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thesis entitled

CONODONT COLOR ALTERATION, ORGANIC METAMORPHISM,
AND THERMAL HISTORY OF THE "TRENTON FORMATION,"
MICHIGAN BASIN

presented by

Craig G. Hogarth

has been accepted towards fulfillment
of the requirements for

Jasleris_degree in 5301.091—

 

Date June 20', 1985

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CONODONT COLOR ALTERATION. ORGANIC METAMORPHISM
AND THERMAL HISTORY OF THE "TRENTON FORMATION,”
MICHIGAN BASIN

By

Craig G. Hogarth

AN ABSTRACT OF A THESIS

Submitted to
Michigan State University
in partial Fulfillment of the requirements
For the degree oF

MASTER OF SCIENCE

Department of Geological Sciences

1985

ABSTRACT
CONODONT COLOR ALTERATION. ORGANIC METAMORPHISM.

AND THERMAL HISTORY OF THE "TRENTON FORMATION."
MICHIGAN BASIN

By

Craig G. Hogarth

The paleogeothermal gradient in the Michigan Basin has
been Found to closely resemble present day gradients. This
conclusion is based on analysis of thermal maturation oF
conodonts in the "Trenton Formation" (Middle Ordovician),
Michigan Basin.

In the northern and central portions of Michigan, a
paleogeothermal gradient of 23 °C/km. best fits the
maturity of the conodonts. In the southern portion of the
basin, the observed maturity of the conodonts could not be
accounted For with a geothermal gradient of 23 OC/km.
Additional subsidence. between 600 and 700 meters. or an
average geothermal gradient of 31 oC/km. had to exist to
account For the maturity in southern Michigan.

From constraints provided by geothermal gradients. the
‘oil generative window’ was constructed For the burial
history curves in the Michigan Basin. In the Central
Michigan Burial History Curve. oil generation is presently
beginning in the Lower Devonian section. In the Northern
Michigan Burial History Curve. oil generation is beginning
in the upper portion oF the Upper Silurian section. In the
Southern Michigan Burial History Curve, only rocks of
Ordovician age and older are capable of hydrocarbon

generation.

DEDICATION

In Memory of, Patricia Ellen Friedly Hogarth

ii.

ACKNOWLEDGMENTS

I would like to extend my gratitude and appreciation to
those who have assisted in the completion of this thesis.
Special thanks go to Dr. Duncan F. Sibley for suggestion of
this topic and expert guidance through its duration.

Thanks are also extended to the members of the thesis
committee. Dr. Robert L. Anstey and Dr. William F.
Cambray. Financial assistance for completion of this
thesis provided by Amoco Production Company. Samples used
in this study were provided by Maria Balzarini, Shell
Western Exploration and Production Inc.: Dr. Joyce Budai.
The University of Michigan Subsurface Laboratory: Dr.
Gordon Wood, Amoco Production Company: Dr. Robert Votaw,
Indiana University at Gary; and Michigan State University.
Appreciation goes to Dr. Carl Rexroad, Indiana Geological
Survey. for providing instruction in sample preparation,
and Dr. Anita G. Harris, United States Geological Survey,
for providing Color Alteration Index standards. Joseph
Straccia, Shell Western Exploration and Production lnc.,
offered helpful suggestions throughout this investigation.
Special thanks go to my family for providing support and

encouragement during my tenure at Michigan State

iii.

University. Finally, I would like to extend my heartfelt
appreciation to Linda for her love, dedication. and

patience.

iv.

TABLE OF CONTENTS

LIST OF TABLES ................................. . vii.
LIST OF FIGURES ................................ . viii.
INTRODUCTION ................................... . 1

DESCRIPTION OF THE MICHIGAN BASIN

AND "TRENTON FORMATION" ........................ . 2

THERMAL HISTORY OF THE MICHIGAN BASIN .......... , 3

LOPATIN’S METHOD OR THE TIME

TEMPERATURE INDEX .............................. . 7
BURIAL HISTORY CURVES .......................... . l4
ORGANIC METAMORPHISM AND CONODONTS ............. . l7
COLOR ALTERATION INDEX: DATA ................... . 25
Sample Preparation and Indexing ................ . 25
Data ........................................... . 29

TABLE OF CONTENTS (continued)

PALEOGEOTHERMAL GRADIENT RECONSTRUCTION ........ .

GENERATION OF OIL AND GAS IN THE

MICHIGAN BASIN. ................................ .
DISCUSSION OF HYDROCARBON GENERATION.... ....... .
CONCLUSION ......................... . ........... .

APPENDIX A.
Core Sampled for Conodonts in the

”Trenton Formation" ............................ .

APPENDIX B.

Burial History Curves Constructed in the

Michigan Basin ................................. ,

REFERENCES CITED ............................... .

vi.

29

40

46

50

52

54

58

LIST OF TABLES

Table 1.

Temperature Factors for Different Temperature
Intervals ...................................... .
Table 2.

Calculation of Cumulative TTI for Example

Burial History Curve ........................... .
Table 3.

Correlation of TTI with Stages of Oil

Generation and Preservation ....... . ............ .
Table 4.

Calculation of the Cumulative TTI in the
"Trenton Formation” Using a Paleogeothermal
Gradient of 35 °C/km. and a Linear Decrease

to 3 Present Day Gradient of 22 °C/km. from

the Permian to the Present ..................... .
Table 5.

Calculation of Cumulative TTI in the "Trenton
Formation" Using a Geothermal Gradient of 23

oC/kmooooooooooooooooo ooooooo o. ................ 9

vii.

LIST OF FIGURES

Figure l.

Burial History Curve for Example Calculation of
the Time Temperature Index ..................... .
Figure 2.

Location of Burial History Curves Constructed

in the Michigan Basin.

(From Cercone. 1984) ........................... .
Figure 3.

Color Alteration Indices. Paleotemperatures.

and Percent Fixed Carbon.

(From Epstein. et al.. 1977) ................... .
Figure 4.

Ahrennius Plot of Heat Induced. Open—Air.
Conodont Color Alteration Data.

(From Epstein. et al.. 1977) ................... .
Figure 5.

Scales of Organic Metamorphism.

(LOM. TAI. and R0: From Hood. Gutjahr and
Heacock. 1975)

(TTI: From Waples. I980)

(CAI represent maximum estimated R0: From
Epstein. et al.. 1977).. ...................... .

viii.

16

20

23

27

LIST OF FIGURES (Continued)

Figure 6.

CAI Isograd Map Superimposed on Structure
Contour of the Top of the "Trenton Group"
(Structure Map: From Hinze and Merritt. 1969)...
Figure 7.

