76-9949 CHAPEL, James David, 1948- PETROLOGY AND DEPOSITIONAL HISTORY OF DEVONIAN CARBONATES IN OHIO. The Ohio State University, Ph.D., 1975 Geology

Xerox University Microfilms,Ann Arbor, Michigan 48106 PETROLOGY AND EEPOSITIONAL HISTORY

OF. DEVONIAN CARBONATES IN OHIO

DISSERTATION

Presented in Partial Fulfillment of the Requirements for

the Degree Doctor of Philosophy in the Graduate

School of The Chio State University

bY Janes David Chapel, B.A,

* * * * *

The Ohio State University

Reading Coirmittee: Approved Ey

Professor Charles H. Summerson Professor Kenneth 0. Stanley //?//? Professor James W. Collinson v Adviser Department of Geology and Mineralogy ACKNOWIEDGMENTS

ivy deepest thanks go to Dr. C. H. Summerson for his guidance and encouragement during the course of the research and for his critical reading of several drafts of the manuscript. I also wish to thank

Dr. J. W. Collinson and Dr. K. 0. Stanley for their discussion and criticism of material presented in this dissertation. Special thanks go to Mr. A. Janssens of the Ohio Division of Geological Survey who discussed stratigraphic problems with the author on several occasions and provided access to unpublished stratigraphic data.

I am especially indebted to the owners and officials of numerous stone companies who permitted me to study the sections in their quarries and who, in some cases, provided access to drill cores. In this regard

\ special thanks are. extended to Mr. B. Mascn of the Prance Stone Company and Mr. R. Annesser of the National lime and Stone Company without whose cooperation and assistance this study would have been impossible.

I also acknowledge financial support provided by the Friends of

Ortcr. Fund of the Department of Geology and Mineralogy of The Chio State

University which helped defray the cost of thin section preparation and drafting.

Finally, Ms. Yvonne M. Kolibash deserves special recognition for her incredible patience and understanding throughout the hectic years of my graduate studies and for her aid in the field and in typing the rough draft of the manuscript. VITA

January 30, 1948...... B o m - Youngstown, Ohio

1969...... B.A., Franklin and Marshall College, - Lancaster, Pennsylvania

Summer, 1969...... Geologist, Callahan Mining Corp., Osbume, Idaho .

1969-197 0...... University Fellow, Department of Geology and Mineralogy, The Chio State University, Columbus, Ohio

1970-197 2...... U. S. A m y

1972-1975...... Teaching Associate, Department of Geology and Mineralogy, The Ohio State University, Columbus, Ohio

FIELDS OF STUDY

Major Field: Geology

Studies in Sedimentology. Professor Charles. H. Summerson.

Studies in Sedimentary Petrology. Professor Christopher St. G. Kendall

Studies in Stratigraphy. Professor Walter' C. Sweet

Studies in Geochemistry. Professor Gunter Faure

Studies in Paleontology. Professors Stig. M. Bergstrom and Aurele IaRocque

Studies in Igneous Petrology. Professor Charles Schultz

iii TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS...... ii

VITA...... ill

LIST OF TABLES...... vi

LIST OF FIGURES...... vli

INTRODUCTION ...... 1

Location and Geologic Setting...... 1 Purpose and Scope of Study...... 2 Previous Work...... 6 Methods of Study...... 7

PART I. DEVONIAN CARBONATES OF CENTRAL OHIO

Chapter I. STRATIGRAPHY ...... 10 * . II. MINERALOGY...... 21

Carbonate Minerals ..... 21 Detrital Minerals...... 22 . Non-Carbonate Authigenic Minerals ..... 25 Non-Carbonate Organic Material...... 29

III. CARBONATE PETROLOGY...... '.... 31

Ccrnponents...... 31 fedimentary Structures...... *LL Carbonate Rock TS/pes...... 52

IV. DIAGENESIS...... 55

Biological KLagenesis...... 55 Lithiflcation...... 58 Dolomitizatlon...... 60 Calcitization...... 63 Sill cifi cation...... 65 iv Chapter Pace V. FACIES ANALYSIS...... 67

Introduction...... ; 67 Facies of Unit I...... 68 Facies of Unit II. .... 88 Facies of Unit III...... 114 Facies of Unit IV...... 141 Facies of Unit V ...... 154

VI. ANALYSIS OF INTER-UNIT CONTACTS...... 184

Unit I-Unit II Contact...... 184 Unit Ii-Unit III Contact ...... 186 Unit III-Unit I V Contact...... 194 Unit IV-Unit V Contact...... 201

PART II. REGIONAL ANALYSIS

VII. DEVONIAN CARBONATES OF THE OUTLIER...... 207

Introduction...... •...... 207 Detroit River (Lucas) Dolomite...... 207 Columbus limestone...... 209 Stratigraphic Analysis...... 215

VIII. PRE-TRAVERSE DEVONIAN FOCKS OF NORTHWESTERN OHIO 220

Introduction...... 220 Sylvania Sandstone...... 220 Detroit River Dolarite...... 223 Dundee Limestone ...... 229 Stratigraphic Analysis...... 236

IX. DEVONIAN CARBONATES OF THE EASTERN OHIO SUBSURFACE.... 241

Introduction...... 24l Bois Blanc Formation...... 241 Columbus limestone...... 243 Delaware limestone...... 244 Stratigraphic Analysis...... 245

X. SUMMARY OF DEP0SITT0NAL ENVIRONMENTS...... 248 •• v ■ •• •• XI. SUMMARY OF DEPOSITTONAL HISTORY...... 259

XII. CONCLUSIONS...... 267

APPENDIX-LOCATION OF MEASURED SECTIONS...... 270

LIST OF REFERENCES...... 273

v LIST OP TABLES

TABLE PAGE

1. Rock-forming constituents of the fossiliferous rocks of units I through V...... 33

vi LIST OP FIGURES

FIGURE PAGE

f 1. Index map of study areas.' ...... 2

2. Index map showing location of major study sections...... 5

3. Cross section showing major subdivisions (units) of the Devonian carbonate sequence in central Ohio...... 18

4. Photomicrograph of dark centered, clear rimmed euhedral dolomite crystals...... 23

5. Photomicrograph of authigenic quartz overgrowths on detrital quartz grains...... 28

6. Photomicrograph of pelletoids of possible fecal origin 37

7. Photomicrograph of corallite filled with two generations of drusy calcite spar cement...... 39

8. Spar-filled fenestral voids...... 43

9. Discontinuity surfaces in the upper part of Columbus limestone...... 44

10. Intensely burrowed fossiliferous packstone-grainstone 46

11. Vertical burrows...... 48

12. Photomicrograph of a boring penetrating an iron-oxide Indurated discontinuity surface...... 49

13. Horizontally laminated algal stromatolite...... 50

14. Domal algal stromatolite...... 51

15. Cross section showing distribution of rock types .... 53

16. Photomicrograph of fossil fragments with micritized rims... 57

vii 17. Contact of sandy conglomerate at the base of unit I with the Silurian Bass islands Dolomite...... 70

18. Cross section of unit I showing distribution of facies 72

19. Negative thin section print of the lower conglomeratic portion of facies 1:1...... 74

20. Negative thin section print of the upper portion of facies 1:1...... 75

21. Photomicrograph of porous dolomitized mudstone of facies 1:2...... 78

22. Brecciated bed in the upper bituminous banded portion of facies 1:2 ...... 80

23. , Upper part of unit I at locality H ...... 81

24. Coralliferous crinoidal grains tone of facies 1:3 (B) disconformably overlying the Silurian Bass Islands Group...... 84

25. Photomicrograph of facies 1:3 grainstone...... 85

26. Cross, section of unit II showing distribution of facies...... 89

27. Coral-stromatoporoid wackestone of facies 11:1.,...... 90

28. Large mound-like stromatoporoids in facies II:1...... 92 .

29. Cherty gastropod mudstone of facies II:2...... 95

30. Fossillferous packstone of facies 11:2...... 97

31. Itypical appearance .of facies 11:3 in the' field...... 100

32. Facies II:3 dolomitized wackestone..... :...... 101

33. Facies 11:3 mudstone containing numerous thin bituminous... 102

34. Facies 11:3 laminated mudstone...... 105

35. Calcite pseudomorphs after gypsum crystals in facies 11:3 mudstcne...... 106

36. Negative thin section print of facies 11:3 pelletoidal packstone-grainstone...... 107

viii 37. Negative thin section print of facies 11:3 fossiliferous and pelletoldal packstone...... 108

38. Spar-filled fenestral voids in facies 11:3 mudstone...... 109

39. Photomicrograph of sandy bed in facies 11:3...... Ill

40. Ripple-marked sandy bed in facies II:3. 112 .

41. Ripple-marked and mud-cracked sandy bed in facies 11:3.... 112

42. Cross section of unit III showing distribution of facies...,116

/ 43. Negative thin-sectian print of facies 111:1 fossiliferous wackest one...... '...... 118

44. Bedding surface in facies 111:1 covered with fragmented and abraded skeletal debris...... 119

45. Facies III: 2 burrowed packstone .... 122

46. Facies III: 3 burrow-mott led mudstone ...... 125

47. Massive mudstone of facies 111:4...... 129

48. Silty-shale bed in facies 111:4...... 130

49. Abrupt contact of facies 111:4 mudstone and facies III :5 grainstone. .... 134

50. Thin-bedded facies III: 5 g r a i n s t o n e ...... 136

51. Photomicrograph of facies III; 5 grains tone...... 137

52. Photomicrograph of facies 111:5 muds tone containing numerous plant spores..... 138

53. Cross section of unit IV showing distribution of facies....143

54. Negative thin section print of facies IV:1 grain-poor wackestone. .... 145

55. Negative thin section print of facies IV:2 packs tone-grainstone...... *...... 149

56. Photomicrograph of facies IV:2 packstone...... 150

57. Prominent "mega-rippled" surface in upper part of the Coluirfous Limestone...... 152 ix 58. Cross section of unit V showing distribution of facies. 156

59. Negative thi'nsection print of fhcies V:1 grainstone.... 159

60. Pyrite-fllled burrows in facies V:1 packstone...... 160

61. Facies V:2 crinoidal wackestone...... •.... 163

62. Cherty and silty argillaceous laminated mudstone of V:3 overlying facies V :1...... 166

63. typical appearance of facies V:3...... 167

64. typical appearance of the lower part of facies V:4...... 171

65. Photomicrograph of facies V:4 mudstone...... 172

66. Burrowed argillaceous mudstone of facies V:4...... 174

6 7 . Negative thin section print of facies V:5 grainstone. 178

68. Negative thin section print of facies V:6 fossiliferous wackestone-packstone ...... 180

69. Unit I-unit II contact ...... 185

70. Unit II-unit III contact at locality U...... 188

71. Unit II-unit III contact at locality MCS...... '...... 189

72. Unit II-unit H I contact at locality B. . .191 1 ...... - 73. Unit II-unit III contact at locality F...... 192

74. Polished slab showing unit III-unit IV contact...... 195

75. Unit III-unit IV contact at locality B...... 197

7c. Unit III-unit IV contact at locality BE...... 198

77* Iron-oxide indurated and bored chscontinuity surface which terminates unit IV ...... 202

73. "Bone'-fragjrent bearing grainstone of facies V:1 sharply overlying packstone of facies IV:2...... 203 i 79. Upper part of the "Columbus" in the outlier...... 213

80. Schematic cross section from the outlier to north-central Ohio showing inferred stratigraphic relations and facies distribution during early Unit III time...... 219 x * 81. Negative thin section print of dolomitized oolitic calcarenitlc from the "Lucas" portion of the Detroit River...... 228

82. "Lower Dundee Lines tone"...... 231

83. Negative thin section print of "Upper Dundee" packstcne..... 235

84. Hi^ily idealized cross section of eperic sea in Middle Devonian time in Ohio showing distribution of basic depositional environments .... 250

85. Cross section showing distribution of facies groups in the Devonian carbonate sequence in Ohio...... 255

86. Restored East-West cross section of the Devonian carbonate sequence in northern Ohio showing relations of stratigraphic units and inferred distribution of facies groups...... 257

87. Inferred distribution of major depositional environments in Ohio at various times during the deposition of the Lower-Middle Devonian carbonate sequence...... 261

xi DffiRODUCriON

Location and Geologic Setting

A sequence of upper Lower Devonian (Emsian) and Middle Devonian

(Eifelian) carbonate rocks of approximately 250 ft maximum thickness crops out in three areas in Ohio (Figure 1). ihe major stratigraphic units conprlsing this sequence are the Coluinbu3 Limestone, the Delaware

Limestone (Dundee Limestone of northwestern Ohio), the Detroit River

Group (including the Sylvania Sandstone), and the Bois Blanc Formation.

In each of the outcrop areas the Lower-Middle Devonian carbonate sequence rests disconformably on carbonates of the Silurian Bass Islands Group and is overlain diseonfonrably by upper Middle Devcrdan (Glvetian) shales and/or argillaceous limestones.

Ihe Devonian carbonates which crop out in the north-south trending belt in north-central Ohio lie on the eastern flank of the

Findlay Arch, a northern extension of the Cincinnati Arch, and dip eastward into the Appalachian Basin at approximately 30 ft. per rrdle

(Bates, 1969, p. 164), whereas those which crop out in northwestern

Ohio lie cn the opposing flank of the Findlay Arch ,nd dip northward and westward into the Michigan Basin at 15-20 ft per mile (Janssens,

1970b, p. 1). Devonian carbonates are thus present in the subsurface 2

Ont

Mich LAKE ERIE T ol ed o

Sandusky

N or t h w e s t outcrop belt :;X; ^ C e n t r a l outcrop belt •o c

The Col ambus Outlier

20 40 60 Scale in miles

Outcropping Devonian Carbonates

Devonian Carbonates in subsurface

Older rocks

Figure 1: Index map of study are^s. ' 3 of eastern Ohio and a few counties in northwestern Ohio, but have been

eroded from the axial area of the Findlay Arch except for the small

outlier centered in Logan County. Ihe Devonian carbonates which crop

out in central Ohio continue to the north beneath Lake Erie, cropping

out again on Pelee Island and in southwestern Ontario. To the south they are progressively truncated by the dis conformable surface at the base of the Glvetlan shales, the latter resting directly on Silurian

carbonates at places in southern Ohio. Sane of the southward thlnlng i3 probably depositional. The Devonian carbonates which crop out in northwestern Ohio continue to the northeast into Michigan and Ontario and to the west into Indiana along the northern flank of the Kankakee

Arch.

Purpose and Scope of Study

Ihe purpose of this study was to describe the petrology of the

Lower and Middle Devonian carbonates exposed in Ohio and to reconstruct their depositional history. Fifty exposures v/ere studied in the three outcrop areas during 1972-1975, trie locations of the most important of which are shown in Figure 2. Drill cores wliich penetrated portions of the seousnce which were not exposed were also studied from several localities in the central Ohio outcrop belt. The discussion of the

Devonian carbonates in the eastern Ohio subsurface is based largely on data presented by other woricei*c.

This report is divided into two parts. The fLrst part is a detailed analysis of the Devonian carbonates of the central Ohio outcrop belt, with the major enphasis placed on analysis of facies and Figure 2: Index map showing location of major study sections. All cross sections of the Devonian carbonate sequence In the central Chio outcrop belt were constructed by projection onto the line HM-B-KI. Toledo \ LAKE ERIE Lucas Ottawa

S an d u s k y S an d u s k y S D , P K Erie! S eneca

I

C ra wf o rd

Marion

_ • O W , i__ Scale m iles j Union.. . I 1 i D el aw a re M j B R i C B f — I Chdmpai MCT M C H 1 Do 1umb us AA S Franklin r1

HM P ickaway

Figure 2. inter-unit contacts. In the second part the Devonian carbonates of the outlier, northwestern (Mo, and the eastern Ohio subsurface are discussed and their stratigraphic and sedinentologLc relationships to the Devonian carbonates in central Ohio sire analyzed, providing the franework for the discussion of regional depositional history which concludes the study.

Previous Work

Iithology and paleontology have been used as a basis for stratig­ raphic subdivision of the Devonian carbonates In Ohio by numerous workers including Prosser (1903, 1905), Swartz (1907), Stauffer (1909), Mo3es

(1922), Westgate (1926), Wells (19*17), Ksrr (1950), and Dow (1961).

Few workers, however, have attempted detailed petrographic and/or environmental analysis of these rocks, and those that have, have dealt with areally and stratigraphically restricted portions of the sequence or with specific features. Wells (1947) inferred biotopes for the four lithotopes which he recogiized in the upper part of the Columbus

Limestone and the Delaware Limestone in the Eranklin-Delaware counties area of central Cnio. Bailey (1969) divided a core which penetrated most of the lower part of the Devonian carbonate sequence in Ottawa

County in north-central Ohio into several facies on the basis of lithologic and geochemical variations. The so-called "bone-beds’1 in the upper part of the Colunfcus and in the Delaware in central Ohio were studied by Westg^te and Fischer (1933) and Wells (19*14), and an abraded rippled appearing surface underlying one of the bone-beds was described and its origin discussed by Bates (1969). Ihe basal Sylvanla Sandstone Member of the Detroit River Group In northwestern Ohio has been studied by numerous workers including Grabau and Sherzer (1910),

Carmen (1936), and Hatfield, Rohrbacher, and Floyd (1968). Janssen3

(1970b) speculated on the possible environments of deposition of the various units comprising the Devonian carbonate sequence in northwestern

Ohio and both Sparling (196*0 and Janssens (1568, 1970a) presented stratigraphic evidence in support of the theory that the Detroit River of northwestern Ohio and the upper part of the Colunbus in central Ohio were deposited ccnteirporaneously.

Methods of Study

Held

All sections were measured to an accuracy of 0.1 ft. with a steel tape. Features recorded for each measured interval included tiiickness, color, texture, sedimentary structures, biota, and nature of contacts.

Special attention v/as given to the orientation and degree of fragmentation and abrasion of the fossils. At most localities oriented approximately

2 leg. samples were collected from 1 ft. intervals, and at a few localities larger oritented samples of each Raj or rock type up to

1.5 ft. in diameter were collected. Sanples were also obtained of all shale er.a clay partings and seams at each locality. In all over 1900 samples were collected for more detailed laboratory study.

Laboratory

.Approximately 900 rock samples were slabbed perpendicular to bedding. Acetate peels were made of many of tlie slabs and thin sections were made from more than 600 of them. Che-quarter of each thin section

was stained with Alizarin-red stain according to the method of Sabins

(1962) to aid in the differentiation of calcite and dolomite. Small

portions of some of the thin sections were also immersed in dilute

hydrochloric acid until all the carbonate was dissolved so that the

distribution of the acid insoluble material could be studied. To in­

sure uniformity of observation, a data table was prepared cn which a

number of textural, palecntologic, mtneralogic, and diagejnetic parameters

were listed. For each sample the relative abundance or degree of

development of each parameter was estimated using a relative numerical

rating scale. To obtain quantitative data cn the rock-forming constitu­

ents numerous samples were point-counted using the methods and considera­

tions of Jaanusscn (1972).

Insoluble residues of 200 samples were obtained by dissolving

approximately *10 g of the sample in dilute hydrochloric acid. Hie

residue of each sample was separated into fine and coarse fractions

using the method of Summerson and others (1957)* and the weight per­

centage of each of these fractions to total sample was calculated.

Both size fractions were studied under a binocular microscope and x-ray

diffraction patterns were obtained for the fine fractions of irany

samples as well as for sanp3.es of the clay and shale partings and seams.

X-ray diffraction patterns were also obtained of fifty of the

samples for which stained thin sections had been prepared. The relative

calcite-dolomite content of each of these samples was determined using

the peak-heigpt ratio method of ferment and Berger (1957)* These sam­ ples served as standards for estimating the calcite-dolomite content

of sanples for which diffraction patterns were not obtained. f

PART I

DEVONIAN CARBONATES OP CENTRAL OREO

9 CHAPTER I

STRATIGRAPHY

The Devonian carbonate sequence of central Ohio was first differentiated from the underlying Silurian carbonates by James Hall

(1843), who referred to it as the "Comiferous limestone," a name previously applied to a limestone interval with a similar fauna in

New York. This correlation was accepted by Newberry (1873* p. 143), who made the first detailed scudy of the Ohio " Comiferous," separating it into two divisions: a lower light-colored cherty fossiliferous limestone interval which he referred to as the Colunhus limestone, and and upper "blue, thin bedded limestone from fifteen to twenty feet in thickness" which he named the Sandusky limestone. Winchsll (1874) also recognised these two divisions, but believed that only the lower

(Columbus Limestone) actually correlated with the "Coniferous" of

New York. Orton (1878) agreed in general with Viinchell, but formally intro-duced the neroe Delaware Limestone for the upper division in the

Erarbzlin Ccunty-Delaware County area. During the next 15 years there was considerable uncertainty as to the exact relations between the

Colu-rbus, Sandusky, and Delaware limestones. This uncertainty was re­ solved when Prosser (1905) and Swarts (1907) 3howed tliat the partial of the Sanau3ky limestone beneath a bed containing many phosphatic

10 u "bone" fragments wa3 faunally more similar to the upper part of the

Columbus than the lower part of the Delaware in the Franklin County-

Delaware County area. Therefore, the Sandusky Limestone was dropped ft*am Ohio stratigraphic nomenclature and throughout central Ohio the entire Devonian carbonate interval aboe the ’’bone-bed” became known as the Delaware limestone.

Swartz (1907) recogiized three members of the Columbus Limestone in the Sandusky area which he named, in descending stratigraphic order, the Venice lumber, the Marblehead Member, and the Bellepoint I-terrber.

The Venice Member coincided with the lower part of the former Sandusky

Line stone and consisted of 20 ft. of massive blue limestone with a

"bcne-bed" at the top. The underlying ISarblehead Member consisted of

MO ft. of fossiliferous gray limestone with a cherty interval in tlie middle. Tie basal Bellepoint Member consisted of M-7 ft. of ’'brown limestcne" with a thin sandstone interval at the base. Swartz believed that the Bellepoint Member of northern Ohio correlated with the much thicker lover "brown limestone" part of the Columbus Limestone in the

Columbus area which was well exposed along the Scioto River near

Bellepoint in southern Delaware County. Swartz also identified several prominent b radii opod horizons in tlie Marble head and Venice members.

Stauffer (1909) ntide an even more extensive subdivision of the

Columbus as well as the Delavrare in the Franklin County-Delaware County area, recognizing 13 faunal and/or lithologLc zones which he designated by the letters A throu^i M. Zones A througi H are in tiae Columbus and zones I through M are in the Delaware. Stauffer observed that the 1 2 thickness of the Columbus decreased by 44 ft. from the Columbus area

to Lake Erie and because the "Spirlfer gregarious horizon" of Swartz

(1907) (Stauffer’s zone F) occurred much higher above the base of the

Columbus in the south than in the north he suggested that "the diminution

in the thickness of the formation as a whole and that the fhuna occur­

ring in the base of the formation in the Sandusky region reappears later

in the vicinity of Columbus" (p. 143).

Vfestgate (1926) subdivided the Columbus Limestone in Delaware

County into four parts, entirely on the basis of physical characteristics.

For the lower 30 ft, tliiek massive brown "iragneslan limestone" portion,

which Includes Stauffer’s (1909) zones A and B, he retained Swartz's

(1307) narre Bellepoint Member. The overlying 6 ft. thick interval of

coral- ar.d stromatoporoid-rich brown limestone coinciding with

Stauffer's (1909) zone C was referred to as the "coral layer" by

Vfestgate (p. 22).. It is overlain in Delaware County by an approximately

6 ft. thick interval of massive limestone containing scattered large

brachiopods and corals which is coincident with the lower part of

Stauffer's (1909) zone E. Ihis interval was referred to as the

"Spirifer macrothyrls zone" by Vfestgate (p. 22). lhe approximately

40 It. thick interval very fossiliferous limestone forming the upper

part of trie Columbus in Delaware County and Including Stauffer's (1909)

zones E (upper part) to H was named the Klondike Member by Vfestgate

(p. 24). Vfells (1947) applied formal biozone names to Stauffer's zones of the Columbus and Delaware limestones and recognized three members of the Columbus in Franklin County. He retained the name Bellepoint Member 13 for the lower "magpeslan limestone" portion of the Columbus, but unlike

West gate (1926) also included Stauffer’s zone C In it. Vfells named the

overlying 6 ft. thick interval of cherty limestone (Stauffer’s zone D) the Eversole Member and the upper approximately % ft. thick interval of fossiliferous limestone (Stauffer’s zones E throu$i H) the Delhi

Member. Thus, Swartz's (1907) Mhrblehead and Venice members, Westgate's

(1926) Klondike Merrtoer, and the Delhi Meifber of Vfells (19^7) are essentially coincident.

Until approximately 1920 the Columbus Limestone as defined by

Prosser (1905)* Swartz (1907), and Stauffer (1909) was believed to be the oldest Devonian unit in central Ohio and was presumed to everywhere overlie unccnformably Silurian I-taroe strata. The Monroe in north­ western Ohio and southeastern Michigan was divided into three members by Prosser (1903), which cane to be known, from oldest to youngest, as the Eass Island (Lower Monroe), Sylvania Sandstone (ItfLddle Monroe) and Detroit River (tapper Monroe) (Lane, Prosser, and Grabau, 1907).

Prosser (1905) recognized that in central Ohio the Columbus rested cn the "Upper Monroe” (called "Lucas" by him) in the Sandusky area, whereas in the Colunbus area it rested cn the "Lower Monroe." However, binee the entire Monroe was believed to be Silurian by Prosser, this relationship was not inconsistent with the prevailing belief at the time that the Columbus everywhere rested unccnformably on Silurian strata. Furthermore, when Stauffer (1916) and Williams (1919) showed that the Detroit River (Lucas) contained a Devonian rather than Silurian fauna it was merely assured tiiat in the Sandusky area and northv:estem

Ohio the Columbus rested unconformably can older Lower Devonian strata. i4

Subsequently, though, the gradual realization that tha Detroit River fauna was Middle Devonian and the correlation o.f the Dundee (Golumbus)

Limestone of northwestern Ohio and southeastern Mchigan, which dis- ccnformably overlies the Detroit River in those areas, with the Delaware instead of the Columbus of central Oliio (Cooper and others, 1942;

Ehlers, Stuirm, and Kesling, 1951) led to proposals that Columbus and

Detroit River deposition may have been at least in part ccntenporaneous

(Ehlers, 1945; Briggs, 1959* Sparling, 1964; Janssens, 1968, 1970a).

Several workers have attempted to apply the formational terminology of the Detroit River Group in it3 "type" area in southeastern liLciiigan to the strata containing the Detroit River fauna in north-central Chio,

At locality C in Erie County Carmen (1927) assigned the upper approxi­ mately half of the 50 ft. thick exposed Detroit River interval to the

Lucas Formation and the lower half to the Arahertsburg Formation, the distinction apparently being made more cn the basis of llthology than cn fauna.. The Lucas vas characterized by Careen (p. 501) as being

"thinner bedded and more even grained than the Amhertsburg below," which was described as being "bran, porous dolomite." Kerr (1950) also used Detroit River fonratlonal terminology in his report cn a core from Ottawa County (locality HH) which extended from the lower part of the Columbus into the Silurian Bass Islands Group. In this core

Kerr found a 150 ft. thick carbonate interval between the base of the

Columbus and the top of the Bass Islands which he assigned entirely to the Detroit River Group because of the presence of a sandstone bed in the lower few inches which he believed correlated with the Sylvania 15 Sandstone of the northwestern Ohio-southeastern Michigan area. This

sandstone was succeeded by 100 ft. of daik-brcwn massive dolomite

containing many white chert nodules and calcite crystals in cavities.

This interval was identified as the "Amhertsburg Dolomite*1 by Kerr.

It was overlain by 50 ft. of thin bedded, light colored laminated unfossiliferous limestone and dolomite containing numerous sandy and brecciated zones. Ihis interval was identified as the "Lucas Dolomite” by Kerr. Bailey (1969) also studied a care from Ottawa County and used similar criteria to differentiate the Lucas and Amhertsburg. Prior to the author’s study no other studies of cores penetrating the lcwer part of the Devonian carbonate sequence in the north-central Ohio out­ crop area had been made so tliat recent workers (Dow, 19ol; Sparling, / 1965; Janssens, 1970a; Conkin and Cctikin, 1973) have accepted Kerr’s assignment of the entire pre-Columbus part of the Devonian carbonate sequence in that area to the Detroit River. As will be discussed in the chapter on Devonian Carbonates of the Eastern Ohio Subsurface, however, only the upper third of this interval probably actually represents the Detroit River.

Because the existing classification and nomenclature of the

Devonian carbontes in central Ohio is somehwat confusing, with the boundaries of the units not well defined or differing from author to author, and stratigraphic names defined in one area being inconsistently used in others, the author has constructed a framework for petrologic and environmental analysis which is independent of previous stratig­ raphic terminology. This framework consists of five Informal units, each of which extends throughout the outcrop belt, although the upper two were caipletely removed by erosion prior to deposition of the

Devonian shales at locality HM in Pickaway County. These units, although

in general somewhat 11 thologically distinct from one another, are

actually groups of two or more distinct facies. The units are separated frccn each other in most places by sharp distinct contacts. These inter­ unit contacts were carefully studied since a primary objective of the study was to determine whether each unit represented a distinct "time- rock" interval, in other words a "package" of lithologles bounded above and below by temporally significant diastems, or whether the units merely represent coexisting stratigraphic facies superimposed as a result of lateral migration of depositional environments in response to relative sea level fluctuations 30 that the inter-unit ccntact3 / merely represent facies boundaries. The necessity of resolving such questions has been emphasized by Heckel Q-913, p. 121), who noted that

"merely assuming that gross lithologlc units represent the deposits of cne delineated period of time has led to much confusion in correlation and to misinterpretation on environmental relations." Thus, for instance, careful study by Rickard (1962) and Laporte (1967) has shown that the commonly recognised units of the lower Devonian Helderberg

Croup of New York, which were believed by earlier workers to be tims- stratigraphic lithologlc units, actually represent contemporaneous, but time-transgressive and interflngering stratigraphic facies, each of which is progressively younger from eaat to west.

Yhe five units recognised by the author in the central Ohio

Devonian carbonate sequence are referred to by the Roman numerals I tlrrough V in ascending stratigraphic order. Figure 3 shows their 17

Figure 3J Cress section showing major subdivisions (units) of the Devonian carbonate sequence in central Ohio. Measured sections shown are those studied by the author during 1972-1975. 00 y l u a NORTH-CENTRAL AREA QQ CO Measured Section and location abbreviation — <_> Core aus=:2>2:^oa SILURIAN BASS ISLANDS GROUP vcui ■Exposure 2 :2 : 1—to o oc£ nizr SOUTH-CENTRAL AREA HORIZONTAL SCALE-MILES DEVONIAN SHALES VERTICAL SCALE-FEET

Figure 3. - 19 distribution and the stratigraphic interval studied at each major

locality. The unit Ill-unit IV contact has been used as a datum for

this diagram, and although this contact probably closely approximates

an isochronous horizon in the outcrop belt it was chosen a3 a datum for the diagram primarily as a matter of convenience, and therefore no

conclusions should be drawn from the diagram regarding the possible lateral relationships of the units. Because major facies changes take place in several units between locality S in Crawford County and locality

B in Seneca County the portion of the outcrop belt north of and including

Seneca County will be referred to as the "north-central area," and the portion south of and including Crawford County to the south as the

"south-central area." The relationships of the author's units to the

\ stratigraphic units and divisions of previous authors are discussed below.

Unit I: In the south-central unit I corresponds to the Bellepoint

Member of the Columbus as defined by West gate (1926) and includes

Stauffer's (1909) zones A and B. In the north-central area it coincides with Kerr’s (1950) "Sylvania Sandstone" and "Amhertsburg Dolomite."

Unit II: In the south-central area unit H includes Stauffer's

(1.909) zones C and D, the latter coinciding vrith Yfells' (1947) Eversole

Member of the Columbus. In the north-central area unit II corresponds closely to Kerr's (1950) "Lucas Dolomite" and Janssens (1970) 11Detroit

River beds," and the upper few feat of the unit may coincide with

Swartz's (1907) Bellepoint Member of the Columbus.

Unit III: In the 3oufch-central area unit III corresponds to all but the upper few feet of Yfestgate's (1926) Klondike Member and Vfells'

(1947) Delhi Member of the Columbus and includes Stauffer's (1909) 20 zones S through G . In the north-central area it corresponds to Swartz’s

(1907) Marblehead Member of the Columbus.

Unit IV; In the south-central area unit IV coincides with the upper few feet of Vfest gate’s (1926) Klondike lumber and Wells’ (1947)

Delhi Member of the Columbus and with Stauffer’s (1909) zone H. In the north-central area it corresponds to Swartz’s (1907) Venice Member of the Columbus.

Unit V: Unit V corresponds to the Delaware limestone of previous workers, although the author’s unit IV-unit V contact does not every­ where precisely coincide with tlie Columbus-Delaware contact of some previous authors. In the south-central area unit V includes Stauffer's

(1909) zones I through M.

