ORDOVICIAN AND CAMBRIAN
FOSSILS FROM A WELL CORE.
DELTA COUNTY, MICHIGAN

Thesis for The Degree of M. S;
MICHIGAN STATE UNIVERSITY

DONALD JAMES MOORE
I962

IIIIII III IIIIIIIIII

3 1293 01096 670

ABSTRACT

ORDOVICIAN AND CAMBRIAN FOSSILS FROM A WELL CORE,
DELTA COUIITY, E-CECIIIGAN

by Donald James Moore

A core from a well in Delta County in the Northern Peninsula of
Michigan was sampled and examined for megafossils. The core cuts a
nearly complete section of the Middle and Lower Ordovician and the
Upper Cambrian. The object of the problem was to find and identify
fossils from the core and determine stratigraphic succession and
ecologic conditions during the depositional interval covered by the
core. The latter two objectives to be achieved through the use of the
fossils identified.

The core was sampled at six inch intervals. Any fossils found
were extracted by mechanical methods and examined with the aid of a
binocular microsc0pe. The fossils were identified through the usual
means of published material. No new species were found.

The presence of the Trenton, Black River, and Lodi Formations and
the position of the Trenton - Black River contact were established. It
was determined that during the depositional interval of the core the

environment was primarily one of a near shore fluctuating sea.

ORDOVICIAN AND CAMBRIAN FOSSILS FROM A WELL CORE,

DELTA COUNTY, MICHIGAN

by

Donald James Moore

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements

for the degree of

MASTER OF SCIENCE
Department of GeOIOgy

1962

AC IGIOI‘ILE DGEI-IEI‘ITS

The author is deeply grateful to Dr. Jane E. Smith of the Michigan
State University Department of Geology under whose kind and patient guid-
ance this problem was undertaken.

Sincere appreciation is extended to Dr. C. E. Prouty, Dr. James H.
Fisher, and Dr. James Trow for their encouragement, constructive sugges-
tions, and critical examination of the manuscript.

Appreciation is also extended to the Michigan GeolOgical Survey which
generously supplied the core, to my wife Barbara Moore for her many hours
of work in the typing of this manuscript and to many of my fellow students

who discussed various facets of the prOblem with me.

ii

TABLE

ACKI‘ICIILEDGE‘QITS o o o o o o o 0
LIST OF FIGURES . . . . o . o .

INTRODUCTION . . . . . . . . . .
General
Nature and Scape

AREAL DESCRIPTION . . . . . . .
Location
Regional Structure

CORE DESCRIPTION . . . . . . .
General
Lithology
STRATIGRAPHIC FRAI-IEZIIORK . . . .
PREVIOUSWORK . . . . . ... .

OF CONTENTS

Deve10pment of Sampling Techniques

Laboratory-Methods
SUMMARY AND CONCLUSIONS . . . .

Summary
Conclusions

0 O O O O O

Stratigraphic Implications

Ecologic Implications
Regional Correlation
Further‘WOrk

BIBLIOGRAPHY . . . . . . . . . .

iii

Page
ii

iv

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15

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40
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45
47

LIST OF FIGURES
Page

Figure 1 Location of Delta County, Michigan
and the Cornell core . . . . . . . . . . . . . . . . 5

Figure 2 Column showing the Cambrian and Ordovician
formations of Michigan as represented in the
comell com 0 O O O O O O O O O O O O O O 0 O O O O O 9

Figure 3 Lith010gy and paleontology of the Cornell
com 0 O O I O O O O 0 O O O O O O O O 0 O O O O O O O M

Figure 4 Geographic and geologic ranges of Middle
Ordovician species from the Cornell core . . . . . . . 46

iv

INTRODUCTION

General

The stratigraphy of the Ordovician system of the Northern Peninsula
of Michigan is not fully understood. The discontinuous nature of surface
exposures due to the cover of glacial drift and the lack of published
'work on wells into the Ordovician in the Michigan basin contribute to
make the study difficult.

It is hOped that study of a core which cuts a nearly complete sec-
tion of the Middle and Lower Ordovician of the Northern Peninsula of

Michigan may contribute some new lithologic and paleontologic information.

Nature and Scope
This report will cover a paleontologic analysis of a well cored

near Cornell, Michigan as an exploratory well by the Cleveland Cliffs
Iron Company. The core was given to the Michigan State Geological Survey
who turned it over to the Michigan State University Geology DepartmentI
for detailed study.

The purpose of this report is to identify, when possible, all
fossils recovered from the core, to determine the stratigraphic succession
based on faunal identification, and to make some determination of paleo-
ecologic conditions.

For practical reasons the scope of investigation of the fauna had
to be limited. BrachiOpoda were found to give the greatest overall
coverage of the core, so the BrachiOpoda were used as the prime founda-
tion of this report. Bryozoa, GastrOpoda, and other forms were identi-
fied as associates, their relative abundance in the core being in that

order.

Richard Dixon (1961) in an unpublished Master's thesis at Michigan
State University, completed a lithologic anaLysis of this same core.

Therefore, this report will investigate only the paleontologic aspects.

AREAL DESCRIPTION

Location

The exact location of the core which is the subject of this report
is SW%, NEfi, Sec. 5, T.40N., R.23W., Michigan Meridian. This is 2%
miles southeast of Cornell, Michigan in Delta County, and about 1500
feet south of the Escanaba River (Slaughter, 1960). Delta County is in
the south central part of the Northern Peninsula of Michigan and is on

the north shore of Lake Michigan.

Regional Structure
This core is located near the north-northwestern flank of the Mich-

igan basin. The Michigan basin is an extensive negative structure that
covers all of the Southern Peninsula of Michigan, part of the Northern
Peninsula and parts of Wisconsin, Illinois, Indiana, Ohio and Ontario,
Canada. Studies have shown that it has been a subsiding structure since
Precambrian time (Newcombe, 1933; Pirtle, 1932; Cohee, 1948). The basin
today is a relatively restricted area bounded by the Findlay and Kanakee
arches on the south, the Wisconsin dome on the west, the Algonquin arch
on the east, and the Precambrian rocks of the Canadian shield on the
north (Pirtle, 1932). These barriers are breached by the Chatham sag on
the east and the Logansport sag on the Kanakee arch to the southwest
(Cohee, 1998). Some doubt still exists as to the time of introduction
of these major positive elements surrounding the basin. Pirtle (1932)
has contoured the top of the Trenton in the Michigan basin and the
structural contours clearly show the influence of the positive structural
barriers.

Pirtle (1932), Newcombe (193a), Mellhorn (1958), and King (1959)

3

all give evidence showing that the Kanakee and Findlay arches were pres-
ent during Ordovician time although perhaps not yet as major positive
elements isolating the basin.

Newcombe (1934) points out that complete isolation of the basin did
not occur for the first time until late Silurian time.

Results of recent drilling in and around the Michigan basin may
provide more information.

On this north-northwestern flank of the Michigan basin, Silurian
and Ordovician rocks crap out along stream beds and other places where
they are not covered by glacial drift. The regional dip is about 40
feet per mile to the southwest. According to Hussey (1936) the dip is
not constant and may change directions locally. This is thought to be
a reflection of the Precambrian basement rocks upon which the Paleozoic

rocks rest.

 

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CORE DESCRIPTION

General

The two inch core was drilled at an angle of 45° from the vertical,
the direction of the inclination being to the south (Slaughter, 1960).
The core has an actual length of 793 feet. It reached a true depth of
561 feet. All depths referred to in this report will be corrected
depths, the corrections having been calculated from inclined depths.

