediments of
the various rock-stratigraphic units were probably deposited
simultaneously under differing environmental conditions in
different parts of the depositional basin. Also, an
analysis of several stratigraphic cross-sections strongly
suggests that Helderberg sediments were deposited overall
in a transgressive sea.

If the stratigraphic units observed in a vertical
section actually grade laterally into subjacent or super-
jacent units and the various units are recognizable through
lithologic or textural differences that developed during
deposition in different depositional environments, then
the various rock components of these units should, at any
given time, show distributional patterns similar to those
observed in a vertical section. Figure 19 shows the
lateral variation of the average proportions for the
various rock components plus any other minerals of some
environmental significance observed in samples that
correspond to a given time line. The lateral distributional
pattern for the various rock components of the Helderberg

units is very similar to that observed in a vertical section

125

II.

 

.msouu mumnnmcamm map cw mucmsomsoo xoou mo coflumanm> Hmumpmqnl.ma musmwm

 

OOI

 

  

muwoamu
huummm

 
    

muwoamo
mcwHaMDmmHoouoflz

 

mawmmom

wumnmmozm p24

 

/

//

 

.Hmwnmume.cmmuo .Nunmso

 

 

 

 

V

 

mmumucoz mow new
>Hm>wm mnsnmnwuwm

Hoonom mxoom.
mmcwumm
Hmnmmuna

126

(compare Figures 18 and 19). This further substantiates
the conclusions concerning the vertical and lateral rela-
tionships among the various Helderberg units. It also
indicates that sediments of the various stratigraphic units
were deposited simultaneously in different depositional
environments at any given time.

The number of species varies laterally from one F1
stratigraphic unit to another at any given time. Though L

a detailed analysis of lateral variations of species

 

diversity was restricted to the limestone and chert facies *7
of the New Scotland Formation, a rock-stratigraphic unit,
this study indicates that there is a definite northeast-
southwest regional trend of species diversity which is of
environmental significance.

If lithologic or paleontologic aspects of at least
one stratigraphic unit are indicative of a given deposi-
tional environment, this unit can be used as a starting
point in reconstructing the overall regional distribution
of depositional environments at any given time.

The uppermost, micritic beds of the Keyser Lime-
stone suggest that these sediments were deposited in an
environment lacking persistent strong currents. Since
many of the bedding surfaces of these rocks display mud-
cracked surfaces this further suggests that the sediments
were deposited in a supratidal, carbonate mud-flat envir-
onment. Therefore, the uppermost Keyser beds offer

enough information to make logical inferences concerning

127

the direction or directions of possible environmental
gradients.

Sediments of the Coeymans Limestone were deposited
in an area where currents were rather intense and per—
sistent. This is based on the fact that the units consist
of biosparitic packstones and grainstones predominantly.
These rock types infer deposition in relatively well
agitated water. Since the Coeymans Limestone was deposited
laterally adjacent to the Keyser Limestone this indicates

that Coeymans sediments are representative of an inner

 

shelf environment adjacent to the carbonate mud-flat. This
type of deposition would primarily occur below low tide
(subtidal) but above wave base.

The New Scotland Formation is laterally adjacent
to the Coeymans Limestone. Sediments of the limestone
and chert facies were deposited in somewhat calmer water
conditions than those of the Coeymans. This is based on
the fact that the units consist of wackestones predomi-
nantly. From an environmental standpoint these sediments
represent an outer shelf environment which would be sub-
tidal also but below wave base.

Sediments of the crinoidal limestone facies and
the crinoidal bearing, quartzose sandstone facies of the
New Scotland Formation were deposited under conditons
similar to that associated with Coeymans deposition. This
is based on the basic textural and structural similarity

of these different stratigraphic units.

128

Sediments of the Shriver Chert were deposited in
a more distal location with respect to the carbonate mud
flat than those of the New Scotland Formation. They are
representative of a slope environment as shown by slump
structures observed in the outcrops. This type of sedi-
mentary structure is common in slope deposits (Thomson
and Thomasson, 1969).

The sediments of the Licking Creek Limestone were
probably deposited under conditions similar to those
associated with deposition of the limestone and chert
facies. This is indicated by the lithologic similarity
of the rocks comprising these two stratigraphic units and
the lateral relationship between the Licking Creek Lime-
stone and the crinoidal limestone facies of the New Scot-
land Formation.