/ CHAPTER II

MINERALOGY

CARBONATE MINERALS

Gsneral

The Devonian carbonates of Ohio consist almost entirely of varying proportions of the carbonate minerals calcite and dolomite.

Four inineralogieal classes are defined on the basis of the relative percentages of calcite and dolomite; 1) limestone (calcite greater than SO percent); 2) dolomltic limestone (calcite between 50 and

90 percent); 3) calcitic dolostone (calcite between 10 and 50 percent) and *0 dolostone (calcite less than 10 percent). Calcitic dolo3tone and dolostone are dominant in units I and II, although some parts of both of these units are dolomltic lirrestone or limestone, and dolcrritic limestone and limestone are dominant in units III through

V,

Calclts

A H of the calcite is of the low-magpesian variety. It occurs as fossil fragments, as fine-grained matrix, as cement filling primary and secondary voids, and as necmorphic replacement spar.

21 22

Dolomite

Dolomite occurs a3 a diaganatic product replacing calcite and

authigenic quartz. Primarily on the basis of crystal size two broad

types of dolomite were recogiized. The first type is characteristic

of the very finely crystalline to medium crystalline dolcatones which

occur in unit II in the north-central area. Thin sections of these

rocks show that they consist of equigranular mosaics of packed ralcron-

sized anhedral appearing dolomite crystals. The second type of dolomite is the dominant type everywhere except in unit H in the north-central area. It consists of centimicron to decimicron-slzed euhedral crystals which have dark euhedral centers and clear outer rims (Figure 4), In dolomitic limestones these larger dolomite crystals occur as isolated porphyrotopes scattered throughout a fine calcitic matrix which they have partially replaced. In calcitic dolostones, however, the dolomite eubedra are so abundant that they abut against one another and may partially replace fossil Pregnants as well as matrix. In dolostones the fossil fragnents are either completely re­ placed by dolomite or are represented by molds. No matter what the degree of dolonitization, however, the dolomite crystals are alvays fairly' uniform in size in a given sample, and in general are no coarser in dolostones than they are in dolomltic limestones.

DETRITAL MINERALS

Quartz

Quartz is the only common detrital mineral (except for lllite in unit V), Two general textural types of detrital quartz occur. The 23

Figure 4: Photomicrograph of dark centered, clear rimmed euhedral dolomite crystals partially replacing fossiliferous limestone. Facies 111:6, locality MCT. Scale equals 1 mm. 2k

first is well rounded, fine to medium "frosted" sand. The second is

angular to subangular silt, most grains of which are elongate.

The rounded quartz is most abundant in the lower 5-10 ft of

unit I where it occurs disseminated and as stringers in dolostone and

in seme places forms orthoquartzitic sandstone lenses. It is also

common in unit II, especially in the north-central area where it

occurs concentrated in intervals up to several feet thick in otherwise

sand-free carbonates. Rounded quartz sand grains are also coraron in

the lower few inches of units III, IV, and V and occur scattered throughout the middle part of unit III in the south-central area.

The angular quarz silt is most abundant in natrix-rich rock3 in

unit V, nost thin sections of which snov.'ed 10-30 disseminated quartz

silt grains, and in the part of unit II coinciding with Stauffer’s

(1909) D zone in the south-central area.

K-ost of the quartz sand in the Devonian carbonates was probably derived from already mature Cambrian and Ordovician sandstones exposed in the region of present-day Wisconsin. Energetic winds carried eroded sand grains from these deposits to the east where they were dropped and either became dispersed in shallow seas or were concentrated 1 cn emergent areas, only to be reworked and redistributed by marine agerios when the emergent areas were subsequently inundated (Surrmerson aid Swann, 1970). The common quartz silt grains in unit V are associated with moderate amounts of detrital clay minerals, and both were probably carried into the sea from distal terrigenous source areas to tne east. 25

Clay Minerals

Clay minerals are most abundant In unit V, especially in the south-central area, where they occur disseminated in mudstones, some of which contain up to 30 percent fine insoluble residue (most of it clay), and concentrated in shaly partings. Scattered clayey and/or shaly partings also occur in most of the other units. Clay minerals also form most of the insoluble material concentrated along stylolitlc sutures.

Diffraction patterns revealed that illlte was the only clay mineral present in most of the sanples, although some samples contained very small amounts of chlorite.

Miscellaneous Detrital Minerals

Wherever the rounded quartz sand grains are abundant uncoonon

"accessory" mineral gains also occur, including zircon, tourmaline, feldspar, and magnetite. Biotite, a corrmon accessory mineral in the

Middle Devonian Qnandoga Limestone of Mew York, where it is believed to be of volcanic origin (Undholra, 1969), was not observed in the

Devonian carbonates of central Chio.

NON-CARBONATE AUIHIGENIC MINERALS

Quarts

Authigenic quartz occurs in three main modes. In decreasing order of abundance these are: 1) as chert bands and nodules; 2) as a replacement of fossils not associated with chert; and 3) as over­ growths on detrital quartz grains. 26

Discontinuous chert bands and chert nodules are most abundant in unit V in the south-central area and In unit I in the north-central area. In unit II chert only occurs in the south-central area in the portion of the unit coinciding with Stauffer’s (1909) D zone. In unit

III chert i3 conanon only in the lower and middle parts of the unit in the north-central area. Chert is very rare in unit IV except near the top of the unit in the Franklin-Delaware counties area. The chert in units I through IV is exclusively white to light gray, whereas in unit V both gray and dark brown chert is coiranon, the latter being most conspicuous in Franklin County. The texture of the chert is quite variable, even within the same unit, ranging from very porous (especially in unit I) to dense and flint-like (especially in unit V).

Three major types of authi genic quartz occur in the chert bodies:

1) dense inicrocrystalllne quartz consisting of minute randomly oriented grains up to 0.05 nm in diameter; 2) fibrous quartz (chalcedony); and 3) megaquartz consisting of an interlocking mosaic of equant crystals up to 0.4 inn in diameter. The bulk of most chert bodies consists of the dense microcrystalline quartz. It is colorless in thin section, bub contains numerous small dark inpurities. In most chert oodles Sharp dolomite euhedra occur scattered throughout the micro­ crystalline quartz. The fibrous quartz lines former voids and in thin section has a very conspicuous orange-brown color under plain light. The megaquartz also occurs as a void filling, typically suc­ ceeding a layer of fibrous quartz, and also replaces fossils included in the chert. It is colorless and very clean appearing in plain light. 27

Partial replacement of fossil fragments by authigenic quartz has occurred in most fossiliferous calcarenites, especially those in units III, IV, and V. Ihe siliciflcation appears to have been selec­ tive, with brachiopods and corals having been the most susceptible and echinodenms and bryozoans the least. Ihe replacement quartz varies from irregular masses of microcrystalline quartz to spherical masses of fibrous appearing quartz. Although partially silicified fossil fragments occur scattered throughout the fossiliferous parts of units

III, IV, and V they are especially abundant in the upper foot of units

III and IV and the basal few inches of units IV and V.

Euhedral authigenic quartz overgrowths on rounded quartz sand grains are quite conspicuous in the lcrwer sandy part of unit I. These overgrowths, are optically continuous with the detrital nuclei and are usually doubly terminated. They tend to occur only where the quartz grains are packed together and only rarely occur cn isolated grains, lhe overgrowths as well as the detrital nuclei may be partially re­ placed by dolanlte crystals (Figure 5).

Pyrite

Pyrite is most common in the matrix-rich rocks In units IV and i V where it occurs as 0.01-0.1 mm euhedral grains disseminated through­ out the matrix in small quantities, as larger masses and aggregates in the centers of burrows, and as a replacement of fossil fragments, especially bryozoans and phosphatlc fish remains. Ilnute euhedral pyrite grains also occur disseminated throughout the sandy zone at the base of unit I and in the sandy intervals in unit II in the north-central 28

Figure 5: Photomicrograph of authigenic quartz overgrowths on detrital quartz grains. Note the dolomite euhedra replacing both the detrital nuclei ana the overgrowths. Facies 1:1, Locality KCT, S ale equals 0.5 nm. 29 area. Masses of crystalline pyrite up to several Inches in diameter

occur In tlie upper 0.5-1 ft of the Etevonian carbonate sequence In the

south-central area immediately below the disconformity at the base

of the Olentangy or Ohio shales.

Miscellaneous Authigenic Mdnerals

Small clusters of ligit tan and purple fluorite crystals and

irregular shaped masses of iron oxide material (limonite?) were observed

in many of the coarse residues from units II and III, but are very

rare in the coarse residues pf the other units. The fluorite Is most

abundant in unit II in the north-central area where it occurs as crystals

lining leached coral molds, and in a 3-4 ft interval in unit III at

locality S where similar crystals line incompletely filled shelter voids

beneath concave down oriented brachiopod vlaves. Gypsum crystals were

at one time present in some beds in unit II in the north-central area, but are today represented by molds or calcite pseudcmorphs after gypsum.

NON-CARBONATE ORGANIC MATERIAL

A variety of non-carbonate material of organic origin is present in the Devonian carbonates of central Ohio including phosphatic fish remains and ccnodonts, chltinous scolecodoits, and plant spores. The phosphatic fish remains, which include fish bones, plates, teeth, and spines, are most abundant in units IV and V where they occur as sand size fragments concentrated in several "bone-beds" and as larger fragments scattered throughout the two units. A few larger fish bone fragments were also observed in fossiliferous parts of units II and 30

III. Fl3h remains were not observed either in unit I or in unit II in the north-central area, however. A detailed study of the conodont distribution in was not mads; however, they appeal* to be most abundant in units IV and V and are especially abundant in the "bone-beds.”

Both scolecodcnts and spore exines are common in portions of units III, IV, and V and are uncommon in units I and II. The scolecoaonts are most abundant in the middle part of unit III in the north-central area, especially in a prominent thin silty shale bed.

The spore exines are most abundant in the upper part of unit III in the north-central area and throughout most of unit V in the south- central area. Spores are so concentrated in some beds in the upper part of unit III in the north-central area that such beds serve as excellent marker beds in individual quarries. Much bituminous material of uncertain origin occurs in parts of units I and II. CHAPTER III

CARBONATE FETRDLOGY ...... 1" 1 T

Excluding diagenetic dolomite and calcite spar the Devonian carbonate rocks of central Ohio consist of varying proportions of grains, matrix, and calcite spar cement. The abundance and distribu­ tion of mechanical and biogenic sedimentary structures, serve as the major basis for the differentiation of facies within each unit.

COMPONENTS

Grains

Grains are discrete carbonate particles greater than 0.02 im in diameter and capable of forming a rock framework (Dunham, 1962, p. 113). Three types of grains were recognized: lithoclasts, frameworks, and allochems. The latter are by far the most abundant type. lithoclasts

lithoclsts were defined by Folk (1962, p. 63) as "fragnents of consolidated limestone eroded from ancient limestones outcrops on an emergent land area.11 The basal few feet of unit I at most places contains well rounded lithoclasts of the underlying Silurian dolomite

31 32

up to a foot In diameter. Rounded and bored lithoclasts up to several

inches in diameter derived from unit IV occur in the lower few Inches

of unit V in the south-central area.

Frameworks

Frameworks are the in situ remains of organisms which encrusted

and/or bound the substrate, such as colonial corals and some

stromatoporoids. Ihey are common only in the portion of unit II in

the south-central area corresponding to Stauffer* s (1909) zone C.

Allochems

Allochems are discrete bodies formed by chemical or bioaction

within the basin of deposition and which have undergone some post-mortem

transport (Folk, 1962, p. 63). Three major types of allochems occur

in the Devonian carbonates in central Ohio: biochems, intraclasts,

and pelletoids, of which biochems are the most abundant.

Biochems: Biochems are fossil fragments. In peels and thin

sections of fossiliferous rocks have have not been intensely dolomitized

most biochems can be identified to phylum, and sometimes to family, by

their morphology and internal structure. Quantitative data on the

biologic conposition of the biochems in each unit was obtained by

point counting 128 samples distributed between the five units. The mean percentage and the percentage range of each parameter for the

thin sections studied from each unit are given in Table 1. In terns

of average biochem conposition all of the unit3 are very similar with

regard to major constituents, echinodera fragments forming approximately half of the biochems and the remainder consisting primarily of subequal Table 1. Rock-forming constituents of the fossiliferous rocks of units I through V. The mean percentages and percent a gp ranges of each parameter are based on petrographic modal analysis of N samples for each unit. T 13 trace.

Unit I... . . II.. III. IV V

N (number of samples) 7 6 50 33 55 MAJOR COMPONENTS - Matrix 39(0-62) 50(0-80)- -43(0-97) 66(0-98) 75(7-99) Spar 12(0-46) 6(0-40) 10(0-46) . 4(0-40) 2(0-26) Biochems 49(38-52) 44(20-56) 47(3-70) 30(2-72) 23(1-73)

BIOCHEMS Echinoderms 72(18-90) 54(15-92) 60(0-96) 52(G-83) 40(0-80) Brachiopods 12(4-33) 17(11-23) 13(0-77) 12(0-57) 24(0-82) Bryozoans 7(3-14)- 8(2-15) 7(0-35) 12(0-32) 14(0-41) Trilobites T(0-1) T(0-1) T(0-2) l(T-5) T(0-l) Ostracods T(0-1) T(0-1) T(0-3) T(0-2) T(0-3) Mollusks T(O-T) • . T(0-l) 1(0-7) T(0-5) T(0-2)' Corals T(0-2) -• - • 3(0-15) 1(0-10) 1(0-3) T(0-2) Stromatoporoids T(0-1) 2(0-6) T(0-T) 0(0-0) 0(0-0) Tentaculites 0(0-0) 0(0-0) T(0-t) 2(0-44) 3(0-50) Charophyte oogenia 0(0-0) 0(0-0) 3(0-19) 0(0-0). 0(0-0) "Bane" fragments 0(0-0) 0(0-0) 0(0-0) 1(0-6) 1(0-9) Ihdetenrinant • 9(0-16) 16(8-28) 15(1-30) 19(0-29) 18(0-60) quantities of brachlopod, bryozoan , and indeterminant fragments In each

unit. Furthermore, the range of abundance of each of these major

constituents is generally similar in each unit so that it is virtually lirpossible to differentiate the unit3 cn the basis of major blochem conposition. Scrae of the less abundant types of biochems are more restricted in their stratigraphic occurrence, however, and thus are somewhat useful in differentiating the units. Tentaculite fragments, for example, were observed only in units III, IV, and V, and occur in more than trace amounts only in the latter two. Similarly, "bone” fragments were observed only in units IV and V. The only type of biochem which appears to be diagnostic of a single unit are the small, hollow spherical calcareous bodies believed to be charophyte oogonia, the calcified spore cases of presumably fresh-water algal plants

(Stewart, 1955; Conkin aid Conkin, 1972). These bodies were observed cnly in thin sections of very fossiliferous unit III rocks.

Intraclasts: Folk (1962, p. 63) defined intraclasts as

•'fragments of penecontemporaneous, generally weakly consolidated carbonate sediment that have been eroded from adjoining parts of the sea bottom and redeposited to form a new sediment." Intracla3ts are irtost conspicuous in units I, II, and III. In both the basal and upper parts of unit I throughout the south-central area beds were observed which contain nurrerou3 angular to subrounded intraclasts up to an Inch in diameter. These intraclasts are identical in texture, and usually also somewhat similar in colore, to the enclosing matrix. Such beds are interpreted as representing periods of disruption of a semi- lithlfied muddy substrate by storm waves, the roundness of the clasts possibly indicating the degree of induration of the mud. Similar intra-

clastlc intervals occur in the lower unfossiliferous part of unit III

in the north-central area. Much more discrete intraclasts up to

several inches in diameter occur in thin intervals overlying scour

surfaces in unit II in the north-central area. These tabular and

angular intraclasts are typically identical in lithology to the bed beneath the scour surface, but are quite distinct from the enclosing matrix. They probably represent fragments of well lithified carbonate mud substrates which were eroded by stozm generated waves. Beds of packed

smaller and better rounded intraclasts also occur in unit II. These beds probably represent accumulations of small current and/or wave transported and abraded intraclasts. Small rounded intraclasts also occur in the very sandy bed3 in unit II in the north-central area.

Pellet olds: The term "pellfitold” is used here in a purely descriptive sense for all spherical to oblong grains of cryptocrystalline to iricrocrystalline carbonate which lack discernible internal structure and are less than 0.15 run in size, except for those similar appearing grains which unquestionably represent micritized or re crystallized biocners. Pelletoid3 are thus of diverse origin and include possible

fecal pellets, small intraclasts, and hydro dynamically produced mud aggregates. They are most conspicuous in unit II in the north-central area where they occur packed together in calcarenite beds up to 3 ft thick, usually in association with intraclasts. Many of the pelletoids in these beds have thin dark rims which may represent algal coatings.

Possible pelletoids of fecal origin occur in the lower parts of 3 6 intra-aUochemlcal voids in unit III (Figure 6). The lade of evidence of such possible fecal pellets In the inter-ailocherrlcal areas of muddy unit III rocks may be due to the effects compaction and re crystal­ lization. Pelletoids were not observed in units I, IV, or V, or in unit II in the south-central area.

Matrix

As used in this study "matrix" includes all particles less than

0.02 rrm in diameter and thus corresponds to the "lime mud" of Dunham

(1962). The terms "muddy" and "matrix-rich" are therefore used here syncncmously. Matrix includes materials of diverse origins such as physicochemically precipitated lime mud (nicrite), ccsipacted pelletoids, finely ccnxrdnuted skeletal debris, and clay- and fine silt-sized terrigenous particles. Because of the varying degrees of compaction, re crystallization, and dolomitization in different units and facies a detailed study of the matrix was not made. In general, however, a distinction can be made between those muddy rocks in which much of the matrix consists of skeletal calclsiltlte and those in which there is little or no evidence of such finely comminuted skeletal material.

The former are dominant in units IV and V throughout the outcrop belt and in the lower part of unit III in the south-central area. Hie latter are dominant in unit III in the north-central area and in units I and

II throughout the outcrop belt.

& * £ : "Spar" is a descriptive term for all transparent to transluscent crystals of calcite greater than 0.02 rrm in diameter which are not of 37

Figure o: Photomicrograph of pelletoids of possible fecal origin partially filling the lower part of a corallite, the upper part of which is filled with drusy calcite spar cement. Note the partial replacement of the calcitic coral wall by spherical masses of chalcedonic authigenic quartz. Facies III:5.» Locality U. Scale equals 0.5 ran. biologic origen* Two major genetic type3 of spar were recogpized, drusy spar cement and neanorphic (replacement) spar. Only the former is actually a primary component, but 3ince the two types are sometimes similar in appearance and difficult to distinguish they are both discussed in this section.

Drusy calcite spar cement is calcite spar that was precipitated in primary depositional voids and dlagenetic voids. It is most abundant in the upper part of unit III throughout the outcrop belt where It occurs as mosaics of clear colorless equant crystals up to 5 nra in diameter 'which fill both the inters and intra-allochemical primary depo3itional voids in matrix-free grain supported fossiliferous calcarentie3. In most cases each biochem appears to be enclosed by a single spar crystal and the spar crystals Join along straight to slightly curved sharp contacts. Similar, but volumetrically less abmdant spar cemented fossiliferous calcarcnites occur in each of the other units.

In the muddy fossiliferous rocks in each unit drusy calcite spar either partially or completely fills intra-allochemical voids and shelter voids. In many of the corals in unit II in the south-central area two generations of drusy calcite spar fill the corallites

(Figure 7). The first generation is a crust of blade-like crystals seldom over 1 rnn in length which lines the corallite walls. It Is succeeded by a generation of coarser equant spar crystals which increase in dianeter toward the center of tine corallite, Drusy calcite spar cement also fills a variety of dlagenetic voids in unit I in the south­ central area and unit II in the north-central area. This spar 13 39

Figure 7: Photomicrograph of a corallite filled with two generations of drusy calcite spar cement. Facies 11:2, Locality MCT, Scale equals 0.5 mm.

A. First generation of small tooth-like spar crystals lining the corallite walls.

B. Second generation of larger semi-equant spar crystals which completely fill the corallite. typically white, but clear, and consists of equant crystals up to approximately 25 ran in diameter. Where such spar fills leached fossil molds the lower portions of the spar masses are typically darker in color due to the presence of internal sediment.

Neomorphic spar is spar formed by the recrystallization of matrix.

Two types of necmorphlc spar were recogiized. Tire first consists of syntaxial gralrv-grov/th riirs on biochems, especially echinoderm fragnents.

Tness grain-growth rins only occur in grain supported rocks and are especially conspicuous in the upper part of unit III in the north-central area, in which the matrix has in places been virtually entirely re­ placed by spar. Usually, however, the neomorphic spar can be differenti­ ated from spar cement by the "dirtier" appearance of the former. Mo3t synt axial grain-growth rims also have irregular and serrated appearing contacts with one another, in contrast to the sharp even contacts of spar cement crystals.

The second type of neomorphic spar occurs only in unit I, It consists of Irregular, ramifying masses and.networks of white polkiolotopic calcite spar in a brown dolostcne host rock. Its replacement origin is evidenced by the "floating" quartz sand grains which it in places contains. Except for the irregular shape and polkiolotopic fabric this neomorphic spar is identical in appearance to the drusy spar cement which fills solution enlarged fossil molds in the same lithology. ill

SEDIT-IENTARY STRUCTURES

Mechanical Sedimentary Structures

Ifechanical sedimentary structures are those structures produced

during deposition or early diagenesis which are not related to cr^tnic

activity. The most common mechanical sedimentary structure is horizontal

stratification. It is best developed in unit II in the narthrcentral

area where frequent abrupt vertical changes in mineralogy and lithology

have resulted in numerous distinct vertical intervals in each section

ranging from thin laminae to beds several feet thick. Horizontal

stratification i3 also well developed in parts of unit V in the south-

central area due to the alternation of recessive weathering shaly inter­ vals up to several feet thick. In the fossiliferous rocks of all the units horizontal stratification is generally not well developed because

of deposition having been uniform for rather long periods of time and/or intensive biogenic homogenization of the sediment. Some of tire mud-free grain supported fossiliferous calcarenites in unlt3 I, II, and

V are crudely cross-3tratified, as are some of the intraclastic and pelletcical calcarenites in unit II in the north-central area. A numer of other mechanical sedimentary structures occur in unit II in the north-central area which were not observed elsewhere including

current ripple marks, contorted laminae, dessication cracks, and

fenestral cavities. The latter are irregular shaped horizontally elongate voids up to 1,5 in, lcng, most of which are filled with drusy

spar cement. Shinn (1968) noted that such voids are common features in the supratidal zone of modern carbonate environments, and proposed that they are produced by dessicaticn and escape of gases from carbonate mud which Is subaerial ly exposed soon after deposition. Thus, since the fenestral voids in unit II are mo3t coirmon in the upper few inches of beds which are truncated by Irregular surfaces (Figure 8) they may have also formed during brief periods of sub aerial exposure.

Discontinuous sedimentation, early llthification, and possible subaerial exposure are also indicated by "discontinuity surfaces" which occur in units III, IV, and V, especially in the south-central area. Jaanus3on (1961, p. 221) defined a discontinuity surface in limestone as "a distinct surface vriiich indicates a break in the sequence" that "mostly shows signs of etching, boring activities of organisms, or both." Discontinuity surfaces ("hardgrounds" of

Bathurst, 1971, p. 39^-396) thus are indicative of llthification of the substrate prior to deposition of the overlying sediment. The two major problems with regard to discontinuity surfaces (hardgrounds) are their identification and determination of whether the llthification tocr: place subaerially or in the submarine environment (Bathurst, 1971).

The discontinuity surfaces recognized by the author in the upper part of zr.e Devonian carbonate sequence in central Ohio are quite diverse in appearance, and thus also probably in origin. They range from srrocon undulating surfaces which truncate large fossils and which may be under- and overlain by identical rock types to irregular pitted and corroded appearing surfaces which may be coated or indurated with iron oxide material and which in most cases are under- and overlain by distinctly different rock type3 (Figure 9)# Most of the discontinuity surfaces are penetrated by small vertical borings and many are overlain 43

Figure 8 : Spar-filled fenestral voids below possible exposure surface. Facies II:3> locality C. Figure 9: Discontinuity surfaces (hardgrounds) in the upper part of the Co hers us limestone. Locality AA.

3. Bored and iron-oxide indurated and coated discontinuity surface which lies 6-18 in. above the base of unit IV in Franklin and Delaware counties.

A. Smooth, gently undulating discontinuity surface which truncates large fossils in the underlying fossiliferous packstone and grainstone. Facies 111:5. This surface forms the unit III-unit IV contact. by concentrations of bone material. The two most prominent discontinuity

surfaces can be traced throughout central Chio, although they differ

in appearance somewhat from place to place, and since they coincide

with distinct Ihunal and/or lithic breaks form inter-mit contacts

(the units III-IV and mits IV-V contacts). These two lnter-init

discontinuity surfaces are discussed in detail in the section on

Analysis of Ihter-mit Contacts. The other discontinuity surfaces are

discussed in the section on Facies Analysis.

Biogenic Sedimentary Structures

Burrov/3 are the most common biogenic sedimentary structure, being conspicuous almost everywhere except in unit II in the north-central area. In muddy rocks the burrows range from rather indistinct color swirls and mottles to discrete sub-horizontal and horizontal sediment filled tubes 15) to an inch in diameter. The latter are especially conspicuous in unit V in the south-central area. The most intensive bioturcation appears to have taken place in muddy grain supported fossiliferous calcarenites such as those in the upper part of unit III in the south-central area. These calcarenites occur in thick beds in vrich there is little or no evidence of primary stratification, and are penetrated by partially dolcmltized anastomosing networks of skeletal calcisiltite which surround elongate lenses of leas intensely blot urea ted material (Figure 10). Such intensive bio.turbation resulted from the thorough "mining" of the substrate by sediment ingesting in- faunai organisms as the sediment accumulated. In sane places in the upper part of unit III thin intensely burrowed fossiliferous calcarenite Figure 10: Intensely burrowed fossiliferous packstone-grainstone. The ligit -colored networks consist of partially dolomitized skeletal calcisiltite. Facies 111:5, Locality U. intervals alternate with non-burrowed calcanenite intervals. Since the ncn-burrowed intervals grade upward into the burrowed intervals, which are in turn abruptly overlain by the succeeding non-burrowed interval, it is possible that the alternation is at least partially the result of biogenic grading, the burrowed intervals perhaps repre­ senting times of slower sediment accumulation when the substrate could be more thoroughly modified by burrowing organisms. The upper few inches of units II and III are in places penetrated by vertical burrows up to an inch in diameter which are filled with the basal sediment of the overlying unit (Figure 11), however.

Most of the discontinuity surfaces in units III, IV, and V are penetrated by small vertical borings up to 20 rrm long and 6 inn wide which may be filled with small blochems, matrix, drusy spar cement, or pyrite (Figure 12). These borings truncate both grains and matrix, indicating that the surfaces were indeed lithified. Bored coral and brachiopcd fragments not associated with discontinuity surfaces were also obaserved in units III, IV, and V.

Laminated eryptalgal structures (algal stromatolites) formed by one trapping of carbonate irnd by rrucilagenous blus-grean algal macs occur in unit II in the north-central area. These structures range from, intervals of horizontal, but microcrenulated to undulating parallel laminae to Isolated concentrically laminated head-like domes and finger-like structures up to 8 in. high (Figures 13, 14). 48

Figure 11: Vertical burrows penetrating the unit IV-unit V contact. Locality T.

B. Fossiliferous wackestone-packstone containing black t!bone" fragnents (Facies IV:2).

A. Fossiliferous wackestone-packstone (Facies 111:5) penetrated by burrows filled with the overlying "bone11- bearing wackestone-packstone of Facies TV:2. 49

Figure 12: Photon! crograph of a boring penetrating an ircn-oxide indurated discontinuity surface. Note the truncation of biocbems by the boring, which is filled with iron oxide indurated mud and biochems. Facies IV:2, Locality AA. Scale equals 1 mm. 50

C.6/:^5+:76.25+29D

figure 13: Horizontally laminated algal stromatolite. Eacies 11:3, Locality F. Scale Is in cm. 51

Figure 14: Dornal algal stromatolite. The ndome,f is 7 in. higfi and is burled by pelletoidal packstone. Facie 11:3, Locality BE. 52

CARBONATE ROCK TYPES

The pre-diagpnstic composition and texture of carbonate sediments reflects the hydrologic, biologic, and chemical conditions which pre­ vailed in the depositional environment in which they were formed. Since textural variation is greater than variation in allochem ccnpositicn in the Devonian carbonates of central Ohio the scheme of Dunham (1962), which emphasizes depositional texture, was U3ed as the basis for classifying carbonate rock types. To differentiate subvarieties size and compositional modifiers similar to those used by Folk (1962) have been prefixed to the basic textural name. Except for bounds tone, which is present only at a few places in unit II, each of Dunham's basic textural types is present In each of the unit3. Because of the cofirm gradational inter-bedding of closely related rock types and the fact that intensive dolomitization, bioturbation, or neomorphic grain growth makes determination of the original depositional texture of portions of seme units difficult, it Is virtually impossible to precisely show the distribution of the original textural types.

Instead, it is both mere practical and convenient to show the distrlbu- ticr. of the rocks types containing much skeletal debri3 (skeletal-rich vackestcnos and mudstones) as is dene in Figure 15. Although each of these broad groups of rock types are represented in each unit the v e r y fossiliferous types are dominant in units III and IV and the less fossiliferous types are dominant in units I, II, and in most of the exposed part of unit V. 53

figure 15: Cross section showing the distribution of very fossiliferous rock types (grain-rich wacke stone, packstone, and grains tone) and less fossiliferous rock types (mudstone and grain-poor wackestcne) in the Devonian carbonate sequence in central Ohio. Jr ui SILURIAN NORTH-CENTRAL AREA mi GRAINSTONE GRAIN-RICH WACKESTONE, PACKSTONE, AND MUDSTONE AND GRAIN-POOR WACKESTONE i i ' ------SOUTH-CENTRAL AREA I _____ 1 DEVONIAN SHALE HORIZONTAL SCALE-MILES -20 - 0 ------r 40 r I VERTICAL 0 0 10 20 SCALE-FEET l x Figure 15 CHAPTER IV

DIAGENESIS

GENERAL

Diagenesis wa3 defined by Murray and Pray (1965, p. 1) as "those natural sediments wliich occur in sediments or sedimentary rocks between the time of initial deposition and the time, if ever, when changes created by elevated temperature, or pressure, or by other conditions can be considered to have crossed the threshold into the realm of rnetamorphism." Different parts of the Devonian carbonate sequence of central Ohio have been subjected to various kind3 and varying degrees of dlagsnetic modification. To facilitate discussion these processes have been grouped into five classes: biologLcal diagenesis, lithifica- ticn, dolcrnitizaticn, calcitizatioa, and silicification.

BIOLOGICAL DIAGENESIS

In many instances the earliest modification of the sediment resulted from the activity of deposit feeding infaunal organisms. Ihese organisms altered the original depositional texture of the sediment both by their movement through the sediment, which caused breakage and reorientation of skeletal particles, and by their ingesting of the sediment, which resulted in the conmlnution of skeletal narticles and 55 the production of fecal pellets. As a result of these processes the burrow-filling material in very fossiliferous rocks is generally much finer grained than the surrounding nan-burrowed material. In many

Instances this finely ccmninuted burrow-filling material served as a locus for later dolomitization and/or silicification.

Microscopic boring algae may also have played a role in the modification of skeletal particles. This I3 suggested by the fact that in some grainstcries, especially those in unit III, many of the smaller bryosoan and brachiopod fragments appear as barely Identifiable masses of dark mlcrocrystalline calclte and many of the larger fragments have dark .micritic rims (Figure 16). Although this "mlcritization11 of biochens may merely represent a physico-chemical inversion process, marginal micritization of skeletal particles by boring endolithic algae has been documented in many areas of modern shallow water carbonate sedimentation (Bathurst, 1956; Kendall and Skipworth, 1969; Taylor and Tiling, 196$; Swinchatt, 1969; Perkins and Halsey, 1970), and

Eatnurst (1965) has suggested that micritic rims on mollusk grains from some Jurassic carbonates in England may represent micritic fillings of minute algal boring3. Thus, it is plausible that the rriiricized particles in the unit III grainstonas originated in the same way, the smallest grains being thoroughly bored and replaced by micrite so that they became pseudo-pelletoidal in appearance, whereas only the margins of the larger biochems were affected. 57

Figure 16. Photcrrlcrograph of fossil fragnents with micritized rims. Facies 111:5, locality U. Scale equals 1.0 mm. 58

L F K H F I C m O N

As used here "littiifl cation" refers to the changing of the

originally deposited unconsolidated sediment, which consisted of a mixture of solid carbonate phases containing aqueous intergranular pore solutions, into a low porosity rock composed of low-magiesian calcite.

Tiiis change was brought about by a number of processes, such as com­ paction, pressure solution, neomorphic grain growth, and cementation, the precise nature, relationship, and timing of which are not yet completely understood, even in modem carbonate sediments. Thus, for carbonates of Devonian age detailed analysis of the various processes which resulted in llthification is virtually impossible.