The core was not logged prior to its acquisition by Michigan State
University. The Cleveland Cliffs Iron Company took three or four inch
cuts about every 10 feet for their files. The core was placed in boxes
capable of holding 11 feet of core. In many cases, however, the core
in these boxes actually cover an interval of anywhere from five to twenty
feet. Because of this and the fact that the boxes are inadequately
marked to cover situations such as this, it is often difficult to place
precisely the depth of any particular sample. The possible margin of
error is usually not so great that careful work cannot keep the error
down to a maximum range of plus or minus one foot. The exceptions are
several boxes, one of which is not labelled at all and another which
seems to be mislabelled since the lithology of the rock it contains is
quite different from that immediately above and below. The latter box
is labelled "to 356?". Two other boxes are marked "to 367?", and "to
378?”. Although these two boxes are questionable, if it is assumed the
labelling is correct, depths can be worked out.

If these sources of error are kept in mind, however, good accuracy
can be obtained. The two-inch diameter of the core provides a relatively

small sample to obtain diagnostic results.

For purposes of identification, the Michigan State Geological Survey
refers to this core as the Cornell core. That name will be used in this

report also.

Lithology
The upper 100 feet or so is primarily limestone with irregular,

interbedded shale while the next 375 feet is primarily dolomite with
about 36 feet of sandstone and 16 feet of limestone interbedded with the
dolomite. The lower 85 feet is primarily sandstone with about five and
one-half feet of interbedded dolomite. Conglomerates appear at 117 feet,
2M7 feet, #85 feet and lowest three feet of core. Thin shaly partings
occur throughout the core. Glauconite and pyrite are conspicuous in the
dolomite middle section (Dixon, 1961). Figure 3 shows the lithology of
the core.

Detailed lithologic descriptions are given in Dixon's report (1961).

STRATIGRAPHIC FRAMEWORK

The fossiliferous portion of the Cornell core starts in the lower
part of the Trenton (Slaughter, 1960) and continues through the Black
River of the Middle Ordovician (Dixon, 1961). The core continues into
the Cambrian but is barren of fossils except for a few scattered Specimens.
The entire core was examined for fossil content. Figure 2 is a graphic
representation of the Ordovician section of the Michigan basin. These
formations have been correlated rather well with those of the Upper
Mississippi Valley and Ontario, Canada and generally with those of the
Appalachian area and the Tennessee - Kentucky area.

Any paleontologic implications of this core as they affect any
interpretation regarding presence or absence of any of these units in
the core or the presence of formational contacts will be presented in
the conclusion of this report.

Dixon (1961), whose work has proceeded the writer's, may be referred
to for an excellent summary of the historical deve10pment of the strati-
graphic nomenclature of the Ordovician as related to the stratigraphy of

this core.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 2 Column showing the Cambrian and

Ordovician formations of Michigan
as represented in the Cornell core.
(After Dixon, 1961)

PREVIOUS WORK

In 1936, Hussey made a study of the Trenton and Black River rocks
of Michigan. His approach was both paleontologic and stratigraphic in
that he listed the fauna and described the rock type and in this way
correlated outcrops over a broad area of the Northern Peninsula. In
1952, Hussey again studied the Ordovician outcrops of the Northern Penin-
sula, this time concentrating on the Middle and Upper Ordovician rocks.
In that report Hussey zoned the Trenton into three zones on a faunal
basis, describing and picturing the fossils.

Both of Hussey's papers describe work with outcrops some of which
are only two miles from the location of the core described in this
report. His works remain as the best available material on the Ordovician
of the Northern Peninsula.

In 19h6 Alice Wilson began a series of papers for the Canadian
Department of Mines and Resources, Mines and Geology Branch, which were
planned as a series of reference texts on the paleontology of the Paleo-
zoic formations of the Ottawa - St. Lawrence Lowland. Each of these
papers describe a faunal class or, if apprOpriate, more than one faunal
class of the Ottawa Formation. These papers, which are comprehensive and
very useful, appeared as numbered bulletins of the Canadian Geological
Survey.

E. O. Ulrich and G. Arthur Cooper in 1938 published a study of the
Ozarkian and Canadian BrachiOpoda in which they described specimens from
all of North America except Newfoundland. This work is invaluable for the
study of the Lower Ordovician.

In 1953, G. Arthur Cooper's sequel to the latter publication was

10

11

released. Although titled Chazyan agg,Re1ated Brachiopoda, forms from

as high as the Trenton or its correlatives are described. This volumi-
nous work is comprehensive in that it describes fossils from all the
United States and Canada, but there is a definite emphasis on Appalachian
or nearby foms.

The classical works on Ordovician rocks include Hall's 1847 study
of the paleontology of New York. This includes descriptions from the
type areas of Trenton and Black River rocks.

Another classical work is the 1895 publication of the Geological
gag Natural History Sprygy‘gf Minnesota. Winchell, Ulrich, gt_gl, produced
in this report on the "Lower Silurian” a long-standing reference to the
fauna of the Upper Mississippi Valley. It covers all classes of fossils
as does Hall's New York study.

The Treatise 9g Invertebrate Pgleontology sponsored.by the Geological
Society of America is an authoritative discussion and description of the
various classes of animals each of which is taken up in individual volumes.
This work is not as yet complete but those sections which are completed
are useful, particularly in the early stages of identification.

The works discussed above are the basic ones that must be consulted
when working on Ordovician paleontology. They are comprehensive works

pertinent to the study of the Ordovician fauna of the Michigan basin.

METHOD OF EXAMINATION

Develooment 9£,§§mpligg Teghgigue

The nature of the core which is the subject of this thesis presented
several prOblems. Its length and the dominant lithology made the search
for fossil specimens difficult and the two-inch diameter cut down rather
drastically on the statistical chance of finding fossils. As a result,
much time was spent in develOping the best approach to recover the great-
est amount of fossil material that would insure good coverage of the
core and provide diagnostic results.

In the beginning, it was haped that microfossils would be found in
sufficient quantities to enable a paleontologic analysis based on this
type of fossil. Recovery of microfossils proved to be impossible for the
most part. The method used in this initial, futile search was as follows.
The core was examined for shale breaks or other likely intervals where
fossils might be found in identifiable condition and samples from these
intervals were removed to the laboratory for disintegration. If natural
intervals were not closely spaced an arbitrary choice of a one-foot sample
interval was made and samples were removed from these places also and
taken to the laboratory for disintegration. A gross examination was made
to find any specimens on the broken surfaces. When specimens were found
on the broken surfaces they were either removed or cleaned in place
depending on matrix material and the condition of the specimen. After
the gross examination, the sample was disintegrated by one of or a combi-
nation of several methods. These methods are (a) mechanical, (b) boiling
in plain water (Layne, 1950), (c) boiling or soaking in potassium hydroxide

(Bolli, 1950), (d) alternate heating and water quenching (MacVicar, 1951,

12

13

Redmond, 1953), and (e) heating and kerosene quenching (Layne, 1950;
Crowley, 1952; Redmond, 1953). These methods all gave varying degrees

of success depending on the lithology involved, the more dense rocks
being nearly impossible to disintegrate and still produce identifiable
specimens. Iisintegration complete enough to permit recovery of micro-
fossils was satisfactorily Obtained only when shales were boiled in plain
water or potassium hydroxide. After subjecting the samples to these
disintegration techniques with little recovery, examination forImicro-
fossils was for the most part abandoned. Further study was devoted to
megafossils using microscOpic examination and mechanical extraction of
any fossils found which gave results which were as good as could be gained

through other methods.