Central Michigan Burial History Curve 1.000
Meters Cumulative Overburden

(Burial Curve: From Cercone. I984) ......... .....
Figure 8.

Northern Michigan Burial History Curve 1.000
Meters Cumulative Overburden

(Burial Curve: From Cercone. 1984) ............. .
Figure 9.

Southern Michigan Burial History Curve 1.000
Meters Cumulative Overburden

(Burial Curve: From Cercone. I984) ............. .

ix.

31

43

45

48

INTRODUCTION

The Michigan Basin is a stable. Paleozoic intracratonic
basin which underwent subsidence from the Ordovician
through the Pennsylvanian. Recently. two models for the
thermal history of the basin have been proposed. Large
discrepancies exist between the geophysical model of the
basin (Nunn. Sleep. and Moore. 1984). and a model using the
Time Temperature Index (TTI) of organic maturation
(Cercone. 1984). The geophysical model proposes that
geothermal gradients during the Paleozoic varied little
from the average present day geothermal gradient of 22
oC/km. The Time Temperature Index model for the thermal
history of the Michigan Basin proposes higher
paleogeothermal gradients. between 35 °C/km. and 45
oC/km. for the Paleozoic section with a subsequent
decrease in the geothermal gradient to present day values.

This study is concerned with the thermal history of the
"Trenton Formation" (Middle Ordovician). Michigan Basin
using conodonts as indicators of organic metamorphism.
Conodonts are microfossils. which have been used as
indicators of organic metamorphism in Paleozoic rocks. to
estimate past thermal history and degree of organic

maturity (Epstein. et al.. 1977). (Harris. 1979)

2
(Legall, et al.. 1981). and (Wardlaw and Harris. 1984).
Conodonts were used in this study as indicators of organic
metamorphism because. 1) they are present in the early
Paleozoic rocks. unlike vitrinite: 2) they are common in
carbonate rocks. unlike palynomorphs; and 3) they are
stable under a wide range of thermal conditions. unlike
palynomorphs. Using conodonts as indicators of organic
metamorphism. estimates of a geothermal gradient in the
Paleozoic were made. From the estimates of paleogeothermal
gradients. inferences concerning the generation and
preservation of oil and gas can be attempted for the
Michigan Basin.
DESCRIPTION OF THE MICHIGANggASIN ANQTFTBENTON FORMATION"

The Michigan Basin is composed of a sequence of
predominantly marine. Paleozoic sediments which dip gently
toward a depocenter in the north-central portion of the
lower penninsula of Michigan. The sediments of the
Michigan Basin are carbonates (47 1). clastics (41 1). and
evaporites (12 z) (Ells. I969).

The Michigan Basin is encircled by the Canadian Shield
to the north. the Algonquin Arch to the east. the Findlay
and Kankakee Arches to the south. and the Wisconsin Arch to
the west (Ells. 1969). For the most part. the basin has
had a relatively simple structural history with little
evidence for post-subsidence structural deformation (Nunn.

Sleep. and Moore. 1984).

3

The "Trenton Formation" is one of the first formations
in the Michigan Basin to exhibit the present basin like
geometry. It is a sequence of fossiliferous limestone with
dolomite present in some portions of the basin. Near the
base. and in the northern sectors of the basin. the
"Trenton Formation" gradually becomes shalier. Thicknesses
of the "Trenton Formation." in the southern penninsula of
Michigan. range from 61 meters to 145 meters. From
exposures in the Upper Penninsula. to the deepest portion
in central. lower Michigan. there is about 3350 meters of
relief on the top of the "Trenton Formation." Overlying
the "Trenton Formation” in the southern penninsula. are
sediment thicknesses ranging between 380 and 3000 meters
(Lillienthal. 1978). Because the "Trenton Formation" is
one of the earliest formations to exhibit the present basin
geometry. it is ideal for examining the Paleozoic thermal
history of the Michigan Basin with conodonts.

IEERMAE HISTORY 95 THE MICHIGAN BASIN

A preliminary study of the observed thermal maturity in
the Michigan Basin was completed by Moyer (1982) using
amorphous kerogen from selected formations. Moyer (1982)
assumed that amorphous kerogen and terrestial spores
undergo similar color changes as they mature. The
coloration of organic matter was graded on the basis of a
spore/pollen color chart. On the basis of one Saginaw
Formation coal sample at Grand Ledge. Michigan (mean

maximum reflectance R0: .5411) and the amorphous kerogen

4
coloration data. Moyer (1982) estimated that between 1.2
and 2.1 kilometers of overburden existed in the Michigan
Basin. Moyer (1982) based the overburden estimate on a
paleogeothermal gradient estimate of 46 oC/km. and a mean
annual temperature of 8 oC. The paleogeothermal gradient
was inferred from a least squares analysis of regression
for amorphous kerogen coloration in the McClure Sparks
well.

Cercone (1984). in order to infer the thermal history
of the basin. utilized Moyer's (1982) data and constructed
burial history curves. from stratigraphic data. for
selected portions of the Michigan Basin. Using several
lines of evidence. Cercone (1984) estimated that 1.000
meters of overburden had been eroded from the Michigan
Basin between the Permian and the Jurassic. Her lines of
evidence include:

1. The presence of immature Jurassic sediments
unconformably lying on mature Pennsylvanian
sediments.

2. Extrapolation of an early Paleozoic subsidence rate
through the Carboniferous. posits 1.000 meters of
additional subsidence.

3. The presence of 1.700 meters of Carboniferous
sediment present in the Illinois Basin minus the
700 meters of Carboniferous sediment present in

the Michigan Basin is about 1.000 meters.

5
4. Extrapolation of the regional dip in the Upper
Mississippian Bayport Limestone to the northern
hinge line of the basin reveals an estimate of
about 1.000 meters of sediment eroded from the
Michigan Basin (Cercone. 1984).
From these lines of evidence. and stratigraphic
information. Cercone (1984) was able to construct burial
history curves and apply Lopatin's method to estimate
paleogeothermal gradients in the basin (Lopatin. I971;
Waples. 1980).

From the Time Temperature Index calculations and the
maturity data from Moyer (1982). Cercone (1984) estimated
that paleogeothermal gradients between 35 °C/km and 45
°C/km existed for the Paleozoic. Cercone (1984)
postulates that a linear decrease in the geothermal
gradient took place from the Permian to the present in
order to account for present day geothermal gradients of
around 22 oC/km. Moyer (1982) and Cercone (1984) have
proposed higher geothermal gradients in the past. based on
suspect organic maturity data. yet geophysical models of
the basin propose paleogeothermal gradients which are the
same as present day values.

