Pennsylvanian Deltaic Sedimentation in Grand Ledge, Michigan

Western Michigan University ScholarWorks at WMU

Master's Theses Graduate College

12-1982

Jeffrey R. Martin

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Recommended Citation Martin, Jeffrey R., "Pennsylvanian Deltaic Sedimentation in Grand Ledge, Michigan" (1982). Master's Theses. 1674. https://scholarworks.wmich.edu/masters_theses/1674

This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. PENNSYLVANIAN DELTAIC SEDIMENTATION IN GRAND LEDGE, MICHIGAN

Jeffrey R. Martin

A Thesis Submitted to the Faculty o f The Graduate College in partial fulfillment of the . requirements for the Degree of Master of Science Department of Geology

Western Michigan University Kalamazoo, Michigan December 1982

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. PENNSYLVANIAN DELTAIC SEDIMENTATION IN GRAND LEDGE, MICHIGAN

Jeffrey R. Martin, M.S.

Western Michigan U niversity, 1982

Pennsylvanian outcrops along the Michigan Basin's southern / margin are composed o f flu v ia l-d e lta ic and marine shelf sediments.

Constructive d e lta ic facies include point-bar sandstones displaying

erosional bases, channel lag, and upward decreasing grain size and

sedimentary structures. Cross-stratification data indicate a uni-

modal, highly variant, northward-trending, paleocurrent pattern that

deviates from regional paleoslope. Point-bar sandstones record

delta plain deposition by meandering d is trib u ta ry channels. Channel

margin facies include Lingula-bearing, interdistributary bay shales;

overlain gradationally by laminated, flaser-bedded and rooted marsh

shales and siltstones; and subbituminous swamp coal. Bay-fill facies

are interrupted by lens-shaped, quartz-poor, fine-grained, crevasse--

splay sandstones.

Delta destructive facies--quartz-rich bioturbated sandstone--

suggest delta lobe abandonment and landward reworking o f delta fro nt

sands over the subsiding deltaic plain. Subsidence resulted in

deposition of th in , marine shales and overlying m icrites which contain

diverse marine fauna and £20% terrigenous clastic detritus.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS

I would like to thank Professor William B. Harrison and the late

Dr. W. David Kuenzi fo r th e ir help and encouragment in the completion of

th is thesis. This report was possible thanks to the help o f the Eaton

County Parks system and especially to Jane McCullough, the park director

and n a tu ra list o f Fitzgerald Park. I would also lik e to thank my col

leagues Mary Davis and Dean Bredwell who provided additional information

and alternative ideas fo r the deposition of the Pennsylvanian sediments

in the Grand Ledge lo c a lity . I thank Dr. W. David Kuenzi, Professor

William B. Harrison, Dr. Thomas Straw, Dr. Richard Passero, and a ll of

Western Michigan University for reviewing and editing this thesis.

Finally, thanks are given to Gulf Oil Exploration and Production Company

who helped in the drafting and duplication of this project.

Jeffrey R. Martin

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MARTIN, JEFFREY R.

PENNSYLVANIAN DELTAIC SEDIMENTATION IN GRAND LEDGE, MICHIGAN

WESTERN MICHIGAN UNIVERSITY M.S. 1982

University Microfilms

International 300 N. Zeeb Road, Ann Arbor, M I 48106

MARTIN, JEFFREY R.

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ACKNOWLEDGEMENTS . . . . ' . . . • . i i

LIST OF FIGURES ...... • • ' • • • • • V

INTRODUCTION ...... 1

Previous Investigations ...... 4

Correlation with other Basins ...... 4

Regional Geology and Structure ...... 6

Stratigraphy ...... 8

INTERPRETIVE ANALYSIS OF ENVIRONMENT ...... 12

Criteria for the Recognition of Depositional Environments ...... ^ ...... 13

Transitional Facies and Inferred Environments . . . 15

Marine Facies and Inferred Environment ...... 29

T erre strial Facies and Inferred Environments . . . . 35

PALEOCURRENT ANALYSIS . .. . . , .,...... -. • • • • • • 56

PETROLOGY ...... • • • • . • • • • • • • • • • . • • • • 61 Megascopic Examination ...... 61

Textural Parameters ...... 67

Channel Sandstones ...... 70

Splay Sandstones ...... 72

Reworked Marine Sandstones ...... 77

Other Samples (excluding sandstones) ...... 78

Chemical Constituents ..... 97

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SUBSURFACE DATA ...... 100

DEP0SITI0NAL MODEL AND THE HISTORY OF SEDIMENTATION ...... 106

Delta Plain or Channel Margin Facies ...... 106

Marsh Subenvironment ...... 106

Bay Subenvironment . . . 108

Levee Subenvironment ...... 108

Abandoned Channel Subenvironment ...... 109

Crevasse Splay Subenvironment ...... , . 109

Destructive Delta Phase . , , ...... , . . , . . . 110

Reworked Sandstone ...... •. • • • HO

Black Calcareous Shale and B io m ic rite ...... «. I l l

Meandering Channel Facies ...... , . . . . . I l l

Channel Lag Deposits ...... I l l

Point Bar Deposits ...... 112

CONCLUSIONS ...... • • • • • • • • 115 APPENDIX I ...... 120

APPENDIX I I ...... 121

SELECTED BIBLIOGRAPHY ...... 122

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES

Figure Page

1. Index map ...... 2

2. Locations of measured sections ...... 3

3. Paleogeologic map of the Pennsylvanian (after Shideler, 1969) ...... 7

4. Measured columns—Lawson and Clay Products Quarries ...... 16

5. Measured columns—Dam Site and American V itrifie d Quarry ...... 17

6. Measured columns—Face Brick Quarry ...... 1 8

7. Coarsening upward sequence—Clay Products ...... 19

8. Closer view o f figure 7 ...... 20

9. Type coarsening upward sequence— Clay Products ...... 22

10. Coarsening upward sequence— American V itrifie d ...... 23

11. Rippled bedding in very fine sandstone— American V itrifie d ...... 25

12. Banded siItsto n e —American V itrifie d ...... 26

13. Close-up o f banded siItstone (note internal structure) ...... 27

14. Stigmaria-rooted siltstone— coarsening upward sequence—Clay Products ...... 28

15. Siltstone with iron concretions— American V itrifie d ...... 30

16. Close-up o f siltsto n e with con cretio ns ...... 31

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES (C on't.)

Figure Page

17. Close-up o f sandstone lenses above co a l~ American V itrified (note interlaminations o f shale and very fin e sandstone) ...... 32

18. Channel lag deposit—Fitzgerald Park ...... 36

19. Close-up o f channel lag ...... 37

20. Close-up o f channel lag—Face Brick ...... 38

21. Sandstone above channel lag—Face Brick ...... 40

22. Discontinuous coal seams— Fitzgerald Park ...... 42

23. Measured columns—Fitzgerald Park ...... 43

24. Measured columns—Fitzgerald Park ...... 44

25. Massive bedding—Fitzgerald Park ...... 46

26. D iffe re n tia l weathering—upper bedded section— Oak Park ...... 47

27. Measured columns—Oak Park ...... 48

28. Summary o f Crossbed Measurements ...... 49

29. Thinly-bedded un its— upper part o f outcrop—Fitzgerald Park ...... 51

30. Lithofacies map o f Interval "A" ...... 52

31. Lithofacies map of Interval "B" ...... 53

32. Lithofacies map of Interval "C" ...... 54

33. Thin section of Eaton Sandstone ...... 62

34. Thin section of Eaton Sandstone ...... 63

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES (C on't.)

Figure Page

35. Triangular diagram fo r samples-- Oak Park and Fitzgerald Park ...... 64

36. Triangular diagram fo r samples—Face Brick ...... 65

37. Thin section o f splay sandstone— American V itrifie d ...... 73

38. Thin section o f splay sandstone— American Vitrified higher in section ...... 74

39. Triangular diagram of samples— tr a ile r park g u lly and dam s ite ...... 82

40. Triangular diagram of samples— American V itrifie d and Clay Products ...... 87

41. D istribution o f subsurface data ...... 101

42. Facies map ...... 107

43. Type measured sections for correlation ...... 116

vii

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES

Table Page

1. Key to symbols used in measured section ...... 14

vi i i

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INTRODUCTION

Studies o f the rocks o f the Pennsylvanian System have been con

ducted throughout the United States and Great Britain with emphasis on

the id e n tific a tio n o f the depositional environments. The Michigan

Basin, lik e the other Pennsylvanian study areas, consists o f cyclical

deposits of arkoses, subarkoses, feldspathic litharenites, siltstones,

shales, and lesser amounts of coal and limestone.

The objective of this research is to identify the processes,

agents, and environments which resulted in the deposition of the cycli

cal rocks in the Michigan Basin. Outcrop exposures in the Grand Ledge

area (figures 1 and 2), 10 miles west of Lansing, Michigan, provide much

of the information used herein. In addition, well log information

enabled extrapolation o f rock types in to the subsurface. The Grand

Ledge sequence is a classic example o f Pennsylvanian sandstone bodies

and th e ir associated rock types in the Michigan Basin. Other Pennsyl

vanian sequences located in Jackson, Michigan, and in the Bay County

area are not as areally extensive or as complete as those o f Grand

Ledge.

Additional objectives, in the Grand Ledge locality, include (1)

mapping relationships between the various clastic facies, (2) inte

grating subsurface data and field relationships to determine the geo

metry o f these Pennsylvanian elastics (sand, s i l t , and cla y ), and (.3)

delineating physical properties of the Pennsylvanian sand bodies in the

Michigan Basin.

1 ' '

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2

SEC SEC

lo w io n

•I —

fa c t SEC In c h SEC

SEC SEC

Railroad

Figure 1. Index Map of Grand Ledge, Michigan

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 3

^ J Stream*

■ ■ i ■— Street* LAWSOI I I" Railroad

^ Quarrie*

FACE BRICK

AMERICAN VITRIFIED

FITZGERALD PARK

Figure 2. Location map showing measured sections and sample collection sites.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4

Previous Investigations

Grand Ledge outcrops, as well as adjacent subsurface data, have

been examined by previous investigators. Each of these investigators

has drawn separate conclusions as to the depositional history of these

sediments. Kelly (1933, 1936) was the f ir s t person to suggest a cyclo-

themic origin (Weller, 1930) for these sediments. Based on analysis of

cross-bedding, Potter and Siever (1956) concluded that the Pennsylvanian

quartzose sandstones of the Illin o is and Michigan Basins were channel

deposits. Shideler (1969), with the use of sandstone isolith patterns,

suggested sediment dispersal through northeast-southwest trending chan-

nelways. Dorr and Eschman (1970) believed that estuarine or deltaic

sedimentation could be responsible for the sediments exposed near Grand

Ledge. F in a lly, Davis and Bredwell (1975) suggested a b a rrier beach-

shoreline model.

Correlation With Other Basins

The sedimentological character of the Michigan Basin can be corre

lated with sim ila r Pennsylvanian depositional basins. Correlation has

been made with the Illin o is Basin where the same quartz-rich sandstones,

organic-rich siltstones and shales, and sublithic sandstones inter

fingering with shales e xist (Ethridge, 1976). Pryor and Sable (1974)

described the same area and noted cyclical deposits which resemble

modern-day flu v ia l-d e lta ic sediments. According to a fie ld guide com

piled by Horne and Ferm (1977), the Carboniferous deposits of the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appalachian Plateau f i t in to a sim ilar model. The Carboniferous rocks

of the Pocahontas Basin in northwestern Kentucky, one of the three major

basins of the Appalachian Plateau, have been correlated to various

counterparts in modern fluvial, deltaic, and barrier systems. Horne and

others (1971a), suggested that the limestone and the red and green

shales of Mississippi an age could best be explained as offshore bars and

islands. The overlying Pennsylvanian sandstones, siltston es, gray

shales, and coals were then characterized as barrier, lagoonal, lower

delta plain, upper delta plain and a llu v ia l plain sediments. The lower

and upper delta plain sediments (B re th itt Formation) are of p a rticu la r

interest since they represent the majority of the cyclical deposits of

the Pocahontas Basin (Baganz, e t al_., 1975). Englund (1974) and Donald

son (1974) both reached similar conclusions for the Carboniferous sand

stones, siltston es, and shales in the Central Appalachians of southwest

V irginia and southern West V irginia . In both studies, i t was noted that

a shallow water delta model with an adjacent strand plain best explains

the observed characteristics o f Allegheny, Conemaugh, and Monogahela

rocks in the central Appalachians. Brown (1969), in his study of north-

central Texas, postulated that the rocks of Upper Pennsylvanian and

Lower Permian age represent re p e titive sequences of open shelf, d e lta ic,

flu v ia l, and in te rd e lta ic depositional systems. In eastern Scotland,

Greensmith (1966) observed Carboniferous sandstones, siltsto n e s, shales,

and limestones which resembled the deltaic deposits described by Horne

and others (1971a). Greensmith's model included channel sandstones,

delta plain siltstones and shales, crevasse splay sandstones, delta

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. front sandstones, interdistributary carbonaceous siltstones and shales,

and fin a lly open shelf s ilt y carbonates. Wanless and others (1963)

attempted a regional study of the Summum, St. David, and Brereton Cyclo-

thems o f the Carbondale Formation o f Illin o is and the Marmaton Group,

DesMoines Series of the mid-continent. After they mapped the clastic

deposits, Wanless and others (1963) observed the following sedimentary

environments: (1) Missouri and Kansas were placed in a marine shelf

environment while at the same time (2) Illin o is , Indiana, and Kentucky

were in flu v ia tile , d e lta ic , and coal swamp environments.

Regional Geology and Structure

S tru ctu ra lly, the Michigan Basin is a s lig h tly e llip so id a l autogeo-

syncline, which was re la tiv e ly isolated from the adjacent basinal areas

by tectonic elements that exhibited positive r e lie f (Shideler, 1969).

Flanking this depressed feature is the Canadian Shield to the north-

northeast and the Wisconsin Arch to the west. The Algonquin and Findlay

arches act as barriers to the east and southeast, isolating the Michigan

Basin from the Appalachian Basin, while in the southwest the Kankakee

Arch separates the Michigan Basin from the Illin o is Basin.

The youngest Paleozoic deposits of the basin, Middle Pennsylvanian

age, are confined to the center o f th is isolated structure. Geographi

cally, the center coincides with the central portion of Michigan's

southern Peninsula (fig ure 3).

During the Pennsylvanian Period, Michigan was emergent. The Early

Pennslyvanian sediments were deposited on a slight angular unconformity

consisting of eroded layers of Mississippi an age rocks. Later in the

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ALLEGHENY OR DESMOINESIAN AGE INTERVAL C

LAMPASAN OR ATOKAN AGE INTERVAL B

MORROWAN AGE INTERVAL A

to '- \ > r - ' i - L

/LAKE\ 'ST.CLAIR

STUDY AREA

MILES

Figure 3. Paleogeologic map of the Pennsylvanian strata in the Michigan Basin (Shideler, 1969).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Early Pennsylvanian, the f i r s t of many minor marine advances deposited

sediments across the state. Deltas prograded from the east to the west

in to the basin (Cohee, 1965). The western edge of the state was under

marine conditions which deposited the red shales of the Saginaw Forma

tio n , while the basal sands o f the Saginaw Formation accumulated in the

remainder of the state. As the margins o f th is shallow sea began to

flu ctu a te , new seaways extended into the state from the south and south

west. Also, during deposition of the Saginaw, the central and western

parts o f the Michigan Basin were alte rna tely marine areas, swamplands,

and finally emergent coastal plains traversed by streams. According to

Cohee (1965), the end o f the Pennsylvanian was marked by the deposits of

meandering rivers and streams (Grand River Formation).

Stratigraphy

The Michigan Basin contains approximately 700 feet (209.6 meters)

o f lower and middle Pennsylvanian strata. Winchell (1861) subdivided

th is Pennsylvanian section in to three formations—the Parma Sandstone,

Saginaw Formation, and Woodville Sandstone. Since that time, many

geologists (K elly, 1936; Shideler, 1969; Davis and Bredwell, 1976) have

questioned the validity of the Parma subdivision.