Laboratory Methods
The core was examined at approximately six-inch intervals which gave

a coverage of approximately a fourainch interval of true depth. Since
the core was cut at an angle of 45° from the vertical, care was taken to
insure that all sample cuts were made along bedding planes. When fossils
were found, a closer examination of the immediate core section was made
to determine if more were present.
The fossils were extracted with the following equipment:

(1) Burgess Vibro Tool

(2) Common Needles

(3) Dissection Needles

(9) Small Chisels

(5) Hydrocholoric Acid

(6) wax to localize the acid effect

14

Examination was made with a binocular microscOpe.

The chisels were used, when necessary, to split the core samples
to gain access to specimens imbedded or partially imbedded in the matrix.
The common needles and dissection needles were used for chipping matrix
and cleaning fossils. The Vibro-Tool was of great value where large
amounts of matrix needed to be chipped. Acid was used only where its use
would not harm the specimen being cleaned. Iilute acid (H01) was used to
assist in softening up the matrix and occasionally to accomplish final

cleaning of the specimen.

SYSTEMATIC DESCRIPTION

Phylum PROTOZOA

Class RHIZOPODA
Order CHITINOZOA
Family CONOCHITINIDAE

Genus RHABDOCHITINA Eisenack, 1931
RHABDOCHITINA? MINNESOTENSIS Stauffer, 1933

RhabdochitinaI minnesotensis Stauffer, 1933, G. S. A. Bu11., vol. 44,

p. 1209, piT‘ZET'IEEI‘39; Collinson and Schwalb, 1955, Ill. State

Geol. Surv., Rept. of Invest., no. 186, p. 30, fig. 10.

Discussion. - Several specimens of this tiny cylindrical organism
were obtained from the Cornell core. Four samples covering an interval
of 20 feet contain hundreds of these chitinozoans in jumbled attitudes.
The only other fossils found with them were scolecodonts.

Horizon gag Locality. - Reported from the bottom five feet of the
Decorah Formation in Minnesota by Stauffer (1933). Collinson and Schwalb
(1955) mention only Stauffer's report of this Species from the Becorah.
They report no other horizon or locality. In 1960 Taugourdeau reported
an occurrence in the Gothlandien (Silurian) of the Sahara. The specimens
from the Cornell core were at depths of 162 ft., 170 ft., 173 ft., and
183 ft. The Spechts Ferry Member of the Decorah Formation is the basal
unit of the Decorah (Twenhofel, 1954). According to Kay (1935) the
Spechts Ferry is Trenton in age. According to COOper (1956) the Spechts
Ferry is Black River in age.

Specimen Numbers. - 232, 242, 245, 260.

15

16

Phylum COELENTERATA

Class SCYPMOZOA

Genus METACONULARIA Foerste, 1928

METACONULARIA CALDERI Sinclair, 1940

Metaconularia calderi Sinclair, 1940, Trans. Roy. Soc., Canada, 3rd Ser.
34, sec. 4, p. 110, pl. 3, figs. 3-5; Wilson, 1951, Canada. Geol.
Surv. of Can., Bull. 17, p. 102, p1. XIX, figs. 1-4.

Discussion. - This specimen consists of only a small fragment, but
the distinctive ornamentation of the species permits identification.

Horizon and Locality. - This species has been reported doubtfully
from the Sherman Falls Beds in Ontario and with certainty from the Coburg

Beds in Ontario. This specimen was found at a depth of 17 feet in the

Cornell core.

Specimen Number. - 24.

Genus CONULARIA Miller, 1818
CONULARIA cf. C. TRENTONENSIS Hall, 1847
Conularia trentonensis Hall, 1847, Pal. New York, pt. 1, p. 222, pl. 59,
figs. ua-fe
Discussion. - This Specimen consists only a part of the entire
organism but it is recognizable as Conularia. Its structure most nearly
resembles the species 9; trentonensis Hall but since not enough of the

characters can be seen, it seems advisable to only note the resemblance

and not assign a species.

17

Horizon gag Locality. - Reported from the Trenton or its equivalents
in Quebec, New York to Virginia, Michigan, and Iowa. This specimen was
found at a depth of 58 feet in the Cornell core.

Specimen Number. - 82.

Class ANTHOZOA
Subclass ZOANTHARIA

Genus STREPTELASMA Hall, 1847
STREPTELASI'IA of. S. CORNICUI.UM Hall, 1847
Streptonlasma corniculum Ha11,1847, Paleontology of New York, vol. I,

p. 69, pl. 25, figs. la-le.

Streptgplasma crassa Hall, 1847, Paleo. of New York, vol. I, p. 70, pl. 25,
figs. 2a-2c.

Streptoolasma multilamellosa Hall, 1847, Paleo. of New York, vol. I, p. 70,
pl. 25, figs. 33-300

Streptoplasma parvula Hall, 1847, Paleo. of New York, vol. I, p. 71, pl.
25, figs. 4a-4c.

Streptelasma corniculum Billings, 1856, Canadian Naturalist and Geologist,
vol. I, p. 122, figs. 3 & 4 on p. 121; Nicholson, 1875, Paleo. of
Ontario, p. 12, (p. 26 partim): U1rich,in Winchell, Schuchert, et al.,
1885, Geol. of Minn., Final Report, vol. III, pt. I, Paleontology,

p. 90, pl. 0. figs. 20, 21.

Petraia corniculum Billings,in Logan, 1863, Geology of Canada, p. 156,
fig. 118, p. 938.

Di§cu5§ion. - This specimen is the tap of a corallum and is broken.
On the basis of its size and septal characteristics it was assigned to
the genus Streptelasma. Because of its condition a definite specific
determination was not made but because of its superficial resemblance to

§;_corniculum Hall and the fact this species is quite commonly reported

 

18

in Black River and Trenton rocks, S; corniculum was recorded as a possible
specific name.

Horizon and Locality. - Common in the Black River and Trenton of

 

central and eastern North America. This specimen was found at a depth of
77 feet.

Spgcimen Number. - 109C.

Phylum BRYOZOA

Subphylum ECTOPROCTA
Order TREPOSTOMATA
Suborder INTEGRATA
Family TREMATOPORIDAE
Genus BATOSTOMA Ulrich, 1882
BATOSTOMA WINCHELLI (Ulrich) 1886
Amplexopora winchelli Ulrich, 1886, 14th Ann. Rept. Geol. Nat. Surv. Minn.,
p. 91.
Batostma winchelli (Ulrich) U1rich,in.Winche11, Schuchert, §t_al., 1885,
Geol. Minn., Final Report, vol. 3, pt. 1, Paleontology, p. 295,
pl. XXVI, figs. 33-37; p1. XXVII, figs. 1-6.
Discussion. - Four specimens found in the Cornell core have been
assigned to the species Batostoma winchelli (Ulrich). Sections were
made of two of them.

Horizon and Locality. - Reported from the Trenton of Minnesota. These

were at depths as follows:

19

Specimen Number Depth in Feet
66 46.5
99 70
110 78
118 83.5

Specimen Numbers. - 66, 99, 110, 118.

Family PHYLLOPORINIDAE

Genus PHYLLOPORINA Ulrich, 1887
PHYLLOPORINA sp.

