BIOSERIES OF THE OSTRACODE
PO-NDERODICTYA

IN THE TRAVERSE GROUP OF MICHIGAN

Thesis for the Degree oI M. S.
MICHIGAN STATE COLLEGE
Arthur Emil Wucke'n‘

I950

THESIS

 

SUPPLEMENTARY ’
A .MBIILEOBIQOR '

i‘ \ l .
ll-‘I ’ 'o.. -‘L. ‘ ' - l u.‘ ‘ a J - '— -- - s . . _. >..

This is to certify that the

thesis entitled

WBioeeriee or the Ostracode Punderodictya 1n
the Traverse Group ’of Michigan."

presented by

Arthur B. Wuckert

has been accepted towards fulfillment
of the requirements for

Master's degree in Geolggx

W 63.46%,

Major professor

May 23. 1950

Date

 

I -" 3343's! 1. ‘ '. u '.'-‘ 7' I. " ’15-’35? - V Wr’ .. -W..._-- " ‘ ‘7‘“ ‘ "‘ - “'
'1' ' I ‘ * '.' ' l1, .' ..
'7 N v N (WV, ,3" \'.L a? fight; W1,» 1‘ ‘ a
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n if“ I I"; l" 0 ‘ Ck

 

BIOSERIES OF THE OSTRACODE PONDTRODICTYA

 

IN THE TRAVERSE GROUP OF MICHIGAN

by
Arthur Emil Fuckert

A THESIS
Submitted to the School of Graduate Studies of Michigan
state College of Agriculture and Applied Science

in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Geology
and Geography

1950

THESIS

ACF"“"LTPG'T'WD

The writer wishes to express his appzeciation for
the co ontinuous and invaluable assistance so freely given
V Dr. W.A. Kelly in the laboratory as well as on the
manuscript. I further extend my grateful thanks to our
departr dent head, Dr. S.G. Eergquist, for his helpful ad-
vice in the study and to Dr. B.T. Sandefur for his ex—
cellent help on the hand drawings. Dr. J.w. Trow and
Mrs. J. Smith also improved greatly upon the thesis.
Dr. A.D. Perejda and Prof. R. L. Carmin of the geography
deparment gave helpful advice on the style of the graphs
and map. To Joe Long, a senior student in the department
of geology, the writer is in debt for the drafting of
the location.map.

To Mr. Harold Poulson and Major P. Mellinger the
writer extends his appreciation for the valuable aid on
the PhOtOVTchfilC matel ial incorporated herein. Hr. Rex
Grant and his staff in the Oil and Gas Division of the
Michigan Geological Survey contributed very kindly to

the progress of this paper.

He

TABLE OF COYTFTTS

AcknOWledgemtscoocuecccceace-ecvoccoocdccocovoccoce

List of Illustrations...........................

IntfluCtiODCCOCQCO'CUO(Cf..UO'U'CO‘CU'C"CC'UC'C'OO'.

ObjeCt Of Stud370000CII¢lovdoO'O’o'e'c'IOCOCCCCCCCC'CCOIG

Termin‘Ology—COOCCCCCOCOG0'.CCICOCCCOCCCCOC‘COOCOOCOC

DiSCUSSiOncecacoooccoccccoccocovccccoeccccccvcccocc

MethOG Of PreparationcoceouvcvcecoeocooccctOOOOOOto

Stratigrathoccccoccoecccooeccccooe¢0dccoccaoocoocc

WGllS Examined in the Studyceccocooceoooo¢cccccccoc

Orientation of Ostracodes.........................g

Descriptions of the Type Specimens.................

Introduction to the Graphs................
Results and Interpretations of the Study..
COnCIUSionSoccecccceocdccoeecccaccoccccccc

BibliograpWCCOCOOCC'COCCIOCCCOCC'CCCCCCI’O

O'CCCOCOC

COOCCOCCC

OCICUOCIC

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\1 to 09

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LIST OF ILLUSTRATIONS
Page
Figure I. Columnar Section of Michigan.............. 15

Index Map of St. Clair County in Michigan........... 17

PLATES
Plate I. Photographed Specimens..................... 25

Plate II. Illustrative Sketches of Ponderodictya.... 87

')

GRAPH

1'1

Graph I. Distribution Chart of the 15 Types in the

Traverse Formation......................... Pocket
Graph II. Frequency of the 15 Types in a

Stratigraphic Section...................... 50

Graph III. Biozones Based on the 15 Types........... 31

iii

INTRODUCTION

Microfossils have been.used for several years as a
means of subsurface correlation with special emphasis on
the foraminifera; however, the Michigan basin has very
few of these. Many ostracodes are found in the oil well
cuttings as well as at outcrop locations in Hichigan.
They are rated second only to the foraminifera in strat-
igraphic value.

Glaessner* states:

 

*Glaessner, M.F., Principles of Micropaleontology, Mel-

bourne University Press, Melbourne, Australia, 1945, p. 17.

 

"Locally ostracodes are of greater value than
foraminifera, because of their greater adapta-
bility to a variety of environmental conditions,
including brackish and fresh water habitat, as
well as to the conditions leading to deposition
of dark shales. Micropaleontologists are in-
clined to place the ostracodes second in strat-
igraphic value, after the foraminifera."

Ostracodes are an important group of microfossils in

the Paleozoic era.*

 

*Kelly, W.A., Personal communication.