Nunn (1981) and Nunn. Sleep. and Moore (1984) developed
a 3-dimensional model for the isostatic subsidence of the
Michigan Basin with subsidence beginning at the base of the
Middle Ordovician (462 M.Y. b.p.). Excess temperatures due

to uplift and subsequent thermal contraction of the

6
lithosphere could produce an excess temperature anomaly of
only 15 °C in the center of the basin for the Middle
Ordovician rocks and degrade to 0 0C by the
Pennsylvanian. Nunn. Sleep. and Moore (1984) conclude that
the excess temperatures produced by a thermal event in the
lithosphere would be insignificant compared to the
deposition of overlying sediments and a corresponding
increase in temperature due to burial. Based on the
geophysical model. Nunn. Sleep. and Moore (1984) estimated
that paleogeothermal gradients in the basin were similar to
present day geothermal gradients of 22 oC/km.

The geophysical model rejects the model of higher
geothermal gradients in the basin on two points. First. in
order to account for paleogeothermal gradients of an
additional 20 oC/km.. heat flow would have to increase by
an additional HFU. In order to perpetuate the additional
heat flow during the Paleozoic history of the basin. an
intrusion the size of a batholith must be present to
account for geothermal gradients on the order of 42
°C/km. (Nunn. Sleep. and Moore. 1984). Secondly. if one
was to assume. for a period from the Devonian through the
Carboniferous. a gradient 20 °C/km. higher than the
present day geothermal gradient. and apply the uniform
extension model for total oceanization of continental
lithosphere (McKenzie. 1978). then subsidence would be on
the order of 10 kilometers for the Michigan Basin (Nunn.

Sleep. and Moore. 1984). Obviously. these are strong

7
arguments against higher paleogeothermal gradients in the

Michigan Basin.

LOPATIN’S METHOD QB THE TIME TEMPERATURE INDEX

The Time Temperature Index is used to model the thermal
conditions necessary for organic maturation (Lopatin. 1971;
Waples. 1980). The model is based on the burial history of
sediments through time. the thermal conditions encountered
during burial. and the kinetics of organic maturation.
Burial history can be constructed from knowledge of the
geologic history and stratigraphic information available
for the intervals of interest. The thermal conditions can
be based on knowledge of present geothermal gradients in
the area of interest. Paleogeothermal gradients can be
estimated from the Time Temperature Index model using
available organic maturity data within the area of interest
and applying various geothermal gradients to best fit the
burial history and observed organic maturity. In the
model. the kinetics of organic maturation are based on the
‘pseudo first-order reaction rate' which states that
reaction rates in organic maturation will double with every
10 °C rise in temperature. Once the burial history. the
geothermal gradient or observed maturity. and the kinetics
of organic maturity are known then the Time Temperature
Index can be calculated.

The Time Temperature Index (TTI) is a Simple
calculation used to infer the thermal conditions necessary

for organic maturation. Figure I. is a sample burial

Figure I. Burial History Curve for Example Calculation
of the Time Temperature Index.

SE:
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Figure l.

IO
histbry curve used for a simple calculation of the Time
Temperature Index. The ea%3tion to calculate the Time
Temperature Index is TTI=2 (ATn) (r0). ATn is the
time in mega-annums whichwgnsediment interface resides in a
particular temperature interval. In the example the r
value is equal to 2. or with every 10 oC increase in
temperature the rate of reaction doubles. The superscript
n. or the index value. is an arbitrary value which has been
designated 0 for the temperature interval between 100 - 110
°C. Table 1. lists n values assigned to various
temperature intervals. In the example. the geothermal
gradient is 30 °C/km. and the mean annual temperature is
20 °C. From the geothermal gradient. the burial history
curve. and the temperature factor the TTI can be
calculated. For the example. a cumulative TTI of 87.5 was
calculated (Table 2.).

Waples. (1980) has correlated the Time Temperature
Index with various indicators of organic maturation. which
are time and temperature dependent. such as vitrinite
reflectance. the Thermal Alteration Index (TAI). and other
organic indicators which define the ‘oil generative window'
and degrees of oil and gas preservation (Table 3.).

Because vitrinite is correlative with the Color Alteration
Index (CAI). the Time Temperature Index (TTI) can be
applied and oil and gas generation can be estimated using
conodonts as indicators of organic metamorphism. With

Color Alteration Indices from the Trenton Formation and the

11

Table 1. Temperature Factors for Different

Temperature Intervals

 

 

Temperature Interval 9Q lgggx gngg Temperature Factor
30 - 40 —7 r-7
40 - so -6 r-6
so - 60 -5 r-5
so - 70 -4 r-4
70 - so -3 r-3
so - 9o —2 r-2
90 - 100 -l r-1
100 - 110 o r0
110 - 120 I r1
120 - 130 2 r2
130 - 140 3 r3
140 - 150 4 r4

.00.,

(After Waples. 1980)

12

Table 2. Calculation of Cumulative TTI for

Example Burial History Curve

 

 

 

1192 Duration (Ma) Temggrature Factor Interval TTI

I so 2'8 .195
2 25 2-7 .195
3 25 2'6 . .390
4 25 2‘5 .781
5 25 2-4 1.562
6 25 2-3 3.125
7 25 2"2 5.25
a 50 2-1 25.0

9 50 20 ___§g;g

Cumulative TTI 87.5

Table 3.

Onset of Oil

Generation and

Generation .....

Peak of Oil Generation. .....

End of Oil Generation. ......

Upper TTI Limit for

Occurrence of Wet Gas. ......

(From Waples.

1980)

I3

15
75

160

~1500

Preservation

Correlation of TTI with Stages of Oil

11)”

.65

1.00

14
Time Temperature Index (TTI) calculations. estimates of
paleogeothermal gradients can be applied to estimate the
thermal conditions necessary for the generation and
preservation of oil and gas in the Michigan Basin.
EURIAL HISTORY CURVES

Analysis of the thermal history and evolution of
hydrocarbons in the Michigan Basin necessitates the use of
burial history curves. Burial history curves are
reconstructions of various sediment units through time.
The curves can be constructed to record subsidence. uplift.
or other geologic conditions. The accuracy of the thermal
history is dependent on the accuracy of the burial history
curves (Waples. I980). Cercone (1984) constructed three
burial history curves in different sections of the Michigan
Basin (Figure 2.). The curves are based on geologic
evidence of subsidence. prexisting overburden in the basin.
and stratigraphic data. Continuous subsidence of the
Michigan Basin was inferred through the Carboniferous. and
erosion events during the Paleozoic were combined into one
major event beginning in the Permian. These assumptions
were used to simplify the burial history models. The
removal of 1.000 meters of preexisting overburden was also
incorporated into the burial history curves (Cercone.
I984).