Discussion. - This specimen is very small. It has the appearance
of angular ridges on a branching surface. The angular ridges are four
to eight in number and could be the zooecial tubes. It resembles
Ehylloporina though identification is doubtful. No sections were made.

Horizon §QQ_Loca1ity. - Reported from the Trenton and Black River
rocks of Ontario, New York and Minnesota. This Specimen was found at a
depth of 76 feet in the Cornell core.

Spgcimen Number. - 108.

20

Phylum BRACHIOPODA

Class INARTICULATA
Superfamily OBOLACEA
Family OBOLIDAE

Genus LINGULA Bruguiere, 1789
LINGULA? sp.

Discussion. - This specimen is crushed and broken so that only a
general shape and some shell material is still recognizable. For this
reason its affinity can only be surmised. The shape is subquadrate and
the shell remnants are shiny and show concentric growth lines. In size
and shape this specimen resembles L;.glgggi,Whitfield, which is a Trenton
form, but due to its condition no positive identification can be made.

Horizon gag Locality. - This specimen was found at 87.5 feet in the
Cornell core.

Specimen Number. - 124.

Subfamily BICIINAE

Genus DICELLOMUS Hall, 1873
DICELLOMUS POLITUS (Hall) 1861
Obolus appolinus? Owen (not Eichwald), 1852, Rept. Geol. Surv. Wis.,
Iowa, and Minn., Appendix, p. 501, pl. 18, figs. 9, 11, 15, 20.

Lingula polita Hall, 1861, Rept. Supt. Geol. Surv. Wisc., p. 24.

Obolella Sp. 3 Billings, 1865, Geol. Surv. Can., Paleozoic Fossils, vol.
1, p. 7.

21

Lingpla? polita Hall, 1862, Rept. Geol. Surv. Wisc., vol. 1, p. 435,
Fig. 1, p. 21.

Obolella? polita Hall, 1863, Sixteenth Ann. Rept. New York State Cab.
Nat. Hist., pp. 133-134, p1. VI, figs. 17-21.

Lingulepis prime Meek and Hayden, 1865, Smithsonian Contributions Know-
ledge, No. 172, Paleontology Upper Missouri, pt. 1, p. 3, pl. 1,
figs. 2a-b.

Dicellomus polita Hall, 1873, 23'd Ann. Rept. New York State Cab. Nat.
Hist., p. 246.

Obolella polite (Hall), Whitfield, 1880, U. S. Geog. and Geol. Survey
Rocky Mtn. Region, Rept. Geol. and Resources Black Hills of Dakota,
by Newton and Jenney, pp. 339-340, p1. II, figs. 12 & 13; welcott,
1886, Bull. U. S. Geol. Surv., No. 30, p. 111; Hall and Clarke, 1892,
Nat. Hist. New York, Paleontology, v01. 8, pt. 1, pp. 72 & 73, pl.
II, figs. 37-41.

Dicellomus politus (Hall),'Wa1cott, 1899, Mon. U. S. Geol. Surv., vol. 32,
pt. 2, p. 443 & 446, p1. LX, figs., 2 &I4a; walcott, 1905, Proc. U. S.
Nat. Mus., vol. 28, p. 316-318; Grabau and Shimer, 1909, North American
Index Fossils, vol. 1, p. 189-190, fig. 224; Malcott, 1912, Mono. U. S.
Geol. Surv., vol. 51, pts. 1 & 2, p. 575, text figs. l6A-B, 49A-B,
p1. LII, figs. 1, 1a-k, 2, 2a-i, 3, 4, 4a, 5, 5a-b; Shimer and Shrock,
1944, Index Fossils of North America, p. 285, pl. 10?, figs. 8-14.
Discussion. - The sample consists of one fairly well-preserved
specimen showing all diagnostic characteristics mentioned by Walcott
except internal structures. The specimen is a slightly crushed ventral
valve. The most posterior part of the beak is missing. There are two
other specimens in the same piece of rock that are considerably crushed
and broken.
Horizon ppd Locality. - The species is reported from the Upper
Cambrian of the Appalachian area, Wisconsin, Missouri, Black Hills, and
the Cordilleran area. This specimen was found at a depth of 415 feet in

the Cornell core.

Specimen Number. - 587

22

Class ARTICULATA
Superfamily ORTHACEA
Family HESPERORTHIDAE
Subfamily HESPERORTHINAE

Genus HESPERORTHIS Schuchert and Cooper, 1931
HESPERORTHIS TRICENARIA (Conrad), 1843
Orthis tricenaria Conrad, 1843, Proc. Acad. Nat. Sci. Philadelphia, v. 1,

p. 333; Bassler, 1915, U. S. Nat. Mus. Bull. 92, p. 897.

Orthis disparilis Conrad, 1843, Proc..Acad. Nat. Sci., Philadelphia, v. 1,
p. 333-

Hesperorthis tricenaria (Conrad) Schuchert and COOper, 1932, Men. Peabody
Mus. Nat. Hist., v. 4, pt. 1, p. 86.

Discussion. - This is a small specimen, broken but fairly well-
preserved and showing some of the interior. It is probably Hesperorthig
diSparilis (Conrad) which is thought by COOper to be a young form of
H; tricenaria (Copper, 1956).

Horizon ppd Locality. - Reported from the Trenton or its equivalents
over a large part of the Middle and Upper Mississippi Valley. Also in
Northern Peninsula of Michigan. Found at a depth of 99 feet in the
Cornell core.

Specimen Numbers. - 139, 6B.

23

Superfamily TRIPLESIACEA
Family TRIPLESIIDAE

Genus OXOPLECIA Wilson, 1913
OXOPLECIA? sp.

Discussion. - This specimen has been doubtfully referred to the
genus Oxoplecia on the basis of certain external features. It has an
approximate width of 13mm. It is costate and has a broad, shallow sulcus
with five costae in the sulcus. The general outline is oval, and is gnetly
convex. The sulcus apparently starts near the beak and broadens rapidly.
The preservation is so poor that nothing else can be determined of this
specimen. Although the possibility of sculpturing such as imbrication
exists, any hint of it has been destroyed in the process of preservation
of this specimen. The exact extent of the beak and portions of the
periphery cannot be determined. For these reasons no attempt has been
made to identify it as to species and generic determination has been
given with a definite question.

Horizon and Locality. - This genus has a long vertical range but the
forms most similar to the specimen reported here are Black River in age
and are reported from nearly all areas of occurrence. This specimen came
from a depth of 166.5 feet in the Cornell core.

Specimen Number. - 237.

24

Superfamily RHYNCHONELLACE
Family RHYNCHOTREMATIDAE
Genus ROSTRICELLULA Ulrich and Cooper, 1942
ROSTRICELLULA nmmso'rENSIs (Sardeson) 1891
Rhynchonella minnesotensi§_Sardeson, 1901, Minn. Acad. Nat. Sci. Bu11.,
vol. 3, p. 333, pl. 4, figs. 21-23.
Rhynchotrema ipeguavalvis Winchell and Schuchert (part) 1892, Geol. Minn.,
Final Report, vol. 3, pt. 1, Paleontology, p. 459, pl. 34, figs. 9-11;
15-230

Rhynchotremp minnesotense (Sardeson) 1922, Fenton and Fenton, Iowa Acad.
of Sci. Proc., vol. 22, p. 70, pl. 1, fig. 15-17.