The Parma sandstone is controversial due to its limited horizontal

and vertical extent. The rocks of the Saginaw Formation, interbedded

sandstones, shales, siltstones, coal seams, and limestones, are more

a really extensive than the rocks o f Parma age. The Verne Limestone, a

shaley biom icrite, was chosen by Kelly (1936) as a Saginaw key bed with

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 9

cyclical deposits above and below it. The final subdivision, Woodville

or Ionia, refers to a ll post-Saginaw formations. Kelly (1936) proposed

the name Grand River Group to avoid correlation difficulties. His group

included the Woodville, the Ionia, and the Eaton sandstones.

The Saginaw Formation often d ire c tly overlies the Mississippian-

Pennsylvanian unconformity, although in some lo c a litie s the basal Penn

sylvanian u n it is the Parma sandstone. Kelly (1936) described the Parma

subdivision as a clean, white quartzose sandstone with local occurrences

o f conglomeratic phases, dark shale members, and Calamites remains.

Grain size is medium to coarse sand, and, in places, the sands are

cross-bedded. The heavy mineral suite consists predominantly of tourma

line and zircon. In addition to these characteristics, the Parma sand

stone is cleaner, better cemented, and more continuously distributed

than the sandstones o f the Saginaw Formation.

In areas where the Saginaw Formation overlies the Parma Sandstone,

the Saginaw lithologies attain thicknesses of 400 feet to 535 feet

(119.8 to 160 meters). Individual units consist of sandstones, shales,

coal, and limestone with fluvial to marine origins. According to Kelly

(1936), the typical Saginaw sequence is as follows: a basal sandstone

overlain successively by sandy shale, gray fissile shale, underclay,

coal, black limey shale and limestone. Sandstones of the Saginaw Formation are le n tic u la r, discontinuous,

and irregularly bedded. Texturally, they are fine-grained with a con

glomeratic zone at the base. The mineralogy is principally quartz with

some decomposed feldspar and muscovite flakes. Heavy minerals make up

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 10

less than one percent o f the mineralogy, whereas, fragmented plant

remains are re la tiv e ly abundant in these sandstones.

The shales of the Saginaw Formation can be divided into three

groups: (1) sandy shales with characteristics similar to the sand

stones; (2) shales without sand, dark in color, and with some lime

present; and (3) underclays. The limey shales of the second group are

generally regularly bedded, while the non-limey shales vary from very

fissile to almost structureless layers bearing clayey nodular masses.

The center of the nodular masses often contains plant fragments. Lin-

gula and foraminifera are also found in the structureless shale. The

fissile and stratified shales are non-fossiliferous or they contain

macerated shells of the pelecypod Anthracomya. At Grand Ledge, the

succession is Anthracomya beds, followed by plant bearing shales, and

topped by a normal marine fauna (K elly, 1936). The underclays are structureless, white to light gray clay beds

with a sandy texture. This category of shales is known as "seatearths",

and they are commonly positioned directly beneath the thicker 1 to 3

feet (.3 to .9 meters) coal seams. The underclays are also charac

terized by irregularly shaped nodules of iron carbonate, 0.5 to 2 inches

(1.3 to 5.1 centimeters) in diameter.

The overlying sandstone has been named the Grand River Group by

Kelly (1936). The stratigraphic section of Kelly (1936), indicates an

unconformity between the Saginaw Formation and the Grand River Group.

The Eaton Sandstone o f the Grand River Group is a massive cross-bedded,

coarse-grained sandstone with a low percentage of mica and an iron

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 11 stained appearance. The basal portion o f th is coarse sandstone is

conglomeratic, containing large fragments of coal, shale, limestone

nodules, clayey ironstones in a sandstone matrix of quartz grains, and

feldspars and heavy minerals in a siliceous or ferruginous cement.

Individual beds at Grand Ledge show rusty layers alternating with white

layers, suggesting that the color originated contemporaneously with the

formation o f the sediment (K elly, 1936). The Eaton Sandstone has also

been characterized by two divisions, a lower massive unit and an upper

thinly-bedded unit. These two divisions are easily distinguishable at

Grand Ledge and th e ir boundary is sometimes marked by a shale parting or

an iron concretion layer.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INTERPRETIVE ANALYSIS OF ENVIRONMENT

The texture, mineralogy, and paleontology were determined using

binocular and optical microscopes, a mechanical stage and an item tabu

la tin g counter. The sedimentology was based on fie ld measurements which

included a study of the sedimentary structures and their corresponding

paleocurrent measurements. The geometry of the c la s tic bodies was

determined with the help of subsurface well log data.

The petrographic examination was the same for each of the 50 sam

ples collected. The routine started with a brief scan of the thin

section to determine a rough estimate of the size and the composition of

random grains. This technique was used to determine the calibration of

the counter used in each modal analysis of 300 points. The point count

then substantiated the estimates made of framework grains, matrix,

cements, and pore space. The essential framework grains (quartz, fe ld

spar, and rock fragments) were then recalculated to 100 percent and

plotted on a triangular diagram designed by Folk (.1966).

Additionally, textural examination was made for another 100 points.

The textural characteristics under consideration were grain size, sort

ing, roundness, feldspar a lte ra tio n , and grain contacts. Calculations

for both mean grain size and grain size sorting were based on 100 grains

using the formulas explained in Folk (1974, p. 55). Roundness classi

ficatio ns were made on 25 grains of the two most abundant grain species,

quartz and feldspar. Roundness was determined using the standard round

ness chart (P ettijohn, e t al_., 1972, p. 586). With each o f the grains

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13 in the appropriate class, the mean roundness was calculated numerically.

The mean feldspar alteration was identified using similar classes; these

were based on the percentage o f a lte ra tio n . The packing or the amount

of grain contacts was measured using a sketch of fabric terminology

(Pettijohn, et al_., 1972, p. 91). The firs t 25 grains were used to

determine the average number o f contacts per grain.

Field measurements involved the examination of the recognizable

sedimentary structures (Table 1). Vertical sequences, throughout the

area, were measured and examined fo r variation in texture and struc

tures. Several vertical sequences were measured in Fitzgerald Park to

determine the size and extent o f the cross-bedded units. Numerous

paleocurrent measurements based on cross-bed dips were also taken in the

park since this location provided a large number of cross-stratification

sets.

The remaining study involved delineating the geometry of the depo-

sitional environment, using both subsurface information and the mean

paleocurrent directions. The subsurface data were compiled from wells

in the Lansing area (Davis, 1976).

Criteria for the Recognition of Depositional Environments

Three facies divisions were recognized a fte r examining the rocks of

Grand Ledge. The groups include terrestrial facies, transitional fa

cies, and marine facies. The corresponding environments of the terres

t r ia l facies, the channel lag and the channel f i l l , are part o f the

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LEGEND

LITHOLOGY SCALE IN FEET

T T mrT T 7 m • • 0 • • 20 Massive Sandstone P • • • • • • ! • • • # » Medium-to fine-grained 15 Sandstones

Sandy Conglomerate 10

5 0 — I — Siltstones — 0 — • 0 _ 0 — 0 0| | | --- M Interlaminated - 0 0 — 00 Silts and Shales 00 — Silty Shale ACCESSORIES

Shale ^ o r y O \ Channel Lag Coal ,Ve Iron Concretions

Biomicrite Fossils

Unconformity Plants or Carbonaceous Matter

SEDIMENTARY STRUCTURES

Trough Cross-beds s - Rippled Beds

Planar Cross-beds £ £ f* Burrows

Avalanche Beds / I ^ Roots 7 -0 ' j '* ! {

JL Wedge-Shaped 2, Cross-beds

Table 1. Key to symbols used in measured sections.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15 fluvial channel environment. The transitional facies includes repre

sentative deposits from either a flood plain or a delta plain environ

ment. The subenvironments include in te rd is trib u ta ry bays, marshes,

swamps, and crevasse splays. The remaining divisio n , the marine facies,

is represented by limestones and shales o f the bay environment and by

reworked sandstones o f the delta fro n t environment.

Transitional Facies and Inferred Environments

The firs t recognized division, the transitional facies, is repre

sented by the basal portion of the Grand Ledge s tra ti graphic column

(fig ure 4). Representative samples from th is facies are found in the

Clay Products Quarry, Lawson Quarry, parts of the American V itrifie d

Quarry (figure 5), and in to the Face Brick Quarry (figure 6).

According to Davis and Bredwell (1975), the lowest unit o f the

facies is a fine-grained, quartzose sandstone containing thin shales or

shale pebbles. Since the base of the unit was not exposed, the thick

ness has not been determined. Above this sandstone lie s 2 meters (6.7

feet) of plant-bearing, gray siltstone. Calamites, Neuropteris, and

Annul aria have been id e n tifie d in th is u n it (Arnold, 1949).

A coarsening upward sequence (figures 7 and 8), 6.7 to 13.4 feet (2

to 4 meters) thick is situated above the gray siltstone. The base of

the sequence is marked by a black, b rittle , fissile shale with sandy

laminae. Vertically, the sequence grades into a soft, blue-gray, Lin-

gula-bearing shale. The shale then coarsens into an alternating u n it of

shale and very fine-grained (1 mm thick) sandstone laminae. Proceeding

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 16

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 00 0 0

.. § . 0 0 P # _ ' 0 • . # in. • 0 0 FACE BRICK Q Brick Quarry (see Figure 2 and Measured sectionMeasured taken w ithin Face Table 1). Figure 6

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VO Siltstone with plant fossils concretions S ilty shale more brackish Siltstone with iron some Figure 7. coarsening One upward exposed sequence in Clay Products Quarry.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 20

M M M H PM illll t

Siltstone with some iron concretions

S ilty shale more brackish

Siltstone with plant fragments

Figure 8. Closer view of the same coarsening upward sequence and one o f the measured sections from Clay Products Quarry.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 21 upward (fig ure 9), the sequence becomes more sandy u n til the shale bands

finally disappear. Overlying layers show increasing sand content,

especially mica, in a root-penetrated coarse siltstone or very fine

sandstone. The roots become extremely abundant at the top of the se

quence until an underclay and coal are encountered.

After the three feet (.9 meters) of lignite or bituminous-grade

coal, the sequence above is covered by talus. According to Davis and

Bredwell (1975), the upper 13.4 to 20 feet (4 to 6 m) sequence is com

posed of primarily coarse-grained siltstone containing two 11.8 inch (30

cm) coal beds.

Correlation between the Clay Products Quarries and the American

V itrifie d Quarry has been attempted by Kelly (1933). He noted that the

entire coarsening upward sequence was represented in both locations,

although the Lingula shales and the plant-bearing shale are no longer

exposed in the American V itrified section (figure 10). About 10 feet (3

m) of very fine-grained, white, quartz-poor sandstone with shale lamina

tions is found above the coal in the coarsening upward sequence of the

American V itrifie d Quarry. La tera lly the very fine-grained, lense-

shaped sandstone grades to a gray, sandy siltston e and fin a lly to a gray

shale. These lensoid sandstones are commonly white to pale gray in color,

quartzose, and very fine-grained. According to microscopic examination,

these sandstones contain enough mica, rock fragments, and feldspar to be

called feldspathic litharenites *n t^1e American Vitrified

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 9, The typical coarsening upward sequence found at Clay Products Quarry (the detailed section is represented by section 0 on figure 4).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 23

n *T»*

Mostly very fin e sandstone beds with thin shale partings

Interbedded very fine sandstones and shales

Coal

Siltstone with iron concretions

Figure 10. A coarsening upward sequence found in American V itrifie d Quarry (the detailed section is represented by section M on figure 5).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 24

Quarry, the sandstone lenses range in thickness from 2 to 20 centi

meters. The thickness variations are the result of the size and the

amount of the th in , dark, shale laminations between sandstone beds.

Another thickness discrepancy is discovered when trying to correlate

between the American V itrifie d Quarry and the Face Brick Quarry. The

sandstone lenses are much thicke r, from 1 to 4 feet (.3 to 1.2 m) th ick,

in the Face Brick Quarry section. In both lo c a litie s though, the sand

stones contain either small-scale troughs or wavy ripples o f about 2

millimeters thickness (figure 11).

The adjacent shales and s ilts to n e , in contrast, show poor bedding

characteristics, although Davis and Bredwell (1975) indicated the pre

sence of loadcasts and linguoid ripples in some of the slabby beds of

siltsto n e .

The rocks of the transitional facies are most readily interpreted

as flood plain deposits or delta plain deposits. Specifically, the

sediments o f the coarsening-upward sequence compare favorably to an

interdistributary bay-fill as described by Donaldson and others (1970).

The abundance of Lingula and foraminifera and the lack of other fauna

indicates a restricted portion of the bay. Directly above the Lingula

shale is the "banded siltstone" which has previously been described from

marshy environments. The "banded s iltsto n e " (figures 12 and 13) is

about 3 feet (.9 m) thick and was probably bordering the bay, as indi

cated by the occurrence o f a single Lingula brachiopod found at the

base. The next unit, the Stigmaria-rooted siltstone (figure 14), repre

sents a shallower, more sheltered environment probably farther inland

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. American American V itrified on figure Quarry 5). (the detailed section is represented by section L ro F ig u re 'll. An example of the rippled bedding observed in the very fin e sandstone w ithin

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ro section on M figure 5). An An example o f the banded siltsto n e found in American V itrifie d Quarry (see Figure 12

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. thinner dark laminae are organic-rich shales whereas the thicker lig h t laminae ^ are quartz-rich coarse s ilts or very fin e sands. " j A A close-up view of the siltstone banded same to show internal structure. The Figure 13

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. oo ro Stiqmaria Roots Products Quarry (see section 0 on Figure 4). The The Stiqmaria-rooted siltstone from the coarsening upward sequence in Clay Figure 14

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 29

from the bay. The siltstone above, containing iron concretions (figures

15 and 16), probably represents a lith ifie d underclay beneath the coal.

Classically, the underclay has been interpreted as an old soil zone

(K elly, 1936); thus, i t should be located even further landward. The

coal probably formed in swampy conditions.

The sandstone lenses above the coal represent a d iffe re n t suben

vironment, especially re la tiv e to energy conditions. The lens-shaped

sand bodies and their distinctive litharenitic lithology may represent

crevasse-splay or overbank-flood deposits. The lateral gradation from

sandstone to siltston e to shale and the interm ittent shale laminations

(fig ure 17) between sandstone lenses is further indication o f a crevasse

splay subenvironment. I f the sandstone lenses do represent splay de

posits, then i t seems reasonable that the rooted siltsto n e is a levee

deposit.

Marine Facies and Inferred Environment

The marine facies is represented by the Verne Limestone. The best

exposure of th is facies is found in the Face Brick Quarry above the

root-penetrated micaceous sandstone of the tra nsition al facies. Accord

ing to Davis and Bredwell (1976), the "rooted siltstone" consists of 10

to 13.4 feet (3 to 4 m) o f gray, limey siltston e or very fin e sandstone,

overlain by about 1.7 feet (0.5 m) of black fossiliferous limestone.

Davis and Bredwell (1976), included this limey siltstone in the marine

facies after observing carbonate patches on or between quartz and mica

grains. Petrographic examination suggests that the carbonate patches

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CO O iron concretions section on M figure 5). Figure 15. The siltstone containing iron concretions from American V itrified Quarry (see iron concretions

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CO iron concretions iron concretions siltsto n e at Clay Products Quarry (see section 0 on figure 4). Figure 16. A close-up view of the iron concretions in the siltstone above the rooted

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 32

Very fine sandstone

Figure 17. A close-up view of the sandstones lenses above the coal at American V itrified Quarry. Note the interlaminations o f shale and very fin e sandstone between lenses (see section M on figure 5).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 33 are a secondary diagenetic e ffe c t, rather than a primary cementing

agent.

It is suggested herein that the Verne Limestone represents the only

documented open marine environment in th is sequence o f rocks. The Verne

Limestone is a black, quartz-rich, sparse, brachiopod and crinoid bio-

mi crite according to Folk's (1962) cla ss ific a tio n . Although brachiopods

and crinoids appear to be the most abundant, Mary Alexander (1968) found

a moderately diverse fauna of four brachiopod species, with the produc-

tid s being the most common; two gastropods, one high-spired form and one

low-spired, turbinate form; a stra ig h t n a utiloid cephalopod; a lacy

bryozoan, Archimedes; a tr ilo b ite ; a pelecypod; a horn-shaped, rugose

coral; crinoid stems; ostracods; and foraminifera.