The TiKjat cbvious change that took place in the Devonian carbonates of central Ohio during llthification wa3 the reduction of primary depositional voids by cementation and compaction, for there is essenti­ ally :;a porosity in any of the ncn-thoroughly dolaidtized rocks. These primary depositional voids included inter-allochemical voids in mud-free grain-supported sediments, intra-allochemical (organic) voids, and shelter voids, all cf which are today filled with drusy calcite spar cement. The carbonate muds also probably had an initial high inter- granular porosity and because there is a lack of compaction features in the matrix-rich recks of most units it is probable that the micros­ copic pores in the carbonate mud were cemented into a rigid framework soon after deposition, prior to burial by younger sediments. In the slightly argillaceous mudstcnes and wacko stones of unit V, however, delicate micrefossils and even tentaculites are compressed, suggesting 59 that the relatively high clay content nay have resulted in compaction

of the carbonate mud before intergranular cementation could take place.

The calcium carbonate cement needed to fill the primary

depositional voids probably cane from both internal and external sources.

Since stylolites are very conspicuous througiout the sequence one

internal source of calcite cement may have been calcium carbonate re­

leased as a result of pressure solution. That stylolites can form

prior to or during llthification and thus themselves be a source of

cement was demonstrated by Oldershaw and Scoffin (19o7) and Amstutz

and Park (1967). Another possible internal source of calcite cement

might have been excess calcium carbonate released by the conversion of

ite tas table aragonite, which in some facies may have originally formed

much of the carbonate mud, to stable low-magnesian calcite during early

diagenesis. In those fhcies in which there are indications of numerous

periods of nctv-depcsition a c slow deposition It is also possible that

at least some of the cementation may iiave occured as a result of pro­

longed exposure of the substrate to sea water supersaturated with

calcium carbonate. Such submarine llthification of the sea floor has

beer, reported by Shinn (1969) and Taylor and Tiling (1969) to be occur­ ring today in same areas of slow sedimentation in the Persian Gulf.

Bathurst (1971, p. ^AO-442) has shown, however, that neither this or

any ether known processes could have yielded the amount of calcite needed to fill the original porosity in most limestones and concluded that

"the true process must be simple and ubiquitous, but at the moment is entirely elusive." 60

DOI/X*HTIZATICM

Most of the dolesnite In the Devonian carbonate sequence of

central Ohio is a post-lithiflcation (secondary) diagenetic product.

This is indicated by the fact that everywhere except in unit II in

the north-central area the dolomite occurs as predominantly

oentlirlcrcn-sized euhedral crystals with dark centers and clear rims

which partially to completely replace calcitic matrix, biochems,

neomorphic calcite spar, calcite spar cement, and even chert in rocks

which contain normal marine fossils and show no evidence of supratidal

accumulation. Hie r/icrocrystalline dolomite wnich occurs in unit II

In north-central Ohio may represent synssdimentary (peneccnteirporaneous)

doloritisation as a result of the very early dla^netic reaction of

aragonitic or calcitic mud with Mg-rich brines produced by such near

surface processes as capillary concentration (Illing, Wells, and

Taylor, 1S65) or re fluxion (Deffeyes, Lucia, and Vfeyl, 1965), hcwever.

This is suggested by the micro crystalline texture of the dolomite, the

fact that the microcrystalline dolostone beds typically alternate with

more calcitic mudstone beds, and the presence of shallow water sedi­ mentary structures and mold3 of gypsum crystals.

7re processes involved in the secondary dolondtlzation are uncer­

tain. According to classic concepts two necessary requirements for +2 secondary dolomltizatlon are pore fluids with a high Mg concentration

and a method of circulating these fluids throught the sediment.

UsdowskL (1968, p. 30*0 showed the average position of equilibirum +2 between calcite and dolomite at about 18 mol percent Mg in solution at 80 C. Oily when this temperature is exceeded will limestone in contact with such solutions begin to alter to dolostcne, and the +2 dolcrrdtization will continue only as long as the Mg concentration of the fluid is sufficiently high. The Devonian carbonates in Chio were probably never buried deep enough to pennit dolcmltizaticn by such a process, however, so it it is probable that some other process not involving deep burial was responsible for the secondary dolanite in these rocks.

One nEchanism of secondary dolomitization which requires neither deep burial or a high Me/Ca ratio was suggested by Badiozamani (1973)-.

According to him the mixing of meteoric ground water with up to 30 percent sea water causes usderaaturation with respect to calcite and oversaturation with respect to dolomite due to the effects of ionic strength on the solubility of these minerals. Thus, limestone brought into contact with brackish waters should begin to alter to dolostcne, even at surface tsirperatures. Badiozamani postulated that during early Paleozoic time such brackish water lenses oversaturated with respect to dolomite would have existed along the margins of emergent craccnic areas and that these dolooitizing lenses would have migrated ir. tire and space in response to relative sea level changes. Using this model he explained the areal and stratigraphic distribution of lire 3 tone and dolostone in the Ordovician Champlainian Series of the

Wisconsin Arch region. As will be demonstrated later in this study, the present area of the Findlay Arch in western Chio was probably emergent during several periods of upper Lower and Middle Devonian time so that it is not unfeasible that the secondary dolomite In the Devonian carbonates in Gilo may also have resulted from dolcmitlzation by brackish water lenses. Uhfortunately, however, the fact that the

Devonian carbonates have been conpletely removed from most of the axial area of the Findlay Arch prohibits conclusive testing of this possibility, although the intensely dolomitized character of the post-Detroit River and pre-Ohio Shale interval in the oulier and the only partially dolomitized nature of the correlative interval in central Ohio suggests that the secondary dolcmitlzation was indeed more intense from east to west.

Whatever the ultimate cause of the secondary dolonltization, the dark centers and clear rims, of the dolomite crystals and the fact that only in the more intensely dolcrnitized rocks are biochems partially or conpletely replaced by dolomite suggest that the dolcmitlzation was accomplished by using local sources of carbonate. According to

Murray (I960) such ”local source dolcxnitization" is dolomitization accomplished by pcre fluids relatively low in total C02 with respect to Ca and and thus requiring dissolution of calcite from beyond the limits of the growing dolomite rhomb to provide the excess carbonate needed because dolomite requires 12-13 percent more carbonate per given volume than calcite and because the replaced volume probably contained scire tore space. “Ihus, the most favorable site for the initiation of such dolomitization is fine calcitic matrix, which has the largest surface area per unit volume and hence is most easily dissolved to pro­ vide the excess carbonate. Qily when the fine matrix is almost conpletely replaced will the dolomite crystals begin to replace the biochems. Secondary dolomitizatlon of this intensity only occured In unit I and in the lower part of unit III In the north-central area. The clear rims of the dolomite crystals were explained by Murray (I960) as repre­ senting inclusion-free dolomite fillings of the high porosity zone3 which must have developed around each crystal as a result of the ex­ cess carbonate they required for growth.

CALCITEZATIOM

Ihe term ’’calcitization" was proposed by Smit and Swett (1969) for the replacement process of dolomite by calcite. It Is sysncncmous with the term ndedolomitizatlon" (Evany, 1967; ds Groot, 1967).

Features suggesting the replacement of dolomite by calcite were observed only in the lower part of m l t I in the south-central area.

Thi3 part of unit I consists of fine to medium crystalline brown dolostone which contains lenses and stringers of well rounded quartz sand grains. The dolostcne consists of a hypidiotqpic mosaic of 0.01 to D.Q6 um euhedrai dolomite crystals, many of which have dark euhedral centers and thin clear rims. Althou^i most of these rhombic carbonate crystals consist entirely of dolomite, staining revealed that in seme places the rims cf the crystals are dolomite, but the dark euhedral nuclei are calcitic. Rhombic carbonate crystals viith dolorritic ©enters and calcitic rims have been cited as evidenoe of ,,dedoloInitization,, by several workers (Evany, 1963; Zenger, 1973), however, to the author1 s knowledge dolomite rims on calcitic nuclei previously have been reported only from the Shell Rock Formation (Upper Devonian) of north-central Iowa by Koch (1970)* who postulated that they also resulted from

"dedolomitization." According to Evany (1967) though* "dedolond.tization"

is caused by solutions with high Mg/Ca ratios reacting with dolomite

crystals to form calcite, the reaction taking place from the outside

toward the center of the dolomite crystal. The reverse situation ob­

served in the lower part of unit I is thus somewhat enigmatic,

although 3ince the dark centered, clear rimmed dolomite crystals are

believed to have been formed by "local source dolomLtization" (Murray,

i960), which produces dolomite crystals with margins depleted in CaCO^

relative to the centers, perhaps the margins of the dolomite crystals may have been less susceptible to calcitization than the centers.

Alternatively, perhaps the clear dolomite rims represent a micro-void

filling cement around thoroughly calcitized rhombs.

Another line of evidence indicating that a post-dolcmitization phase of calcitization occurred in the lower part of unit I are irregular networks and masses of white calcite spar, some of which contain

"floating" quartz grains and hence must be a replacement of the dclxitized matrix.

Experimental work by de Groot (1967) indicates that calcitization of iolomite can take place only near the earth1 s surface because lew

Prr and low temperatures are required. Thus the indications of calcl- tication in the lower part of unit I in the south-central area may . suggest that mid-unit I emergence occurred, at least in that area. SILIPICATION

The buHc of the chert in the Devonian carbonates of central Ohio is probably of secondary replacement origin. This is indicated by the presence of relict carbonate textures in mo3t of the chert bodies, the transecting of large fossils and sedimentary structures by chert, and the bounding of chert bodies by sty loll tes. In some instances such replacement of carbonate by silica may have been initiated before lithlfication as suggested by the deflection of argillaceous laminations around chert nodules and fractures in cLiert nodules ’which are filled with ncn-silicified carbonate matrix. Sane of this early diagenetic replacement chert may have actually originated as interstitial gels similar to those Middleton (1958) suggested were responsible for the cherts in the Devonian Bois Blanc Formation of Ontario. Disruption of such interstitial earlv diagenetic gels, or even perhaps primary silica gels, is probably responsible for the brecdated appearing chert bands in the portion of unit II in the south-central area which coincides with Stauffer’s (1909) zone D. In most cases chertlfication preceded secondary dolomitizatlcn as indicated by the better preservation of fossils in chert nodules than in the dolomltized host rocks and the fact tint most chert nodulss. contain numerous euhedral dolomite crystals whicr. have almost certainly replaced the autliigenic quartz. That dolorite can indeed replace chert has been demonstrated by Walker

(IS52).

Tiie source of the silica in the chert bodies is uncertain.

Middleton (1958) proposed that early diagenetic dissolution of siliceous sponge spicules provided the silica for the chert in the

Devonian Bois Blanc Formation in Oitario. The face that sponge spicules are very rare in the Devonian carbonates of central Ohio, even in very fossiliferous rocks, may be the result of such early dissolution of the siliceous spicules. Furthermore, the only place where chert does not occur is in unit II in the north-central area, which is relatively unfossiliferous. Other possible sources of silica for the chert include colloidal silica produced as a weathering product in emergent areas and carried into the sea by streams and wind-blown quartz silt which was subjected to early diagenetic dissolution. 9

CHAPTER V

FACIES ANALYSIS

INTRODUCTION

Each unit consists of two or more facies which represent the sedimentary record of areally restricted parts of the sea floor where

"environmental conditions causing facies differentiation" were "stable

for a sufficient length of time so that the resultant facie3 were clearly and unequivocably manifest from one place to another"

(Laporte, 1967, p. 08). The facies are defined, and their environments of deposition, inferred, on the basis of their lithology, fauna, physical and biogenic sedimentary structures, mineralogy, vertical and lateral llthologic associations, and, in some instances, diagenetic features,,

Sane of the facies are homogeneous, reflecting prolonged uniform depositicnal conditions. Others are more heterogeneous, however, and consist of an interbedded record of several intimately related coexisting subenvironments.

Most of the facies intervals are laterally continuous for considerable distances and this fact, along with the general lithologic character of the rocks themselves, suggests deposition on a gently sloping shallow sea floor of low relief. Most fhcies show lateral gradations, and in some cases complete transitions, into other facies, 67 however, Indicating that regional variations in water circulation and

agitation occurred across the broad shallow sea. Models of carbonate

sedinentation in "clear water" epeiric seas in which regional variations

in water agitation and circulation, and hence sediment types, are attributed to the relationships that different relative depths would have had to the position at which epeiric waves and currents iirpinged on the sea floor and liad their energy dlssapated by friction have been presented by Shaw (1963) and Irwin (1965). Ihese theoretical models served as the starting point for the author* s environmental interpreta­ tions of each facies.

It is emphasized that facies have been defined independently far each unit, even though nost of the basic llthologic types occur in each unit and probably represent equivalent sedimentologlc responses to similar depositional conditions. No two similar facies in different units are precisely analogous, however, so that a generalized treatment of facies for the entire sequence would have tended to minimize strati graphic and sedimentologlc differences between the units.

FACIES OF UNIT I

Unit I is everywhere the oldest unit in the Devonian carbonate sequence of central Ohio. It ranges in thickness from 8 ft at the southernmost locality (locality HM in Pickaway County) to approximately

100 ft at locality MH in the north. Unit I is best exposed in Franklin and Eelaware counties where it is approximately 30-35 ft thick. In the north-central area only the upper few feet of unit I are exposed,

hov;ever, at localities B, F, and BE in the north-central area cores

which penetrate most or all of the unit were studied.

'Ihe contact of unit I with the underlying laminated and

brecciated microciystalline dolostones of the Silurian Ba3S Island

Group is a disconformity which coincides with the "basal Kaskaskla

surface” of Summerson and Swann (1970). This surface is very irregular

and karstic appearing in places, with the sinks and crevices being

filled not with the basal very sandy unit I material, but with red

clay which contains angular fragments of the Silurian dolostcne, rounded quartz sand grains, and scattered dolomite rhombdhedra (Figure

17). This red clay material predates the Initiation of unit I

sedimentation and may represent a paleosol, as was suggested by

Sumners on (1959).

Differentiation of unit I into facies was scxnewhat hampered by the limited number of exposures of the unit and by the intensive

doicnitization portions of it have undergone. Three facies have been recogiized, however, the distribution of which are shown in Figure 18.

Facies 1:1 — Basal Sandy Dolostone Facies

Distribution: Facies 1:1 forms the basal 5-10 ft of Unit I everywhere except at locality HM in Pickaway County. In the Franklin

County area facies 1:1 coincides with Stauffer*s (1909) zone A and the lower few feet of his zone B. In the north-central area facies 1:1 coincides with Kerr's (1950) "Sylvania Sandstone" and the lower sandy portion of his "Airhertsburg Dolomite 70

\

Figure 17: Contact of sandy conglomerate.at base of unit I (B) with the Silurian Bass Islands Dolomite. (A). Ihe'reddish material is sar.dy clay which fills in solution cracks in the Silurian dolomite. Figure 18: Cross section of Unit I showing distribution of facies.

• + +T + • Ottawa i i i i+♦+ +!+ ++ •» i n m m m fVX ■ \ i ++ + + * NORTH-CENTRAL * AREA CQ Seneca U1 Crawford UNIT I-UNIT II CONTACT Marl on Marl CORALLIFEROUS CRINOIDAL GRAINSTONE FACIES FACIES OF UNIT I D0L0MITIZED MUDSTONE-WACKESTONEBASAL SANDY D0L0ST0NE FACIES FACIES C o . iwi O >. Del aware Del o o o 1:2 SQUTH.-CENTRAL'AREA h -V5 o u C o . Frankl1n SILURIAN BASS ISLAND GROUP O 0 O r 40 r VERTICAL SCALE-FEET

Figure 18 / Description: Facies 1:1 consists of grayish-brown fine to medium

grained dolostone which contains much well rounded, fine to medium

grained quartz sand. In the north-central area the quartz sand is

fairly evenly distributed throughout a hypldiotopic mosaic of dark

centered, clear rinmed dolomite crystals with much intercrystalline

porosity. The facies 1:1 dolostone in the Franklin Comty area is

finer grained and less porous, and is also typically bimodal, consisting

of a dense microciystalline dolomite groundmass with scattered euhedral

dolomite porphyrotppes up to 0,08 nra in diameter. The quartz sand also

tends to be concentrated in distinct lenses and stringers in facies

1:1 in the Franklin County area. The greatest concentration of quartz

sand is in the basal 2-4 ft of the facies, which at most places also

contains abundant well rounded clasts of the underlying Silurian

dolomite up to 0.8 ft in diameter (Figure 19). At a few localities discontinuous lenses of white orthoquartzitic sandstone up to 10 in. thick also occur at the base of facies 1:1.

The basal conglomeratic part of facies 1:1 in the Franklin Comty

area grades upward into 4-8 ft of rather heterogeneous sandy dolo3tcne

containing discontinuous leases of laminated mudstone, mud-lunp breccia beds, ar.d cro3s-stratified sandstone lenses. Some of the less sandy beds of this upper facies 1:1 interval are also burrow mottled and

contain poorly preserved fossil mold3 and/or fossil "ghosts,” which

suggsst that such beds may have originally consisted of wackestone

(Figure 20). Most of the fossil molds, of which corals are the most evident, appear to be solution enlarged and are filled with white 74

Figure 19: Negative thin section print of the lower conglomeratic portion of facies 1:1 (Basal sandy dolostcne facies). Note the well-rounded clasts of Silurian dolomite. The small dark black grains are detrital quartz grains. The matrix consists of microcrystalline dolomite containing scattered centimicron sized euhedral dolomite porphyrotopes. Locality MCS. Scale equals 5 mm. 75

Figure 20:. Negative thin section print of the upper portion of facies 1:1 (Basal sandy dolostone facies). Note the "ghost"-like biochems and the interval of concentrated quartz sand. The irregular dark area in the upper part of the photograph is drusy calcite spar filling an irregular diagenetic void of uncertain origin. Locality MCT. Scale equals 10 mm. calclte spar. Similar spar containing "floating" quartz grains occurs in Irregular ramifying masses throu^iout the dolostone. This polkiolotcpic spar is almost certainly of post-dolomitization- replace­ ment origin.

Interpretation: Facies 1:1 represents the oldest record of deposition in the sea which transgressed the emergent ba3al Kaskaskia surface in central Ohio during late Emslan time. The preservation of residual paleosols only in crevices and sinkholes in the upper surface of the eroded Silurian Bass Islands Group, the absence of a basal record of lew energy, nearshore muddy sediments, and the 3andy and conglomeratic nature of the lower part of facies 1:1 suggest that the initial Emsian trangression was so rapid that the paleosols and aeolian sand deposits which had probably accumulated at mo3t places on the emergent surface were subjected to intensive reworking in the agitated near wave-base zone of the transgressing sea, the sand and lithic

•fragments being incorporated into the basal unit I sediment. Only where tbs paleosols filled in cracks and depressions in the basal

Kaskaskia surface were they protected from this intensive reworking and preserved. The general upward decrease in the abundance of quartz sand in fhsies 1:1 probably reflects progressive deepening of the sea and hence increased distance from the near wave base zone of the sea where the sand was being reworked. The absence of facies 1:1 at locality HM in Pickaway County and the irare heterogeneous nature of facies 1:1 in the Franklin Comty area than in the north-central area suggest that during early unit I time the shoreline became stabilized near the southern end of the outcrop belt so that there facie3 1:1 consists of the Interbedded record of a ccoplex mosaic of diverse, but Intimately related nearshore subenvirorunents.

Facies 1:2 — Dolomltised Muiatcne-Wackestone Facies

Distribution: Facies 1:2 is the dominant facies of unit I north of Pickaway County, It everywhere gradationally overlies facie3 1:1 and extends upward to the unit I - unit II contact, ranging in thickness from approximately 25 ft in Franklin County in the south to approximately

80-90 ft in Ottawa County in the north.

Description: Facies 1:2 consists largely of massive, fine to medium grained brown dolostone which in thin sections can be seen to consist of a hypidiotqpic mas ale of micron- to centimicrcn-sized euhedral dolomite crystals with much intercrystalline porosity (Figure 21),

Many of the larger dolomite crystals have dark centers and clear rims.

In the north-central area facies 1:2 contains many unfos3iliferous white chert nodules. Chert is less abundant in the south-central area; however, the few chert nodules that do occur in facies 1:2 in that area are typically packed with the silicified skeletal remains of small corals, brachiopocb, echinoderms, and ramose bryozoans, the latter being especially abundant. Intervals containing small unidentifiable fossil molds also occur throughout most of facies 1:2 in the south- central area.

One of the most conspicuous features of facies 1:2 are dark colored, horizontally elongate "spindle"-shaped areas up to 1.5 in. long and 78

Plgure 21: Photomicrograph of porous dolomitized mudstone of facies 1:2. Locality B. Scale equals 0.2 mm. 0.5 in. thick. These mottles occur in great abundance In soms Intervals* giving the dolostone a crudely stratified appearance. They differ from the surrounding limiter colored dolostone only in having a some­ what greater content of fine Insoluble material. They most likely represent horizontal burrow mottles, although It is possible that they could be "pseudoclasts11 formed by the compaction, flowage, and separation of mors argillaceous laminae.

The upper 6-10 ft interval of facies 1:2 is everywhere much more heterogeneous than the lower portion of the facies and contains such features as interaclastic breccia bad3 (Figure 22), undulating band3 of black hydrocarbon-rich doloatcne, calcite filled solution enlarged coral molds, lime mudstone beds (the latter oily in the north-central area). At locality HM in Marion County this upper heterogeneous portion of facies 1:2 overlies a sharp irregular surface which terminates the underlying Interval of unfo3siliferous massive dolostone (Figure 23).

The fine insoluble residue content of facies 1:2 ranges from

0.5 to 6 percent, averaging 2.6 percent. Scattered up to 0.5 in. thick black shaly partings occur throughout the lower massive portion of the facies, however. These shaly partings, like the fine residues, ccn3i3t largely of ill!tic clay with a considerable amount of bituminous material. Well preserved renains of primitive psllophytic plants were found in the lower part of facies 1:2 at localities U and MCK suggesting that some of the fine insoluble material may consist of the carbonaceous remains of land plants which drifted into the sea. Figure 22:. Breceiated bed in the upper bituminous banded portion of facies 1:2 .(Dolomitized mudstone-wackestone facies). Locality U. Scale in cm. 81

Figure 23: Upper part of unit I at locality H. The scale is six feet long.

C. unit II (Facies 11:1).

B. Hydrocarbon banded portion of facies 1:2. The white areas are calcite spar masses which fill coral molds.

A. Massive portion of facies 1:2. 82

Interpretation; lhe lower thick homogeneous dolorrdtized

mudstone portion of facies 1:2 is interpreted as representing deposition

in a low energy* probably below wave-base environment into which there

was negligible influx of terrigenous material. This environment was

established throughout all but the southernmost part of the outcrop

area following the initial stage of late Ehsian trangressicn and was

maintained for a considerable length of time thereafter as indicated

by its considerable thickness. The fact that the chert nodules in

facies 1:2 are much more fos3iliferous in the south than in the north

suggests that the sea probably shallowed and/or became better circulated

from north to south.

Although still representing deposition in a lew energy environment, the upper more heterogenous portion of facie3 1:2 nay possibly repre­

sent deposition in a relatively shallow above wave-base portion of the

sea. This is suggested by the breccia lenses, which indicate occassional

disruption of a semi-11 thified muddy substrate, probably by storm

generated waves. The undulating hydrocarbon-rich bands and the coral

fauna also suggest a somewhat shallower depositional environment

than that envisioned for the rest of the facies. Perhaps such a relatively shallow water low energy environment was established through­ out central Chlo following a mid-unit I period of emergence represented by the irregular surface which terminates the lower more massive part

of facies 1:2 at locality H. 83 Fa.cle3 1:3 — Coralllferous Crlnoidal Grainstcng Facies

Distribution: Facies 1:3 is best developed at the southernmost locality (locality K4 in Pickaway County)* where it forms virtually the entire 8 It thick unit I interval, lhe only other locality where facies 1:3 was observed was locality MCT in Franklin County where a

2-3 ft tiiick bed of the facies which is both under- and overlain by facies 1:2, occurs near the middle of unit I.

Inscription: Facies 1:3 consists of crudely stratified, calcarenitlc to calciruditic skeletal grains tone which in places contains numerous large, usually fragmented and abraded colonial corals and stromatqporoide (Figure 24). The biochems consist pre­ dominantly of disarticulated crinoid remains (80-90 percent), although a few brachiopod ana bryozoan fragments were noted in most thin sections

(Figure 25). At locality HM rround-like accumulations of corals and stromatcporoids were observed at several places in facle3 1:3. The corals are much more abundant than the 3traratoporoids and are quite diverse, though large massive colonial forms are dominant. The srrc-mtoporoids range from thiclc disk-like to large ball-like forms.

I:. tr.e centers of the mound-like accumulations the corals and s;r^a.toporoid3 appear to be in growth position and are sometimes associated with small pods and lense3 of higily conpacted black shale.

Alcr.g the flanks of the mounds, however, tiie corals and stromatoporolds occur in diverse non-growth orientations and many of them are fragmented.

In trie grainstones abraded and fragjnsnted coral fragments oriented with 84

Figure 24: Coralliferous crlnoidal grainstone of facies 1:3 (B) disccnfcnrably overlying the' Silurian Bass Islands Dolomite (A). Note the' large overturned colonial coral in fhcies 1:2. Locality HM. Scale equals 1ft.. 85

Figure 25: Photomicrograph of facies 1 :3. grainstone (B) in stylolitic contact with the Silurian Bass Islands Dolomite (A). All of the biochems shown in facies 1:3 are crlnoid frag- ments. Scale equals 2 mm. their long dimensions parallel to the crude horizontal to sub­ horizontal stratification are quite common.

There is virtually no carbonate rcud in facies 1:3, except for that trapped in the zooecia of bryozoan fragnents. Dolomite is also rare, although in thin sections of facies 1:3 from locality MCT a few centImL cron-sized dolomite euhedra replacing both crlnoid fragments and spar cenent were observed. Except for scattered quartz sand grains in the lower 2-3 in. of facies 1:3 at locality HM there is essentially no terrigenous material in the facie3. Chert was not observed anywhere in facies 1:3 and partially silicifLed fossil fragments are very uncannon. •

Interpretation: Facies 1:3 represents deposition in a highly agitated probably above wave-base area of the sea where the supply of oxygen and nutrients was sufficient, and the substrate firm enou^i, to support an abundant and diverse fhuna of high epifaunal suspension feeding organisms. The author envisions the sea floor in this environ­ ment as having been covered with crlnoid meadows, except for occassional small corals and stromatoporoid mounds. The energy level in this current and wave swept environment was so high that all carbonate mud was winnow-d away, yielding a porous skeletal sand substrate which was in­ hospitable to the nnny normal marine benthonic organisms which preferred a muddier substrate. This skeletal sand was shifted about by the energetic waves and currents resulting in the crude stratification during storms tI'ib light-weight skeletons of the corals were to33ed about and fragmented larger fragments accumulating in diverse orientations on the flanks of the mounds and smaller fragnents being incorporated into the

skeletal sand.

FACIES OF UNIT II

General

Unit II is the most variable in thickness of all the units, ranging

from approximately 0.5-15 ft in the south-central area up to approxi­

mately 50 ft in the north-central area. Three generalized facies

have been recognized in unit II, the distribution of which are shown

in Figure 26. Although it is uncertain whether deposition of these

three facies began simultaneously, as will be discussed in more detail

under Analysis of Inter-Unit Contacts, it seems likely that all three

fhcies were being deposited contemporaneously immediately prior to the

termination of unit II deposition tliroughout the outcrop belt.

Facies H : I — Coral-Stromatoporold Wackestone Facie3

Distribution: Facies 11:1 is present only in the south-central area where it forms all of unit II except in Franklin County, ranging

from 0.5 to approximately 10 ft in thlcicness. It corresponds to

Stauffer's (1909) zone C.

Description: In Delaware, IMon, and liarion counties facies

11:1 appears as a biostromal-llke interval consisting of abundant

large in situ corals and stomatqporoids in a partially dolomitized mat­ rix which contains much fragmented coralline debris and nunerous thin black shaly partings (Figure 27), the latter being mo3t concentrated 88

Figure 25: Cross section of Unit II showing distribution of facies. •o oo I N

LU I I I I I 0£ U. CQ Q- U NORTH-CENTRAL AREA I CQ I to UNIT II-UNIT III CONTACT Marion Co. Crawford Co,Seneca Co; Ottawa Co. FACIES OF UNIT II ' Co SANDY LAMINATED MUDSTONE FACIES CORAL-STROMATOPOROID WACKESTONE FACIES CHERTY GASTROPOD MUDSTONE FACIES o >- I I I I I I I I I =3 S ^=3 O cu ., 1 : 11:2 1 1 11:3 O' to Oo S 2 3= 20 SOUTH-CENTRAL AREA I III I < < Franklin Co. Delaware t 10 HORIZONTAL SCALE-MILES -10 -20 VERTICAL I I L i-0 SCALE-FEET figure 26, 90

Pi gore 27: Coral-stromatoporoid wackestone of facies 11:1. Note the lamir.ar habit of the stromatoporoids (S) and the thin dark bituminous laminae. Locality MCI. Scale in cm. everywhere In the basal 1-4 In. of the facies. Trie corals in facies

11:1 are very diverse and include massive and branching colonial forms

up to several feet in diameter, a variety of smaller tube-like, foliate,

and encrusting colonial forms, and both solitary and branching rugose

forms. Tne stromatoporoids consist mainly of laminated and tabular

forms up to 6 ft long and 0.7 ft thick (Figure 28). In some places thin laminar stromatoporoids which inter finger with the wackestone are so abundant that the lithology is actually stromatoporoid boindstone.

Although almost all of the large corals and stromatoporoid3 are in their original growth locations, most of the slender and more delicate forms are new recumbent and covered with thin bituminous films.

Besides fragmented coralline debris, in some places the wackestone contains small crlnoid, brachlopod, and bryozoan fragments. Macro­ fossils other than the corals and strcmatoporoid3 are rare, however.

Considerable lateral variation occurs within facies 11:1. At one place (locality PY) it is only 0.5 ft thick and consists entirely of unfos si liferous shaly bituminous mudstone. South of Delaware

County facies H : 1 is also less well developed and contains relatively few colonial corals or stromatoporoids. At the northernmost locality

'where facies 11:1 was recognized, locality S in Crawford County, it i3 at least 12-15 ft thick and consists predominantly of burrowed corailiferous mudstone which contains scattered very large in situ corals, semi-nodular stromatoporoids, and several of up to 0.5 ft thick intervals of packed fragmented coral and stromatoporoid debri3. 92

Figure 28 : large round-like stromatoporoids in facies 11:1 Locality U. Scale in in. 93

The fine insoluble residue content ol* facies 11:1 averages 2 . k

percent. Mo3t of the fine residue consists of illitic clay, with

minor amounts of bituminous material and angular quartz silt. Many

of the sanples also yielded a number of rounded quartz sand grains.

Chert nodules were only observed in facie 3 11:1 at locality S and

silicifled fossils not associated with chert nodules are very rare.

Interpretatlon: Facies 11:1 is believed to have been deposited

in a relatively low energy, probably above wave-ba3e area of the sea

where conditions were favorable for the proliferation of a diverse

coelenterate fauna, but apparently inhibited most other organisms.

Hie corals and stromatoporoids indicate normal marine temperatures and

salinities and moderately good circulation so that it Is unlikely tlxat

abnormal physico-chemical conditions were responsible for the general

lack of other normal marine organisms. Instead the great abundance of

the coelenterat.es, which must have virtually "carpeted" the substrate

•in places, bnd/or possibly very low rates of carbonate mud deposition may have been the primary factors tending to Inhibit the other normal marine organisms. That the rate of accumulation of carbonate mud was

indeed px*obably very slow is suggested by tlie numerous bituminous

laminae which are probably concentrates .formed during times of little

or no carbonate mud deposition. Thus, in spite of the abundance of bituminous material the environment of deposition of facies 11:1 was probably very clear and ncn-turbld. At times, however, probably during storms, higher energy conditions prevailed and the more delicate coral

skeletons were fragmented and mixed with diverse skeletal debris washed in from neighboring d e e p e r water environments producing the wackestone intervals. Local sea floor topography probably played a large role in determining the nature of facies II;1 from place to place, the biostro- mal portions of the facies pexiiaps representing relatively high areas of the sea floor which were better lighted and circulated, and those places where the facies is not as well developed perhaps representing relatively deeper and/or more poorly circulated areas.

The author* s environmental interpretation of facies 11:1 is consistent with Laporte's (19o7) Interpretation that similar muddy, stromatcporoid-rich rocks in the Lower Devonian Manlius Formation of

Ifew York were deposited in "shallow offshore lagoonal water.11

Facies 11:2 — Gherty Gastropod Mudstone Facies

Distribution: Facies 11:2 occurs only in Franklin County in the south-central area where it forms almost all of unit II, ranging from

6=12 ft in thickness. It coincides with Stauffer's (1909) zone D and

Wells* (1953) Eversols Member of the Columbus Limestone.

Description: In most places facies 11:2 consists almost entirely of light-brown partially dolomLtlzed mudstone which contains numerous bands cf white chert up to 6 inches in thickness (figure 29). Most of the chart bands are unfosslllferous and some are composed almost entirely of angular to rounded chert clasts up to several inches in diameter.