Rostricellula pippesotensis (Sardeson) Cooper, G. A., 1956, Smith. Misc.
Coll., vol. 127, pt. 1 & 2, p. 269, p1. 131A, figs. 1-7, p1. 139A,
figs. 1-11.

Discussion. - Two specimens were found. One specimen (I 110) is
slightly smaller and thinner than that described by Cooper and is prob-
ably an immature specimen. Winchell and Schuchert describe one of this
nature. It is a complete specimen with no interior showing. Another
specimen (# 97) of the same species is a mature form. It is a broken
brachial valve showing only the beak characters of the interior. This
interior of this specimen is encrusted with a bryozoan (Prasapora).

Horizon app Locality. - COOper reports this species from the MeGregor
Member of the Platteville Formation in Wisconsin, Illinois, and Minnesota,
and the Spechts Ferry Member of the Decorah in Minnesota. Winchell and
Schuchert describe it from the Trenton equivalents of the Upper Mississippi
valley. Specimen No. 110 was found at a depth of 78 feet in the Cornell

core while specimen No. 97 was found at a depth of 68.5 feet.

Spgcimen Numbers. - 110, 97.

25

Superfamily ATRYPACEA
Family ATRYPIDAE
Subfamily ZYGOSPIRINAE
Genus ZYGOSPIRA Hall, 1862
ZYGOSPIRA RECURVIROSTRIS (Hall) 1847

Appypa recurvirostris Hall, 1847, Pal. New York, 1, p. 140, p1. XXXIII,
fig. 5.

Zygospira recurvirostrip (Hall) Chamberlin, 1883, Geol. Wisc., vol. 1,
p. 155, fig. 7; Winchell and Schuchert, 1892, Geol. Minn., Final
Report, vol. 3, pt. 1, Paleontology, p. 466, p1. XXXIV, figs. 38-41.
Discussion. - Ten well-preserved specimens were found, one of which

is broken and another is crushed slightly. All have both valves present.

No internal structures were observed.

Horizon gpd Locality. - This species has been found abundantly in
almost all occurrences of the Trenton Formation and less often in Black
River rocks. These specimens came from depths as follows:

Specimen # 82a at 57.8 feet
" # 89a at 59.5 "
" I 90 at 63.5 "
" # 99a at 70 "
" # 99b at 70 "
99c at 70 "

3
:Ih

" A 99d at 70 "
109a at 77 "
" # 116 at 82 "

SI}:

" I 118b at 83.5 "

Sppcimen Numbers. - 82a, 89a, 90, 99a, 99b, 99C. 99d, 109a, 116, 118b.

26

ZYGOSPIRA cf. 2. ELONGATA Cooper, 1956

Zygospira elongata Cooper, 1956, p. 670, pl. 2680, fig. 29-32.
Discussion. - The specimen is a large Zygosoira with 33 costae, a

prominent median fold on the pedicle valve with slightly concave flanks
posteriorly which accentuate the fold. It is nearly piano-convex with
the pedicle valve being moderately convex. The brachial valve has a
shallow sulcus beginning near the beak and broadening anteriorly to occupy
nearly half the anterior margin. The commissure is sulcate with the flanks
slightly swollen. Five costae occupy the sulcus. Measurements are:
length, 5.5 mm; width, 5.3 mm; thickness, 3.5 mm.. The specimen is well
preserved with both valves complete. Internal structures were not observed.
This form is only tentatively assigned to §p_elongata COOper, because it
has a 5 or 6 more costae than his §p_elongata and that species has not
been reported as yet from the Upper Mississippi Valley.

Horizon ppd Locality. - COOper reports this species from the Lebanon
Formation in Tennessee. This specimen was found at a depth of 123 feet

in the Cornell core.

Sppcimen Number. - 175.

ZYGOSPIRA DEFLECTA (Hall) 1847

Atma deflecpa Hall, 1847, Pal. New York, 1, p. 140, p1. XXXIII, fig. 4.

lygospira deflects (Hall), Hall and Clarke, 1894, Pal. New York, 8, pt. 2,
p- 157-

Discussion. - This is a small specimen with the typical deflected

flanks of §p_deflecta (Hall). It is well-preserved except for the brachial

2?

valve which is partially covered with matrix. The Specimen is complete
with no interior showing.

Horizon app Locality. - Reported in Trenton and Black River equiv-
alents of Ontario and New York. This specimen was found at a depth of
69 feet.

Specimen Number. - 98.

Subfamily GLASSINAE Schuchert, 1929

Genus IDIOSPIRA Cooper, 1956
IDIOSPIRA PANDERI (Billings) Cooper, 1956

Camerella ppmderi Billings, 1859, Canadian Nat. Geol., v. 4, p. 302; Logan
1863, Geol. Can., p. 143, fig. 78; Hall and Clarke, 1894, Pal. New
York, v. 8, pt. 2, p. 220, pl. 62, figs. 19-23; ? Raymond, 1911, Ann.
Carn. Mus., v. 7, p. 250, pl. 36, figs. 31, 32; Wilson, 1946, Geol.
Surv. Canada, Bull. 8, p. 118, p1. XI, fig. 2.

Idiospira papderi (Billings), Cooper, 1956, Smithsonian Misc. 0011., v. 127,
pts. 1 a 2, p. 691, pl. 108F, figs. 26-32, p1. 195F, figs. 33-37,
p1. 195H, figs. 42-46.

Discussigp. - A single broken pedicle valve was found. Internal
structures were not observed.

Horizon apg,Locality. - It is widely reported from the basal Trenton
or its equivalents in New York, Ontario, Quebec, Kentucky, Missouri, and

Iowa. This specimen was found at a depth of 123 feet in the Cornell core.

Spgcimen Number. - 175a.

28

Superfamily PLECTAMBONITACEA
Family SOWERBYELLIDAE
Subfamily SOMERBYELLINAE

Genus SOWERBYELLA Jones, 1928
SOWERBYELLA SERICEA (Sowerby) 1839
Leptaena sericea Sowerby, 1839, Murchison's Sil. Sys., pt. 2, p. 636,

pl. XIX, figs. 1 & 2.

Plectambonites sericeus (Sowerby) Hall and Clarke, 1892, Pal. New York, 8,
pt. 1, pl. XV, figs. 15-190

Sowerbyella segicea (Sowerby), Jonws, 1928, Geol. Surv., Gr. Brit., Mem. 1,

p. 414, pl. XXI, figs. 1-4; Wilson, 1946, Geol. Surv., Can., Bull.

No. 8, p. 51, p1. III, fig. 26.

Discussion. - Four pedicle valves with no interiors visible were
found. Two of them are fairly well-preserved.

Horizon and Lgcality. - This species is reported from the Black River
and.Trenton equivalent in Ontario and the Trenton of Michigan. Specimens
were found at the following depths:

Specimen I 66 at 46.5 feet
" A 118a at 83.5 "
" I 118b at 83.5 "
" I 126a at 89.5 "

Specimen Numbers. - 66, 118a, 118b, 126a.

Discussion. - This specimen is clearly of the genus Sowerbyella but

specific determination cannot be made. Both valves are present and

29

complete and no interior can be seen. The surface sculpturing cannot be
seen in enough detail, due to exfoliation, to enable a diagnosis to be
made. It is rather large, convavo-convex with the pedicle valve moder-
ately convex and with the greatest convexity just anterior to the umbo.
The sides are gently sloping. The interarea is flat, and the pedicle
opening sub-triangular with deltidial plates. The beak projects slightly
over the posterior margin and the outline is suboval. There is a promi-
nent concentric rugosity midway of the brachial valve, with a fainter
corresponding one on the pedicle valve. There are very faint wrinkles

on the posterior margin.

