Pinnacle Reef Complex - Ray Reef, Macomb County, Michigan

Western Michigan University ScholarWorks at WMU

Master's Theses Graduate College

12-2012

Faunal Distribution and Relative Abundance in a Silurian (Wenlock) Pinnacle Reef Complex - Ray Reef, Macomb County, Michigan

Jennifer L. Trout

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Recommended Citation Trout, Jennifer L., "Faunal Distribution and Relative Abundance in a Silurian (Wenlock) Pinnacle Reef Complex - Ray Reef, Macomb County, Michigan" (2012). Master's Theses. 110. https://scholarworks.wmich.edu/masters_theses/110

This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. FAUNAL DISTRIBUTION AND RELATIVE ABUNDANCE IN A SILURIAN (WENLOCK) PINNACLE REEF COMPLEX - RAY REEF, MACOMB COUNTY, MICHIGAN

Jennifer L. Trout, M.S.

Western Michigan University, 2012

Niagaran (Silurian) reefs are important sources of hydrocarbons in the Michigan Basin. In addition, some of these reservoirs have been used for gas storage

and may be potential CO2 sequestration sites. Despite extensive research on Niagaran reefs, most studies concerning faunal abundance and distribution have been qualitative studies conducted by paleontologists with an emphasis on taxonomy, paleoecology, and evolution. This study is the first quantitative study of relative abundance and general distribution of fauna throughout a single Wenlock reef located in the southern trend of the Michigan Basin. This study will build on previous work done by WMU students and will utilize their data (e.g. core descriptions, facies analyses, whole core analyses and sequence stratigraphic boundaries) to evaluate the distribution of fauna in Niagaran reefs in the Michigan Basin. The purpose of this study is threefold: 1) to quantitatively determine faunal abundance from subsurface cores of Ray Reef, 2) to determine if the faunal abundance is variable or consistent on windward vs. leeward margins vs. the crest of the reef, and 3) to analyze porosity/permeability data in conjunction with faunal abundance. These objectives will be met using a combination of core descriptions and image analysis of core slabs to capture quantitative variations in the distribution of reef organisms. This data may provide further insight into Niagaran pinnacle reef complex growth and development as well as faunal influence on reservoir characteristics. FAUNAL DISTRIBTUION AND RELATIVE ABUNDANCE IN A SILURIAN (WENLOCK) PINNACLE REEF COMPLEX - RAY REEF, MACOMB COUNTY, MICHIGAN

Jennifer L. Trout

A Thesis Submitted to the Faculty of The Graduate College in partial fulfillment of the requirements for the Degree of Master of Science Department of Geosciences Advisor: G. Michael Grammer, Ph.D.

Western Michigan University Kalamazoo, Michigan December 2012

ACKNOWLEDGMENTS

The completion of this thesis would not have been possible without the support and encouragement of many people. Foremost among them is my advisor, Dr. G. Michael Grammer, whose knowledge, advice, and support guided me through this process. Dr. Grammer’s unique teaching/mentoring style and vision led me from undergraduate work to this thesis and prepared me for future work. For this, I am very grateful and appreciative. I would also like to thank my committee members Dr. William Harrison III and Dr. Robb Gillespie for providing valuable feedback, guidance, and support. I would like to thank the Department of Geosciences, the Michigan Geological Repository for Research and Education, and the Michigan Basin Geological Society for financial support. I truly appreciate the help I received from the administrative staff, especially Kathy Wright and Linda Harrison. Without the support of my fellow students (especially Shawn McCloskey, Marcel Robinson, Pete Feutz, Seth Workman, and Jason Asmus) I would not have made it through the program and am grateful for their patience, advice, and friendship. I would like to express my deepest gratitude for the never ending support and encouragement of my sister Amanda Trout and my friends Carla Chase and Michele Anderson, without whom I would have never had a chance. I dedicate this work to the memory of my father and mother, Gordon W. and Patricia A. Trout, who instilled in me the value of knowledge, work, and love.

Acknowledgments - Continued

Jennifer L. Trout

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TABLE OF CONTENTS

ACKNOWLEDGMENTS ...... ii

LIST OF TABLES ...... x

LIST OF FIGURES ...... xi

CHAPTER I: INTRODUCTION ...... 1

First Objective: Relative Abundance and General Distribution of Fauna on a Single Reef Complex in the Southern Pinnacle Reef Belt of the Michigan Basin ... 1

Second Objective: Influence of Wind/Current on Morphology and General Distribution of Fauna (Reef Zonation) ...... 2

Third Objective: Influence of Wind/Current on Cementation ...... 4

CHAPTER II: GEOLOGIC SETTING ...... 6

Regional Geologic Setting ...... 6

Regional Stratigraphy ...... 9

Changes in Sea Level and Climate During the Silurian ...... 11

Wind Direction on Reefs in the Michigan Basin During the Silurian ...... 14

Sequence Stratigraphy Boundaries ...... 19

CHAPTER III: PREVIOUS WORK ...... 21

General Overview of Michigan Basin Studies of the Silurian ...... 21

Ancient Analogs ...... 23

Qualitative Studies of Faunal Relative Abundance and Distribution Outside of the Michigan Basin and During Other Time Intervals ...... 23

Table of Contents - Continued

Hydraulic Energy and Reef Framebuilding Morphology ...... 23

Water Depth and Reef Zonation in Western Canadian Devonian Reef Complexes...... 26

Hydraulic Energy, Faunal Morphology and Zonation, and Early Submarine Cementation in a Middle to Upper Devonian Iberg Reef, Germany ...... 27

Previous Qualitative Studies of Michigan Basin Silurian Reef Faunal Relative Abundance and General Distribution...... 29

Previous Quantitative Studies of Relative Abundance and General Distribution of Fauna ...... 29

Thornton Reef Complex (Thornton, Illinois) ...... 30

Southeastern Wisconsin Quarries ...... 31

Michigan Basin Southern Pinnacle Reef Belt (Macomb County, Michigan) ..... 33

Reed North Quarry (Fairborn, Ohio) ...... 33

Previous Studies of Michigan Basin Pinnacle Reefs Using Sequence Stratigraphy ...... 34

Ray Reef...... 34

A Study Comparing Silurian Pinnacle Reefs from the Northern and Southern Trends ...... 35

Modern Analogs ...... 35

CHAPTER IV: MATERIALS AND METHODS ...... 36

Materials ...... 36

Methods...... 38 v

Table of Contents - Continued

Framework Density ...... 38

Diversity ...... 39

Distribution and Composition of Reef-Building Assemblages ...... 40

Description of Various Quantitative Methods Used in Modern Reef Ecology Studies ...... 40

Quantitative Methods Used in Paleoecology Studies of Fossil Reefs ...... 42

Skeletal Mineralogy and Diagenesis ...... 44

Cements...... 48

Reservoir Characteristics ...... 60

Evaluation of Porosity...... 60

Procedure ...... 60

Limitations of this Study ...... 63

Dolomitization ...... 63

Limitations with Core Data ...... 63

Limitations of Analogs ...... 64

CHAPTER V: RESULTS AND DISCUSSION ...... 66

Relative Abundance ...... 68

Framework Density ...... 69

Diversity ...... 73

Table of Contents - Continued

Distribution and Composition of Reef-Building Assemblages ...... 75

Distribution and Community Replacement vs. Succession ...... 76

Community Replacement ...... 78

Cementation ...... 80

Comparisons with Ancient Analogs ...... 80

Modern Analog – Tongue of the Ocean (TOTO), Bahamas ...... 83

Similarities between TOTO, Bahamas and the Silurian Michigan Basin Reefs and Margins ...... 83

Reservoir Characteristics ...... 84

Analysis of Core Up to Sequence Boundary 2 (SB2) ...... 89

Analysis of Core from Sequence Boundary 2 (SB2) to Sequence Boundary 3 (SB3) ...... 93

Analysis of Core Above Sequence Boundary 3 (SB3) or between SB3 and Sequence Boundary 4 (SB4) ...... 101

CHAPTER VI: POTENTIAL APPLICATIONS AND FUTURE WORK ...... 105

Potential Applications ...... 105

Future Work ...... 110

CHAPTER VII: CONCLUSIONS ...... 112

Major Findings ...... 112

Relative Abundance ...... 112

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Table of Contents - Continued

Framework Density ...... 113

Diversity ...... 113

Morphology...... 113

Faunal Distribution ...... 114

Cement ...... 114

In situ vs. Debris ...... 115

APPENDICES

A. HALMICH 2-1 (PN24763) RESULTS AND SUPPORTING TABLES AND FIGURES ...... 116

B. JACOB 1-36 (PN24987) RESULTS AND SUPPORTING TABLES AND FIGURES ...... 137

C. PERCY 2-2 (PN25100) RESULTS AND SUPPORTING TABLES AND FIGURES ...... 156

D. BUSCH-TUBBS-KUHLMAN 1-36 (PN25203) RESULTS AND SUPPORTING TABLES AND FIGURES ...... 167

E. LASKOWSKI 4-1 (PN25547) RESULTS AND SUPPORTING TABLES AND FIGURES ...... 186

F. LASKOWSKI 5-1 (PN25832) RESULTS AND SUPPORTING TABLES AND FIGURES ...... 202

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Table of Contents - Continued

G: WINDWARD VS LEEWARD EFFECTS ON FAUNAL DISTRIBUTION AND RESERVOIR CHARACTERISTICS: SIMILARITIES BETWEEN RAY REEF (SILURIAN) AND THE MARGIN AND FORESLOPE OF THE TONGUE OF THE OCEAN, BAHAMAS ...... 213

BIBLIOGRAPHY ...... 286

LIST OF TABLES

1: Well name, permit number, footages, and facies data for well cores from Ray Reef used in this study ...... 36

2: Mineralogies of major fauna ...... 47

3: Comparison of Cores in Ray Reef ...... 67

LIST OF FIGURES

1: Map of the Earth during the Middle Silurian (425 Ma) by Scotese at http://www.scotese.com/newpage2.htm ...... 7

2: Michigan Basin region showing basins, reef banks, pinnacle reef belts, domes, arches, and study locations discussed in text...... 8

3: Stratigraphic Nomenclature for Silurian strata in Michigan (Guelph Formation highlighted) and surrounding states (compiled from Catacosinos et al., 2000; Shaver, 1991; Simo and Lehman, 2000) ...... 10

4: Global sea level curves determined using sequence stratigraphy (Haq & Schutter, 2008) and generalized graptolite zones (Johnson, 2010)...... 13

5: Paleogeographic reconstruction of Laurentia and the epicontinental and epeiric seas during the Silurian (430 Ma) with the location of the Michigan Basin indicated by the box ...... 16

6: Structural contour model of Ray Reef showing distinction between windward and leeward margins in aerial and profile views (Wold, 2008) ...... 17

7: A) Cross section from B to B’ (south/windward to north/leeward) across Ray Reef. B) Cross-section of Ray Reef showing the relationship between primary depositional facies and porosity and permeability values with B’ (north) to the right ...... 18

8: Model of zoned marginal reef showing morphologies of fauna relative to energy level and position on reef as well as lithologies and reef type: coral reef (mainly Cenozoic), stromatoporoid reef (mainly Siluro-Devonian) and stromatolite (mainly early Proterozoic) (redrafted from James and Bourque, 1992)...... 25

9: a) Inferred Devonian depth zones based on paleoecological comparisons with b) Holocene ecological zones (after Logan, 1969) ...... 27

10: Reconstruction of paleoecology of Devonian Iberg Reef, Germany, showing wind direction and faunal morphology...... 28

List of Figures - Continued

11: Ray Reef with the location of cores utilized in this study and the direction of inferred paleowind...... 37

12: Halmich 2-1 at 3027 feet showing the core and the piece cut for thin section analysis (Facies 4 Skeletal Grainstone)...... 48

13: Halmich 2-1 core at 3027 feet showing plane light (top) and cross-polarized light (bottom) thin sections of sub to euhedral replacement dolomite...... 49

14: Busch-Tubbs-Kuhlmann 1-36 at 3202 feet showing the core and the piece cut for thin section analysis (Facies 3A Stromatoporoid Wacke-Boundstone)...... 50

15: Bush-Tubbs-Kuhlmann 1-36 core at 3202 feet showing plane light (top) and cross-polarized light (bottom) thin sections of replacement dolomite...... 51

16: Busch-Tubbs-Kuhlmann 1-36 at 3047 feet showing the core and the piece cut for thin section analysis (Facies 3A Skeletal Wacke-Packstone)...... 52

17: Bush-Tubbs-Kuhlmann 1-36 core at 3047 feet showing plane light (top) and cross-polarized light (bottom) thin sections of coral with structure partially retained by subhedral to euhedral mimetic replacement dolomite...... 53

18: Busch-Tubbs-Kuhlmann 1-36 at 3049 feet showing the core and the piece cut for thin section analysis (Facies 3A Skeletal Wacke-Packstone)...... 54

19: Bush-Tubbs-Kuhlmann 1-36 core at 3049 feet showing tan areas in plane light (top) and cross-polarized light (bottom) thin sections of bladed or botryoidal fabric destructive marine cements...... 55

20: Busch-Tubbs-Kuhlmann 1-36 at 3057 feet showing the core and the piece cut for thin section analysis (Facies 3B Skeletal Wacke-Packstone)...... 56

21: Bush-Tubbs-Kuhlmann 1-36 core at 3057 feet showing dark brown area in plane light (top) and cross-polarized light (bottom) thin sections of replacement dolomite...... 57

xii

List of Figures - Continued

22: Halmich 2-1 at 2979 feet showing the core and the piece cut for thin section analysis (Facies 3A Stromatoporoid Wacke-Packstone)...... 58

23: Halmich 2-1 core at 2979 feet showing dark brown area in plane light (top) and cross-polarized light (bottom) thin sections of replacement dolomite...... 59

24: Color code for fossil identification in core slab images...... 62

25: Example of color-filled fossils on scanned .tiff image (left side) and Image- Pro Plus count of each fossil and corresponding percent of the slab occupied (right side)...... 62

26: Relative abundance of fauna across wells in Ray Reef ...... 69

27: Density of fauna across wells in Ray Reef. Density of fauna is the percentage of the core that is covered by each category of fauna when the total slabbed core surface equals one hundred percent ...... 73

28: Diversity by facies across wells in Ray Reef. Diversity is expressed as the number of phyla represented with a maximum of eight possible ...... 75

29: Busch-Tubbs-Kuhlmann (BTK) core showing average perimeter of fauna in millimeters (x-axis) with core depth in feet (y-axis)...... 79

30: Cross-plot of average values for permeability and porosity in the Reef Core Facies (3a) for five cores across Ray Reef ...... 85

31: Cross-plot of average values for permeability and porosity during the transgressive and regressive phases of the three 3rd order sequences across Ray Reef ...... 88

32: Facies, texture, faunal density, percentage of cement, percentage of porosity, and permeability (mD) below Sequence Boundary 2 for all six wells studied across Ray Reef ...... 92

xiii

List of Figures - Continued

33: Facies, texture, faunal density, percentage of cement, percentage of porosity, and permeability (mD) between Sequence Boundary 2 and Sequence Boundary 3 ...... 96

34: Core slab a) without pore space highlighted in black and b) same core slab showing enhanced porosity due to secondary dissolution of cements highlighted in black from a windward core (Laskowski 4) ...... 98

35: CT scanned cores comparing moldic and vuggy porosity that has (a) and has not (b) been enhanced due to secondary dissolution showing extent of permeability enhancement ...... 99

36: Facies, texture, faunal density, percentage of cement, percentage of porosity, and permeability (mD) between Sequence Boundary 3 and Sequence Boundary 4 ...... 104

37: From the conodont and graptolite zonations of Illinois (Ross and Ross, 1996) and the corresponding conodont and graptolite zonations of the correlated 13Ccarb curve (Cramer et al., 2011), it appears as though the three 3rd order sequence boundaries identified in Ray Reef by Wold (2008) occurred during the Mulde event ...... 108

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CHAPTER I: INTRODUCTION

The Mid-Silurian Wenlock series was the first of two significant global peaks in the earth’s reef building history (Copper, 2002). It was also one of the largest in areal and latitudinal extent, second only to the Eifelian-Givetian and Frasnian of the Devonian (Copper, 2002). Greenhouse conditions, sea level highstands, and the arrangement of tectonic plates in equatorial regions combined to create extensive shallow platforms and intracratonic basins conducive to reef growth (Copper, 2002). Some of the most studied and best examples of Wenlockian reefs are located in the Michigan Basin (Shaver, 1977). In the intracratonic Michigan Basin, Niagaran pinnacle reefs grew on the sloping edges of the margin, distal to a barrier reef complex which encircled the basin (Mesolella et al., 1974; Gill, 1977; Gardner and Bray, 1984). It has been proposed that these reefs were sourced with hydrocarbons by interbedded carbonates and subsequently sealed by evaporites in cyclic fashion as sea level and intracratonic basin conditions changed through Silurian time (Gardner and Bray, 1984). To date, these reefal reservoirs have produced more than 490 MMBO and 2.9 TCF of gas in the Michigan Basin (Grammer et al., 2010).

First Objective: Relative Abundance and General Distribution of Fauna on a Single Reef Complex in the Southern Pinnacle Reef Belt of the Michigan Basin

Due to their economic and stratigraphic significance, the literature concerning Silurian reefs is voluminous. However, most studies conducted in the Great Lakes area have been qualitative studies which have focused on taxonomic lists of species, reef community succession, timing of deposition, and diagenesis. The number of 1

studies that have focused on the relative abundance and general distribution of reef fauna are few (Balogh, 1981; Ingels, 1963; Lehmann and Simo, 1989; Schneider and Ausich, 2002; Watkins, 1993). There are no published quantitative studies on Silurian Reefs in the Michigan Basin pinnacle reef belts. Therefore, the primary goal of this study was to quantitatively analyze relative abundance (including framework density and diversity) and general distribution in a single Wenlock reef complex. The reef chosen for this study was Ray Reef which is located in Macomb County, Michigan, along the southern trend of pinnacle reefs. This reef was chosen because a previous study (Wold, 2008) had determined third order sequence stratigraphic boundaries that were correlated across the reef and used to create a 3-D model. These third order sequence boundaries were used in this study as time correlative surfaces for relative abundance and distribution calculations across the reef.

Second Objective: Influence of Wind/Current on Morphology and General Distribution of Fauna (Reef Zonation)

The control of wind and currents on reef zonation has been proposed since Darwin (1897). On modern reefs, studies have shown correlations between coral morphologies and current and wave energies. Most studies have shown that reefs are better developed on windward margins with coral shapes ranging from encrusting or robust in higher energy settings to delicately branching in lower energy leeward settings or deeper on the fore slope. Suggested reasons for more extensive reef growth on windward margins are food and nutrient replenishment, removal of fine clogging sediment, and moderation of temperature, salinity, and dissolved oxygen extremes (Wells, 1957). Studies concerning faunal distribution along modern windward and leeward reef margins have been conducted in the Caribbean (Geister,

1977; Gischler, 1994; Gischler and Lomando, 1999), Great Barrier Reef (Marshall and Davies, 1982; Hopley and Barnes, 1985; Hubbard, 1988), Grand Cayman (Blanchon and Jones, 1995), Hawaii (Grigg, 1998), Ryukyu Islands of Japan (Hongo and Kayanne, 2009; Yamano et al., 2003), and Caicos Platform (Rankey et al., 2009). Studies that are in disagreement with these general trends include a study in Hawaii which emphasizes that exceptionally large open-ocean swells may discourage reef development on windward sides except where they are shielded by adjacent islands or are isolated from the large swells in embayments (Grigg, 1998), and a study by Rankey et al. (2009) which suggests that it is an oversimplification to state that platform-scale facies patterns are controlled by windward/leeward influences (Rankey et al., 2009). Using an uniformitarian approach, some researchers have attempted to apply patterns of modern reef zonation, coral morphologies, and hydrodynamic regimes to ancient reef zonation and coral and stromatoporoid morphologies in order to interpret paleoenvironments (James, 1976, 1983; Kershaw, 1998). Studies using such analogies have been conducted on the following ancient reefs: the Pleistocene of Curacao, Netherlands Antilles (Pandolfi and Jackson, 2001; Pandolfi et al., 1999), the Devonian Iberg Reef in the Harz Mountains of Germany (Gischler, 1995), the Western Canadian Devonian reefs (Klovan, 1974), and middle to late Devonian reefs (Machel and Hunter, 1994). There have been no published quantitative studies on Wenlockian Reefs in the Michigan Basin pinnacle reef belts that have analyzed faunal distribution and morphology in relation to hydraulic regimes on a single reef complex (e.g. whether they are consistent or vary on leeward, crest, and windward sides of a reef). Therefore, the second purpose of this study was to determine if faunal morphology, 3

relative abundance, and general distribution on a single Wenlockian reef complex in the Michigan Basin pinnacle reef belt varied in response to hydraulic energy of the windward/leeward reef margins and reef crest.