The paleontologic aspects of Helderberg rocks
further substantiate the preceding conclusions concerning
the various depositional environments. Purdy (1964)
indicates that the number of species occupying the shoal-
ing (tidal) zone is less than that occurring in the outer
platform of the Great Bahama Bank. Similar relationships
occur between the Coeymans Limestone and the limestone
and chert facies of the New Scotland Formation. Also, the
limestone and chert beds display more evidence for biotur-
bation than any other Helderberg unit. This corresponds
with the conclusions of Moore and Scruton (1957) that

Jourrowing activity increases offshore in the Gulf Coast region.

129

A summary of the depositional environments which
occurred during deposition of Helderberg sediments is
shown by Figure 20. The different rock types, sedimentary
structures, and faunal assemblages which served as possible
indicators for the different environmental conditions are

also noted on this figure.

 

 

Oriskany
gandatorie _.

_- --—l

Shriver Chert

New Scotland
Formation

————————_

Upper Member of
Coeymans Limestone

_——-_ ——-_‘

 

Middle Member of
Coeymans Limestone

Lower Member of
Coeymans Limestone

 

 

 

 

Uppermost beds
of the
Keyser Limestone
__-____ --_______.__-2_______l”____-_._.n_
. m m
Formation > >
a r4 m m
m m 3 3 H
p U m m m
-:--i H (DU) 302 G
4J 4J >rd 0rd "4
m H 0;) FhQ m
H m .Q m m
Q4 JJ KI! m m
figositional s s ,
ironment m H Subtidal

 

 

 

 

 

 

Figure 20.-!Interpretation of depositional environments of
the Helderberg Group in Virginia and West
Virginia.

CHAPTER VII

CONCLUSIONS

The principal conclusions derived from this inves-
tigation are as follows:

1. In outcrops north of Monterey, Virginia the
Coeymans Limestone can be subdivided into three members:
(a) a lower limestone member, (b) a middle limestone mem-
ber, and (c) an upper limestone member.

2. The middle limestone member is a thin-bedded,
finely crystalline, crinoidal limestone with chert nodules

and lenses. G. coeymanensis is restricted to the basal

 

beds of the member. The member shows a general thinning
from north to south.

3. The midinterval of the middle limestone member
of the Coeymans Limestone appears to represent a time
plane.

4. Evidence is lacking to indicate that the
depositional basin was significantly deformed by any tec-
tonic events during deposition of Helderberg sediments.

5. The formations comprising the Helderberg Group

are rock-stratigraphic units rather than time-stratigraphic

131

 

132

units and overall the group represents a transgressive
phase of deposition during early Devonian time in West
Virginia and Virginia.

6. Calcite, quartz, illite(?), and chert are the
dominant mineral components of all Helderberg rock types.
Dolomite, collophane, tourmaline, feldspar, zircon, and
organic material occur in some samples as accessory com-
ponents.

7. Based on the type of grain support and the pro-
portion of grains, matrix, and cement the following car-
bonate rock types can be recognized in the Helderberg
Group: micrite, biomicritic wackestone, biomicritic pack-
stone, biosparitic packstone, biosparitic grainstone,
pelsparitic grainstone, and intrasparitic grainstone.

8. Petrographic evidence suggests that most of
the sparry calcite occurring in Helderberg samples repre—
sents a primary pore filling cement. However, some sparry
calcite resulted from recrystallization of microcrystal-
line calcite or from inversion of an original aragonite
cement.

9. Petrographic evidence suggests that micro-
sparry calcite represents recrystallized grains of micro-
crystalline calcite.

. 10. Field and petrographic evidence suggest that
most of the chert occurring in the Helderberg units is of

a replacement origin.

133

ll. Thirty-three environmentally significant
interspecific fossil associations involving ten of 34
fossil species identified in the New Scotland Formation
can be recognized by the chi square test for independence,
even though field observations suggest that most of the
fossils had been transported or reworked to some degree.

12. The associations can be grouped into a pri-
mary recurrent group and a related secondary recurrent
group, which may be indicative of the original structure

of the biocenoses.

 

13. All species showing an association with

another species with the exception of S. strictum have a

 

positive association with limestone. This suggests that
they favored a lime mud substrate.

14. All associated species are negatively asso-
ciated with beds or lenses of chert. This type of asso-
ciation suggests that the occurrence of chert in the New
Scotland Formation is possible a replacement phenomenon.

15. The spatial distribution of the computed
indices of species diversity suggest that three fossil
communities possibly existed during deposition of New
Scotland sediments and the communities had an undulant
northeast-southwest trend. There is a general increase
from northwest to southeast in the species diversity
gradient.

16. Even though there is not a statistically

significant relationship between the indices of species

134

diversity and the mud content in the New Scotland Forma-
tion there is a general negative linear trend of the data.
This is not surprising since brachiopods are the dominant
New Scotland fossils and they were suspension feeders.