Width - 13.5 mm.
Length - 9.0 mm.
Midwidth - 13.0 mm.
Brachial Length - 8.5 mm.
Height - 3.0 mm.
Thickness - 2.0 mm.

Horizon and Locality. - The genus has been reported in all Middle
Ordovician rocks. This Specimen was found at a depth of 45 feet in the
Cornell core.

§pecimen Number. - 64a.

3o

Superfamily STROPHOHEN CE.
Family STROPHOHEHIDAE

Genus STROPHOMENA Blainville, 1825

STROPHOI-E'I-IA cf. 3. FILITBXTA (Hall), 1847

Lentaepg filitexta Hall, 1847, Pal. New York, v. 1, p. 111, pl. 318,
fig. 3.

 

Strophomena filitexta Hall and Clarke, 1892, Pal. New York, v. 8, pt. 1,

p. 251, pl. 9, fig. 6; Fenton, 1929, Amer. Midland Nat., v. 11, no. 9,

pp. 500-503, pl. 38, figs. 1-5.

Discussion. - Two samples found in the Cornell core came from within
three feet of each other and contain brachiOpods that could be referred
to StrOphomena filitexta (Hall). One sample consists of one large, in-
complete pedicle valve with external features only while the other sample
consists of many large, broken, intermingled valves. The size and external
characteristics of the valves strongly suggest §;,filitexta.

Horizon Egg Locality. - This species has been found in the Trenton
and Black River equivalents in the Middle and Upper MisSissippi valley,
Michigan, the Appalachians, and Ontario. These specimens were found at
depths in the Cornell core as follows:

Specimen # 176 at 124.5 feet
" f 180 at 127 "

Specimen Numbers. - 176, 180.

STROPHOIvEI-EA sp.

Inscussion. - Two specimens found in the Cornell core at depths of

60.5 feet and 77 feet cannot be identified beyond genus. Both are resup-

31

inate, reticulate, and have costellae of varying size. For these reasons

they have been placed in the genus Strophomena. Ho internal characters are

available and in both cases, poor preservation prevents measurements.
Horizon and Locality. - These specimens were found at the following

depths:

a:

Specimen 86 at 60.5 feet
It # 1091) at 77 n

Specimen Numbers. - 86, 109b.

Genus RAFII-IESQUII-JA Hall and Clarke, 1892
mnmsomm NORMALIS Wilson, 1932

Rafinesquina normalis Wilson, 1932, Royal Soc. Can. Trans., ser. 3, v. 26,
sec. 4, p. 395, pl. 5, figs. 5-7; Salmon, 1942, J. of Paleo., v. 16,
No. 5, p. 585, pl. 86, figs. 21-24; Wilson, 1946, Canada. Geol. Surv.
Bull. No. 8, p. 79, pl. 8, figs. 10, ll, text fig. 6, No. 6.
Discussion. - The specimen referred to here aslfig normalis is a
complete specimen except that the cardinal extremities are broken. No
interior is visible but the beak was washed with acid (Cooper, 1956) and
faint outlines of interior structures are visible. Acidizing was not
satisfactory due to the partial silicification of the specimen as evi-
denced by Beekite structures. The exterior of the specimen is in good
enough condition to recognize all diagnostic characteristics. Salmon (1942)
in her paper on Mohawkian RafineSQuinae, defined the essential identifying

characteristics as follows:

32

"The most important characters are those of

the interior (especially the brachial) and

the shell structure (character of the pseudo-

punctae). These are considered fundamental

and are here used as generic distinctions.

This usage is in accord with recent research

in other groups of brachiopods, notably the

'work of Schuchert and COOper on the Orthoidea."
She further states in regard to specific determination:

" convexity and outline - are here

considered the basic criteria for dis-

tinguishing species."
With regard to the generic distinctions, the character of the pseudo-
puncta, the shape of the cardinalia and the sum of other minor characters
indicates that the specimen discussed herein is of the genus Rafinesguina.
Specific determination was made through careful measurements and the ratios
of these measurements. 'Wilson (1946) says that the average measurements
of the type specimens of fi:_normalis are: width, 29mm.; length, 22mm.;
thickness, 6mm.. She relates these measurements by dividing each of them
by the thickness. This expresses the dimension of thickness as one, which
she calls convexity, and each of the other two dimenshxnsas a multiple of
the thickness. These values are compiled in a table that shows the rela-
tionship of convexity to length and to width and points out that decreasing
length and width accompany increasing thickness. Her values for §;_normalis
are: convexity = 1, length = 3.6, width = 4.8. The measurements of the
specimen found in the Cornell core are: width, 30mm.; length, 21.5mm.;
and thickness, 6.3mm.. The reduced values for the specimen are: convexity
= 1, length = 3.4, and width = 4.5. An examination of Wilson's tables
show that these values approximate those of §;_normalis more nearly than
those of other Rafinesguipa species. Salmon (1942) states that the

length/width ratio of g, nor-mans is high, ranging from 1:1.uo to 1:1.53.

33

The length/width ratio of this specimen is 1:1.40.

Horizon and Locality. - This species, found at a depth of 56 feet in
the Cornell core, has a reported range of Upper Sherman Falls to Upper
Cdburg in New York and Ontario.

Specimen Number. - 79.

Superfamily DALMANELLACEA
Family DKLMANELLIDAE
( = WATTSELLIDAE)
Genus DALMANELLA Hall and Clarke, 1892

DALMANELLA WINCHELLI Cooper, 1956

Orthis Dalmanella hamburgensi§1.Winchell and Schuchert, 1885 (not
walcott, 1884 , Geol. Minn., Final Report, v. 3, pt. 1, Paleontology,
p. 440, pl. 33, figs. 14-16.

Eglmagella flinchelli Cooper, 1956, Smithsonian Misc. 0011., v. 127, pts.
1 & 2, p. 953, p1. 158D, figs. 15, 16.

Discussion. - This specimen is poorly preserved and no interior can
be seen. Enough external characteristics are available to warrant placing
this specimen with Qg'winchelli Cooper. Size and configuration are
similar and while only an estimate can be made, the number of costellae
seem to exceed 32 which agrees with.Winche11 and Schuchert's description.

Horizon and Locality. - This species is reported from the Decorah
Formation, Guttenburg Member, in Minnesota. This specimen came from a
depth of 20.5 feet in the Cornell core.

Specimen Number. - 29.

34

Family ONNIELLIDAE

Genus PAUCICRURA Cooper, 1956
PAUCICRURA ROGATA (Sardeson), 1897
Orthis rOgata Sardeson, 1901, Minn. Acad. Nat. Sci., Bull. 3, p. 331,
pl. 5, figs. 1-4; 1896, Amer. Geol., v. 19, p. 95, pl. 4, figs. 1-10.
Orthis (Dalmanella) testudinaria (Winchell and Schuchert, not Dalman)
Winchell and Schuchert, 1885, Geol. Minn., Final Report, pt. 1,
Paleontology, v. 3, p. 491, pl. 33, figs. 17-22; Hall and Clarke,
1893, Pal. New York, v. 8, pt. 1, pl. 58, figs. 27-31.