Third Objective: Influence of Wind/Current on Cementation

James et al. (1976) found that the distribution of early submarine cementation on reefs was influenced by wind and currents. Studies by Marshall and Davies (1981) and Gischler (1995) showed that reefs exposed to higher water energy were better cemented than those exposed to low or medium water energies. Studies by Klovan (1974) and (Grammer 1993a, 1993b, 1999) have shown that windward margins experience rapid cementation with steeper margins and abrupt facies changes while leeward margins have more gently sloping sides with gradual facies changes over long distances. Although reservoir characterization is not part of this study, the role of early cementation is a critical element of primary and secondary porosity and permeability values in reservoirs. Because there is an established relationship between hydraulic energy, reef morphology, and early cementation, a secondary objective of this study was to record the estimated percentage of early marine cementation in the cores and the estimated percentage of core that is composed of in situ fossils compared to debris. This data may indicate areas for future research applicable to industry for reservoir characterization. These objectives were accomplished by using a modified continuous line intercept transect method for six subsurface cores from a single reef complex, Ray Reef, located along the southern trend of Niagaran reefs in the Michigan Basin. The six cores examined were located throughout the reef complex, e.g. two cores from the 4

reef crest, two cores from the windward side of the reef, and two cores from the leeward side of the reef. The core depths examined were limited to those that were of Wenlockian age (428.2-422.9 Ma) and known locally as the Guelph Formation or Brown Niagaran. The relative abundance and general distribution of fauna were analyzed with previously compiled core descriptions, facies analyses, and sequence stratigraphic boundaries (Wold, 2008). This study could be a precursor to many future studies. Future analyses of pore types, sizes and their relationship to facies and fauna as well as hydraulic energy and their influence on diagenesis could be very valuable. Additional studies of fossil diagenesis could also be noteworthy and could be included in studies of porosity. If it could be shown that faunal distribution and relative abundance are factors that influence reservoir characteristics such as porosity and permeability, then these proxies could indicate reservoir quality and point to more or less productive zones within the reef. Findings of this study could also initiate further inquiries into different reefal reservoir types and reefs found in other ancient strata with different fauna (e.g. Jurassic pinnacle reefs (corals and tubiphytes), Cretaceous rudist bivalve, etc.).

CHAPTER II: GEOLOGIC SETTING

Regional Geologic Setting

During the Silurian, 412-438 million years ago, what is now the Michigan basin was located 10-15 degrees south of the equator (Briggs and Briggs, 1974), and was covered in a warm, shallow, epicontinental sea which extended from the Taconic highlands (present-day Atlantic seaboard) across the Allegheny Trough in the Appalachians and across most of the central part of the continent (Figure 1). The coastline was located on the southern edge of the Canadian Shield, which was to the north (Briggs and Briggs, 1974). Midcontinental arches isolated the basin with the Kankakee Arch to the southwest, Findlay-Cincinnati Arches to the south and southeast, Algonquin Arch to the east (Briggs and Briggs, 1974), and the Wisconsin Arch to the west (Gardner and Bray, 1984) as shown in Figure 2. Warm ocean waters met a barrier of patch reefs which encircled the subsiding saucer-shaped (Howell and van der Pluijm, 1999) Michigan basin. Pinnacle reefs developed on the shelf sloping down into the basin, which reached its maximum depth at its center at approximately 200-300 meters (656-984 feet) (Liebold, 1992). The term “pinnacle” has been applied to these reefs due to their isolation, high relief, and small areal extent (Gill, 1977). Shouldice (1955) defined pinnacles as structures over 250 feet high and with a length of less than two miles.

Figure 1: Map of the Earth during the Middle Silurian (425 Ma) by Scotese at http://www.scotese.com/newpage2.htm. The Michigan basin is circled.

Today, the Michigan basin is roughly circular and covers approximately 207,000 square kilometers (80,000 square miles) (Catacosinos, 1991). It is 400 km (248.5 miles) in diameter and almost 5 km (3.1 miles) deep (Howell and van der Pluijm, 1999). The majority of the basin is contained in the lower peninsula of Michigan, but it also extends into the eastern portion of the upper peninsula of Michigan and the bordering edges of the surrounding Canadian province and Midwestern US states (in a clockwise direction: western parts of Ontario Canada close to Lakes Huron and Erie, northern Ohio and Indiana, northeastern Illinois, and eastern Wisconsin – see Figure 2). The 90–150 meters (300-500 feet) tall Niagaran pinnacle reefs are encased in evaporites and dolomite/limestone. Overlying the Silurian deposits are Devonian and Carboniferous sediments, Jurassic red beds, and glacial till. Many Niagaran reefs in the Michigan Basin have been thoroughly dolomitized

and show signs of karsting, dissolution and recrystallization (Gill, 1977). However, moving from the 210 meter (700 foot) thick reef and bank area of the pinnacle belts into the center of the basin, the Niagara Formation becomes progressively less dolomitic. It thins to approximately 30 meters (100 feet) in the center of the basin where it is mostly limestone (Catacosinos, 1991).

Figure 2: Michigan Basin region showing basins, reef banks, pinnacle reef belts, domes, arches, and study locations discussed in text. Redrafted from Gardner and Bray (1984); Lehman and Simo (1989); and Shaver (1991). 8

Regional Stratigraphy

The regional stratigraphy of the Silurian rocks in Michigan includes the following groups: Burnt Bluff, Manistique, Niagara, and Salina (Catacosinos et al., 2000) (see Figure 3). The Niagara Group is split between the Lockport Dolomite and the Guelph Dolomite Formations. The interval of interest in which the reefs are found is the Guelph Dolomite Formation. This formation has also been referred to in the past by the following names: Brown Niagara, Niagaran Reef, Pinnacle Reef, and Engadine Dolomite (Catacosinos et al., 2000). The Guelph and Lockport formations make up the European Wenlock series. Figure 3 shows the stratigraphic nomenclature for the Michigan Basin and surrounding states. It should be noted that the Great Lakes area is fairly devoid of Silurian outcrops. Therefore, almost all of the studies conducted in the area have been done so in quarries. Although quarry exposures present good 2-D representations of reefs, the nature of the quarrying process makes repetition of studies almost impossible since the area studied is either later removed or the quarry is filled with water or sediment. This study has been conducted using subsurface cores drilled from oil and gas wells. These cores are stored at the Michigan Repository for Research and Education and have been preserved and are available for future study.

Michigan N. American N. American Period Epoch Age StageSubsurface Subsurface Informal Wisconsin Indiana Illinois Ohio Group Formation Literature Devonian Pridoli Bass Islands (419‐416) undiff G G FF EE DD Wabash Fm Racine Ludlow CCRacine(Mississinewa Fm Liston Late Cayugan Salina (423‐419) BB and Creek) A‐2 Carb A‐2 Carb 10 A‐2 Evap A‐2 Evap Silurian Ruff A‐1 Carb A‐1 Evap A‐1 Evap Cain A‐0 Carb NiagaraGuelph Dol. Brown Niagaran Wenlock Louisville and Waukesha Middle Niagaran Gray Niagaran (428‐423) Lockport Dol. Waldron White Niagaran Manistique undiff Manistique Brassfield Llandovery Burnt Bluff undiff Clinton Joliet Early Alexandrian Cataract Fm (444‐428) Cabot Head Sh. Salamonie Manitoulin Dol. Ordovician Figure 3: Stratigraphic Nomenclature for Silurian strata in Michigan (Guelph Formation highlighted) and surrounding states (compiled from Catacosinos et al., 2000; Shaver, 1991; Simo and Lehman, 2000).

Changes in Sea Level and Climate During the Silurian

Until recently, the Silurian was thought to have been a relatively stable greenhouse time with only moderate changes in climate as the marine fauna recovered from the end-Ordovician mass extinction (Calner, 2008). Evidence from stable isotope studies of carbon and oxygen have shown that the Silurian was much more volatile than once thought, especially regarding the ocean-atmosphere system (Cramer and Saltzman, 2007). Several sea level curves for the Silurian have been published. Some are global eustatic sea level curves (e.g. Haq and Schutter, 2008; Loydell, 1998; Johnson, 2010) and others are regional (e.g. Johnson 1996; Spengler and Read, 2010). Ross and Ross (1996) developed a global sea level curve that has been questioned as being truly global since Ross and Ross (1996) used data from sections of only one continent, Laurussia (Munnecke et al., 2010). There are inconsistencies between different sea level curves. The researchers neither used the same methods nor do they agree on every highstand or lowstand of sea level or their amplitude. Munnecke et al. (2010) provided a review of these sea level curves. Ross and Ross (1996) used depositional sequences to create their sea level curve with fluctuations of 60 meters (~197 ft.) throughout the Silurian. All of the sea level curves created by Johnson have been tied to generalized graptolite zones. Johnson (2010) reported 10 global highstands with magnitudes ranging from several tens of meters (~65 feet) to more than 70 meters (230 feet) by calibrating highstands with buried coastal topography. The sea level curve produced by Haq and Schutter (2008) was determined using sequence stratigraphy and includes 15 highstands and implies fluctuations of up to 140 meters (~459 feet).

A regional sea level curve by Spengler and Read (2010) shows 11 highstands interpreted as 3rd order sequences in the area of the Wabash Platform based on high frequency sequence stratigraphy. Although sea level curves are provided, no amplitudes for fluctuations are proposed. Ross and Ross (1996), showed seven sea level highstands, two of which occurred in the Wenlock (Figure 4) and a third in the overlying Cain Formation (A-0 Carb) of the Ludlow series. Ross and Ross (1996) considered these to be 1-3 million year, 3rd order sea level fluctuations affecting cratonic shelves but not basins. These three sea level changes were also identified in the cores of Ray Reef studied by Wold (2008) and were correlated across the Michigan Basin by Ritter (2008). Third order sequence boundaries within the Guelph Formation were used in this study to indicate time-equivalent surfaces in determining relative abundance and faunal distribution in the six subsurface cores examined across Ray Reef. Figure 4 shows sea level curves from Ross and Ross (1996) and Spengler and Read (2010) for comparison on a regional level and Johnson (2010) and Haq and Schutter (2008) for a more global perspective.

Figure 4: Global sea level curves determined using sequence stratigraphy (Haq & Schutter, 2008) and generalized graptolite zones (Johnson, 2010). Regional sea level curves determined using high frequency sequence stratigraphy of the Wabash Platform (Spengler & Read, 2010) and graptolite and conodont assemblages from the Illinois Basin (Ross & Ross, 1996). Arrows indicate eustatic sea level highstands identified in Ray Reef by Wold (2008) and across the Michigan Basin by Ritter (2008). (redrafted from Cramer et al., 2011; Munnecke et al., 2010; and Ross and Ross, 1996).

Wind Direction on Reefs in the Michigan Basin During the Silurian

Present day winds develop because the sun heats the air at the equator causing the usually moist, warm equatorial air to rise. The rising air mass causes low pressure at the earth’s surface near the equator. The air masses then move horizontally toward the poles. When the air mass reaches the poles, the cool dry air sinks to the surface creating high pressure at the earth’s surface near the poles. Because air moves from areas of high pressure to areas of low pressure, the surface winds will move along the Earth’s surface from the poles to the equator where the air will warm and rise and begin the cycle all over again. These air movement cycles are referred to as convection cells. So, on a non-spinning Earth, the northern hemisphere would experience strong northerly winds and the southern hemisphere would experience strong southerly winds. These air mass movements between the equator and 30 degrees are called Hadley cells (Thurman and Trujillo, 1999). Due to the eastward rotation of the earth and the difference in velocity at different latitudes, air masses south of the equator are deflected toward the left. This deflection is called the Coriolis effect (Thurman and Trujillo, 1999). The combination of convection cells and the Coriolis effect creates circulation cells. As stated earlier, air is heated at the equator and rises creating a low pressure zone near the equator. As the air rises, it cools, condenses and falls as rain over the equatorial region. As the air travels poleward, it cools and becomes drier and denser and begins to descend in the subtropics, around 30 degrees latitude, both north and south. These circulation cells between the equator and 30 degrees north latitude in the northern hemisphere, and between the equator and 30 degrees south latitude in the southern hemisphere, are called Hadley cells (Thurman and Trujillo, 1999). The high pressure zones that are created around 30 degrees latitude from the dry descending air masses 14

are referred to as subtropical highs. These areas usually experience conditions that are dry and clear. The area of low pressure near the equator where air is moist and rising is referred to as equatorial lows (Thurman and Trujillo, 1999). The air movement along the surface of the Earth is what creates the wind belts. Between the equator and 30 degrees, the air moves from the subtropical highs to the equatorial lows. These are called the trade winds. In the southern hemisphere, the wind blows from the southeast to the northwest due to the Coriolis effect creating the southeasterly trade winds (Thurman and Trujillo, 1999). In the northern hemisphere, the wind blows from the northeast to the southwest creating the northeast trade winds. A south to southeasterly dominant wind direction during the Silurian is assumed for the Michigan Basin since it was located between the equator and 30 degrees south latitude (Copper, 2002; Scotese, 2003; Blakey, 2011) (Figure 5).

Figure 5: Paleogeographic reconstruction of Laurentia and the epicontinental and epeiric seas during the Silurian (430 Ma) with the location of the Michigan Basin indicated by the box. Arrows show the surface winds between the equator and 30 degrees south blowing from the south- southeast to the north-northwest. Modified from Blakey (2011) and Scotese (2003).

Wold (2008), in addition to assumed easterly trade winds, based the interpretation of a predominantly south to southeast wind direction on Ray Reef using a combination of reef geometry and reservoir characteristics. The southern end of the reef has a steep margin with thick packages of stacked facies which have higher porosity and permeability values (Figures 6 and 7). This was interpreted as being 16

caused by increased cementation of skeletal grains which allowed the angle of declivity to become greater as it aggraded and prograded and was interpreted to be the windward side of the reef. The northern end of the reef has a lower angle of declivity, contains thinner packages of stacked facies which prograde, contains more fine-grained sediment which was swept off of the reef crest, and has lower porosity and permeability values and was therefore interpreted to be the leeward side of the reef (Figures 6 and 7).

Figure 6: Structural contour model of Ray Reef showing distinction between windward and leeward margins in aerial and profile views (Wold, 2008). Windward margin is characterized by a high angle of declivity, thick packages of stacked facies and progradational as well as aggradational growth. The leeward margin has a more gentle slope and thinner packages of facies which prograde only. 17

B) C)

Figure 7: A) Cross section from B to B’ (south/windward to north/leeward) across Ray Reef. B) Cross-section of Ray Reef showing the relationship between primary depositional facies and porosity and permeability values with B’ (north) to the right. The areas of highest porosity and permeability are found on the windward margin, in grainstone facies, and near exposure surfaces. The leeward margin and Bioherm and Restricted Facies, consist of more fine-grained sediment and have lower porosity and permeability values. C) Cross-section of Ray Reef with sequence boundaries drawn in yellow or brown with B’ (north) to the right (Wold, 2008).

Sequence Stratigraphy Boundaries

Since this study relied on previously interpreted sequence boundaries (SB) in making interpretations, a short overview of this information is in order. The entire

Silurian comprises one 2nd order sequence. Although the Silurian is the shortest period in the Phanerozoic (443-416 Ma), it falls within the 10-50 million year time span of second order cycles that are thought to be driven by a combination of tectonics and the volume of ocean basins, with lesser influence caused by ice volume changes (Read et. al, 1995) . Within this second order cycle of the Silurian are multiple superimposed third order cycles. Third order cycles range from .5 – 5 million years long and are thought to be caused by changes in ice volume (Read et. al, 1995). High frequency cycles (fourth and fifth order sequences or Milankovitch cycles) are thought to be driven by the shape of the Earth’s orbit around the sun (eccentricity) of 100 kyrs and 400 kyrs, changes in the Earth’s tilt (obliquity) of 40 kyrs, and changes in the Earth’s “wobble” (precession) of 20 kyrs (Read et. al, 1995). It is the fourth and fifth order sequences that are thought to control reservoir quality in carbonates (Grammer et al., 2004). Within the Ray Reef cores, Wold (2008) identified three 3rd order sequences. The datum for the 3-D model was set at the stratigraphic top of the Lockport

Dolomite (SB1). This datum was chosen because it is a relatively flat surface that dips only slightly (.5-1.5 degrees) toward the center of the basin. Sequence Boundaries 2 and 3 were determined using idealized facies stacking patterns and flooding or exposure surfaces. Sequence Boundary 4 was not present in all cores but was selected in the overlying Salina sediments containing anhydrite. The boundary was identified using neutron density logs where the signature of the reef (between 1000-2000 API) increased markedly to the signature of the evaporites (between 3000- 19

4000 API). Wold (2008) also identified fourth order high frequency sequence boundaries (HFSB) across Ray Reef.

CHAPTER III: PREVIOUS WORK

General Overview of Michigan Basin Studies of the Silurian

The first Silurian reefs in the Michigan Basin area were discovered in Wisconsin by James Hall in 1862 (Shaver, 1991), followed by oil discovery in Indiana in 1865 (Shaver, 1991) and southwestern Ontario in 1889 (Gill, 1985). However, oil exploration in Michigan was not heavily pursued until the 1950’s. Up to that point, what was known of these structures was gleaned from qualitative academic studies of outcrops and quarries that focused on creating faunal lists, determining biostratigraphy, interpreting the paleoecology, and understanding reef growth and development (Lowenstam, 1950; Textoris and Carozzi, 1964; Jodry, 1969; Shaver, 1974, 1977). Lowenstam’s studies in 1949 and 1950 were instrumental in validating Michigan Basin Silurian structures as “true” reefs and influencing an interest in the possibility of hydrocarbon production from them (Copper and Brunton, 1991). Throughout the 1960’s, oil exploration and development flourished in the Michigan Basin (Mantek, 1973) and provided new sources of data for study (e.g. subsurface cores, wireline logs, and gravity data). During the 1970’s and 1980’s, the focus of most Niagaran reef studies in the Michigan Basin concerned the diagenesis and/or timing of Niagara and Salina carbonate and evaporite deposits which make these reefs such good reservoirs (Gill, 1973; Mesolella, 1974; Briggs and Briggs, 1975; Huh et al., 1977; Sears and Lucia, 1979). During this time, reef models were expanded from the simple core and flank models to descriptions of facies and corresponding interpretations of environments of deposition. These models proposed reef growth through three or four stages of development (Briggs and Briggs, 1974; Huh et al., 1977; Gill, 1973, 1977; Shaver, 21

1974; Balogh 1981). Workers made distinctions between stages based on fauna and lithology and attempted to determine the sequence of deposition of strata in the reefs and surrounding sediments/evaporites based on models of subsidence within the basin during static sea level (Briggs and Briggs, 1975; Sears and Lucia, 1979), changes in salinity with static sea level (Gill, 1973, 1977; Briggs and Briggs, 1974; Huh et al., 1977) or changes in regional sea level that were reflected in the cyclicity of sediment deposition (Mesolella, 1974). Most identified an initial bioherm, an organic or “true” reef, a restricted stage and some identified a supratidal stage. Some studies identified or observed exposure horizons within the reefs (Gill, 1977; Balogh, 1981). However, all of these studies were based on lithostratigraphy and time-correlation of facies was known to be diachronistic. In 1977, Vail et al. initiated a new approach to stratigraphy using unconformities in reflection seismic lines. They found that these seismic reflectors were good indicators of time-correlative surfaces. By identifying exposure and/or flooding surfaces, strata can be divided into genetically related units, or sequences, with an equivalent time reference across strata. When an environment of deposition can be determined and a model of ideal facies packages proposed, then the combination of the theoretical model and the observed genetic units can be used to make predictions about areas where empirical data is lacking. This is a primary advantage of using a sequence stratigraphic approach (Eberli and Grammer, 2004). Recent studies of Silurian pinnacle reefs in the Michigan Basin have used a sequence stratigraphic approach to further refine our understanding of reef development and reservoir characteristics (Ritter, 2008; Wold, 2008; Qualman, 2009). It is the third order sequence boundaries in Ray Reef determined by Wold (2008) that were used in this study as time correlative surfaces in determining relative abundance and general 22

distribution of fauna in this study.