The curves represent three areas of oil production in
the basin. The Central Michigan Burial History Curve is

located in the central portion of the basin in the

15

Figure 2. Location of Burial History Curves
Constructed in the Michigan Basin
(From Cercone. I984)

16

LOCATION OF BURIAL HISTORY CURVES

   

Michigan \
Bwun

 

 

 

(CERCONE, 1 984)

Figure 2.

 

I7
Mississippian/ Devonian production areas of the basin. The
Northern Burial History Curve represents the northern reef
trend of the basin. The Southern Burial History Curve
represents burial history in the Ordovician production
zones of the Michigan Basin (Cercone. 1984). Finally.
burial history curves were constructed in areas where
changes in CA1 are located. Burial history curves were
used in the Lopatin modelling so paleogeothermal gradients
could be estimated and compared with the observed maturity.
ORGANIC EEIAMORPHISM AND CONODONTS

Conodonts are a microfossil of debated biological
affinity which were ubiquitous in Cambrian through Triassic
seas. Numerous authors postulate that most conodonts were
pelagic organisms. however. this interpretation is based
solely on their global distribution and bilateral symmetry
(Clark. 1981: Bergstrom. 1973: and Seddon and Sweet.

1971). Traditionally. conodonts have been used as
biostratigraphic tools. Recently. interest has been
focused on their use as indicators of organic metamorphism
in Paleozoic rocks.

Diagenesis and catagenesis have long been studied in
various types of organic matter. Temperature and time have
been emphasized as the primary variables controlling the
diagenetic and catagenetic processes occuring in organic
matter (Teichmuller and Teichmuller. 1966; Lopatin and
Bostick. 1973; Hood. GutJahr. and Heacock. 1975). Conodont

skeletons contain a small amount of organic matter. which

l8
accounts for their coloration. Upon heating. the organic
matter present is progressively fixed within the conodont
element. With progressive carbon fixation. darkening of
the conodont element takes place. Maturation of conodonts.
in the geologic environment. is considered to be additive
and irreversible (Epstein. et al.. 1977).

From experimental evidence. Epstein. et al.. (1977)
constructed the Color Alteration Index (CAI) to estimate
the maturity of the conodonts. and then calculated an
Ahrrenius plot to estimate the approximate paleo-
temperatures conodonts have undergone during their burial
history. Unaltered conodonts. from the Kope Formation
(Upper Ordovician). were subjected to temperature ranges
between 300 0C to 600 0C for 1 to 1000 hours in order
to model the color changes observed in field collections of
conodonts. In the presence of heat. conodonts gradually
undergo color changes from amber at low temperatures tO
black at high temperatures. The color changes observed in
the experiments were the same as the colors observed in the
field collections. From the observed color changes.
Epstein. et al.. (1977) developed the Color Alteration
Index (CAI). The Color Alteration Index is a numerical
scale from 1 to 5 and is based on the color Observed in the
conodonts under reflected light (Figure 3.).

Based on the experimental evidence provided by the
conodonts in open-air heating runs. Epstein. et al.. (1977)

extrapolated an Ahrrenius plot using the ‘pseudo first

19

Figure 3. Color Alteration Indices. Paleotemperatures.
and Percent Fixed Carbon.
(From Epstein. et al.. 1977)

20

 

Figure 3.

21
order reaction rate’ to geologic time and reasonable
thermal conditions. From the Ahrrenius plot. estimates of
paleotemperature can be made based on the Observed Color
Alteration Index (CAI) of the conodonts (Figure 4.).

In addition to developing the Color Alteration Index
for conodonts. Epstein. et al.. (1977) experimentally
matured conodonts. under a variety of conditions. in order
to determine whether the coloration process was contingent
on variables other than the duration and magnitude of
heating. Under high pressure (1 kbar). using inert Argon
and reducing methane as media. the conodonts showed no
variation in color from those heated at 1 atmosphere in
open-air runs. Also. the effects of pressure have been
addressed extensively in the coalification process.
Lopatin and Bostick (1973). provide laboratory evidence
showing that pressure has little or no effect on the
increase in vitrinite reflectance during experimental
heating at high temperatures and varying pressures. Field
evidence from coal seams and conodonts demonstrates that
pressure has little or no effect in the maturation of
organic matter (Teichmuller and Teichmuller. 1966; Epstein.
1977).

Although pressure has no effect on the coloration
process in conodonts. water pressure does affect the
coloration of conodonts. Under high pressure (1 kbar). in
a closed system. and in the presence of water the

maturation of the conodonts is retarded. The presence of

22

Figure 4. Ahrennius Plot of Heat Induced. Open-Air.
Conodont Color Alteration Data.
(From Epstein. et al.. 1977)

23

o. z. omimeiomm mmaimmasm... 538300300563

SHflOH NI ‘SWIJ.

833 one can on“ 3... 2: 03 on

0—.
cow
0009

 

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wPZODOZOU no m02<m

SBVSA NI ‘BWIJ.

Figure 4.

24
water in an open system has no effect on the coloration of
conodonts. However. as a result of color retardation in a
closed system. paleotemperature estimates from the
Arrhenius plot could be underestimated. Epstein. et al..
(1977) point out that these conditons may be present in
overpressured rocks. Overpressured rocks. in the Michigan
Basin. were not present due to low rates of sedimentation
(Bethke. I985). therefore paleotemperature estimates. from
the Ahrrenius plot are probably correct. Based on the
experimental and field evidence. conodonts appear to be
good indicators of organic maturity and paleotemperature in
carbonate rocks.

The Color Alteration Index (CAI) has been correlated
with other scales of organic maturation in sediments.
Epstein. et al.. (1977). found a good correlation between
vitrinite reflectance and the CA1 observed in Devonian
conodonts found in the Appalachian Basin. The range in
vitrinite reflectance and CAI is less than 0.8 1Ro for a
CAI of 1 to more than 3.6 1R0 for a CAI of 5. Color
Alteration Indices (CAI) have also been correlated with
percent fixed carbon. The fixed carbon percentages range
from less than 601 to more than 951. Other scales of
organic maturity can be correlated with the Color
Alteration Index based on the correlation with vitrinite
reflectance. Some scales which can be correlated with the
Color Alteration Index are the Level of Organic

Metamorphism (Hood. Gutjahr. and Heacock. 1975). the

25

Thermal Alteration Index (TAI) (Staplin. 1969). and the
Time Temperature Index (TTI) (Lopatin. I971; Waples. 1980)
(Figure 5.). All of the preceding are measures of organic
maturation which can be correlated with the Time
Temperature Index (TTI).