17. Depositional sights which experienced larger
accumulations of fine grained sediments generally supported
larger pOpulations of strophomenids than other areas during
deposition of New Scotland sediments.

18. A stratigraphic unit overlying another unit
in a Helderberg outcrop grades laterally into a subjacent
or superjacent unit in another section and the sediments
of the various rock-stratigraphic units were deposited
simultaneously under differing environmental conditions
in different parts of the depositional basin.

19. Field and petrographic evidence suggest that
the micritic beds of the upper Keyser Limestone were
deposited in a supratidal, mud-flat environment.

20. Stratigraphic, paleontologic, and petro-
graphic evidences indicate that micrite and wackestone
beds of the New Scotland Formation and the Shriver-Chert-
Licking Creek Limestone interval were deposited in an
open marine environment probably below wave base.

21. Stratigraphic and petrographic evidence suggest
the packstone and grainstone beds comprising the Coeymans
Limestone, the crinoidal limestone and sandstone facies
of the New Scotland Formation were deposited in a high

energy environment such as a marginal or beach deposit.

 

 

CHAPTER VIII

SUGGESTIONS FOR FURTHER RESEARCH

During the final stages of this investigation it
was realized that fossil data were collected in such a way
that they could be used to analyze just the lateral varia-
tions of fossil distributions. If the fossil data had
been collected in such a way that the temporal variations
of fossil distributions could be evaluated then this addi-
tional information might further define the depositional
history of the Helderberg Group in the study area.

A study of the relationship, if any, of the reef
horizons in the upper Keyser Limestone and the Coeymans-
New Scotland stratigraphic couple might also bring to
light additional information that would further define the
geometry and topography of the depositional basin for the

Helderberg Group in the study area.

135

l

BIBLIOGRAPHY

136

BIBLIOGRAPHY

Ager, D. V., 1963, Principles of paleoecology: New York,
McGraw—Hill, 371 p.

Alling, H. L. and Briggs, L. I., 1961, Stratigraphy of
Upper Silurian Cayugan evaporties: Am. Assoc.
Petroleum Geologists Bull., vol. 45, pp. 515-547.

Bathurst, R. G. C., 1958, Diagenetic fabrics in some
British Dinantian limestone: Liverpoor and Man-
chester Ceol. Jour., vol. 2, pp. 11-36.

 

Beerbower, J. R., 1957, Paleoecology of the Centerfield
coral zones, East Stroudsburg locality, Monroe
County, Pennsylvania: Pa. Acad. Sci. Proc., vol.
31, pp. 91-97.

Beerbower, J. R. and McDowell, F. W., 1960, The Centerfield
biostrome: An approach to a paleoecologic problem:
Pa. Acad. Sci. Proc., vol. 34, pp. 84-91.

Berdan, J. M., 1964, The Helderberg Group and the position
of the Silurian-Devonian boundary in North America:
U. S. Geol. Survey Bull. 1180-B, Contributions to
stratigraphic paleontology, pp. Bl-B19.

Berner, R. A., 1966, Chemical diagenesis of some modern
carbonate sediments: Am. Jour. Sci., vol. 264,
pp. 1-36.

Black, M., 1933, The precipitation of calcium carbonate
on the Great Bahama Bank: Geol. Mag., vol. LXX,
pp. 455-460.

Boucot, A. J. and Johnson, J. G., 1967, Paleogeography and
correlation of Appalachian province Lower Devonian
sedimentary rocks, i3 Toorney, D. F., ed., Silur-
ian-Devonian rocks of Oklahoma and environs,
Symposium: Tulsa Geol. Soc. Digest, vol. 35,
pp. 35-87.

137

138

Bowen, Z. P., 1967, Brachiopoda of the Keyser Limestone
(Silurian-Devonian) of Maryland and adjacent
areas: Geol. Soc. America Mem. 102.

Braun-Blanquet, J., 1932, Plant sociology; trans. by
G. D. Fuller and H. S. Conrad: New York, McGraw—
Hill.

Bretsky, P. W., 1970, Upper Ordovician ecology of the
central Appalachians Yale Univ. Peabody Mus. of
Nat. Hist. Bull. 34, 150p.

Butts, Charles, 1940, Geology of the Appalachian Valley
in Virginia: Va. Geol. Survey Bull. 52, pt. I,
568 p.

Cain, S. A., 1938, The species-area curve: The American
Midland Naturalist, vol. 19, pp. 573-581.

Chadwick, G. H., 1908, Revision of "the New York Series":
Science, n. 5., vol. 28, pp. 346-348.

Chayes, Felix, 1949, A simple point counter for thin
section analysis: Am. Mineralogist, vol. 34,
pp. l-ll.