Ancient Analogs

Qualitative Studies of Faunal Relative Abundance and Distribution Outside of the Michigan Basin and During Other Time Intervals

Hydraulic Energy and Reef Framebuilding Morphology

James (1983) and James and Bourque(1992) described general reef zonation trends by qualitatively combining metazoan morphology as controlled by water energy levels, carbonate classification, and growth forms to create a model for interpretation and prediction of Cenozoic reef environments (Figure 8). They proposed that the Reef Crest Facies received the most wind and wave energy and were therefore limited to those encrusting and sheet-like forms of fauna capable of sustaining such forces. If wind and wave energies were moderate or episodic, morphologies with short, stout branches or blades could occur with the encrusting forms on the crest. Older scleractinian reefs had hemispherical to massive forms on the crest. James and Bourque (1992) proposed that the Reef Flat Facies consisted of material swept off of the reef crest which varied from large skeletal cemented clast pavements with nodules of coralline algae where wind and wave energy was high, to clean carbonate sand shoals where wave energy was moderate. The Back Reef Facies was characterized by sand- and mud-producing fauna, e.g. calcareous green algae. They described the coral in the back reef as stubby and dendroid or globular. James and Bourque (1992) also were able to distinguish windward from leeward margins based on fauna due to “bad water”. They described “bad water” as water driven off of the platform downwind which was warm, depleted in oxygen, and 23

contained fine-grain sediment. Due to this “bad water”, the leeward margin was inhibited in its reef growth for several tens of meters in depth and was either bare rock or rock covered in fleshy algae. James and Bourque (1992) considered stromatoporoids to have had encrusting or large, enveloping growth forms in high energy areas such as the reef crest due to their anchorage in the sediment. They considered platy forms to have inhabited rough water and the smooth, totally enveloping forms to have been found in the quiet water zones below wave base, in the back reef (domal, bulbous, and dendroid forms), or in the lagoon (delicate forms, stick-like amphiporoids). However, they did not interpret stromatoporoids to be able to withstand surf zone conditions based on sand- and gravel-rich facies containing ragged, reworked stromatoporoid skeletons that were up to several tens of centimeters high and interpreted as an indication of scouring and digging during storms (Kershaw, 1979). Stromatolite reefs consisting of domes, linked domes, columnar and elongate stromatolites were all considered forms found in high-energy settings. Stromatolites found on isolated deep subtidal and slope reefs had conical forms.

Figure 8: Model of zoned marginal reef showing morphologies of fauna relative to energy level and position on reef as well as lithologies and reef type: coral reef (mainly Cenozoic), stromatoporoid reef (mainly Siluro- Devonian) and stromatolite (mainly early Proterozoic) (redrafted from James and Bourque, 1992).

Water Depth and Reef Zonation in Western Canadian Devonian Reef Complexes

In 1974, Klovan qualitatively described facies from a Western Canadian Devonian reef complex and compared them to Holocene analogs. The similarities between the Givetian Rainbow-Zama reef tracts and the Michigan Niagaran pinnacle reef trends are striking. Klovan states that many of the reefs attained 600 ft (182.8 m) thicknesses and were encased in evaporites. The reefs are proposed to have been built on antecedent crinoidal mud mounds (Langton and Chin, 1968). He also notes that this reef tract is surrounded on all sides by barrier reef complexes. Klovan evaluated the fossils in these reef complexes, as was pioneered by Lecompte (1958), using water depth as the determining factor in zonation of communities: 1) a quiet water coral community, 2) a semi-rough tabular stromatoporoid community, and 3) a turbulent-water massive stromatoporoid community. Klovan went on to compare his previous work on approximating water depth of faunal growth in Late Devonian bioherms (Embry and Klovan, 1972) to modern Caribbean coral reef water depth zones as studied by Logan (1969) (Figure 9). He found that there were four stages of development in the Rainbow area pinnacle reefs: 1) an initial quiet water, probably deep, base formed by a crinoidal micrite; followed by 2) colonization by corals and tabulate stromatoporoids of a “true reef”; 3) vertical growth of massive stromatoporoids in the center of the reef with talus on the fore reef; and finally, 4) a supratidal setting with restricted fauna (Klovan, 1974). These four stages are very similar to the four stages of Michigan Basin Silurian pinnacle reef growth described by most workers (Briggs and Briggs, 1974; Huh et al., 1977; Gill, 1973, 1977; Shaver, 1974; Balogh 1981; Wold, 2008). Klovan also found evidence of differentiation between windward and leeward

margins of the reefs in the Redwater Reef Complex. Dips of 15 degrees and abrupt facies changes into the basin on the windward side were distinguished from gently sloping leeward sides with gradual facies changes over long distances basinward (Klovan, 1974). These findings are consistent with early, rapid cementation of steeper windward margins and more gradual leeward margins found in the modern Bahamas (Grammer 1993a, 1993b, 1999).

Figure 9: a) Inferred Devonian depth zones based on paleoecological comparisons with b) Holocene ecological zones (after Logan, 1969). (Klovan, 1974)

Hydraulic Energy, Faunal Morphology and Zonation, and Early Submarine Cementation in a Middle to Upper Devonian Iberg Reef, Germany

A 1995 qualitative study of the Middle to Upper Devonian Iberg Reef of Germany by Gischler determined that paleowind and/or paleocurrent influenced the faunal distribution as well as the early submarine cementation of the reef. Gischler provided a figure that displayed the morphological forms of fauna found on the leeward fore reef, back reef, and windward fore reef (Figure 10). He placed

encrusting/platy stromatoporoids and corals, dendroid stromatoporoids, Thamnopora, and crinoids on the leeward side near sea level with branching corals deeper down the fore reef on the leeward side. In contrast, he found massive stromatoporoids and bulbous corals on the windward side near sea level with crinoids, encrusting and dendroid stromatoporoids, Thamnopora, and branching corals further down the windward forereef. The leeward lagoon was inhabited by large thickets of branching rugose corals and a mixture of other fauna from the back reef and fore reef. Reservoir characteristics were not within the scope of Gischler’s study, however he did conclude that cementation was intensive on the windward (southeastern flank) side of the reef due to pore spaces being constantly flushed by high wave exposure (Gischler, 1995).

Figure 10: Reconstruction of paleoecology of Devonian Iberg Reef, Germany, showing wind direction and faunal morphology. Drop-off and reef wall are presumed (redrafted from Gischler, 1995).

Although these studies, (Klovan, 1974; Gischler, 1995), were conducted on 28

reefs of Devonian age, the majority of the fauna that occupy Silurian reefs are the same or very similar. Also, due to the striking similarities between the Rainbow/Zama reefs and the Silurian pinnacle reefs of the Michigan Basin, these are both applicable models for ancient faunal distribution on windward and leeward reef margins for this study.

Previous Qualitative Studies of Michigan Basin Silurian Reef Faunal Relative Abundance and General Distribution

According to Perrin et al. (1995) qualitative studies have used the classic approach of reconstructing reef zonation by arranging inshore-offshore trends based on interpretations of facies, associated taxonomic lists and morphologies, lithologies, and geometric relationships between facies. This is true of two studies cited by Perrin et al. (1995) from the Great Lakes area (Copper and Fay, 1989; Lehmann and Simo, 1989).

Previous Quantitative Studies of Relative Abundance and General Distribution of Fauna

In a review of quantitative methods of reef zonation conducted by Perrin et al. (1995), it is stated that there have been very few quantitative studies of faunal assemblages. Perrin lists the techniques used by previous workers as: in situ mapping of coral colonies or reef builders as recorded from vertical faces, bedding surfaces, or quadrats (Kissling and Lineback, 1967; Konigshof et al., 1991; Weidlich et al., 1993); or from point-counting from quadrats (Zankl, 1969; Schafer, 1979; Budd et al., 1989; Stemann and Johnson, 1992); and transect point-counting along vertical sections (Collins, 1988). None of these studies had goals of determining reef

zonation, but rather were focused on improving the distinction between reef facies and quantitatively determining the faunal composition of the assemblages. Of these, only the study by Kissling and Lineback (1967) is similar in time frame or geographic area (Devonian Falls of the Ohio) to the Wenlock Reefs of the Michigan Basin. Although there have been several published reports of species counts from reefs in the Michigan Basin, they are usually published as paleontology seminar papers (Indiana University Paleontology Seminar, 1980; Indiana University Paleontology Seminar, 1976) or field guide books (Pray, 1976; Mikulic, 1985; 1987; Mikulic and Kluessendorf, 1988) and lack other sedimentary or stratigraphic data that is necessary to draw conclusions about hydrodynamic regimes or quantitative data concerning relative abundance or general distribution. In the Great Lakes Area, there have been three peer-reviewed published qualitative studies. Copper and Fay (1989) studied the Early Silurian Manitoulin Island reef, Lehman and Simo (1989) studied the Pipe Creek Jr. quarry reef, and Shaver (1974) studied the middle Silurian reefs of Northern Indiana (see Figure 2). There have been four quantitative peer-reviewed published studies in the Great Lakes Area that focused on faunal abundance in Silurian reefs (Ingels, 1963; Watkins, 1993; Balogh, 1981; Schneider and Ausich, 2002). However, only one of these studies (Balogh, 1981) involved the study of Silurian (Wenlock) reefs in the Michigan Basin southern pinnacle reef belt. This was an unpublished Master’s Thesis.

Thornton Reef Complex (Thornton, Illinois)

Ingels (1963) studied the famous Thornton Reef Complex found in a quarry in Thornton, Illinois. This was a quantitative study using percentages of fauna as 30

estimated using rough point counts in quadrats of four square feet along transects designed to “sample the maximum number of lithologic and paleontologic variations” (Ingels, 1963). Additional “spot” samples were taken on satellite reefs of the complex and adjacent interreef strata. Parameters recorded were: taxonomic groups (diversity); number of individual in each group (abundance); lithologic character; average bed thickness (differentiated based on lithology); size of fossil fragments (“mainly crinoid stems”); and structural attitudes (Ingels, 1963). There were no complex calculations of diversity (Shannon-Weaver index, etc.) nor were there calculations of framework density (areal coverage). Ingels (1963) created topographic maps with biosome distributions where boundaries enclose areas where “guide fossil(s) constitute 20% or more of the population”. Ingels proposed a prevailing west-southwest wave and wind current. He outlined six biotopes with a windward wave-resistant stromatoporoid ridge, a coral rampart, a dead-reef flat, a lagoon beach, a lagoonal crinoid meadow, and a leeward wave-resistant stromatoporoid ridge. Ingels also concurred with Kuenen’s (1950) observation that, “The living reef tends to grow windward, while detritus is dumped to leeward…”

Southeastern Wisconsin Quarries

Watkins (1993) conducted point counts on polished slabs from five quarries in southeastern Wisconsin (Racine Formation) to obtain the relative abundance of various Silurian reef fauna. He used the specimen collections and data from the Milwaukee Public Museum to compare reef fauna of Wenlockian age from southeastern Wisconsin to reef fauna in other parts of the Michigan Basin, based on literature findings. He reported finding relative abundances of 99% crinozoans and 31

less than 1% gastropods and favositids in the Franklin flank beds; 97% crinozoans, 2% stromatoporoids, and less than 1% brachiopods and trilobites in the Horlick Quarry flank beds; 74% crinozoans, 22% stromatoporoids, 3% brachiopods, 1% laminar bryozoans, and less than 1% trilobites in the Horlick Quarry reef core; 40% stromatoporoids, 31% crinoids, 21% brachiopods, 5% favositids, and 3% ramose bryozoans in the Francey Quarry reef core; 51% stromatoporoids, 23% crinozoans, 19% favositids, 3% solitary rugosans, 2% halysitids, 1% ramose bryozoans, and less than 1% brachiopods in the Brown Deer Road reef core;and 62% stromatoporoids, 20% ramose bryozoans, 17% crinoids, and less than 1% solitary rugosans, brachiopods, and gastropods in the Grafton reef core. Watkins found that the S.E. Wisconsin Wenlockian reef fauna were typical of those found in other parts of the Michigan Basin. He also found that the reef fauna were not necessarily unique to the reefs, but were also found in level-bottom communities; although in the reefs they had higher species diversity, greater numbers of guilds, and more extensive tiering. Watkins used Bambach’s (1983) definition of guilds as fossils divided into class-level taxonomy and used to infer that fossils in the same guild used the same resources (food and space) in the same ways. Tiering, in this study, is a term used to describe the height above the bottom that the sessile, epifauna fed by suspension (0-5 cm, 5-10 cm, etc.) However, Watkins determined faunal abundance on point counts alone. This approach does not indicate the proportion of fauna to rock volume which determines the density of fauna. He also limited his facies to flank beds and reef core with no further indications of faunal zonation or wind/current influence on distribution.

Michigan Basin Southern Pinnacle Reef Belt (Macomb County, Michigan)

Balogh (1981) studied single cores from three Michigan Basin Silurian reefs, including one core from Ray Reef (Busch-Kuhlman-Tubbs 1-36). Balogh’s main purpose was to determine the paleoenvironment and depositional histories of three reefs in southeastern Michigan based on biota in order to develop a model of reef growth. He used a combination of lithological and facies characteristics, termed lithotopes, to determine percentages of faunal and lithological allochems in 23 lithotopes (A-W). Within these lithotopes, he determined the relative abundances of biota and noted growth form morphologies to aid in determining environment of deposition. Because Balogh only studied one core from each reef (Ray Reef, Peters Reef, and Belle River Mills Reef), his model is static and does not indicate facies, or lithotope, changes through time and therefore no heterogeneity or lateral variability is portrayed. Although Balogh did not indicate windward/leeward margins, his lithotopes are arranged to indicate hydrodynamic energy relative to wave base, low and high tide in fore reef knoll, reef crest, back reef, and lagoon settings.

Reed North Quarry (Fairborn, Ohio)

Schneider and Ausich (2002) studied framebuilders in the Brassfield Formation of a rare, non-dolomitized early Silurian reef in a southwestern Ohio quarry. Their focus was on comparing the diversity of fauna from the Brassfield Formation to the Jupiter Formation of Quebec which is also not dolomitized, is of similar age, but grew in a different paleolatitude. They determined that in the studied patch reef there was: differentiation in faunal distribution with solitary and colonial rugose corals more abundant on the windward side; stromatoporoids more abundant 33

on the leeward side; and tabulate corals, crinoids and bryozoans evenly distributed across the reef (Schneider and Ausich, 2002). However, these relationships were inferred from a bedding surface, with an area of 20-by-20 meters, across the core of an in situ reef in the quarry. Out of the 200 square meter area, only 75 square meters had patch reef exposed. Relative abundance was calculated using point counts and percentages of total population, not percentages of area occupied (framework density). Also, this formation is of Early to Early Middle Silurian age (see Figures 2 and 3).

Previous Studies of Michigan Basin Pinnacle Reefs Using Sequence Stratigraphy

Ray Reef

Wold (2008) examined eight cores from Ray Reef and produced a 3-D model in Petrel based on facies analysis and sequence stratigraphy (Figures 6 and 7). Like Klovan (1974) and Grammer (1993a), Wold found that the windward margin was steeper and the leeward margin more gently sloping. Wold also found, as Grammer (1993a) did, that the windward margin with its predominantly skeletal grainstones had higher porosity and permeability values. Wold identified three stages/facies groups in general agreement with previous workers: Facies 1&2 mud-rich bioherm;

Facies 3&4 reef; Facies 5 restricted. Wold identified three 3rd order sequence boundaries which were correlated between multiple cores. Fourth and fifth order sequences were also identified in the cores but did not correlate with each other. Wold found that the 4th order sequences controlled the reservoir distribution and facies variability and suggested that wind could have been an influential factor.

A Study Comparing Silurian Pinnacle Reefs from the Northern and Southern Trends

Ritter (2008), in studying Silurian pinnacle reefs in both the northern and southern trends of the Michigan Basin, found a distinct relationship between porosity and permeability and the position of the facies in the sequence. Specifically, Ritter found that facies that were physically closer to the 3rd order sequence boundaries experienced preferential dissolution and enhanced porosity and permeability due to exposure, while facies located closer to the 4th order sequence boundaries had diminished porosity and permeability due to early cementation and occlusion. In the current study, the preferential dissolution of third order sequence boundaries due to exposure negatively affected both the recognition of fauna and the calculated relative abundance and distribution along these time-equivalent surfaces.

Modern Analogs

There have been several studies of modern reefs and the influence of wind and current on faunal distribution. Although there is no perfect modern analog for Silurian pinnacle reef growth, the Bahama platform has similarities in approximate size, latitude, climate, shallow water depth and trade winds. Also, studies of the influence of wind and wave energy on faunal zonation and coral growth morphology (Geister, 1977; Gischler and Lomando, 1999) in the Caribbean and Belize and faunal abundance and cementation of the Tongue of the Ocean, Bahamas (Grammer, 1993a) were considered as modern analogs.

CHAPTER IV: MATERIALS AND METHODS

Materials

There are sixteen sub-surface cores available for study from Ray Reef. Of those, eight cores were chosen for description and used to determine stratigraphic sequences in a previous study by Wold (2008) due to their quality and continuity of core footage. This study incorporated the previous descriptions, facies determinations and sequence stratigraphic boundaries of these cores and focused on the further examination of six of the eight cores to determine relative faunal abundance, diversity, framework density, and general faunal distribution throughout Ray Reef (Table 1; Figure 11). Thin sections (42) from two crest wells (Halmich 2-1 and BTK 1-36) were impregnated with blue epoxy, stained with Alizarin Red S and analyzed using a petrographic microscope to aid in identification of cement in hand samples (see Figures 12 -23).

Table 1: Well name, permit number, footages, and facies data for well cores from Ray Reef used in this study.

Permit Footage Facies Well Name Number (total feet) 1 2 3a 3b 4 5

Busch-Tubbs-Kuhlman No. 1- 36 (CPC R-107) 25203 2952-3264 (312) N Y Y Y Y Y Halmich No. 2-1 (CPC-R112) 24763 2923-3219 (296) N Y Y Y Y Y Jacob No. 1-36 (CPC R-111) 24987 2934-3251 (317) N N Y Y Y Y Laskowski No. 4 (CPC R-118) 25547 2979-3241 (262) Y Y Y N Y Y Laskowski No. 5-1 (CPC R- 121) 25832 3190-3250 (60) N N Y N N Y Percy No. 2-2 25100 3198-3252 (54) N N Y Y Y Y

MGRRE MASTER PROJECT

Macomb County, Michigan

Ray Reef

ATTRIBUTE MAP OB Zone: TROUT - FACIES_1 Exactly Matches "1" Zone: TROUT - FACIES_2 Exactly Matches "1" Zone: TROUT - FACIES_3A Exactly Matches "1" Zone: TROUT - FACIES_3B Exactly Matches "1" Zone: TROUT - FACIES_4 Exactly Matches "1" Zone: TROUT - FACIES_5 Exactly Matches "1"

WELL SYMBOLS Dry Hole Gas Storage OB Gas Storage Observation Location Only

0 0.2 0.39 MILES 25203 0 0.13 0.25 0.38 0.5 0.63 0.75 Busch-Tubbs-Kuhlman 1-36 KILOMETERS

November 11, 2011

24987 OB Jacob 1-36

24763 Halmich 2-1

OB OB

25547 Laskowski 4-1

25100 Percy 2-2

25832 Laskowski 5-1

PETRA 11/11/2011 3:59:35 PM

Figure 11: Ray Reef with the location of cores utilized in this study and the direction of inferred paleowind. 37

Methods

The main focus of this study was to quantitatively determine the relative abundance and general distribution of fauna in a single Wenlock reef (Ray Reef) and to analyze these parameters in different hydraulic energy settings of that reef (e.g. windward vs. leeward vs. crest). Relative abundance in this study is an expression of the percentage of an individual phylum when the sum of phyla equals one hundred percent. For example, 50% stromatoporoid, 30% tabulate coral, and 20% bryozoan equals 100%. General distribution in this study refers to where on the reef different assemblages of fauna are located in relation to hydraulic energy, e.g. windward side, crest, or leeward side. According to Perrin et al. (1995), there are three main parameters that can be used to characterize the distribution and abundance of reef framebuilders: 1) framework density, 2) reef-builder diversity, and 3) composition of reef-building assemblages. However, there is no general consensus on the most accurate method to evaluate these parameters (Perrin et al., 1995).