Of the many genera found in the Devonian formations of

Michigan, Ponderodictya appeared to be the most abundant;

 

therefore, it was chosen for this bioseries or phylomorpho-

genetic study. According to Glaessner,*

 

*Glaessner, M.F., 22, cit., 1945, p. 81.

 

the sequence of evolutionary stages of each morphologic
character or feature is a bioseries. Any subdivisions or
zones of a stratigraphic column based on the evidence of
bioseries are known as biozones.

This research method has been and is now employed by
several workers in.paleontology. After citing several

xamples of such.work Jeletzky% says:

a

 

*Jeletzky, J.A., "Some Nomenclatorial and Taxonomic Problems
in Paleozoology," Journal of Paleontology, Vol. 24, No. 1,

1950, p. 27.

 

"The tendency to discard specimens as a foundation
of paleozoological species and to use fossil pop-
ulations (i.e. series of specimens assumingly
representing these) contributes considrably to

the phylogenetical method and makes-it much more
exact. It seems to be sufficiently evident that
the old phylogenetical concept of tphylogenetic
lines! did not represent the true character of
paleozoological evolution. The fact that in all
numerous cases when paleozoological material is
more or less plentiful and evolutionary series
continuous we observe not 'lines!, but tphylo-
genetical fields! or 'plexus' is very significant,
It may be safely assumed that these concepts re-
flect much more correctly the character and course
of evolutionary processes than the concept of
'phylogenetical lines'."

(3‘3

In accord with the above, the writer has employed the
subspecies, or variants, as a basis for classification
rather than the conventional and empirical catagorizing of
the species into specific geologic time spans. This method
embraces the 'phylogenetical field! concept referred to by
Jeletzky above. Furthermore this method testifies to the
contemporaneity and ancestry of the several variants of

Ponderodictyawhich comprise its populations manifested

 

in the Traverse formation.

OBJECT OF STUDY

The object of this study is determine whether there
is evidence of one or more bioseries in the single ostra-

code genus, Ponderodictya,and with the evidence obtained

 

for such bioseries, to Subdivide the Traverse ostracode

zone into as many biozones as may be distinguisned.

TERTIHOLOCY

Carapace is the entire shell or fossil composed of two
halves, a right valve and left valve; often referred to

as the test.

Flanges are located in the anterior region of Ponderodiegya,
being linear ridges, often arcuate. Some may app~ar merely

as nodose structures. (Pl. I, Fig. 1,2; Pl. 2, Fig. 1,5.)

Hingement. In Ponderodictya the valves articulated about

 

 

J.)

an axis directed through the more convex dorsal margin.
The interlocking of the valves at this position is a
rabbeted contact of the ridge and groove type.* (Pl. I,

Fig. 1,6.)

 

*shimer, H.W., a Shrock, E.R., Index Fossils of Berth

America, J. Wiley & Sons, Inc., new York, 1947. p. 685.

 

Mamelons are intermediate be ween nodes and monticules.

Marginal overlap_is a feature where one valve overpaps

 

he other along the free margins, he larger one may have
a groove for receiving the edge of the smaller. (Pl. I,

Fig. 2,4,8; P1. 2. Fig. 2,5.)

Monticules are of lower relief than nodes, having a large

 

diameter and very little height. This term differs from

the general usage and is here initiated with the above de-

finition. (Pl. I, Fig. 2.)

Muscle scar is udhlly located in the central region on

 

the side of the valve of Ponderodictya, it has much the
appearance of an old vaccine scar. (Fl. I, Fig. 2,7; Pl.2,

Figd 1,2,3.)

Nodes are a variation from the spines; being broader and
of lower relief than the spines. The height is about equal

to the diameter. (Pl. 2, Fig. 5.)

Fitting is a type of ornamentaion of the surface of the
carapace. It is used in this paper to describe a condition
where the area of the pits is smaller than the space between

them. (Fl. 2, Fig. 5,4.)

Plenation. The plenate end is the end toward which the

 

swing of the shell is directed, andwhich tendsto be full
becadse of the greater area of the region extending beyond
the hinge. The degree of plenation is a composite effect

of relative height of the ends, relative projection beyond
the limits of the hinge, and relative fullness of the ventro-
adplenate, as compared to the ventro-antiplenate portions of

the shell.* IPl. I, Fig. 1,5,15; Pl. 2, Fig. 1,2,5.)

 

*swartz, F.M., & Oriel, 3.8., Journal of Paleontology, Vol.22,

No. 5, 1948, p. 546.

Feticulation is the opposite of the condition for pitting,

 

. . . ,_ , ._ ,_ . r- _.
1.e., the ple are broader than the intevening spaces,
which may be ordy ridges separating the pits. (P1 I,

Fig. 1, 2.)

Shoulders_maj take the place of flanges, where the sides

 

of the valves converge abruptly toward the margins. Some

specimens even lack the abrupt shoulder. (Pl. I, Fig. 6,12.)

g

Spines are structures that appear norially in the poster-
ior region of Ponderodictya and have a length greater

than the d'ameter normal to the length. (Pl. 2, Fig. 2.)

DISCUSSION

Ostracodes comprise a subclass of bivalved marine crust-
acea, which average from 0.5 m.m to 4 m.m in length. One
group, the Leperditacea, not used in this study, attain a
length.of some 25 m.m. The two valves of the carapace are
joined at addrsal hingement, about which they articulate
in.life. AS the writer will demonstrate in this study, the
external surface of the valves may have various types of
morphologic features and degrees thereof; or the sufface
may be void of superficial ornamentation.