Kelly (1936) found tha t the Verne Limestone can occur in two v a ri

eties, either a continuous bed or as 3.9 inches (19 cm) thick nodules.

Both varieties are surrounded by a black, coaly shale. The more con

tinuous, bedded limestone is typical of the Face Brick locality, while

the nodular limestone is more commonly found at Lawson Quarry.

The Verne Limestone probably represents a shallow marine environ

ment lik e the seaward reaches o f an in te rd is trib u ta ry bay. This would

explain the occurrence of 10 to 15 percent terrigeneous s ilt- and clay

sized grains, as well as the presence of a sparse marine fauna. The

substrate was probably soft as suggested by the presence of the spine-

bearing, productid brachiopods. The soft substrate is likely responsi

ble for the lower diversity of species, since many marine invertebrates

need a firm bottom to survive.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 34

The discontinuous nature of the Verne Limestone and the limestone

pods surrounded by the black coaly shales appears lik e modern day car

bonate mud mounds (M ulter, 1975). The organisms enclosed in the bio-

mi crite suggest a semi-restricted environment like at the mouth of an

in te rd is trib u ta ry bay. In th is environment the suspension feeders would

receive enough nutrients from the incoming currents while at the same

time coaly shales from a more euxinic environment were being deposited.

The black, coaly shale surrounding the limestone was probably the result

o f fine-grained sediment s e ttlin g out o f suspension, in an in te rd is tr i

butary bay.

The Stigmaria roots in the siltstone underlying the Verne Limestone

are primarily subparallel to one another, like the mangrove roots de

scribed by Multer (1975). The root-bearing micaceous sandstone would

then fa ll into the upper part o f a tid a l f la t environment or the seaward

portion of a marsh environment. The unit below, where the plant roots

are less dense and the iron concretions become more abundant, signifies

a probable tidal fla t deposit. Sedimentation would have been slow,

allowing the iron concretions to form in the thin laminae of shales and

sandy siItstones.

At the Face Brick Quarry location, the tidal fla t and bay sequence

differ due to the addition of a highly bioturbated, medium gray, coarse

s ilt- to fine, sand-sized unit. The bioturbation was probably caused by

burrowing organisms because the pattern crosses and the individual

burrows do not taper like plant root penetrations. According to petro-

graphic analysis, a representative sample of this unit contained the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 35

highest percentage of quartz and the lowest percentage o f rock fragments

(Q85F15^ The bioturbated sandstone is probably marine as evidenced by the

abundance of burrows. It probably signifies delta destructive processes

such as delta lobe abandonment and subsidence. The subsidence would

then enhance the landward reworking by marine processes o f the delta

front sands which lie on the subsiding deltaic plain. The reworking of

the delta front sands has therefore resulted in the extremely clean,

well-sorted, quartz-rich nature of the reworked marine sandstone.

Continued subsidence might then explain the deposition o f the th in ,

black marine shales and the overlying m icrite .

T errestrial Facies and Inferred Environments

The terrestrial facies is represented by the Grand River Formation,

more s p e c ific a lly by the Eaton Sandstone. Exposures of th is sandstone

facies are found along the Grand River and Sandstone Creek. Localities

include the ledges o f Fitzgerald Park, the c lif f s o f Oak Park, and the

sandstone outcrop a t Face Brick Quarry. The subdivisions of the Eaton

Sandstone include channel lag, channel f i l l , and point-bar sandstones.

The Eaton Sandstone has an erosional base and lie s upon members of

the Saginaw Formation. The base o f the sandstone (figures 18, 19, and

20) is yellow-brown in color, medium-grained, and poorly sorted. The

poor sorting is the result of large shale clasts approximately 0.4 to

7.9 inches (1-20 cm) in length. The shale clasts are s till fissile but

have very irregular to nodular shapes. The irregular shape of the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CO CT>

Channel Channel lag Limestone Limestone nodule iron concretions Fitzgerald Park, (see section G on Figure 24) Lag consists of coal, shale, and and limestone chunks. Shale chunk Figure 18. A channel lag deposit found at the base of one of the sections measured within

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CO iron concretions Coal Coal seam Coal Coal seam Figure 24). chunk L9. L9. A close-up view o f a channel lag found in Fitzgerald Park (see section on G Shale Figure

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CO 00 indurated shale Limestone Limestone or Shale Shale chunk Silty shale ). 6 - f t > are prim arily on f i shalegure surrounded size by medium sand grains (see section P A A close-up view of a channel lag deposit at Face Brick Quarry. The clasts Figure 20 Si ISitstone

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 39

lowermost shale clasts is probably the result of differential compac

tio n .

Discontinuous coal seams, coal chunks, limestone clasts, and iron

stone nodules are also found in the basal sandstone o f the Grand River

Formation. The coal is lignite or bituminous grade and has a blocky and

folded appearance due to d iffe re n tia l compaction. The coal chunks and

limestone clasts, when compared to the shale clasts, are less abundant

and smaller in size, 1 to 9 inches (2.5-22.9 cm). The sandstone matrix

of th is basal sandstone also contains abundant iron concretions. These

siderite concretions range in size from 1 to 6 inches (2.54-15.24 cm)

with very irregular shapes.

The matrix of this "pebble conglomerate" is a fine- to medium-

grained, quartzose sandstone. In Face Brick Quarry the "pebble con

glomerate" attains a thickness of 6 meters, while in Fitzgerald Park the

thickness varies from 2.5 to 7.5 feet (0.65-2.15 m). Although the

sandstone is quartzose, i t also contains a sig n ifica n t amount o f fe ld

spar and rock fragments. Thus, from the composition ( 575^14^13 )* (1962) would c la s s ify the sandstone as lit h ic arkose approaching sub-

arkose. Minimal amounts of muscovite and zircon were also observed.

The f r ia b ilit y of the sandstones as observed in the fie ld is best ex

plained by a minimal amount of cement holding the subangular grains

together. The basal conglomeratic sandstone lacks bedding, but bedding is

apparent in the overlying sandstone sequences. At the Face Brick lo

cality (figure 21), the immediately overlying sandstone is massive,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Moderate Bedding

Massive Bedding

Figure 21. The sandstone above the channel lag a t Face Brick Quarry. Note how the sandstone is divided in to massive bedding at the base and moderate bedding toward the top (see section P on figure 6).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 41

while the upper ten feet (3 m) contains 1.6 to 4.7 inches (4-12 cm)

thick horizontal beds.

The conglomeratic zone (sandstone with shale clasts) of the Grand

River Formation indicates the basal portion of a fluvial channel. The

conglomeratic texture may be produced by rip-up clasts surrounded by a

medium-grained sandstone, an appearance typical of channel lag. Appar

ently these clasts were ripped up from a partially consolidated sediment

surface and transported by flu v ia l processes in stream channels. The

sharp, erosive, lithologic contact with the underlying rocks and the

clasts of shale ripped up from beneath are suggestive of a fluviatile

channel environment. Discontinuous coal seams (figure 22) are also

abundant in channel fills , although they are not the result of ripping

up coals from the Saginaw Formation. The coals are probably the result

of transported tree trunks or other vegetation trapped in quiet or cut

off portions of the channels. The iron concretions of the channel lag

u n it are probably best explained by levee deposits slumping in to the

pre-existing channel.

Natural outcrops o f the Eaton Sandstone range from 20 to 50 feet

(6-15 m) thick. The sandstone is white on a fresh surface and usually

yellow-brown from iron staining on the weathered surface. I t is medium-

grained a t the base, becoming fin e r grained upward as shown in the

measured columns (figures 23 and 24) observed at Fitzgerald Park. Thin-

section examination of the samples collected from the measured sections

reveal primarily a quartz and feldspar mineralogy. Most of the samples

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ro Coal Coal seams Park Park (see section I on figure 23). Figure 22. An example o f discontinuous coal in seams the channel lag found in Fitzgerald

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 43

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 44

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 45

from Fitzgerald Park and Oak Park (figure 25) are arkosic or subarkosic

^62-76F19-33R0 - ll^ The Eaton Sandstone is fa ir ly massive at the base (fig ure 25),

while i t becomes extensively bedded in the middle and upper portions of

the outcrop (figure 26). The massive portion is best exhibited at Oak

Park (fig ure 27) where i t lie s unconformably on the Saginaw members or

on the channel lag.

The basal u n it o f the Eaton Sandstone (figure 23, column I ) , lie s

directly upon the channel lag or "pebble conglomerate." It is primarily

massively bedded, although some isolated spots display large-scale,

trough-shaped cosets averaging 4 to 5 meters across and 0.15 to 0.6

meters th ick. Brunton compass measurements indicate that the trough

cross-beds have dips as great as 14 to 18 degrees.

In the middle unit of the Eaton Sandstone (figures 23 and 24), the

bedforms are essentially tabular sets of about 4 to 7 inches (6.2 to

17.8 cm) th ick. The in clin a tio n o f the beds varies from planar cross

strata with dips of 20 to 30 degrees to trough cross-strata with only 8

to 12 degree dips. The most corranon trend fo r these strata is to the

north-northwest as shown by a mean current rose pattern (figure 28).

The upper unit (figures 23 and 24) reveals generally wedge-shaped

or smaller trough-shaped cross-strata. These sets are about 7 feet (2

m) across and only 7 to 11 inches (17.8-27.9 cm) thick. Cross-sets in

this portion primarily dip to the northeast-southeast and dips are

moderate, about 10 to 22 degrees. Small scale bedding, 0.5 to 1 inch

(1.3-2.5 cm) th ick, can be observed upon closer examination of these

cross-sets.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 46

Figure 25. An example o f the massive bedding observed in Fitzgerald Park (see section J on figure 23).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. section of Park Oak (see section C on figure 27). Figure 26. An example o f the d iffe re n tia l weathering found only in the upper bedded

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 48

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. S IT 1$'

A. it<* It in F ittg tfsld Pork oil Ik* mop »o,

FIGURE 28

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LEGEND

- ''T o p unit of fha Coton Sondatona

Middla unit of tho Colon Sondatona

-Boaol unit of tha Colon Sondatona

|| Maoaurad Saettona

Potaoeurrant Doto from Sitaa 2 0 -2 4 (Rafar to Appandix)

> s it e a

CM. lut

S ca le

Contour in la rvo t - 10 faat

SUMMARY OF CROSSBED MEASUREMENTS

The top o f the Eaton Sandstone (figures 23, 24, 27, and 29) is sub

horizontal with internal pinch and swell structures characteristic of

rippled bedding. Cosets are about 6 to 15 inches (15.2-38.1 cm) thick.

The ripples are therefore small scale, only 0.25 to 1 inch (0.64-2.5 cm)

th ick. The measurements taken from these nearly horizontal beds trend

to the east-southeast with the majority of the dips between 5 to 12

degrees.

The Eaton Sandstone has frequently been referred to as part o f a

superimposed fluvial-deltaic environment. In Potter and Siever's (1956)

scheme, the quartzose, cross-bedded sandstones were channel deposits.

Their interpretation was determined by examination o f the sedimentary

structures associated with available outcrops and by using paleocurrent

measurements. Shideler (1969) was also convinced that th is sandstone

u n it represented northeast-southwest trending channels. His methology

included the use of sandstone is o lith patterns (figures 30, 31, and 32).

Dorr and Eschman (1970) in te rp re t the quartzose sands deposits as dis

tributary channel deposits of a deltaic environment. Davis and Bredwell

(1975) took a d iffe re n t approach as they examined the outcrops in the

Grand Ledge v ic in ity ; th e ir model considers the sandstones to be ba rrier

shoreline deposits.

Detailed petrographic examination, in addition to the decreasing

scale of sedimentary structures and the cross-stratification data,

suggests that the sandstones represent flu v ia l channel deposits. The

sedimentary structures indicate a decrease in the flow regime upward.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 01 in Fitzgeraldis tic Park. o f These units rippled pinching show bedding and (see swelling, section F on a figure character 24). Figure 29. These th in ly bedded units represent the upper part o f the outcrops found

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 52

r—7| INTERVAL 100 -20 0 BOUNDARY

2 0 0 - 3 0 0

I -100 3 0 0 - 4 0 0

MILES

Figure 30. Sand isolith map of Interval "A" (Shideler, 1969)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 53

INTERVAL V— • BOUNDARY m 1 - 5 0

5 0 - 1 0 0

>100

KJ.O :Pi6,

/LAKE\ 'ST.CLAIR

MILES

Figure 31. Sand isolith map of interval "B" (Shideler, 1969)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 54

INTERVAL £oOl 1 - 5 0 ' IZI BOUNDARY

o' 111 5 0 - 1 0 0 '

> 100'

LAKE -N-h

0 10 20 30 40 ____1 I L I I MILES

Figure 32. Sand isolith map of interval "C" (Shideler, 1969).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 55 According to Fisher and Brown (1972), the structures observed and the

upward fining of texture indicate point bar sequences of a fine-grained

meander belt. Further evidence supporting this conjecture is the mul

tiple orientations of the paleocurrent data. According to the paleo-

current analysis (Appendix 1 and figure 28), these sandstone bodies were

probably migrating point bars. Throughout Fitzgerald Park the vectors

change position, both horizontally and vertically, resembling a pattern

typical o f sediment migration. Because the underlying rocks are a t t r i

buted to deltaic environments, it seems that the Eaton Sandstone repre

sents a series of migrating d istrib u ta ry channels prograding over the

d e lta ic sediments o f the Saginaw Formation. Furthermore, the decreasing

grain size and lower flow regime supports sinuous channels rather than

straight ones. If the channels were straight, the vertical distribution

of grain size should remain almost constant regardless o f the energy

changes (Fisher and Brown, 1972).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. PALEOCURRENT ANALYSIS

The direction of ancient currents which transported the Eaton

Sandstone a t Fitzgerald Park and Oak Park was determined by measurement

of the orientation of cross-stratification in these rocks. This portion

of the study has been divided into 24 sites, each with at least 3 inter

vals represented (Appendix 1 and figure 28). Each interval is a summa

tio n o f numerous readings which have been classified and analyzed by

Park's (1970) computer program. His program w ritten in Fortran IV is a

trigonometric solution to the problem of rotating cross-strata; pre

viously all rotation was determined graphically. The program provides

data for plotting vectors which represent the direction of cross-strata

orientation (Appendix 1 and figure 28). Restacking the input data

yielded four intervals, each represented by a resultant vector in each

of the 24 sites where readings were taken. These regroupings made it

easier to categorize over 1,200 paleocurrent measurements.

This revised analysis o f the data suggests that a ll the resultant

vectors of the remaining 24 sectors indicate primarily northerly di

rections o f sediment transport (Appendix 1 and figure 28). Interval 1

o f the Eaton Sandstone suggests prim arily northeasterly flow ; interval 2

suggests northwesterly flow; interval 3 is more widely distributed, but

a northerly orientation s t i l l dominates; and interval 4 suggests a

southeasterly flow. The inconsistencies of the vector patterns between

the 24 sites and th e ir four intervals suggest changing of the current

direction through time. The resultant vectors also record reversals in

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 57 the flow direction, especially between interval 2 and interval 3. The

changing directional pattern, associated with an upward fining sequence,

is typical of laterally migrating channel and point-bar deposits (Vi-

sher, 1965).

The c ro s s -s tra tific a tio n data, obtained from Pennsylvanian outcrops

in Grand Ledge, indicate a unimodal, highly varient, northward-trending,

paleocurrent pattern. These northward-trending channels may have been

only local occurrences since they deviate from the regional paleoslope.

The regional paleoslope (Potter and Siever, 1956) dips to the southwest

and is based prim arily on subsurface measurements. Included in Potter

and Siever's (1956) study was a b rie f analysis o f the basal Pennsyl

vanian sediments in Michigan; however, th e ir analysis was based on only

fiv e samples from two widely-separated counties, Jackson and Arenac.

They found that the grand mean of the Parma Sandstone was approximately

239.2 degrees with 90 percent confidence lim ited to +40.1 degrees,

agreeing with the proposed southwest transport dire ction . The Parma

Sandstone, analyzed by Potter and Siever (1956) is not found in the

Grand Ledge lo c a lity ; therefore, the Eaton Sandstone may represent a

d iffe re n t paleocurrent trend because i t is younger than the Parma Sand

stone. Shideler (1969) noted that during the Atokan stage, paleonto-

logic s im ila ritie s among marine units in the Michigan and Eastern In te r

ior basins, plus a consideration of regional paleoslope, indicate that

the most feasible in le t fo r the Michigan embayment was to the southwest.