Framework Density

In developing a new quantitative method for determining ancient reef

zonation, Perrin (1995) defined framework density as the “quantity of reef building skeletal material preserved in growth position compared to the quantity of sediment, cement and primary porosity”. Since the cores from Ray Reef are all dolomitized, primary porosity has been altered. Also, studies have shown that the majority of reefs are composed of debris and not fauna in growth position (Friedman, 1985). In the area contiguous to the Great Barrier Reef of Australia, Bennett (1971) found that only 2-15% of the total skeletal debris was of coral fragments. Therefore, in this study, all 38

fauna whether in growth position or not are included in framework density because, as also stated by Perrin et al. (1995), density reflects both the reef facies and reef community. Since density is closely dependent on the abundance, (the number of individuals or colonies), size, and morphologies of the reef builders (Perrin et al., 1995), all fauna were included in calculations of density. Note was taken of which specimens were in growth position. When faunal zonation was determined, only specimens in growth position along the time correlative sequence boundary area were included to more accurately represent fauna in place at the time of deposition and not relocated debris. Framework density, as calculated in this study, is basically the relative abundance of fauna expressed as the percentage of core that is covered by fauna when the total core area equals one hundred percent. For example, stromatoporoid coverage of 10%, unidentified coverage of 10%, tabulate coral coverage of 5%, rugose coral coverage of 5%, bryozoan coverage of 2 %, crinoid coverage of 2%, and cement coverage of 6% equals a total faunal/cement coverage of 40% which means that 60% of the coverage is matrix and pore space with the sum of all equaling 100% coverage.

Diversity

Diversity, as expressed in this study, refers to taxonomic richness only, e.g. facies with greater numbers of different phyla present (or greater numbers of suborders of tabulate corals) are more diverse than facies with fewer numbers of different phyla present. No complex calculations such as the Shannon-Weaver index of diversity were conducted.

Distribution and Composition of Reef-Building Assemblages

Modern studies of present-day reefs express coral zonation as: 1) a gradual morphological modification of individual coral species; i.e. zonation of growth forms 2) species zonation; and 3) a gradual modification of communities due to the effect of species zonation, i.e. assemblage zonation (Perrin et al., 1995). The term ‘zone’ was defined by Wells (1954) as “an area where local ecologic differences are reflected in the species association and signalized by one or more dominant species”. This study used a combination of taxa identification, abundance and dominance, morphology, and hydraulic energy settings to determine the zonation of a single reef along third order sequence boundaries in six subsurface cores located throughout the reef. Dominance was determined as the two most abundant taxa found at the sequence boundary. Zonation was mapped on previously interpreted third order sequence boundary maps (Wold, 2008) using core description and relative abundance and distribution data collected in the present study.

Description of Various Quantitative Methods Used in Modern Reef Ecology Studies

Quantitative methods on modern reefs have employed either plot techniques or plotless techniques. Plot techniques allow the worker to obtain numbers of fauna within a quadrat. The quadrats may either be randomly placed or distributed at predetermined, equally spaced sampling units over a continuous belt. Within each quadrat, the fauna are either individually counted or their coverage is estimated. Plot techniques usually record the following parameters: number of species, number of individuals for each species, total cover, cover of each species, and density (Perrin et al., 1995). The plotless techniques are of two types: plotless distance-measurement 40

methods and line transect methods. The plotless distance-measurement methods can be applied in two different ways. In the first, a random selection of individuals from an entire population is selected and used as an endpoint to measure the distance to its nearest neighbor. This is the same as the nearest neighbor method and the random pair method (Perrin et al., 1995). In the other method, random sampling points are used as endpoints to measure the distance to the nearest individual. This is the same as the closest individual method, the point centered quadrat method, and the wandering quarter method and only allows the study of one group at a time, e.g. corals (Perrin et al., 1995). This method records the following parameters: numbers of species, estimates of total cover, number of individuals for each species, density, and mean area per individual (Perrin et al., 1995). The second plotless technique, the line transect method, uses either an equally spaced point transect or a continuous transect. In the equally spaced transect method, a transect line is divided into equally spaced intervals which are further divided into a predetermined number of equally spaced points. The species are recorded at each point and each block is estimated for frequency of individuals (Kershaw, 1957). The value of this method is that different groups of organisms and substrates can be evaluated. However, this technique only records the frequency and cover and is based on the assumption that “the total number of points recorded for one species divided by the total number of points recorded along the transect represents a valid measure of the species cover” (Perrin et al., 1995). In the continuous transect method, every part of the transect line that is intercepted by an individual or component is recorded. This method relies on the assumption that, “the ratio of total transect length being intercepted by organisms to the overall length of transect is equivalent to the ratio of the total area occupied by the 41

living organisms to the overall area” (Perrin et al., 1995). The line intercept transect method is widely used in modern coral reef ecology studies (Perrin et al., 1995).

Quantitative Methods Used in Paleoecology Studies of Fossil Reefs

Very few ancient reefs have been quantitatively studied for their faunal composition. Of the studies that have been published, most have been conducted on outcrops using methods devised to map in situ reef builders or coral colonies from vertical faces, bedding surfaces, or quadrats (Perrin et al., 1995). Studies of vertical surfaces using quadrats can provide good estimates of coral assemblage composition and framework density but they are time consuming and inevitably contain time- averaging elements that render comparisons with modern reefs untenable (Perrin et al., 1995). Neither plotless techniques using a point distance nor quadrat techniques are suitable for studies where the fauna are of different size ranges. Use of the line intercept transect requires a time-correlative surface. Some workers have used a surface parallel to general stratigraphy or an internal paleosurface for a reference line (Perrin et al., 1995). The line intercept transect has the advantage of direct comparison between different parts of the same reef at the same level. Because this method is frequently used in modern reefs, data are comparable between modern and ancient (Perrin et al., 1995). This method also allows for data capture from different fauna as well as matrix, micritic crusts, diagenetic products, and porosity (Perrin et al., 1995). This study is an evaluation of a single reef using six subsurface cores. The use of subsurface cores is a deciding factor in which of the above described methods can be used. The continuous transect line method is the most comprehensive, and is the most obvious choice given that there are six vertical cores which are only four 42

inches in diameter. One of the downfalls of this method is that a time-correlative surface is required. However, since sequence stratigraphically derived sequence boundaries have already been established for this reef by a previous study (Wold, 2008), time correlative surfaces are known at the third order sequence level and can be compared directly from each core found on different sides of the same reef. Also, this method allows collection of data not only from fauna but also matrix, cement, flooding surfaces, and exposure surfaces. Because the width of the core is only 4 inches, sometimes the morphology of a particular specimen was not possible to determine (e.g. a stromatoporoid crosses the diameter of the core and cannot be identified as laminar or hemispherical or domal). Also, the limited width decreased the coverage area and caused flat, long specimens to have their area (framework density) under calculated as compared to smaller or taller, more narrow specimens. In addition, Perrin et al. (1995) has emphasized that in-growth position specimens need be the only ones counted in order to accurately reconstruct reef zonation since skeletons are often reworked in the reefal environment. However, as stated earlier, most studies indicate that the majority of reef composition is debris. In order to determine if this is true for ancient fossil reefs, percentages of faunal elements smaller than 4 mm were estimated per foot and faunal fragments larger than 4 mm were counted and noted whether they were in-growth position or not. For purposes of faunal density, all fauna whether in growth position or not were included. However, when reef zonation was analyzed, only fauna in growth position were included. Also, as stated by Perrin et al., (1995) the need to indicate the quality of the preservation of the fossils is important in being able to compare analysis from different areas of the same reef, as well as to reefs from different areas or time 43

frames. Perrin used the terms “scree” for non-outcropping areas and the single category of “unidentified” to capture the areas not identifiable to coral or coralline algae genera. This study will capture the quality of the data by including a single category of “unidentified” for those areas of core that definitely showed faunal fabric but was diagenetically altered to the point that identification to phylum was not possible.

Skeletal Mineralogy and Diagenesis

The skeletal mineralogy of marine organisms has been studied by paleontologists and carbonate petrographers since Sorby (1879). Original mineralogy of some fossils is still controversial. This is especially true of one of the main reef framebuilders during the Silurian, the stromatoporoids. In determining original mineralogy, there have been two methods employed. In one, phyla with extant species have been directly studied and their mineralogy determined. For example, crinoids are known to be, and assumed to have always been composed of high Mg calcite. Other phyla, which do not have extant species, have been compared with other phyla in the same sample that are of known skeletal mineralogies to determine the amount of preservation. Using this data, a hypothesis is put forward as to the original mineralogy. Many workers confine their interpretations to either calcite or aragonite. Few have attempted to distinguish between high Mg calcite and low Mg calcite (Porter, 2010). In the case of stromatoporoids, there are two schools of thought. Some workers propose that stromatoporoids were originally composed of aragonite (Stearn, 1972, 1975; Trabelsi, 1989). Trabelsi based his conclusion on the observation that remnants of relict radial fibrous features could be found within some skeletons as 44

compared to the galleries which were filled with clear, equant calcite. Stearn (1972) proposed that stromatoporoids were sponges and based this hypothesis on the morphological similarity between modern aragonitic sclero-sponges and stromatoporoids as well as the observation that stromatoporoid skeleton microstructure fabrics were recrystallized. Stearn observed similar recrystallization in Pleistocene scleractinian corals, which were originally composed of aragonite but were diagenetically altered with the aragonite recrystallized to calcite. He concluded that the in situ recrystallization of aragonite to calcite could produce the microstructure fabrics that he saw in stromatoporoids, and that stromatoporoids were originally aragonitic. Other workers (Galloway, 1957; Rush and Chafetz, 1991) maintain that stromatoporoids were composed of calcite. Galloway based this on the observation that Paleozoic stromatoporoids generally had preserved structural elements. Rush and Chafetz (1991) in studying stromatoporoids from the Devonian Helderberg strata also proposed that stromatoporoids were originally composed of calcite. However, they went one step further and proposed that the original composition was high- magnesian calcite that was later altered by an in situ, thin-film diagenetic process. They based this hypothesis on the following observations: 1) Echinoderms found in the Helderberg strata, which are known to be composed of high-magnesian calcite, exhibit relict, inclusion-rich zones in diagenetic low-magnesian calcite which is very similar to the type of preservation seen in the stromatoporoids; 2) Microdolomite was present in the studied stromatoporoids which is an important indicator of precursor high-magnesian calcite (Lohmann and Meyers, 1977); 3) Brachiopods from the Helderberg strata, known to be of low-magnesian calcite original mineralogy, had well-preserved skeletal ultrastructure whereas the stromatoporoids were recrystallized 45

(like Stearn had observed in 1972) and therefore, unlikely to have been composed of low-magnesian calcite; 4) Gastropods from the Helderberg strata, known to be composed of aragonite, had undergone extensive leaching and subsequent cementation by equant calcite and showed no original ultrastructure. However, the stromatoporoids, even though they had highly porous reticulate structures, were preserved as a neomorphic fabric of inclusion-rich zones in low-magnesian calcite and; 5) Microprobe analysis of the studied stromatoporoids did not show high Sr values as would be expected if the original mineralogy were aragonite. Any dissolution-precipitation in the stromatoporoid that may have occurred had to have been an in-situ, fabric retentive, thin film process (Pingitore, 1976). There has been another hypothesis regarding mineralogy of marine invertebrates. As first introduced by Sandberg (1983), there is evidence that seawater chemistry has oscillated through geologic time between aragonitic seas and calcitic seas. The driver of these oscillations is not of relevance here. The important point is that a cladistic study by Porter (2010) has provided data that indicate that seawater chemistry has significant influence on carbonate skeletal mineralogy mainly at the time the mineralized skeleton first evolves. Based on the first appearance of carbonate-mineralizing clades, Porter (2010) indicates that tabulate corals, rugose corals, ostracodes, and stenolaemate bryozoans all evolved during calcite seas and therefore had original mineralogies of calcite. Porter gives two reasons for not distinguishing between low-magnesian and high-magnesian calcite as other workers have (Stanley and Hardie, 1998, 1999; Zhuravlev and Wood, 2008): 1) because the magnesium content in calcite can vary continuously (and is inconsistently defined in the literature) and 2) because studies have shown (Stanley et al., 2002, 2005; Ries, 2004, 2006) that the magnesium content of calcitic skeletons can vary according to 46

the Mg/Ca ratio of seawater (where normally HMC taxa can become LMC when the Mg/Ca ratio is low)(Porter, 2010). Unfortunately, Porter excluded Stromatoporoidea (Paleozoic stromatoporoids) from his study because they may have a polyphyletic origin of calcareous skeletons (Stearn and Mah, 1987; Rush and Chafetz, 1991; Wood, 1991; Stearn et al., 1999). For purposes of this study, Table 2 includes the assumed mineralogies of the major fauna identified.

Table 2: Mineralogies of major fauna. Modified from Flugel (2004) with Porter (2010) added. (X = dominant mineralogy, x = less common mineralogy, NA = not applicable/not specified).

Porter, 2010 Arag + Ca Organism Arag LMC HMC Cal Phosphates Arag Calcite Cyanobacteria x X x NA Sponges: Stromatoporoidea x X X NA Corals: Rugosa X x X Corals: Tabulata x X x X Bryozoa x X x X x X Brachiopoda: Articulata X x X Brachiopoda: Inarticulata X NA Mollusca: Bivalvia X X X X Mollusca: Gastropoda X X x X Echinodermata X X

Cements

After analyzing core, it became obvious that the majority of the core was not composed of fauna, but rather matrix and cement. In order to determine a method for recording the amount of cement in each foot of core, it was first necessary to be able to define and identify cements in hand sample. The cores with the most unidentifiable matrix/cement were selected for thin section analysis. Several samples (42) were taken from two crest cores (Halmich 2-1 and BTK 1-36) and thin sections were made using impregnation with blue epoxy and stained with Alizarin Red S. Analysis of the thin sections revealed that most of the darker gray areas were cryptocrystalline sub to euhedral replacement dolomite (Figs. 12-15).

Figure 12: Halmich 2-1 at 3027 feet showing the core and the piece cut for thin section analysis (Facies 4 Skeletal Grainstone).

Figure 13: Halmich 2-1 core at 3027 feet showing plane light (top) and cross- polarized light (bottom) thin sections of sub to euhedral replacement dolomite. 49

Figure 14: Busch-Tubbs-Kuhlmann 1-36 at 3202 feet showing the core and the piece cut for thin section analysis (Facies 3A Stromatoporoid Wacke- Boundstone).

Figure 15: Busch-Tubbs-Kuhlmann 1-36 core at 3202 feet showing plane light (top) and cross-polarized light (bottom) thin sections of replacement dolomite.

Some fossils were identifiable as such because they consisted of subhedral to euhedral mimetic replacement dolomite (Figs. 16 and 17).

Figure 16: Busch-Tubbs-Kuhlmann 1-36 at 3047 feet showing the core and the piece cut for thin section analysis (Facies 3A Skeletal Wacke-Packstone).

Figure 17: Busch-Tubbs-Kuhlmann 1-36 core at 3047 feet showing plane light (top) and cross-polarized light (bottom) thin sections of coral with structure partially retained by subhedral to euhedral mimetic replacement dolomite. 53

Some tan and dark brown areas appeared to be bladed or botryoidal fabric destructive marine cements (Figs. 18-21).

Figure 18: Busch-Tubbs-Kuhlmann 1-36 at 3049 feet showing the core and the piece cut for thin section analysis (Facies 3A Skeletal Wacke-Packstone).

Figure 19: Busch-Tubbs-Kuhlmann 1-36 core at 3049 feet showing tan areas in plane light (top) and cross-polarized light (bottom) thin sections of bladed or botryoidal fabric destructive marine cements. 55

Figure 20: Busch-Tubbs-Kuhlmann 1-36 at 3057 feet showing the core and the piece cut for thin section analysis (Facies 3B Skeletal Wacke-Packstone).

Figure 21: Busch-Tubbs-Kuhlmann 1-36 core at 3057 feet showing dark brown area in plane light (top) and cross-polarized light (bottom) thin sections of replacement dolomite. 57

Some dark brown laminar patches have been identified by previous workers as stromatoporoids (Balogh, 1981; Gill, 1977). Gill (1977) describes a massive stromatoporoid on Plate 3 as “completely recrystallized into a brown homogeneous dolomite mass, showing only barely discernible traces of internal lamination” in hand sample and also shows a photomicrograph in plane light of “typical texture of recrystallized massive stromatoporoid” which looks very similar to Figures 22-23. Generally, shape and content of footages above and below possible stromatoporoids were used in determining whether they were recorded as stromatoporoids or simply cement. No other distinctively early marine cements (isopacous, fibrous) were detected in thin section.

Figure 22: Halmich 2-1 at 2979 feet showing the core and the piece cut for thin section analysis (Facies 3A Stromatoporoid Wacke-Packstone). 58

Figure 23: Halmich 2-1 core at 2979 feet showing dark brown area in plane light (top) and cross-polarized light (bottom) thin sections of replacement dolomite. 59

Distinguishing micrite, microcrystalline carbonate mud considered as matrix, from syndepositional cement can be very difficult, if not impossible in some instances (Friedman, 1985). Given that the cores in this study have all been dolomitized, distinguishing original micritic matrix from syndepositional cements is not possible in hand sample. Since determination of percentage of cement content is a tertiary objective, the following were recorded as cements in core hand sample: dark brown or tan aphanitic, amorphous areas.

Reservoir Characteristics

Evaluation of Porosity

In an attempt to determine the porosity characteristics in cores from differing water energy environments and differing proximities to sequence boundaries, 20 feet of core were selected for further study. Slabbed core from the reef crest, windward, and leeward margins were covered in a flour paste that was colored with food coloring. Once the paste had set in the pores, the surfaces were wiped clean and scanned to a digital image. These images were analyzed using software that determined the percentage of colored areas on the slabbed core surface to estimate moldic and vuggy porosity of the slabbed surface. Additionally, six feet of core from

the reef crest, windward, and leeward margins were subjected to CT scanning. By color coding the void areas in the rock, the CT scans show the degree of interconnectedness of the molds and vugs in three dimensions.

Procedure

Each core slab was wetted with water, scanned using a desktop flat-bed scanner (HP scanjet 7400c), and saved as a .jpeg file. The core slab was then 60

examined using a hand lens and/or low power binocular microscope. Skeletal fragments or molds were assigned to the following phyla/categories: Stromatolite (including cyanobacterial mats), stromatoporoid, tabulate coral, rugose coral, crinoid, brachiopod/gastropod, bryozoan, unidentified, and cement. Each fossil category was assigned a color code (Figure 24). Identified fossil fragments ~4mm in size or larger were color-filled on the .tiff images using Microsoft Paint software or Adobe Illustrator (Figure 25). Growth forms, when detectable, were noted in a spreadsheet as were fossils that were found in situ. Identification of tabulate corals to suborder (e.g. Favositina, Auloporina, Syringoporina, Halysitina, Heliolitina, and genus Thamnopora) and rugose corals to species (e.g. Fletcheria), when possible, was noted. Percentage of core coverage of skeletal fragments <4mm in size were evaluated using visual estimate charts (Baccelle and Bosellini, 1965) and entered into the spreadsheet. Color-filled images were analyzed using the image analysis program Image-

Pro Plus. The relative abundance (e.g. the percentage of total foot of core area covered by fauna and cement) of each fossil category was calculated by the image analysis program (Figure 25). The program also recorded size data for each component (e.g. maximum width, maximum length, minimum width, minimum length, etc.). Calculations were made from the spreadsheets for relative abundance, framework density, and reef-builder diversity by facies and entire cores. Composition of reef-building assemblages was determined using the data captured describing the morphologies expressed, the dominant taxa, and assemblage zonations of in-growth position fauna in various hydraulic energy settings of the reef along third order sequence boundaries and were placed on previously interpreted sequence 61

boundary maps (Wold, 2008). Cyanobacterial mats/ Stromatolite Stromatoporoid Tabulate Coral Rugose Coral Crinoid Brachiopod/Gastropod Bryozoan Unidentified Cement

Figure 24: Color code for fossil identification in core slab images.

Figure 25: Example of color-filled fossils on scanned .tiff image (left side) and Image-Pro Plus count of each fossil and corresponding percent of the slab occupied (right side).

Limitations of this Study

There were several issues which hindered the approach and effected the results of this study: 1) all of the cores in this study have been dolomitized; 2) fossils have different skeletal mineralogies and therefore different preservation potentials; 3) no outcrop is available for study, only four-inch subsurface slabbed drill cores; 4) and the use of findings from studies of the modern as an analog to the ancient is problematic.

Dolomitization

All of the cores for Ray Reef are known to be dolomitized. This presented problems in fossil identification. By limiting fossil identification to broad categories (phyla), most problems with misidentification were eliminated. However, the inability to distinguish fossils from matrix due to complete destructive diagenesis was unavoidable. This probably caused the faunal abundance and distribution numbers to be inaccurately low. In addition, variations in faunal skeleton mineralogy (i.e. preferential dissolution/replacement of originally aragonitic skeletal components) also may have induced inaccuracies due to differences in preservation potential. However, these are issues that are inherent to Paleozoic studies and could not be eliminated.