These variations in expression of morphological
characteristics are the criteria with which the biozones

are delineated. According to Glaessner:%

 

*Glaessner, M.F., o . cit., 1945, p. 225.

 

"When it is found that the stages in the progre-
ssive structural development of morphological char-
acters follow each other in numbers of individuals
taken from successive beds in a stratigraphic
sequence, then their order of appearance supports
the phylogenetic interpretation oflthese stages
while, concurrently, the possibility of establish—
ing phylogenetic relations between.them supports
the classification of the stratigraihic sequence

of biozones."

In this present.study it is not claimed that the
aurorae of the several bioseries arecomplete within the
Traverse group, but the statistical examination of the

frequency of occurrence of mutations should indicate the

existence of at least one hemera or point of peak develop-
ment in the stratigraphic column.

An aurora is the geologic time interval from the
actual appearance bf a mutant in a bioseries to its sub-
sequent disappearance or replacement by a successive
mutant. An aurora is not necessarily completed within
the short interval of geologic time as represented in
the Traverse formation.

Further studies on the formations directly above and
below the Traverse group might easily discover biostrati-
graphic divisions that integrate perfectly with the divi-
sions that are evident from this study. As Tan Sin Hok*

states:

*Tan Sin Hok, "The Results of Phylomorphogenetic studies
of Some Larger Foraminifera", De Mg, in Ned. Indie, 6, (IV),

1959, p. 95.

 

"The biostratigraptic value of phylomorphogenetic
researches is that they mean a methodical search
for index fossils, and that they also enable us to
establish a series of time markers in.which the
geologic time is recorded in a gapless manner,

as the consecutive terms of the same bioseries
represent a rational and continuous sequence.

Such a paleontological chronometer is of utmost
improtance, as by means of it, other forms can be
dated independently."

The biozones, representing a continuous series of
stratigraphic units in.the Michigan.synclinorial basin,

may be correlated_by further work in some other region

10

that has a similar and fairly continuous section of Paleo-
zoic formations. This w uld be limited to sediments of
marine origin such as the section in New York or Illinois.

The question has been asked whether or not a geograph—
ically restricted environment could be a dominant factor
affecting the variations and mutations that give rise to
the bioseries. For example, if a stratigraphically contin-
uous series of ostracodes in the Illinois basin had been
subjected to a much different environment than.a series in
the Michigan basin, the two faunal series may by assumption
be highly different in types of ornamentation, in degrees
of expression, and in time interval of occurrence; morpho-
logic features typical in the series of one basin for a
definite time interval or biozone may never occur or at
least be much different in the faunal series of the other
basin. Furthermore, in.harmony with the assumption, the
same set of features may occur in a time interval other
than that of the first found series. If this assumption
were the case, then the projected correlation over the
continent would not be a reliable method even if there were
any hints of correlation trends that appeared to corroborate
the empirical method. The latter method is that of arbi-
trarily chosen ranges for species which is and has been re-
lied upon quite heavily by geologists for many years.

According to Glaessner,*

*Glaessner, M.F., op. cit., 1945, p. 226.

11

"The stratigraphic value of morphogenetic stages

would be very limited if the rate of change from

one stage in a bioseries dt’the next depended

largely on local environmental factors. Tan Sin

Hok has considered this possibility and has found

indications that the effect of such influences is

rather limited. For example the stages of evolu-

tion of nepionic characters in some foraminifera

were reached in Southern Europe and in the Indo-

Pacific region at the same time."

For an illustration in the ostracodes, the co-existing
faunal series of the Illinios and Michigan basins will
suffice. If the two series of fossils from these two basins
or any other two or more basins of marine sediments of
similar age were compared on the basis of bioseries and
biozoning, it is highly probable that the same combinations
of morphologic features will be present in each of the
faunal series in every basin in similar geologic time inter-
vals. These morphologic features should invariably show
the same frequency of occurrence in.a1l basins.

This discussion is summarized Very well in Glaessner'sw

words,

 

*Glaessner, M.F., op. cit., 1945, p. 226.

 

"Since it is improbable that evolutionary

changes varying inspeed under the influence of
environment can produce, under different circum-
stances and in different regions, the smme combin-
ations of bioserial stages in a number of CG-
existing species (popuiations), the actual occurr-
ence of such combinations would strengthen the
case for the stratigraphic application of the
morphogenetic method."

12

METHOD OF PEEPiFATION

Practically all of the well cuttings examined in
this study are he washed and bottled sets of the Mich-
igan Geological Survey. Most of the rock samples were
suitable for study under the binocular microscope, but
occasfhally it was necessary to crush the larger rock
pieces or to wash away excess drilling muds in order to
recover any specimens otherwise undetectable.

The contents of all the bottles covering the Traverse
formation in all the wells were examined to pick out the

ostracode genus Ponderodictya for mounting in stratigraphic

 

typ slides. The state well—permit numbers and depths
were recorded on each slide immediately.

After all of the available wells in the St. Clair
area had been checked, the mountedspecimens were again
examined to obtain a control set of type specimens which

a.

exemplified the sundry morphologic structures and their

variations necessary for the bioseries study.

STRATIGRAPHY

The writer here presents the Traverse* section as
described in a well log from the St. Clair area. The lith-
ology recorded in this log is typical of the well cuttings
examined in this study. In many wells the footage inter-
vals were somewhat more constant than the record below
would indicate; so that, for example, thirty feet-of shale
as seen in.this type of log, may be represented by three

or four samples in the bottled sets.