Scattered dark burrow mottles occur in the mudstone, but otherwise it i3 massive and structureless. The mud3tone Is composed of a hypldiotopic mosaic of dark centered, clear rinmed dolomite crystals which have 95 SNL SUC FR L YU LAbUKM YOUH ALL FOR SOURCE SINGLE A

Figure 29: Chert gastropod mudstone of facies 11:2. Note the concen­ tration of fragmented skeletal debris. Locality MCT. Scale in cm. replaced a large portion of a recrystallized calcitlc matrix. Many

angular to subrounded quartz slit grains are scattered tlirou^iout this

matrix.

Small gastropods are the dominant fossils in the cherty mudstone,

Wells (19^7) noting that over thirty 3pecies tiad been recorded from

the Eversole Member. These gastropods occur throughout the facie3, but are best preserved in the chert bands. A few of the chert bands

also contain the fragmented skeletal remains of brachiopods, crlnoid3, trllobites, solitary rugose corals, bryozoans, and cephalopoda. Since most of the chert band3 are unfos3iliferou3 except for gastropods, however, it is likely that this diverse skeletal material does not represent the remains of Indigenous organisms, but instead represents allocthcncus skaletal debris.

At locality MOT facie3 11:2 also contains beds of very fossiliferous wackestone, packs tone, and crudely cross-stratified grainstcne up to several feet thick which are interbedded with the cherty, and in some places laminated mud3tcne beds. These fossiliferous beds contain a diverse and abundant normal marine fauna, small massive colonial corals, solitary rugose corals, and diverse brachiopods being most conspicuous

(Figure 30). The sand-sized skeletal debris eonsi3t3 largely of disarticulated crinoid remains, with subordinate brachiopod and bryozoan fragments. Most of the fossiliferous beds also contain scattered rounded quartz sand grains.

The fine insoluble residue content of the cherty gastropod mudstone averages ^.1 percent and these residues consist almost entirely of 97

figure 30: Fossiliferous packstone of facies 1:2. Locality MOT. Scale in in. angular quartz silt. The coarse residues consist entirely of chert

fragnsnts.

Interpretation: The cherty gastropod mudstones of facies II;2

are interpreted as having been deposited in a low energy, probably above

wave-base portion of the sea which nay have been protected from open

marine waves and currents by shallow shoal areas* In this semi­

restricted possibly lagoonal-liks environment conditions were favorable

for the proliferation of diverse gastropod fauna, but other normal

marine organisms were inhibited. During stores, however, the frag­

mented remains of the normal marine organisms which flourished in

more open marine shoaling areas were swept into the area of facies

11:2 deposition resulting in the skeletal debris bands. Ihe brecciated

appearing chert bands in facies 11:2 suggest that conditions may also

have been favorable for the formation of primary or early diagenetic

silica gels which in some cases apparently v/ere disturbed and frag­

mented, possibly during storms, prior to burial by carbonate mud.

The area between the low enex*£y lagoonal-like areas and the agitated

shoal areas probably was a complex mosaic of subenvironments, the

depcsioional records of wliich were interbedded as a result of variations

in vacer energy, probably partially in response to relative mean sea

level fluctuations. Such a transitional area is probably represented

by the interval of intimately interbedded cherty laminated mudstones and fossiliferous rock types at locality MCI. '99

Facies 11:3 — Sandy Laminated Mudstone Facies

Distribution: Facies 11:3 occurs only in the north-central area

where it forms all of unit II, ranging in thickness from approximately

10 ft at locality B in Seneca County to approximately 50 ft a locality

ME in Ottawa County, Facies 11:3 corresponds to the "Lucas Dolomite"

of Kerr (1950) and the "Detroit River beds" of Janssens (1970a),

Description: Facies 11:3 consists of a variety of interbedded,

predominantly muddy and dolomltic rock types which contain the neither

diverse or abundant Detroit River fauna, The contacts of the beds are

generally abrupt and in some cases coincide with distinct planes of

separation. Most beds are light tan to dark brown, but in every section

of facies 11:3 several 19 to 2 ft thick distinct gray-green weathering

Intervals are present which contain much rounded quartz sand (Figure 31),

The non-sandy rock types of facies 11:3 can be grouped into two

classes for purposes of discussion. The first class consists of massive to bituminous banded very fine grained dolcatones. Many of

the massive appearing dolostcne beds contain masses of white calcite

spar up to several inches in size which fill mold3 of sirall brachiopods,

gastropods, and rugose coral3 (Figure 32), Etched slabs of such

fossiliferous dolostcnes also revealed the presence of numerous very

small molds of unidentifiable fossils, suggesting that the original

llthciogy was wackestone. Such intervals of fossiliferous passive

doiostcne alternate with intervals of unfossiliferous dolostone con­

taining thin bituminous shaly laminae or up to 1 in, thick parallel bands of very bituminous doiostcne (Figure 33), These bituminous Figure 31: Typical appearance of facies 11:3 in the field. Locality MH. The scale represents 10 ft.

B. Unit III.

C. Unit II consisting entirely of facies 11:3. The gray- green colored beds contain much quartz sand and are excellent marker beds in individual quarries. 101

Figure 32 : Bed of fades 11:3 dolomitized wackestone (B) containing calcite spar masses which fill solution enlarged fossil molds and burrows (?). Underlying the wackestone bed is gray-green mottled very sandy bed (A). Locality B. Scale in in. 102

Figure 33: Facies 11:3 mudstone containing numerous thin bituminous laminae. Locality. MH. Scale'is in cm. bands and laminae are usually continuous for considerable distances and are undisturbed by either burrows or dessication features. Also included in the first class of non-sandy facies 11:3 rock types is a stromatoporoid bioharm at least 50 ft in diameter and ^ ft thick which occurs at the very top of unit II along the north shore of felly's

Island (locality KI), just north of the Glacial Grooves State Memorial*

This biobarm consists of abundant digitate and nodular massive stromatoporoids in a porous, very fossiliferous, brown dolostone matrix.

Similar stromatoporoids were not observed in facies 11:3 at any other locality. In thin section the brown doiostcne was seen to consist of a padced mosaic of equigranular micron-sized dolomite crystals. The fine insoluble residue content of the brown dolostcnes averages less than 1 percent and the residues consist primarily of bituminous matter and illitic clay. Except for a few rounded quartz sand grains in seme samples there were no coarse residues. Neither chert or silicsted fossils v/ere observed.

The second class of ncn-sandy facies 11:3 rock types is consider­ ably more diverse trian the Ill’st class.' Jh general though, the rock types included in the second class tend to be lighter in color also more variable in mineralogic composition, ranging from line stone to dolostone, than those of the first class. The bulk of the second class consists of unfossillferous laminated rode types, some of which arc almost certainly algal stromatolitic bounds tone (figures 12, 13), whereas other more even laminated beds displaying dessication features and thin lenses of angular "rlp-up" breccia probably are laminated 1 0 4

mudstones formed by purely physical processes (Figure 34), Some of

these laminated mudstone beds contain scattered molds of gypsum

crystals or calclte pseodomoiphs after gypsum crystals (Figure 35)*

In thin sections the algal stomatolitic bounds tones and laminated mud­

stones are generally similar in appearance, both typically consisting

of alternating 0,2-15 uni thick laminae of packed micron-sized dolomite

crystals. The thickest laminae generally consist of the coarsest

dolomite crystals and also may contain scattered angular quartz silt

grains and/or palletoids, Also included in this second class of non-

sandy facies 11:3 rock types are beds of pelletoidal and/or intra-

clastic ealcarenite (Figure 35), which are most conspicuous at

localities F and EE, and lenses of highly calcitic fossiliferous pelletoidal packs tone containing fragments of the branching strcrnatoporold

Amphipora ramosa which occur in the upper part of facies HE:3 at locality C (Figure 37). Many laminated beds are terminated by sharp irregular surfaces beneath which the laminae are contorted and typically ccr.oain fenestra! cavities which are filled with carbonate mud or calclte spar (Figures 8, 38), Hie abindance and conposition of the insoluble residues of the second class of non-sandy facies 11:3 rock types are similar to those of the first class.

The massive and bituminous banded dolostaios dominate unit II throughout north-central Ohio, especially where It is thickest, the laminated and pelletoidal rock types being most abundant in t'ne middle and upper parts of the unit in the Seneca County-Sandusky County area. 105

Figure 3^: Facies 11:3 laminated mudstone. Note the dessication cracks and the intraclastic breccia bed. Locality BE. Scale in cm.

i 106

Figure 35* Calclte pseudomorphs after, gypsum crystals in facies 11:3 mudstone. The matrix is raicrocrystalline dolomite. Locality Be. Scale equals 2 mm. 107

Figure 36: Negative thin section print of facies II:3 pelletoidal packstone-gralnstone.. locality EE. Scale equals 5 mm. 108

Figure 37: Negative thin, section print of facies 11:3 fossiliferous and pelletoidal packstone. The major biochems-are fragments of a ramose stromatoporoids?(A), possibly 'Amphipdra famdsa5 and an auloporid coral (B). Locality S. Scale equals' I'O mm. 109

Figure 38: Spar-filled fenestral voids in facies 11:3 mudstone. Note the dark rounded intraclasts. Locality BE. Scale equals 5 mm. 2he prominent gray-green weathering sanely beds in facies 11:3

serve as excellent marker-beds in individual quarries, but because every

sandy bed shows considerable variation in lithology and sand content

(which ranges from 5-MQ percent) over short distances, and because

there are also typically several le33 prominent sandy intervals in each

section, inter-quarry correlations based just on sandy beds i3 not

possible. I\b3t of the sandy intervals, have been intensely styloll tized

and most contain many pelletoid3 and angular to well rounded Intraclasts

as well, as the rounded quartz grains (Figure 39). AI30 present in

most of the sandy beds are sand size calcite spar porphyrotopes, which

probably represent recrystallized fossil fragments, and scattered

small euhedral pyrite grains. T h e contacts of the sandy beds are in

general abrupt, and the upper surface of one sandy bed at locality F

is ripple-marked and in places displays dessication polygons

(Figures 40, Ml).

Interpretation: The variety of muddy rode types, the presence of current and dessication structures, the highly restricted fauna, and the indications of evaporite minerals suggest that facies 11:3 represents the interbedded record of a complex mosaic of subenvironments

•viiich existed in a broad, above wave base area of shallow water and restricted circulation.

These intimately related subenYirorinents probably developed as a resulc of the conhined effects of topograptiic irregularities and regional variations in water circulation and agitation. Because this area of facle3 11:3 deposition probably lay far beyond the reach of Ill

Figure 39: Photc~dcrograph of sandy bed in facies 11:3. Note the well rounded quartz, grains (A) and small rounded microcrystalline dolomite intraclasts (B) in the' microcrystalline dolomite matrix (C). Locality C. Scale equals 5 mm. 112

Figure 4QRipple-marked sandy bed in facies 11:3. locality F

Figure 41: Ripple-marked and mud-cracked sandy bed in facies 11:3. locality F. open marina waves and currents the major movement of water probably was by storm generated waves and/or density currents. 3h general

though, circulation was poor and this, combined with the shallowness of the sea, led to warm and saline waters from which carbonate mud was

likely directly precipitated by physicochemical processes. The topographically highest areas were subject to frequent periods of emergence as is Indicated by the numerous irregular bedding surfaces immediately beneath which spar-filled fenestral cavities and contorted laminae are conspicuous. Ihe major periods of emergence probably resulted from brief low-stands of relative sea level, however, it is possible that briefer periods of subaexlal exposure could have occurred in some very shallow areas merely as a result of the blowing of water off of the sea floor by intense winds. Soire areas became "ponded" during low sea level stands and in 3uch areas delicately laminated muds accumulated which were subjected to frequent dessication and disruption by storms. At most tliras, however, most of the facies 11:3 environ­ ment was probably a broad shallow lagoonal-like area. In the deepest and/or most restricted parts of this area conditions were probably stagnant, resulting in the accumulation of unfosslliferous laminated and bituminous banded mdustanes which were subsequently dolomitized, possibly oeneconteirporaneously. In soma what better circulated and probably shallower submerged areas the muddy substrate was inhabited by the snails, bracrdopods, small corals, and other merrbera of the

"Detroit River" fauna, the skeletal remains of which accumulated essentially in situ and with little or no fragmentation to form the now • 114 intensely doloniitisad fosslliferous wackestone beds, Hi other probably even shallower areas the substrate wa3 covered by blue-rgreen algal

Fats which trapped carbonate mud, resulting in the formation of algal stromatolites. The wide variety of forms and sizes of these biogenic sedimentary structures probably at least partially reflect variations in strength and frequency of water movement (Hoffman and others, 1969).

Hie distinct sandy beds in facies 11:3 probably resulted from the periodic "tapping" of an emergent aeolian sand covered area by the shallow sea and the spreading of this sand throughout the restricted portion of the sea by storm generated waves and currents, Hie only nearby source of quartz sand would have been the aeolian-marine

Sylvania Sandstone of northwestern Ohio and southeastern Michigan, suggesting that the latter areas were emergent and covered by aeolian sand throughout the time of facies 11:3 deposition in north- central Ohio.

FACIES OF UNIT III

General

Unit III is 30-35 ft thick througiout the outcrop belt. It has leer, separated into five facies, the distribution of which are shorn it Figure 42. Also indicated in Figure 42 is the position of a prxirent sllty-shale bed which is an excellent marker bed in the north-central area.

Facies 111:1 — Brachiopod Wackestone Facies

Distribution: Facies 1X1:1 forms the lower 13-17 ft of unit III throughout most of the south-central area, abruptly overlying either 115

Figure 42:. Cross section of Unit III showing distribution of facies. &

N m & m m m * 1 1 I =C =C •—< I I I Q. O Q. ■mm I U i CQ I IMS* NORTH-CENTRAL AREA I CO Seneca Co. Ottawa Co. UNIT III-UNIT IV CONTACT SKS&fSflW , I CO 4 III * ' ■ ■ t ' 4 11 f a c i e s

1 *■ V » » V *■ »k*'. * ► * *'V V J J V * ► * *'V 4 k k fc f . V v > w 1 * * * 1 w > V v . f v fc i _ F ni I I I I I UJ p a c k s t o n e

Sc o FACIES OF UNIT >- CL. CRINOIDAL PACKjSTONE-GRAINSTONE FACIES BRACHI0P0D WACKEST0NE FACIES b u r r o w e d OHERTY. MUDSTONE-SILTX SHALE FACIES BURROWED MUDST0NE-WACKEST0NE FACIES

t t I I 00 S ° S 00 ZD > 0 „ 0 ’ 0 „ 0 > | — | SILTY-SHALE | BED t

Plgure 42.. 117

facies 11:1 or 11:2 and grading upward everywhere into facies 111:2.

At locality S it is both under- and overlain by facies 111:2. At hcality S it is both under- and overlain by facie3 111:2. In

Pfcanklin and Delaware counties it coincides with Stauffer's (1909) zone E.

Description: Facies 111:1 consists of bluish-gray to brown massive grain-poor wackestone (Figure 43). In some places it is al­ most devoid of macrofossils, but elsewhere it contains diverse macrofauna which in terms of both numbers of species and numbers of individuals is dominated by brachiopods, "Splrifer" macrothyrls being especially conspicuous. Scattered corals also occur in facies

111:1 111:1, a branching rugose form and a very large solitary rugose form being most abundant. Also present are bulbous stromatoporoids up to 8 in. in diameter which have grown around coral and brachiopod nuclei. A few gastropods, pelecypods, and cephalopods were also obser­ ved, small gastropods, pelecypods, and cephalopods were also observed, small gastropods being especially numerous in the lower 0.5-1 ft of the facies where it overlies unit II. Also occurring in the lower foot of facies 111:2 where it overlies facies II are numerous abraded and fragmented facies 11:1 corals and stromatoporoids. Most of the indigenous macrofossils are neither fragmented or abraded, however, and appear to be essentially in situ. In the lower part of facies 111:1 at several localities, though, 1-2 in. thick slightly argillaceous beds occur which contain packed, fragmented and abraded remains of brachiopods, bryozoans, and corals (Figure 44). In the upper few feet 118

Figure ~3: Negative thin-section print of facies 111:1 fossiHferous wackestone. The biochems include gastropods (A), brachiopods (B), and crinoids (C). fest of the matrix consists of skeletal calcisiltite. The small dark round grains are quartz grains. Locality 0. Scale : equals 10 mm. 119

Figure -44: Bedding surface in facies. 111:1 covered with fragnented and abraded skeletal debris. Locality U.. iacr

of facies 111:1 transitional to facies 111:2 stringers of disarticulated

crinoid remains are common.

The muddy matrix of facies 111:1 consists largely of skeletal

calciciltite, although in some sanples up to approximately 50 percent

of the fine calcitic material has been replaced by dark centered, clear

rirrmed euhedral dolomite crystals up to 0.14 mm in diameter. The

fine insoluble residue content of facies 111:1 averages 2.5 percent and

consists largely of illitic clay. Rounded quartz sand grains are

common in the lower 0.5 ft of facies 111:1 at most localities, but

are very rare elsewhere. Chert does not occur in facies 111:1,

although some brachiopod fragments are partially internally silicified.

Interpretation: The moderately diverse and abundant normal

marine fauna and the muddy texture of facies 111:1 suggest deposition

in a relatively low energy, but moderately well circulated portion

of the sea, probably just below mean wave base. In this area much of

the finely corrminuted skeletal debris produced by physical and biological processes in neighboring shallower more agitated environments was

deposited. The soft muddy substrate apparently inhibited sessile high epifaunal suspension feeding organisms such as crinoids and many types of corals, but was very favorable for low epifaunal suspension and filter feeding brachiopods. The thin layers of fragmented and abraded skeletal debris indicate that occasionally the muddy sub­ strate was disturbed by waves, probably during storms, resulting in a sweeping away of carbonate mud and concentration of the coarse skeletal remains. 121'

Facies 111:2 — Burrowed Packstorte Fades

Distribution: An approximately 10-15 ft interval of facies 111:2 forms the middle of unit III in the south-central area. This Interval gradationally overlies facies 111:1 and is abruptly overlain by facies 111:4 in Marion and Crawford counties and by facies 111:5 south of T'ferion County. The lower 3-6 ft contains abundant specimens of

Brevispirifer gregarlus and coincides with Stauffer's (1909) zone F.

The upper part coincides with the lower half of Stauffer's zone G.

A 1-3 ft thick interval of facies 111:2 also occurs at the base of unit III at some localities in the north-central area and at locality

S in Crawford County.

Description: Facies III:2 consists of gray fossiliferous calcarenitic to calciruditic packstone and minor grainstone occurring in massive appearing beds up to several feet thick, many of which are separated by prominent stylolites (Figure 45). The thin interval of facies 111:2 which occurs at the base of unit III at some localities in she north-central area is finer grained and less muddy than the thicker interval in the south-central area and is crudely cross- s t m i f i e d in places. In both area, however, facies 111:2 contains a very diverse and abundant macrofauna dominated by brachiopods, massive colonial and small solitary rugose corals, massive encrusting stromatoporoids, pelecypods, and large gastropods. The presence of an abundant soft-bodied burrowing infauna is also indicated by numerous intensely bioturbated intervals. 122

Figure [15: Polished slab of facies III :2 burrowed packs lone. The large biochems are mostly brachiopod fragnents. Locality U. Scale In cm. 123.

Analysis of thin sections showed that approximately 60-70 percent

of the sand-sized biochems consist of disarticulated crinoid fragments,

with the rest consisting largely of brachiopod, bryozoan, and in-

determinant fragments. Also observed in most thin sections were

scattered trilobite fragments and charophyte oogonia. The latter are most abundant in the lower part of facies 111:2 in the south-central

area. Approximately 10-20 percent of the fine calcitic matrix of

facies 111:2 has been replaced by dark centered, clear rimmed dolomite

crystals and neomorphic calcite spar.

A variety of features occur in facies 111:2 which suggest that

there were frequent slowdowns in the rate of sedimentation, and probably even periods of non-deposition. These include intensely burrowed intervals, semi-continuous bands of black carbonaceous (?) mottles, and smooth undulating discontinuity surfaces which truncate biochems.

The fine insoluble residue content of facies 111:2 averages 1.5 percent and consists almost entirely of illitic clay. Scattered well rounded quartz sand grains occur throughout the facies and are very abundant in the basal 3-6 in. of the facies where it overlies facies

11:1 or 11:3. No chert was observed in facies 111:2, although partially silicifisd small brachiopod and coral fragments are corrmon.

Ir.t e rpret at ion; The abundant and diverse normal marine faune and the muddy grain-supported texture suggest that facies 11:3 was deposited in a clear, well circulated and nutrient-rich portion of the sea, probably near to mean wave base. In this environment the rate of skeletal sand and mud production was very high resulting in the accumulation of muddy, typically packed skeletal sands which were intensely bioturbated by deposit feeding infaunal organisms, resulting in the almost complete obliteration of primary depositional stratification. The grains tone beds and lenses, however, indicate that at times the water energy was sufficiently high to winnow away all of the carbonate mud.

Facies 111:3 — Burrowed Mudstone-Wackestone Facies

Distribution: Facies 111:3 is well developed only in the north- central area where it forms most of the lower 10-15 ft of unit III, either directly and abruptly overlying facies 11:3 or gradationally overlying a 1-3 ft thick interval of facies 111:2. It also grades wouthward into facies 111:2. Facies 111:4 is everywhere terminated by a prominent, surface which is overlain by facies 111:4.

Description: Facies 111:3 consists of greenish-gray to brown intensely dolcmitized mudstone and wackestone which occurs in several thick beds separated by prominent stylolites (Figure 46). Some inter­ vals are crudely stratified and contain discontinuous argillaceous laminae and thin mud-lump breccia intervals whereas others are intensely burrow mottled and "churned'' appearing. Some of the stylolitized bedding surfaces are covered with branching horizontal tube-like burrows and a variety of tracks and trails. At most localities, however, the only evidence of a skeletal fauna are scattered molds of brachiopods and corals (both solitary rugose and massive colonial types), especially in the lower and upper few feet of the facies, and uncommon very Figure ^6: Facies 111:3 burrow-mottled mudstone. Locality F. Scale equals 2 ft. 126

“ragged1* appearing silicified stromatoporoids which occur throughout the facies. At locality MH, however,, facies 111:3 is much less intensely dolomized than elsewhere and consists of grain-poor wackestone con­ taining fragjnented skeletal remains of diverse normal marine organisms as well as scattered bulbous stromatoporoids up to 7 in. in diameter.

Also, the upper 2-3 ft of facies 111:3 at locality MH contains an abundant essentially in situ macrofauna of brachiopods (mainly thin- shelled atrypids and stropheodontids), corals (solitary and branching rugose types and massive colonial types), pelecypods, and large ramose bryozoans.

Thin sections of facies 111:2 show a hypidiotopic mosaic of dark centered, clear rimmed euhedral dolomite cyrstals which have almost conpletely replaced a recrystallized appearing calcitic groundless.

The fine insoluble residue content averages 2.5 percent and consists largely of illitic clay with sorre angular quartz silt. Rounded quartz grains are very rare, having been observed only in the lower few inches of the facies at a ftew localities. Some of the distinct tube-like burrows are replaced by white chert, but in general chert is rare.

Spores and scolecodonts were common in most residues.

Interpretation: Facies 111:3 probably represents deposition in a considerably less well circulated and probably somewhat shallower part of the sea than the likely contemporaneously deposited facies

111:2 interval in the south-central area. In this semi-restricted low energy area an abundant soft bodied burrowing infauna nourished, but at most places and at most times the diverse normal marine fauna 127

of facies 111:2 was inhibited, probably due a wide variety of factors

including low water energy, insufficient supply of nutrients, the muddy, probably somewhat fluid substrate, and possibly high temperature

and/or salinity. In areas of the sea transitional between the facies

111:2 and facies 111:3 environments, however, such as Is probably

represented by facies 111:3 at locality MH, many of the normal marine

skeletal-bearing organisms were able to flourish. In such areas some

of the carbonate mud probably consisted of skeletal calcisilitite.

Elsewhere though, the carbonate mud probably consisted of a mixture of physicochemically produced carbonate and fecal pellets.

Facies 111:4 — Cherty Mudstone-Silty Shale Facies

Distribution: Facies 111:4 forms the middle part of unit III in the north-central area, averaging 15 ft in thickness. In this area It abruptly overlies the surface which.terminates facies 111:3 and is abruptly overlain by facies 111:6. A southward thinning tongue of facies 111:4 extends into the south-central area and is recognizeable as far south as locality PY in ‘Delaware County. At localities S and

HM this facies 111:4 interval is 4 ft thick and has very abrupt lower and upper contacts with facies 111:2 and 111:5 respectively.

Description: Facies 111:4 consists largely of rather intensely dolomitized brown massive mudstone. At most places in the north-central area it can be separated into four divisions, typical development of the lower three divisions occurs at locality F in Seneca County. The lower division consists of 6-7 ft of partially dolomitized brown mudstone which contains discontinuous argillaceous laminae, uncommon

thin-shelled brachiopod fragments, and very conspicuous small black

"wispy" looking burrow mottles (Figure 47). This division, which contains

almost no chert, but grades upward into 11-17 ft of massi.ve partially

dolomitized mudstone which contains much white chert. Most of this

chert occurs in 1-3 in. thick semi-continuous bands; however, some

occurs in small elongate masses which probably represent chertifled burrow tubes. The lowest chert band contains abundant fragmented skeletal debris of bryozoans, brachiopods, corals, and trilobites, as well as uncommon eharophyte oogonia. None of the other chert is fossiliferous, however. The chert is least abundant in the upper

5-6 ft of this division, which, however, contains scattered thin- shelled brachiopod fragments and several 1-2 in. thick carbonaceous mottled bands. The upper division of facies 111:4 at locality F is a 2 inch thick bed of ferruginous stained silty shale which very abruptly overlies the dolomitized mudstone and is abruptly overlain by facies 111:5 grainstone (Figure 48). Thin sections and x-ray diffraction analysis showed that this silty shale consists largely of illicic clay and very fine angular quartz silt (5-20,percent), with small amounts of calcite and dolomite. Washed-and acid treated residues of the silty shale bed yielded, besides quartz silt, flaky black bituminous aprticl.es of uncertain origin, a few silicified crir.cid stem columnals, and numerous spores and scolecodcnts.

Both to the north and south of locality F an upper interval of facies 111:4 dolomitized mudstone intervenes between the silty shale Figure '47: Massive mudstone of facies 111:4 displaying numerous carbonaceous burrow-mottles and discontinuous argillaceous streaks. Locality P. 130

Fi~jire 48: Sllty-shale bed (SS) in facies 111:4. Locality MH. 131

bed, which ranges from 0.5 to 6 in. in thickness, and the grainstones

of facies 111:5. The thin tongue of facies 111:4 in the south-central

area is represented by this post-silty shale interval, the latter being

very thin and occurring at the very base of the facies throughout that

area. This interval of facies 111:4 in the south-central area contains

much white chert and Wright (1975) reported that it contained abundant

chitinozoa compared to the over- and underlying unit III facies. Some

of the chert masses contain the fragmented remains of diverse normal

marine organisms. In the north-central area the post-silty shale

facies 111:4 interval thickens progressively to the north concomitant

with a thinning of the pre-silty shale facies 111:4 interval, the

latter being only 6 ft thick at locality MH where it contains numerous

higi-spired gastropods in the upper 1-2 ft. The post-silty shale inter­

val of facies 111:4 in the north-central area coincides with the

"bottom rock" of Stauffer (1909) and contains poorly preserved remains

of crinoids and bryozoans, suggesting that the lithology may have

originally been wackestone, or possibly even packstone, in some places.

It is much less cherty than the post-silty shale facies 111:4 interval

in the south-central area.

Because most of the calcitic particles which originally formed

the facies 111:4 mudstone have been recrystallized and largely replaced by a hypidiotopic mosaic of dark centered, clear rimmed

dolomite crystals the constituent composition of the original sediment

is uncertain. Thin sections of some of the chert bodies showed packed

rounded grains averaging 0.1 mm in diameter Which probably either 132 represent small rounded biochems or pelletoids. On the basis of their uniform size and the lack of coarser skeletal debris, however, the author believes that these grains represent fecal pellets produced by the soft-bodied organisms which were responsible for the burrowing of parts of the facies, and probably also yielded the scolecodonts which are corrmon in most residues of facies 111:4 mudstone as well as in the silty shale.

The fine terrigenous content of the carbonate protion of facies

111:4 averages 1.9 percent and consists almost entirely of illitic clay with some quartz silt.

Interpretation: The unfossiliferous mudstone (probably originally pelletoidal packstone) which dominates facies 111:4 is interpreted as representing deposition in a low energy above wave-base area even more restricted and distant from the area of normal marine circulation than was the facies 111:3 environment, as is by the almost couplete lack of an indigenous skeletal-bearing fauna. The burrows and soclecoaonts indicate that soft-bodied organisms flourished, however, and these organisms probably produced fecal pellets which formed the bulk of the sediment. Since the environment was probably relatively shallow and warm, however, physicochemical precipitation of carbonate mud directly from sea water may have also taken place. Hie more fossiliferous post-silty shale interval in the north-central area probably reflects deposition in a slightly better circulated area of the sea transitional to the environment of deposition of the overlying facies 111:5. 133'

The entire facies 111:4 interval is believed to represent deposition during a time when the circulation in the shallow sea was more restricted than either during earlier or later unit III time.

This restriction of circulation was probably brought about by regional shallowing. During the peak of this regression former areas of very shallow water carbonate deposition, probably in northwestern

Ohio and southeastern Michigan became emergent and were subjected to intensive ground water solution. Sheetwash and streams probably carried the insoluble detritus leached from these exposed carbonates, and possibly also land plant debris, into the shallow nearshore area of the sea, where little or no carbonate deposition was occurring due to brackish conditions, resulting in an accumulation of organic- rich terrigenous mud now represented by the silty-shale bed. When the sea again transgressed and the emergent areas were re-inundated deposition of carbonate mud (represented by the post-silty shale interval of facies 111:4) began again in north-central Ohio.

Facies 111:5 — Crinoidal Packstone-Gralnstone Facies

Distribution: Facies 111:5 forms the upper 10-15 ft of unit III throughout the cuecrop belt. In Franklin County it gradationally overlies facies 111:2 and corresponds to the upper part of Stauffer’s

(19C9) zone G. In the northern part of the south-central area it very abruptly overlies the 4 ft thick facies 111:4 interval (Figure 49).

In the north-central area it is gradational with the underlying facies III:4 at most places. Facies 111:5 is everywhere terminated by an abraded undulating discontinuity surface which marks the unit III- unit IV contact. 134

Figure 49: Abrupt contact of facies 111:4 mudstone (A) and facies III:5 grainstone (B). Locality S. Scale in inches. 135

Description: Facies III:5 consists largely of gray to gray brown, thin to medium bedded fossiliferous calcarenitic grainstone,

75-90 percent of the biochems of which consist of disarticulated

crinoid fragments (Figures 50, 51). The remaining biochems consist

largely of subequal amounts of fragmented, but only slightly abraded, bryozoan, brachiopod, and indeterminant fragments. Most of the indeterminant biochems are small intensely micritized grains. Many of the larger brachiopod and bryozoan fragments also have dark micritized

rims. Numerous charophyte oogonia and a few tentaculite, trilobite, and coral fragments were observed in most thin sections.

The grainstones of facies 111:5 are best developed in the area between Dealware and Seneca counties. North of Seneca County the

facies is muddier, and although unquestionable grainstone beds do occur in this area many beds which appear to be grainstones in the field

can be seen in thin section to actually be packstones in which the matrix has been almost entirely replaced by neomorphic calcite spar.

Also occurring in facies 111:5 north of Seneca County are thin, partially dolomitized mudstone and wackestone beds, some of which contain abundant spores (Figure 52). Facies 111:5 is also muddier in

Franklin County in the south-central area where discontinuous layers ana lenses of grainstone are gradationally interbedded with intensely bioturbated intervals composed largely of finely comminuted skeletal debris, much of which has been replaced by dolomite.

A diverse and abundant macrofauna occurs in facies 111:5, especially the muddier portions. Most conspicuous and abundant are Figure 50:. Thin-bedded facies III:5 grainstone.. Locality KI. 137

Figure 51: Photomicrograph of facies III:5 grainstone. Crinoid fragments (A) are the' dominant biochem. Note the large ch anophyte oogonia (B) which is partially filled with carbonate mud and partially with drusy calcite cement. Locality U. Scale equals 1 mm. 138

Figure 32:. Hiotomlcrograph of Facies 111:5 mudstone containing numerous plant spores (A). Locality BE. Scale equals 0.5 mm. the thin-shelled stropheodcntid brachiopods. These occur throughout

the facies, but are especially prominent in the north-central area where they virtually cover some bedding planes. Several horizons of the large brachiopod Parasplrifer acuminatus also occur in facies

111:5 in the north-central area. A nuntoer of species of massive

colonial and small solitary rugose corals are common in facies III:5> these also being much more abundant in the north-central than the south-central area. Large gastropods, coiled cephalopods, and pelecypods, on the other hand, are most abundant in the Franklin County area and become progressively less abundant to the north. Many bedding surfaces in the upper part of unit III in the south-central area are partially covered by large fenestrate bryozoan fronds.