99593 AETERATION INDEX: DATA
Sample Preparation gag Indexing:

Between 100 and 500 grams of limestone or dolomite was
crushed in a coarse crusher. The Size of the largest
crushed chips was about 1/2 inch. The chips were then
place in plastic buckets. and 10 percent acetic acid was
added. The buckets were covered and placed under fume
hoods for several days. until the carbonate matrix was
dissolved. Once the matrix was dissolved. the remaining
sediment was wet sieved to remove the coarse fragments and
the fine particles from the conodont fraction. A 25 mesh
sieve on top of 150 to 200 mesh sieves removed the
remaining coarse fraction. The 150 to 200 mesh sieves
caught the sediment fraction containing the conodonts. The
sediment Fraction containing the condonts was wet sieved to
remove remaining fine particles. The fraction of the
sediment containing the conodonts was allowed to dry
overnight.

Once the remaining sediment is dry. conodonts can be
further concentrated using heavy liquid separation.
1.1.2.2. Tetrabromoethane was used to complete the heavy

liquid separation. Care must be taken when using heavy

26

Figure 5. Scales of Organic Metamorphism.

(LOM. TAI. and Ro: From Hood. Gutjahr. and
Heacock. 1975)

(TTI: From Waples. 1980)

(CAI represent maximum estimated R0:
From Epstein. et al.. 1977)

27

 

 

 

.. R
O
2—
4—
6—1
"—o.5
8--
Io-"'
-:- 1.0
12—5— 1.5
'—2.o
14--
-L
15-4.".."2'5

THERMAL
ALTERATION
INDEX

1" NONE
(YELLOW)

Z-SLIGHT

(BROWN -
YELLOW)

-3-MODERATE
_3.5(BR0WN1

—3.7

—t4-STRONG
(BLACK)

 

COLOR

ALTERATION
INDEX

""'I5

-—2

 

TIME

‘ TEMPERATURE

INDEX

—I60

—1500

 

 

Figure 5.

 

28
liquids for they are carcinogenic (Hauff and Airey.
1978). A strong fume hood. a respirator. and Norton Viton
gloves were used to handle the heavy liquid separation.
The sediment containing the conodonts was placed in the
1.1.2.2. Tetrabromoethane and stirred. The slurry was then
allowed to sit overnight with occasional stirring. Once
the separation was complete the heavy portion is separated
by filtering. The 1.1.2.2. Tetrabromoethane was filtered
through and saved for future use. The heavy fraction was
washed a few times. to remove the remaining heavy liquid.
with methanol or acetone and allowed to dry. Once the
sediment was dry. the conodonts were handpicked with a
trimmed 00000 camel’s hair brush. Conodonts were mounted
on standard micropaleontologic slides and glued on with gum
arabic.

Once the conodonts have been recovered. the Color
Alteration Indices can be determined. From each.core a
number of individual samples were selected for indexing.
Specimens were placed on a clean. white porcelain plate
under reflected light. Using a CAI standard of Ordovician
conodonts provided by Dr. Anita G. Harris. each sample was
indexed by visual comparison with the standards and
assigned a CAI. After initial indexing. representative
samples from every core were tested to determine whether

the assigned CAI value was consistent and reproducible.

29
0.9.22:

Color Alteration Indices were determined for conodonts
in 24 "Trenton" core locations. one Upper Penninsula
surface exposure. and from data published on the
Brazos-State Foster core in Ogemaw county (Repetski and
Harris. 1981) (See Appendix A. for wells and exact
locations). Color Alteration Indices. in the "Trenton
Formation." range from 1.0 in the surface exposures of the
Upper Penninsula and shallowly buried rocks in Southern
Michigan. to 2.5 (at 3.02 km.) in the deepest central
portion of the basin. At 3.84 km. the CA1 is 3.0 in the
Brazos State-Foster core (Repetski and Harris. 1981). From
the CA1 data collected in the "Trenton Formation." a CAI
isograd map was constructed for the Southern Penninsula of
Michigan. The isograd map is superimposed on a structure
contour of the top of the "Trenton Group" (Figure 6.). The
Ahrennius plot. constructed from experimental maturation of
conodonts. indicates that temperatures in the basin ranged
between 20 0C to 80 °C for a CAI of 1.0 and for a CAI
of 3.0 paleotemperatures ranged between 110 and 200 0C.
From the CA1 estimates and the burial history curves.
paleogeothermal gradients can be estimated for the Michigan
Basin using Lopatin's Method.

PALEOGEOTHERMAE GRAQIENT RECONSTRUCTION

Estimations of a paleogeothermal gradient in the
Paleozoic is necessary to understand the thermal history of

the Michigan Basin. The construction of a paleogeothermal

30

Figure 6. CAI Isograd Map Superimposed on Structure
Contour of the Top of the "Trenton Group"
(Structure Map: From Hinze and Merritt. 1969)

31

 

 

 

1.0 ‘

 

0.1. = 1000'

a

 

'3onuts

 

Figure 6.

 

32

gradient for the Ordovician rocks constrains geothermal
gradients through most of the sedimentary history of the
basin and provides constraints for the generation and
preservation of oil and gas in the basin. Because
conodonts provide an estimate of organic maturity in the
early Paleozoic rocks. geothermal gradients can be applied
to burial history curves in the Michigan Basin to estimate
a gradient which fits the observed conodont maturity. In
order to estimate paleogeothermal gradients. Lopatin’s
analysis was applied to the burial history curves. using a
variety of geothermal gradients. to calculate maturities.
A gradient was then picked which best fit the CA1 observed
in the conodonts.

Cercone (1984) has postulated geothermal gradients
between 35 oC/km. and 45 °C/km. for much of the
Paleozoic. with a subsequent linear decrease in the
geothermal gradient from the Permian to the present day
gradient of 22 °C/km. Using burial history curves
constructed for portions of the Michigan Basin. the
maturity of the Middle Ordovician section was calculated
using Lopatin’s analysis to determine whether the maturity
of the conodonts concurred with the maturity calculated for
a gradient of 35 °C/km. and a linear decrease to present
day gradients of 22 °C/km. In most burial history
curves. the maturity calculated by the published geothermal
gradient of 35 oC/km. overestimated the observed maturity

of the conodonts (Table 4.). For example. from an observed

Table 4.

Calculation of the Cumulative TTI

33

in the

"Trenton Formation" Using a paieogeothermal

Gradient of 35 °C/km and a Linear Decrease

to a Present Day Gradient of 22 oC/km.

from the Permian to the Present.

Present Burial

Southern
Michigan....
Southern
Michigan....
S./Middle
Michigan....
Northern
Michigan....
Central
Michigan....
Central

Michigan....

.882

1.42

1.86

3.84

km.

km.

km.

km.

km.

km.

CAI Value TTI Range

1.5 20-40

1.5-2.0 ~35-45

2.0 40*160
3.0 200-900

TTI CaIC.