Devonian, Traverse: Thickness Total
in Feet Thickness

Limestone, black, hard 2 2
Limestone 8 10
Limestone, gray black 6 l6
Shale, black 12 28
Limestone, buff and gray, fossiliferous;

some gray limy shale 20 48
Shale, black 10 58_
Chert, limestone, gray % 59:

n n n % so

Shale, gray 8 68
Limestone, gray brown 10 78
Shale and limestone, gray 10 88
Limestone, gray, brown, dense,fossil-

iferous, some shale, Chert, and

secondary calcite 15 105
Shale, gray, soft 6 109
Shale, and limestone 5 112
Shale, gray and soft l 115
Limestone, brown, buff, dense; secondary

calcite 7 120
Limestone, brownish-gray, dense, shaly;

gray shale 10 150
Limestone, gray-brown, dense, fossiliferous 4 54
Shale, gray, flakey and muddy, limy 19 155
Limestone, gray-brown, dense, fossili-

.ferous; some shale and seconday

calcite 15 168

*See Colunnar Section, Figure I

Devonian, Traverse cont'd Thickness Total
in Feet Thickness

Shale,ssft, gray, limy 55 225
Limestone, gra.y-brown, fossiliferous,
gray shale 10 255

Limestone, gray, fossiliferous, gray

muddy shale 15 2é8
Limestone, brown, fossiliferous 5 255
Limestone, gray and buff, some gray

shale 5 258
Shale, gray, soft 5 265
Limestone, brown, fossiliferous 5 268
Shale, light gray, soft 10 278
Limestone, brown, fossiliferou3 pyrite,

brown flaky shale 55 515
Shale, gray, flaky, soft, limy; pyrite 5 518
Shale, light gray, soft and powdery 5 525
Shale, gray, flaky, limy; pyrite 50 555
Shale, gray, flaky, limy, fossils

pyrite 5 558
Limestone, gray, many fossils, a little

,gray shale; pyrite 10 568

 

15

GENERALIZED COLUMNAR SECTION OF MICHIGAN
MICHIGAN GEOLOGICAL SURVEY DIVISION

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SYSTEM. SERIES ORMATION.GROUP LITHOLOGY THICKNESS ECONOMIC PRODUCTS
, RECENT
SAND. GRAVEL.CLAY, boulders, _ SAND. GR AVEL. PEAT. MARL.
PLEISTOCENE GLACIAL DRIFT mm 0 IOOO FRESH WATER
"PERMO-CARBONIFEROUS" "RED- BEDS" SHALE,CLAY, SANDY SHALEmsu
GRAND RIVER SANDSTONE.sandy shale Bo -95 BUILDING STONEFRESH WATER
PENNSYLVAN'AN SAGINAW SHALE,SANDSTONE,IImesIone,coa| 20-535. ggf‘NLEE-CEBQL'FRESH “I“
LIMESTONE. SANDY OR CHERTY
BAY PORT \ LIMESTONE,SANDSTONE 2-I00 LIMESTONE,FRESH WATER
MICHIGAN SHALE.gypsum,anhydrIIe.sandstone 0-500 GYPSUM
"MICHIGAN STRAY“ SANDSTONE 0-Bo GAS
_ FRESH WATER. BRINE
MISSISSIPPIAN MARSHALL SANDSTONE.sandy shale I00 400 BUILDM STONE
COLDWATER SHALEJandSIOI-w.lumesIone 500 -||00 SHALE. FRESH WATER
SUNBURY SHALE O-l40
BEREA-BEDFORD SANDSTONE, SHALE 0-325 GAS.0IL
ELLSWORTH- ANTRIM SHALE, lImesIone IOO‘950 SHALE, GAS
TRAVERSE LIMESTONE. SHALE Ioo-Boo ggI‘EESEI‘ajfitg'L-GAS-
ELL SHALE. Limestone 0-80 SHALE
ROGERS CITY-DUNDEE LIMESTONE 0-475 L'MESTONE- O'L-G‘S'
DEVON IAN ' LEMEESSII'OI’NAETEDROLOM ITE
DETROIT RIVER engmLTE-“M'°"-”" ISO-I400 OILGASS'ALT, BRINEI
Y FRESH WATER
SYLVANIA SANDSTONE.SANDY DOLOMITE 0-550 GLASS SAND. FRESH WATER
BOIS BLANc DOLOMITE,CHERTY DOLOMITE o-Iooo
BASS ISLAND DOLOMITE 50-570 DOLOMITE. FRESH WATER
SALINA SALT. DOLOMITE. Shaleanhydme 50-4000 SALT. GAS. OIL
NIAGARAN
SILUR'AN Guelph-Lock orI-Engadme) DOLOMITE L , h I l50’800 LIMESTONE DOLOMITE'
MamsIIque-Jurnt Bluff) " ”"3 000.5 ' ° OIL. GAS. FRESH WATER
CamacI
CINCINNATIAN
Michmpnd) Ed ) SHALE, LIMESTONE 250'800
ORDOV'C'AN 01va I. m OI GAS LIMESTONE
TRENTON-BLAGII RIVER LIMESTONE. DOLOMITE zoo-I000 ”LE-SH WATER -
ST PETER SANDSTONE 0 - I50 FRESH WATER
OZAORKIAN PRAIRIE DU CHIEN DOLOMITE. Shale 0 - 4l0
R
DOLOMITE. SANDY DOLOMITE. -
CANADIAN HERMANSVILLE ”mm. I5 500
“I“? .SUPER'OR BUILDING STONE
CAMBRIAN Momma? SANDSTONE 500-2000 FRESH WATER
Jacobs" lo)
(Coppnlormfions) shalcmndstm SEMI-PRECIOUS GEM STONES
I KILLARNEY GRANITE GRANITE.GNEISS,dIorII¢.:y¢nII¢
ALGONKIAN HURON“ SLATES.HEMATITE. SCHIST, IRON ORE. ROOFING SWE-
(Im mmfim) OUARTZITE. GRANITE.m5I.. 2000+ ROAD NETAL, GRAPHITE
dolomite MARBLE
ROAD METAL. BUILDING
T LAURENTIAN SGHIST. GNEIss. GRANITE STONE,YER0E ANTIQUE.TALC.
ARCHEAN GOLD
AEENATIN SEAT? “REE"STOM- ROAD METAL