, 1956, Petrographic modal analysis - An elementary
statistical appraisal: New York, John Wiley and
Sons, Inc.

Clarke, J. M., 1889, The Hercynian question: New York
State Mus. 42d Ann. Rept., pp. 408-437; New York
State Geologist 8th Ann. Rept., pp. 62-91.

Clarke, J. M. and Schuchert, Charles, 1899, The nomencla-
ture of the New York series of geological forma-
tions: Science, n.d., vol. 10, pp. 874-878.

Chave, K. E., 1964, Skeletal durability and preservation,
i3 Imbrie, John and Newell, N. D., eds., Approaches
to paleoecology: New York, John Wiley and Sons,
Inc., pp. 377-387.

Cloud, P. E., Jr., 1951, Geology of Saipan, Mariana
Islands, part 4, Submarine topography and shoal
water ecology: U. S. Geol. Survey Prof. Pap.
280K, pp. 361-445.

, 1962, Environment of calcium carbonate deposition
west of Andros Island, Bahamas: U. S. Geol. Sur-
vey Prof. Pap. 350, 138p.

 

139

Cochran, W. G., 1954, Some methods for strengthening the
common chi-square tests: Biometrics, vol. 10,
p. 417.

Cole, L. C., 1949, The measure of interspecific association:
EcologY, vol. 30, pp. 411-424.

Conrad, T. A., 1829, Second annual report on the paleonto-
lOgical department of the Survey: New York State
Geol. Survey 3d Ann. Rept., pp. 57-66.

Cooper, G. A., Butts, C., Caster, K. E., Chadwick, G. H.,
Goldring, W., Kindle, E. M., Kirk, E., Merriam,
C. W., Swartz, F. M., Warren, P. S., Warthin, A. S.,
and Willard, B., 1942, Correlation of the Devonian
sedimentary formations of North America: Geol.
Soc. America Bull., vol. 53, pp. 1729-1794.

 

Cotter, Edward, 1966, Limestone diagenesis and dolomitiza-
tion in Mississippian carbonate banks in Montana:
Jour. of Sedimentary Petrology, vol. 36, pp. 764-774.

Craig, G. Y., 1954, The paleoecology of the Top Hoise Shale
(Lower Carboniferous) at a locality near Kilsyth:
Quart. Jour. Geol. Soc. London, vol. 110, pp. 103-
119.

Dunham, R. J., 1962, Classification of carbonate rocks
according to depositional texture, i2 Ham, W., ed.,
Classification of carbonate rocks: Am. Assoc.
Petroleum Geologists Mem. 1, pp. 108-121.

Dennison, J. M., 1961, Stratigraphy of Onesquethaw Stage
of Devonian in West Virginia and bordering states:
W. Va. Geol. Survey Bull. 22, 87 p.

Dixon, W. J. and Massey, F. J., Jr., 1957, Introduction to
statistical analysis: New York, McGraw-Hill,
2nd ed., 488p.

Donaldson, A. C., 1960, Interpretation of depositional
environments of Lower Ordovician carbonates in
central Appalachians: W. Va. Acad. Sci. Proc.,
vol. 32, pp. 153-161.

Ellison, R. L., 1963, Faunas of the Mahantango Formation in
southcentral Pennsylvania: Pa. Geol. Survey Bull.
G39, pp. 201-212.

Epstein, A. G., Epstein, J. B., Spink, W. J., and Jennings,
D. S., 1967, Upper Silurian and Lower Devonian
stratigraphy of northeastern Pennsylvania, New
Jersey, and southeasternmost New York: U. S. Geol.
Survey Bull. 1243, 75p.

140

Fager, E. W., 1957, Determination and analysis of recurrent
groups: Ecol., vol. 38, pp. 586-595.

Fairbridge, R. W., 1950, Recent and Pleistocene coral
reefs of Austrailia: Jour. Geol., vol. 58, pp.
330-401.

Fischer, A. G., 1961, Latitudinal variations in organic
diversity: Amer. Scientist, vol. 49, pp. 50-75.

Fisher, R. A., Corbert, A. S., and Williams, C. B., 1943,
The relation between the number of species and the
number of individuals in a random sample of animal
population: Jour. Animal Ecol., vol. 12, pp.
42-58.

Folk, R. L., 1959, Practical petrographic classification
of limestones: Am. Assoc. Petroleum Geologists
Bull., vol. 43, pp. l-38.

, 1960, Petrography and origin of the Tuscarora,
Rose Hill, and Keefer formations, Lower and
Middle Silurian of eastern West Virginia: Jour.
Sedimentary Petrology, vol. 30, pp. 1-58.