Inlmanella rogata (Sardeson) Schuchert and COOper, 1932, Men. Peabody
Mus. Nat. Hist., v. 4, pt. 1, p. 120, pl. 17, figs. 2-5, 7, 13, 31.

Paucicrura regata (Sardeson), Cooper, 1956, Smithsonian Misc. 0011., v. 127,
pts. 1 & 2, p. 957, p1. 157F, figs. 18-24.

Discussion. - This specimen is imperfectly preserved and no interior
may be observed. The external characteristics, however, are sufficient
to warrant placing this Specimen with §;_;gggt_,

Horizon gpg_Locality. - This species has been reported from the Upper
Decorah (Ion Member) and the Lower Prosser in Minnesota and Wisconsin and
from the Aubern Chert in Missouri. The specimen reported here was

found at a depth of 45.3 feet in the Cornell core.

Spegimen Number. - 64b.

 

35

Phylum MOLLUSCA

Class PELECYPODA
Order TAXODONTA
Superfamily NUCULACEA
Genus CTENODONTA Salter, 1851

cmnonorcm OBLIQUA (Hall), 1845

Nucula obligua Hall, 1845, Amer. Jour. Sci. and Arts, vol. XLVIII, p. 292.
Tellinovuya? obligua Meek, 1873, Pal. Ohio, vol. 1, p. 139.

Paleoconcha obligua and E; faberi Miller, 1889, North America Geol. and
Pal., p. 498.

Ctenodonta oblmua (Hall), Ulrich, in Winchell and Ulrich, 1896, Geol.
Minn., vol. 3, pt. 2, p. 604, pl. XLII, figs. 83-87.

Discussion. - The specimen is a very small inner mold. Its size,
shape and other characteristics enable assigmnent to _C_,_ obligua Hall.

Horizon gpg,Locality. - Found in Trenton and Richmond rocks in Ohio,
Indiana, Kentucky, Tennessee, Illinois, and Iowa. This specimen was found
at a depth of 29 feet in the Cornell core.

Specimen_Number. - 41.

36

Class GASTROPODA
Subclass EUGASTROPODA
Superorder PROSOBRANCHIA
Order ARCHEOGASTROPODA

Genus HORMOTOMA Salter, 1859
HORMOTOMA? sp.

Discussion. - The specimen consists only of two coils which are
pyritized. It is referred to Hormotoma because it is rather loosely
coiled, high-spired, and has slightly flattened whorls.

Horizon gng Locality. - This specimen was found at a depth of 25.4
feet in the Cornell core.

Spgcimen Number. - 36.

Genus ECCYLIOMPHALUS Portlock, 1843
ECCYLIOMPHALUS? sp.

Discussion. - This specimen is poorly preserved with the entire
surface covered with euhedral calcite crystals. It is a discoidal species
with the last whorl flaring out. Its general appearance permits a ques-
tionable assignment to the genus Eccyliomphalus.

Horizon and Localit . - This specimen was found at a depth of 45.6
feet in the Cornell core.

Spgcimen Number. - 64.

37
Genus TROPIDODISCUS Meek and Wbrthan, 1866
TROPIDODISCUS Sp.

Discussion. - The specimen is a nearly complete small inner mold
showing no ornamentation. It is assigned to Trogidodiscus on the basis
of its size and angular cross section.

Horizon and Locality. - Found in the Trenton of Eastern United States
and Mississippi valley. This specimen was found at a depth of 98 feet
in the Cornell core.

Specimen Number. - 131.

Phylum ARTHROPODA

Class TRILOBITA
Order PTYCHOPARIIDA
Suborder ASAPHINA
Superfamily'ASAPHACEA
Family ASAPHIDAE
Subfamily ISOTELINAE
Genus ISOTELUS DeKay, 1824

ISOTELUS GIGAS DeKay, 1824

Isotelus gigas DeKay, 1824, Ann. Dye. Nat. Hist., New York, vol. 1, p. 176,
pl. 13, figs. 1 & 2.
Discussion. - Two specimens that consist of only parts of hypostomata

were found. The characteristic imbrication of this structure serves to

identify the species.

38

Horizon and Locality. - Reported from Middle and Upper Ordovician of
North America, Siberia, Northern EurOpe, and Greenland. The species is
common in the Trenton of Michigan and Ontario. These specimen were found
at depths of 58 feet (% 82c) and 88 feet (8 126).

Specimen Numbers. - 82c, 126.

Order PHACOPIDA
suborder PHACOPINA
Superfamily DALMANITACEA
Family PTERYGOMETOPIDAE
Subfamily'PTERYGOMETOPINAE

Genus CALYPTAULAX
Subgenus C. (Calliope) Delo, 1935
CALYPTAULAX (CalliOps) cf. 0. CALLICEPHALUS (Hall) 1847

Phacogs calliLcephalus Hall, 1847, Pal. New York, pt. 1, p. 247, pl. 65,
figs. 3a-31; Billings, in Logan, 1863, Geol. Surv., Can., Geol. Canada,
p. 187, fig. 184.

Ptegygometopus callicephalus (Hall), Clarke, ip,Winchell and Ulrich, 1896,
Geol. Minn., Final Report, 3, pt. 2, Paleontology, p. 731, figs. 51,

52. p. 732-

Cglliops callicephalus (Hall), 1935, Eelo, Journ. Paleon., vol. 9. p. 402-
420, figs. 1-45.

Cglyptaulax (Calliops) calliceghalus (Hall), 1959, Harrington et al.,
Treatise on Invertebrate Paleontology, pt. 0, Arthropoda 1, p. 492,
fig. 389, I108. Ba-O.

Discussion. - Two specimens, one a pygidium, the other a cephalon,
are doubtfully referred to as_Q;,callicephalus (Hall) on the bases of

their gross appearance and the common occurrence of this Species in Trenton

39

and Black River rocks of Minnesota, Michigan, and Ontario. Both specimens
are in poor condition.

gggizon and Locality. - Found in Trenton and Black River rocks of
Minnesota, Michigan, and Ontario. These specimens were found at depths
of 88 feet (# 127) and 207 feet (a 295).

Specimen Numbers. - 127, 295.

SUI'fl-EARY AND CONCLUSIONS

Summary

Though many of the fossils recovered from the core are poorly pre-
served and others not diagnostic, some stratigraphic correlation can be
made and some conclusions as to ecologic conditions at the time of depo-
sition of the core can be drawn. In strong contrast to the highly fossil-
iferous upper hundred feet of the core, below 100 feet fossils are very
scarce, a condition which Hussey (1936) noted in the outcrop of the Black
River. The rock types of the core below 100 feet are dense limestone,
dolomite, and sandstone none of which are usually very productive of fos-

sils, but even in shaly partings fossils are lacking.
Conclusions
Stratigraphic Implications of the Cornell Core

An attempt has been made with Figure 3 and Figure 4 to summarize the
paleontologic findings of this investigation.

One of the objectives was to establish the Trenton - Black River
contact in the core with paleontologic evidence. Between the depths of
123 and 127 feet three diagnostic brachiopod species occur. Idiospira
panderi (Billings) was found at a depth of 123 feet. This species has
been reported only from the Trenton over a wide area including New York,
Ontario, Quebec, Kentucky, Missouri, and Iowa. Stroohomena filitexta
(Hall) was found at 123.5 and 127 feet. Wilson (1946) has reported this
species from the Leray Beds in Ontario but Cooper (1956) states that this
species has never been found in Chaumont equivalents except for Wilson's

report so feels that perhaps the identification was incorrect. Zygospira

40

41

cf. §&,ELONGATA (COOper) was found at a depth of 124 feet. §;_elongata
has been found only in the Lebanon Formation (Black River) in Tennessee.
The depth at which it was found in the Cornell core lies between the two
occurrences of S; filitexta but, since the referral to Z;_elopgata was
doubtful, little significance can be attached to its presence. Hussey
(1952) reports S; filitexta very common in the beds that he calls the
base of the Trenton. At 127 feet in the Cornell core S; filitexta occurs
in a relatively thin bed with many other fossils in random attitudes.