 

FIGURE— I

 

Countv

St. Clair
I!
n
I!
I!
I!
H
I!
n
I!
I!
I!
I!
n
H
I!
N
n
Y!
I!
fl
'1
H
n
"
I!
I!
fl
1!
fl

Sanilac

TTLL

C

Ontario Wells:

Lambton
N

Y!

*Morton's Salt

n ‘T‘l'd’ xv ‘w-Yh a? “h
» AEAMIH.W Tw Tkw .
' __J-'~.l-L.A - --_ ”A _.L. ...*__< L

16

Township

 

Ft. Gratiot
Clyde

Pt. Huron
Grant
Clyde

Wales
Cottrelville
Burchville
Ft. Gratiot
Burchville
Wales

Ft. Gratiot
Kenockee
Kimball
wales

Pt. mron
Burchville
Clyde

Clyde

Ft. GratiOt
St. Clare
Pt. Huron
Clyde

Ft. GratiOt
Clyde

Pt. HUron

IPt. Huron

Pt. Huron
Grant
Grant '
Fremont

Shore
Zombra
Zone

#11, no state permit number.

State Permit

 

Number

15841
15922
11001
1595
1562
15072
14755
14847
15028
12055
14969
5926
15702
14072
14558
5068
5526
6199
7860
8990
9271
M.S.ll*
4720
5855
6584
4671
5204
4294
2517
1595
10918

7

 

RI3E RME RISE RISE

   

,I05I8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

r" - ‘ —__I_‘—T”* (n-1,.--

. , I a I I
g | I I .1395 .I2035
"' I I '25I7 Imam

. ,
r— ~
I I I
z I I
N I I ’I3702 * “4720
I" l I I ”3922 . I
.L _ I I 6:659 7830
I ' I4358 I
z I I
t O I5072
I' I I4072
l _ ' I4969
.. - I 4_2%
S 1
INDEX MAP SHOWING ‘-
ST. CLAIR COLNTY IN
MCI-IIGAN
z
c-
9.4? ..

.2»

E, I—

g4

E

 

 

 

o z 4 6 t‘
-=—=—==‘
su'ruTE MILES

 

: WELLS EXAMINED FOR PONDERODIOTYA IN THE ST. CLAIR COUNTY AREA

M LO“.

 

‘

ORIrLTATIO? or OSTPACOLES

Glaessner*

 

*Glaessner, M.F., on. cit., 1945, p. 15.

m

 

outlines the problem that exists on the subject of orient-
ing ostracodes.

"As there is no obvious relation between the

shape of the test (fossil) and the internal

anatomy of living ostracodes, the characters

considered as distinguishing the anterior and

posterior ends of the shell are not genreally

accepted in the same sense by all students of

Palaeozoic ostracodes."

For the specimens examined in this study it was de-
cided to designate the relatively more bulbous end as the
posterior, (see Plate 2.) which usage is widely employed.
This is often referred to as the plenate end. The more

is.
pointed, streamlincdfis the anterior or antiplenate. The
portion of the margin.which is more convex, and which also
lacks overlap in several of the varieties, is the hinge
area as well as the dorsum. The relatively straight portion
of the margin opposite the dorsum is the venter. If the
Observer tips the specimen up on its venter with the pointed
anterior end facing away, the valve on the observer's left
is the left valve, and the one on his rigzt becomes the
right valve. This latter valve is smaller and is overlapped

by the left valve along the margins as described for each

ype in the control set.

19

quanpTlovo OF THE TYPE FPECIETFQ

EII CIVJP'l (Fig. 5)%
Carapace oblong—ovate; left valve overlaps right
on entire ma rgin,except at the posterodorsal portion;
dorsal margin arched, ventral nearly straight; indistinct
anterior flange on right valve; muscle scar not very pro—
nounced; surface of right valve quite reticulate; left
valve smoother than right valve; no evidence of spines

on either valve.

SP} CI‘VP 2 (Fig. 5)

Carapace subquadrate in outline; pitting on entire
surface very fine; left valve slightly larger han.right
valve, overlapping the latter rather weakly on the entire
margin except on the posterodorsal portion where there
is no overlap; a very indistinct ridge or shoulder on the
anterior portion of the right valve; muscle scar weakly

expressed; one nodose spine pr sent on lower left portion

of right valve.