 

, 1962, Spectral subdivision of limestone types;
in Ham, W., ed., Classification of carbonate
rocks: Am. Assoc. Petroleum Geologists Mem. 1,
pp. 62-84.

 

Folk, R. L. and Robles, Rogelio, 1964, Carbonate sands of
Isla Perez, Alacran Reef Complex, Yucatan: Jour.
Geol., vol. 72, pp. 255-292.

Forbes, S. A., 1907, On the local distribution of certain
Illinois fishes: An essay in statistical ecology:
Ill. State Lab. Nat. Hist. Bull., vol. 7, pp.
273-303.

, 1925, Method of determining and measuring the
associative relations of species: Science, vol.
61, p. 524.

 

Force, L. M., 1969, Calcium carbonate size distribution
on the west Florida shelf and experimental studies
on the microarchitectural control of skeletal
breakdown: Jour. Sedimentary Petrology, vol. 39,
pp. 902-934.

Frank, R. M., 1965, An improved carbonate peel technique
for high-powered studies: Jour. Sedimentary
Petrology, vol. 35, pp. 499-500.

 

141

Garrison, R. E. and Fischer, A. G., 1969, Deep-water
limestones and radiolarites of the Alpine Jurassic;
in Friedman, G. M., ed., Depositional environments
in carbonate rocks: Soc. Econ. Paleontologists
and Mineralogists Spec. Pub. 14, pp. 20-55.

Gevirtz, J. L. and Friedman, G. M., 1966, Deep-sea car-
bonate sediments of the Red Sea and their impli-
cations on marine lithification: Jour. Sedimentary
Petrology: vol. 36, pp. 143-151.

Ginsburg, R. N., 1956, Environmental relationships of grain
size, Florida carbonate sediments: Am. Assoc.
Petroleum Geologists Bull., vol. 40, pp. 2384-2427.

, 1957, Early diagenesis and lithification of
shallow water carbonate sediments in south Florida,
in LeBlanc, R. J. and Breeding, J. G., eds.,
Regional aspects of carbonate deposition--a sympo-
sium: Soc. Econ. Paleontologists and Mineralogists
Spec. Pub. 5, pp. 80-99.

Ginsburg, R. N. and Lowenstam, H. A., 1958, The influence
of marine bottom communities on the depositional
environment of sediments: Jour. Geol., vol. 66,
pp. 310-318.

Greenfield, L. J., 1963, Metabolism and concentration of
calcium and magnesium and precipation of calcium
carbonates by a marine bacterium: New York Acad.
Sci. Annual., vol. 109, pp. 23-45.

Griffiths, J. C. and Rosenfeld, M. A., 1950, Progress in
measurement of grain orientation in Bradford Sand:
Pennsylvania State Univ. Min. Industry Expt. Sta.
Bull. 56, pp. 202-236.

Hall, James, 1859, Descriptions and figures of the organic
remains of the Lower Helderberg Group and the
Oriskany Sandstone: New York Geol. Survey,
Paleontology, Vol. 3, 532 p.

Hobbs, C. R. B., 1957, Petrography and origin of dolomite
bearing carbonate rocks of Ordovician age in
Virginia: Bull. Va. Polytechnic Inst., Eng. Expt.
Station ser, no. 116, pp. 5-127.

Illing, L. V., 1954, Bahaman calcareous sands: Am. Assoc.
Petroleum Geologists Bull., vol. 38, pp. 1-95.

Jaccard, P., 1908, Nouvelle recherches sur la distribution
florale: Bull. Soc. vaud. Sci. Nat., vol. 44,
pp. 223-270.

142

Johnson, J. H., 1951, An introduction to the study of
organic limestone: Colo. School of Mines Quart.,
vol. 46, n. 2, 185;.

Johnson, K. G., and Friedman, G. M., 1969, The Tully clastic
correlatives (Upper Devonian) of New York State:
A model for recognition of alluvial, dune(?),
tidal, nearshore (bar and lagoon), and offshore
sedimentary environments in a tectonic delta com-
plex: Jour. Sedimentary Petrology, vol. 39, pp.
451-485.

Johnson, R. G., 1962a, Interspecific associations in
Pennsylvanian fossil assemblages: Jour. Geol.,
vol. 70, pp. 32-55.

, 1962b, Mode of formation of marine fossil assemb-
lages of the Pleistoncene Millerton Formation of
California: Geol. Soc. America Bull., vol. 73,

pp. 113-130.

Krumbein, W. C. and 81053, L. L., 1963, Stratigraphy and
sedimentation, 2nd Ed.: San Francisco, W. H.
Freeman and Co., 660p.