The fine insoluble residue content of facies 111:5 averages less tiian 1 percent and consists almost entirely of illitic clay.

Quartz sand is very rare. Chert is uncommon in facies 111:5, having been observed only at locality T in Marion County. Many brachiopod and coral fragments are partially internally replaced by authigenic quartz, however.

Interpretation: The grainstones of facies 111:5 represent deposition in a highly agitated, probably above wave-base portion of the sea where coriditions were ideal for the proliferation of an abundant fauna dominated in the most agitated areas by high epifaunal suspension feeding crinoids and bryozoans. These organisms probably formsd "meadows" which covered large portions of the skeletal-sand substrate, resulting in the exclusion of most other normal marine 140

organisms from such areas. Even in the areas of highest agitation on the disarticulated remains of the crinoids were apparently buried so rapidly by newly produced skeletal debris that they underwent only minor abrasion. The muddier portion of facies 111:5 north of Seneca County probably represents deposition in a generally less intensely agitated and probably shallower portion of the sea where crinoids were less abundant and the muddier substrate was favorable for brachiopods. The beds of spore-bearing mudstone probably represent brief time when more restricted conditions analogous to those represented by facies 111:4 were briefly reestablished. The muddy burrowed part of facies 111:5 in Franklin County is, on the other hand, believed-to represent deposition in generally slightly deeper and less intensely agitated water than represented by the less muddy portion of the facies, 'as is suggested by its more diverse fauna.

In light of the general belief that the so-called "charophyte oogcnia" in the Devonian carbonates of Ohio, Indiana, and Kentucky represent the calcareous fruiting organs of fresh-water algal plants

(Peck, 1934;. Stewart, 1955; Perkins, 1963; Conkin, Sawa, and Kem,

197-) it is perhaps worthy of note that in central Ohio these grains occur only in unir III and are common only in the fossiliferous pack- stcr.es of facies 111:2 and the fossiliferous grainstones of facies

111:5, and are absent or rare in the muddier rocks, both those believed to have been deposited in slightly deeper water (facies 111:1) and in shallower water (facies 111:3, 111:4) than the grain-supported fossiliferous rocks. Similarly in facies 111:5 in the north-central area "charophyte oogonia" are abundant in the grainstone beds, but

do not occur in the interbedded spore-bearing mudstones, believed to have been deposited in probably shallower water than the grainstones.

Furthermore, in the Jeffersonville limestone of Indiana "charophyte oogonia" occur only in the very fossiliferous "normal marine" part of the formation and are absent in the unfossilifenous "laminated beds," which were interpreted by Perkins (196’3, p. 65) as having been deposited In a "shelf lagoon." Thus, since the "charophyte oogonia" seem to occur only in very fossiliferous clacarenites and are rare in rocks believed to have been deposited in shallower water it seems improbable that they were derived from fresh-water algal plants, and instead it is suggested that they perhaps came from marine algal plants which flourished in the agitated normal marine environment, or else that they represent calcareous foraminifera, which they were identified as by Horowitz and Potter (1971* P* 218, Fig. 5).

FACIES OF UNIT IV

General

Unit IV ranges from 4-8 ft in thickness in the southern part of the cub crop belt uo about 15 ft in the north. It has been differentiated ir.cc two distinct, but entirely gradational facies the distribution of which are shown in Figure 53. Also shown are the positions of a prominent 1-2 in. thick shaley bed and a 2-3 ft thick interval which contains abundant tentaculites, both of which are useful "marker beds" in unit IV in the north-central area. figure ;>3: Cross section of Chit IV showing distribution of facies. oo I—I *o Q Erie O >00 0 0. UNIT V CONTACT ur cc Lu. co a. UNIT NORTH-CENTRAL AREA 00 oo UNIT Crawford Co. Seneca FACIES tai 00 Marlon SHALY LIMESTONE BED MUDSTONE GRAIN-POOR WACKESTONE FACIES GRAIN-RICH WACKESTONE-PACKSTONE FACIES TENTACULITE HORIZON xxxx IV:1 IV:2 l— to sis: oo SOUTH-CENTRAL AREA «c «c < o o =r Franklin.Co. Delware HORIZONTAL SCALE-MILES VERTICAL SCALE-FEET figure 53 1 4 4

Facies IV:1 — Mudstone Grain-Poor Wackestone Facies

Distribution: Eacies IV:1 is the dominant facies in the lower

8-13 ft of unit IV throughout most of the north-central area. At most localities it grades rather abruptly into several feet of facies IV:2 which form the upper part of the unit. Eacies IV:1 also grades into facies IV:2 to the south, being.poorly represented south of locality

B in Seneca County.

Description: Eacies IV:1 consists of bluish-gray weathering brown mudstone and grain-poor wackestone which typically occurs in

6-10 in, beds, some of which are separated by very thin shaly partings.

The rather sparse fauna of facies IV:1 is dominated by brachiopods, mainly small thin-shelled forms, which are most abundant on bedding surfaces. A prominent horizon of the large brachiopod Paraspirifer acuminatus occurs a few feet above the base of the facies at most localities. Some beds, especially those in the upper few feet of the facies, contain scattered solitary and branching rugose corals, ramose bryozoans, small gastropods, trilobite fragnents, disarticulated crir.cid remains, fish bone fragments up to several inches long, and ter.oaculites (Figure 54). The latter are especially abundnat in an interval 7-9 ft above the base of unit IV in Erie and Sandusky counties.

Most of the skeletal debris in facies 1V:1 is little fragmented or abraded and probably accumulated essentially in situ, with little physical or biogenic reworking, although burrow mottles do occur in some of the muddier beds indicating the presence of a soft-bodied 145

Figure 54: Negative thln-section print of facies XV: 1 grain-poor wackestone. Ttentaculite fragments (A) are the major biochem. The small black dots are the dark.centers of euhedral dolomite crystals. Locality PK. Scale equals 5 mm. l4 6

burrowing infauna. In the lower 1-3 ft of facies IV: 1 immediately

overlying a prominent discontinuity surface which terminates unit III,

however, fragmented, abraded, and partially silicified brachiopods,

corals, and stromatoporoids are common, although most of these fossils

were derived from the underlying facies 111:5. Also occurring in

the lower, few feet of facies IV: 1 are scattered "bone.” fragments.

At most localities in Erie and Sandusky counties a prominent 1-2 in.

thick clayey shale bed occurs 1-3 ft above the tentaculite-rich

interval, both of which lie progressively closer to the base of unit IV

from north to south. The tentaculite-rich interval is barely

distinguishable at the southernmost locality in the north-central

area (locality B).

Most of the matrix of facies IV: 1 appears to consist of skeletal

calcisiltite. In most samples, however, approximately half of the

calcitic matrix is replaced by 0.7-0.13 rrm dark centered, clear rimmed

euheiral dolomite crystals which only very rarely impinge upon the

biochems. The fine insoluble residue content of. facies IV:1 averages

4.2 percent and consists mainly of Illitic clay with minor angular

ausroz silt and pyrite. Rounded quartz sand grains are common in the

lower lev; inches of facies IV:1, but were not observed elsewhere. Chart

does not occur in facies IV:1 but partially silicified fossils are

cortmcn, especially in the lower part. Many of the bryozoan, brachiopod,

and "bone" fragments are partially to completely pyritized.

Interpretation: The moderately diverse, but not abundant "normal marine" fauna and the dominance of carbonate mud conposed largely of skeletal calcisiltite suggest that facies IV: 1 represents deposition

in a low energy, probably below wave-base environment, but where

circulation and the supply of nutrients was still adequate to support

the brachiopod-bryozoan dominated fauna. This environment was thus

probably similar to that in which facies 111:1 was deposited. Into

this low energy open marine area the finely comminuted skeletal debris

produced by physical and biological reworking in adjacent more agitated

areas (represented by facies IV:2) was carried and deposited, resulting

in a muddy, probably somewhat fluid substrate. This muddy substrate

probably was one of the major factors which inhibited organisms which

require firm places for attachment such as crimoids. The relative

paucity of burrowing and the presence of common pyrite suggest that

reducing conditions may have existed not far below the sediment-water

interface. The shaly partings and the slightly higher average fine

insoluble residue content than any of the very muddy facies in units

I, II, of III suggest that at times the facies IV: 1 environment may

hare teen slightly turbid due to the influx of fine terrigenous materials.

Facies IV: 2 — Grain-rich Wackestone-Packstone Facies

Distribution: Facies IV:2 forms virtually all of unit IV in the

south-central area, where it coincides with Stauffer's zone H, and the upper few feet of unit IV in the north-central area.

Des crlption: Facies IV:2 consists of brownish-gray calcarenitic

and calciruditic packstone, wackestone, and grains tone which breaks into 3-10 in. thick beds (Figure 55). The most characteristic feature of facies IV: 2 is its diverse and very abundant fauna. Among the macro­ fossils the brachiopods are most abundant, with Leptaena rhomboidalis,

Cyrtina sp., Paraspirifer acumlnatus, and Spirifer duodenarius being especially conspicuous. Mollusks, however, which are so abundant in fossiliferous packstones in unit III, are scarce In facies IV:2, except for the the large spiny gastropod Platyceras dumosom. Small rugose corals are common throughout facies IV:2 and in the south-central area an interval approximately in the middle of the facies is characterized by the branching rugose coral Erldophyllum seriale.

In some beds large fenestrate bryozoans are very abundant, almost completely covering the bedding surfaces. Also common in facies

IV: 1, and observed nowhere else in the Devonian carbonate sequence of central Ohio are several species of blastoids. Most of the muddier beds contain elongate tube-like burrows, indicating the presence of’ a soft bodied burrowing infauna.

Thin section study showed that the biochems of facies IV:2 consist of 60-So percent disarticulated echinoderm remains with the reminder consisting of subequal amounts of bryozoan, brachiopod, and Indeter­ minant fragments, Also present in trace amounts are trilobite, ostracode, tentaculite, and "bone" fragments, the latter being most abundant in the lower 0.5-1 ft of the facies. Many of the biochems are penetrated by sharp spar or mud filled borings and in some of the muddier beds the crinoids fragments are irregulary notched and embayed

(Figure 56). The matrix of facies IV:2 consists largely of skeletal 149

Figure 35' Negative thin section print of facies TV:2 packstone- grainstone. Biochems include crinoid fragments (A), brachiopod fragments '(B), bryozoan fragments (C), trilotite fragments (D), and "bone11 fragments (E). Locality MGS. Scale equals 5.0 mm.' 150

FI gore 55: Photomicrograph of facies IV: 2 packs tone. Note the irregularly embayed (bored ?) crinoid fragments. Ihe ligjnter colored area represents a boring filled with calcite spar and biochems. Locality K. Scale equals 2 mm. 151

calcisiltite, up to approximately 20 percent of which is replaced by dolomite crystals identical to those in facies IV: 1. The fine

insoluble residue of facies IV: 1 is similar in composition to that of facies IV:1, bub averages only 2.1 percent. A few white chert nodules occur in facies IV:2 in Franklin County, but chert is very rare elsewhere. Partially silicified fossil fragments, especially brachiopods and rugose corals are very abundant.

Facies IV:2 is characterized by numerous vertical changes in abundance, size, and degree of fragment at ion and abrasion of skeletal debris. Many of these changes are gradational. Other, however, coin­ cide with discontinuity surfaces, the two most prominent of which occur in the basal few feet of the facies and are best developed in Franklin

County. There a smooth undulating discontinuity surface ("smooth layer" of Stauffer (1909) terminating unit III is overlain by a 0.5-1 ft thick bed of facies IV:2 packstone-grainstone containing numerous

"bone" fragments. This bed is terminated by a slightly irregular surface (the upper surface in Figure 9) which is coated and indurated with rusty-looking iron oxide material. This crust is penetrated by Irregular vertical cracks up to 2 in. deep and 1 in. wide which are filled with the overlying "bone"-rich packstone, and by distinct vertical borings up to an inch long which are filled either with iron oxide material or the calcite spar (Figure 12). Approximately 0.5-1 ft above this bored Iron-oxide encrusted surface is a prominent undulating

"mega-rippled" surface (Figure 57). The generally parallel, but slightly curving crests of the ripples trend on the average N15W, and are 152

Figure 57: Prominent "mega-rippled" surface in the upper part of the Columbus Limestone (near the base of unit IV) at locality MGS. 353 separated by 1-3 in. deep trougjis. The distance between the crests ranges from 2-3 ft. The surface appears to have been subject to

considerable abrasion, although it is not nearly as smooth as the undulating "mega-rippled" surface which terminates unit III. Like the iron-oxide encrusted surface the "mega-rippled" surface near the base of unit IV is penetrated by small borings and is overlain by

"bone"-rich packstone.

Interpretation: The abundant and diverse normal marine fauna and the dominant grain-supported texture of facies IV:2 suggests desposition in a moderately to intensely nutrient-rich, probably above wave-base portion of the sea. The numerous vertical variations in texture indicate, however, that energy conditions were quite variable. Some of these variations may reflect fluctuations of mean sea level.

Others, however, may have resulted from sudden changes in wave and/or current energy related to major storms. The bored discontinuity surfaces indicate that some of these changes in water agitation resulted in the cessation of carbonate deposition submarine lithification of the sub­ strate, although it is possible that some of the discontinuity surfacce, the ircn-oxide indurated surface near the base of the facies, for instance, may have been subaerially exposed. The "mega-rippled" discontinuity surfaces are believed to indicate oscillation rippling of the skeletal-sand substrate prior to initiation of lithification

(Bates, 1969). The numerous "bene" fragments which occur in the few inches of packstone overlying each discontinuity surface suggest that during the times of little or no carbonate sedimentation represented 154 by these surfaces the phosphatic fish remains became concentrated on them, where they were fragmented and abraded as a result of prolonged and/or intensive wave agitation, and subsequently were incorporated into the lower few inches of the sediments deposited over each surface.

FACIES OF UNIT V

General

Unit V is the uppermost unit recognized by the author in the

Devonian carbonate sequence of central Ohio and is everywhere discon­ formably overlain by Devonian shales. It ranges in thickness from about 35 ft in the south-central area to possibly as much as 70 ft in the north-central area (Stauffer, 1909, p. 143), although only the lower approximately 30 ft are exposed anywhere in the latter area.

Six facies have been recognized by the author in unit V, the distribution of which are shown in Figure 58. Also shown is the position of a thin clay-shale bed which lies 1.5-3 ft above the base of the unit at most localities. Oliver and others (1969, p. 1007) correlated this clay-shale bed with the Tioga Bentonite, a prominent volcanic ash bed in the central Appalachian region, where It forms the boundary.' between the Chesquethaw and Cazenovian stages of the Devonian

(Dennison, 1961). The Bentonite is discussed in more detail following description and analysis of the unit V facies.

Facies V:1 — Basal Packstone-Grainstone Facies

Distribution: At most places facies V:1 forms the basal 0.3-2.5 ft of unit V, everywhere overlying an irregular bored discontinuity surface 155

Figure 58: Cross section of unit V showing distribution of facies. cr» Jji N l 2^ C FACIES cc U_ WACKESTONE FACIES Seneca Co. Erie Co. NORTH-CENTRAL AREA GRAINSTONE FACIES MUDSTONE GRAIN-POOR » » W*V **-.77j ’ >."7 vv. ; 1 CALCIRUDITIC PACKSTONEUPPER CALCARENITIC f T > T o° ^ J< ° ^ O _ o _ ^ £ Tr °. e.°° - ° "t o J* >_ - V ED ("TIOGA BENTONITE”.) b ■ J P H ' h V:5 V:6 V:4 . 1 ^FACIES OF UNIT A 0 - - 0 - - 0 m 111 • / A S W A Q - ( O ( Q - tt™t if- j if- tt™t 1 1 0 MUDSTONE-FACIES BASAL PACKSTONE- ARGILLACEOUS — POSSIBLE VOLCANIC AS .GRAINST0NE FACIES I I I I I .CRINOIDAL WACKESTONE FACIES

DEVONIAN SHALES S I I I 0.9 ®0® 0.9 + + + + ■( + + + + cq or F 7 T 7\ S : ] # h I oi =c V:3 V:2 V:1

20 ; H- ; —j I I I 2 O O UNIT IV-UNIT V CONTACT Frank'Hn Co.Delware Co. Marlon Co. Crawford Co. SOUTH-CENTRAL AREA I 10 HORIZONTAL SCALE-MILES -20 -10 -0 u VERTICAL 0 SCALE-FEET

Figure 58, 157 which terminates unit IV. In the south-central area it coincides

with the lower part of Vfestgate and Fischer* s (1933) "lower bone-bed."

Some workers (Swartz, 1907; Wells, 1944) have assigned this interval

to Columbus on the basis of its greater lithologic similarity to the

underlying than the overlying strata. Vfestgate and Fischer (1933,

p. 1163) and Conkin and Conkin (1975, p. Ill), however, have argued

that since this interval contains the first restricted Hamiltonian

fossils in the Devonian section it should be considered as the basal bed of the Delaware rather than the uppermost bed of the Columbus.

Thus, it has been included in unit V, rather than unit IV.

Throughout much of the south-central area facies V:1 grades upward into the mudstones and grainstcries of facies V:4. In both

Franklin County In the south-central area and at most places in the north-central area, however, facies V:1 is terminated by a smooth

Irregular discontinuity surface which has a relief of up to approxi­ mately 1 ft and in places truncates • facies IV:2, facies V:1 having been cccpletely removed by erosion. In the Franklin County area this

discontinuity surface is iimediately overlain by 1-6 in. of brown

clayey shale at the base of facies V:3 which contains numerous "bone"

fragments in places and corresponds to the upper part of Vfestgate

and Fischer's (1933) "lower bone-bed." In the north-central area it is overlain by several inches of burrowed mudstone at the base of

facies V:2.

Description: Facies V:1 consists of fossiliferous packstone and grains tone. The grainstone is most conspicuous in the south-central area where It forms the lower 0.2-1.3 ft of the facies, immediately

overlying and filling in the irregularities in the discontinuity sur­

face which terminates unit IV. The grainstone Is faintly cross­

stratified and consists of packed well rounded and sorted biochems

cemented by clear calcite spar cement (Figure 59). Constituent analysis

showed that on the average the biochems consist of echinoderm fragments

(47 percent), brachiopod fragments (22 percent), bryozoan fragments

(9 percent), "bone" fragments (2 percent), indeterminant fragments

(20 percent), and trace amounts of ostracod, trilobite, tentaculite,

and rugose coral fragments. Most of the indeterminant biochems are probably brachiopod and bryozoan fragments, but since the skeletal

structure of these two groups of organisms is very similar they cannot easily be differentaited when the grains are small and well rounded.

Also occurring in the lower 2-3 in. of the facies V:5 grainstone are

rounded, bored, and in some instances iron oxide indurated clasts

derived from the underlying unit facies IV:1 as well as scattered rcur.ded quartz sand grains.

Most of the facies V:1 interval in the north-central area and the upper part in the south-central area consists of calcarenitic packsccne and wackestone. Characteristic of these muddier portions of the facie are numerous horizons of fragmented, abraded, and partially

silicified thick-shelled brachiopods and rugose corals. Also con­

spicuous are partially pyritized ramose bryozoans and an interval at the very top of the facies at most localities which contains numerous ver­ tical pyrite filled (replaced ?) burrows up to 1.5 in. long (Figure 60). 159

Figure 59; Negative .thin section print of facies V:l. grainstone. Rounded crinoid fragments (A) are the dominant biochems, with secondary ramose bryozoans (B). The dark areas consist of crystals of drusy calcite spar cement. Locality MCS. Scale equals 2 mm. Figure 60: Py rite-filled vertical burrows in facies V:1 packstone. Locality MCS. Scale is in cm. 161

Ihe fine matrix consists largely of skeletal calcisiltite partially replaced by dark centered, clear rimmed centimicran-sized dolomite crystals. The fine insoluble residue content of the facies V:1 packstones averages 2.6 percent. Chert was not observed in facies

V:l.

Interpretation: The grainstones of facies V:1 represent deposition in a very highly agitated, probably above wave-base environ­ ment where the skeletal remains of diverse normal marine organisms were intensely fragmented and abraded. The crude cross-stratification suggests that currents may have been responsible for considerable lateral transport of the biochems. This high energy environment was established over a bored discontinuity surface with both "bone" fragments which were concentrated on the surface prior to reinitiation of carbonate deposition and clasts eroded from the lithified surface being incorporated into the grainstone. The facies V:1 packstones represent deposition in a generally somewhat lower energy environment, probably analogous to that proposed for facies IV:2. The smooth discontinuity surface which terminates facies V:1 in places suggests that in such places facies V:1 deposition was ended by a probably abrupc change in hydrodynamic regimen, or possibly by emergence, followed by submarine and/or subaerial cementation and scour, the latter resulting in the complete removal of facies V:1 in some in some areas. Those areas, on the other hand, where facies V:1 appears to grade upward into facies V:*J may represent topographically low areas 162 where the substrate was not lithified and scoured and deposition was more continuous.

V:2 — Crinoidal Wackestone Facies

Distribution: Facies V:2 is best developed in the north-central area where it is 5-8 ft thick and overlies facies V:l. It grades upward and southward into facies V:4.

Description; Facies V:2 consists of calciruditic fossiliferous wackestone and minor packstone, with the biochems consisting mainly of nan-abraded crinoid remains (Figure 6l). Ihe largest crinoid remains occur packed together in 1-2 in. thick bands which alternate with 3-6 in. thick muddier bands containing smaller and less abundant crinoid frag­ ments as well as small ramose and fenestrate bryozoans and thin-shelled ' brachiopods. As can be seen in Figure 61 the bases of the bands of packed crinoid remains are rather abrupt, whereas the upper contacts are more gradational. The muddier bands display a faint horizontal stratification and contain very thin shaly partings which are covered with meandering tracks and trails and in which fish scales and plates up to an Inch.In size are embedded. The shaly partings are more abundant near the top of the facies. The matrix of facies V:2 consists of fine silt-sized recryszaliized calcite particles which have in part been replaced by dark centered, clear rimmed centimicron-sized euhedral dolomite crystals.

The fine insoluble residue content averages 4.8 percent, the residues consisting largely of illitic clay with minor quartz silt. No rounded quarts sand grains were noted. Nodules of white fossiliferous chert 3.63

Figure 6l: Facies V:2 crinoidal wackestone. Note the beds of packed crinoid fragments, alternating with less fossiliferous beds. Locality V. Scale Is In cm. . 16* occur In the upper part of facies V:2 at most localities. Pyrite occurs in facies V:2 as a partial replacement of ramose bryozoans.

Interpretation: Facies V:2 is believed to represent deposition in a low to moderate energy environment in which the supply of nutrients was sufficient to support the crinoid dominated fauna. The crinoids may actually have populated slight topographic highs, their disarticu­ lated remains being swept by storm generated waves or currents into adjacent slightly deeper and lower energy areas,- producing the sharp- based packstone intervals. The thin shaly partings probably indicate times of very low energy when there was little or no carbonate deposi­ tion, permitting thin layers of fine terrigeous material to be concen­ trated on the sea floor, or else sudden influxes of such fine allogenic material into the environment. The "bone" material embedded in the shales suggests that the former is the more likely case, however. The replacement of biochems by pyrite and the shallow nature of the burrows suggest that reducing conditions may have existed only a short disoar.ee below the sediment-water interface.

Facies V:3 — Argillaceous Mudstone Facies

Distribution: Facies V:3 dominates unit V in Franklin County where it is approximately 23-25 ft thick and coincides with Stauffer’s

(19C3) zones I, J, and K, although these zones are more easily distinguished in Delaware County to the north where facies V:3 is gradational with facies V:4. At its base facies V:3 contains the thin clayey bed which overlies the discontinuity surface truncating 165

facies V:l. It is very abruptly overlain by a thin interval of

facies V:5.

Inscription: In general facies V:3 consists of medium to dark

gray, very cherty and argillaceous mudstcne. It is best exposed at

locality MCS, where the lower 2-3 ft is distinctly different from the

succeeding portion of the facies. It consists of laminated

argillaceous mudstone which contains numerous continuous black chert

beds up to 1.5 in. thick (Figure 62). The lamination is formed by the

alternation of 0.'5-4 mm thick very argillaceous laminae with up to

15 nm thick less argillaceous laminae consisting of packed small

centimicron-sized dolomite crystals. Some of these coarser laminae

also contain much angular to subrounded quartz silt and small indistinct

pelletoids. Except for a few phosphatic inarticulate brachiopod

fragments (Lingula nannl, Qrbiculoidea lodlensis) this basal facies

V:3 interval is devoid of fossils. This interval Is terminated by an

irregular surface penetrated by vertical finger-like burrows up to

1.5 in. long which are filled with argillaceous mud containing much

angular silt- and sand-sized bone material. This "bone-bed" lies at

the base of an approximately 18 ft thick interval of shaly massive

argillaceous mudstone which contains discontinuous stringers of both

light and dark colored chert in the lower part and more irregular masses of dark colored chert with light colored rims in the upper part (Figure 63). This interval is thin to medium bedded due to many thin shale partings. Some of the beds are slightly coarser grained and more "crystalline" appearing than the others and these typically 166

Jlgure 62: Cherty and silty argillaceous laminated mudstone of facies V:3 (B) overlying facies V:l( A). The cent act is a discontinuity surface. Locality' MCS. 167

Figure 63: Typical appearance of facies V:3. Ihe section shown is approximately 14 ft thick. Note the numerous semi- ccntir.ucus bands of dark chert.' locality MGS. contain scattered silt-sized "bone" remains, as well as very uncomnon thin-she lied brachiopod and tentaculite fragments. Several 0.5-1 in. coquina-like beds occur in this interval, however, which consist almost entirely of packed fragments of the thin-shelled brachiopod

Leptaena rhdmboidalis. Some of the shaly bedding surfaces also display faint horizontal meandering trails, indicating the presence of bottom- feeding organisms. Thin sections of the argillaceous mudstone show a mixture of finely comminuted and skeletal debris, clay and quartz silt, and small centimicron-sized dolomite crystals. Also present are very delicate unidentified calcitic microfossils and numerous small brownish-black spores, both of which appear to be highly compressed.

In some samples the dolomite appears to have replaced up to 50-60 percent of the matrix. The fine insoluble residue content of the mud­ stone beds ranges from 8-35 percent and these residues consist pre­ dominantly of ill!tic clay with considerable angular quartz silt and minor pyrite and bituminous material.

Interpretation: The argillaceous mudstones of facies V:3 represent a relatively low energy environment into which both calcisiicitic skeletal debris produced in agitated shoal areas and fine terrigenous material derived from clastic source areas probably far to the southeast was transported and deposited. The absence of shallow- water sedimentary structures in most parts of the facies suggests that this low energy environment was probably below wave-base at most times. The poor water circulation and high turbidity due to the influx of-the fine terrigenous material, inhibited most normal marine organisms. Occasionally, however, probably during storms, the muddy substrate was disturbed, resulting in local winnowing away of mud and concentration of the few skeletal fragnents into the thin coquina-like beds. The presence of bituminous matter and pyrite in the mudstones suggest that reducing conditions may have also prevailed just below the substrate, further inhibiting most benthonic organisms. Perhaps reducing condi­ tions also in some way aided the probably very early diagenetic formation of the chert. The lower laminated portion of facies V:3 may possibly represent deposition in a considerably shallower and/or more "restricted" environment than proposed for the rest of the facies.

This is suggested both by its delicately laminated character and by its irregular burrowed and scoured upper contact which may be a facies dis­ continuity representing the rapid transgressive migration of the agitated near-wave base part of the sea and establishment of deeper water below wave-base conditions in a former area of low energy above wave base mud deposition. It is not feasible, however, that the lamination could have formed in a relatively deep undisturbed portion of the shallow sea.

Facie; — Mudstone-Grain-Poor Wackestone Facies

Distribution: Facies V:4 is the dominant facies in the exposed part of unit V, averaging approximately 25 ft thick throughout the outcrop belt. In the south-central area north of Franklin County, where it coincides with Stauffer’s zones I, J, and K, it gradationally overlies facies V:1 and is abruptly overlain by facies V:5. In the north-central area it is gradational with the underlying facies V:2 and grades upward 170

rather abruptly into facies V:6. Throughout Franklin and southern

Delaware counties an up to 9 ft thick interval of facies V:4

(coinciding to Stauffer's (1909) zone M) lies between the thin facies

V:5 interval and the Olentangy Shale.

Description: In the south-central area tlje lower 27 ft thick interval of facies V:4 is best exposed at locality JE in Marion County.

Here the lower approximately 16 feet consists of 1-3 ft thick mudstone and grain-poor wackestone beds which are interbedded with up to 8 in. thick recessive weathering shaly mudstone intervals (Figure 64).

Mudstone and grain-poor wackestone beds consist largely of packed skeletal calcisiltite up to 30-40 percent of which has been replaced by small dark centered, clear rinmed centimi cron-sized dolomite crystals (Figure 65). The fauna is moderately diverse and abundant.

Most conspicuous are brachiopods, leptaena rhomboldalis and Delthyrls cosibrlna being the most abundant. Also occurring in most of the mudstone-wackestcne beds are scattered small gastropods, pelecypods, tencaoulites, and bryozoan and crinoid debris. In some beds small rugose corals are present, and in the lower part of facies V:4 transitional to facies V:1 branching rugose corals, small massive colonial corals, and coiled cephalopoda were observed. The fossils are most abundant on the bedding surfaces beneath the bun-owed shaly intervals. Some of these surfaces are virtually covered with the slightly abraded remains of one or two species of brachiopods, whereas on others, tentaculites are very abundant and brachiopods are scarce. Hie shaly intervals themselves are generally unfossiliferous 171

Figure 64: typical appearance of the lower part of facies V:4. Note the thick muds tone-wackes tone beds alternating with thinner argillaceous beds. A possible volcanic ash bed (Tioga Bentonite ?). lies immediately be lew the prominent overhang in the lower right comer of the picture. Locality JE, 172

Figure 65: Ehotcndcrograph of facies V:^ mudstone.composed largely of skeletal calcisiltite. partially replaced by dolomi'te crystals. The dark grains are "bone" fragments. Locality N. Scale equals 2 mm. 173

except for scattered compressed tentaculites and uncommon brachiopods.

They typically contain abundant horizontal burrow tubes up to 0.8 In.

In diameter, however, which consist of packed aggregates of small clear

dolomite crystals and have pyritic centers (Figure 66). A variety of

tracks and trails also occur on the bedding surfaces. Horizons of

white chert nodules occur scattered throughout the lower portion of

facies V:4, many of them being localized in and around horizontal

burrow tubes.

Tne upper 10-11 ft of facies V:4 at locality «JE is much less

argillaceous than the underlying part of the facies and consists

entirely of grain-poor wackestone containing much white nodular chert,

especially in the upper few feet. This interval contains considerable

sand-sized crinoidal and bryozoan debris, but is lacking in macrofossils

compared to the lower part of the facies. Hie portion of facies V:4

coinciding with Stauffer’s (1909) M zone in Franklin County consists

of massive non-argillaceous mudstone containing a few brachiopod-rich

Intervals and much white nodular chert.

In north-central Ohio facies V:4 is best exposed at locality PK

in Erie County. Here the lower 20-22 ft of the facies consists of thin-

bedded. mudstone with numerous thin-shaly partings and almost no macro-

fossils except for uncomnon fenestrate bryozoans. Small crinoid and

tentaculite fragments were observed scattered throughout the partially

dolomitized skeletal calcisiltite matrix of most.thin-sections, however.

Many of the argillaceous bedding surfaces also displayed faint meandering trails. The upper 5-6 ft of facies V:4 at locality PK consists of 174

Figure 66: Burrowed argillaceous mudstone of facies V:4. Ihe light colored burrows have pyritic nuclei.. .'Note, the scattered compressed tentaculltes. Locality. K. Scale in cm. grain-poor wackestone containing scattered crinoid debris. Chert is

common in V:1! in the north-central area only in the lower few feet

of the facies V:1 transitional to facies V:2.

The fine insoluble residue content of facies V:4 ranges from

4-30 percent, being the greatest in the lower part of the facies in the

south-central area. As in facies V:3 the fine residue is composed largely of illitic clay with much quartz silt. Spores are also common in most residues of this facies, ihe coarse residues consisted of chert fragments, silicified fossil fragments, and pyritized fossil fragments.

Interpretation: Facies V:4 probably was deposited in a low energy below wave-base environment slightly deeper and further removed from the source of terrigenous material than the environment of facies V:3 deposition. In the north-central area the facies V:4 environment was apparently so far below wave base that the supply of nutrients was insufficient to support an indigenous skeletal fauna and unfossiliferous skeletal calcisiltite accumulated.

In the Delaware to Crawford County region, however, the water was apparently clear enough at most times and the supply of oxygen and nutrients sufficient to support a moderately diverse and abundant fauna, dominated by low epifaunal suspension feeding brachiopods and pelecypods.

The skeletal remains of these organisms accumulated relatively whole and non-abraded in the muddy substrate. Occasionally, however, the muddy substrate was disturbed by deep storm waves, resulting in winnowing away of mud and the formation of coquina-like concentration of somewhat abraded, but still mostly whole, fossils. At other times influxes of much fine terrigenous material led to the demise of the skeletal- bearing organisms and deposition of the very shaly mudstone intervals.