SrECIIEN’ 3(Fig. 6)

Carapace subquadrate in.outline much like "2"; this
specimen is shorter and wider, also has a straighter ventral
line than "2"; left valve only slightly larger, overlaps
right valve weakly; no overlap on the posterodorsal or an-
terior margins; line of juncture forms a projecting prow

aThe pictures appear on Plate I.

D

at the anterior (antiplenate) end; anterior shoulders Oi
both valves converge abruptly to the anterior margin; the
muscle scar is very indistinct; pitting appears quite fine;
two tiny nodose mamelons in the posterodorsal and poster-
oventral quadrants of the right valve; a very waak anterior

flange is present on right valve.

SPECIHEf'é (gig. 8)

Carapace similar to "l", oblong-ovate, but on this
specimen the anterior flange ofthe right valve is a low
linear ridge rather than a spinose structure; one post-
terior mamelon is prominent on the lower portion of the
bulge of plenation of the right valve; left valve retic-
ulate but has no other structures; overlap not prominent,
entirely-lacking along the posterodorsal portion of the

margin; muscle scar is only moderately expressed.

SPECIMEN 5 (Fig. 2)

Carapace much like "4", subquadrate; conspicuous
overlap of left valve over right valve, except within the
posterodorsal portion of the margin; muscle scar smooth
and distinct, anterior flange on right valve very promin-
ent, somewhat lunar; two distinct posterior monticules;

both valves reticulate; dorsal margin somewhat less arcned

than that of "4"; ventral margin nearly straight.

F)
Ia

SPECIMFN'B (Fig. 12)

Carapace larger than, but similar to "5"; left valve
moderately overlaps right except on the posterodorsal
slope; dorsal margin arcuate; ventral nearly straight;
anterior shoulder of right valve bold, but not expressed
as a flange; one nodose spine on the lower left portion
of the right valve; muscle scar indistinct and shallow;
left valve smoother than the right which is moderately
reticulate.

SPECIMEN 7 (Fig. 4)

Carapace sub-elliptical; dorsal margin arcuate, ven-
tral nearly straight; left valve larger than right, over-
lapping the latter strongly along the margin.except in the
posterodorsal portion; muscle scar very shallow and in,
distict; pitting quite weak over entire carapace; no spines
present; the anterior half of right valve slopes gently
down.from the center to the anterior margin; no flanges or

bold shoulders present.

srrcnmr a (Fig. 14) ‘

Carapace like "4", oblong-ovate, though.more ellip-
tical; left valve larger, overlaps right valve along entire
margin.except on the posterodorsal slope; lacks any an.
terior flange or shoulder; one monticule on the lower left
portion of the right valve; distinct reticulation on.both

valves; muscle scar smooth and very distinct.

¥0
LU

SPECIMEN 9 (Fig. 11)

Carapace similar to "2", subquadrate in outline;
overlap very prominent and evident along er tire margin;
one very prominent mamelon in the postal oventra 1 region of
the right valve; the anterior ridge is bold BEL slightly

pointed; muscle scar smooth and indistinct; reticulation

well expressed over entire carapace.

SPECIMEN'lO (Fig. 9)

Carapace oblong-ovate with left valve overlapping
right very markedly except on the posterodorsal portion;
dorsal margin.arched; ventral margin nearly straight;
muscle scar extrez Ml} weak; two rather ind is inct post—

erior monticules and a much depressed anterior ridge on

the right valve; surface only moderately pitted.

SPECIMEN ll (Fig. 13)

Carapace outline much like "10", oblong- ova te; left
valve larger than an d overlapping right valve except on
the posterodorsal portion; dorsal margin arched, ventral
margin nearly stI*aight; two posterior ma melons on right
valve; the right valve lacks the anterior shoulder and
slopes gent ' down to the anterior margin; a spinose
ridge is located on theis anterior slope of the right
valve; muscle scar smooth and rather weakly develop ed; fairh

well-pitted surface.

I‘D
CQ

SPECIMEN 12 (Fig. 7
Carapace subquadrate similar to "5"; left valve larger
than right with overlap on all margins except along the
posterodorsal portion3-dorsal margin.moderately arched;
ventral margin straighter than in "10"; one monticule in
the center of the lower left quadrant of right valve; the
anterior flange is rather weakly developed; the muscle scar

is quite smooth and shallow; surface moderately pitted.

SPECIMEN’IS (Fig. l)

Carapace subquadrate in outline more like "12" than
"5"; left valve larger than right with prominent overlap
on entire margin.except along the posterodorsal porti n;
dorsal margin moderately arcuate; ventral margin nearly
straight; a posterior minticule present on the right valve;
a very bold anterior flange on right valve and an indis-
tinct anterior ridge on left valve; muscle scar distinct

and smooth; reticulation distinct on both valges.

a:

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PLATE II

All three sketches exhibit a definite swing or plen-
ation to the left or posterior. They may be reticulate

or pitted; nodes may be replaced by monticular mounds.

Fig. l. R'ght valve; anterior ridge, moderate overlap,
distinct central muscle scar, no posterior
spines, convex dorsal margin, straight ventral
margin.

Fig. 2. Right valve; prominent anterior shoulder, no
flange, 1 posterior Spine, muscle scar, distinct
overlap, arcuate dorsal and ventral margiHS.

Fi«. 5. Right valve; prominent overLap, lunar anterior
ridge, 2 nodose posterior spines, m sole scar,
dorsal margin much more arched than ven.ral.