With the inlet in this position, currents could be trending to the

northeast or the southwest. In addition to the geometric configuration

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 58

of Atokan sediments, "interval B" (figure 31), Shideler examined the

orientation and configuration of Desmoinesian sediments, "interval C"

(figure 32). He found sand belts which trend in a westerly direction

and suggested they were channel sands of a flu v ia l system. I f Shi -

deler's (1969) proposed channels were part of sinuous meanders, the

la te ra lly s h iftin g point bars would create both southwest and northwest

trending paleocurrent measurements supporting the dominant northwestward

trends measured from Grand Ledge sandstone sections. The Early Penn

sylvanian Pounds Sandstone of southeastern Illin o is also has large-scale

festoon cross-beds with northeasterly dip. The northeast trend is

lo ca l, although grouped exposures o f the Pounds Sandstone, a member o f

the Caseyville Formation, also indicate both northeast and southwest

trends. According to Ethridge and Fraunfelter (1976), th is suggests

m ultiple channel development.

In the Giant City Park locality, Ethridge and Fraunfelter (1976)

took 41 measurements from the extensive outcrops of the Pounds Sandstone

and plotted them on a current rose. The rose diagram indicated that the

primary transport direction was to the south-southwest. Ethridge and

Fraunfelter noted that other sandstones from the same Caseyville Forma

tion trend to the north-northwest. These variations in current direc

tio n may be comparable to the pattern shown in the Eaton Sandstones

(figure 28 or Appendix 1), which are also Lower to Middle Pennsylvanian

in age. P e lle tie r (1958) took measurements o f the Late Mississippian aged

Pocono Sandstone in Pennsylvania and Maryland. His conclusions were

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based on 5,000 cross-bed attitudes taken at 254 localities. The summa

tion of the Mississippi an cross-bedding indicated a mean transported

direction of 290 degrees in the northwest quadrant. Pelletier also

grouped the Lower Pennsylvanian Mauch Chunk and the Lower Pennsylvanian

P o tts v ille sandstones. He found that the 181 readings taken from 12

localities yielded a mean transport direction of 295 degrees, again in

the northwest. These data support the northerly paleocurrent trends of

the Eaton Sandstone, because these sandstones are from sim ilar geologic

times.

A sim ilar study was completed by Meckel (1970) in the Central

Appalachians. The majority of the 246 readings were taken on the Lower

Pennsylvanian, the P o tts v ille Formation. Current rose diagrams showed

the mean transport direction, 327 degrees, was to the northwest. Meckel

also graphed his findings on the Middle Pennsylvanian, Llewelyn Forma

tio n . From the 38 readings taken, he found that the mean vector, 356

degrees, s t i l l indicated tha t sediment transport was to the north.

All of the previous authors studied paleocurrent directions from

c y c lic Pennsylvanian aged sandstones and a ll noted that northerly trans

port directions were apparent. Therefore, it seems possible that the

Pennsylvanian sandstones o f the Michigan Basin could have also had a

northerly transport direction despite Potter and Siever's southwest

regional paleoslope. The previous authors also suggest a source area to

the south or to the east which this author's data support. Potter and

Siever (1956), on the other hand, suggest a Canadian or Northern Appa

lachian source area.

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Major differences exist between the regional paleoslope and the

data obtained from the Pennsylvanian Grand River Formation. Possible

reasons for these differences are: (1) the limited readings of Potter

and Siever (1956) could have yielded insufficient and incorrect data;

(2) the paleocurrent data presented by Potter and Siever (1956) pertains

only to the Parma Sandstone which is not found at Grand Ledge; or (3)

the paleoslope has changed with time; thus a southwest direction could

be possible during the Lower Pennsylvanian while a northwest direction

occurred during the Middle Pennsylvanian.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. PETROLOGY

The majority of the samples were collected in Fitzgerald Park and

Face Brick Quarry because of th e ir well-exposed sections. The most

important lith o lo g y was the abundant channel f i l l , Eaton Sandstone.

According to petrographic studies, which included a 300 point count to

determine mineralogy and a 100 point count to determine textural charac

te ris tie s , the Eaton Sandstone fa lls in to the arkose or subarkose d iv i

sions of Folk (1966).

Megascopic Examination

The color ranges from buff to pale yellow on fresh surfaces to a

yellow-brown on weathered surfaces. The white spots found on weathered

surfaces probably represent weathered feldspar or altered mica. The

yellow-brown color of the weathered samples is the re sult o f limonite

staining.

The composition o f the sandstones (figures 33 and 34) can be deter

mined from the three component diagrams in figures 35 and 36.

Petrographic Examination

Mineralogy

The three detrital constituents, quartz, feldspar, and rock frag

ments, make up 92 to 97 percent o f the composition of the grains.

Quartz is the most abundant mineral averaging 65 to 75 percent of the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ro CT> Quartz Plagioclase Microcline grains are microcline, quartz, and rock fragments (thin section 10X). A A thin section showing the composition o f the Eaton Sandstone. The recognizable Figure 33. Fragments Rock

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. O'* CO Quartz Rock Rock Fragments Rock Rock Fragments Quartz Polycrystalline Quartz quartz, rock fragments, and muscovite (thin section 10X). Quartz Figure 34. A thin section showing the composition of the Eaton Sandstone. The grains are shown Muscovite

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CTl -p* ROCK ROCK FRAGMENTS Channel 16 MSRP - OAK PARK Symbol Symbol Samples Inferred Environment QUARTZ

Channel Splay Point Bars " ----

0} 5 -15' 2 18,19,20 — 22,23 S4 5-25' S , 5 - 2 3 '^ s j s - i s ' ^ S FITZGERALD PARK FELDSPAR • • • • • • o ® 21 Figure 35. Triangular diagram fo r samples collected in Park Oak and Fitzgerald Park. Symbol Samples Inferred Environment

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

ROCK FRAGMENTS Distributary Channel 13 13 Channel Lag 1,7 4,10,11 DistributaryBar Mouth FACE FACE BRICK © • 0 O A-6,-14,-16 Crevasse Splay Symbol Symbol Samples Inferred Environment o/o QUARTZ V V \/ \/ V \/ \/ FELDSPAR / \/ Figure 36. Triangular diagram fo r samples collected in Face Brick Quarry.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 66

composition after the components are recalculated to 100 percent. The

majority of the quartz is either monocrystalline (less than 5 degrees),

common quartz, or the monocrystalline (greater than or equal to 5 de

grees), the undulose variety. In most samples, the polycrystalline

quartz with greater than six units, the strained variety, is more common

than polycrystalline quartz with two to five units. The strained quartz

is characterized by extreme undulosity, elongate grains, and usually

sutured boundaries. The feldspar varieties are dominately untwinned

m icrocline, orthoclase, and plagioclase with small amounts of twinned

microcline and sodium plagioclase. The d istin ctio n between untwinned

feldspar and quartz was determined by checking the optical properties of

the grains instead of a rtificia lly staining the slides. Most of the

unweathered surfaces of these samples contain between 20 to 30 percent

feldspar grains, thus it is understandable why they have been classified

as arkoses and subarkoses.

The remaining grains are rock fragments including both metamorphic

and sedimentary types. The most abundant rock types are argillaceous

fragments with a few schistose fragments. The metamorphosed a rgilla

ceous grains are either slates or phyllites. They appear as s ilt- or

clay-sized grains which have been squeezed between more resistant grains

to the point where it is d ifficu lt to distinguish them from matrix

m aterial. Dickinson (1970) recognized a problem in the id e n tific a tio n

between matrix and squeezed, in te rstitia l rock fragments; that is why he

devised a system to describe the differences between the two. Following

Dickinson's definitions (1970), it is possible that the 5 to 15 percent

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. matrix found in the descriptions by Kelly (1936) and Davis and Bredwell

(1976) is actually a "pseudomatrix.11 Thus, the Dickinson terminology

has been used to determine i f the rock names given to the previously

studied Pennsylvanian sandstones are accurate. The minor constituents

make up on the average a trace to 5 percent o f the Eaton Sandstone. The

most noticeable minerals of this class are muscovite, chlorite, and

zircon. In some cases, the sandstones also contain tourmaline, apatite,

and pigeonite. Organic fragments are also included in th is division .

Textural Parameters

Textural characteristics, in addition to mineralogy, set the Eaton

Sandstone apart from the rest of the samples collected. Textural para

meters include size, sorting, roundness, feldspar a lte ra tio n , and grain

contacts.

The grain size of the total rock was measured for 100 grains. The

mean grain size was determined by f ir s t adding together the size values

of the 100 grains, then dividing by 100. In addition, the average grain

size was determined fo r quartz and feldspar in d ivid u a lly by measuring

the f i r s t 25 grains o f each.

Grain sizes were examined closely in the 17 samples taken from four

measured sections in Fitzgerald Park. From the calculated samples, i t

was found that sections 1, 2, and 3 are divided into four groups: basal

or interval 1, middle or interval 2, top or interval 3, very top or

interval 4. The grains o f interval 1 are between 0.30 and 0.35

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millimeters, thus placing them in the medium sand division on Went

worth's grain size scale. The grains of interval 2 show a marked de

crease in grain size (0.25-0.27 mm). The grains of interval 3 show

another decrease, falling into the fine sand category. In interval 3

the grain size ranges from 0.20 to 0.25 m illim eters with the m ajority

between 0.20 and 0.23 millimeters. In another part of this division

grain size ranges from 0.23 to 0.26 m illim eters, marking a reversal in

the decreasing grain size pattern. A sample of interval s was collected

from section 4 only. The grain size, 0.14 to 0.16 millimeters falls on

the lower end of the fine sand scale and it follows the normal fining

upward trend.

Interval 1 and interval 2 contained feldspar grains that were

larger than the quartz grains. This probably signifies that the feld

spar came from a closer source area. In intervals 3 and 4 the quartz

grains are s lig h tly larger than the feldspar grains. This is expected

in finer sands because quartz is more resistant to both physical and

chemical erosion than feldspar. This mineralogical reversal occurs at

the same point as the grain size reversal previously mentioned.

Roundness values were obtained using the following formula: Mean MF Roundness = where M represents class midpoints; F represents fre

quency; and i represents a summation sign. Roundness values were then

calculated for both quartz and feldspar by classifying 25 grains of

each.

Samples from the same measured sections were used and sim ilar

results were observed as in the size determinations. Most of the sam

ples are in the subangular category, although many of the samples are

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just short of the subrounded category. Very little correlation could be

made between degree o f roundness and stratigraphic position of the

samples. The patterns which do exist are as follows: interval 1 re

cords rounder quartz grains; interval 2 records equal roundness values

for both quartz and feldspar; and interval 3 records a significant

reversal where feldspar becomes s ig n ific a n tly more rounded than quartz.

Sorting values based on 100 grains were obtained by calculating the

standard deviation o f the grain size measurements (Folk, 1974). The

084% and the 016% were obtained graphically fo r each sample. The re

sults indicate fluctuations in sorting. Sites 1, 2, and 3 (figure 28)

all exhibit an increase in sorting from interval 2 to interval 3. This

pattern would be expected, since more uniform grains are commonly found

in fin e r sandstones. The coarser-grained sandstones were probably

deposited rapidly and thus a mixture of both coarser and fin e r sediment

resulted. The finer-grained sandstone, on the otherhand, was probably

transported farther; thus the coarser grains had a chance to be sorted

out. Despite an upward increase or decrease in sorting, the m ajority of

the Fitzgerald Park samples have a phi standard deviation between 0.35

and 0.50, therefore classifying them as well-sorted (Folk, 1968).

The percentage o f feldspar alte ra tio n as shown by 25 dominant

feldspar grains for each sample is between 0 to 6.25 percent. All the

samples examined are within the unaltered feldspar category. One pat

tern observed was a decrease in the amount of a lte ratio n from interval 1

to interval 3 with more alteration taking place in interval 3 as com

pared to interval 2. The least amount of feldspar alteration, between

0.5 to 0.6, was located in interval 2.

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Grain contacts were important when determining the amount of poro

s ity and permeability. The degree o f packing was based on the number of

contacts for the firs t 25 grains for each sample. Differential packing

seems to have occurred as shown by variable degrees of packing. I t is

apparent, however, that interval 2 is the most compact as shown by

sections 2, 3, and 4. An upward decrease in packing is noticed in the

same sections. This is logical since the lower parts of the section

would have been under more compaction while the upper parts would be

under the least amount of lithostatic pressures.

Channel Sandstones

The channel sandstones o f Face Brick Quarry are s lig h tly d iffe re n t

from the sandstones o f Fitzgerald Park. Petrology and the presence o f

shale clasts were used to c la ssify the channel sandstones as a separate

facies according to Davis and Bredwell (1976). P etrologically, the

channel sandstones, samples 4, 10, 11, and 13 on figure 35, contain more

quartz, less feldspar, and about the same percentage of rock fragments

when compared to other Eaton sandstones. The rock fragments are more

sig n ific a n t in sample 13, a channel lag sandstone with shale and lime

stone clasts.

Textural s im ila ritie s e xist between the channel sandstones and the

Eaton sandstones of Fitzgerald Park although they are not exactly the

same. Patterns in the textural characteristics of the Face Brick Quarry

samples are d iffic u lt to spot because the samples could not be obtained

from ve rtica l columns.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 71 The channel lag sandstone, sample 13, is very d is tin c tiv e from the

other channel sandstones. This "shale pebble conglomerate" (Davis and

Bredwell, 1976) is characterized by variable grain sizes ranging from

0.076 mm to 0.41 mm, excluding the shale, limestone, and ironstone

pebbles. The average grain size, 0.233 mm, is substantially smaller

than the other channel sandstones which average between 0.341 mm to

0.376 mm.

Sorting values between the channel lag and the other channel sand

stones also d iffe r because of the presence of shale clasts and other

large rip-up and transported materials found in the lag. In fact,

sorting is very poor in the channel lag sample while the other channel

sandstones are well sorted.

Differences are also apparent after reviewing the roundness values.

The roundness values range from very angular to subrounded in the chan

nel lag, while angular to rounded grains are found in the channel sand

stone samples. Mean roundness values are subangular fo r a ll the sam

ples, but the rho values are much smaller in the sample of channel lag.

The quartz is more rounded in the channel lag samples, while the channel

sandstones display more rounded feldspar grains.

The amount of alte ra tio n in feldspar grains is small in the channel

lag; comparable to the upper sand units from sites 1, 2, 3, and 4. The

feldspar alte ra tio n in the channel sandstone is higher and more com

parable to intervals 1 and 2 of sites 2, 3, and 4. Even though a range

from 0.54 to 0.82 exists fo r a ll o f the channel sandstones, they s t i l l

fa ll into the unaltered feldspar category.

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The packing values are low in the channel lag sample when compared

to the other channel sandstones. Samples 4, 10, and 11 have packing

degrees sim ilar to those o f the finer-grained top sands found in the

measured sections of Fitzgerald Park. Since the packing is lower than

the samples taken at Fitzgerald Park, it is logical to assume that the

porosity and permeability are better in the channel lag sandstone, even

though the channel lag has the poorest sorting.

Numerous s im ila ritie s are found between the textural character

is tic s of the channel sandstones from Face Brick Quarry and interval 1

from the sandstone ledges a t Fitzgerald Park. Both sandstones appear to

be basal portions of the Eaton Sandstone as shown by comparisons of

grain size, sorting, and the amount of feldspar alteration. The petro

graphic sim ilarity, in conjunction with stratigraphic positioning of

sites 1, 2, and 3 with the Face Brick site, further support the channel

sandstones being units of the Eaton Sandstone. I t is therefore apparent

tha t these minor distin ctions which were accentuated by Davis and Bred-

well (1976) are not s u ffic ie n t proof to isolate these sandstones into

two separate facies.

Splay Sandstones

Another sandstone found at Face Brick Quarry is the lense-shaped

splay sandstone (figures 37 and 38). From the triangular diagram ( fig

ure 36) samples A-6, A-14, and A-16 represent feldspathic litharenites.