This terrigenous material may have been associated with much fine organic material resulting in the intensive mining of the mud by soft-bodied infaunal organisms which produced the conspicuous burrow tubes. Tie upper less argillaceous and more crinoidal portion of the major interval of facies V:4 throughout the outcrop belt probably reflects deposition in a somewhat shallower, and better circulated, but still probably below wave-base area than the lower portion of the facies.

Facies V:5 — Upper Calcarenitic Grainstone Facies

Distribution: Facies V:5 has been observed only in the south- central area where it coincides with Stauffer’s (1909) L zcne of the

Delaware limestone. It is best developed at locality D in Delaware

County, where it ranges from 3-7 ft in thickness. Here it abruptly overlies facies V:4 and is terminated by an irregular channeled appearing surface. This surface is overlain by several feet of ferruginous stained, crudely cross-stratified crinoidal packstone and grainstone, the lower few inches of which contain numerous sand size bore fragments. This lithology corresponds to Vfestgate and Fischer’s

"upper bone bed" of the Delaware limestone, but Conkin and Conkin

(1975, p. 111-112) have shown that it actually represents a basal calcarenite of the Olentangy Shale, the irregular channeled surface it overlies being the post-Delaware erosion surface. Facies V:4 thins to i77 the south of locality D so that at locality MCT in Franklin County it occurs only as scattered up to 0.5 foot thick lenses lying between the upper and lower intervals of facies V:*J. The northernmost locality where facies V:5 was observed is locality JE in Mart ion County where two feet of it abruptly overlies facies V:4 at the very top of the section.

Description: Facies V:5 consists of massive appearing fine to coarse calcarenitic grainstone, 75-85 percent of the biochems being abraded disarticulated crinoid fragments, with the remainder consisting of abraded bryozoan, brachiopod, ostracod, trllobite, and bone fragments (Figure 67). Many of the ostracod, trllobite, and bone frag­ ments are partially pyritized. Peels and polished slabs show that the massive appearing grainstone consists of numerous layers of spar cemented packed skeletal debris with the mean grain size of the biochems in each layer -differing from the mean grain size of the biochems In the adjacent layers. These layers are separated from one another by sharp micro-discontinuities. Phcrofossils are uncommon except in the layers with the coarsest biochems. These usually contain scattered specimens of the small "button" coral Hadrophyllum d'Orbigiyl as well as larger ramose and fenestrate bryozoan fragments.

Samples of facies V:5 yellded virtually no fine insoluble residues.

Besides pyritized fossil fragments most of the coarse residues contained a -few rounded quartz sand grains. 178

Figure 67: Negative thin section print of facies V:5 gralnstcne. Locality JE. Scale equals 1 iron. 1;79

Interpretation: The environment of deposition of facies V:5

was likely very similar to that of the grainstone portion of facies

V:l, a highly agitated above wave-base environment from which all

carbonate mud was winnowed by energetic waves and/or currents

leaving behind size sorted fragmented and well abraded biochems.

Facies V:6 Calciruditle Packstorte Facies

Distribution: Facies V:6 forms the upper few feet of the exposed

portion of unit V at a few localities in the north-central area,

occupying the sane relative stratigraphic position as facies V:5 in

the south-central area. It rather abruptly overlies facies V:4.

Description: Facies V:6 consists of calciruditic packstone and

grain-rich wackestone containing an abundant and diverse macrofauna of brachiopods (mainly thin-shelled forms), peleeypods, corals (both solitary rugose and massive colonial forms), large bulbous stromatopo- roids, and large coiled cephalopods (Figure 68). The skeletal sand p o m i o n of the facies consists primarily of crinoid fragments, with sutordinant amounts of brachiopod and bryozoan fragments. The matrix consists of skeletal clacislltite. Small dolomite porphyrotopes occur scattered throughout the matrix. The fine insoluble residue content of facies V:6 averages 2.5 percent and consists largely of illitic clay with some quartz silt. The coarse residues consist entirely of partially silicified fossil fragments. A few nodules of white replace­ ment chert were noted. 180

Figure 68: Negative thin section print of facies V:6 fossillferous wackes tone-packs tone. Crinoids (A) are the dominant biochem, with secondary bryozoan (B) and brachiopod (C) fragments. Ihe white appearing portions of the matrix consist of lllitic clay. Most of the matrix is skeletal calcisiltite. Locality SD. Scale equals 0.5 mm. .181

Interpretation: Facies V:6 probably represents deposition in

a well circulated nutrient portion of the sea, probably close to mean wave base, as suggested by the diverse and abundant macro-fauna and the abundant, skeletal sand. In this environment biogenic reworking predominated over physical reworking, resulting in fragmented, but unabraded skeletal debris.

Tioga Bentonite

The Tioga Bentonite is a widespread volcanic ash bed which is most prominent in the central Appalachian region where it occurs between the Moorehouse and Seneca members of the Onandoga Limestone and forms the boundary between the Onesquethaw and Cazenovian stages of the

Devonian (Dennison, 1961; Oliver and others, 1967). In this region the Tioga is a tuffaceous shale composed largely of interstrati fled illite and smectite with scattered euhedral crystals of biotite,

K-feldspar, albite, apatite, and zircon (Weaver, 1956; Dennison and

Textoris, 1970). In west-central Virginia, near the probable volcanic source, the tuffaceous beds occur throughout a 40 m interval of marine

Devonian strata; however, throughout most of the central Appalachian area the Tioga is a single bed less than 1 m thick (Dennison and

Textoris, 1970).

The stratigraphic position of a thin shale bed believed to be the Tioga was located from geophysical logs in numerous wells in the

Illinois Basin area by Collinson and others (1967), and Droste and

Vitaliano (1973) reported the presence of a thin shale bed near the top of the Jeffersonville Limestone in southeastern Indiana, and near the top of the Detroit River Formation in northern Indiana which

they also believed is the Tioga. This possible Indiana Tioga is seldom over an inch thick and in some places Is a "pure ash" consisting

only of clay and non-clay minerals characteristic of K-bentonites

(although blotite Is absent), whereas elsewhere it Is an "impure ash"

in which the pyroclastic components are admixed with up to 50 percent

of the "normal Middle Devonian suite of illite and subrounded quartz

grains" (Droste and Vitaliano (1973)). Baltrusaitis (197^) correlated

a biotite-rich bed near the top of the Lucas Formation in the

Michigan Basin with the Tioga Bentonite of. the Appalachian Basin; however, he does not believe that this Kawkawlin Bentonite correlates with Droste and VitalianoTs Indiana "Tioga" on the basis of the apparent absence of biotite in the latter and his belief that the stratigraphic interval containing the Kawkawlin was removed by pre-

Traverse erosion in northern Indiana. Baltrusaitis (197^, p. 1330) therfore concluded that "the Tioga Bentonite reported in Middle

Devonian strata in northern Indiana on the southern flank of the

Michigan Basin Is considered on the basis of stratigraphic position to he much older than the Tioga bentonite of the Appalachian and

Illinois Basins." Droste and Shaver (1975), however, argued that the

Indiana "Tioga" and the Kawkawlin Indeed represent the same isochronous bed and that both represent the Tioga.

Prior to this study the Tioga has been reported as occurring near the top of the "Qnandoga" in the far eastern part of Ohio by

Janssens (1969) and at the Colurrbus-Delaware contact near Sandusky in northern Ohio by Oliver and others (1967). Janssens (1970a, p.6) also stated that D. A. Textoris and J. M. Dennison believed that the

"3-inch bed of shale" which lies between the Columbus and the Delaware

(actually between facies V:3 and either facies V:1 or IV:2) in

Franklin County is the Tioga. The Tioga reported from the eastern Ohio subsurface by Janssens (1969) was described as being "mica-rich" and almost certainly represents the biotite-rich Appalachian Basin

Tioga. The status of the reported Tioga in central Ohio is less certain, however, for although the author has found this 1-2 inch thick brown clay shale seam near the base of unit V at numerous localities within intervals of several different unit V facies (See Figure 58). x-ray diffraction analysis shows that it does not posses any of the mineralogical attributes of a K-bentonite, consisting almost entirely of illite. This, however, could be the result of dilution and/or diagenetic alterations, and on the basis of its distinctive appearance and the fact that it occurs in several unit V facies the author tenatively accepts the correlation of this clay-shale bed near the base of unit V with the Appalachian Basin Tioga and the probable

Indiana Tioga reported by Droste and Vitaliano (1973). CHAPTER VI

ANALYSIS OF INTER-UNIT CONTACTS

UNIT I-UNIT II CONTACT

Description

The unit I-unit II contact is well exposed only at a few localities in the south-central area where It coincides with a prominent sharp but slightly irregular surface which terminates either facies 1:2 dolomitized mudstone or facies 1:3 coralliferous crinoidal grainstone.

This surface is overlain by 0.5-2 in. of black fissile shale at the base of either facies 11:1 coral-stromatoporoid wackestone or facies

11:2 cherty gastropod mudstone (Figure 69). Below this surface originally muddy unit I rocks have been intensely dolomitized and the fossils in them have been leached so that they occur only as molds, mar.y. of which have been enlarged by solution and filled with calcite spar cement. Above the surface, however, dolomitization has been less intense and calcitic fossils are generally very well preserved.

In the north-central area most of the quarries are not deep enough to expose the unit I-unit II contact, however, in cores from localities B, F, and BE it was placed at the abrupt change from brown cherty and porous dolomitized mudstone of facies 1:2 to the more

184 185

Figure 69: Unit I-unit II contact. Locality. C.

C. Facies 111:1.

B. Facies 11:1 (2 ft thick).

C. Facies I:2. 186

heterogeneous and non-cherty finer grained carbonates of facies 11:3.

This change occurs approximately 2-k ft below the base of the lowest

distinct sandy bed in facies 11:3 in each of the cores, however, due

to the fragmented nature of the cores it could not be determined

whether it coincides with a distinct surface as it does in the south-

central Olio.

Interpretation

The unit I-unit II contact is believed by the author to represent

an unconformity formed as a result of regression of the unit I sea

and emergence of the central-Ohio area during probably latest Emsian

time. This is suggested both by the sharp lithologlc and diagenetic

breaks with which the contact coincides and by the thin black shale

which overlies the surface, which is believed to represent the basal

nearshore deposit of the transgressing unit II sea. Although some of

the southward thinning of unit I may be due to more intensive post­

unit I erosicn in the south than in the north, much of this thinning

is probably depositional, as indicated by the absence of facies 1:2

at locality HM.

UNIT II-UNIT III CONTACT

Description

The unit II-unit III contact coincides with an abrupt change in

lithology throughout central Ohio, but only at a few places does it coincide with a distinct surface of separation. At most places in the south-central area the unit I-unit II

contact is between facies 11:1 coral-stromatoporoid wackestone and facies

111:1 brachiopod wackestone (Figure 70). The contact of these two

facies is quite sharp and distinct, but generally is not a distinct

separation surface, and at some places the two facies even appear to

be gradational over a vertical distance of 0.1 in. or less. At most

places the basal 1 ft of facies 111:1 contains partially fragmented

and somewhat abraded corals derived from facies 11:1, as well as numerous small indigenous gastropods. Also occurring in the basal

foot of facies 111:1 are numerous well rounded quartz sand grains. The unit II-unit III contact is generally similar in appearance where

facies 111:1 abruptly overlies the cherty gastropod mudstone of

facies 11:2, although at such places the coral fragments in the basal

1-2 ft of facies 111:1 are.> generally smaller and less abundant than where it overlies facies 11:1 (Figure 71)*

At locality S facies 11:1 is overlain not by facies 111:1, but instead by Brevispirifer gregarius and charophyte oogonia bearing

fossiliferous packstones and grainstones of facies 111:2. This contact is very abrupt ana distinct, but takes place within a thick stratum and is not marked by a physical surface of separation. It is also quite irregular, with numerous shallow scour-like depressions and vertical finger-like burrows up to 0.4 ft long penetrating the underlying muddy facies 11:1 which are filled with the basal very sandy calcarentic grainstone of facies 111:2, Although the burrows are sharp and distinct, in some places the burrow-filling material merges with 188

Figure 70: Unit II-unit III contact. :Locality.U.

B. Facies 111:1 containing fragjnented and abraded corals and stromatoporoids derived from the underlying facies 11:1 in the lower six inches.

A. Facies 11:1. 189

Figure 711 Unit II-unit III contact-at locality. MCS. The vertical bar represents. 1 ft.

B. Facies 111:1.

A, Facies 11:2., the muddy matrix near the peripheries of the burrows, suggesting that the muddy facies 11:1 sediment was not yet thoroughly lithified when the burrowing occurred.

At those localities in the north-central area where the unit li­ mit III contact occurs between facies 11:3 and facies 111:2 it generally appears identical to the way it does at locality S, except that in some places tabular silicified clasts of facies 11:3 mudstone occur in the basal sandy 2-4 in. of facies 111:2 (Figure 72).

However, where facies 111:3 dolomitized burrowed mudstone and wackestone overlies facies 11:3 the contact is much less conspicuous, although just as abrupt as elsewhere. At such places It coincides with a sharp color break from the tan and brown muddy facies 11:3 rocks below to the greenish-gray muddy facies 111:3 rocks above (Figure 73). At locality Be, however, the uppermost bed of facies 11:3 is finely laminated mudstone rather than massive mudstone and its contact with the over- lying facies 111:3 is quite sharp and conspicuous, being marked by a 1.5 in. shaly seam which locally thickens into a 1-2 in. thick lense of packed tabular' clasts of the laminated mudstone in a very sandy matrix.

Interpretation

The unit II-unit III contact is believed to represent a facies discontinuity or "ravinerrent" (Swift, 1968) formed as a result of a very abrupt and major rise in relative sea level which resulted in rapid deepening of the sea and inproved circulation throughout central ( M o and hence sudden termination of the deposition of the unit II facies. Figure 72: Unit II-unit III contact at locality B.

B. Facies'111:2.

A. Facies 11:3. 192

Figure 73 : Unit II-unit III contact .at locality . F, . :The scale is three feet long.

B. Facies 111:3 (Burrowed mudstane-wackestcne facies).

A. Facies 11:3 (Sandy laminated mudstone facies). Ihis is suggested by the fact that each of the abrupt facies changes

coinciding with the unit II-unit III contact represents a change

from restricted and/or shallower depositional conditions to more open marine depositional conditions, the absence of a distinct surface of

separation between the units, which would be expected if unit II deposition had been terminated by emergence, and by the burrows, which indicate that the unit II muds were not everywhere completely lithlfied prior to initiation of unit III deposition. During and iirmediately after this abrupt rise in sea level disequilibrium conditions probably prevailed throughout the area, resulting in a period of ncn-deposition during which the part of the sea floor over which the agitated near wave-base zone of the sea traversed were subjected to intense submarine erosion. This submarine erosion is believed responsible for the uneveness of the contact in places and also accounts for the abraded and fragmented coral and stromatoporoids and the tabular dolostone clasts which occur at the base of the unit III in the south-central and north- central areas, respectively. These dolostone clasts were probably derived from portions of the stustrate in the area of facies 11:3 deposition which had been emergent and subaerially lithified immediately prior to the sudden sea level rise, During this period of noncarbonate deposition quartz sand was also spread over the post-unit II surface by waves and currents, much of it possibly having been derived from submarine erosion of sandy facies 11:3 beds in the north, but some possibly having been transported by wind or water from the area of

Slyvania Sandstone accumulation in northwestern Ohio. When equilibrium 194

conditions were reestablished deposition of unit III carbonate sediments

began, the different basal unit III facies reflecting regional variations

in water depth and water energy. This initiation of unit III

deposition probably did not begin precisely simultaneously throughout

central Ohio. However, if the unit I-unlt II contact does represent

a sudden and significant rise in relative sea level then it may

approximate a time line, at least locally, and this sudden sea level

rise should be reflected in the Devonian carbonate sequence in neighboring regions as well.

UNIT III-UNIT IV CONTACT

Description

Tne unit III-unit IV contact coincides with a smooth, gently undulating surface which truncates grains, burrows, and even large fossils in the underlying calcarenitic fossiliferous packstones and grainstones of facies 111:5 and which Is overlain by calciruditic wackestones of facies IV:2 in the south-central area and calciruditic wackestones of facies IV: 1 in the north-central area (Figure 74). In the lower 0.5-1.5 ft of both these unit IV facies abraded fragments of facies 111:5 fossils and sand-sized "bone" fragrents are quite coircnon, the latter being especially abundant in the Franklin County area.

Scattered rounded quartz sand grains also occur throughout this basal unit IV "bone-bed" ("first bone-bed" of Wells (1944)), At some localities the post-unit III surface has been stripped by quarrying and it can be seen to be "mega-rippled," consisting of alternating very shallow 195

Figure 74: Polished slab showing the unit III-unit IV ccaatact. Locality K. Scale in cm.

B. Facies IV:2. Note the numerous black "bone" fragments.

A. Facies 111:5.

» 196 parallel troughs and ridges which trend in a general N20W-N25W direction throughout central Ohio and have wavelengths of approximately

2 ft.

In the Franklin County area the unit III-unit IV contact is the

"smooth zone" of Stauffer (1909). Ibis almost perfectly smooth

slightly undulating surface truncates large corals and brachiopods in the underlying facies 111:5 grainstone and in some places is penetrated by small vertical borings. For 2-10 mm beneath this smooth surface the facies 111:5 grainstone is so intensely micritized that the bio- chems are barely recognizeable in thin sections. This micritized interval is succeeded downward by a 2-15 mm thick interval in which both matrix and biochems have been thoroughly replaced by authi genic quartz.

At many places north of Franklin County the undulating post­ unit III surface is penetrated by vertical cracks (burrows ?) up to

6 in. deep which are filled with the overlying "bone"-bearing unit IV wackestone or packstone (Figure 75) 9 even though the surface may itself truncate burrows and fossils in facies III:5> indicating that it was lithified prior to unit IV deposition. Elsewhere, especially in che Marion County to Sandusky County area, this smooth undulating surface Is penetrated by irregular V-shaped cracks up to 14 in. deep which interconnect laterally and which are filled with light-brown dolcnitic mudstone containing "bone" fragments up to an inch lcng

(Figure 76). This burrow-filling material is distinctly different from the overlying basal unit IV wackestone or packstone and probably 197

Figure 75: Unit III-unit IV contact at locality B.

B. Facies IV:2.

A. Facies 111:5. Note the vertical burrows (?) penetrating the upper surface of unit III which are filled with facies IV:2. 1 9 8

Figure 7 6 : Unit III-unit TV contact.at locality.BE.

B. Facies IV:1.

A. Facies 111:5 penetrated by irregular vertical cracks (burrows ?) filled with dolomit'ic mudstone containing scattered "bone” fragments. 199 represents material washed into cracks in the surface long before the initiation of unit IV deposition. Because this fine-grained dolomitic material is much less resistant to weathering than the enclosing facies

111:5 packstone or grainstone the upper 1-2 ft of unit III in weathered exposures appears very cavernous.

Interpretation

The smooth undulating surface which marks the unit III-unit IV centact represents an abraded, probably submarine lithifLed discontinuity surface as was recognized by Bates (1969), who made a detailed study of this surface at locality K in Delaware County and suggested that it formed as a result of intense storm activity. This author believes, however, that the surface represents a very prolonged interval of non- deposition , and possibly even emergence. This is suggested by the highly abraded nature of the surface, the fact that it is in places penetrated by deep interconnecting carbonate mud-filled cracks

(burrows ?) which appear to have been enlarged by solution, and by conspicuous differences in the faunas of facies 111:5 and unit IV.

These differences include the presence of blastoids in unit IV and their absence in facies III:5» and the great abundance of charophyte oogcnia in facies 111:5 and their complete absence from unit IV. Thus, the author suggests that facies 111:5 deposition was terminated throughout central Ohio by a very sudden and significant fall in relative sea level. The resultant sudden change in depositional regimen probably caused the demise of the crinoid dominated facies

111:5 fauna, so that carbonate deposition essentially ceased throughout central Ohio. In this probably near mean sea level area waves generated by prevailing winds apparently interacted with the unconsoli­ dated skeletal sand to produce large scale oscillation ripples as was suggested by Bates (1969). Subsequently, however, prolonged exposure of this oscillation rippled unconsolidated skeletal sand to sea water saturated with CaCO^ probably led to submarine lithiflcation, just as is occurring today in some shallow areas of the Persian Gulf where the substrate is porous and the rate of sediment accumulation is low (Shinn, 1969). Continued oscillatory wave action then resulted in the abrasion of the hard rippled surface. Except for a few boring organisms this hard wave-eroded surface was evidently inhospitable to most normal marine organisms so that little sediment accumulated cn it except for fragmented and abraded phosphatic fish remains. The abrasion of the surface also probably produced much fine carbonate mud, most of which was swept away by the waves and currents, although some became trapped and filled the irregular cracks of uncertain origin which penetrated the surface in places. Although there is no definite evidence suggesting subaerial exposure of this surface, slight falls in sea level could well have resulted in brief periods of emergence.

This rrobably quite long period of non-deposition and submarine erosion in central Ohio was terminated when sea level again abruptly rose and and rapidly inundated the area to near to below wave-base depths.

During this rapid rise in sea level the lithified substrate was further scoured and in some places was penetrated by burrowing organisms, and the loose "bone" material and abraded facies 111:5 fossils which were •201

concentrated into the basal unit IV sediment.

UNIT IV-UNIT V CONTACT •

Description

At most places the unit IV-unit V contact lies between the somewhat llthologically similar facies IV:2 and facies V:l. This contact is most conspicuous in the south-central area, where at most localities facies IV: 2 is truncated by an irregular surface consisting of shallow elongate hummocks which rise up to 3 in. above intervening gully-like areas (Figure 77). The rounded flat-topped hummocks are coated and indurated by an iron-oxide material in which fenestrate bryozoan fronds and crinoid stem sections up to 3 in. long are embedded.

Silicified brachiopod fragments also project through this iron-oxide crust. Also penetrating these hummocks are numerous up to 1 in. long pyrite and spar filled vertical borings. Tne floors of the gullies are neither coated with iron-oxide or bored, however, many of them slightly undercut the adjacent hummocks. This irregular surface is everywhere overlain by the cross-stratified facies V:1 grainstone containing scattered "bone'1 fragments and rounded quartz sand grains, and at locality MCS this grainstone also contains angular to rounded and bored clasts of the underling facies IV:2 packstone (Figure 78).

In the north-central area the facies IV:2-facies V:1 contact is much less conspicuous than In the south due to the greater lithologic similarity of the two facies and the fact that the surface is more regular, although it is still penetrated by pyrite-filled borings 2 0 2

figure 77: Iron-oxide indurated bored', discontinuity surface which terminates unit IV. Locality 0. 203

Figure 7 8 : "Bone’N-frasnent bearing grainstone of facies. V:1 (B) sharply overlying packstone of facies IV:2 (A). locality MCS. Note the hi^ily irregular nature of the contact and the ligjit colored clasts of facies IV:2 inducted in facies V:l. 20H

and Is overlain by a thin concentration of "bone" material.

At locality V in Erie County and locality MCT in Franklin

County facies V:1 is itself terminated by a smooth, channeled surface.

In places at each of these localities this post-facies V:1 surface

coiipletely "cuts out" facies V:1 so that the unit IV-unit V contact is between either facies IV:2 and facies V:2 (at locality V), or

facies IV:2'and facies V:3 (at locality MCT).

Interpretation

The irregular bored surface terminating facies IV: 2 Is a dis­ continuity surface which probably represents a hiatus of considerable duration, possibly even longer than that represented by the post-unit

III surface, as suggested by the fact that restricted Hamiltonian fossils make a sudden appearance in the overlying facies V:l. This hiatus probably resulted from another major rapid regression of the sea similar to that believed to have terminated unit III deposition.

Tnis regression probably resulted in central Ohio becoming a "starved" area very close to mean sea level where there was little or no carbonate deposition and where portions of the sea floor may at times have become emergent "stranded" areas. Except for the iron-oxide ir.curaoion and coatings of the surface there Is no evidence definitely suggestive of subaerial exposure, however, so it is believed that the lithification and corrosion of the surface probably were due primarily to submarine processes. When sea level again rose and initiated facies

V:1 deposition throughout central Ohio the "bone" fragments which had become concentrated on the "starved" surface and eroded clasts of the

lithified substrate were reworked and Incorporated into the basal facies V:1 sediment. PART II

REGIONAL ANALYSIS

206 CHAPTER VII

DEVONIAN CARBONATES OF THE OUTLIER

INTRODUCTION

The Devonian carbonates of the Logan County outlier are poorly exposed. Sections at several localities (Figure 2) were studied, however, which combined enconpass most of the "Detroit River"

("Lucas") and the "Columbus," the two Devonian carbonate units recognized in the outlier by previous workers. Descriptions of most of these sections, as well as of sections which are no longer accessible, were presented by Stauffer (1909) and Moses (1922).

DETROIT RIVER (LUCAS) DOLOMITE

The oldest Devonian carbonate unit in the outlier consists of at least 25 ft of highly dolomltic strata which contain the Detroit River fauna and which are best exposed at the old Piatt quarry near West

Liberty where they are overlain by 2 ft of "Columbus." These strata were assigned to the "Monroe" by Stauffer (1909)j who believed they were Silurian, and to the "Lucas" by Moses (1922), who made no definite statement regarding their age, although he believed the unit was disconformably overlain by the Devonian "Columbus." Carmen (1927, p. 502) referred to the unit as the "Detroit River formation," stating

207 208

that "several exposures of the Lucas dolomite are known, and one

exposure exists that is probably Amhertsburg." like Moses, Carmen

believed that the Detroit River was overlain disconformably by the

Columbus, although he noted (p. 506) that the ’.’Detroit River fauna is

better interpreted as Devonian."

The ’’Detroit River" (’’Lucas") of the outlier consists of thin

bedded, massive to laminated mudstone composed largely of micro-

crystalline dolomite. Many of the massive intervals contain calcite

spar-filled molds of the brachiopod ProsSerella lucasi and small

rugose corals and brachiopods. Some of the laminated intervals appear

to be faintly cross-stratified, suggesting that the lamination is

mechanical in origin, whereas others appear to be algal stromatolites.

The upper portions of some of the laminated beds contain spor-filled

fenestral cavities. Rounded quartz sand grains occur scattered

throughout the unit, but are most abundant in several 3-4 in. thick

beds of sandy, pelletoidal packstone. Such sandy beds are especially

conspicuous in an approximately 10 ft thick interval of the "Detroit

River" exposed at locality BS. Also conspicuous at this locality are

scour structures up to 2 ft across and 0.8 ft deep which are filled

wich intraelastic breccia and cross-stratified dolosiltite. Several

fees of massive, non-sandy microcrystalline dolomite are exposed be­ ne ash the sandy dolostone which probably belong to the Silurian Bass

Islands Group. Unfortunately the contact of this unit with the over-

lying Detroit River is concealed. 209

COLUMBUS LIMESTONE

The "Detroit River" of the outlier is overlain by approximately

40-65 ft of brown massive and in places cherty fine to coarse grained

dolostone which is disconformably overlain by the Ohio Shale. Stauffer

(1909) and Moses (1922) referred to this dolostone interval as the

"Columbus Limestone," although both suggested that the upper part

might actually correlate with the Delaware Limestone of central Ohio.

Summerson and others (1957) and Oliver and others (1967) also regarded

the entire interval as "Columbus."

Moses (1922) divided the "Columbus" of the outlier into three

"divisions" based on general differences in lithology and fauna. He

described the "Lower division," which is 20 ft. thick at Cable,

Champaign County (locality CB), the only place it is completely ex­

posed, as "thick bedded, dark gray fossiliferous limestone" which he

divided Into two "zones" (p. 20). The lower zone, which is 6 ft

thick, consists of a basal three foot interval of "compact, grayish

brown limestone, thin bedded and somewhat banded" and an upper three

foot interval of cherty "gray-brown limestone containing a few corals

and braehiopods" (p. 20, 32). The basal interval contains much quartz

sand in the lower few inches. The upper 14 ft "zone" was described by

Moses (p. 20), as "bluish gray or greenish gray limestone in which harder more siliceous, gray drab pebbles are found locally." It

contains almost no fossils.

Moses (p. 20) described the "Middle division" of the "Columbus"

as "30 ft or less of massive, hard gray, fossiliferous limestone- 2 1 0

containing a few chert nodules." Among the characteristic fossils

(all molds) noted by Moses in this "division" were "Spirifer" gregarlus

and Calcisphaera nobusta, the latter corresponding to the author's

charophyte oogonia. Succeeding the "Middle division" is the "Upper

division," described by Moses (p. 21) as "forty-five feet of gray to

brown, grainy to crystalline magpesian limestone." Moses estimated

that the total thickness of these three divisions, and hence the

"Columbus," might be as much as 85 ft in the eastern part of the

outlier. The thickness of the "Columbus" appears to decrease in

in thickness from south to north and from east to west in the outlier, however, so that at Cherokee Run.(locality CR) in the northwestern part of the outlier only 36 ft of "Columbus" (all "Upper division") is present between the "Lucas" (Detroit River) and the Ohio Shale.

Furthermore, whereas at Cable the "Lucas" (Detroit River) is succeeded by the "Lower division" of the Columbus, seven miles to the northwest

at the Piatt quarry (locality PT) 2 ft of the "Middle division"

containing much quartz sand rests directly on the "Detroit River."

These relationships led Moses to postulate that "the successively higher layers of the Columbus overlap northward" and that "the thinning wesov.ard is again due to the westward overlap of successively higher strata."

The best section of the "Columbus" in the outlier is at an operating quarry 1.5 miles south of East liberty, Logan County where approximately 55 ft of the unit are exposed beneath the Ohio Shale,

The entire interval of "Columbus" at this locality is dolostone consisting 2 1 1

of a hypidiotopic mosaic of centi- to decimicron-sized dark centered,

clear rirnned dolomite rhorrbs. However, the presence of relect textures and structures, the nature and abundance of fossil molds, the abundance

and distribution of chert, and variations in the color, porosity, and texture of the dolostone permit recognition of a number of distinct intervals which can be correlated directly with the vertical sequence of facies extending from near the base of unit III to near the top of unit V exposed in the quarries near Marion in the central outcrop belt. Furthermore, the discontinuity surfaces which mark the unit

III-unit IV and unit IV-unit V contacts, and the possible volcanic ash bed in the lower part of unit V in central Ohio are also recognizeable in the "Columbus'1 at East Liberty. The relationships of these thoroughly dolomitized facies intervals to Moses’ "divisions" are discussed below.

The East Liberty quarry is divided into two levels by a prominent bench 22 ft above the floor of the lower level. Moses assigned the entire section of "Columbus" exposed in the lower level to his

"Middle division." The author has recognized three distinct dolomitized facies intervals in this level. The lowest extends from the floor of the quarry to 6 ft above the base and consists of gray mdium grained dolostone which contains scattered brachiopod and rugose coral molds.

It is succeeded by approximately 10 ft of gray medium grained dolostone which contains numerous fossil molds of brachiopods, large favositid corals, small rugose corals, bulbous stromatoporoids, gastropods, and charophyte oogonia. The latter are most abundant, along with the brachiopod Brevispirifer gregarlus, in the lower part of this 2 1 2

Interval. This fossiliferous dolostone interval is overlain by 5-6 ft

of brownish-gray very dense unfossiliferous dolostone which contains '

several bands of white nodular chert. A few thin-shelled brachiopods

occur in the chert, but no fossil molds were observed in the dolostone.

These three intervals correspond respectively to the intervals of facies 111:1, 111:2, and III':1! at locality H in Marion County in

central Ohio,

The portion of the "Columbus" exposed in the upper level of the

East Liberty quarry was assigned entirely to the "Upper division" by

Moses. It can be separated into three main Literals which are

indicated in Figure 79. The lowest interval consists of 6 ft of gray massive granular appearing medium grained dolostone. Small molds of

crlnoid fraenents are quite conspicuous in this interval, but except

for a few molds of solitary rugose and colonial corals, larger fossil molds are unccmnnon. This interval represents thoroughly dolomitized

facies 111:5 calcarenltic packstone and/or grainstone and like the interval of that facies forming the upper part of unit III in central

Chio is abruptly terminated by a sharp undulating discontinuity surface. Also, as in central Ohio, at locality EL this surfhce Is overlain by a 3 ft thick very fossiliferous interval which contains numerous "bone" fragments in the lower few inches. Molds of fossils found in facle3 IV:2 in central Ohio are quite prominent in this interval, including large fenestrate bryozoans, the large brachiopod

Paraspirifer acuminatus and the branching coral Eridophyllum. serlale.

A few inches from the top of this interval white chert nodules occur 213

Figure 79: Upper part of the "Coluntous" In the outlier. Locality EL.