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INTRODUCTION TO THE GRAPES

Of all the wells examined in the study the twenty one
that had a minimum of poor features, as missing intervals,
were graphed to illustrate the distribution of the type
variants counted. he base of the Antrim shale is the top
of the Traverse formation, which is used in this study as
the marker horizon below which the depths in feet an in
negative elevations. This feature is recorded on all
three graphs on the extreme left, and it also serves as
the vertical or stratigraphic scale on the graphs. The
same portion of the Traverse formation is shown on all the
graphs, to preclude any confusion when the graphs are com-
pared. Since there is no appreciable variation in the
thickness of the Traverse formation in the small area
studied, it was possible to draw an approximately straight
base for this formation, which line also serves as the top
of the Dundee formation. (See Fig. I, p. 15.) The Bell
formation shown on figure I has been included as part of
the Traverse formational group, because the two are not
easily differentiated. This is shown.to be true also by
the absence of the Bell on the driller's log.

Graph I (in pocket) shows the frequency in numbers of
the variants throughout their vertical extent in twenty on e
wells. As indicated in the legend each type variant has
a different color, but the size of the geometric symbol

expresses an absolute number of the specimens at the proper

29

elevations. At the extreme right on graph I are the
conventional zones based on the various combinations of
faunal assemblages throughout the column examined. The
length of the vertical line for each type variant expresses
the upper and lower limits of the respective t'pe.

Graph 2 (p. 50.) is not a group ofwells but rather the
thirteen type variants of Ponderodictya plotted to show the
percentage of the total number of each type that occurs at
any given elevation. The points of highest percentages as
well as the second highest points for each type variant
have been plotteistratigraphically on graph 5 (p. 51.) as
major and minor highs. They appear as large and small
circles, from which horizontal lines are shown projected
to the right side. The lines projected from the large
circles limit the major zones which are lettEd; the small
circles or minor highs subdivide the major zones into
minor zones which are numbered.

In summary, Graph 5 illustrates the biozones previous-
ly defined in contrast to the stratigraphic range zones

shown on graph I.

 

 

 

 

 

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A STRATIGRAPHIC SECTION SHOWING FREQUENCY IN PERCENT OF THE l3 TYPES OF PONDERODICTYA

FROM 2| WELLS IN THE ST. CLAIR COUNTY AREA

GRAPH 2

 

 

31

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIOZONES IN THE TRAVERSE FORMATION BASED ON
THE FREQUENCIES OF THE I3 TYPE SPECIMENS
FEET TYPE bI’ELIMENS MINOR MAJOR THICK‘
I00 I 2 3 4 5 5 7.-..‘8_.__9 -10-.-”.-.-I2.._I;?________,_ ZONES ZONES NESS 4
I r I— I I BARREN
__ _ _ ._ ._ __ __ __ _._. __ ._ __. __ ____ __ ._ ‘4‘
I 5 30
I
I I
7-I——-———————-———-——-—-———--r———-——« K
I50 I___'___________ ______ 4 ‘
l T 3 IO
i
I I I
I I I J
uJ' I I
:I I I 2 60
a - I I
. 200 l {- I
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E "_.._.__.,_______. ______ I_.._A
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___-_...--.._...__.._____... _____ r__._.___‘--
400 BARREN
TOP OF DUNDEE
FREQUENCY POINTS! O:MAJOR HIGHS o: MINOR HIGHS

 

 

GRAPH 3

RESULTS AFB INTERPRETAIONS OF THE STLJY

The graphic illustrations of the counts on the diff-

erent variants of Ponderodictya show that their individual

 

peak developments did not maintain within the same short
straigraphic interval, but rather, there is indicated a
phylomorphogenetic succession through much of the Traverse
formation. Some of the types show considerable overlapp-
ing of their time periods or zones, which indicates trans-
itional periods in which the younger groups of variant
morphologic structures were gradually replacing the pre-
ceeding ancestral groups. (Graph 2.)

The thirteen.type specimens Were graphfid in descend-
ing order with respect of their hemerae, (Graph 2 and 5.)
but the writer is not able to account for the succession
of the various groups of taxonomic features, although an
ample amount of projection has been done by students of
paleozoology to explain such occurrences.

For example; the posterior structures vary in number
as well as expression from spinose to monticular; the
flanges vary in degree of develOpment, even being replaced
by a shoulder or lack of either feature at the anterior
or antiplenate end. Similar discussion is applicable to
the other features as the overlap, muscle scar, reticula-

tion, pitting, and general outline of the carapace. These

morphologic structures are variations within the genus, so

 

C1]
C23

that we may expect the types to be generally similar. A
greater variation of these features or subsequent replace-
ment by some other features would cross the generic boundary.
From an examination of the zones on graph I, the reader may
see the longQDntemporaneous life spans of various types.
Specimens 7 and 10 exhibit much overlap of life span. They
have some common.morphologic features, so that one may be
more closely related to the other than either is with a more
dissimilar form such as number 15. It is evident from
graph 5 that the peak development of 7 is forty feet strat-
igraphically higher or later than that of 10. These two
types may be very close variants of a common ancestral form.
Further investigation of the formations stratigraphically
lower than the Traverse group may disclose variants of

Ponderodictya that are similar and ancestral to these.

 

Such studies need not be confined to the Michigan Basin
alone; for in.harmony with the bioseries concept, the
development of the phylomorphogenetic series was similar
over the entire world within the same geologic time inter-
val even though breaks in sedimentation took place at diff-
erent times in.different basins of deposition.