Mineralogically they contain less quartz, between 62 and 65 percent;

less feldspar, between 14 and 17 percent; and more rock fragments,

between 19 and 22 percent, than the previously described arkoses and

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CJ Feldspar Chlorite Untwinned Chiorite Rock Rock Fragments Quartz Untwinned Untwinned Feldspar numerous rocknumerous fragments (thin section 10X). The The grains are shown quartz, untwinned feldspar, muscovite, c h lo rite , and Figure 37. A thin section of the splay sandstone collected in American V itrified Quarry. Quartz

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ■ Fragment Rock Muscovite Rock Rock Fragment * Fragment Fragment Muscovite Rock Fragment Rock higher in good the example o f section. pseudomatrix (Dickinson, Note 1972). the of abundance mica and (Thin rock section fragments. 10X). A ^ Fragment Rock Figure 38. A th in section o f splay sandstone collected in American V itrifie d Quarry but

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 75

subarkoses. In addition to the major minerals, ch lo rite and muscovite

make up as much as 5 percent of the total composition. The increasing

amounts of mica and rock fragments are best explained by the fluvial

system overtopping the banks or by the breaching of natural levees.

Since the mica and rock fragments are very fin e - to fine-sand sized, i t

is probable that the grains were being transported in suspension.

During flood conditions overbank flow or crevassing occurs causing the

fine sand deposits to spread out over flood plain or bay-fill shales and

siltstones.

The rock fragments appear squashed between and bent around grains;

therefore they have been c la ssifie d as pseudomatrix. The pseudomatrix

is most abundant in the splay sandstones. The author suggests that

lith o s ta tic pressures, the re su lt o f shale dewatering and compaction,

have caused the squashed appearance. The fin e r grain size, the abun

dance of micas and rock fragments, and the flood conditions are all

conducive elements fo r the formation o f the pseudomatrix.

Texturally, the crevasse splay sandstones d iffe r from the pre

viously described Eaton sandstones, most noticeably in grain size. The

average grain size ranges between 0.074 mm to 0.191 mm which compares

with the uppermost Eaton Sandstone units in Fitzgerald Park. In both

the splay sandstones and interval 3 o f the Eaton Sandstone, the quartz

grains are larger than the feldspar grains. This is not the norm in the

coarse-grained Eaton sandstones. Grain size s im ila ritie s between the

two are marked by the observed reversal pattern previously described.

Roundness values differ slightly, with most of the Fitzgerald Park

samples in the subangular category. Almost a ll o f the roundness values

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 76

for the splay sandstones are in the subrounded category. The quartz is

more rounded than the feldspars, which correlates nicely with the pat

tern o f medium-grained Eaton sandstones.

The packing is dominantly closed in the splay sandstones (3.4 to

4.0); thus, the porosity and permeability is greatly reduced. This

pattern could be anticipated because petrographically the splay sand

stones contain more rock fragments and mica flakes than the Eaton sand

stones. The presence of the pseudomatrix has increased the amount of

grain contacts and therefore reduced the number of open pores. The

finer grain size would further increase the packing, especially under

lithostatic pressures.

The feldspar a lte ra tio n is minimal in a ll the Pennsylvanian sand

stones observed. The splay sandstones are essentially unaltered, 0.50

to 0.62, which appears to be the same range for interval 2 and interval

3 from the sandstone sections o f Fitzgerald Park. These intervals fa ll

between 10 to 15 feet above the base in a ll the columnar sections. I t

appears that the source rocks had undergone very l i t t l e weathering

alteration before erosion and transportation.

According to Folk's textural maturity flow-sheet, the splay sand

stones (0.365 0 to 0.675 0) are prim arily moderately sorted and sub-

mature. Since a higher percentage o f rock fragments and micas are found

in the splay sandstones, i t is understandable that the sorting would be

lower. The moderate sorting is especially noticeable in Mary Alexan

ders' (1968) samples A-14 and A-16 taken from the southeast wall o f Face

Brick Quarry.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 77

Reworked Marine Sandstone

Face Brick Quarry is the only location where a sample of the re

worked marine sandstone was obtained. Quartz and feldspar make up

almost 100 percent o f the composition. The reworked sandstone, compared

to the other sandstones (figure 36, sample #7), contains the highest

percentage of quartz, up to 85 percent. Only a trace o f mica was ob

served in th is fine-grained subarkose, thus reinforcing the reworking by

marine processes. Other minerals are probably absent because of selec

tiv e sorting of elements by plants and animals which have disrupted the

bedding. The quartz grains are the dominant mineral as well as the most

stable.

The texture of the reworked sandstone is very sim ilar to the units

between 15 and 20 feet (4.5 m to 6.0 m) above the base of the Eaton

Sandstone. Average grain size d iffe rs between the two sandstones. The

reworked sandstone is very fine-grained (.114 mm) while the Eaton sand

stones only reach the fine-sand size category.

In contrast, sorting values can be correlated between the two

sandstones. Many of the phi values o f the Eaton sandstones approach the

0.425 0 value o f the reworked marine sandstone. Most of the correla

tives are in the upper 5 to 10 feet (1.5 m to 3.0 m) of the Eaton Sand

stone columns measured in Fitzgerald Park.

Roundness values follow the pattern o f the splay sandstones. Most

of the quartz and feldspar grains were subangular, similar to those of

the Eaton sandstones. I t was also noticed that quartz grains of the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 78 reworked sandstone were more rounded than feldspar grains, which is true

o f both the basal and middle units o f the Eaton Sandstone and a ll the

Saginaw splay sandstones.

Packing values of 3.84 are sim ilar to the crevasse splay sand

stones. Both of these finer-grained sandstones, despite mineralogic

differences, are packed tig h te r than the Eaton sandstones. Since the

packing is greater, the pore space is decreased and the permeability is

even smaller.

The feldspar alteration is very minimal, closely resembling the

a lte ra tio n in the splay sandstones. Another correlation could probably

be made between the reworked sandstone value, 0.54 unaltered, and the

upper parts o f the Eaton Sandstone, about 15 feet (38.1 m) from the base

of the outcrop.

Other Channel Sandstone

The other channel sandstones are compared to the major lith o lo g ie s

previously described. These remaining samples are important because

they improve the correlation between Fitzgerald Park, Face Brick Quarry,

Oak Park, Clay Products Quarry and Lawson Quarry. In addition to com

pleting the stratigraphic column, these samples also lin k marine and

non-marine facies.

Fitzgerald Park and Oak Park Samples

The remaining samples, 18, 19, 20, 21, 22, 23, 16, MSRP, and D

(figure 35), have closely related mineralogies; some even have similar

textures. The texture of sample 16 is quite different from the other

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 79

Eaton sandstones. The grain size, 0.185 mm, is fin e r than most Eaton

sandstones and w ithin the range o f the Saginaw splay sandstones. The

roundness value falls within the subangular category with quartz grains

being more rounded; th is is the typical pattern o f the basal part of the

Eaton outcrops. The distinctiveness of sample 16 is in the packing.

Packing is almost non-existent with most of the grains floating in an

iron oxide cement. This cement is either a secondary event or i t has

replaced the original grains and cement. Since large patches o f the

iron oxide are found on the th in section, a replacement cement is sug

gested. As much as 58 percent iron oxide replacement is recorded in the

300 points counted.

Sample 18 is another sandstone with slightly different textural

characteristics. The grain size, 0.340 mm, is comparable to the basal

units o f the Eaton Sandstone, including the channel f i l l sandstones from

Face Brick Quarry. Roundness values are approaching the subrounded

class, the feldspar (2.94 p) appears slightly rounder than the quartz

(2.90 p). The alteration value of 0.50 indicates the feldspar has not

changed character from its original form in the source rocks. The

packing value is low in sample 18 indicating higher porosity and per

m eability. This sandstone has very l i t t l e replacement iron oxide which

would be expected since the sandstone is a bone color. Apart from the

other Eaton sandstones, sample 18 contains more rock fragments o f the

pseudomatrix variety.

Sample 21 is quite d iffe re n t from the typical Eaton Sandstone. The

petrology consists of Q4g*r3i^21 ’ therefore, the percentage of quartz is

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 80 low, the percentage of feldspar is high, and the percentage of rock

fragments is as high as in the crevasse splay sandstone. The iron oxide

replacement makes up 17 percent o f the to ta l composition, which is the

mean fo r most of the sandstone samples. Muscovite appears as a trace

mineral in sample 21, whereas the splay sands contain as much as 5

percent mica.

The textural characteristics of sample 21 are very different from

the already described sandstones. The grain size, 0.174 mm is fin e r

than most o f the Eaton sandstones, but sim ilar to the splay sandstones.

The rock is well sorted; s lig h tly better than the basal sandstones of

the Eaton Formation and somewhat less than the splay sandstones of the

Saginaw Formation. The roundness values are less than any o f the pre

viously described sandstones although the Eaton sandstones also have

subrounded grains with rounder quartz grains. Alteration of the feld

spar is minimal, lik e many o f the other sandstones. The packing value,

1.84, is small. Thus, the porosity and permeability should be greater

in th is sample as compared to most of the Eaton samples, the splay

sandstones, and the reworked sandstones.

Sample 23 of figure 35 is also distinctive with the most noticeable

feature being the overall mottled appearance. The hand specimen is a

yellow sandstone with dark brown oval spots. The spots resemble iron

concretions without hard outer shells. These iron concretions have been

interpreted as primary events, as evidenced by the lack o f concentric

layers and by the sim ilarity of textural characteristics between the

matrix and the spots. A high percentage of replacement iron patches

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 81

(16%) is found in these pod-like concretions. The only other important

difference is that th is sandstone occurs beneath a discontinuous coal

seam.

The composition of sample 23 is similar to the Eaton sandstones, on

the low end Of the mineralogic scale (Qg 3 p33 R4 )* This sample contains the highest percentage o f feldspar o f a ll the sandstone samples. Grain

size and sorting is comparable to the basal units of the Eaton Sand

stone. Roundness is also distinctive as in sample 21; the grains are

subangular and the values are the lowest o f a ll the sandstones. The

feldspar alteration is slightly higher, 0.62, but s till only minimal.

Packing values are consistent with those o f the lower Eaton Sandstone.

T ra ile r Park Gully Samples

Figure 39 contains the mineralogic compositions of sandstones

collected from the following sites: Trailer Park gully, dam site, and

c l i f f across from sewer works. The composition of samples 24 through 30

resembles the sandstone ledges in Fitzgerald Park, with

Q60-70F20-32R3-12‘ Group 1 is made up o f samples 25, 28, and 30 shown on figure 39.

A ll these samples were taken in the ravine across from the Fitzgerald

Park entrance. In fa c t, the ravine is a continuation of the sandstone

ledges displayed along Sandstone Creek. The sandstones o f group 1 a ll

have a d is tin c tiv e banding lik e th a t of a layer cake. The bands a lte r

nate between white friable sandstones and limonite-stained indurated

sandstones. In addition to having a primary iron cement, the yellow

brown layers have patches of replacement iron oxide, between 11 to 19

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

ROCK FRAGMENTS Splay Channel DAM SITE orWORKS SEWER O 27 ® 26 Symbol Samples Inferred Environment QUARTZ

Channel TRAILER TRAILER PARK GULLY FELDSPAR Figure 39. Triangular diagram for samples collected in the tra ile r park gully site. and dam • 24.25,28,29,30 Symbol Samples Inferred Environment

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 83

percent. The composition is similar between the two layers except that the white bands have more feldspars, squashed rock fragments, and z ir

cons, while the yellow-brown bands contain more iron and muscovite. The

petrology is similar to the Fitzgerald Park sandstone ledges; therefore,

they have been classified as Eaton sandstones.

Minor textural differences from the Eaton sandstones have made i t

necessary to group these banded sandstones separately. Grain size is

between 0.304 mm to 0.375 mm; thus, they are sim ilar to the medium-

grained channel sandstones above the lag a t Face Brick Quarry and to the

medium-grained basal Eaton sandstones throughout Fitzgerald Park. The

sorting ranges from the moderately sorted (0.64 0) sample 30 to the

well-sorted (0.475 0) sample 28, although the three values are closest

to the moderately sorted boundary of 0.50 0. Roundness values o f 2.74p

to 2.54p for both quartz and feldspar are slightly less than the values

of the sandstones from the ledges. Feldspar a lte ratio n is minimal in

a ll three banded sandstones, comparable to the Eaton Sandstone values.

Packing values are between 1.68 to 1.96 with s lig h tly higher values

calculated for the white, more-friable layers. Similar values were

calculated fo r the upper units o f the sandstone ledges from Fitzgerald

Park, further justifying the populations shown on figure 35 and figure

39.

Group 2 consists of sample 27 taken across from the sewer works a t

the base o f a 40-foot (12 m) sandstone outcrop and sample 29 taken in

the gu lly across from the park entrance. Despite the d iffe re n t loca

tions, the sim ilarities are too close to overlook. Both samples of

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 84

group 2, shown on figure 39, have compositions lik e those of the sand

stone ledges shown on figure 35. The percentage of replacement iron

oxide is between 19 to 24 percent, within the range of the other Eaton

Sandstone members.

Textural differences seem to be the main reason for separating

these sandstones from the re st. The most important difference was found

in grain size. The values approach the coarse grain boundary with the

averages between 0.452 to 0.469 mm. The grains of group 2 were larger,

suggesting they were deposited farther upstream from the other sand

stones. Another important difference was discovered after the sorting

values were calculated. The sorting of group 2, unlike the other sand

stones, is between 0.34 to 0.36 0; therefore, they can be classified as

very well sorted. Roundness values are lik e those of the middle and top

units o f the Fitzgerald Park sandstones. The sandstones even share the

same reversing pattern, such that in sample 27, the quartz is rounder,

and in sample 29, the feldspar is rounder. Alteration is minimal, as it

is in the Eaton sandstones. The packing value is low and very close

(1.88 to 1.92) to the packing value in group 1.

Differences are s lig h t between sample 27 and sample 29. Sample 27

is unique as i t contains p yrite and because the basal contact is a gummy

shale. Neither the pyrite nor the shale are associated with sample 29,

which is compositionally and texturally uniform. In contrast, sample 27

shows vertical variability: the base of the sample is a pyrite layer

with floating sand grains; the grain contacts increase upward until they

eventually become grain supported; the top is marked by more pseudo-

matrix and small fragments o f p yrite in a grain supported sandstone.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 85

The pyrite is probably related to reducing conditions that existed

during the deposition of the dark gray shale. Zircon and mica are found

in trace quantities in sample 27.

Sample 24 cannot be placed in any of the previously mentioned

categories despite the compositional sim ilarity to the Eaton sandstones

of Fitzgerald Park. Sample 24 has a grain size sim ilar to the basal

sandstone in Fitzgerald Park, 0.302 mm, although the other textural

characteristics differ. Sorting, for instance, is only 0.95 0, ap

proaching poorly sorted while the Eaton sandstones are primarily well

sorted. Roundness is subangular lik e most o f the Eaton sandstones,

although the values, 2.62 for quartz and 2.58 for feldspar, are slightly

lower suggesting textural submaturity. Because of drastic sim ilarities

and differences, the author suggests th is sample is from a tra nsition al

zone between two facies. Feldspar a lte ra tio n and packing does not

change s ig n ific a n tly between sample 24 and the sandstone ledges from

Fitzgerald Park. Another sig n ific a n t characteristic of sample 24 is the

abundance o f plant fragments on the lower bounding surface.

Sample 26 also d iffe rs from the other sandstones despite s im ila ri

tie s to the composition o f the Eaton sandstones. The sandstone was

located above the dam s ite sequence on the Face Brick Quarry side of the

riv e r. The gradation is from a white sandstone to a mottled sandstone,

to a yellow-brown sandstone; the same pattern that is observed at the

location where samples 18, 19, and 20 were collected. A color banding

is also evident where the iron staining has permeated through the very

fin e sand grains. This very fine sandstone or coarse siltston e is

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 86

easily correlated to the sandstone above the coal in the old Clay Pro

ducts Quarry.

The grain size, 0.089 mm,'definitely falls into the very fine sand

scale. This sandstone has the finest grain size of any of the pre

viously described sandstones. The sorting value closely resembles the

values of group 2 and for this reason, it is also very well sorted.