Krynine, P. D., 1948, The megascopic study and field
classification of sedimentary rocks: Jour. Geol.,
vol. 56, pp. 130-165.

Lalou, Claude, 1957, Studies of bacterial precipitation of
carbonates in sea water: Jour. Sedimentary Petro-
logy, vol. 27, pp. 190-195.

Laporte, L. F., 1967, Carbonate deposition near mean sea-
level and resultant facies mosaic: Manlius Forma-
tion (Lower Devonian) of New York State: Am.
Assoc. Petroleum Geologists Bull., vol. 51, pp.
73-101.

, 1969, Recognition of a transgressive carbonate
sequence within an epeiric sea: Helderberg Group
(Lower Devonian) of New York State, in Friedman,
G. M., ed., Depositional environments in carbonate
rocks: Soc. Econ. Paleontologists and Mineralo-
gists Spec. Pub. 14, pp. 98-118.

Lesgold, A. M., 1967, Analysis of contingency tables, ACT
1.01, Technical Report No. 14: Michigan State
University, Computer Inst. for Social Science
Research, pp. 1-17.

Lowenstam, H. A., 1955, Aragonite needles secreted by algae
and some sedimentary implications: Jour. Sedimen-
tary Petrology, vol. 25, pp. 270-272.

 

 

143

MacArthur, R. H., 1955, Fluctuations of animal populations
and a measure of community stability: Ecol., vol.
36’ pp. 533-536.

McCue, J. B., Lucke, J. B., and Woodward, H. P., 1939,
Limestones of West Virginia: W. Va. Geol. Survey,
vol. 12, 560p.

McIntyre, G. A., 1953, Estimation of plant density using
line transects: Jour. Ecol., vol. 41, pp. 319-
330.

Margalef, D. R., 1957, Information theory in ecology:
Menorias de la Real Academmia de Ciencias y Artes
de Barcelona, vol. 23, pp. 373-449 (translated by
Wendell Hall in General Systems Yearbook), 1958,
vol. 3, pp. 37-71.

Matthews, R. K., 1966, Genesis of recent lime mud in
southern British Honduras: Jour. Sedimentary
Petrology, vol. 36, pp. 428-454.

 

Matter, Albert, 1967, Tidal flat deposits in the Ordovician
of western Maryland: Jour. Sedimentary Petrology,
vol. 37, pp. 601-609.

McKee, E. D., 1949, Geology of Kapingamarangi Atoll,
Caroline Islands, in Scientific investigations
in Micronesia: Pacific Sci. Board, National
Research Council.

Moore, D. G. and Scruton, P. C., 1957, Minor internal
structures of some recent unconsolidated sedi-
ments: Am. Assoc. Petroleum Geologists Bull.,
vol. 41, pp. 2723-2751.

Newell, N. D. and Rigby, J. K., 1957, Geological studies
on the Great Bahama Bank, in LeBlanc, R. J. and
Breeding, J. G., eds., Regional aspects of car-
bonate deposition--a symposium: Soc. Econ.
Paleontologists and Mineralogists Spec. Pub. 5,
pp. 15-72.

Newell, N. D., Rigby, J. K., Whiteman, A. J. and Bradley,
J. S., 1951, Shoal-water geology and environments,
eastern Andros Island, Bahamas: Am. Mus. Nat.
Hist. Bull., vol. 97, pp. 1-29.

Newell, N. D., Purdy, E. G., and Imbrie, John, 1960,
Bahamian ooliticsand: Jour. Geol., vol. 68,

 

144

Odum, H. T., Cantlon, J. E., and Kornicker, L. S., 1960,
An organizational hierarchy postulate for the
interpretation of species-individual distributions,
species, entropy, ecosystem evolution, and the
meaning of a species-variety index: Ecol., vol.
41, pp. 395-399.

Oppenheimer, C. H., 1961, Note on the formation of spheri-
cal aragonite bodies in the presence of bacteria
from the Bahama Bank: Geochim et Cosmochim Acta,
vol. 23, pp. 295-296.

Pelletier, B. R., 1958, Pocono paleocurrents in Pennsylvania
and Maryland: Geol. Soc. America Bull., vol. 69,
pp. 1033-1063.

Pettijohn, F. J., 1957, Sedimentary rocks, 2nd ed.: New
York, Harper and Brothers, 718p.

 

Potter, P. E. and Pettijohn, F. J., 1963, Paleocurrents
and basin analysis: Berlin, Springer-Verlag, 296p.

Preston, F. W., 1948, The commonness and rarity of species:
Ecol., vol. 29, pp. 254-283.