Limitations with Core Data

Unlike a study involving outcrop, this study utilized slabbed subsurface cores. Since the cores are four inches in diameter, they provided a severely limited, one dimensional, vertical representation of the strata. This limitation rendered morphological classification of some fossils inaccurate or impossible. There are 63

several cores from the same reef. However, they are widely spaced (i.e. within approximately .25 – 1.0 kilometer of each other). Since carbonates show a high degree of heterogeneity, the sequence stratigraphic approach of looking at changes in packages of facies that are indicative of the environments in which they were deposited were required to make interpretations from core to core across the reef (Qualman, 2009, Ritter, 2008; Wold, 2008;). In addition, the line transect method used in this study is usually employed on outcrops where bedding planes are used as time-correlative surfaces. Because this study only used subsurface cores, previously determined third order sequence stratigraphic boundaries were used as a time-correlative surface. Because a previous study (Ritter, 2008) has shown that there is more dissolution along third order sequence boundaries due to exposure, the fauna exposed at these surfaces also negatively impacted the relative abundance and distribution results. Also, fauna recorded between sequence boundaries were used to interpret community succession and provide information on hydraulic energy as interpreted from faunal morphology. However, these areas are known to be “time-averaged” (Perrin et al., 1995) and could not be used in determining true reef zonation.

Limitations of Analogs

The use of modern analogs has inherent limitations. These include differences between modern and ancient climates, tectonic settings, water circulation patterns, sea level changes (both amplitude and frequency), the evolution of biota, and both the thickness and diagenesis of strata (Klovan, 1974; Grammer et al., 2001, 2004). There is also the uncertainty of whether genetics or the environment had more control on coral and stromatoporoid morphology. For the purposes of this study, it was assumed 64

that wave energy was the primary reason for variations in growth forms and that those species with strong genetic controls only thrived in limited environments (Sandstrom and Kershaw, 2008).

CHAPTER V: RESULTS AND DISCUSSION

There are sixteen sub-surface cores available for study from Ray Reef which are housed at the Michigan Repository for Research and Education. Wold (2008) chose eight of these cores for description and use in determining stratigraphic sequences due to their quality and continuity of core footage. This study incorporated these previous descriptions, facies determinations, and sequence stratigraphic boundaries and focused upon further examination of six of the eight cores to determine relative faunal abundance, framework density, diversity, and general distribution throughout Ray Reef (Table 3). Four parameters are used in this study to characterize the abundance and distribution of reef fauna: 1) relative abundance, 2) framework density, 3) reef- builder diversity, and 4) composition of reef-building assemblages. These parameters were studied on fauna grouped into the following categories: 1) cyanobacteria (mats or stromatolites), 2) stromatoporoids, 3) tabulate corals, 4) rugose corals, 5) bryozoans, 6) crinoids, 7) brachiopods, and 8) unidentifiable fauna. The unidentifiable fauna are so labeled because they still retain enough of their original shape, size, or texture to be recognized as skeletal clasts or grains, but have been diagenetically altered to the point that they cannot be placed into one of the above mentioned categories.

Table 3: Comparison of Cores in Ray Reef

Core Length S Faunal Core In Well Name (ft) B Relative Abundance Density Density Cement situ Debris Leeward Stromatop 1.43%, Unid 0.35%, 3198-3252 4 Stromatop 54%, Unid 39%, Tab 0.04%, Bryz 0.01%, Percy 2-2 (54.5) 3 Tab 3%, Bryz 3%, Crin 1% Crin 0.002% 1.82% 16% 16% 84% Brach 30%, Bryz 26%, Cyano 1.30%, Stromatop 0.81%, 4 Tab 12%, Unid 10%, Tab 0.79%, Crin 0.54%, 2934-3251 3 Crin10%, Stromatop 4%, Bryz 0.45%, Brach 0.30%, Jacob 1-36 (288) 2 Cyano 4%, Rugose 4% Rugose 0.17%, Unid 0.09% 4.44% 21% 39% 61% Crest

67 Unid 29%, Bryz 26%, Unid 3.88%, Stromatop 0.80%, 4 Crin 22%, Stromatop 12%, Cyano 0.56%, Tab 0.42%, 2923-3219 3 Tab 4%, Cyano 4%, Bryz 0.41%, Crin 0.35%, Halmich 2-1 (294) 2 Rugose 1%, Brach 1% Rugose 0.05%, Brach 0.03% 6.51% 19% 16% 84% Bryz 40%, Crin 19%, Stromatop 4.7%, Crin 1.8%, Brach 13.2%, Tab 12.7%, Tab 1.9%, Bryz 0.66%, 2952-3264 3 Unid 5%, Stromatop 5.6%, Unid 0.55%, Rugose 0.49%, BTK 1-36 (311) 2 Rugose 4%, Cyano 0.12% Cyano 0.35%, Brach 0.11% 10.58% 24% 16% 84% Windward 4 2979-3241 3 Lask4 (220) 2 Unid 53%, Brach 26% Cyano 1.24%, Unid .43% 2.40% 22% 32% 68% Brach 62%, Cyano 19%, Crin 3190-3250 3 10%, Unid 6%, Cyano 2.17%, Brach 0.05%, Lask5 (50) 2 Tab 3% Unid, Tab, Crin <0.05 2.29% 29% 20% 80% Averages: 4.67% 22% 23% 77%

Relative Abundance

The Percy core (leeward margin) displays dominant relative abundances of stromatoporoids and other unidentifiable fauna. The Jacob core (crest to leeward margin) shows dominant relative abundances of brachiopods and bryozoans (Table 3 and Figure 26). The crest cores show dominant relative abundances of bryozoans, crinoids, and other unidentifiable fauna in the Halmich core, and bryozoans and crinoids in the Busch-Tubbs-Kuhlman (BTK) core (Table 3 and Figure 26). The windward cores display dominant relative abundances of brachiopods and unidentifiable fauna in the Laskowski 4-1 core, and brachiopods in the Laskowski 5-1 core (Table 3 and Figure 26). Because this study captures data for faunas spanning a wide range of sizes, relative abundance does not necessarily indicate which fauna actually make up most of the reef. Framework density is a much more indicative measure of reef composition. It expresses the percentage of surface area which fauna occupy. However, relative abundance numbers do indicate that, among the smaller sized fauna, brachiopods are more abundant on the windward side of the reef while bryozoans and crinoids are more abundant on the crest.

Relative Abundance of Fauna Across Wells in Ray Reef

20 Relative Abundance (%)

0 Lask5 Lask4 BTK Hal Jacob Percy

Unid Stromatoporoid Tabulate Rugose Bryozoan Crinoid Brachiopod

Figure 26: Relative abundance of fauna across wells in Ray Reef. Relative abundance is the percentage of each fauna when the sum of all fauna equals one hundred percent. Laskowski 5 (Lask5) and Laskowski 4 (Lask4) wells are on the windward side of the reef. The Halmich (Hal) and Busch-Tubbs-Kuhlman (BTK) wells are on the reef crest. The Jacob and Percy wells are on the leeward side of the reef. Refer to Figure 11 for well locations. (unid = unidentifiable).

Framework Density

Attempting to develope a new quantitative method to determine ancient reef zonation, Perrin (1995) defined framework density using four quantitative parameters: 1) reef-building fauna preserved in growth position, 2) sediment, 3) cement, and 4) primary porosity. This study was not able to use this definition for several reasons. This study, like others, shows that the majority of the reef is composed of debris and not fauna in growth position (Friedman, 1985; James, 1983). Because density is closely dependent upon abundance, (the number of individuals or 69

colonies), size, and morphologies of the reef builders (Perrin et al., 1995), all fauna were included in calculations of density, regardless if they were in growth position or not. Fauna size was captured by image analysis software and perimeter measurements were analyzed as discussed below. Fauna morphology and specimens found in situ were noted. In regards to amount of sediment and primary porosity, the cores from Ray Reef are all dolomitized making it very difficult to distinguish original micritic sediment from micritic cement (Friedman, 1985). Diagenesis, especially dolomitization, has also altered primary porosity and original cementation. Framework density, as a result, is calculated in this study as the percentage of subsurface slabbed core that is covered by fauna when the total slabbed core surface area equals one hundred percent. One example would be the following, one foot of slabbed core displays densities of: stromatoporoid 10%, unidentified fauna 10%, tabulate coral 5%, rugose coral 5%, bryozoan 2%, and crinoid 2%. Total faunal coverage would equal 34% with the remaining 66% of the coverage consisting of undistinguished matrix, cement, and pore space. The sum of all fauna and non-fauna equals 100% coverage of the slabbed surface of the core. The general trend, in modern coral reefs, shows density of reef-builders initially increasing with water depth on the upper part of the reef slope and then decreasing with water depth (Wells, 1957; Liddell and Ohlhorst, 1988). On the reef flat, density increases to the reef crest where corals may be replaced by coralline algae (Tracey et al., 1948; Wells, 1957; Chevalier and Beauvais, 1987; Hubbard et al., 1990) and on the deep slopes, density decreases quickly as scleractinian corals are replaced by other fauna such as coralline algae (Minnery et al., 1985; Minnery, 1990), sclerosponges (Land and Moore, 1977; Liddell and Ohlhorst, 1988), encrusting foraminifera (Reiss and Hottinger, 1984; Perrin, 1989, 1990, 1992), or by sediment. 70

Below certain depths, colonies may decrease in size and change morphologies to more delicate foliaceous or platy shapes. This decreases their framework density (Perrin et al., 1995). Highest framework density in Ray Reef occurs in cores that are interpreted as being located on the reef flat to reef crest. Total framework density is 6.5% for the Halmich 2-1 (crest) core and 10.6% for the Busch-Tubbs-Kuhlman 1-36 (crest) core (Table 3 and Figure 27). Both windward cores and one leeward core (Percy 2-2 = 1.82% total density) have the lowest framework densities. The Laskowski 4-1 (windward margin) core has a total framework density of 2.4% and the Laskowski 5- 1 (windward margin) core has 2.3% (Table 3 and Figure 27). The Jacob 1-36 (crest to leeward margin) core has a medium range of framework density at 4.44% (Table 3 and Figure 27). Although these percentages of framework density seem to be very low, they are similar to densities of framework fauna found in other reefs (Friedman, 1985). Coral fragments comprise only 2%-15% of the total debris contiguous to the Great Barrier Reef (Bennett, 1971). Reefs are comprised mostly of mud and debris, not in situ fossils (Friedman, 1985). Findings in this study confirm that most of the reef is composed of matrix and cement, with lesser amounts of skeletal grains and pore space. The leeward and crest cores all have stromatoporoids as either the number one or number two contributor of framework density ranging from 0.80% to 4.7% (see Table 4 and Figure 32; Percy (leeward margin) = stromatoporoid 1.43%, unidentifiable fauna 0.35%; Jacob (crest to leeward margin) = stromatoporoid 0.81%, tabulate corals 0.79%; Halmich (crest) = unidentifiable fauna 3.88%, stromatoporoid 0.80%; BTK (crest) = stromatoporoid 4.7%, crinoid 1.8%). This indicates that the energy level of the water was high enough to provide sufficient oxygen and nutrient 71

levels but not so energetic as to inhibit stromatoporoid growth. Windward cores, in contrast, did not display stromatoporoids as either dominant in relative abundance or framework density. The the Laskowski 4-1 (windward margin) core shows unidentifiable fauna of 0.43%. The Laskowski 5-1 (windward margin) core shows brachiopods of 0.05% and unidentifiable fauna, tabulate corals, and crinoids each with less than 0.05% (see Table 3 and Figure 27). The Laskowski 4-1 (windward) core is interpreted as being located on the forereef slope at a water depth shallow enough to be in rough water; thereby causing lower densities and a lack of stromatoporoids. The Laskowski 5-1 (windward margin) core is interpreted to be in water deeper than the Laskowski 4-1. Here, most fauna are found as rubble, debris or molds (e.g. brachiopods). This may be due to the increased energy on the windward margin breaking down fossils, followed by dissolution and recrystallization rendering the fauna unidentifiable. Additionally, increased water energy on the windward margin would winnow finer-grained material away and increase precipitation of cements. Later dissolution of these cements and other skeletal grains would produce moldic and vuggy secondary porosity. This also makes identification of fauna more difficult.

Density of Fauna Across Wells in Ray Reef

5 4.5 4 3.5 3 2.5 2 Density (%) 1.5 1 0.5 0 Lask5 Lask4 BTK Halmich Jacob Percy

Unid Stromatoporoid Tabulate Rugose Bryozoan Crinoid Brachiopod

Figure 27: Density of fauna across wells in Ray Reef. Density of fauna is the percentage of the core that is covered by each category of fauna when the total slabbed core surface equals one hundred percent. Highest densities are found in the crest cores (BTK and Halmich). Laskowski 5 (Lask5) and Laskowski 4 (Lask4) wells are on the windward side of the reef. The Halmich (Hal) and Busch-Tubbs-Kuhlman (BTK) wells are on the reef crest. The Jacob and Percy wells are on the leeward side of the reef. Refer to Figure 11 for well locations. (unid = unidentifiable).

Diversity

Diversity, as expressed in this study, refers only to taxonomic richness, e.g. facies with greater numbers of different phyla present (or greater number of families of tabulate corals) are considered more diverse than facies with fewer numbers of different phyla present. No complex calculations such as the Shannon-Weaver index of diversity (Hammer et al., 2001) were conducted. Chappell (1980) created theoretical curves to account for the lateral and vertical diversity of corals caused by the interaction of biotic and physical factors

such as light, hydrodynamics, sediment influx, and subaerial exposure. Modern coral reefs display a general trend in diversity on the fore-reef that gradually increases in diversity from shallow water to wave-base. Further down slope, diversity decreases with deeper water due to increases in sediment influx as well as a reduction in light intensity. On the reef flat, diversity increases with water coverage and less subaerial exposure but decreases toward the reef front where wave energy is highest. In the back reef area, diversity increases with shallow water and lower water energy and less sediment, reaches a point where it remains constant, and then decreases with depth as light intensity is reduced (Chappell, 1980). Diversity in Ray Reef is lowest in the reef facies observed in the deeper leeward Percy core, with only halysitid and possible alveolitid tabulate corals, and the reef facies observed in the deeper windward Laskowski 5 core, with only thamnoporid and auloporid tabulate corals (Figure 33). The Laskowski 4 windward core has greater numbers of phyla and also has more diverse tabulate corals including favositid, thamnoporid, halysitid, and auloporid specimens as well as the colonial rugose coral Flethcheria sp (Figure 28). This is consistent with a shallower forereef interpretation. The Jacob 1-36 (crest to leeward margin) core has several instances where 7 of 8 possible phyla are present in the reef facies and favositid, thamnoporid, halysitid, and auloporid tabulate corals are present (Figure 28). This is consistent with a reef flat to back reef interpretation. The Halmich 2-1 (crest) and BTK 1-36 (crest) cores are the most diverse with several instances of 5-8 phyla represented in the reef facies, including all the previously listed types of tabulate corals (Figure 28). This is consistent with a reef flat or crest interpretation.

Diversity Across Ray Reef by Well and Facies

8 7 6 5 4 3 2 1 0

Number of Phyla Present (Max = 8) Lask5 Lask4 BTK Halmich Jacob Percy

Exp FS 5-Restriced 4-Skel Grnstn 3A-Reef Core 3B-Reef Debris 2-Bioherm

Figure 28: Diversity by facies across wells in Ray Reef. Diversity is expressed as the number of phyla represented with a maximum of eight possible. Generally, crest cores show the highest diversity in the Bioherm and Reef Core Facies with the more marginal windward core (Lask4) with similar values and the crest to leeward (Jacob) core showing similar values in the Reef Core Facies and the Reef Debris and Skeletal Grainstone Facies. The lowest diversities were in the deeper windward foreslope Lask 5 and deeper leeward Percy cores. Laskowski 5 (Lask5) and Laskowski 4 (Lask4) wells are on the windward side of the reef. The Halmich (Hal) and Busch- Tubbs-Kuhlman (BTK) wells are on the reef crest. The Jacob and Percy wells are on the leeward side of the reef. Not all facies are present in all wells. Refer to Figure 11 for well locations. Exp = exposure; FS = flooding surface.

Distribution and Composition of Reef-Building Assemblages

This study uses a combination of faunal identification, abundance and dominance, morphology, and hydraulic energy settings to determine the vertical change or community replacement in six subsurface cores located throughout the reef. Faunal dominance is expressed as fauna with greater than 20 percent relative abundance. It is generally accepted that ecological succession is expressed as increases in

species diversity, biomass, structural complexity, and stability through time (James and Bourque, 1992). Biomass has also been shown to increase with shallowing upward water conditions (Riding, 1981). This study used the average perimeter of fauna as an indicator of biomass which was analyzed using spindle diagrams (Hammer et al., 2001), correlated to previously interpreted third order sequence boundaries and high frequency sequence boundaries (Wold, 2008) to evaluate biomass changes within shallowing upward sequences that could indicate community replacement. Although Stearn (1982) argued that modern corals show no general morphologic patterns and should not be used as indicators of ancient environments, there are many published articles that argue that morphology is indicative of environmental conditions. This study used the findings of workers who have used modern coral reefs as models to interpret ancient reefs (Gischler, 1995; James, 1983; James and Bourque, 1992; Klovan, 1974).

Distribution and Community Replacement vs. Succession

The definition and determination of ecological succession in Paleozoic reefs has been a matter of controversy since the 1970’s. One of the main disputes centers around whether succession is interpreted as autogenic, i.e. changes caused by the biota within the system, which is usually the preferred definition of biologists, or allogenic, i.e. changes caused by external forces outside the system such as sea level change, which is usually favored by geologists in making their interpretations (Copper, 1988). Some workers have suggested using the term “community replacement” as was done by Johnson (1977) and Rollins et al. (1979) when succession of organisms 76

is thought to be due to external forces such as climate or sea level change (Copper, 1988). Other biologists have used the term “colonization sequence” (Gray, 1981) in order to avoid the term “succession” and its implications (Copper, 1988). The intention of this study is not to investigate ecological succession theory; but rather, to provide additional evidence to previous studies (Ritter, 2008; Wold, 2008; Qualman, 2009) which have used sequence stratigraphy to improve the model used in these pinnacle reefs to show their lateral and vertical heterogeneity. This study seeks to show that the changes in community replacement are repeatedly seen throughout the main sequences of reef growth in this Wenlock pinnacle reef complex and that this affects the heterogeneity of these reefs and their reservoir characteristics. Because sequence stratigraphy was used to determine third order sequence boundaries, changes seen in the reef community at this level may be considered allogenic. These changes will be referred to as “community replacement” as reflected in shallowing upward sequences which coincide with eustatic sea level changes. This is not a new method or interpretation, but a combination of newer (sequence stratigraphic) methods with older interpretations (Klovan, 1974; James 1983; James and Bourque, 1992; Gischler, 1995). Riding (1981) in describing the sediment, biota, size and geometry of four different types of bioherms and biostromes in the Silurian of Northern Europe, concluded that the different types of reefs were “stages in the response of reef building organisms to progressively shallower and more turbulent conditions.” Higher frequency fourth order sequence boundaries may be autogenic and due to “true succession” caused by the organisms themselves, or they may simply be “community replacements” due solely to external forcings. This paper will not attempt to differentiate causes, but will use the term “community replacement” for all observed changes. 77

Additionally, this study incorporates the trends of increasing diversity and biomass (as interpreted from perimeter measurements) as indicators of community replacement. As an aside, these are typically among the attributes used in determining ecological succession (Chappell, 1980; Copper, 1988; James and Bourque, 1992; Perrin 1995; Scrutton 1999).

Community Replacement

Community replacement in a shallowing upward sequence is best visualized by plotting the average perimeter of fauna on the x-axis and the core depth in feet on the y-axis in a spindle diagram. Figure 29 of the Busch-Tubbs-Kuhlman (BTK) (crest) core shows a general relationship between increasing stromatoporoid and tabulate coral perimeter (or biomass) with shallowing upward sequences marked by third order sequence boundaries and high frequency sequences. This is seen throughout the cores across the reef. When analyzed in sequences, the pattern of reef growth becomes more apparent and is in stark contrast to the “bucket models” of the 1970’s and 1980’s that imply 300-600 ft of uninterrupted reef growth.

n te a la d m u zo h b o c Unid Stromtro Tabulate Rug Bryz Crin Brach Unid S Ta Rugose Bry Crinoi Bra -2960 -2980 2990 HFSB -3000

-3020

-3040 3058 HFSB -3060

-3080

79 3100 -3100 SB3

-3120 CoreCore Depth Depth (ft.)(ft.) 3128 HFSB

-3140

-3160 3175 SB2 -3180 3189 HFSB -3200 3204 HFSB

-3220

-3240

-3260 3264 HFSB 120 240 360 480 600 720 840 960 1080 Average Perimeter (mm) Figure 29: Busch-Tubbs-Kuhlmann (BTK) core showing average perimeter of fauna in millimeters (x-axis) with core depth in feet (y- axis). High Frequency Sequence Boundaries (HFSB) are marked across faunal categories with dashed lines and their corresponding core depth is noted on the left. Third order Sequence Boundaries (SB) are marked across faunal categories with solid lines and their corresponding core depth is noted on the left. Note the increase in faunal perimeter, especially in framebuilding stromatoporoids (Strom) and tabulate corals, coincident with sequence boundaries. This is suggestive of biomass increasing with shallowing upward sequences which indicates community replacement.