C. Uhit V containing a prominent "bone-bed" at the base and a possible volcanic ash bed-.-2-3 fb above the base.

B. Unit IV containing a prominent "bone-bed" at the base and terminated by a very irregular bored discontinuity surface.

A. Upper part of unit III terminated by a smooth undulating discontinuity surface. 214

which contain escallently preserved packed skeletal fragments, indicating

that the chertification preceded dolomitization and that the original

texture wa3 packs tone. This dolcmitized facies IV: 2 interval is

terminated by a very irregular discontinuity surface which is overlain

by 3-6 in. of darker colored, very porous and fossillferous dolostone

containing numerous "bone” fragments and corresponding to facies V:1

of central Ohio. A sharp, slightly stylolitized surface terminates

this interval. Ihia surface is succeeded by 27-30 ft of brovmlsh-gray

thin-bedded fine to medium grained cherty dolostone which extends up­ ward to the Ohio Shale. The lower 2.3 ft of this interval, beneath a prominent 0.5-1 in. thick clayey shade seam, is slightly limiter in

color than the dolostone overlying the clayey shale seam and contains a few solitary rugose coral and brachiopod molds and also a thin band of bryozoan-rlch white chert. The clayey shale seam marks the most prominent plane of separation above the major quarry bench and almost certainly represents the possible "Tioga Bentonite" also found near the base of unit V in the central outcrop belt. Except for a few scattered brachiopod and solitary rugose coral molds fossils are un­ common above the clayey shale seam, althou^i lenses containing crudely stratified calcltic crinoid debris and scattered sand-sized "bone" fragrents occur in the 2-5 ft thick interval of dolostone immediately beneath the Chio Shale. Lenses of partially pyritized quartz sandstone up to several inches thick occur immediately belcw the shale, filling in small scours and vertical burrows up to an inch lcng in the upper surface of the dolostone. Ihis entire post-facies V:1— pre-Chio Shale interval at locality EL correlates with the post-facies V:1 interval 2 1 5 ■ of unit V in central Ohio and probably represents dolomitized slightly

argillaceous mudstone and wackestone of facies V:^. Ihe "bony"

crinoidal lenses near the top my correspond to facies V:5 of central

Chio.

STRATIGRAPHIC ANALYSIS

Since unit V of central Chio coincides with the Delaware Limestone most of Koses ’ "Upper dlvision” of the "Columbus" in the outlier

actually correlates with the Delaware and not with the upper part of

the Colurrbus of central Ohio. Furthermore, the fact that in spite

of intensive dolamitization the same vertical sequence of acies which

characterize the unit III-unit V interval at places in central Chio belt can be recognized in the "Columbus" at locality EL in the outlier indicate that throughout unit III-unit V time the same general deposltional conditions prevailed in both areas. Probably this was also the case during the time of unit II deposition since the "Detroit

River" of the outlier is indentical in lithology and fauna to facies

11:3 of north-central Chio. In north-central Ohio, however, facies

11:3 succeeds up to 100 ft of dolomitic unit I strata, whereas in tn= outlier the "Detroit River" directly overlie3 the Silurian Bass

Islands Group. Ihus, either unit I was never deposited in the outlier, or if it was, It was completely removed by pre-Detroit River (unit II) erosion. Since facies 11:3 probably represents deposition in a more restricted and probably shallower area of the sea than facies 11:1 and 11:2 it seems likely that immediately following the unit II transgression the sea in the outlier area was, as it was in north-

central Chio, shallower and more restricted than in south-central Chio.

It is further suggested that in the southeastern part of the outlier

unit III directly overlies not the "Detroit River" (facies 11:3)*

but several feet of facies 11:1 which in this area intervenes between

facies 11:3 and facies 111:1. This contention is based cnthe fact

that only the lower 3 ft of Moses' lower "zone" of the "Lower division"

at locality CB actually represents facies 11:3 and the fact that the

upper cherty, bituminous, and vsryfossillferous interval of the lower

"zone" is dissimilar to any lithology in eithr facies 11:3 or unit III

of central Ohio, being instead sorrewhat similar to facies 11:1 of

that area. This relationship is further indicated by the fact

that Surrmerson and others (1557) found an abrupt increase in quartz

sand content at the base of Moses1 upper "zone" of the "Lower division"

at locality CB, sugg23ting that the abrupt but irregular contact of the

upper and lower zones represents the unit II-unit III contact. If this

interpretation is correct then facies 111:1 only coincides with the

upper 14 ft of Moses1 "Lower division," and since an 8 ft interval of

facies 111:1 is exposed beneath facies 111:2 at locality EL, where

- a 58 ft thick section of "Colunbus" is exposed beneath the Chio Shale,

the total thickness of the unit III-unit V interval in tixe eastern

part of the outlier is probably only about 64 ft, approximately Its

thickness in central Ohio, 'xhe fact that the facies 111:1 interval

is absent in the central part of the outlier, where instead facies H I : 2

rests directly on the "Detroit River" (facies 11:3), is believed by 217 the author not to be the result of westward overlap over a dlsconformable surface as was suggested by looses, but is instead believed to represent the establishment of different unit III facies in different topographic areas following the rapid sea level rise which terminated deposition of the unit II facies, Just as occurred in central Ohio (Figure 80). 2 1 8

Figure 80: Schematic cress section from the outlier to north-central Ohio showing inferred stratigraphic relations between the Silurian Bass Islands Group and units I and II of the Devonian carbonate sequence and inferred facies distri­ bution during early unit III time. o o LU QQ I OQ (SKELETAL SAND) MEAN SEA LEVEL FACIES 111:2 DEPOSITION I 00 Crawford Co. Seneca Co. UNCONFORMITY MEAN WAVE BASE SEA FLOOR HORIZONTAL SCALE-MILES • (FOSSILIFEROUS MUD) FACIES 111:1 DEPOSITION Marlon Co SILURIAN-"DEVONIAN" ■JCr « * < > « < ■JCr * b e 3 -ft LAKE INDEX MAP ^ ERIE L*' r s . ' H r | F r 1 /i /i M I#:if tm w . BH

(SKELETAL SAND)

I LU r* m GROUP Belt Logan Co. *

Central O u t c r o p FACIES 111:2 DEPOSITION * J c s

% % V^/ MICH* 1 P T ' i l l Outlier,'' ^ l l | f cu H SILURIAN BASS ISLANDS

Figure 80. CHAPTER VII

PRE-TRAVERSE DEVONIAN CARBONATES OF NORTHWESTERN CHIO

INTRODUCTION

Three majro pre-Trav&rse Devonian stratigraphic units are currently recognized in northwester Ohio: the Sylvania Sandstone

Member of the Detroit River Group, the "undifferentiated Detroit

River dolomite,1' and the Dundee Limestone (Janssens, 1970b).

SYLVANIA SANDSTONE

In northwestern Chio the Sylvania Sandstone is a 0-50 ft thick unit of cross-stratified quartz sandstone and fossiliferous sandy dolostone which unccmformably overlies the Silurian Bass Islands Groiqp and is conformably overlain by the "Detroit River dolomite." The

Sylvania thickens northward into Michigan, where it consists of up to

300 ft of predominantly very pure, cross-bedded sandstone that in places overlies the Emsian Bois Blanc Formation (Landes, 1951). There is a definite linear trend of maximum thickness of the Sylvania in Michigan which extends in a north-northwest direction from Monroe County in the southeast comer of the state to Clare and Gladwin Counties in the north-central pare (Landes, 1951, p. 15, Figure 9). The Sylvania thins 220 221 rapidly away from this area so that in western and northeastern

Michigan the "Detroit River dolomite" rests directly cn the Bois Blanc rather than the Sylvania.

The cross-bedded sandstone portions of the Sylvania consist of packed, well-rounded fine and medium sand-sized quartz grains which are cemented by dolomite, calcite, and authigenic quartz. A few well-rounded chert, feldspar, and heavy mineral grains also occur.

Such cross-bedded sandstone forms most of the unit where it is thickest, but where it is thinner, as in northwestern Ohio, generally only the lower half is sandstone, the upper portion consisting of sandy dolostone and dolomitic sandstone which contains molds of brachiopods, gastro­ pods, and corals identical to those in the overlying "Detroit River dolomite" (Carmen, 1936, p. 259-261). Atypical development of the

Sylvania-"Detroit River dolomite" contact occurs at the Prance Quarry at Silica (locality SL) where the two units are entirely gradational over an interval of approximately 8-10 ft. At the Pugh Quarry in

Y/ood County the contact is very atypical, however. There several feet of cross-bedded and ripple-marked Sylvania sandstone exposed in the quarry sump, are abruptly overlain by 2 ft of'sand-free, gypsum crystal-bearing mudstone which forms the basal bed of the "Detroit

River dolomite."

Many authors have discussed the source and origin of the Sylvania elastics (Sherzer and Grabau, 1909* p. 618-86; Carmen, 1936, p. 262-

263; Landes, 1951, p. I1*; Briggs, 1959* p. *0-^6), and all have agreed that the sand was probably derived from already texturally and mlneraloglcally mature Cianforlan and Ordovician sandstones exposed in

ta*i area of present-day Wisconsin. There has been somewhat less con­

sensus as to the precise origin of the Sylvania, however. Sherzer and

Gradau (1909, p. 79) proposed that the Sylvania represented largely

an aeollan deposit, the upper part of which wa3 reworked by marine

agents. This hypothesis was based cn their study of the Sylvania where

it is thickest in southeastern Michigan and consists largely of cross­

bedded sandstone. Other authors, however, have postulated that the

Sylvania i3 largely a marine blanket sand formed in the beach environ­ ment of a southward trangressing sea so that it is progressively younger to the southeast (Carmen, 1936; Ehlers, Stumm, and Kesling,

1951} Briggs, 1959; Hatfield and others, 19o8), Janssens (1970b) - apparently .also favored a largely marine origin for the Sylvania stating (p. 14) that "the earliest Middle Devonian marine transgression of northwestern Chio resulted in deposition of the Sylvania Sandstone, although he also noted that "in places this deposit may be aeolian material that was reworked by the transgressing sea,1' a view that was also supported by Carmen (1936).

This author supports the ideas of a confined aeollan-marlne origin of "he Sylvania and that most of the upper part of the Sylvania in northwestern Ohio is marine. However, the definite linear trend of thickness of the Sylvania in eastern Michigan, the fact that the

Sylvania is not everywhere present at the base of the Detroit River, and the fact that Carmen's (1936) proposal that the Sylvania becomes younger from northwest to southeast was based in large part on a 223 misunderstanding of Detroit River stratigraphy, tend to svpport

Sherzer and Grabau's (1909, p. 79) contention that the sylvania was originally almost entirely an aeolian deposit, the upper portion of which was reworked by the transgressing Detroit River sea. Since there is little sand at the Bois Blanc-Detroit River contact in the central Michigan Basin it seena probable that either deposition of the

"Detroit River dolomite" began in this region before the Sylvania dune fields in eastern Michigan were "tapped" by the transgressing sea or that they lay beyond the limits of marine dispersal of the aeolian sand.

According to Briggs (1909, p. 43) initial deposition of the

Sylvania sands .took place following the time of deposition of the

Emsian Boi3 Blanc Formation. The precise age of the unit is uncertain, however, Fagerstrom (1967, p. 1187) stating that the "brachiopods, goniatltes and ccnodcnts are indefinite, raj rely bracketing the age as between the lower Emsian and Lower Elfellan."

DETROIT RIVER DOLOMITE

The "undifferentiated Detroit River dolomite" includes all of the Detroit River Group which succeeds the Sylvania Sandstone

(Janssens, 1970b, p. 7). It is everywhere disconforsnably overlain by the Dundee Lime3tone. Janssens' (1970b, p. 9) laopack map of the

"Detroit River dolomite" in northwestern Ohio shows that it ranges in thicloiess from 24 ft at the Auglaize quarry in Paulding County, near the Ohio-Indlana border, to 175 ft in the subsurface of Fulton County, Just south of the Ohio-’iichigan border. At the Pugh quarry

in Wood* faunty the "Detroit River dolomite" is 55 ft thick. Approxi­

mately 25 miles to the north at the Prance quarry at Silica (locality

SL) it is approximately 130 ft thick, however. This progressive north-

vrard increase in thickness of the "Detroit River dolomite11 continues

into Michigan and, in the center of the Michigan Basin it is over

1,000 ft thick (Landes, 1951, p. *J8, Figure 6). In western and

northern Michigan and in southwestern Chtario the "Detroit River

dolomite" directly overlies the Bois Blanc Formation, rather than the

Sylvania Sandstone as in northwestern Ohio and eastern Michigan. Landes

(1951) and Sanford (1967) regarded the Bois Blanc-Detroit River contact

in the Michigan Basin as unconformable.

Ehlers, Stunm, and Kesling (1951) sparated the 130 ft thick post-

Sylvania Detroit River interval at locality SL into three divisions,

which they identified in ascending stratigraphic order as the

Archertsburg Dolomite, tie Lucas Dolondte, and the Anderdon Limestone

formations which in the Detroit River area of Michigan and Chtario are

both iithologically and faunally distinct. Fagerstrom (1971, p.. 8)

argued, however, that in terrra of rock-stratigraphic terminology the an:ire post-Sylvsnla Detroit River interval at Silica should be

considered as "Lucas," as it was named by Prosser (1903, p. 5^1), with the three formations designated by Ehlers, Stuiran, and Kesling (1951) actually representing "biostratigraphic subdivisions." There is a rather significant difference in lithology between the Amherstburg ; ' interval and the combined Lucas-Anderdon interval, and a difference in 225

carbonate mineralogy between the Lucas and Anderdon Intervals, however,

30 that these names are still convenient to use in discussing the

section.

The basal 20 ft thick Airfliert3burg interval consists of brown

to gray-brown sandy dolostone which is gradational with the under­

lying upper dolondLtic portion of the Sylvania Sandstone, The quartz

sand decreases in abundance from the base to the top of the Amhertsburg

interval, and tends to be concentrated in beds up to 1 ft thick which

alternate vdth less sandy beds containing molds of brachiopods and

corals identical to those found in the upper dolanitic portion of the

Sylvania. Thus, it seems probable that the Amhertsburg reflects

deposition in a moderately agitated probably nearshore environment

similar to represented by the upper marine portion of the Sylvania.

The Amhertsburg interval is succeeded by approximately 110 ft

of thin-bedded, massive to laminated mudstones and skeletal-poor wacke3tones. The lower 8*J ft thick Lucas part of this interval is e ssentially all dolostone. The upper 26 ft thick Anderdon part contains

several beds of laminated lime mudstone intercalated with more dolanitic beds. This thick Lucas-Andendon interval i3 both llthologically and

faunally similar to facies 11:3 in north-central Ohio and probably also represents deposition in a shallow, highly restricted and saline portion

of the sea. Thus, the transition from the Amhertsburg interval to the

Lucas-Anderdcn interval probably represents shallowing-and increased

restriction of circulation, A number of differences between the Lucas-

Anderdcn interval at locality SL and facies 11:3 in north-central Chio 226. were noted, however. Uiese are as follows:

1) Sandy intervals, which are so distinct and conspicuous in

facies 11:3 in north-central Chio, are less comrm and

rnuch less well developed in the Anderdon-Lucas interval

at locality SL.

2) Several 1-4 ft thick breccia beds composed of jumbled

appearing large dolostone fragnents occur in the Lucas

interval at locality SY. In places such breccia fills

sink-like structures up to 10 ft across and 8 ft deep.

Ihese breccia beds have 3erved as a locus for secondary

mineralization, with many of the cavities between the

dolostone fragments being lines by calcite crystals,

celestite crystals, and various sulphides. No such

mineralized brecclated intervals were observed in facies

11:3 in north-central Ohio.

3) Gypsum crystals and molds and calcite pseudomorphs of

gypsum crystals are much more abundant in the Lucas-

Ancerdcn interval at locality SL than in facies 11:3 in

north-central Ohio. Furthermore, Janssens (1970b, p. 7)

noted that both gypsum and anhydrite are quite common in

the "Detroit River dolomite" in the subsurface of north­

western Ohio.

4) Scour surfaces up to several feet across and a foot deep

which are filled with cross-bedded intraclastic calcarenite

are quite conspicuous at places in the Lucas-Anderdon 227

interval at locality SL, but such large-scale scour

surfaces were not observed in facies 11:3 of north-central

Ohio.

5) Etefinite oolites were not observed in facies II; 3 in

central Ohio. An approximately 1.5 ft thick; bed of

re crystallized micro-cross laminated oolitic calcaranite

occurs in the upper part of theDucas interval at locality

SL, however (Figure 8l). s \ Stromatoporoid biostrcmes do not occur in the Lucas-

Anderdcn interval at locality SL, whereas they were ob­

served near the top of facies H : 3 at several localities

in north-central Ohio,

7) A greater portion of the Lucas-Anderdcn interval at

locality SL consists of laminated mudstone and algal

3tromatolltic bound3tcne, than does facies 11:3 in north-

central Ohio, which is dominated by dolomitized

bituminous banded mudstones and skeletal-poor wackestones.

■Ihese differences suggest that the Lucas-Anderdon represents deposition in a somewhat n»re restricted, saline, and probably shallower portion of the sea than facies 11:3 so that slight falls in

sea level would have resulted in much more frequent and widespread emergence of the forner than the latter. Furthermore, the brecciated zones in the Lucas suggest that some of these emergent periods were prolonged, resulting in extensive ground water solution of evaporites and collapse of the overlying strata, as v/as suggested by Janssens 228

Figure 8l: Negative thin section print of dolomitized oolitic calcarenite from the "Lucas” protion. of the Detroit River. Locality SL. Scale equals 5 mm. 229

(1970b, p. 7). The greater quantity of quartz sand in facies 11:3 in

north-central Ohio than in the Anderdon-Lucas at Silica suggests that

the area of aeolian £|ylvania sandstone accumulation in northwestern

Ohio and southeastern Michigan was probably still emergent during the

tine of facies 11:3 deposition in north-central Ohio, but that this area was almost completely submerged and buried by carbonate sediments by the time Lucas-Anderdcn deposition wa3 initiated in Ohio.

The 55 ft thick, interval of the "Detroit River dolomite" at the Pugh Quarry (locality PG), is most similar to the Lucas interval at locality SL, with neither the lower sandy Airhertsburg interval or upper more calcareous Anderdon interval being present. This suggests both that more of the Detroit River was removed by pre-Dundee erosion and that deposition of the "Detroit River dolomite" began under more restricted conditions and/or later, at locality PG than at locality SL.

Fagerstrom (1967* p. 8, 71, 75) has demonstrated that most of the post-Syivania Detroit River in northwestern Ohio is early Middle

Devonian (early Eifelian), although he noted that the Amhertsburg may be late Early Devonian (late Emsian).

DUNDEE LIMESTONE

The Dundee Iime3tcne of northwestern Ohio and southeastern

Michigan includes all strata lying between the Detroit River Group and the Silica Formation of the Traverse Group. Its maximum thickness in northwestern Ohio is 103 ft in the subsurface of Fulton County

(Janssen3, 1970b, p. 13). Twenty miles to the east at locality SL it 230

Is only 62 ft thick. The contact of the Dundee with the underlying

"Detroit River dolomite" is abrupt and at most places the lower 3 to 6 in.

' of the Dundee contains much rounded quartz sand and small rounded clasts

of the underlying "Detroit River dolomite." In places this sandy

material, fills in shallow depressions and cracks in the underlying

surface. This contact has long been regarded as a major disccnformLty

(Grabau and Sherzer, 1910; Ehlers, Sturun, and Kesling, 1951).

Janssens (1970b) divided the Dundee in northwestern Ohio into

three parts which he referred to as the "lower Dundee," the

"upper Dundee," and the "lithographic Dundee Limsstone." Janssens*

terminology is somewhat misleading, however, since the "lithographic

Dundee Limestone" actually fome the lower part of the Dundee near

the Ohio-Indiana border, occupying the sane stratlgraphic position as

the "lower Dundee" In the Lucas County area.

The "lower Dundee11 is *12 ft thick at locality SL where it

dis conformably overlies the "Detroit River dolomite" and grade a abruptly

upward into the overlying "upper Dundee." At locality PG only 28 ft

of "lower Dundee" is exposed above the "Detroit River dolcmit." It

consists of massive light tan to dark-brown color banded porous dolostone

•which is composed of a hypidiotoplc mosaic of 0.10 to 0.20 inn dark

centered, clear rdranred dolomite crystals (Figure 82). The intervals

of slightly different colored dolostone appear to be texturally and

mineraiogically identical, although some of th thinner darker colored

bands contain much fine disseminated pyrite. The contacts of these

Intervals of different colored dolostone are commonly penetrated by up 231

Figure 82: "Lower Dundee" Limestone. 'Locality PG. The Detroit River- Dundee contact is just below the'base of the picture. Note the dark bituminous bands which are penetrated by vertical burrows in places. to 3 In. long vertical burrow3, The upper few feet of the lower

Dundee expo3ed at locality PG displays relict lamination and in some places appears to be cross-bedded. Occurring within this interval of relict laminated dolostone are white chert nodules. The chert is extremaly fossiliferous, containing small gastropods, trachiopods, orthoconic cephalopoda, tentaculites, trilobites, disarticulated crinoid stem columnals, and o3tracodes. Also very conspicuous and abundant are charophyte oogonia. The dolostone surrounding these chert nodules is also very fossiliferous, but the fo3sil3 are preserved as largely unidentifiable molds. This fossiliferous dolostone occurs as discontinuous lenses within the relict laminated dolostone interval.

The excellent preservation of the fossils in the chert compared to those in the dolostone indicates that chertifLcation preceded dolonitization.

!'5o3t samples of the "lower IXcndee" yielded 2-4 percent total insoluble residue, with most of the residue being angular quartz silt, with minor clay and pyrite. A sample from the very base of the "lower

Dundee" at locality PG yielded 9 percent insoluble residue, most of it- rounded quarts, with some chert. Also present in most residues were rany spores and scolecondonts.

Janssens (1970b, p. 17) proposed a "tidal environment" for the

"lower Dundee." However, since there is no evidence of tidal activity or periodic emergence this author favors a semi-restricted permanently submerged lagoonal-like environment of deposition. This low-energy and probably ratiier highly saline environment was inhabited only by 233 soft-bodied polychaete annelids which produced the few vertical burrows in the mud substrate and yielded the scolecodont remains. Occasionally, however, storms swept small fossils and fossil fragments from neigh­ boring more normal marine areas resulting in the skeletal debris lenses.

The "lithographic Dundee Lime stone" forms the lower part of the Dundee just east of the Ohio-Indiana border and apparently grades to the east into the "lower IXondee" in the Kenry County-Fulton County area (Janssens, 1970b, p. 11, 12). At the Auglaize quarry in Paulding

County the "lithographic Dundee Limestone" consists of 33 ft of inter­ bedded highly calcareous light-gray to brown unfossiliferous laminated mudstones and pelletoidal and oolitic packstones and sharply overlies the generally similar appearing, but darker and more dolomitic "Detroit

River dolomite." The "lithographic Dundee" probably represents depo­ sition in shallower, but somewhat more agitated waters than the "lower

Dundee" as indicated by the presence of oolites and peiletoids, the latter probably representing small rounded intraclasts since there is no evidence of a fauna which could have produced fecal pellets. The above fossils probably resulted from even higher salinities than that of the senrL-restrlcted "lower Dundee" environment and to frequent episodes of subaerial exposure indicated by fenestral sturctures.

Both the "lithographic Dundee Limestone" and the "lower Dundee" are very abruptly but conformably overlain by the very fossiliferous limestones of the "upper Dundee," which is 20 ft thick at locality SL.

Texturally the "upper Dundee" ranges from calciruditlc wackestcne to calcarenitlc paclc3tone and grainstcna, with the different textural types being intimately intsrbedded and generally gradational with one another (Figure 83). The "upper Dundee" contains a diverse and abundant macro fauna dominated by brachiopods, pelecypods, gastropods, and solitary rugose corals. Thin section study-showed that ai the average *i9 percent of the sand-sized biochems consist of echinoderm fragments, indicating that crinoids were also probably major elements of the fauna, viith the rest being mainly brachiopod, bryozoan, and indeterminant fragments. Charophyte oogonia were also noted in most thin-sections of calcarenitlc packstones and gralnstones. In the wackestones the macrofossils are largely whole, nan-abraded and essentially in situ. Horizontal tube-like burrows and thin shale partings also occur in the wackestone3. Kacrofossils in the packstones and gralnstones tend to be fragmented and somewhat abraded, suggesting intensive reworking by waves and currents. Much neamorphic grain growth spar occurs in the packstones, mo3t of it forming syntaxial oT."3rgrowths around eciiinodem fragments. Euhedral dolomite crystals averaging 0.13 mn in diameter partially replace the fine carbonate maurix as well as the neomorphLc spar. The dolomite crystals are most abundant where the matrix is very argillaceous. The fine insoluble residue content of the "upper Dundee" averages 4 percent and consists rrostly of illitic clay with minor amounts of fine quartz silt and pyrite. Chert was not observed. Partially silidfied fossil fragaents are very ccranon though. The "upper EXmdee" at locality SL is sharply overlain by the very argillaceous limestones of the Silica Formation. Although there is no physical evidence of emergence or erosion at the 235

Figure 83: Negative thin section print'of fossiliferous packstcne from the "Upper Dundee1/". Locality SL. :Brachiopod fragments are the dominant biochem. Scale equals 5 nm. 236. top of the Dundee, the IXmdee-Sllica contact Is believed to represent an unconformity (Janssens, 1970b, p. 10), The diverse and abundant fetma of the "upper Dundee" Indicates deposition In a normal narlne environment well supplied with oxygen and nutrients. Occasionally energy conditions were so high that all fine mud was winnowed away and the skeletal debris was highly frag­ mented, resulting In the accumulation of packed mud-free skeletal sands which were later cemented by calcite spar to form the gralnstone beds. The more abundant wackeatcnes and packstones Indicate, however, that at most times somewhat lower energy conditions prevailed,

STRATCGRAPHIC ANALYSIS

The lack of an unequivocable datuu permitting precise correlation has resulted In considerable disagreement as to the stratigraphlc relationships of the Lower and Middle Devonian sections on the opposite flanks of the Findlay Arch In Ohio, the fundamental point of controversy being the relationship of the Colunbua of central Ohio to the Detroit River Group (Sylvania Sandstone and "Detroit River dolomite") of northwestern Ohio, There are two general schools of thougit regarding this relation­ ship, The first is that Columbus deposition completely post-dated

Detroit River deposition. This was the conmon belief prior to the mld-lS^O's and was based largely on the presumed Early Devonian age of the Detroit River fauna and the belief that the strata now called Dundee is northwestern Ohio correlated with the Columbus of central Ohio. In spite of the demonstration of the correlation of the Dundee with the Delaware and not the Colunbus of central Ohio by Cooper and others (1942, p. 1754) and Ehlers (1945, p. 112) and the deter­ mination that at least the upper part of the Detroit River contained restricted Middle Devonian fossils (Fagerstrom, 1971, p. 75), several authors have continued to support the hypothesis that the Detroit River and the Columbus are distinct ttme-stratigraphic units, Kerr (1950) assigned the approximately 150 ft thick Interval between the Silurian Bass Islands Group and the Colunbus In a core Dram north-central Ohio entirely to the Detroit River Groip. He further correlated the 3 In. sandstone at the base of this Interval, the overlying 100 ft of tan cherty dolomite, and the upper 50 ft of sandy heterogeneous limestone and dolostone with the Sylvania Amhertsburg, and Lucas of northwestern Ohio respectively, believing that the Detroit River and Columbus were everywhere separated by a regional disconformity beneath which the Detroit River progressively thinned from west to east across northern Ohio, a view also supported by Carmen (1957) and Dow (1951). Sanford (1967* P. 985) likewise postulated that the "Columbus Limestone of Sandusky, Ohio and Pelee Island, Ontario are the basal coarse clastic limestone facies of the Dundee Formation" which "grade southward in Ohio to dark brown aphanltic limestone of the Delaware limestone which In turn lies with dlsconfbrn&blfi contact upon the true Columbus limestone at the type section." Although most authors who have supported the theory that the Columbus and Detroit River Group are distinct time-stratlgraphic units 238 t have also supported the ccnoept of a widespread period of emergence aid erosion having followed Detroit River deposition, Carraen (1927, p. 506) recognized that the Detroit Rlver^Columhus contact in narth- -central Ohio was not a disccnformity and stated that In that area "deposition continued unbroken t c m Lucas Into Columbus time," The second school of thought regarding the relationship of the Detroit River to the Columbus Is that they represent at least In part ccntenparanaous deposition, nils was suggested first by Ehlers (In Landes, 1951, P. 19), who postulated that the "Lucas sea" Initially extended across northern Ohio, but that subsequent emergence of the Findlay Arch resulted In the restriction of this highly saline sea to the Michigan Basin and Initiation of Colunbus deposition In the former area of Lucas deposition east of the Findlay Arch* Thus, according to Ehlers1 theory deposition of the Colunbus of central Ohio and the iqpper part of the Lucas ("Detroit River dolomite") of northwestern Ohio may have been contemporaneous, but In separate basins. Briggs (1959, p. 46, 53), proposed that It was not emergent areas which caused the highly restricted conditions of the Detroit River

(Lucas) sea but that Instead the restriction was due to coral and £ strccatoporoid banks which formed barriers around the margin of the

Michigan Basin beginning In "late Bois Blanc and Anfcertsburg time" so that "the Detroit River sea was a boreal 3ea that was largely disconnected from the more southexnly Columbus sea lh Ohio and Indiana." This view was supported by Sparling (1965, P. 158-160), who postulated that the very fossiliferous basal few feet of the '239 Columbus at locality MH in Ottawa County In central ( M o represented a northward and westward migrating "coralline bank" v M c h farmed the boundary between "marine and restricted hypersaline ecologies," representing respectively by the overlying Columbus (unit X U ) and underlying "Luca?" (unit U)« Janssens (1968, 1970a) has presented stratlgraphlc evidence which also Indicates that the Detroit River and Columbus may represent contemporaneous fades, Biostratigraphic evidence suggesting that the Detroit River Is essentially a "Michigan Basin fades" of the Columbus has been discussed by Oliver and others

(1967, p. 1018-1019) and Ragerstrcm (1967, p. 71). This author supports both the correlation of the Dundee of northwestern Ohio with the Delaware (unit V) of central Ohio and the Idea of a fades relationship between the upper Coliatbus (units III-IV) of central Ohio and the post-syivanla Detroit River of northwestern Ohio. Unlike the previous workers who have supported such a facies relationship, however, the author does not believe that the pre-Columbus Devonian Interval (unit I-unit II Interval) of central Ohio correlates with any portion of the Detroit River of north­ west Ohio. Instead the author believes that unit I of central Ohio (Kerr’s (1950) "Amhartsburg Dolomite") correlates with the Etesian Bois Blanc Formation of the central Michigan Basin and eastern Ohio subsurface, which is absent In northwestern Ohio, and that the fades U s 3 of north-central, which contains the Detroit River fauna and much quartz sand, was deposited while the area of aeolian syivania sand accumulation In northwestern Ohio and southeastern Michigan was still emergent, and hence prior to initiation of deposition of the "Detroit River dolomite." Kais, only the unit I U - m l t IV interval (Columbus) In north-central Ohio is believed to correlate with the dolomite por­ tion of the Detroit River in northwestern Ohio* Not only are relation­ ships most consistent with the available biostratigraphic data, but they are sensible In terms of the areal and stratlgrephlc distribution of environmental units (facies) and In terms of the development of the entire region with time. CHAPTER IX

EEVQNIAN CARBONATES OF TOE EASTERN OHIO SUBSURFACE

INTRDCUCTION

Devonian carbonates of probable Einslarv-Elfellan age are present In the subsurfaee of eastern Ohio where they collectively form the "Chandoga" (Janssens, 1969)* throughout such, of eastern Ohio the "Chandoga" dlsccnforroably overlies Silurian dolcsnttea. In eastern-* most Ohio though, the "Chandoga" dlsccnformably overlies either Lower Devonian "rocks of Helderberg age" or the Crlskany Sandstone (Janssens, 1969)* 3h southeastern Ohio the "Ctaandoga" Is 30-100 ft thick and grades eastward Into the Huntersville Chert near the Qhio- Vfest Virginia border (Dennison, 1969; Janssens, 1969)* 3n north­ eastern Ohio the "onsndoga*1 is much thicker, averaging 200-230 ft (Dow, 1961) and Is divisible Into three units; the Beds Blanc Formation, the Columbus Lime a tone, and the Delaware Limestone.