21

68

202

442

2548

24.392

34
CAI of 2 at 2.96 km.. and a corresponding range in TTI of
40 to 160. the cumulative TTI calculated using a geothermal
gradient of 35 OC/km and a subsequent decrease to present
day values was 2.548. This corresponds to a CAI value of
4.0. From consistent overestimation of this magnitude. one
can conclude that lower geothermal gradients must have been
present in the Michigan Basin.

Since the observed maturity is overestimated by the
published paleogeothermal gradient from amorphous kerogen
coloration data. lower paleogeothermal gradients must have
been present in the Michigan Basin. For the Northern and
Central Michigan Burial History Curves a paleogeothermal
gradient of 23 °C/km. (M.A.T. 20 0C) was found to be
the best paleogeothermal gradient accounting for the
observed Color Alteration Indices (Table 5.).

Paleogeothermal gradients of 23 oC/km. are consistent
with the constraints provided by the geophysical model
(Nunn. Sleep. and Moore. 1984). Other evidence supporting
this gradient is paleomagnetic data. from the
McClure-Sparks well in the basin. which estimates a
maximum paleotemperature of 200 °C (van der Voo. and
Watts. 1976). The paleotemperature estimate of 200 0C
was measured at a depth of 5.3 kilometers. If 1.000 meters
of overburden is added to the 5.3 km.. and a paleo-
geothermal gradient of 35 oC/km is used to estimate
paleotemperature. then temperatures on the order of 240

°C would have been present in the basin. On the other

TabIe 5.

"Trenton

Gradient

Present Burial

Southern
Michigan.... .882
Southern
Michigan.... .97
Southern
Michigan.... 1.42
S./Middle
Michigan.... 1.86
Northern
Michigan.... 2.26
Central

Michigan.... 2.96
Central

Michigan.... 3.84

Km.

Km.

Km.

Km.

Km.

Km.

Km.

35

Calculation of Cumulative TTI

in the

Formation" Using a Geothermal

of 23 oC/km.

 

_Al Value 11; Raga:
1.0 1-30
1.5 20-40
1.5 20-40
2.0 40-160
2.0 40-160
2.0 40—160
3.0 200-900

TTI Calc.

18

37

63

184

785

36
hand. applying a gradient of 23 oC/km. temperatures on
the order of 165 OC would have been present during
maximum burial. Sustained temperatures of 165 OC would
be consistent with the paleomagnetic data and the Color
Alteration Indices in the northern and central portions of
the basin. however. the observed maturity in southern
portion of the basin can not be accounted for with a
paleogeothermal gradient of 23 °C/km.

With a geothermal gradient of 23 °C/km. and burial
history curves of the southern portion of the basin. the
observed maturity of the conodonts can not be explained.
The maturity observed in the conodonts is higher than the
calculated maturity. With CAI of 1.5 at 0.97 km.. the
calculated TTI from a gradient of 23 °C/km. would be
around 9. The minimum TTI for a CAI of 1.5 is 20. Also.
near the boundary where CA1 changes from 1.0 to 1.5. the
TTI calculated. using a gradient of 23°C/km.. is around
8. yet the predicted maturity should be around 15 to 20.
The discrepancy between the observed maturity and the 23
°C/km. gradient suggests that variables controlling the
thermal maturity of the southern portion of the Michigan
Basin were different from the northern and central sections
of the basin. A number of explanations exist to account
for the increased maturity of the southern portion of

Michigan.

37

One explanation for the maturity observed in the
southern portion of the basin could be to add additional
overburden to the basin while maintaining a gradient of 23
oC/km.. The amount of cumulative overburden required to
account for the observed maturity. from the Mississippian
to the Pennsylvanian. is on the order of 1.600 to 1.700
meters rather than 1.000 meters suggested by Cercone
(1984). Cercone (1984) has also observed heightened
maturity in the southern portion of the basin and
attributes it to error in the burial history curve
underestimating the amount of burial due to the erosion of
an unknown amount of pre-Devonian sediment during the Early
to Middle Devonian. However. with a gradient of 23
°C/km.. the amount of pre-Devonian sediment removed
during the Early to Middle Devonian ("IS-20 Ma) would have
to exceed 3.000 meters in order to account for the maturity
observed in the Ordovician rocks of the southern basin.
Sediment accumulation and erosion of this magnitude seems
unliker.

Another possible explanation for the higher Observed
maturity in the southern portion of the basin could be
regional variation in the conductivity of rocks from the
southern sector to other sectors of the basin. Generally.
carbonates and sandstones have higher conductivities than
shales. hence the geothermal gradient would be higher in
sections containing more shale units. Hitchon (1984)

points out that variation in conductivity is also related

38
to permeability. the type of cementation. and the magnitude
of compaction. as well as lithology. Pollack and Watts
(1976) addressed the variation in conductivity of rocks
from samples in the McClure Sparks well of the Michigan
Basin. Their findings indicate that geothermal gradients
in shale units of the Michigan Basin are around 25 °C/km.
slightly higher than the average gradient of 22 oC/km.
(Pollack and Watts. 1976). This variation is due to lower
conductivity of shale units. Accounting for higher
geothermal gradients in the southern portion of the basin
by changing the conductivity would be difficult. for the
conodonts were all selected from a carbonate matrix. Also.
the shale content of the "Trenton Formation" increases to
the north and the effects of decreased conductivity would
probably be expressed in the rocks of the northern section
of the basin (Lillienthal. 1978).

Although the addition of more cumulative overburden and
changing rock conductivities are possible explanations for
the increased maturity of the southern basin. the most
plausible explanation would be an increase in heat flow on
the southern flank of the basin. Based on the burial
history curves. average geothermal gradients of 31 oC/km.
had to exist in the southern portion of the basin to
account for the maturity observed in the conodonts. Two
possible models exist for increasing the heat flow in the
southern portion of the basin. The most obvious method to

increase heat flow in the sedimentary section would be to

39
increase the heat flow contribution from basement rocks.
Increased heat flow in the basement could be the result of
an increased amount of radioactive decay on the southern
edge of the basin. Another model accounting for higher heat
flow. hence higher geothermal gradients is gravity-driven.
ascending basin waters in the southern portion of the
basin.

The paleohydrology of the Michigan Basin has not been
studied. However. Bethke (1985) modelled the paleo-
hydrology of the Illinois basin and concluded gravity
driven groundwaters moved in a south to north direction
through the Illinois Basin. With gravity drive. heat flow
is increased significantly in the north due to warm
ascending fluids. Hitchon (1984) associates hydrocarbon
accumulations and variation in paleogeothermal gradients to
gravity-driven paleohydrologic conditions operating in the
Alberta Basin of Canada. Bethke (1985) points out that the
Michigan Basin could also be considered for the development
of a gravity drive model because it is tectonically similar
to the Illinois Basin. The fact that large bodies of
hydrothermal dolomites occur in the "Trenton Formation" in
the southern portion of the basin (e.g. Albion-Scipio and
Northville Fields (Taylor. 1982) is consistent with the
idea that basinal brines were ascending in this region. Of
course. much more work needs to be done in order to

determine the paleohydrology of the Michigan Basin.