Cementation

Syndepositional cementation was expected to be highest in the windward cores based upon previous work (e.g. Grammer et al., 1993a), and this was found to be true in this study. The Laskowski 4-1 (windward margin) core contains 28.12% cement. However, the windward Laskowski 5-1 core only contains 15.8% cement which is just slightly higher than the cores from the leeward side with the Percy 2-2 (leeward margin) at 12.20% and the Jacob 1-36 (crest to leeward margin) at 13.63% (see Table 4). The percentage of cement is lowest in the leeward Percy 2-2 core at 12.20%. The crest Halmich 2-1 core has 24.74% and the crest BTK 1-36 core has 21.02% cement (Table 3). Based upon the presence of moldic and vuggy porosity observed in the core, it is interpreted that secondary dissolution of some cements in the windward cores has occurred. Therefore, the original amount of syndepositional cementation of these cores cannot be known but is presumed to be greater than the amounts estimated in this study.

Comparisons with Ancient Analogs

Generally, the community succession put forth by Klovan (1974) when working on the Western Canadian Devonian reefs is the closest to what is observed in Ray Reef. As Klovan suggested, the Thamnoporid-Disphyllid-Alveolites community was observed in lower energy settings below storm wavebase. Small rugose corals could be added to this community for Ray Reef in the Silurian of the Michigan Basin southern pinnacle belt trend. Intermediate energy settings contain a tabular stromatoporoid community which was interpreted by Klovan to be analogous to the modern Diploria-Montastrea-Porites community located between fair weather and 80

storm wavebases. Rugose corals and tabulate corals with similar domal-multilobate- branching forms also occur within this community at Ray Reef. The highest energy settings in Klovan’s model included the massive stromatoporoid community located between sea level and wavebase. In this study, domal to hemispherical stromatoporoids are included in the higher energy massive stromatoporoid community with specimens displaying ragged non-enveloping forms interpreted as occurring in higher energy settings than smooth enveloping forms. James and Bourque (1992) described reef facies and water depth differently. They considered the Reef Front Facies to comprise water depths between 10 m (the base of surface wave action) and 100 m with the Reef Crest Facies to a depth of 15 meters at most. This is different from the Klovan model with the highest energy in the 3-9 meter range (10-30 ft.) corresponding to just below sea level to wave base, the intermediate energy in the 9-21 meter range (30-70 ft.) corresponding to wave base to storm wave base range, and the lowest energy from 21-24 meters (70-85 ft.) considered below storm wave base. James and Bourque (1992) also differentiated stromatoporoid forms and energy settings by placing encrusting or large non-enveloped, ragged margin (i.e. massive) stromatoporoids in the high energy reef crest facies and the totally enveloped smooth stromatoporoids in quiet water below wave base or in sheltered areas in the back reef with domal, bulbous, and dendroid forms. Domal stromatoporoids were also observed in this study. Ragged, non-enveloped stromatoporoids are interpreted as occurring in higher energy settings than stromatoporoids that had smooth and enveloped forms occur. The BTK (crest) core contains a colonial rugose coral Fletcheria sp. just above a HFSB between 3053’-3056’ and above SB3 along with thamnoporids, rugose 81

corals, encrusting stromatoporoids and bryozoans. Gischler (1995) noted very similar fauna in the leeward forereef where a possible channel connected a lagoon to the open ocean in a Devonian atoll. Gischler assigned it to a quiet, low energy environment. The BTK (crest) core is interpreted as being on the crest to leeward side of the reef in a similar environment as that described by Gischler and would be consistent with a “leeward forereef” interpretation. Schneider and Ausich (2002) compared the diversity of fauna in a patch reef, located in a southwestern Ohio quarry of Early Silurian age, in the Brassfield Formation to the Jupiter Formation of Quebec. Findings on Ray Reef compared to Schneider and Ausich (2002) are in agreement that stromatoporoids are more abundant on the leeward side than the windward side. In the Ray Reef, however, stromatoporoids were most abundant in the cores from the reef crest. Also, Schneider and Ausich (2002) found solitary and colonial rugose corals more abundant on the windward side. In Ray Reef, no rugose corals were readily identifiable on the windward side, although this may be due to secondary diagenesis as previously discussed. Identifiable rugose corals in Ray Reef were found more frequently in lower energy settings and gradually increased in size and decreased in abundance as sequences shallowed upward toward sequence boundaries. Schneider and Ausich found that tabulate corals, crinoids, and bryozoans were evenly distributed across the reef. In Ray Reef, bryozoans and crinoids were most abundant in the reef crest cores. Crinoids and bryozoans were sparse in the windward cores. Tabulate corals were more abundant as thamnoporids in lower energy settings and were replaced by favositids with increasing energy, as reported by Klovan (1974). The larger favositids were found in the higher energy settings but were not found with the highest energy (ragged domal, non-enveloped) stromatoporoids. 82

Modern Analog – Tongue of the Ocean (TOTO), Bahamas

The Niagaran reef and slopes of the Michigan Basin during Silurian time were similar in some ways to the margins and upper slopes of the intraplatform basins in the Bahamas. Variations in composition and make up of marginal deposits as well as upper slope deposits in response to windward and leeward positioning suggest that many of the same processes may be operating in each environment. In addition, the modern day Bahamas are located in a subtropical setting affected by easterly trade winds similar to the Silurian reefs in the Michigan Basin as discussed previously. Grammer et al. (1993a) have shown that several characteristics of the margin and upper slope environment such as slope geometry, facies and faunal distribution and relative amounts of cementation, in the Tongue of the Ocean (TOTO), Bahamas, were influenced by windward or leeward orientation of the margin.

Similarities between TOTO, Bahamas and the Silurian Michigan Basin Reefs and Margins

In a previous study on Ray Reef, Wold (2008) concluded that there were a number of attributes similar to the findings of Grammer et al. (1993a) in the Tongue of the Ocean, Bahamas. Specifically, both showed steeper windward margins with abrupt changes in facies and more gently grading leeward margins characterized by more gradual changes in facies. Wold also found, as Grammer et al. (1993a) had documented, that the windward margin with its predominantly skeletal grainstones had higher porosity and permeability values compared to the nonskeletal grainstones of the leeward margin (Figure 30). In this study of relative abundance and general distribution of fauna in Ray Reef, there are general similarities with findings in the Bahamas (Grammer et al.,

1993a) even though the specific fauna are different. Studies conducted by Grammer et al., 1993a determined that faunal abundance and diversity were greater near the top of the wall (50-75 meter water depth) and decreased with depth in the Tongue of the Ocean. Ray Reef displays a similar trend with faunal abundance and diversity increasing upsection in what have been interpreted as high frequency shallowing upward cycles (this study, Wold (2008) and Ritter (2008)). Similarities are also observed in the increased amount of syndepositional cement found in the windward forereef slope of Ray Reef and Tongue of the Ocean (Grammer et al., 1993a). Grammer et al. (1993b, 1999) documented the rapid growth rates of cements (8-10 mm/100 years) indicating rapid cementation rates (10s-100s of years) of the slope deposits. This allowed slopes to retain the high angles of declivity. Grammer et al. (1993) found pore-filling botryoidal cement in the coarse skeletal packstones and grainstones of the interior of the marginal (“cemented”) slope fronting the TOTO, Bahamas. The windward Laskowski 4 core in Ray Reef similarly displays higher amounts of syndepositional cement, including botryoidal cements, as well as syndepositional vertical fractures (i.e. neptunian dikes) which are also common on the surface of cemented slopes in Tongue of the Ocean, Bahamas (Grammer et al. 1993a).

Reservoir Characteristics

all wells across Ray Reef shows the highest values in the windward Lask4 core and the lowest values in the windward Lask5 core (Figure 30). This would appear at first glance to indicate that there is no relationship between windward or leeward positions on a reef and reservoir characteristics of porosity and permeability. However, when other aspects such as sediment texture, reef morphology, and diagenesis are taken into consideration, these apparent contradictory findings can be explained.

Windward vs. Leeward Reef Core Facies 3a Average

80 70 Lask 5 60 50 Lask4 40 Halmich 30 BTK 20 Jacob

Permeability (mD) Permeability 10 0 024681012

Porosity (%)

Figure 30: Cross-plot of average values for permeability and porosity in the Reef Core Facies (3a) for five cores across Ray Reef. The Laskowski 4 core, interpreted as being in a windward forereef position, shows the highest values. The lowest values are in the Halmich (crest), BTK (crest), and Lask 5 (windward) cores. The Jacob (crest to leeward) core has intermediate values. Whole core analysis was not available for the leeward Percy core.

sequence boundaries due to porosity occlusion resulting from early cementation. Using 3rd order sequence boundaries identified by Wold (2008), analysis in this study shows that the three 3rd order sequence boundaries do not always show the same trends. The windward Laskowski 4, the crest BTK, and the crest Halmich cores show that there is a general trend in porosity and permeability values increasing from the transgressive phase to the regressive phase in the first sequence up to SB2 (Figure 31a, 31b and 31c). In the second sequence, between SB2 and SB3 porosity and permeability values again increase from the transgressive to the regressive phase (Figure 31a, 31b and 31c). In contrast, the third sequence from SB3 to SB4 shows the porosity and permeability values either remain about the same or decrease from the last transgressive phase to the regressive phase (Figure 31a, 31b and 31c). Also, the porosity and permeability values of the transgressive phase increase substantially from Sequence 1 to Sequence 2 to Sequence 3 (e.g. the Lask4 values for the transgressive phase of Sequence 1 are ~8 mD/6%, Sequence 2 increases to 75mD/11%, and Sequence 3 increases to 100 mD/13%) in the Lask4 windward and BTK crest cores. In the Halmich crest core the transgressive phase values increase from Sequence 1 to Sequence 2 but increase only slightly to Sequence 3. However, the results for the Jacob (crest to leeward) core (Figure 38d) are different. Although the Jacob (crest to leeward) core shows an increase in the porosity/permeability values from the transgressive phase to the regressive phase during the first sequence up to SB2, as was seen in the Lask4, BTK, and Halmich cores, in the second sequence from the transgressive phase to the regressive phase between SB2 and SB3, permeability values decrease, in contrast to what is observed in the windward and crest cores. The cause for this decrease is unknown, but may be due to this area of the reef transitioning from a crest position and exposure to a more 86

leeward position, as will be explained in the next section. The transition to more mud-rich sediments with decreased fauna would decrease the original porosity/permeability values and seal those sediments from secondary dissolution enhancement. a)

Windward Lask 4 Reef Core Facies 3a 3rd Order Sequence Averages R3001-3052 Sequence 3 1000 T3052-3067 SB3

R3067-3143 Sequence 3 100 Sequence 2 Sequence 1 T3143-3169 SB2 Sequence 2 R3169-3212 10 Sequence 1 T3212-3215 Facies 2 Permeability (mD) Permeability 1 R2979-2994 Facies 5 0 5 10 15 R2995-3001 Facies 4 Porosity (%) b)

Crest BTK Reef Core Facies 3a 3rd Order Sequence Averages T2980-2989

R2990-3072 (exp) 100 Sequence 3 T3072-3100 SB3

Sequence 3 R3100-3161 Sequence 2 10 Sequence 2 T3161-3174 SB2

Sequence 1 R3174-3220 Sequence 1

Permeability (mD) Permeability T3220-3264 Facies 2 1 2952-2974 Facies 5 0246810 Porosity (%) 2975-2980 Facies 3a

Crest Halmich Reef Core Facies 3a 3rd Order Sequence Averages R2934-3018 Sequence 3 100 T3019-3027 SB3

R3029-3108 Sequence 2 Sequence 2 T3109-3142 SB2 10 R3143-3204 (F2 & F3) Sequence 3 Sequence 1 Sequence 1 Permeability (mD) Permeability T3205-3218 (F2) 1 0246810 Porosity (%)

Crest to Leeward Jacob Reef Core Facies 3a 3rd Order Sequence Averages R2935-2992 (F5&4)

R2992-3001 (F3a) 100 Sequence 3 R3001-3020 (F3b) Sequence 2 Sequence 3 T3020-3052 SB3 Sequence 1 10 R3052-3124 Sequence 2 T3124-3160 SB2 Sequence 3 Permeability (mD) Permeability R3160-3220 1 Sequence 1 051015T3220-3251 Porosity (%)

Figure 31: Cross-plot of average values for permeability and porosity during the transgressive and regressive phases of the three 3rd order sequences across Ray Reef. Most all of the sequences, except for the Jacob sequence 2, show increases in porosity and permeability going up in sequence and from the transgressive leg to the regressive leg (except for sequence 3). Note that Sequence 3 on the Jacob core is broken out between the regressive phase Reef Debris Facies (F3b – hollow triangle) and regressive phase Reef Core Facies (F3a – filled triangle) in order to show that values increased in the Reef Debris Facies part of the sequence and then decreased in the Reef Core Facies part of the sequence. 88

To further explore these trends, it is useful to look at the facies and faunal morphology and density in each of these three cores during these three sequences.

Analysis of Core Up to Sequence Boundary 2 (SB2)

In the first sequence, the Lask4 (windward), the BTK (crest), and the Halmich (crest) cores are changing from a mud-rich bioherm facies to a reef facies (Figure 32). This accounts for the increase in porosity/permeability values from the transgressive leg to the regressive leg up to SB2. From the bottom of the cores up to SB2 (Figure 32), the Lask4 windward core has a Bioherm Facies of mostly crinoid debris and a Reef Core Facies. The Halmich (crest) core has a Bioherm Facies and a Reef Core Facies. The BTK (crest) core has a Bioherm Facies, a flooding surface with a high density of stromatoporoids, and a Reef Core Facies consisting of equal densities of stromatoporoids and crinoid debris. The BTK core also has the highest density of all the cores and a diverse representation of fauna, inferring that it is a well established and healthy part of the reef. The Jacob (crest to leeward margin) core includes a Reef Core, and Reef Debris Facies of approximately 1% or less faunal density, a Skeletal Grainstone Facies consisting of 7% bryozoans and 7% crinoid debris, and an exposure surface. From the facies and faunal density descriptions, the Lask4 (windward margin) core is interpreted as being deeper down, around fair weather wave base, on the windward foreslope. The Halmich (crest) and the BTK (crest) cores are thought to be on the reef crest to flat and closer to sea level because the Halmich core shallows to a grainstone and the BTK core shows a flooding surface. The Jacob (crest to leeward margin) is probably on the upper portion of leeward foreslope and closest to sea level as there is evidence of subaerial exposure. These interpretations support increasing 89

porosity and permeability values due to early cementation and later dissolution in the crinoid and debris rich windward Lask4 core. The shallowing of the Halmich (crest) core from a mud-rich bioherm to a skeletal grainstone would account for the increase in porosity and permeability. The change from a muddy crinoid and bryozoan rich bioherm to a reef core with equal densities of stromatoporoids and crinoids allows for increased porosity and permeability values in the BTK (crest) core. Core from the Jacob (crest to leeward) well also show an increase in the porosity/permeability values from the transgressive phase to the regressive phase during the first sequence up to SB2 (Figure 31c and 31d). However, the Jacob (crest to leeward) core is already in a reef to skeletal grainstone facies in the first sequence and experiences an exposure surface at SB2. It is thought that dissolution due to exposure greatly increases the porosity/permeability values from the first sequence up to SB2.

Figure 32: Facies, texture, faunal density, percentage of cement, percentage of porosity, and permeability (mD) below Sequence Boundary 2 for all six wells studied across Ray Reef. The Lask4-1 (windward), the Halmich (crest), and the BTK (crest) cores are transitioning from mud-rich Bioherm Facies into Reef Core Facies. The Jacob well was already in an established reef position as shown by the Reef Core, Reef Debris, and Skeletal Grainstone Facies consisting mostly of crinoid and bryozoan debris, and exposure surfaces. Since the BTK and Jacob cores are the only ones below Sequence Boundary 2 that show an exposure surface, they are interpreted to have been closer to sea level than the other cores during this sequence. 92

Analysis of Core from Sequence Boundary 2 (SB2) to Sequence Boundary 3 (SB3)

The second sequence is diagramed in Figure 33. The Lask4 (windward) and BTK (crest) cores both contain only reef facies skeletal wackestones–packstones. The presence of skeletal wackestones-packstones not sealed by finer grained sediments could be the reason for porosity/permeability increasing compared to the sequence below. During the third sequence from SB3 to SB4, the Lask4 (windward) core shallows up from reef facies, to skeletal grainstone facies, to restricted cyanobacterial mat facies. The BTK (crest) core changes from reef facies, to reef debris facies, back to reef facies, an exposure interval, reef facies, and finally a restricted cyanobacterial mat facies. The change from a reef facies to the restricted cyanobacterial mat facies and overlying anhydrite sealed and prevented the preferential dissolution of the surface during the last exposure causing the porosity/permeability values to be lower. Between SB2 and SB3 (Figure 33), the Lask4 (windward margin) core consists of only a Reef Core Facies with a very low faunal density that includes less than 1% of fauna including brachiopods, tabulate corals, and unidentified fauna. It is interpreted as being on the windward foreslope between sea level (SL) and fair weather wave base (FWWB). The BTK (reef crest) core is much more diverse including all faunal categories identified, with over 7% density of stromatoporoids, over 4% tabulates, and over 3% crinoid debris. The BTK core is also interpreted as being between SL and FWWB during this time. The Halmich (crest) core is composed of Reef Core wackestones to grainstones with a diversity of fauna. The Jacob (crest to leeward margin) core has both a Reef Core Facies of slightly more than 1% tabulates and a Skeletal Grainstone Facies with 5% crinoids and 2%

brachiopods and an exposure surface and is interpreted as being on the leeward foreslope. Porosity and permeability values increase slightly for the Lask4 (windward margin) core presumably due to secondary dissolution of syndepositional cements. The Halmich (crest) core also shows an increase in porosity/permeability values which is probably due to the change in texture to a skeletal grainstone. The BTK (crest) core shows a flooding surface at SB3 and vuggy and moldic porosity implying dissolution. However, porosity and permeability decreases in the Jacob leeward forereef core may be explained not by the low densities of fauna in the Reef Core Facies, which were similar to the previous sequence up to SB2 of around 1% of tabulates and stromatoporoids, but rather to the decrease in the density of fauna in the Skeletal Grainstone Facies (from 7% crinoids and 7% bryozoans up to SB2 and only 5% crinoids and 2% brachiopods at SB3). Additionally, below the exposure surface at SB3, leaching and salt fill is noted. Both the decrease in the skeletal grainstone facies and leaching followed by salt plugging may account for the decrease in porosity and permeability values in the Jacob core.

Figure 33: Facies, texture, faunal density, percentage of cement, percentage of porosity, and permeability (mD) between Sequence Boundary 2 and Sequence Boundary 3. Sequence Boundary 3 shows strong control over faunal density as there is an extreme paucity in fauna below SB3 in the windward Laskowski 4 and Laskowski 5 cores and to a lesser extent in the crest-leeward Jacob core. The increase in permeability in the Lask 4 core is thought to be due to dissolution of cements and secondary porosity and permeability enhancement. The Jacob (crest to leeward) and BTK (crest) cores also show possible exposure and flooding surfaces at SB3 with low poro/perm values. The Laskowski 5 (windward) core completes its reef life cycle between SB2 and SB3 with the end of reef growth at this position noted by a Restricted Facies consisting of cyanobacterial mats at SB3. The Halmich core (crest) shows a change to a Reef Debris Facies consisting of skeletal grainstones at SB3 consisting mostly of crinoids and unidentifiable debris and medium poro/perm values. 96

One of the most striking characteristics of the Laskowski 4 (windward margin) core is the visually apparent moldic and vuggy porosity (Figure 34) that is more connected than the molds and vugs of the representative Jacob (crest to leeward margin) core (Figure 35). The enhanced porosity of the windward margin core is hypothesized to be due to the lack of fine-grained sediment originally deposited due to the higher energy of the wind driven water onto the reef. The flushing of water on the windward margin would have made precipitation of cement between grains more favorable due to a constant resupply of ions and carbon dioxide outgassing. This increased cementation also accounts for the higher degree of declivity on the windward margin of the reef as seen by Grammer et al., (1993a) and interpreted by Wold (2008) on Ray Reef in comparison to the leeward margin. It is hypothesized that the preferential secondary dissolution of some of those cements may be the cause for the enhanced vuggy porosity seen in the cores at present. Since the leeward margin had more fine-grained sediments which fell out of suspension due to a decrease in water energy, there may have been less intergranular space and less favorable conditions for precipitation of cements due to the less energetic and ion depleted waters.