Roundness values are again low with the closest parallel being sample

24. Once again, the values fo r the feldspar a lte ratio n and fo r packing

are w ithin the ranges obtained from the Eaton Sandstone columns.

Samples from American V itrifie d and Clay Products

The samples collected from American V itrifie d Quarry and from Clay

Products Quarry are plotted on figure 40. These samples are arkoses

lik e most o f the sandstones in Fitzgerald Park. Textural differences

set these sandstones (samples 14, 15, 17, AV, AVBS, CPAC) apart from the

others. One of the most striking differences is in grain size; these

samples fo r the most part are very fin e sandstones.

Samples AVBS and CPAC (Group 3) on figure 40 share almost identical

characteristics. The sequences from which the samples were removed have

been correlated by Kelly (1936) since both represent flood sands de

posited on bay fills . If composition alone was considered, sample AV

would also be included in group 3, but textural differences set them

apart. A ll o f these samples contain between 62 and 65 percent monocrys

talline quartz, 26 to 28 percent feldspars, and 9 to 15.5 percent rock

fragments. In addition, the accessory minerals muscovite and zircon

make up approximately 2 percent of the total composition.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 00 -vi ROCK ROCK FRAGMENTS Marsh or Levee Splay

14 14 c p a c CLAY PRODUCTS • O is Bay Symbol Symbol Samples Inferred Environment QUARTZ Crevasse Splay

a v b s , AMERICAN VITRIFIED a v • 17, Symbol Samples Inferred Environment FELDSPAR Figure 40. Triangular diagram fo r samples collected in American V itrifie d & Clay Products Quarry.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 88

A textural s im ila rity was noted between samples AVBS and CPAC. The

grain size ranges between 0.104 mm to 0.110 mm in the very fine sand

category. A slight contrast was spotted in sample AV; the grain size

(0.16 mm) is in the fine sand category instead. The sorting of group 3

(0.375 0 to 0.40 0) has been classified as well sorted. The sorting of

sample AV (0.50 0) is s lig h tly higher, on the boundary between the

moderately sorted and the well sorted categories. Similar roundness

values were also observed such that quartz with a 2.94 to 3.06 range is

more rounded than feldspar with a 2.78 to 2.94 range. The roundness

values calculated from sample AV also fa ll w ithin the ranges above. The

feldspar a lte ra tio n values are minimal fo r a ll three samples ranging

from 0.54 to 0.62. The packing is greatest in sample AV, but values for

a ll three range between 2.0 and 2.4.

Sample 17 shown on figure 40 also represents a very fin e sandstone

deposited during flood conditions. It lies upon the bay-fill sequence,

d ire c tly above the coal, observed at American V itrifie d Quarry. The

sandstone's composition, is lower in quartz, higher in feld

spar, and about the same percentage o f rock fragments as found in group

3. Plagioclase, microcline, and polycrystalline quartz appear in the

sample as accessory minerals. The composition of sample 17 is also

s ig n ific a n tly d iffe re n t from the make-up o f the Eaton sandstones and the

Saginaw splay sandstones.

Both textural s im ila ritie s and differences exist between sample 17

and group 3. The grain size (0.109 mm) is in the very fin e sand cate

gory like group 3. The sorting value (0.375 0) is categorized as well-

sorted, which is the same c la s s ific a tio n derived fo r group 3 sandstones.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 89

Roundness values (Q=2.7; F=2.54) are somewhat lower although they are

s t i l l cla ssifie d as subangular lik e group 3 sandstones. A lteration of

feldspar grains is 0.50; therefore, the difference between group 3

values is not important. Packing is s lig h tly lower than the values

calculated fo r group 3. Since the 1.8 value is lower, the porosity must

therefore be slightly higher.

The composition, texture, and overall appearance o f sample 15

appears quite different from the other samples plotted in figure 40.

This sample has been named the "banded siltsto n e " of the Clay Products

Quarry. I t is composed of interlaminated shales and coarse siltstones.

The laminations are almost uniform with white siltsto n e layers being

slightly thinner at the base and thicker at the top than the gray shale

layers. Some of the reddish-brown shale layers are probably the result

of iron staining.

Compositionally, the sample is a subarkose ( 077^20^3 ^ Respite amount o f s i l t and clay sized grains. Accessory minerals include musco

vite and pyrite. The dark gray foliated layers contain more pyrite,

indicating that the reducing conditions were more intense in this so-

called bay-fill mudstone. The white layers, on the other hand, contain

more quartz and muscovite suggesting more normal fluvial conditions. It

was also noticed that grains were larger in the light gray bands while

the dark gray bands contained smaller grains, more cement, and more

matrix. This banded appearance or textural layering could best be

explained as either coarse s ilt-s iz e d grains s p illin g over into fin e r

s ilt or clay sized floodplain deposits or as the encroachment of levees

into in te rd is trib u ta ry bays as suggested by E llio t (.1974).

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The overall appearance and textural characteristics set sample 15

apart from the other coarse siltstones and s ilty shales deposited under

sim ilar conditions. Together both layers y ie ld almost the smallest

average grain size of 0.08 mm. Sorting (0.40 0) is similar to samples

CPAC, AVBS, and 17 indicating sim ila r winnowing conditions. Roundness

values are also distinct, with 2.78 quartz values compared to 2.70

feldspar values. The roundness values are subangular, but they are

s u ffic ie n tly less than the values obtained from Eaton sandstones. The

alteration value of the coarse fraction in sample 15 is identical to

sample 17. The packing value is only 1.12, suggesting a higher poro

sity, but the addition of cement and/or matrix reduces the pre-existing

porosity.

The remaining sample 14 on the tria ngu lar diagram (figure 40) was

taken d ire c tly above the “banded s ilts to n e ." Sample 14 has been termed

a root-bearing siltstone and as a continuation of the bay-fill sequence,

it represents the upper part of this coarsening upward sequence. It

appears that marshy land plants flourished as evidenced by the abundance

of roots. This same development o f shallow rooted plants occurs on the

banks of levees, supporting the theory of the encroachment of levees

into the bay.

The composition of sample 14 is similar to the composition of

sample 15 except fo r the abundant root casts which have increased the

percentage of organics counted. Even though the minerals present are

almost identical, the percentages differ with sample 14 recording a

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. lit h ic arkose composition secondary mineralogy in

cludes chlorite and zircon in addition to the muscovite and pyrite found

in sample 15.

Texturally, the comparisons between sample 14 and the other samples

o f Clay Products Quarry and American V itrifie d Quarry are rare. Sample

14 has the smallest grain size recorded, only 0.056 mm. The sorting is

remarkably different; the value is 0.2 0. The presence of this very

well sorted layer in the bay-fill sequence is probably best explained by

the encroachment o f levees. Levees from modern flu v ia l models normally

contain grains of uniform size as well as abundant vegetation. Mean

roundness values o f 2.82 fo r quartz and 2.50 fo r feldspar f a ll w ithin

the subangular category. Feldspar alte ra tio n is minimal and comparable

to the other samples plotted on figure 40. The packing value (1.48) is

low, but the addition of cement and the fine-grained texture indicates

that the porosity is not that high.

Additional Samples from Face Brick Quarry

Additional samples (1, 2, 3, 6, 8, and 12) were collected from Face

Brick Quarry as shown in figure 36. S im ila ritie s between samples in

figure 36 were recognized: sample 12 with sample 6; sample 8 with the

crevasse splay sandstones; and sample 3 with the channel lag sample.

Similarities are found in compositions only, whereas differences pri

m arily occur in grain size, sorting, and roundness.

The petrographic analysis of sample 12 (Q57F28R15^ lndi cates a lith ic arkose composition. The quartz is primarily monocrystalline.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 92

The feldspar grains are untwinned, therefore the composition is d iffi

c u lt to determine. Accessory minerals include up to 6 percent musco

vite, 1 percent zircon, and a trace of chlorite.

The textural characteristics of sample 12 are as follows: grain

size is very fin e sand (0.106 mm) and compares well with samples CPAC

and AVBS; sorting is moderate (0.625 0); the roundness of quartz (2.62p)

and of feldspar (2 .54p) is subangular, unlike samples CPAC, AVBS and the

splay sandstones; the feldspar alteration falls within the unaltered

division like the other samples; and the packing indicates reduced

porosity, as do samples CPAC, AVBS and AV.

Compositionally, sample 6 plots as a feldspathic litharenite de

spite sim ilarities to sample 12. The accessory constituents, zircon,

muscovite, c h lo rite , and m icrocline, are a ll found in trace amounts.

Texturally, th is lit h ic sandstone has an average grain size of

0.196 mm, closely resembling the grain size of sample A-14. The sorting

value (0.54 0) is in the moderately sorted category like samples A-16

and AV. The mean roundness of sample 6 (2.82 fo r quartz and 2.58 fo r

feldspar) differs from sample 12 although both contain subangular

grains. An alteration value of 0.74 is slightly high but s till within

the 0 to 6.5 percent alteration. Packing is high at 3.0, but the splay

sandstones are more tig h tly packed. I t appears that the higher amount

o f rock fragments increases the packing and therefore reduces the pore

space.

The composition of sample 8 (068^12^18^ 15 ver^ S1'mi^ar t0 t *ie composition of sample A-14, one of the splay sandstones. The 68 percent

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 93 quartz is composed of both monocrystalline and polycrystalline varie

ties. The 12 percent feldspar is made up of untwinned feldspar, micro-

cline, perthitic textured feldspar, and even the high temperature vari

e ty, sanidine. Accessory minerals make up approximately 2 percent of

the total composition and consist of muscovite, biotite, and chlorite.

The splay sandstones also contain muscovite and chlorite, but samples of

biotite and sanidine were not found.

The texture o f sample 8 can be compared to the texture of sample 6.

The grain size is almost id e n tic a l, with both lit h ic sandstones having

averages of 0.195 mm. The sorting value (0.575 0) is greater than the

0.54 0 value of sample 6, but both samples are within the moderately

sorted category. Roundness values are slightly higher in sample 8

although i t appears that the ra tio between quartz and feldspar roundness

is almost the same when compared to roundness ratios in other samples.

In sample 8, quartz grains have values o f 2.98p and are more rounded

than feldspar grains that have values of 2.62p. The amount of feldspar

alte ra tio n (0.74) is the same fo r both sample 8 and sample 6. In con

trast, the packing value is significantly different, with sample 8

(2.52) having more porosity than sample 6 (3.0). Despite the textural

sim ilarities, these samples cannot be classified in the same group due

to discrepancies in the mineralogical compositions.

Sample 3 is a rooted siltstone or very fine sandstone with a com

position resembling the sandstone matrix o f the channel lag sample 13 or

o f sample 14 from Clay Products Quarry. The rooted siltsto n e has a

lith ic arkose composition (QyjFjgR^). The majority of the quartz is

monocrystalline, with undulose quartz being almost twice as abundant as

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common quartz. The feldspar is untwinned. The 4 percent accessory

minerals are primarily muscovite and chlorite.

Texturally, sample 3 does not resemble sample 14. The average

grain size (0.083 mm) is somewhat larger than the average grain size in

sample 14. Sorting (0.375 0) is not as good as sample 14, but is com

parable to the sorting of sample AVBS and sample 17. Roundness values

of 3.02 for quartz and of 2.86 for feldspar are very close to the

boundary between subrounded and subangular. The amount o f feldspar

alteration is once again less than 6.5 percent. Packing in sample 3 is

greater than the packing in sample 14. I t seems that the differences

between sample 3 and sample 14 outweigh the s im ila ritie s .

The composition of sample 1 (Q^yFgg^i) is closely related to sample

7, a reworked sandstone. Both subarkosic samples contain high percent

ages of quartz and very low percentages of rock fragments. The ex

tremely small percentage o f both rock fragments and mica to ta ls only 2

percent of the entire composition. The absence or limited presence of

these constituents suggests that reworking by marine processes has also

taken place in th is sample. In both of these reworked sandstones the

monocrystalline quartz dominates. It is likely that the reworking and

bioturbating broke down the rock fragments and the polycrystalline

quartz creating the small (0.029-0.067 mm), equant, monocrystalline

quartz grains. In addition to the previously mentioned minerals, zircon

and organics were found in trace amounts.

Textural s im ila ritie s were also found between sample 1 and sample

7. The grain size of each is approximately 0.115 mm and is in the very

fine sand-size category. The sorting values of each of these reworked

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 95 sandstones are in the well-sorted divisio n . Sample 1 (0.39 0) is better

sorted than sample 7 (0.425 0) although the difference is not large

enough to be significant. The amount of feldspar alteration is also

closely related, with both samples around the midpoint value for un

altered feldspar.

The textural differences between sample 1 and sample 7 are in sig

n ific a n t. I t seems that the roundness and packing o f sample 1 do not

correlate well with sample 7. The roundness values (quartz at 2.9 and

feldspar at 3.3) have reversed positions from those calculated in sample

7. The rho value of sample 1 is within the subrounded category while

sample 7 is in the subangular category. Packing values also indicate a

s lig h t discrepancy between sample 1 and sample 7. In the case of sample

1, the packing value (4.12) is higher than the value determined fo r

sample 7 (3.84). Since both samples have high packing values, one would

expect less porosity in the reworked and bioturbated samples.

I t is suggested herein th a t a sim ila r destructive process created

both reworked, quartz-rich sandstones. I t appears that the textural

differences lie primarily in the diagenetic history of each of these

samples, even though the amount of cement and o f pore space is approxi

mately the same. Sample 2 is composed of 52 percent quartz, 11 percent feldspar, and

37 percent rock fragments. The composition plots as a litharenite with

the rock fragments having the same squashed appearance as the other

lit h ic sandstones. The composition d iffe rs from the other lit h ic sand

stones since i t contains more than 3 times as many rock fragments as

compared to feldspar grains. When plotted on figure 36, it is almost

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 96 directly on the border between a litharenite and a feldspathic lith -

arenite. Mica is approximately 6 percent of the to ta l sample, which

fu rth e r ju s tifie s the comparison between sample 2 with the splay sands

examined by Alexander (1968). Polycrystalline quartz appears in trace

amounts which is what one would expect in a sample with s ilt-s iz e d

grains.

The textural s im ila ritie s are not as pronounced as the composi

tional sim ilarities. The textural characteristics set sample 2 apart

from the other samples collected. The average grain size (0.082 mm) is

in the very fine sand or coarse siltstone category. The largest grains

of sample 2 are firs t muscovite, then feldspar. The sample (0.475 0)

is well sorted, lik e most o f the fine-grained sandstones and coarse

siltstones already described. Roundness values are subangular, in

contrast to the subrounded values o f the crevasse splay sandstones.

Another interesting distinction is that the feldspar is more rounded

than the quartz, which is abnormal. Most of the feldspar grains are

unaltered. The packing value (1.08) sig n ifie s the grains are almost

floating in a secondary iron cement. After recalculating for the amount

of replacement, it was found that approximately 85 percent of the slide

was grains. This suggests a greater degree of packing, especially a fte r

considering the percentage o f "pseudomatrix" id e n tifie d .

The remaining samples (sample 9 and AL-1) are both biomicrites or '

wackestones i f one uses Dunham's (1962) c la s s ific a tio n . The point

counts conducted fo r these samples yielded at least 20 percent t e r r i

genous grains. The terrigenous grains were id e n tifie d and measured to

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 97

determine the kind of marine environment in which they were deposited.

Muscovite abundance was also determined to position the environment with

regard to the mouth of the delta or the coastal shoreline. The lime

stone was examined further to identify the skeletal grains and the

groundmass. The skeletal grains are primarily brachiopod and crinoid

fragments although the d iv e rs ity o f th is environment has been discussed

in the section on marine facies. The groundmass under the 50 power

objective appears pelletal instead of the collective term micrite.

Chemical Consituents

The cementation process involves four cements. The amount of each

cement present and the degree o f compaction varies between samples. The

firs t authigenic mineral was the growth of chlorite rims. The chlorite

rim cements are oriented tangentially around the framework grains,

indicating they were probably the earliest cement. In unpolarized light

the rims are id e n tifie d as green pleiochroic bands, whereas, crossed

nichols reveal only a weakly birefringent rim surrounding the sand

grains. The chlorite rim cements are present in almost every sample

examined, although they are d iffic u lt to distinguish in samples con

taining large amounts of matrix and "pseudomatrix."