40

The regional movement of warm fluids through time could
account for the maturity observed in the southern portion
of the Michigan Basin. however. determining the duration
and timing of such an event would be difficult. A
geothermal gradient of 31 oC/km. represents an average
geothermal gradient for the entire post-depositional
history of the Middle Ordovician section. Basin water
movement of this nature would not span the entire
post-depositional history of the Middle Ordovician
section. Obviously. geothermal gradients would have
fluctuated significantly during an event of this nature.
However. if one assumes a duration from the Devonian
through the Jurassic ("250 Ma) for the movement of basin
waters in this manner. and a geothermal gradient of 23
°C/km. for the remaining post-depostional history. the
geothermal gradient would only have to increase to 32
°C/km. in order to account for the observed maturity.

In summation. a paleogeothermal gradient of 23 °C/km.
is the best fit for the observed maturity in the northern
and central sections of the basin. but in the southern
portion of the basin additional overburden or an average
gradient of 31 oC/km had to exist to account for the
observed maturity of the conodonts.

Once thermal conditions are established for the
Michigan Basin. the generation and preservation potential

for hydrocarbons can be estimated. Based on the

41
constraints provided by the paleogeothermal gradient and
burial history curves constructed for the Michigan Basin.
the ‘oil generative window’ was constructed for each burial
history curve. In the Central Michigan Burial History
Curve (Figure 7.) the initial generation of oil (TTI=15)
began in the Lower Ordovician section during the
Mississippian and currently oil generation is beginning in
the Lower Devonian section at Just over 1 km. from the
surface. The Lower Devonian section probably began
generating oil about 200 million years ago. Oil generation
has been completed (TTI=I60) for all of the Lower and
Middle Ordovician sections and portions of the Upper
Ordovician section. Presently. the base of the oil
generative window is about 2.85 km. from the surface in the
Central Michigan Burial History Curve.

The Northern Michigan Burial History Curve represents
the Silurian production zones of the Michigan Basin. In
the Northern Michigan Burial History Curve. initial oil
generation began in the Lower Ordovician section during the
Mississippian and generation is presently occuring in the
uppermost section of the Upper Silurian. Oil generation is
completed for a small portion of the Lower Ordovician
section in the Northern Michigan Burial History Curve.
Presently. the boundary of the ‘oil generative window' is
from 1.30 to 2.75 kilometers below the surface (Figure 8.).
The ‘oil generative window’ for the Central and Northern

Michigan Burial History Curves was calculated using a

42

Figure 7. Central Michigan Burial History Curve
1.000 Meters Cumulative Overburden.
(Burial Curve: From Cercone. 1984)

43

 

 

 

  
     

 

 

 

ooou
mmzhkmmmsm... 1_<:zz< 25:2 :83 £200sz.
823.0“ sz_o<m6 4<2mmzh0m0 cow H .mwlw
E omhmums.
O. 20:53sz .=o
\
a. I \
mFHEL.
. ZOF<mm2mO
25030020 4 \ 1:0 “.0 hwmzo
. \
m I 2<_O_wmm_lmO s_\\\ \\
IIII 2505820.: \
25235 .2
N I
252035 .SIIII\
w 1 242030 2252932

 

252259352533522m...
_ _ _
car com com oov

 

 

._. . v. _.. m... n. n.— _2 n— m C

 

 

 

 

 

 

 

 

 

 

 

 

Zmomammm>o mmmhmfi Door
0 man—DU >mO._.m_—._ Aim—Du Z<O_IU:2 ._<m_._.zm0

Figure 7.

44

Figure 8. Northern Michigan Burial History Curve
1.000 Meters Cumulative Overburden.
(Burial Curve: From Cercone. 1984)

45

Pan

amazemisme ._<:22< 25:2

    

 

 

 

 

 

 

 

 

 

 

  
  

 

 

 

 

 

5.3.2 .
.—.ZN.O<I0 J<EIWIPOWO
Ex 2 $8. .mzoommu.
8.1.2.:
8:32.200 3 0 Fr
. ZO_._.<:w2mO.:O ZO_._.<EmeG
r H .__O LO $.sz m
M II
.11 252625 J
2526916.:
1 2<_O_>oazo .: w
a 252%....)
2523a: II
P I 25233 J p
z<_2o>mo.= /._2 2522623.:
2.: can con cow as.
_._.__._._._.__.___.._._.._o

 

 

Zmomammm>0 mmmhmfi. Door
0 m>mDU >m0...m=.. ._<_m_=m Z<0_:U_S_ ZEN-+5.02

Figure 8.

46

geothermal gradient of 23 oC/km. however. in the Southern
Michigan Burial History Curve a higher geothermal gradient
was used to estimate the commencement of oil generation.

In the Southern Michigan Burial History Curve. a
geothermal gradient of 31 oC/km. was used to calculate
the onset of oil generation. As a result of thinner units
in the southern portion of the basin. the magnitude of
cumulative burial was not as great as in other sections of
the basin. With a geothermal gradient of 31 oC/km.. only
rocks of Ordovician age and older are capable of oil
generation. Presently. the top of the ‘oil generative
window' is at about 1 kilometer from the surface. The base
of the ‘oil generative window’ (TTI=160) is not present in
the sedimentary section of the southern basin due to
shallow burial (Figure 9.). Under the assumption that
burial was greater and a gradient of 23 °C/km. was
present in the southern portion of the basin. the location
of the ‘oil generative window’ would be similar.

DISCUSSION QE HYDROCARBON GENERATION

From data presented in previous sections. the Michigan
Basin's thermal history has changed little since its
inception. A model using conodonts as indicators of
organic metamorphism. differs significantly from the
thermal model proposed by Cercone (1984) and concurs with
the geophysical model of the basin constructed by Nunn.
Sleep. and Moore (1984). One of the problems associated

with the geophysical model is the generation of

47

Figure 9. Southern Michigan Burial History Curve
1.000 Meters Cumulative Overburden.
(Burial Curve: From Cercone. I984)

48

Ex

F

252059,

. .vmm — .MZOUENU.
0.0N mmah<mm02wh 4<DZZ< 2<m2 Am F H _.F.:

. S #29320 252553 20F<mmzm0 4.0
.520 0 ".0 PmmZO

 
  

 

 

 

 

 

 

2<_ZO>wD .2 \.D
2<_10_mm_mw=2

co. can con cow
.._ v. _._._E_.._..__.,__.__._ o_

Zmomzmmm>0 map—MS. 000.. - . :
. o m>m=0 Zap—.9: ._<_mDm z<0=._0_5_ ZEN—9.50m

Figure 9.