Figure 34: Core slab a) without pore space highlighted in black and b) same core slab showing enhanced porosity due to secondary dissolution of cements highlighted in black from a windward core (Laskowski 4). Whole core analysis values are porosity () = 16.4%, permeability (K) = 121 mD.

Lask4 3157’ (=12.2%, K=124 mD)

a) b) Jacob 3063’ (=7.1%, K=1.2 mD)

Figure 35: CT scanned cores comparing moldic and vuggy porosity that has (a) and has not (b) been enhanced due to secondary dissolution showing extent of permeability enhancement. Orange fill denotes pore space. 99

However, the Laskowski 5 core is also on the windward side of the reef but has the lowest average porosity and permeability values. This can be attributed to two things: 1) the Laskowski 5 core only contains 50 ft. of sediment between SB2 and SB3 as compared to the Laskowski 4 core which contains 220 ft. of sediment from below SB2 to above SB4 and 2) the Laskowski 5 core contains only three facies, two of which are mud-rich and have poor original porosity and permeability: Bioherm Facies 2 (mud rich), Reef Core Facies 3, and Restricted Facies 5 (mud and cyanobacterial mat rich). The highest framework density is in the Restricted Facies with cyanobacteria as the only identifiable fauna. In the reef core facies, the identifiable fauna are thamnoporid and auloporid tabulate corals along with brachiopod molds and crinoid pieces. This would indicate a lower energy environment below storm wave base (70 ft.) according to Klovan. It is interesting to note that no rugose corals were seen in this core. Additionally, an extreme paucity of fauna is found in both the Laskowski 4-1 and in Laskowski 5-1 cores directly below SB3. Sequence Boundary 3 is marked by an exposure interval/flooding surface in the Jacob (crest to leeward) and a flooding surface in the BTK (crest) core. It is not known whether this lack of fauna is due to diagenesis, an environment at the time of deposition that was too harsh for viability, or possibly sediment bypassing a cemented slope as was shown in the TOTO (Grammer, 1993a) and being deposited as a “lowstand fan”. This would account for the severe paucity of fauna on the higher foreslope Laskowski 4 (windward) core and the lack of fauna and the low porosity and permeability of the Laskowski 5-1 (windward) core located deeper on the foreslope due to the finer-grained sediment being deposited here as a “lowstand fan”. 100

This lack of fauna is not seen below SB3 in any other cores, except perhaps a less dramatic example in the Jacob 1-36 (crest to leeward) core where this area of the reef may be transitioning from a more crest/reef flat position and exposure to a more leeward position as evidenced by the change around SB3 from a wackestone- packstone texture with exposure/flooding to a skeletal wackestone-grainstone texture composed mostly of crinoid, coral, and stromatoporoid debris that is heavily cemented with signs of leaching and salt fill. These changes imply that the Jacob core was possibly exposed while on the crest but received the debris being shed off the crest to the leeward side as sea level rose again. The heavy cementation and some salt fill may account for the decrease in porosity/permeability values.

Analysis of Core Above Sequence Boundary 3 (SB3) or between SB3 and Sequence Boundary 4 (SB4)

The last sequence studied, between SB3 and SB4 (Figure 36), shows the Lask4 (windward margin) core containing a Reef Core Facies of less than 1% density with syndepositional vertical fractures, Skeletal Grainstone Facies consisting solely of stromatoporoid debris of less than 5%, and a Restricted Facies of cyanobacterial mats of over 20% density. The Halmich (crest) core is transitioning from a peloidal

mudstone-grainstone to a wacke-boundstone at SB4, and a wacke-packstone and then into the restricted cyanobacterial boundstone above SB4 indicating it was in deeper water than the Lask4 (windward), BTK (crest), and Jacob (crest to leeward) cores. The BTK (crest) core contains a flooding surface, Reef Core Facies with over 6% stromatoporoid density and over 1% tabulates, a Reef Debris Facies of less than 1% density, an exposure surface of over 1% stromatoporoids and 2% cyanobacterial mats, more Reef Core Facies, and a Restricted Facies of 1% cyanobacterial mats.

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The presence of both stromatoporoids and cyanobacterial mats in the exposure surface of the BTK (crest) core shows the rapidity of the change in depositional environment and the corresponding change in facies. The Lask4 (windward margin), BTK (crest), and Jacob (crest to leeward) cores all show the end of reef growth and the development of Restricted Facies with cyanobacterial mats. The higher density of cyanobacterial mats in the Lask4 (windward margin) and BTK (crest) cores may account for the decrease in porosity and permeability seen in these cores during this sequence. The Jacob (crest to leeward margin) core shows a Reef Core Facies containing over 18% stromatoporoids, a Reef Debris Facies of almost 1% tabulate corals, a Skeletal Grainstone Facies of less than 1% faunal density, and a few feet of Restricted Facies with cyanobacterial mats of less than 1% density. The increase in porosity and permeability values in the Reef Debris (Facies 3B) Facies, located below the exposure surface, accounts for most of the increase in this sequence as seen in Figure 31d. Due to the inability to correlate 4th order High Frequency Sequences across the reef, no attempt was made to infer trends in reservoir characteristics at this scale.

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Figure 36: Facies, texture, faunal density, percentage of cement, percentage of porosity, and permeability (mD) between Sequence Boundary 3 and Sequence Boundary 4. All cores except the Halmich (crest) core show the end of reef growth at SB4 with Restricted Facies consisting of cyanobacterial mats in the Lask4 (windward), Jacob (crest to leeward), and the BTK (crest) cores. The presence of both stromatoporoids and cyanobacterial mats in the exposure surface shows the rapidity of the facies transition. The Jacob core shows a Reef Core Facies consisting mostly of stromatoporoids. It also has a Reef Debris Facies rich in tabulate corals and a Skeletal Grainstone Facies. The Jacob core has a less dense restricted facies with cyanobacterial mats indicating that it may have been deeper on the leeward foreslope during this interval. The Halmich (crest) core is transitioning from a peloidal mudstone-grainstone with mostly unidentifiable debris back into a Reef Facies before ending reef growth with Restricted Facies of cyanobacterial mats. This indicates that the Halmich (crest) core was in deeper water than the other cores at SB4. The Percy core completes its reef life cycle between SB3 and SB4 and ends at SB4 with a Restricted Facies of mudstone with anhydrite. 104

CHAPTER VI: POTENTIAL APPLICATIONS AND FUTURE WORK

Potential Applications

The findings of this study are applicable to both academia and industry. From an academic perspective, this study provides a semi-quantitative description of the fauna that created Ray Reef. These findings, in addition to sequence stratigraphy (Wold, 2008), provide additional evidence that may help to better constrain Michigan Basin chronology since it is difficult, if not impossible, to do so using biostratigraphy since dolomitization has destroyed the most useful biomarkers (e.g. conodonts and

graptolites).104 Chemostratigraphy using stable carbon isotopes has been successfully employed in regions where biostratigraphy is not feasible. Indeed, recently stable carbon isotope excursions have been directly correlated with Silurian graptolite and conodont biozonations on a global Silurian sea level curve (Cramer et al., 2011).

13 Although recent studies have suggested that overall  Ccarb trends are not significantly affected by dolomitization (Glumac and Walker, 1998) and that 13C values of carbonate usually are not reset by diagenesis (Margaritz, 1983; Banner and

13 Hanson, 1990) attempts at using  Ccarb isotope excursions have not been successful in the pinnacle reefs of the Michigan Basin. However, the sequence boundaries identified in Ray Reef (Wold, 2008) are in general agreement with the timeframes published by Cramer et al. (2010) for the Mulde event. Additionally, Cramer and Saltzman (2007) propose that positive carbon isotope excursions occurred coincident to intervals of reef proliferation and carbonate platform expansion in epeiric seas and that rich organic shale deposition occurred prior to the carbon excursion. They propose that carbon sequestration was restricted to the deepest of intracratonic basins and the deep ocean. They use the Late 105

Llandovery Ireviken Excursion as an example and state that the expansion of carbonate platforms in the epeiric seas of Laurentia indicate that transgression of sea level continued during the rising limb of the Ireviken excursion. If the same is true for the Mulde Event, then all three 3rd order sequences identified in Ray Reef could have occurred during the Mulde Event. Wold’s Sequence Boundary 1 is placed at the top of the Lockport Dolomite (Gray Niagaran) which would correspond to the Homerian stage of the Wenlock series (Figure 46). The graptolite zones identified by Ross & Ross (1996) in the Illinois Basin coincide with the graptolite zones directly correlated to global Silurian

stable104 istope  Ccarb curve and the first and second peaks of the Mulde Excursion Event (Figure 37). Sequence Boundary 2 was the start of a transgressive phase and was based on 3rd order idealized stacking patterns and may coincide with the rising limb of the first peak in the Mulde Event. Sequence Boundary 3 was placed based on an exposure surface (sea level lowstand) noted in several cores and could also be indicative of the low after the first peak of the Mulde event (Figure 37). After SB3, sea level again transgresses until Sequence Boundary 4 which marks the end of reef growth and the deposition of anhydrite of the Salina A-1 Evaporite in the Michigan Basin. The rising limb of the second peak of the Mulde event could be the

corresponding transgression after SB3. The following regression could be the falling limb of the second peak of the Mulde Event (Figure 37). Sequence Boundary 4 could have occurred in the Gorstian Stage of the Ludlow Series after the Mulde event but before the Lau event. In order to make definite correlations, more data is needed,

13 especially  Ccarb values, which would help to align Michigan’s Provincial Series and Stages to that of the rest of North America and the world.

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107 2nd peak of Mulde

1st peak of Mulde

(Cramer et al., 2011)

(Ross & Ross, 1996)

Figure 37: From the conodont and graptolite zonations of Illinois (Ross and Ross, 1996) and the corresponding conodont and 13 rd graptolite zonations of the correlated  Ccarb curve (Cramer et al., 2011), it appears as though the three 3 order sequence boundaries identified in Ray Reef by Wold (2008) occurred during the Mulde event. However, there is neither biozonation nor stable isotope carbon excursion values from Michigan to verify this. 108

The findings of this study are also relevant to industry. This study has found similarities in reef/slope geometry, facies distribution, faunal distribution, and cementation between ancient Silurian reefs and Pleistocene to modern margins and slopes of the Tongue of the Ocean, Bahamas. The influences of wind and water energy are important parameters that should be considered when characterizing reefal reservoirs. Windward margins have been shown to include coarser grained sediments that undergo increased cementation due to the winnowing of finer sized sediments and the pumping of water through intergranular pore spaces. The increased cementation provides the ability for reefs and slopes to attain high degrees of declivity. The increased cementation may occlude porosity and permeability unless the cements are later dissolved out, thereby enhancing porosity and permeability. Conversely, leeward margins receive finer grained sediments that are swept off of the reef crest or reef flat and deposited in the lower energy leeward settings. These sediments have less original porosity and permeability due the mud-rich sediments. Community replacement as expressed by the change of fauna type and morphology as well as the increase in biomass (fauna perimeter) was recorded repeatedly coinciding with shallowing upward stratigraphic sequences throughout Ray Reef growth and development. This is in stark contrast to the “bucket models” of the 1970s and 1980’s that imply 300-600 ft. of uninterrupted reef growth. All of these findings imply that, although not a one-to-one correlation, the use of modern analogs is invaluable when attempting to understand ancient counterparts. The fauna may be very different, but the processes and forces that affect them may be very similar to what can be observed in the present or near past. However, more work needs to be done to clarify the effects of fauna on porosity, cementation, and diagenesis. 109

Future Work

Undoubtedly, there is not only one parameter that influences porosity and permeability (e.g. fauna type), but rather several parameters working in concert that add complexity and heterogeneity to reservoir characteristics. Nevertheless, now that some data has been documented and observations made, more informed questions may be asked. One that has surfaced concerns the major framebuilders, stromatoporoids, and their tendency to become “cemented up”. Some workers even state that the identification of stromatoporoids is sometimes made on the distinct dark brown banded cement that has replaced the stromatoporoid. Is this due to the original mineralogy, the small size of the chambers, whether or not the chambers are connected laterally? Is it an effect of being in a certain position on the reef, of being in a certain facies, surrounded by sediments of a certain size? Does the cementation of stromatoporoids effect reservoir characteristics? Does it enhance or occlude porosity and permeability? There are few studies published that research the effect of fauna on reef reservoir characteristics. The question of whether or not certain fossils generally occlude or enhance porosity and permeability has not been pursued. Besides the regular sedimentological approach of studying pore type, pore throat size, and grain size, additional data would be needed to answer this question. Among the most important of the parameters that would need to be studied would be the original mineralogy of each fossil, the size and shape of individual living chambers that were left as voids in each particular fossil and the interconnectedness of these chambers (e.g. corals with connecting pores between chambers vs. corals without pores connecting chambers), and the grain microstructure of each fossil. Factors complicating the determination of these parameters include the 110

original mineralogy of some of the fossils (i.e. stromatoporoids). This is controversial and impossible to prove on extinct fauna. It has also been shown that mineralogy may be less important than microstructural complexity (i.e. surface area) and solution saturation state in controlling dissolution rates of carbonate grains (Walter, 1985). Another question concerns the timing and type of diagenesis of reef and skeletal grainstone facies directly below 3rd and 4th order sequence boundaries. What are the types and quantities of cement in the various facies and energetic settings on

the reef? Have facies below 3rd order sequence boundaries porosity enhanced due to exposure? Have facies below 4th order sequence boundaries had porosity occluded due to cementation? Has syndepositional cement been secondarily dissolved? Have aragonitic fossils been dissolved creating molds and vugs and re-precipitated as calcite cements? How does the sea water chemistry at time of deposition (calcite seas during the Silurian) contribute to faunal relative abundance due to taphonomic effects? How did the sea water chemistry effect mineralogy of synsedimentary cements and later diagenesis? The answers to these questions are probably not dependent on only one parameter. But exploring these questions may help us to better understand the fauna of reefs and their effect on reservoir characteristics.

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CHAPTER VII: CONCLUSIONS

This study found similarities between Ray Reef (Silurian) and the margin and foreslope on windward and leeward margins of the Tongue of the Ocean, Bahamas in geometry, facies and faunal distribution, and cementation. This study supports other sequence stratigraphic based studies suggesting that these reefs are more laterally and vertically heterogeneous than previous models have predicted. Repeated changes in faunal morphology and biomass indicating community replacements coinciding with shallowing upward sequences and differences in faunal abundance, density, and diversity between windward, crest, and leeward margins are documented or have been identified. Reservoir characteristics were affected by differential cementation and secondary dissolution, as well as composition of skeletal grainstone facies, between windward, crest, and leeward margins.

Major Findings

Relative Abundance

Bryozoans were either first or second most abundant (20% or greater) fauna in crest cores with the other abundant fauna being unidentifiable fauna and crinoids in the crest Halmich core, crinoids at 19% in the crest BTK core, and brachiopods in the leeward Jacob. Brachiopods were either the first or second most abundant fauna in the windward cores with the other abundant fauna being unidentifiable fauna in Laskowski 4 core and cyanobacteria at 19% in Laskowski 5 core. The leeward Percy core had stromatoporoids and unidentifiable fauna as the most abundant. 112

Framework Density

Stromatoporoid density was highest on the reef crest and on the leeward side and was absent or unidentifiable on the windward side. Increased stromatoporoid density on the leeward side is in agreement with Schneider and Ausich (2002) and Klovan (1974) who found massive stromatoporoids restricted to the “central” (reef crest?) part of the reef. However, increased stromatoporoid density on the leeward side is in disagreement with Gischler (1995) who found massive stromatoporoids and bulbous corals dominant on the windward side along with encrusting and dendroid stromatoporoids. Overall faunal density was highest on the crest. The leeward Percy core had the least faunal density.

Diversity

Diversity was highest in the Reef Core Facies. Diversity was also highest in the crest cores. Tabulate coral diversity included favositids, thamnoporids, halysitids, and auloporids. Rugose corals included both solitary and colonial (Fletcheria sp.) forms. Stromatoporoids included encrusting, laminar to tabular, and hemispherical to domal forms (ragged non-enveloping and smooth enveloping).

Morphology

Klovan’s model for interpretation of water depth/fauna morphology was valuable and resembled the changes in communities seen in Ray Reef. Rugose corals and favositid tabulate corals could be added to the tabular stromatoporoid intermediate energy between wave base (30 ft.) and storm wave base (70 ft.). Rugose corals could also be added to the thamnoporid-disphyllid alveloites community from 113

storm wave base (70 ft.) and deeper. These changes in community replacement were seen repeatedly through all cores in association with shallowing upward conditions which coincided with third order stratigraphic sequences and higher frequency sequences.

Faunal Distribution

Rugose corals were most abundant in the lower energy settings and were not present when hemispherical or domal stromatoporoids were present. Tabulate corals (especially favositids) were found in higher energy settings where they replace the heliolitids (Scrutton, 1999). Rugose corals were sometimes absent in these higher energy settings. The crest cores showed the most repetitive cycles that culminated in hemispherical/domal stromatoporoids implying the highest water energies and the climax stage of reef development. Few crinoids and no bryozoans were found in windward cores, but many brachiopod molds were found. Extreme diagenesis, nonviable conditions, or sediment bypass were interpreted below SB3 on the windward Laskowski cores, and to a much lesser extent in the Jacob core.

Cement

The windward Laskowski 4 core had the highest percentage of cementation. Windward cores also had higher amounts of visually detected porosity. Large amounts of syndepositional cements were probably present but have been dissolved out creating secondary porosity and permeability. 114

Cement averaged 19.25% with a high of 28.12% on the windward side and a low of 12.20% on the leeward side. The crest ranged from 21% to 25% cement.

In situ vs. Debris

The reef was composed mostly of rubble or debris with the average for the six cores being 23% in situ fauna and 77% debris.

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Appendix A

HALMICH 2-1 (PN24763) RESULTS AND SUPPORTING TABLES AND FIGURES

116

PN24763: Halmich 2-1 Results

Relative Abundance: Framework Density, Reef-Builder Diversity, and Composition of Reef-Builder Assemblages

Relative Abundance Analysis of the proportion of high level categories of fauna, when the sum of all fauna equaled 100 percent, showed that the most numerous faunal categories were Unidentified fauna, bryozoans, and crinoids (Tables 1 & 5). The frame-builders were represented by unidentified fauna, stromatoporoids, tabulate and rugose corals. Among the non-framebuilders, bryozoans and crinoids were the second and third most abundant fauna, respectively. Brachiopods were the least abundant at just over 1%.

Percent of Population Faunal Category (when sum of all fauna equals 100%) Unidentified 29.27 Bryozoans 25.84 Crinoids 21.67 Stromatoporoids 10.90 Stromatolites and cyanobacteria 6.96 Tabulate corals 3.11 Rugose corals 1.21 Brachiopods 1.03 Table 1: Percent of population contributed by each faunal category.

Reef-Builder Diversity Faunal diversity, as expressed by the number of faunal categories represented, is summarized in Tables 2 & 5. Diversity was highest in the Reef Core Facies 3A with 7 categories of fauna represented. The Bioherm Core Facies 2 had a medium range of representation (range of 3-6). The Restricted Facies 5 ranged from1-4 faunal categories and the Reef Debris Facies 3B had 2 faunal categories. Tabulate corals were represented by favosities, halysites, and thamnoporid types.

Number of Faunal Categories Facies Represented Restricted Facies 5a-d 2, 1, 2, 4 Skeletal Grainstone Facies 4 1, 0, 0, 0, 0, 0, 1, 0 Reef Debris Facies 3B 2 Reef Core Facies 3A 2, 0, 4, 7, 2, 7, 1, 0, 7, 0, 7, 3, 6, 5, 5, 6, 6 Bioherm Core Facies 2 4, 0, 1, 6, 4, 5, 4, 0, 3 Table 2: Number of faunal categories represented in each facies (a coarse indicator of diversity). 117

Framework Density When analyzed according to the percentage of the slabbed core surface that was covered by fauna, the total area covered was 6.52% of the 294 feet of studied core. Unidentified fauna had the highest percentage of coverage with 3.36% (Table 3). Stromatoporoids, and stromatolites had just over 1% coverage. All other faunal categories had 0.5 % or less coverage.