Another point necessary for clarification is that the
stratigraphic points of peak deve10pment or hemerae do not
express the same stratigraphic terminal points that limit
the life span or stratigraphic range of each type specimen;

therefore, the biozones made evident on their reSpective

0-]

graphs (1 and E) are different with respect to the number

of zones and their vertical distribution. The zones shown
on graph 5 are not proposed to be the same zones or even

a similar expression of the zones shown on graph I. Since
the hemeral peaks or major and minor highs on graph 3 are
the points of highest frequencies of the individual var-
iant types, then the peak point of each type must fall with-
in the stratigraphic range of that respective type on

graph I.

From the nature of the two kinds of zones as shown on
graphs 1 and 3, it appears faster and easier to locate and
define a zone stratigraphically accurate by the high fre-
quency points (hemerae) than.by the conventional life span
or stratigraphic range of a type. It would be necessary
to check several of the type variants by the old method
of graph I in order to find the various assemblages of
those types that define any one zone of graph I. On the
other hand, if a student were reasonably sure he had
located two hemeral or major points as those of types 10
and 12 (graph 3), then he will have limited the horizon to
approximately ten geet. The top of this horizon is 510 feet
stratigraphically below the base of the Antrim shale or its
equivalent. (See graph 5, major zone D.)

The frequency-biozones (graph 5) are further preferred
to those of the conventional zones based on the stratigraphic

range of individuals (graph I) because the missing of one

OJ
'1

or more type specimens for some footage interval will
rasult in an erroneous faunal assemblage. Even some of
the zones shown on graph I may be in error because of this.
Where small footage (5—20 feet) intervals are missing from
the well samples, the range of the type specimen may not
be determined correctly to its true upper or lower extent
if the missing interval is at such a critical stratigraphic
position. It is true that where such an interval is miss;
ing, the frequency or statistical methods will have no
specimens either, but if the student has sufficient well
samples to locate the high points or hemerae, then he has
the biozones (graph 5) located stratigraphically in spite
of the missing intervals. It may be argued that the use
of samples from several wells would increase the accuracy
of determining the zones of graph I. This may be very
true; but that same number of wells will locate the hem—
erae much better, so that the zones of graph 3 become more
accurate than those of graph I. by so doing. I

Since the study was made from well samples in a rel-
ative y sahll area (See map.) it was possible to obviate
the possible arguments of environmental differences and
extreme variations of thickness of the Traverse iormation.
The absence of specimens for different intevals as evi-
denced by graph I is not due to contemporareous environ-
mental differences within the area, but this absence is

often due to a break in.well samples for several feet.

 

56

It is also caused by poor sampling; for example, several of
the wells examined were not used in the cunt because entire
trays of 25 bottles each, may have had little besides the
drilling muds, which was1 d away readily to reveal a pau—
city of rock fragments and fossils.

The variation in thickness of the formation over
some thirty miles approximates stty to seventy feet, the
slightly thicker portion is toward the basin itself.
Accordingly, if any area with a thicker or thinner section
is studied for comparison, then its hemerae points and
their respective biozones must be compared on a strati-
graphically proportional basis with the zones outlined in

this study. (Graph 3)

01
K]

CONCLUSIONS

On the basis of the hemerae of the respective variant

types of Ponderodictya there is a definite zoning in the

 

lower three fourths of the Traverse formation. This zon—
ing or subdividing of a formational group is not only pos-
sible with the frequency method, but such zones are also
more accurately located stratigraphically than the zones
defined by he conventional method of vertiCal ranges of

species.

B BLIOGRAPEY

Glaessner, M.F., Principles of hicropaleontology, Mel-

 

bourne University Press, Melbourne, Australia, 1945.

Jeletzky, J.A., "Some hbmenclatoria and Taxonomic Problems

in Paleozoology," Journal of Paleontology,Vol. 24,

 

to. l, 1950.

Kelly, W.A., Personal Communication.

Shimer, H.W., and Shrock, R.R., Index Fossils of Perth

 

America, J.¥iley a S ons, Inc., New York, 1947.

1

Swartz, F.H., and Oriel, S.S., Journal of Paleontology,

Vol. 22, Nb. 5, 1948.

Tan Sin Hok, "The Results of Phylomorphogenenc Studies of

Some Larger Foraminifera," De Hg. in Ned. Indie., 6,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   
   

 

 

   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I TYPE SPECIMENS g ZONE
I384I 5526 I3922 5926 I3028 5068 IIOOI 5204 4294 467i CANADA I2 |4072 ; I3702 6584 4720 6I99 7860 CANADA SOCANADAIS M733 I4358 g 3 4 5 g 7 8 9 IO II I3; I3
DISTRIBUTION CHART OF THE I3 TYPES OF I ._ I a . . I —— — ~— _ - 4— —.. ~— -— _- “—-
' ; I g f I I9
i I I I can: - _..___..,_.___—m~_— .
Izo I... . . I ; I I... I
PONDERODICTYA IN THE TRAVERSE FORMATION ; b p I t i ‘8
I, I U B i I I I n . I D
' I i g I I I] ____-______,_.___~.____.____
IN THE ST. CLAIR COUNTY AREA I z i I /
I40 Cw--. LPQEIYR m ‘ I w 5 L I ' ' "‘ "“‘ “' "“ “ “‘ " ““"‘ “'
TYPE" SF“EC‘.IMEI\IS FRI-:UUI.I'I I I I I ; I
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‘ TOP OF DUNDEE

 

 

 

 

 

 

GRAPH I

 

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