49
hydrocarbons in the Devonian aged rocks of the central
portion of the basin. Nunn. Sleep. and Moore (1984). and
Vogler. et al.. (1981) postulate that Devonian oils have an
Ordovician source. and have migrated through the Silurian
section to Devonian resovoirs. Illich and Grizzle (1983).
Powell. et al.. (1984). and Pruitt (1983) suggest three
genetic groupings of oil in the Michigan Basin. They
propose that the Devonian rocks are mature enough to have

generated hydrocarbons i situ. Much of the Devonian

 

production is in the central portion of the basin and the
onset of oil generation is presently in the uppermost Lower
Devonian of the Central Michigan Burial History Curve.

Cercone (1984) points out that the Central Michigan
Burial History curve is not in the deepest portion of the
basin. As a result. oil generation may be beginning in the
Middle and Upper Devonian section in the deepest portion of
the basin. Nunn. Sleep. and Moore (1984) and Powell et
al.. (1984) point out that oils in the Devonian section are
immature. Construction of the ‘oil generative window’ from
the burial history curves and the conodont maturity data
suggests that Devonian oils in the central portion of the
basin would be immature. Additional burial in the central
portion of the basin or variation in the conductivity of
source rocks may account for the presence of the oil window
in Middle and Upper Devonian sections. A geothermal
gradient of 23 °C/km. is capable of accounting for

Devonian oils.

50

Ordovician oils are located in reservoirs associated
with hydrothermal dolomitization events (e.g. Albion-Scipio
and Northville Fields) on the southern flanks of the
basin. From previous sections. additional overburden or an
average geothermal gradient of 31 °C/km. had to exist to
account for the observed maturity. When the ‘oil
generative window’ is calculated. the maturity of the oils
generated in southern Michigan would probably be immature.
Geochemical evidence from southern Canada indicates that
Ordovician oils are at a point where oil is being intensely
generated (Powell. et al.. 1984). A discrepancy exists
between the maturity observed in conodonts and the oil
geochemistry. This discrepancy could be explained by
higher than predicted geothermal gradients on the southern
flanks of the basin or migration of Ordovician oils updip
from central portions of the basin in response to a gravity
driven paleohydrologic system operating in the basin.

CONCLUSION

From the conodonts observed in the "Trenton Formation"
of the Michigan Basin:

1. Color Alteration Indices. in the "Trenton
Formation." range from 1.0 in the shallowly buried and
surface exposures of the basin to 2.5 in the deepest
samples from the basin.

2. With a geothermal gradient of 35 °C/km. during
the Paleozoic and a subsequent linear decrease to a present

day geothermal gradient of 22 oC/km. from the Permian to

51
the present. the observed maturity of the conodonts was
consistently overestimated.

3. From Color Alteration Indices and burial history
curves constructed in the Michigan Basin. a geothermal
gradient of 23 oC/km. best fit the observed maturity in
northern and central Michigan.

4. In southern Michigan observed maturity could not be
accounted for with a gradient of 23 oC/km. Additional
subsidence of 600 to 700 meters had to occur in the
southern basin or an average geothermal gradient of 31
°C/km. had to exist to account for observed maturity.

5. Higher geothermal gradients could be attributable
to gravity driven fluid flow of warm basin waters onto the
southern flanks of the basin.

6. Calculation of the ‘oil generative window’ for the
burial history curves in the Michigan Basin reveals that
oils generated in the basin are probably immature in the
Devonian section and marginally mature in other areas of
the basin.

7. The model constructed from the Color Alteration
Index concurs with geophysical models of the basin,
however. detailed studies of probable source rocks and rock
conductivities should be considered for a comprehensive

study of the Michigan Basin thermal history.

APPENDICES

Core sampled for conodonts in the

Esteem

30-20N-06W
01-06N-15W
25-23N-15W
07-24N-06W
11-12N-13W
14-25N-02E
Ol-OIS-OIW
26-03S-04W
05-05N-02E
02-01S-07E
07-O4S-O3W
29-O7S-04W
03-055-03W
10-OBS-O7W
15-025-02W
24-38N-10E
l3-33N-05E
24-26N-11W
23-28N-05W
30-33N-02E
09-25N-11W

14-03N-08W

API Number

21-039-33680
21-139-34268
21-101-34277
21-113-34078
21-123-13816
21-135-34070
21-075-33129
21-025-23039
21-155-27907
21-161-18940
21-075—22213
21-059-28407
21-059~22168
21-023-37704
21-075—26541
Indiana

21-141-29372
21-055-34319
21-079-34673
21—141-34957
21-055-34132

21-015-30137

52

Appendix A.

Operator

Hunt Energy
Omni Pet.
Shell
Dart Oil
Sun/Turner
Hunt U.S.A.
Total Pet.
Humble
Mobil
Torosian
Humble
Andersn Oil
Mammoth Pet.
Shell

Texaco

Shell

Shell

Shell

Shell

Shell

Shell

Shell

"Trenton Formation"

Farm Name

Wnterfld Dp. A-l
Hirde #1-1
Maidens #5-25
Brugger #3-7
Bradley #4-11
Big Creek #14
Harmon Luck #1-1
J. Riley #2
Jelinek-Ferris #1
Nerreter #1
Kryst/Comm. #1
Whitaker #2
Wooden #4
Bidwell #1-10

S. Konkol #1

R a L Mat. #1-24
Taratuta #1-13
Blair #2-24

Blue Lake #3-24
Allis #3-30
Weber-Schrn. #6-9

Timm-Kenndy #1-1

 

53

 

 

Epgpfiipg API Number Operator Farm Name
16-09N-15E 21-151-25357 Humble Hoppinthal #1
11-l4N-04E 21-017-37779 Shell Prevost #1-11
28-24N-02E 21-129-25099 Sune BrzoS St. Fstr. 1
05-38N-24W Outcrop Bark River 22.0.

@ CA1 provided by Repetski

and Harris.

1981. U.S.G.S. Rept.

* Specimens from outcrops provided by Dr. Robert Votaw.

Indiana University at Gary

54

Appendix B.

Burial History Curves Constructed in the Michigan Basin

55

pl-

Svoassé 22:51.50.

 

 

 

Exho.
~\1co.u_>o1.0.2
223.630 .3

 

    

 

 

 

 

:0.5:m
- . 23:0).
5.32.3332
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