An iron cement also forms rims around the framework grains. The

samples o f the Eaton Sandstone collected from Fitzgerald Park and Oak

Park, and the channel sandstones taken from Face Brick Quarry show the

most complete rims. The iron cement is a major consitutent in the

banded sandstones found along Sandstone Creek and in the g u lly across

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 98

from the Fitzgerald Park entrance. The iron-stained, more indurated

layer, yellow-brown in color, exhibits the greatest number of iron rims.

Kelly (1936) hypothesized a syngenetic origin for both the ferruginous

rims and the color banding.

The next most abundant cement is a siliceous cement which sometimes

occurs in the form of quartz overgrowths. The siliceous cement follows

the formation of the ferruginous rims, thus, partially fillin g the

remaining pore space. In the more tig h tly packed samples, the s ilic a

cementation has been more complete. The quartz overgrowths are more

abundant in the coarse- to medium-grained sandstones as compared to the

samples containing finer grains and more matrix.

Land and Dutton (1978) recognized sim ilar cements in a Pennsyl

vanian deltaic sandstone from the Strawn Series, north-central Texas.

Their sequence of authigenic minerals is as follows: (1) growth o f a

chlorite rim around quartz grains, (2) cementation by the average of 11

percent syntaxial quartz overgrowths, (3) cementation by calcite, (4)

dissolution of calcite cement, feldspar grains, and rock fragments, and

(5) cementation by Fe calcite, anerite, and kaolinite.

A carbonate cement was also found in the Grand Ledge samples. The

carbonate occurs prim arily as patches which surround pre-existing ce

ments and framework grains. The patches were found in the samples o f

the rooted siltston e collected from Face Brick Quarry. The carbonate

patches are larger and more irre g u la rly shaped than the framework

grains; fo r th is reason, they have been termed carbonate replacement.

It is possible that the carbonate was actually leached out of the adja

cent or overlying biomicrite and then seeped into the rooted siltstone.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 99

The most prominent epigenetic cement is the abundant replacement

iron oxide which appears in almost every Grand Ledge sample but not in

the samples o f the Strawn Series. The iron oxide cement also appears in

large patches engulfing framework grains, accessory minerals, other

cements, and even the matrix o f some samples. The replacement iron

oxide is abundant in the Fitzgerald Park Sandstone and in the channel

sandstones from Face Brick Quarry. The Saginaw sandstones, siltstones,

and shales have only small amounts of this iron oxide present.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SUBSURFACE DATA

Two attempts to explain Pennsylvanian subsurface data were under

taken by Potter and Siever (1956) in the Illin o is Basin and by Shideler

(1963) in the Michigan Basin (figure 41). Shideler's (1963) work is the

most significant since it deals with the lower, middle, and upper Penn

sylvanian sediments.

Shideler's three divisions fo r the Pennsylvanian sediments o f the

Michigan Basin, Interval "A," Interval "B," and Interval "C," are shown

in figure 3. Interval "A" (figure 30) represents the Morrowan or oldest

Pennsylvanian u n it. In outcrop, th is interval corresponds to the Parma

Sandstone and the Saginaw units beneath the oldest coal horizon. In te r

val "B" (figure 31) represents Lampasan or Atokan sediments. I t in

cludes all strata above the roof shale of the Saginaw coal to just

beneath the Verne Limestone member. The youngest Pennsylvanian sedi

ments are represented by Interval "C" (figure 32). Shideler includes

the Eaton Sandstone assemblage, sta rtin g with the channel lag, in the

Allegheny or Desmoinesian Division.

According to figure 30, the thickest sand accumulations are located

in pre-Pennsylvanian valleys, while the thinnest sand accumulated on

topographic highs. Shideler's 200 foot (59.9 m) sandstone isolith line

delineates a north-south trending linear sand belt coinciding with the

axis of the greatest pre-Pennsylvanian depression. Also observed were

100

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 101

EATON_ IJNSHAMj /LAKE\ 'ST.CLAIR N-

MILES

Figure 41. The d istrib u tio n o f subsurface data in the Grand Ledge vicinity (Shideler, 1963).

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 102

elongate, narrow sand belts which extend from the major linea r trend.

These sand bodies are generally aligned with pre-Pennsylvanian valleys,

and th e ir elongate and branch-like appearance resembles modern examples

o f d is trib u ta rie s developing from a major flu v ia l channel.

Potter and Siever (1956) noted sim ilar sand belts which parallel

entrenched valleys o f the pre-Pennsylvanian surface. Sim ilar correla

tions have been made in the trend of sediment transport from Potter and

Siever's (1956) paleocurrent data which also revealed northeast to

southwest trending channels. The dendritic pattern o f the narrow sand

belts was id e n tifie d in subsurface maps from both the Illin o is Basin and

the Michigan Basin. The subsurface correlation between these two basins

is very important since the Parma Sandstone is not found in outcrop

exposures in the Grand Ledge v ic in ity . The author has decided to use

the rock description of Kelly (1936) and the subsurface data of Shideler

(1963) to define the oldest Pennsylvanian environment as a flu v ia l chan

nel with several distributaries branching from it. Some of the Saginaw

units are also found in this interval and distribution of the shales,

siltstones, and coals indicate the adjoining bay, marsh, and swamp

environments.

Shideler (1963) suggested that his intricate facies relationships

of varicolored shales, subgraywacke sandstones, terrestrial biota, and

the lineation of sand bodies are characteristic of stream alluviation in

a deltaic complex. The discontinuous marl and coal deposits were prob

ably the result of deltaic progradation across the basin. This allowed

the formation o f marginal fresh water lakes and swamps.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 103

Interval "B" (figure 31) illustrates the dispersal pattern of

elongate sand belts which have the geometric configuration of meandering

channel deposits. Clays and s ilt s are located along and in-between the

sand belts indicating that the energy was much lower in the interchannel

areas. According to Shideler (1963), the dark shale and the sand lith -

ologies are closely associated.

The relationship between the sandstone and shale have been in te r

preted as an a llu via l plain environment interrupted by minor marine

advances. The te rre s tria l deposits are elongate, le n tic u la r sand bodies

with abundant cut and f i l l structures. Meanwhile, the b rie f marine

episodes deposited the restricted, Lingula-bearing shales. The exten

sive coal deposits were also the result of marine transgressions which

probably created the swamp conditions.

The splay sandstones could be included in this interval, although

Shideler did not make specific reference to their association with the

other Saginaw sediments. Meandering channel deposits were found in the

subsurface indicating a flu v ia l environment. The outcrop exposures do

not show the specific interfingering of the channel and bay environ

ments, although splay sandstones interrupt the normal shale deposition

in outcrops from Face Brick Quarry and American V itrified Quarry.

Shideler's only mention of the splay sandstones is in his description of

the source area. He states that the micaceous and feldspathic nature of

the sandstones is indicative of extensively decomposed firs t-c y c le

sediments possibly derived under humid conditions from crysta llin e land

masses of the Laurentian Shield. The author's alternative is that these

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sandstones are a combination of flu v ia l sands and levee, bay, or over

bank deposits. Flooding caused breaches in the natural levee sediments

and the mixed sediment is carried onto the bay or overbank deposits.

In Shideler's Desmoinesian isolith map (figure 32), the orientation

and geometric configuration of the two major sand belts are highly

suggestive o f channel sand deposits resulting from a stream system

moving slowly in a westerly direction.

Interval "C" has been interpreted as an a llu v ia l plain assemblage

with minor contributions of shallow neritic deposits. The pattern of

the fluvial sediments specifies a relatively broad alluvial plain con

taining rapidly aggrading streams. The aggrading nature o f the streams

combined with cross-bedded sedimentary structures indicate channel f i l l

deposits. It is the feeling of the author that with detailed descrip

tions of both sedimentary structures and the corresponding grain size,

tha t the generalized environment could be divided into subenvironments.

Since interval "C" corresponds to the Grand River Formation, i t seems

more appropriate to use the outcrop exposures found throughout the Grand

Ledge area. I f Shideler had examined the Eaton Sandstone deposits, he

probably would have classified the rocks of Interval "C" as point bar

deposits based on differences in grain size and sedimentary structures

(Appendix I I ) .

Other available information regarding the subsurface nature of the

Pennsylvanian sediments in Michigan was also studied. This included

some Lansing subsurface data from Davis and Bredwell (unpublished).

Since the wells are simply divided into sandstone, s ilts to n e , and shale,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. it is d ifficu lt to interpret the environment of deposition unless one

has examined the core samples. I t is possible though, to observe the

lith o lo g ie s in te rfin g e rin g , which suggests that they are contempor

aneous. The cyclic nature of the sediments, as well as the interfin

gering of lith o lo g ie s , suggest e ith er a flu v ia l or a d e ltaic environment

of deposition.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DEPOSITIONAL MODEL AND THE HISTORY OF SEDIMENTATION

This author is proposing the fluvial deltaic model shown on the

facies map (figure 42). The depositional model consists of a construc

tive phase and a destructive phase. The terrestrial and transitional

facies are components o f the constructive phase, while the destructive

phase is prim arily made up of the marine facies.

Delta Plain or Channel Margin Facies

Correlation between measured sections at Clay Products Quarry and

American V itrified Quarry, along with topographic elevations indicate

that the area was in itia lly a large deltaic plain during Saginaw time.

The delta plain can be divided into bay, marsh, and swamp subenviron

ments, all part of the constructive delta phase.

Marsh Subenvironment

The exposed base of the Saginaw Formation is a fine-grained,

quartzose sandstone which contains shale laminae or shale pebbles (Davis

and Bredwell, 1975). A plant-bearing gray siltston e overlies the sand

stone. The plants were probably transported from swamp or marsh condi

tions into a bay environment as suggested by th e ir fragmented appear

ance. Increased flu v ia l sedimentation followed, with the deposition of

alternating layers of shale and coarse siltstone. According to Coleman

106

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SUBFACIES SUBFACIES crevasse splay carbonatemounds MARINE FACIES CHANNEL MARGIN A\ BAY SUBFACIES BAY CHANNEL SUBFACIES QUARRIES

_ _ \ Lawson Quarry

W mJm JZ ^ •T *1

o o©

LAWSON ROAD

and Gagliano (1965), modern marsh deposits contain an abundance of plant

life in fresh to brackish water. It is also common for the organic

sedimentation to be interrupted by the introduction of fine elastics

during flood conditions. The th in laminae o f sandstones and si Itstones

probably represent overbank deposits.

Bay Subenvironment

The next unit is a soft, blue-gray Lingula-bearing shale. This

u n it suggests a minor marine advance providing a suitable brackish

environment for the Lingula and foraminifera. The restricted portion of

the bay did not last long because of the influx of terrestrial sedi

ments, a plant bearing shale followed by a "banded siltstone."

Levee Subenvironment

The very fin e sandstone laminae represent the fin e elastics de

posited in marshy shales. The flooding became more frequent as sug

gested by th icke r and coarse-grained sandstone laminae higher in the

section. F in a lly , the very fine sandstone became more abundant than the

shale. The composition o f the sandstone changed s lig h tly with the

occurrence of micas and the introduction of root casts. Root penetra

tions and iron concretions are abundant in th is zone. In the modern

Mississippi Delta, Coleman (1964) described natural levee deposits

containing similar features: wavy laminations from plant roots and

small fe rric nodules produced by oxidation. I f these are actually

subaerial levee deposits, then the levees are probably encroaching into

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 109 the bay. E llio tt (1974) stated that the encroachment of the levees into

the bay produced a coarsening upward sequence of interbedded sands and

muds with increasing thickness of the coarser beds upward.

Abandoned Channel Subenvironment

The underclay probably represents a period of channel migration,

with the fin e r sediment overlying the coarser sediments. Shideler

(1963) described the underclay as a white to light gray, structureless,

sandy clay which contains siderite concretions of variable size and

shape. The light color and lack of structures suggest that the depo

sition was very rapid, thus vegetation could not keep pace. The iron

concretions probably formed due to ponded water percolating through the

pores o f th is sandy shale.

I f the channel migrated further away, the amount of sediment depo

sited in the Clay Products Quarry area would be decreased. This event

could explain how the dense vegetation flourished, thus forming the

subbituminous grade coal. In Lawson Quarry, the coal seams appear more

shalely which is probably due to the in flu x of fin e sediment during

times of floods. Beerbower (1961), in his study of the Dunkard Group,

found clay partings and laminated clay shale between beds o f coal which

he attributed to an in flu x o f c la s tic sediments in a marshy or anaerobic

environment.

Crevasse Splay Subenvironment

This sequence of events was followed by crevassing of the new

natural levees. The crevassing is represented by about ten feet (3.0 m)

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of very fin e grained white sandstone which contains thin shale lami

nations. The sequence (figures 5 and 10) is recorded in the deposits

above the coal at American V itrifie d Quarry. Also important in th is

area is the lateral gradation from one to two feet (0.3 to 0.6 m) of

fine-grained sandstones which interfingers with a gray siltsto n e and

finally into a gray shale. This lateral change of lithology indicates

the proximity of these deposits with regard to the distributary channel.

The crevasse splay sandstones, which p lo t as feldspathic lith a re -

nites, also occur at Face Brick Quarry although the units are slightly

thicker. They spill into a silty shale which probably represents a bay

environment. The s ilty shale above the quartz-poor, fine-grained sand

stone, contains a greater number of fragmented plant fo s s ils . The plant

remains were probably carried by currents into this environment from the

adjoining marsh environment.

Destructive Delta Phase

The remaining units o f the Saginaw Formation, the reworked sand

stone, the black calcareous shale and the biomicrite, are parts of the

destructive delta phase. More specifically, they represent the advance

of the marine facies.

Reworked Sandstone

The reworked sandstone is the lowermost unit of the destructive

delta phase. The sandstone is rich in quartz, low in rock fragments,

and has been extensively burrowed. This bioturbated subarkose suggests

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delta lobe abandonment and landward reworking by marine processes o f the

delta front sands over a subsiding delta plain.

Black Calcareous Shale and Biomicrite

Continued subsidence was apparently responsible fo r the deposition

of thin, black, marine shales and overlying biomicrites. These depo

s its , lik e the carbonaceous limestones of the Dunkard Group (Beerbower,

1961), are typically thin, irregular, and in many places nodular. Since

they are commonly associated with carbonaceous shales, the biomicrite

with a diverse marine fauna and up to 20 percent terrigenous clastic

detritus was probably deposited in a brackish lagoon or a semi

restricted bay. As previously discussed, the micrites probably repre

sent carbonate mounds as suggested by th e ir lim ited extent. Above the

micrite is the "banded siltstone" previously discussed.

Meandering Channel Facies

Channel Lag Deposits

S hifting o f the meandering channel or channel rerouting through

weak points in the levee are suggested for the channel lag deposits. It

appears that as the riv e r shifted and as the energy was increased, i t

caused the slumping o f the cut bank slopes in to the riv e r's channel.

The transported shale, limestone, and coal clasts were deposited farther

downstream where finer-grained sands were being deposited. The flood

water then ripped up consolidated sediments from the adjacent delta

plain and deposited them as the competancy of the stream was decreased.

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The resultant deposit consists of shale clasts, discontinuous coal

seams, coal chunks, limestone clasts, and ironstone nodules enclosed in

a fin e - to medium-grained quartzose sandstone.

Point Bar Deposits

Arkosic or subarkosic sandstones overlie the channel lag deposits.

These Eaton sandstones have two divisions—the lower, coarse- to medium-

grained massive u n it and the upper, fin e - to medium-grained bedded u n it.

The decrease in flow regime coupled with a fin in g upward sequence (Ap

pendix I I ) suggests that the Eaton sandstones are point bar deposits.

A correlation can be made between the Eaton sandstones and the

Pennsylvanian flu v ia l sands from the Missourian o f central Oklahoma.

Visher's (1965) study o f the Missourian flu v ia l sandstones revealed both

textural and sedimentological differences between the sandstones at the

base o f the sequence and those at the top o f the sequence. He noted

that the finer and more poorly sorted samples were found near the top of

the sequence, which closely parallels the trend found in the measured

sections taken in Fitzgerald Park. The sedimentary structures o f these

Pennsylvanian sandstones also share s im ila ritie s ; the Missourian dis

plays primarily large trough cross-beds in the lower zone grading upward

into current laminated sands; while the Eaton Sandstone exhibits massive

bedding or large trough cross-bedding at the base followed by planar to

smaller trough cross-bedding and fina lly rippled bedding at the top.