BQIS BLANC FORMATION'

Ehlers (19*15, p. 80-109) Introduced the stratigraphic name "Bols Blanc" for approximately .350 ft of presumed Chandogsn age strata exposed on and In the vicinity of Bols Blanc Island In the Mackinac 241 2*12. Straits In northern Michigan, tonkin and tonkin (1973) divided the "type” Bols Blanc into three lithologLc units: 1) a lower cherty and in places caralllferous unit of probable Einsian age; 2) & middle unit of thin-bedded limestone containing abundant corals and stxmatoporoida of Elfallan age; and. 3) an upper limestone unit containing much Band at the base and also of Eifelian age. In Chin the name "Bols Blanc” was first used by Newman and Woodhams (195*0 for 63.5 ft of "very cherty, fine grained, ligjit to medium brown limestone” which overlay the Qrlslcany Sandstone and was overlain by the Columbus Limestone in a core studied by them from Lorain County near Lake Erie. Dow (1961) recognized 60-140 ft of Bois Blanc in a number of wells throughout northeastern Ohio. Be described the Bols Blanc (p. 15) as "brown to broNnish-gray somewhat sandy finely crystalline dolomite containing 40 to 75 percent of white chalky dolcmoldic chert and bluish-grey chert,” Dow noted that the quartz sand is most abundant everywhere in the basal few feet of the Bois Blanc. Jh the Erle-Ciyahogar-Yfeyne counties region Dow (1961, p. 14) found that the Bois Blanc could be easily differentiated from the overlying Columbus by its "dolcmltic character, darker coles*, and such higier proportion of cherty residues." To the east, however, he found that the Bois Blanc became more calcareous and the Columbus mare cherty, so that the contact of the two units was very difficult to precisely place. Because the chert in the Colunbus tended to be darker than the chert in the Bois Blanc, however, he consistently placed the contact at a "rather definite chert break" (p. 15)* Newman and 243

Vbodhams (1954), Stauffer (1944), and Janssens (1970b) placed the Bols Blanc-Coluribus contact In cares from northeastern Ohio at the base of a "coral biostrcme" Interval which Is apparently not every­ where present or Is not easily recognlzeable in well samples such as were studied by Dow* The Bois Bleno-Colusbus contact was stated to be a "regional unconformity" by Janssens (1968, p. 9). Regional straligraphic relations suggest that the Bols Blanc of the Ohio subsurface correlates only with Conkln and Oomdn's (1973) lower probably Bmsian unit of the "type" Bois Blsnc in northern Michigan*

COLUMBUS LIMESTONE

Overlying the Bois Blanc in the northeastern Ohio subsurface is a 120-190 ft thick predominantly limestone interval assigned by Dow (1961) entirely to the Oolunfcus Limestone everywhere except just east of the outcrop belt in Erie County, where he assigned the lower 65-70 ft to the "Detroit River*" This "Detroit River" interval was described by Dow (p. 20) as "brown to grayish brown finely crystalline limestone, grading downward into brown finely crystalline doloraitlc limestone with 10 to 25 percent of white to grayish-white chalky chert." He also noted the presence of much quartz sand in the upper 10 ft* The over- lying Coluntous was described by Dow (p. 22-23) as "tan to buff finely exystalllne limestone containing a little gray to white chalky chert." Hie Oolwbus further east in the Ohio subsurface was found by Dow (p. 27) to be "brown to brownish gray limestone containing 30 to 75 percent dark chert." 244

Janssens (1970a, p. 25) recorded 158 ft of Columbus In a core from Lorain County which he described as "fine to coarse grained fosslliferous light-yellcwish brown to medium brown limestone with nodular fbasilifterous white chert." The lower 34 ft was called a "coral bloat rctne." Janssens (1968) noted the presence of a 3-10 ft thick very sandy Interval In the Columbus approximately 60-70 ft above Its base In numerous cores and wells In Erie and Lorain counties. Stauffer (1944) also found that the lower part of the Colwbus was very sandy In a core from near Barberton, Summit Couity.

DELAWARE LIMESTONE

Tie Columbus Limestone just east of the outcrop belt In Erie, Lorain, and Ashland counties in northeastern Ohio Is overlain by approximately 30 ft of "argillaceous gray to brownish-gray limestone containing 15 to 25 percent brownish-black; or mottled blue-gray and brown chert" (Dow, 1961, p. 26). Dow (1961) assigned this interval to the Delaware Limestone and observed that it was "easily distinguished In these counties from the underlying Columbus by its darker color, the presence of brownish-black or mottled blue-gray and brown chert, and a much higher proportion of insoluble material." Janssens

(1963, p. 11) also noted that the Columbus-Dalaware contact was "dis­ tinct" and marked In the Erle-Lorain County area by the change from fine- to coarse-grained yellowish-gray limestone to fine-grained ll^it-brownlsh-gray limestone." Dow (1961) found that the Delaware became leas argillaceous and contained lighter colored chert east of Lorain and Ashland counties so that It could net be differentiated from the Colunbus in wells, Stuafffer (1944) reported only 5 ft of Delaware between the Coiunbus limestone and the Devonian shales In a core from near Barberton, Sunrait County, which was separated from the Coiunbus by a thin pyrltlc shale bed. Since Barberton Is over 50 miles southeast of any well In which the Delaware was definitely differentiated fron the Columbus by Dow (1961), It may be that the Pelaware thins to the southeast in the subsurface as a result of pre-Devonian shale erosion, lhat this nay be the case Is further suggested by Joissens' (1969, p. 1-21) observation that the Delaware pinches out to the east of the south-central outcrop area so that in southeastern licking County, approximately 30 miles east of Columbus, the Devonian shales directly overlie the Columbus.

STRAT1GRAPHIC ANALYSIS

Since Kerr (1950) assisted the entire 150 ft thick pre-Columbus Devonian. Interval at locality MH in Ottawa County to the Detroit River Dow (1961) believed that the Bois Blanc was either never deposited or was removed by erosion in the central Ohio outcrop belt area, even though he recorded 60 ft of Bols Blanc beneath the sandy "Detroit River" Interval In a well In Brie County only 10 miles southeast of locality MH. Unit I In north-central Ohio (which coincided with Kerr’s (1950) "Amhertsburg" at locality MH), however, Is similar in 2U6 thickness and litholcgy to the Bols Blanc and Is also overlain by a very sandy interval (fades 11:3) so that this author believes that the Bols BQLanc coincides with unit I throughout oentral Ohio* and hence that only the 50 ft thick fades 11:3 Interval (Kerr's (1950) "Lucas”) at locality MH represents the "Detroit River." Since unit I thins markedly from north to south In the central outcrop belt the southward thlrnlng of the "Onandoga" in the subsurface nay thus be ■ . ' N- due largely to southward thlmlng of the Bols Blanc. The Colunbus of the subsurface probably closely corresponds to the unit U - m i t IV Interval of oentral Ohio* althougi the available well and core descriptions do not permit precise location of the Inter- unit contacts in the subsurface. The unit H-usit H I contact In the » ■ • t subsurface* however* probably approximately coincides with the upper limit of abundant quartz sand in the Colunbus* approximately 60-70 ft above the B d s Blane-Columbus contact in most places (Janssens* 1968). The apparent eastward transition of the sandy init II Interval (Dow's (1961) "Detroit River") into a "coral biostrome" In the eastern Erie County area (Janssens* 1970a) suggests that during the time of unit

II deposition water agitation and probably depth Increased toward the east. This "coral biostrome" area nay have been continuous with the area of prolific coral and stromatqporoid growth in south-central Ohio represented by fades 1:1 (Stauffer's (1909) zone C) as was suggested by Janssens (1970b* p. 28), The very fosslllferous limestones and cherty less fosslUferous limestones of the Colunbus Interval in the subsurface which probably 2H7 correlates with the unit H l - m i t IV Interval In oentral Ohio probably represents deposition wider moderately agitated near wave* base to lew energy below wave-base conditions, the former prevailing In the western part of the subsurface area and the latter In the eastern part* sinna charophyte oogonia, which are restricted to fosslllferous packs tones and gralnstones In unit H I In oentral Ohio, were Observed by the author in thin sections Cram a care penetrating the upper part of the Colunbus near Barberton, Summit County, it Is suggested that these small calcareous algal (?) bodies may provide a means of approximately locating the unit III Interval In at least the western part of the subsurface area* The Delaware of the subsurface almost certainly correlates with w i t V of central Chlo, the thin pyritic shale bed noted by Stauffer (1944) at the Colurabus-Delaware contact In an wdergromd mine at Bsrberton, Sunmlt County, possibly representing a submarine expression of the discontinuity surface which marks the w i t IV-V contact in central Ohio* Like the Columbus of the eastern_part of the Chlo subsurface the Delaware of the subsurface probably also records a low-energy probably belcw wave environment* CHAPTER 10

SUMMARY OF EEPOSITIONAL ENVIRONMENTS

Cv Detailed study of the Devonian carbonate sequanoe In Ohio has revealed a diversity of distinct Uthofbcles within Individual stratig- raphlc units. These fades are believed to represent local variations In such Intimately Interrelated factors as water depth, water agitation and circulation, topography and paleogaography, deposltlonal slope, and the rates of transgression and regression, These numerous distinct lithof&cles can be grouped, however, into four basic recurring associ­ ations of rock types, biota, and sedimentary structures, each of which probably represents similar sedimentologLc and ecologic responses of sediments and organisms to analogous environmental conditions. Most of these basic facies ©xjwps are represented within each presumably correlative Interval of the sequence, and with the same lateral (geographic) relationships to one another in each such interval,. suggesting that during each major phase of Devonian carbonate deposition in Ohio the sea was differentiated into four distinct, but gradational shallow marine environments. In accordance with theoretical models of nclear water** sedimentation In epeirlc sea presented by Shaw (1963) and Irwin (1965) It is believed that this regional environmental differentiation resulted from largely depth controlled variations m

248 water circulation across the shallow sea* Figure 84 shows the infer­ red relationships of each of the basic depositcnal environments to one another and to relative depth. The facies represented by each of these depositlonal environments are also listed on Figure 84. This diagram Is highly idealized and In reality the areal distribution of the basic depositlonal environments was probably somewhat less controlled by relative depth and relative wave-base than Is Indicated* To generalize and sisplliy discussion of these depositlonal environ­ ments 9 however It si convenient to refer to such a relative depth- wave-base framework. The restricted above wave-base environment prevailed in the shallowest portion of the sea, far beyond the reach of open marine waves and currents and where the major movement of water was by wind-generated waves and possibly by density currents generated as a result of sharp salinity gradients. Topographic irregularities resulted in this shallow generally low energy area of the sea being differentiated Into a ccnplex mosaic of subenvironments ranging from periodically emergent algal mat covered flats and "ponded" areas where gypsum-crystal bearing laminated muds accumulated to slightly deeper, less frequently emergent areas where hittssinous banded muds and slightly fossilifterous muds containing the Detroit River fauna accumulated. Many of the features that are characteristic of modem supratidal environments were produced In the periodically emergent areas. Most of the sediment which accumulated in these various sub- envircnments was probably carbonate mud precipitated directly from SEMI-RESTRICTED AGITATED NEAR- LOW ENERGY BELOW RESTRICTED ABOVE WAVE-I3ASE ABOVE WAVE BASE ABOVE WAVE-BASE ZONE ZONE ZONE WAVE-BASE ZONE 1 Shoreward limit 1 of open marine The strand 1 1 energy effects 1 / | ^Mean sea level A ^Mean Wave-base

5 E D I Laminated muds and Burrowed muds- Skeletal sands Fossil 1ferous muds M intraclasti c and coral- £ calcarenites stromatoporoid ? biostromes - 11:3 I _ 11:1 1:3 I:2(?) - Lucas-Anderdon I - 11:2 Ilia 111:1 F interval of the I „ A 111:3 111:5 IV: 1 C Detroct River I - 111:4- IV :0, V:2 I do!omi te E Lower Dundee V: 1 V ; 3 S - Li t h o g r a p h i c Dundee^ V;5 V ;4 V:6 I Upper Dundee

Figure 84: Highly idealized- cross section of epeiric sea in Middle Devonian time in Ohio showing distribution of basic depositicnal environments in accordance with Shaw-Irwin model of epeiric sedimentation and observations made in this study. 250 251 the warm and relatively higily saline sea water. During storms, however, areas of the substrate which were lithlHed or semt-lithified were eroded, producing Intraclats which were In some cases Intensely abraded by the storm-generated waves and currents and xedeposlted to form cross-stratified pelletoidal and intraclastic calcarenites and caldrudltes. As a result of such storm activity and frequent lateral migration of the subenvironments in response to sea level fluctuations the deposlticnal record ofthe restricted above wave-base environment is characterized by frequent abrupt lateral and vertical UthologLc changes. The 3emi-P8atricted above wave-base environment represents that permanently submerged, low to moderate energy area of the sea between the restricted above wave-base environment and the area of maximum open marine wave and current energy. This probably lagoonal-llloe area was a locus of carbonate mud deposition, much of which was probably precipitated directly from sea water, although same of the sediment may have consisted of fecal pellets produced by soft-bodied burrowing organisms. 3h the best circulated parts of this environment normal marine skeletal-bearing organisms flourished, especially corals and 3tromatcporoids, which accumulated in biostrcmal-like deposits where the rate of carbonate mud deposition was lew. Occasionally storm waves disturbed the substrate, producing mucKUmp intraclasts where it was semi-lithifted and fragmented coral and strcraatcporold debris where it was "carpeted11 by these organisms. During some storms fragmented skeletal debris was also swept into the semi-restricted 252' environment from the adjacent agitated open marine environment re­ sulting In thin coqulnar-llke accumulations In the muddy sediment. The agitated near-above wave-base environment prevailed In the area where open marine waves and currents inpinged on the sea floar and had their energy dlssapated by friction. This hlgily agitated and nutrient area was populated by a diverse and abundant normal marine fauna dominated by crlncids, brachiopoda, and bryozoans. Hie abundant skeletal debris produced by these organisms was subjected In varying degrees of physical and/or biogenic reworking resulting In sediments which ranged Aram cross-stratified and abraded mud-free skeletal sands to fragnented, but not abraded muddy bloturbated skeletal sands. Hie low energy below wave-base environment prevailed in the deepest part of the sea where only the deepest storm waves were able to disturb the substrate. 3h this area much of the finely comminuted skeletal debris produced by physical and biogenic processes in the adjacent near-above wave-base agitated environment was deposited. Tn the shallowest and/or best circulated parts o f this environment a moderately diverse and normal marine fauna flourished, the skeletal remains of which accumulated easentalUy in situ and with minimal physical or biogenic reworking In the muddy skeletal caldsUtite substrate. 3h deeper and/or lees well circulated below nave base areas most of the noxmal marine organisms were Inhibited and unfossiliflerous wnriw accumulated which In some Instances contained considerable quantities of fine terrigenous materials derived from source areas far to the east. 253

Figure 85 shows the areal and stratigrephlc distribution of the facies group* believed to represent each of these basic depositlonal environments In the north-south trending central Ohio Devonian outcrop belt. Similarly, Figure 86 shows the distribution of these facies groups (Inferred far the eroded Findlay Arch area) In a restored east- west cross section of the Devonian carbonate sequence across northern Ohio. Comparison of these diagrams reveals that throughout Einsian- Elffeltan time the facies differentiation In the shallow sea was generally much greater from east to west than from north to south. Thus, the central outcrop belt area was probably more nearly parallel than perpendicular to the depositlonal strike of the sea throughout Ekisian-Eifelian time. Rjrtherraore, the distribution of the facies grotps In the east-west cross section suggests that throughout this time the general paleoslope In northern Ohio was from west to east, with north­ western Ohio probably having been an emergent sand covered area during the time of Bols Blanc (unit X) and unit IX deposition, a shallow restricted above wave-base area during the time of Columbus (unit XXX and IV) deposition, and a restricted to agitated above wave-base area during the time of Delaware (mit V) deposition In central and eastern Ohio. This Is consistent with the proposals by Droste, Shaver, end Lazor (1975), that during Kiddle Devonian time a "broad shallow water shelf" cn which "carbonate flat" sediments accumulated "occupies nearly all but the southwest part of Indiana and extended at least as for as central Ohio," and that during later Middle Devonian time this "Wabash Platform effectively was narrowed." The southward thinning of unit X 254

figure 85 : Cross section showing idistribution of facies groups in the Devonian carbonate sequence of central Ohio. !--- ytflTjl '/Ml::I *' *' SILURIAN Marion RESTRICTED-ABOVE WAVE-BASE DEPOSITS SEMI-RESTRICTED ABOVE WAVE-BASE DEPOSITS LOW ENERGY BELOW WAVE-BASEAGITATEDDEPOSITS ABOVE WAVE-BASE DEPOSITS Franklin DEVONIAN SHALE HORIZONTAL SCALE-MILES VERTICAL r40 SCALE-FEET

figure 85 256

figure 86: Restored East-Vfest cross section of the Devonian carbonate sequence in northern Ohio showing relations of stratigraphic units and inferred distribution of facies groups. w Lucas Co, Erie Co. Cuyahoga Co. FINDLAY ARCH Traverse Gp . v •ERODED

DUNDEE

s s S DETROIT RIVER

DOLOMITE

M a s

Sylvani a Sandstone

SILURIAN ORISKANY LOW ENERGY BELOW WAVE-BASE DEPOSITS SANDSTONE nr-j-ff AGITATED ABOVE WAVE-BASE DEPOSITS - 50 r~ SEMI-RESTRICTED ABOVE WAVE-BASE DEPOSITS

- 0 RESTRICTED ABOVE WAVE-BASE DEPOSITS * SCALE-FEET

Figure 86 258

In central (Mo, which is almost certainly at least In part depositlonal, also sug&sts that the Bnsian-Eifislian seas in Ohio may also have shallowed to the south. CHAFER XI

SUMMARY QF REGIONAL EEPOSITIONAL HISTORY

In latest early Devonian (Emsian) time the sea transgressed westward out of the Appalachian Basin over the karstic basal Kaskaskia erosion surface, Initiating unit I (Bois Blanc) deposition throughout all but westernmost Ohio, which remained an emergent area covered with a veneer of aeolian sand. Unis transgression was so rapid that the paleosols and aeolian sands which covered the basal Kaskaskia surface in the inundated areas were not preserved beneath a record of low energy nearshore muddy sediments, but were instead reworked in the agitated neareabove wave-base zone of the transgressing sea, resulting

In the basal sandy and conglomeratic zone of unit I. As the transgression continued most of central and eastern Ohio was inundated to below wave base depths and the thick record of relatively non-sandy sparsely fossiiiferous muds represented by facies 1:2 began to accumulate. The absence of record of unit I deposition in the outlier or northwestern

Chio suggests, however, that the unit I sea must have shallowed’rather rapidly to the west of the central outcrop area. Similarly, the. relative thinness and heterogeneous character of unit I in the southern, part of the central outcrop belt suggests that this was a shallower area where unit I deposition may have begun somewhat later and was 259 ' 260

probably much less continuous than to the north and east. However,

some of the southward thinning of unit I, and perhaps also the

absence of unit I in the outlier, may be due to erosion following

eastward regression of the sea and emergence which is believed to have

terminated unit I deposition.

Following this post-unit I period of emergence and possible

erosion the sea again spread westward, either in latest Emsian or

earliest Eifelain time, initiating unit II deposition in central Ohio.

The inferred distribution of the generalized depositlonal environments

iirmediately following this unit II transgression, as well as during

several subsequent periods of Eifellan time, are shown on Figure 87.

During unit II time the aeolian sand covered area in northwestern Chio

remained emergent and was the probable source of the sand which was

periodically introduced into the restricted above wave-base environ­

ment (represented by facies 11:3)* which at this time prevailed in most

of north-central and probably also west-central.Ohio. Southeast of

this area of restricted circulation the semi-restricted, above wave- base environment was established following the unit II transgression.

In portions of this semi-restricted environment where the' circulation was fairly good and the rate of carbonate mud accumulation low corals

and stromatoporoids flourished, resulting in the biostromal-like facies

11:1. The agitated near-above wave-base and low energy below wave- base environments probably prevailed in southeastern Chio during unit II time, the former being represented by the fo'ssiliferous packstones and grainstones which occur in facies 1:1 in Franklin County, and the latter

4 261

Figure 87: Inferred distribution of major depositlonal environments in Ohio at various times ..during the deposition of the Lower-Middle Devonian carbonate sequence. Tv \J \ SOURCES CLASTIC EARLY UNIT V SEMI-RESTRICTED ABOVE WAVE-BASE ZONE RESTRICTED ABOVE WAVE-BASE ZONE EMERGENT AGITATED NEAR-ABOVE WAVE-BASE ZONE L0W ENERGY BELOW WAVE BASE ZONE $ COLUMBUS - I - I - 3 [ 2 2 3 EARLY UNIT III MID-UNIT III lip** V» lip** \ SOURCES CLASTIC UNIT II MID-UNIT V

Figure 87 263 probably being represented by the argillaceous and cherty mudstones of the "Qnandoga" in the Ohio-West Virginia border area.

Deposition of unit II in central Chio was terminated by a very abrupt and sharp sea level rise which was followed by a brief period of non-deposition and submarine erosion prior to re-establishment of equilibrium conditions and initiation of deposition of the basal unit III facies. These facies represent environments ranging from semi-restricted and agitated above-near wave-base in the north (repre­ sented by facies III:3* ^ and 111:2 respectively) to low energy belcw wave-base in the south (represented by facies 111:1). Ihis sharp rise in sea level also resulted in inundation of the area of aeolian

Sylvania sand accumulation in northwestern Chio, initiating deposition of the upper marine part of the Sylvania and in a semi-restricted, but moderately agitated shallow area of the sea. It had relatively little effect in most of the eastern Chio subsurface area, however, where deposition of low energy below wave-base muds probably continued uninterrupted from unit II to.unit III time.'

Mid-unit III time was characterized by regional shallowing which resulted in the establishment of the restricted above wave-base environment represented by the ’’Lucas" and "Anderdon" portions of the

"Deuroit Fiver dolomite" in northwestern Chio. During the peak of the mid-unit III regression the semi-restrlcted above wave-base environment extended as far southeast as northern Delaware County In central Chio and It is probable that the restricted above wave-base area in northwestern Chio may have become emergent and subjected to intense ground-water solution. In later unit III time sea level again rose and the- restricted above wave-base environment was reestablished in northwestern Ohio while most of central Chio became an area of agLtated near-above wave-base deposition (facies 111:5). An abrupt fall of sea level terminated unit III deposition and resulted in central

Chio becoming a near mean sea level "starved" area where there was little or no sediment accumulation and where the substrate was lithified and intensely scoured. I is also very probable that-at this time northwestern Chio again became emergent. Deposition may have continued relatively uninterrupted from unit III to unit XV time in far south­ eastern Chio, however.

Deposition of unit IV in central Chio and the upper part of the

"Lucas"-"Anderdon" Interval in northwestern Chio was initiated when the sea again rapidly transgressed westward and equilibrium conditions were established throughout the entire area. The fact that most of unit IV in north-central Ohio consists of fossiliferous mudstones and wackestcnes interpreted as having been deposited in the low energy below wave-base environment suggests that mean , sea level may have been higher during unit IV time than unit III time. 'Unit IV deposition was, however, like unit III deposition terminated by an abrupt and sharp fall in sea level which caused emergence of northwestern Ohio and brought the central Chio area very close to mean sea level once again. During this low stand of sea level the northwestern Chio area was apparently subjected to rather intense erosion and the post-unit IV discontinuity surface formed in central Ohio. 265 / The hiatus which followed the deposition of unit IV in central

Chio and the ’’Detroit River dolomite" in northwestern Ohio was long enougi to permit the development of restricted Hamiltonian fossils, which first appear in the thin interval of facies V:1 packstone and grains tone over lyin g the post-unit IV discontinuity surface. The fact that facies V:1 is itself termihated by a prominent discontinuity surface in places suggests that it is an essentially independent wedge­ like unit which may have been deposited while northwestern Chio was still emergent, and hence that it was not related to the sudden and sharp rise in seal level believed to be responsible for initiation of deposition of the post-facies V:1 portion of unit V in central Chio

(Delaware limestone) and the Dundee Limestone of northwestern Ohio.

During very early Dundee-Delaware time areas of restricted and semi­ restricted above wave-base deposition, represented by the "lithographic

Dundee" and the "lower Dundee respectively, were established in north­ western Ohio, whereas the central Chib area was rather, rapidly inundated to below wave base and became an area of skeletal calcisiltite depo­ sition (facies V:2,. 3, and *0. This finely comminuted skeletal debris is believed to have been produced’in the' agitated near-above wave-base environment which was probably initially established in the now eroded axial region of the Findlay Arch. Not too long after initiation of

Dundee-Delaware deposition a layer of volcanic ash, probably the Tioga

Bentonite of the Appalachian Basin, was deposited throughout the northern

Mid-Continent region. This volcanic ash was apparently not preserved in northwestern Chio, but is probably represented by the thin brown 26 6

/ clay-shale bed near the base of unit V in central Ohio and the

outlier. As the Dundee-Delaware transgression continued the agitated

near-above wave-base environment migrated into northwestern Chio,

Initiating deposition of the skeletal sands of the "upper Dundee" in

this area while the rest of Chio probably remained a below wave-base

area of carbonate mud deposition. Considerable quantities of illite

and angular quartz silt also accumulated in parts of the below wave

base area, this terrigenous material probably being derived from

source areas in the present Appalachian region which developed between

the time of unit IV and unit V deposition. Somewhat later in unit V

(Delaware) time agitated near-above wave-base depositional conditions were at least briefly reestablished In central Ohio, as indicated by

the fossiliferous packstcnes and grainstones of facies V:5 and V:6 which abruptly overlie the argillaceous mudstones which form, the bulk

of the exposed portion of the unit. Because of the limitations of the exposures and. the probably intensive erosion which. followed Dundee-

Delaware deposition and preceded deposition of the Devonian shales in

central Ohio and the Traverse Group in northwestern Ohio the later

depositional history of the Emsian-Eifelian carbonate sequence in Ohio

is unknown. V

CHAPTER XII

CONCLUSIONS

The Lower-Middle Devonian carbonate sequence in central Ohio

consists of five major units which are separated from each other by

distinct surfaces which represent abrupt changes in depositional regimen

and/or prolonged periods of non-deposition and in some instances emergence. Each of these units consists of two or more generally

laterally extensive and laterally gradational facies which reflect

geographic and/or terrporal variations in environmental conditions, especially water agitation and circulation. Many of the vertical facies

contacts within units are quite sharp and discontinuity surfaces are present In some facies indicating that sudden changes in depositional

regimen were frequent.: The absence of "ideal" transgressive and regressive facies sequences also indicates that the relative sea level

changes responsible for the termination of deposition of one unit and

for initiation of deposition of the succeeding unit were very rapid.

Regional stratigraphic analysis indicates that the oldest unit . in the Devonian carbonate sequence of central Ohio (unit I) has no

correlative in either northwestern Ohio or the Logan County outlier.

It probably correlates with the Bois Blanc Formation of the eastern

Chio subsurface and south-central Michigan, however. Unit II also

26? probably predates any marine Devonian rocks in northwestern Ohio, however, in the outlier it coincides with the so-called "Detroit River."

Units III-V of central Ohio are represented both in the outlier and northwestern Ohio. In the outlier the unit III-V interval ("Columbus") * is thoroughly dolomitlzed, but the same sequence of facies represented in this interval near Marion in the central outcrop belt can be recog­ nized. Since the upper limit of abundant quartz sand in the Devonian carbonate sequence of central Chio (essentially the unit II-unit III contact) probably approximately correlates with the Sylvania-"Detroit

River dolomite" contact in northwestern Ohio and since biostratigraphic data indicates the correlation of the Dundee and the Delaware (unit V), it seems probable that units III and IV of central Ohio correlate with the "Detroit River dolomite" of northwestern Chio. Thus the silty-shale bed in unit III and the discontinuity surface terminating unit III in central Ohio may correspond to brecciated ground-water solution zones in the "Detroit River, dolomite."

The'numerous distinct lithofacies occurring In the outcropping

' • • • Devonian carbonates in Ohio can be grouped into, four suites, the facies included in each of these suites displaying a basic lithologic ani faunal similarity and probably representing equivalent sedimentologic and ecologic responses to somewhat analogous depositional conditions.

The major factors responsible for the differention of the sea into the four basic depositional environments represented by each of these four facies suites were probably water agitation and circulation, both of which may have been closely related to relative water depth. The distribution of the rocks representing each of these basic depositional

environments within each unconformity- or discontinuity bounded unit

Indicates that througiout the time of deposition of the Devonian

carbonate sequence the general paleoslope was towards the east. Thus,

the sharp vertical facies contacts within the sequence in the central

Ohio outcrop belt, which is rougnly parallel to depositional strike,

are probably roughly time equivalent. The areal and stratigraphic

distribution of the facies suites indicates that in spite of numerous regressions, the general tendency during the Middle Devonian was

for submergence of the craton in the northern. Mid-Continent region, with

the deeper water depositional environments becoming more dominant in

Chio with each succeeding phase of deposition. This progressive,

but discontinuous cratcnic submergence may have been the result of

cratonic downwarping due to increased orogenic activity in the

Appalachian region, the latter which is first reflected in the sedemen-

tary record by the abundant fine terrigenous material in the

Delaware limestone (unit V). I

APPENDIX A

LOCATIONS OP MEASURED SECTIONS

Sections in Central Chio

HM Hal-Mar Stone Company Quarry, just south of Deer Creek 4 miles northwest of Williamsport, Pickaway County (Clarksburg Quad.).

AA American Aggregates Company Quarry along the west bank of the Scioto River 4.5 miles south of Columbus, Franklin County (Southwest Columbus Quad.).

WJ Madison Stone Company Quarry just east of little Darby Creek 2 miles south of West Jefferson, Madison County (West Jefferson Quad.).

MCT Abandoned Quarry bounded by Trabue Rd. and McKinley Ave. 1 mile west of Marble Cliff, Franklin County (Southwest Columbus Quad.).

MCS Marble Cliff Industries Quarry between the Scioto River and Dublin Rd. 2 miles northwest of Marble Cliff, Franklin County (Northwest Columbus Quad.).

HR Exposures along Hayden Run 2 miles south.of Dublin, Franklin County (Northwest Columbus Quad.).

SN Abandoned "Snouffer's" Quarry along the east bank of the Scioto River 1 mile south of Dublin, Franklin County (Northwest Columbus Quad.).

BR Exposures along Bartholemew Run 1 mile southeast of Powell, Delaware County (Powell Quad.).

M Abandoned "Miami" Quarry 2 miles northeast of Powell, Delaware County (Powell Quad.).

U Union Quarry 2 miles east of Watkins, Union County (Shawnee-Hills Quad.).

270 Sections in Central Chio, continued. MCK Exposures along the north bank of Mill Creek 1 mile west of Bellepoint, Delaware County (Shawnee Hills Quad.). K National lime and Stone Company Quarry at Klondike, 2 miles north of Bellepoint, Delaware County (Ostrander Quad.).

0 Owens Stone Company Quarry 0.5 miles west of Warrensburg, Delaware County (Ostrander Quad.).

D Abandoned quarries east and west of the Chesapeake and Chio * Railroad where it intersects Delaware Run in the western part of Delaware, Delaware County (Delaware Quad.).

PY Pen-Ry Stone Company Quarry 1,5 miles south of Radnor, Delaware County (Ostrander Quad.).

OW Abandoned Quarry 0.5 miles east of Owens, Marion County (Marian West Quad.).

JE Abandoned John Evan’s Quarry just northwest of Marion, Marion County (Marion West Quad.).

H J. M. Hamilton and Sons Quarry 1.25 miles northeast of Marian, Marion County (Marion East Quad, and Marion Vfest Quad.).

T National lime and Stone Company Quarry 3.5 miles northeast of Mhrion, Marion County (Mannet Quad.).

S National lime and Stone Company Quarry at Spore, 6 -miles north­ west "of Bucyrus, Crawford County (Oceola Quad.).

B France Stone .Company Quarry 1.5 miles east of Bloomville, Seneca County (Attica Quad.).

FR France Stone Company Quarry. 1 mile west of Elatrock, northeastern Seneca County (Fireside Quad.).

BE France Stone Company Quarry 0.5 miles west of Bellevue, Sandusky Quadrangle (Bellevue Quad.).

PK Sandusky Crushed Stone Company Quarry at Parkertown, Erie County (Bellevue Quad.).

C ' Abandoned Quarry owned by Wagner Quarries Company 1.5 miles southwest of Castalia, Erie County along State Route 101 (Castalia Quad.).

V Abandoned Quarry 1.7 miles south of Venice, Erie County just north of State Route 101 (Castalia Quad.). 272 Sections in Central Chio, continued.

SD Wagner Quarries Company Quarry 2 miles south of Sandusky, Erie County across from the Soldier’s Home (Sandusky Quad.).

MH Standard Slag Company Quarry 0.5 miles southwest of Marblehead, Ottawa County (Gypsum Quad.).

KI lakeside exposures and abandoned quarries on Kellys Island, Erie County (Kellys Island Quad.).

Sections in the Outlier

CB Exposures along a small creek a mile southwest of the village of Cable, 10 miles northeast of.- bbana, Champaign County (Kingscreek Quad.).

PT Abandoned Piatt Quarry 2 miles east of West Liberty, Logan County (Kingsereek Quad.).

EL East liberty Stone Company Quarry 1 mile west of East liberty, Logan County (East liberty Quad.).

EF Abandoned Quarry just west of Belle font aine, Logan County (Bellefontaine Quad.).

CR Exposures alopg Cherokee Run 4.5 miles north of Bellefontaine, Logan County (Huntsville Quad.).

BS Abandoned Quarry 0.3 miles north of Big Springs, Logan County (Rushsylvania Quad.).

Sections in Northwestern Chio

SL France Stone. Company Quarry at Silica, Lucas County (Sylvania Quad.).

PG Pugh Quarry, 5.2 miles west of Weston and 5 miles south of I'fcClure, Wood County (McClure Quad.). LIST OF REFERENCES ■

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