Purdy, E. G., 1962, Sediments as substrates (abs.): Geol.
Soc. America Spec. Paper 68, p. 249.

, 1964, Sediments as substrates, in Imbrie, John
and Newell, N. D., eds., Approaches to paleoecology:
New York, John Wiley and Sons, Inc., 432 p.

Rickard, C. V., 1962, Late Cayugan (Upper Silurian) and
Heldergergian (Lower Devonian) stratigraphy in
New York: New York State Mus. and Sci. Service
Vull. 386, 157p.

Rudwick, M. J. S., 1965, Ecoloyg and paleoecology, in
Moore, R. C., ed., Treatise on invertebrate
paleontology, Part H (Brachiopods), vol. 1, Geol.
Soc. America, pp. H199-H214.

Sanders, H. L., 1958, Benthonic studies in Buzzards Bay,
I; Animal-sediment relationships: Limm. and
Oceanogra., vol. 3, pp. 245-258.

Schuchert, Charles, 1900, Lower Devonic aspect of the
Helderberg and Oriskany formations: Geol. Soc.
America Bull., vol. 11, pp. 241-332.

, 1903, On the lower Devonic and Ontario formations
of Maryland: U. S. Natl. Mus. Proc., vol. 26,

145

Schuchert, Charles, Swartz, C. K., Maynard, T. P., and
Rowe, R. B., 1913, The Lower Devonian deposits of
Maryland, in Lower Devonian: Maryland Geol.

Survey, pp. 67-190.

Stockman, K. W., Ginsburg, R. N., and Shinn, E. A., 1967,
The production of lime mud by algae in south
Florida: Jour. Sedimentary Petrology, vol. 37,
pp. 633-648.

Stose, G. W. and Swartz, C. K., 1912, Description of the
Pawpaw and Hancock quadrangles, Maryland-West
Virginia-Pennsylvania: U. S. Geol. Survey Geol.
Atlas, Folio 179, 24p.

Swartz, F. M., 1929, The Helderberg Group of parts of West
Virginia and Virginia: U. S. Geol. Survey Prof.
Pap. 158-C, pp. 27-75.

, 1939, The Keyser Limestone and Helderberg Group,
in Willard, B., ed., The Devonian of Pennsylvania:
Pa. Geol. Survey, 4th Ser., Bull. G-19, pp. 29-91.

Tappan, Helen, 1960, Cretaceous biostratigraphy of northern
Alaska: Am. Assoc. Petroleum Geologists Bull., vol.
44, pp. 273-297.

Thomson, A. F. and Thomasson, M. R., 1969, Shallow to deep
water facies development in the Dimple Limestone
(Lower Pennsylvanian), Marathon region, Texas,
in Friedman, G. M., ed., Depositional environments
In carbonate rocks: Soc. Econ. Paleontologists
and Mineralogists Spec. Pub. 14, pp. 57-78.

Thorp, E. M., 1939, Florida and Bahama marine calcareous
deposits, in Trask, P. D., ed., Recent marine
sediments: Am. Assoc. Petroleum Geologists Spec.
vol. 4, pp. 283-297.

Tyrrell, W. W., Jr., 1969, Criteria useful in interpreting
environments of unlike but time-equivalent carbon-
ate units (Tansill-Capitan-Lamar), Capitan Reef
complex, West Texas and New Mexico, in Friedman,
G. M., ed., Depositional environments in carbonate
rocks: Soc. Econ. Paleontologists and Mineralo-
gists Spec. Pub. 14, pp. 80-97.

Ulrich, E. O., 1911, Revisions of the Paleozoic systems;
Geol. Soc. America Bull., vol. 22, pp. 281-680.

Valentine, J. W. and Mallory, B., 1965, Recurrent group of
bonded species in mixed death assemblages: Jour.
Geol., vol. 73, pp. 683-701.

146

Weber, J. N., Bergenback, R. E., Williams, E. G., and
Keith, M. L., 1965, Reconstruction of depositional
environments in the Pennsylvanian Vanport basin by
carbon isotope ratios: Jour. Sedimentary Petrology,
vol. 35, pp. 36-48.

Weller, Stuart, 1900, A preliminary report on the strati-
graphic paleontology of Walpack Ridge, in Sussex
County, New Jersey: New Jersey Geol. Survey Ann.
Rept. 1899, pp. 1-46.

, 1903, The Paleozoic faunas: New Jersey Geol.
Survey Rept. on Paleontology, vol. 3, 462p.

Williams, H. S., 1900, Silurian-Devonian boundary in North
America: Geol. Soc. America Bull., vol. 11, pp.
333-346.