0n the basis of the above evidence this writer would place the Trenton -
Black River contact at 127 feet. A review of the work of Hussey (1952)
and Dixon (1961) will supply further evidence.

Dixon (1961) places the Trenton - Black River contact at 117 feet
because of a conglomeratic bed found at that depth. The first unit below
his contact is a limestone - shale unit, 15.6 feet thick, which is fossil-
iferous and more like the majority of the Trenton above it than the Black
River below. Hussey (1952) states that at the Chandler Falls area, which
is the type area for his basal Trenton Member, zone 2, "may be the base
of Trenton." Zone 2 at Chandler Falls is three feet thick and the con-
glomerate above it (zone 3) is five feet thick, the top of which marks a
disconformity. According to this, the base of the Trenton could be as
much as eight feet below the contact established by Dixon. Hussey (1936)
also says that:

"the most fossiliferous part of the Trenton
is the first three or four feet immediately
below the conglomerate."

The writer regards the entire Trenton section (0 - 127 feet) as the
Chandler Falls Member.

The most significant thing paleontologically about the rocks below

42

127 feet is the scarcity of fossils. They are virtually non-existent.
There were only two species found between 127 feet and 415 feet that are
of any significance. A possible 9320p1ecia sp. was found at 162 feet.
If the identification is correct then that may mean that the zone where
it was found at least is Black River. Its preservation is so poor that
little importance can be attached to it. Rhabdochitina? minneso ensis
Stauffer was found at depths of 162 feet, 170 feet, 173 feet and 183 feet.
Stauffer (1933) reported this species from the bottom five feet of the
Decorah Formation in Minnesota. This would be the Specht's Ferry Member
which Kay (1935) says is basal Trenton in age while Cooper (1956) says
it is Black River in age. In 1933, when Stauffer first reported this
species, the lower part of the Decorah was considered to Black River in
age. As late as 1955 (Collinson, 1955) no one had reported any other
occurrence of this Species in North America. In 1960, Taugourdeau report-
ed this same species from the Silurian of the Sahara. If this is correct
then any stratigraphic value of Rgltmippesotensis is in doubt though the
North American occurrence of this form may be vertically more restricted.
The lowermost fossil found in this core was Dicellomus politus an
inarticulate brachiopod of Upper Cambrian age which was discovered at
a depth of 415 feet. This supports Dixon's conclusion that the t0p of

the Lodi is found at that depth.
Ecologic Implications of the Cornell Core

Hussey (1952) and Dixon (1961) have both suggested that the Cornell
area in Trenton - Black River time was a shallow sea with a fluctuating
‘water level that sometimes left the sediments near shore uncovered.

Hussey has reported ripple marks and many intraformational conglomerates.

z+3

Dixon also reports many intraformational conglomerates. This writer
believes that the paleontologic evidence of the Cornell core supports
this theory.

There are many highly fossiliferous zones such as those at 56 feet,
68 feet, 77 feet, and 78 feet, 100 feet, and 127 feet. Some zones have
partially silicified fossils. The fossils which belong to many classes of
invertebrates, are in attitudes suggesting a thanatacoenosic situation.
This would seem to indicate that the sea level was subject to rather sudden
shallowing as might occur*in a near-shore environment.

An investigation of the paleoecology of the fossils found may prove
helpful at this point. All of the specimens recovered are of neritic
benthos habit and all but the conularids are sessile forms. The Cambrian
oboloid brachiopod found at 415 feet was probably an inhabitant of the
shallow neritic zone, even perhaps stagnant water (COOper, 1936). The
Rhabdochitina of the 180 foot zone is considered to be an inhabitant of
the reducing environment (Collinson, 1955). The carbonaceous character
of the rock at this core depth supports this interpretation. The
strophomenid brachOpods (Rafinesquina, Sprophomena, etc.) are adapted for
living on a muddy bottom--their structure allows them to extract more
oxygen from the water (COOper, 1936). Bryozoa need clear water and a
hard substratum to survive (Elias, 1949). The more streamlined and the
more rotund forms of Brachiopoda (i.e. Zygospira and Rostricellula) would
indicate an environment of clear, moving water (COOper, 1936).

Using the above particulars and the core lithology one can erect an
ecological sequence for the Cornell core. The sediments of the core from
the bottom to the 80 foot level were deposited in near-shore, fluctuating

seas. This is evident by the Dicellomus, by the Rhabdochitina, by the

~44

  
   
 
  
  
 
  
  
  

0
We: Mn Am
100
mm
We mm
m We
in / Me: to 5 mm
03 m «mm: mm m
Jam mum
games—manila
= 221.
200
Mine? mm
1 alu
300.
/ = Separates specimens found
within one foot interval.
; = Separates specimens found
at same depth.
Vertical Scale 1" a 57'
400
Mam um s
Figure '3. Lithology and peleontology
50° of» the Cornell core.

561 Total upth of Core

 

z+5

strophomenid-type brachiopods, by the oolitic zones, the intraformational
conglomerates, the pyritic and glauconitic zones and the zones of clean
sandstone. Between 80 feet and 60 feet the depositional environment was
probably one of moving water over at least a partially hard substratum.
The environment was probably near-shore since there are zones of macerated
shells at intervals. The fact that bryozoans and zygospirid brachiOpods
were in abundance in this zone is also evidence for this. Above 60 feet
the environment was again one of fluctuating sea level. The bryozoans are
not abundant and the brachiopod p0pulation is similar to the type found

below the 80 foot level.

Regional Correlations

The evidence produced by this core indicates that Middle Ordovician
fauna of the Northern Peninsula of Michigan is closely related to that
of the Upper Mississippi Valley and the Ontario. St. Lawrence Lowland.
Affinities with other areas exist to a lesser extent. Figure 4 summarizes

the relationships in a graphic manner.

Further Wbrk

Further work with the Ordovician subsurface of the Northern Peninsula
of Michigan will depend upon future drilling. It would appear that pale-
ontologic evidence concerning the Middle Ordovician of Michigan will not

be easy to obtain.

46

Area Mich. Upper Ont., Ap Tenn.& Okla
Species Basin Miss. Can. Area Ky. . Area

Rhabdochitina? min 0 en ‘ Obr?
Metnconularia calderi 0t
Conularia tonens
S , elasma ornicul

atostoma nchelli
thllopo n sp

r'u a? s

Hespero hi

.ople la? 8

cell otensi

v ospi curvirost
, osnira lon

‘ os i d e

dicsn ra deri

owe sericea

tronhomena ili

.home pp;

fine..uina normalis

-1m winchelli

aucicrura ata

enodo a obli 0t
Tropidodiscus 52;, 0t 0t
Igotelus giges Om Om Om Om

Om Om Om

Om Om

 

Trenton - 0t Trenton and Black River - On
Black River - Obr

Figure 4 GeOgraphic and geologic ranges of Middle Ordovician -
species from the Cornell core.

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4?

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