Visher (1965) proposed that the grain size decrease and the decrease in

flow regimes would re fle c t both decreasing depth of water and a la te ra l

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 113

shift of the depositional site away from the main axis of the stream as

the meander loop extended.

Schumm (1963) discovered that the nature of sediment accretion

within fluvial channels was dependent upon the size and the quantity of

sediment in transport. Therefore large volumes o f coarse d e tritu s are

ty p ic a lly transported in broad channels with low f la t point bars; con

versely, fine d e tritus is ty p ic a lly transported in deep narrow channels

with steep point bar slopes. The measured columns of the Eaton Sand

stone are prim arily medium sand grains; therefore, the sediment was

transported in re la tiv e ly broad channels which become narrower with time

as shown as the fin in g upward sequence. The point bars themselves are

generally low and fla t at the base of the column while they become

steeper and of moderate height, about 25 to 40 feet (7.5 to 12.0 m),

after reaching the top.

The paleocurrent data (Appendix I or figure 28) obtained throughout

Fitzgerald Park is yet another tool to identify the environment of

deposition. Under the section on Paleocurrent Analysis, i t was men

tioned that paleocurrent trends change from sector to sector and from

division to division, indicating some migration. The change in flow

direction from the base of the sections to the top and the associated

fining upward sequence are typical of laterally migrating channel and

point bar deposits (Visher, 1965).

Basically, the typical sequence at Grand Ledge suggests a con

structive phase in which the bay, marsh, swamp, and splay sediments were

deposited. This was followed by a destructive phase where subsidence

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. and marine transgression has deposited the reworked quartz-rich sand

stone, the calcareous black shale, and the quartz-bearing biomicrite.

The la st episode started with the advancing of d istrib u ta ry channels

suggesting the constructive phase was once again dominant. The forma

tion of the migrating point bars was also a part of the constructive

phase. Continuing upward through the point bar sequences, the energy

and the depth o f the water have decreased, suggesting that the destruc

tiv e phase had taken over again.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CONCLUSIONS

The petrographical and sedimentological characteristics identified

in the Saginaw and Grand River Formations, o f Middle and Upper Pennsyl

vanian age can be closely compared to a fluvial/deltaic environment of

deposition. The depositional model proposed herein is based on paleo

current analysis, the petrology and petrography of the typical samples,

the subsurface data which allows interpretation of facies geometry, and

ve rtica l sequences of sedimentation. The proposed model is based on

evidence suggesting that deltaic processes dominated the pre-existing

fluvial and coastal surroundings.

Sediments from the Saginaw and Grand River Formations (figure 43)

have been grouped into three major facies: the marine facies, the

tra n sitio n a l facies, and the te rre s tria l facies. The marine facies

consists of ( 1) bioturbated, quartz-rich, delta fro n t sandstone, ( 2 )

black, calcareous, interdistributary bay shales, and (3) black, quartz-

bearing, carbonate mud mound biomicrites. The transitional facies is

comprised o f (1) Lingula-bearing, re stricted in te rd is trib u ta ry bay

shales, ( 2 ) laminated to flaser bedded, rooted, marsh shales and s ilt-

stones, and (3) subbituminous, swamp coals. These components o f the

transitional facies represent portions of the smaller bay subfacies

which is locally interrupted by lens-shaped, quartz-poor, fine-grained,

crevasse splay sandstones of the adjoining channel margin subfacies.

The te rre s tria l facies or channel subenvironment is represented by

coarse, poorly sorted conglomeratic sandstones; by medium grained,

115

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 116

FACE BRICK FITZGERALD PARK

• * • • • • • liiiil • » • • • • • * • • «••••< • I ......

• # # . _

rr.’ w ‘♦w.'aj. w ; -ttww'w uc* mwj u0

■A-«

Figure 43. The type measured sections fo r Face Brick, Clay Products Quarry and Fitzgerald Park.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 117

moderately sorted, quartzose sandstones; and by medium grained, moder

ate ly- and well-sorted, cross-bedded sandstones. These units are in te r

preted as channel lag, channel f i l l , and point bar subenvironments,

respectively.

The channel f i l l and point bar sandstones exhibit erosional bases,

occasional channel lag deposits, an upward fining of grain size, and a

decreasing scale of cross-stratification. Over 1,200 paleocurrent

measurements were taken from these sedimentary structures. Plots o f the

averaged vectors (figure 28) indicate a unimodal, highly variant, north

ward trending paleocurrent pattern that deviates from the regional

(Potter and Si ever, 1956) paleoslope.

The petrology and petrography of the representative sandstones

indicate sediments were derived from a low-grade metamorphic and plu-

tonic source te rra in . The composition o f the Eaton sandstones, speci

fica lly the medium- to fine-grained sandstones interpreted as point

bars, is arkosic (Qg2F33R5^ to subarkosic (Qqif i 4R5^• The fine-grained,

bioturbated sandstones have higher values of quartz ( 535^15) placing

them in the subarkosic category. In contrast, the fine-grained sand

stones with abundant rock fragments represent crevasse splay sandstones

defined as feldspathic litharenites ■ ('QggF^Rgj).

Textural characteristics were also examined to determine specific

variations between the sandstones. The sandstones interpreted as chan

nel f i l l and point bar sandstones were id e n tifie d by the fin in g upward

trend, the increasing sorting values (almost all belonging to the well-

sorted division), and the subangular roundness values.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 118

Composition and textural characteristics have been determined fo r

each of the samples to decide the environment of deposition. The petro-

graphic study provided the information needed to construct the deposi-

tional environments fo r the point bar sandstones, the marine sandstones,

and the crevasse splay sandstones. This petrographic work involved the

relationship between composition, grain size, sorting, roundness, and

packing.

The subsurface data reveals the geometry o f the sandstone bodies.

The basal Pennsylvanian units are prim arily elongate, branch-like sand

belts which resemble d is trib u ta rie s extending from a major channelway.

Shales, siltston es, and coals of the Saginaw Formation are found between

and adjacent to linear sand belts; they probably represent bay, marsh,

and swamp subenvironments.

The remaining Saginaw units belong the the Atokan Series (figure

31). The dispersal pattern results in siltstones and shales between

elongate sand belts. The geometric configuration of the sand belts

parallels modern patterns of meandering channels. The siltstones and

shales would represent sediments found in a llu v ia l plains. Minor marine

advances then took place depositing the Lingula-bearing shale and the

swamp coals, thereby in te rru p tin g the deposition of sandstone.

The youngest Pennsylvanian un its, the Desmoinesian Series (figure

32), are represented by sandstones of the Grand River Formation. Shi -

deler recognized two well-defined sand belts and he suggested that they

were channel f i l l deposits in a stream system which flowed to the west.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 119 More specifically, the pattern of fluvial sediments indicates a rela

tiv e ly broad a llu v ia l plain with rapidly aggrading streams. The aggrad

ing process is even more noticeable in the outcrop exposures that the

author has defined as point bar deposits. The Eaton Sandstone expo

sures, with their upward fining in grain size and their upward decrease

in sedimentary structures, in conjunction with Shideler's (1965) sub

surface work, suggests tha t these sandstones are channel f i l l or point

bar deposits.

The depositional history suggests periods of both constructive and

destructive deltaic phases. The typical strati graphic sequence (figure

43) at Grand Ledge starts with sediments deposited in bay, marsh, swamp,

and crevasse splay subenvironments. A destructive phase causing re

working follow s. During th is phase, marine processes produced the

reworked, quartz-rich sandstone, the calcareous, black shale, and the

quartz-bearing biom icrite. The remaining episode is constructive,

starting with flooding which causes d istrib u ta ry channels to cut through

delta plain deposits. Continuation of the constructive phase leads to

the deposition of migrating point bars. The upward decrease of both

grains size and sedimentary structures indicates a decline in the con

structive deltaic forces.

I t is therefore suggested tha t the sedimentary deposits of the

Pennsylvanian Period in and around the Grand Ledge area of south-central

Michigan were formed in a deltaic depositional setting.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SITE 20 SITE 21

0v = 77.7° 0v= 359.3° L = 20.2 L = 59 51 obs., NS 20obs.,S 0v = 309.9° 0v= 285.0° L =39.0 .S' L = 86 38 obs.,S 03 obs., S

23SIT SITE 24

0v=3l2 9° 0vs 19.2° L = 4 7.4 L= 26.9 52obs., S 09obs.,NS 0v = 3l2.7° 0v = 3OO.4° L = 57.1 L = 37.5 60obs.,S IOobs.,NS

APPENDIX I

0 **72.6° 0v= 61.9° L = 35.3 s * L*3I.2 l9obs.,S 101 obs., S 0v= 359.3° 0v= 32 9 .3 ° L - 59 y * L *34.9 20obs.,S 34 obs., S 0v= 285.0° 0v = 22.0° L = 86 L * 10.5 03 obs., S 35 obs.,NS

SITE 24

LEGEND

Top unit of the Eaton Sandstone

y S * Middle unit of the Eaton Sandstone 0v =166.1 ° L = 33.5 02 obs., NS s * Basal unit of the Eaton Sandstone 0v = l9.2° L = 26.9 09obs.,NS §w=300.4° L = 37.5 IOobs.,NS Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

Plant fragments None Diverse marine fauna Root casts brachs. and crlnoids abundant Llngula, forams and a low salinity pelecypod Root casts Plant fragments including wood

Highly bioturbated no structures None Horizontal bedding Root structures finally small scale rip pled bedding flazer bedded Fissile shale Root structures Structureless to horl- Plant fragments due to shale layers Small scale ripples Plant fragments zontally bedded and No bedding SEDIMENTARY STRUCTURES FOSSILS

FLOW TYPE OF High marine energy Low to moderate No energy High energy (river) to deposit but sig nifies lower energy High energy but part regime marine energy regime Middle lowerto lower lower flow regime Med. scaletroughs planar to small scale Low energy bedding wood Plant fragments including trough cross beds and Low energy and farther from channel of lower lower flow Lower upper to upper lower flow Massive to large scaletrough cross Plant fragmentsincluding wood Very low energy (high energy)

Fines upward None None slightly slightly None Fines upward Fines upward slightly Coarsens upward Coarsens upward Poor gradation Upper (low regime Coarsens upward Fines upward GRADATION TEXTURAL

SIZE AVERAGE GRAIN None Fine sand Medium to coarse silt Fine sand (.074 to (.074 to .191mm) .376mm) Medium to fine size Very fine sand 0.54 to076 .191mm) ium sand size matrix Medium sand (.341- sand (,300mm to .140mm) Clay to medium silt Clay size .076 to .410mm large rip up clasts In med (Average .233mm) APPENDIX nAPPENDIX OFSUMMARY INFERRED ENVIRONMENTS

Feldspathlc Uthare- BlackCalcareous Biomicrite nite (More Mica) Shale and Black Feldspathlc Uthare- Coal Lithic Arkose to Feldspar Lltharenlte nlte(More Mica) (More Mica) Soft Blue Gray Shale Silty Shale Arkose

Bay Slltstone B. Lagoonal MARINE ENVIRONMENT LEVEE ENVIRONMENT B. Crevasse Splay Shallow Marine A. Shoreline or BAY FILL BIVIRONMENT D. Swamp A. Natural Levee B. Restricted Bay ENVIRONMENTS & SUBENVIRONMENTS & PETROLOGY PETROLOGY B. Channel Fill C. Point Bars Subarkose A. Interdistributary Subarkose to Arkose C. Marsh Silty Shale and CHANNEL ENVIRONMENT A. Channel Lag Subarkose to Lithic

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SELECTED BIBLIOGRAPHY

Alexander, M. E., 1968, Biostratigraphy o f the Saginaw Formation near Grand Ledge, Michigan, Western Michigan University Earth Science independent research project.

Allen, J. R. L., 1966, On bedforms and paleocurrents: Sedimentology, v. 6, p. 153-161.

______,1970, Sediments o f the Modern Niger Delta: A summary and review, ijn Morgan, J. P., ed., Deltaic sedimentation modern and ancient; Soc. Econ. Paleo. and M ineral., Spec. Pub. No. 15, p. 138- 151.

Arnold, C. A., 1949, Fossil flo ra o f the Michigan coal basin: Michigan Univ. Mus. Paleontology, Contr., v. 7, no. 9, p. 131-269.

Atherton, E., e t al_., 1960, D iffe re n tia tio n o f Caseyvilie (Pennsylva nian) and Chester (Mississippian) sediments in the Illin o is Basin: Illin o is Geo. Survey. Circ. no. 306, 36 p.

Barton, D. C., 1930, Deltaic coastal plain of southeast Texas: Geol. Soc. Amer. B u ll., v. 41, p. 359-382.

Bates, R. L ., 1938, Occurrence and o rig in o f certain lim onite concre tions: Jour. Sed. Pet., v. 8, p. 91-99.

Baganz, B. P., Horne, J. E., and Ferm, J. C., 1975, Carboniferous and Recent Mississippi lower delta plains: a comparison: Gulf Coast Assoc, of Geol. Soc. Trans., v. 25, p. 183-191.

Beerbower, J. R., 1961, Origin of cyclothems of the Dunkard Group (Upper Pennsylvanian-Lower Permian) in Pennsylvania, W. V irg in ia , and Ohio: Geol. Soc. Amer. B u ll., v. 72, p. 1029-1050.

Bernard, H. A., Major, C. F., Jr., Parrott, B. S., and LeBlanc, R. J., J r., 1959, The Galveston b a rrie r island and environments: Gulf Coast Assoc. Geol. Soc. Trans., v. 9, p. 221-224.

Bernard, H. A., LeBlanc, R. J., Sr., Major, C. F., Jr., and Parrott, B. S., 1970, Recent sediments of southeast Texas: a fie ld guide to the Brazos alluvial and deltaic plains and the Galveston Barrier Island complex: Texas Univ. Econ. Geology Guidebook, no. 11, 98 p.

Bredwell, H. D., 1974, Carboniferous depositional environments of Grand Ledge, Michigan, Michigan Earth S cientist, v. 10, no. 3.

122

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Bredwell, H. D., and Davis, M. W., 1973, A happening on the ledges; a fie ld tr ip sponsored by the National Association of Geology Teach ers, Parts A and B.

Brown, L. F., 1969a, Geometry and d istrib u tio n of flu v ia l and deltaic sandstones (Pennsylvanian and Permian) North Central Texas, Gulf Coast Assoc, of Geol. Soc. Trans., v. 19, p. 23-48.

_____ , 1969b, Northern Texas (eastern shelf) Pennsylvanian delta systems, j[n Delta Systems in Exploration fo r Oil and Gas: Uni ve rsity of Texas Bur. Econ. Geology, p. 42-53.

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______> 1976, Verbal communication.

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Englund, K. J ., 1974, Sandstone d istrib u tio n patterns in the Pocahontas Formation o f southwest V irginia and southern West V irg in ia , Geol. Soc. Amer. Spec. Paper 148, p. 31-45.

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Ethridge, R. G., Fraunfelter, G., Utgaard, J., eds., 1973, Depositional environments of selected Lower Pennsylvanian and Upper Mississip- pian sequences of southern Illin o is: Guidebook for Thirty-seventh Annual T ri-sta te Field Conference, Department o f Geology, Southern Illin o is University, Carbondale, 158 p.

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Frazier, D. E., 1967, Recent deltaic deposits of the Mississippi River: th e ir development and chronology: Gulf Coast Assoc. Geol. Soc. Trans., v. 17, p. 287-311.

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Land, L. S. and Dutton, S. P., 1978, Cementation of a Pennsylvanian d e lta ic sandstone: Isotopic data, Jour, o f Sed. P e tro l., v. 48, no. 4, p. 1167-1176.

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Pelletier, B. R., 1958, Pocono paleocurrents in Pennsylvania and Mary land: Geol. Soc. Amer. B u ll., v. 69, p. 1033-1064.

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Reineck, H. E. and Singh, I. B., 1973, Depositional sedimentary environ ments: Springer-Veriag, New York, 439 p. (Fluvial Environment, p. 225-263; Deltaic Environment, p. 264-279; and The Coast, p. 280- 305).

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