Wilson, J. L., 1969, Microfacies and sedimentary structures
in "deeper water" lime mudstones, in Friedman,
G. M., ed., Depositional environments in carbonate
rocks: Soc. Econ. Paleontologists and Mineralogists
Spec. Pub. 14, pp. 4-17.

Woodward, H. P., 1943, Devonian System of West Virginia:
W. Va. Geol. Survey, vol. XV, 665p.

Yeakel, L. S., 1962, Tuscarora, Juniata, and Bald Eagle
paleocurrents and paleogeography in the central
Appalachians: Geol. Soc. America Bull., vol. 73,
pp. 1515-1539.

Yoshirata, T., 1951, Some examples of the law of geometri-
cal progression of an animal population: Bull.
Japan Soc. Sci. Fisheries, vol. 16, pp. 185-187.

 

APPENDICES

147

Map
Number

APPENDIX A

LOCATION OF OUTCROPS

Outcrop
Name

Location

 

New Creek II

New Creek I

Smoke Hole Caverns

Grant-Pendleton
County line

Nelson Rock

Healing Springs

Big Draft

Abandoned quarry along cut-off
between U.S. 50 and U.S. 220-
W. Va. 46, Mineral County.

Quarry of Mineral County Stat
Road Commission along U.S. 50
(0.1 mile east of junction of
U.S. 50 and U.S. 220.

Outcrop in channel of Jordan
Run in the vicinity of the
entrance to Smoke Hole Caverns,
Grant County.

Road cut along W. Va. 28 dir-
ectly south of the Grant-
Pendleton County line.

Along the first dirt road (0.6
mile east of the junction with
W. Va. 28) turning east off of
W. Va. 28 south of the junction
between U.S. 33 and W. Va. 28
in the vicinity of Judy Gap,
Pendleton, County.

Along road and creek near west
end of gap west of Healing
Springs, Rockingham County, Va.

Along Big Draft which is cut-
ting through Bobs Ridge,
Greenbrier County.

148

 

 

Map
Number

Outcrop
Name

149

Location

 

10.

11.

12.

l3.

14.

15.

16.

17.

18.

Bluefield

Island Ford

Millboro Springs

Monterey

Thorn Creek

Ruddle

Smoke Hole South

Smoke Hole North

Maysville Gap

Greenland Gap

Rocks

Abandoned quarry at end of
hill southeast of the ball park
at Bluefield, Virginia.

Road cut near old bridge of
U.S. 60 between Covington and
Clifton Forge at Island Ford,
Va.

Along Va. 42, 7% miles south
of Millboro Springs, Bath
County, Virginia.

Quarry % mile east of Monterey,
Virginia and north of U.S. 50.

Along Pendleton County road 23,
0.9 mile east of junction with
U.S. 220.

Road cut along an abondoned
section of U.S. 220, 0.5 miles
east of Ruddle, Pendleton
County.

Along road leading from U.S.
220 into Smoke Hole, about 1.5
miles northwest of Upper Tract,
Pendleton County.

Along road leading from U.S.
220 into Smoke Hole, about 1.7
miles northwest of Upper Tract.

Along Lunice Creek and W. Va.
just west of Maysville, Grant
County.

Along North Fork of Patterson
Creek at east end of Greenland
Gap, Grant County.

Along Baltimore and Ohio Rail-
road in a water-gap of the
South Branch of Potomac River,
4 miles north of Romney, Hamp-
shire County.

Map
Number

Outcrop
Name

150

.Location

 

19.

20.

21.

22.

23.

24.

25.

Trinity Road

Thrasher Spring
School

Petersburg Gap

Hively Gap

Bull Pasture
Mountain

Fordwick

Gala

Along Trinity Road (2.4 miles
from the junction with U.S.
220) just southeast of the
junction between U.S. 50 and
U.S. 220, Hampshire County.

Along county road between Old
Fields and Williamsport, 2.8
miles east of Williamsport on
east side of mountain and 1.1
miles northwest of Thrasher
Spring School, Hardy County.

Along U.S. 220, two miles east
of Petersburg, between the
highway bridge over South Branch
of Potomac River and the Grant-
Hardy County line.

Along U.S. 33 in Hively Gap,
1.5 miles west of Oak Flat,
Pendleton County.

Along U.S. 250, 4 miles eash
of McDowell, Virginia, on the
east slope of Bull Pasture
Mountain.

In abandoned quarry of Lehigh
Portland Cement Company at
Fordwick, Augusta County,
Virginia, 0.4 mile east of
Craigsville.

Along the Chesapeake and Ohio
Railway, 1 mile north of Gala,
at southwest end of Bill Hill,
Botetourt County.

 

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