Faunal Category Percent of Slabbed Core Surface Coverage Unidentified 3.36 Stromatoporoids 1.18 Stromatolites 1.16 Tabulate corals 0.54 Bryozoans 0.13 Rugose corals 0.10 Crinoids 0.05 Brachiopods 0.01 Table 3: Density of faunal categories as a percentage of slabbed core surface coverage.

When analyzed by facies, the Reef Debris Facies 3B had the highest coverage with 24.5% of which 22.5% was stromatoporoid in 2.6 feet (Tables 4 & 6). The Restricted Facies 5c had the second highest coverage with 17% of 6.7 feet. The Reef Core Facies 3A provided 4.3% coverage in 212 feet and the Bioherm Core Facies 2 provided 3.8% coverage in 20 feet. Both the Reef Core Facies and Bioherm Core Facies contained all categories of fauna except cyanobacteria/stromatolites. The Skeletal Grainstone Facies had the least coverage with 0.16% in 8 feet.

Facies Faunal Categories with Most Coverage Reef Debris Facies 3B 24.5 % (2.6 ft.) – stromatoporoids 22.5%, unid Restricted Facies 5c 17.13% (51 ft.) – cyano 6.72%, unid 6.67% Reef Core Facies 3A 4.29% (212 ft.) – stromatoporoids .46%, unid 3.31% , all categories represented except cyano Bioherm Core Facies 2 3.83% (20 ft.) – unid 3.4%, all categories represented except cyano Skeletal Grainstone Facies 4 0.16% (8 ft.) – all unid Table 4: Faunal category coverages per facies.

Composition of reef-building assemblages and distribution Due to the high degree of diagenesis encountered in this core, there was a much higher percentage of unidentifiable fauna. From the bottom of the studied core at 3219’ to Sequence Boundary 2 at 3142’ there were mostly encrusting, laminar to 118

tabular, massive, and branching forms of unidentifiable fauna. Branching bryozoans were identified throughout this interval as were several medium to large solitary rugose corals, branching tabulates (thamnoporids and halisites/aulocysts), and several favositids. Between Sequence Boundary 2 at 3142’ and Sequence Boundary 3 at 3028’, there are four notable instances of identifiable fauna. At 3134’ there are encrusting stromatoporoids and bryozoans with laminar to tabular tabulate corals at 3135’ and 3138’. There are laminar to tabular stromatoporoids at 3099’ and encrusting stromatoporoids at 3097’ with favositid tabulate corals up to 3095’. At 3080’ and 3079’ there are favositid corals with unidentified fauna and encrusting stromatoporoids at 3076’ and laminar to tabular stromatoporoids at 3074’ with favosites. This is overlain by cyanobacteria at 3072’. Encrusting stromatoporoids appear again at 3041’ with unidentified fauna and favosites. Throughout this interval solitary rugose corals go from smallish in size at 3116’, 3113’, and 3084’ to medium sized at 3075’-3074’, 3066’, to medium to larger sizes at 3057’, 3041’, 3040’, 3039’, 3035’, 3034’, 3032’-3030’. Also found throughout this interval are unidentifiable fauna, branching bryozoans and tabulates. Between Sequence Boundary 3 at 3028’and Sequence Boundary 4 at 2933’ there are two instances where stromatoporoids can be identified. At 3025’ the stromatoporoids are encrusting and at 3024’ they are laminar to tabular. Along with the stromatoporoids are encrusting, massive, and branching unidentifiable fauna. There are also small and medium solitary rugose corals at 3026’, 3024’ and 3020’. Large solitary rugose corals are found at 3005’ and 3000’ while medium sized solitary rugose corals are noted at 2999’, 2998’, and 2995’. There were no rugose corals found above 2995’. There are laminar to tabular stromatoporoids at 2954’, 2950’, and 2949’ with massive hemispherical to domal stromatoporoids at 2951’-2949’. There also instances of cyanobacteria at 2975’-2968’ and 2960’-2958’. Above 2949’ to Sequence Boundary 4, there are very few fauna and they are all unidentifiable. Immediately above Sequence Boundary 4 at 2933’ to 2929’ are pieces of laminar to tabular and massive hemispherical to domal stromatoporoids. From 2929’ to the top of the core at 2923’are laminar to tabular and massive hemispherical to domal cyanobacteria and stromatolites.

Cement The Halmich 2-1 core is on the interpreted crest of Ray Reef. The estimated percent of cement identified on the slabbed surface of this core was 24.74%.

In situ vs Debris The examined slabbed surface of this core was comprised of 16% in situ fossils and 84% debris.

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m h Unidd Stromo b Rug Bryz Crin Brachc Tabulate n a ryz i Uni Str T Rug B C Bra -2928 2933 SB4

-2944

-2960

-2976 2978 HFSB

-2992

-3008

-3024 3028 SB3

120 -3040

-3056

-3072 -3088 3095 HFSB -3104

-3120

-3136 3143 SB2

-3152

-3168

-3184 3190 HFSB

-3200

-3216 1000 2000 3000 4000 5000 6000 7000 8000 Figure 1: Spindle diagram showing the core depth in feet on the Y axis and fauna perimeter on the X axis. The solid lines represent 3rd order sequence boundaries (SB) and the dashed lines represent high frequency sequence boundaries (HFSB) with the footage depth noted to the left. From left to right the fauna measured are Unid=unidentified fauna; Strom=stromatoporoids; Tabulate=tabulate corals; Rug=rugose corals; Bryz=bryozoans; Crin=crinoids; Brach=brachiopods.

Average Perimeter of Faunal Category

Average Perimeter (mm) 0 1000 2000 3000 4000 5000 6000 7000 2900

2950

3000

3050

3100 Depth (ft.) Depth

3150

3200

3250

Unid Cyano Stromatoporoid Tabulate Rugose Brach Bryozoan Crinoid SB

Figure 2: Average perimeter of all fauna vs. depth of studied core.

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Average Perimeter of Framebuilding Fauna

Average Perimeter (mm) 0 500 1000 1500 2000 2500 2900 SB4 2950

3000 SB3

3050

Depth (ft.) Depth 3100

SB2 3150

3200

3250

Unid Stromatoporoid Tabulate Rugose SB

Figure 3: Average perimeter of frame-building fauna vs. depth of studied core with Sequence Boundaries marked. Note the increase in stromatoporoid and tabulate coral abundance from SB2 to SB3 with an increase in size close to SB3. Also, rugose corals are clustered below SB2 and around SB3. From SB3 to SB4 stromatoporoids are smaller but concentrated toward SB4 whereas the rugose and tabulate corals are not seen above ~3000 feet in the core.

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Average Perimeter of Non-Framebuilding Fauna

Average Perimeter (mm) 0 100 200 300 400 500 600 700 800 2900

SB4 2950

3000 SB3

3050

Depth (ft.) 3100

SB2 3150

3200

3250

Brach Bryozoan Crinoid SB

Figure 4: Average perimeter of nonframe-building fauna vs. depth of studied core with Sequence Boundaries marked. Note the decrease in abundance and size moving from SB2 to SB3 and SB4.

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Average Perimeter of Faunal Category Above SB4

Average Perimeter (mm) 0 500 1000 1500 2000 2500 3000 2922

2924

2926

2928 Depth (ft.) Depth 2930

2932

2934

Unid Cyano Stromatoporoid

Figure 5: Average perimeter of fauna vs. depth above Sequence Boundary (SB) 4. Note the absence of all faunal categories except unidentified fauna, cyanobacteria - stromatolites, and stromatoporoids. This is the end of the Wenlock reef building.

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Average Perimeter of Faunal Category BetweenSB3 and SB4

Average Perimeter (mm) 0 1000 2000 3000 4000 5000 6000 7000 2920

2940

2960

2980 Depth (ft.)

3000

3020

3040

Unid Cyano Stromatoporoid Tabulate Rugose Brach Bryozoan Crinoid

Figure 6: Average perimeter of all faunal categories vs. depth between Sequence Boundaries 3 and 4. Note the absence of both tabulate and rugose corals above 2990’.

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Average Perimeter of Faunal Category BetweenSB2 and SB3

Average Perimeter (mm) 0 500 1000 1500 2000 2500 3020

3040

3060

3080

3100 Depth (ft.)

3120

3140

3160

Unid Cyano Stromatoporoid Tabulate Rugose Brach Bryozoan Crinoid

Figure 7: Average perimeter of all faunal categories vs. depth between Sequence Boundaries 2 and 3. Note the decrease in prevalence of non-framebuilding bryozoans and crinoids and the increase in stromatoporoids as compared to below SB 2. Also note that rugose corals are scarce near the bottom of this sequence but are plentiful near the top of the sequence.

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Average Perimeter of Faunal Category Below SB2

Average Perimeter (mm) 0 200 400 600 800 1000 1200 1400 1600 1800 3130

3140

3150

3160

3170

3180

Depth (ft.) Depth 3190

3200

3210

3220

3230

Unid Cyano Stromatoporoid Tabulate Rugose Brach Bryozoan Crinoid

Figure 8: Average perimeter of all faunal categories vs. depth below Sequence Boundary 2. Note the prevalence of non-framebuilders (bryozoans and crinoids especially) and frame-building corals but lack of stromatoporoids in this sequence.

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Facies Halmich 2-1 Above SB 4 domal to dendroid laminar to hemi or robust delicate solitary colonial Ftg SB 1 2 3A 3B 4 5 in situ debris encrust tabular massive branch branch rugose rugose 2923 cyano 2924 cyano 2925 cyano 2926 cyano/unid 2927 cyano 2928 unid 2929 stromatop stromatop 2930 stromatop stromatop 2931 stromatop stromatop 2931.66 2932 stromatop stromatop 2933 unid unid stromatop 2933 4

Figure 9: Stratigraphic column showing fauna, morphology, and in-situ vs. debris for studied core above SB4.

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Facies Halmich 2-1 SB3 to SB4 domal to laminar to hemi or dendroid robust solitary colonial Ftg SB 1 2 3A 3B 4 5 in situ debris encrust tabular massive branch delicate branch rugose rugose 2933 4 2934 unid 2935 2936 2937 2938 missing 2939 missing 2940 missing 2941 unid 2942 2943 2944 unid 2945 2946 2947 2948 2949 stromatop stromatop 2950 stromatop stromatop 2951 unid stromatop 2952 cyano 2953 unid 2954 stromatop 2955 2956 unid unid 2957 unid unid 2958 cyano/unid romatop/unid 2959 cyano 2960 cyano/unid unid - hemi 2961 unid unid 2962 unid 2963 unid unid 2964 unid unid 2965 unid 2966 unid unid 2967 unid 2968 cyano/stromatop 2969 cyano/unid cyano/unid 2970 cyano 2971 cyano/unid 2972 unid 2973 unid 2974 cyano 2975 cyano/unid 2976 unid 2977 2978 (continued)

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2978 2978.1 2979 2979.5 2980 2980.7 2981 2983 unid bryz 2984 unid bryz 2985 unid unid 2985.4 2985.9 2986 unid 2987 unid 2988 unid 2989 bryz 2990 2991 bryz 2992 unid 2993 2994 unid 2995 unid unid thamno med 2996 unid unid 2997 unid unid 2998 unid favosites unid med 2999 favosites stromatop/bryz/unid med 3000 unid large 3001 unid unid 3002 unid 3003 unid unid 3004 3005 unid large 3006 favosites unid/strom? 3007 3008 3009 3010 unid 3011 3012 3013 3014 unid favosites 3015 unid 3016 3017 3018 3019 unid 3020 bryz/unid small 3021 unid 3022 unid unid 3023 unid unid 3024 stromatop unid med 3025 stromatop unid 3026 unid small 3027 3027.5 3028 3

Figure 10: Stratigraphic column showing fauna, morphology, and in-situ vs. debris for studied core between SB3 and SB4.

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Facies Halmich 2-1 SB2 to SB3 dendroid laminar to domal to hemi or robust solitary colonial Ftg SB 1 2 3A 3B 4 5 in situ debris encrust tabular massive branch delicate branch rugose rugose 3028 3 3028 unid 3028.5 3029 unid unid 3030 unid unid med 3031 favosites large 3032 unid unid med 3033 unid unid bryz 3034 unid large 3035 unid med-lrg 3036 unid favosites/unid 3037 unid 3038 unid unid 3039 unid favosites med 3040 unid unid large 3041 stromatop/unid unid large 3042 missing 3043 unid unid 3044 favosites unid 3045 missing 3046 unid favosites/unid unid 3047 missing 3048 unid unid thamno 3049 unid unid 3050 unid favosites/unid 3051 unid favosites/unid 3052 unid favositid 3053 3054 unid unid unid 3055 unid 3056 unid 3057 large 3058 unid unid 3059 favositid unid 3060 missing 3061 unid favosites bryz 3062 unid unid 3063 unid favosites unid 3064 unid unid 3065 unid unid 3066 unid favosites unid med 3067 3067.1 3067.85 unid 3068 unid 3069 unid 3070 3071 3072 cyano 3073 3074 stromatop favosites unid bryz med 3075 med 3076 stromatop unid unid 3077 unid unid 3078 unid unid bryz/thamno 3079 favosites unid thamno 3080 favosites/unid unid 3081 unid 3082 unid unid 3083 favo/unid unid 3084 unid bryz small 3085 unid bryz 3086 bryz 3087 unid favosites unid 3088 unid bryz 3089 3090 3091 3092 unid (continued) 131

3091 3092 unid 3093 3094 3095.25 unid 3095.6 favositid 3096 favo/unid 3097 stromatop favosites/favo 3098 unid 3099 stromatop unid 3100 unid unid 3101 3102 unid 3103 unid unid 3104 unid 3105 unid 3106 unid 3107 3108 favo/unid unid 3109 3110 unid unid 3111 unid unid 3112 3113 bryz small 3114 unid tab 3115 unid bryz/unid/thamno 3116 unid small 3117 favo unid 3118 3119 tab unid/bryz 3120 unid/bryz 3121 favo favo unid 3122 unid unid 3123 favo/unid 3124 favo thamno? 3125 3126 bryz 3127 unid unid 3128 3129 unid 3130 unid 3131 3132 thamno 3133 3134 stromatop/bryz unid bryz 3135 unid favositid 3136 unid 3137 favo 3138 favositid 3139 unid halysites 3140 tab bryz/unid 3141 bryz 3142 bryz 3142 2

Figure 11: Stratigraphic column showing fauna, morphology, and in-situ vs. debris for studied core between SB2 to SB3

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Facies Halmich 2-1 Below SB2

laminar to domal to hemi dendroid robust delicate solitary colonial Ftg SB 1 2 3A 3B 4 5 in situ debris encrust tabular or massive branch branch rugose rugose 3142 2 3142.5 halysites 3143 3144 unid halysites 3145 unid halysites 3146 3147 favositids bryz/thamno/unid 3148 unid tab unid 3149 bryz 3150 halysites/thamno 3151 3152 3153 unid bryz - some feathery/thamno 3154 bryz unid 3155 bryz 3156 unid 3157 tab bryz 3158 thamno 3159 unid unid bryz 3160 unid bryz 3161 unid bryz-feathery 3162 bryz 3163 bryz-feathery 3164 bryz 3165 bryz/unid 3166 favo bryz 3167 favo - halysites or aulocyst? 3168 unid/favositid thamno? 3169 bryz/unid 3170 bryz 3171 unid unid bryz/unid 3172 unid bryz 3173 unid bryz/unid 3174 unid bryz/unid 3175 unid bryz/unid 3176 unid favo/unid bryz/unid 3177.5 bryz favo bryz 3178 bryz/unid (continued)

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3175 unid bryz/unid 3176 unid favo/unid bryz/unid 3177.5 bryz favo bryz 3178 bryz/unid 3179 unid unid bryz med 3180 unid unid unid bryz 3181 unid unid bryz med 3182 unid unid unid bryz 3183 unid bryz 3184 unid unid bryz large 3185 unid bryz-feathery 3186 bryz bryz 3187 bryz 3188 tab - aulocyst/halysites? 3189 unid bryz/unid 3190 unid bryz/halisites/tha large 3191 unid unid bryz/tab 3192 bryz/unid unid/favositid bryz 3193 unid bryz/unid med 3194 unid unid bryz/unid large 3195 unid favo-emmonsia type/ bryz/unid med 3196 unid bryz large 3197 unid unid bryz 3198 bryz unid unid 3199 bryz/unid/tab thamno? 3199.25 3200 unid tab bryz/unid 3201 bryz 3202 tab tab bryz 3203 unid unid 3204 unid unid 3205 unid unid 3206 unid unid unid 3207 3207.6 unid unid 3208 unid bryz 3209 unid bryz 3210 stromatop bryz med-large 3211 unid bryz 3212 unid bryz/unid 3213 bryz/unid med 3214 unid unid unid bryz/unid 3215 unid 3216 unid bryz med 3217 unid 3218 bryz/unid bryz 3219 unid unid

Figure 12: Stratigraphic column showing fauna, morphology, and in-situ vs. debris for studied core below SB2.

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brachiopods/gastr stromatolites stromatoporoids bryozoans crinoids opods/ostracodes tabulate corals rugose corals unidentified Total Faunal Number Begin Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Count for of Phyla ftg. End ftg. Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies Identified 2923 2929 5c 220 96 0 0 0 0 0 0 10 4 230 2 2929 2931.66 3b 0 412 100 0 0 0 0 0 1 0 413 2 2931.7 2933.25 3a W-Bs 0 31 89 0 0 0 0 0 4 11 35 2 SB4 2933.3 2936.1 5a 0 0 0 0 0 0 0 2 100 2 1 2936.1 2949 5b 0 0 0 0 3 20 0 0 12 80 15 2 2949 2978.1 5c/5d 91 35 21 8 0 0 1 0 0 0 146 56 259 4 2978.1 2979 4 0 0 0 0 0 0 0 1 100 1 1 2979 2979.5 3a W-Ps 00 2979.5 2980.7 4 00 2983 2985.4 3a W-P 0 4 12 3 9 2 6 0 0 0 24 73 33 4 2985.4 2985.9 4 0 0 0 0 0 0 0 0 0 0 2985.9 3027 3a W-P 0 7 5 11 8 6 4 5 4 9 7 9 7 87 65 134 7 3027 3027.5 4 0 0 0 0 0 0 0 0 0 0 3027.5 3028 3a W-P 0 0 0 1 0 0 0 0 1 50 2 2 SB3 3028 3028.5 4 0 0 0 0 0 0 0 0 0 0 3028.5 3067.1 3a W-P 0 1 1 4 2 2 1 3 2 21 11 20 10 147 74 198 7 3067.1 3067.85 4 0 0 0 0 0 0 0 0 0 0 3067.9 3071 3a W-P 0 0 0 0 0 0 0 7 100 7 1 3071 3073 3a M-P 00 3073 3092 3a W-G 0 3 3 11 13 5 6 2 2 15 17 2 2 50 57 88 7 3092 3095.25 4 0 0 0 0 0 0 0 3 100 3 1 3095.3 3095.6 3a M-P 00 3095.6 3142.5 3a W-G 0 5 1 51 12 52 12 6 1 35 8 3 1 287 65 439 7 SB2 3142.5 3143 4 0 0 0 0 0 0 0 0 0 0 3143 3143.8 3a W-P 0 0 0 1 13 0 1 13 0 6 75 8 3 3143.8 3172 3a W-Pc 0 0 222 39 190 33 7 1 31 5 3 1 115 20 568 6 3172 3173 3a B-Wb 0 0 175 87 16 8 4 2 0 1 0 5 2 201 5 3173 3177.5 3a W-Pc 0 0 66 26 128 51 2 1 6 2 0 50 20 252 5 3177.5 3189.8 3a W-Pbc 0 0 320 44 292 40 5 1 6 1 3 0 104 14 730 6 3189.8 3199.25 3a W-Gc 0 0 204 39 210 40 1 0 12 2 9 2 91 17 527 6 3199.3 3207 2 Bb 0 0 22 30 16 22 0 3 4 0 32 44 73 4 3207 3207.6 2 W-P 0 0 0 0 0 0 0 0 0 0 3207.6 3208 2 M-Wb 0 0 0 0 0 0 0 10 100 10 1 3208 3211 2 M-P 0 3 6 18 33 7 13 4 7 0 2 4 20 37 54 6 3211 3212 2 M-Wb 0 0 4 15 3 12 2 8 0 0 17 65 26 4 3212 3215 2 W-P 0 0 27 32 18 21 1 1 0 1 1 37 44 84 5 3215 3217.33 2 W-Pcb 0 0 6 12 14 28 0 0 1 2 29 58 50 4 3217.3 3218 2 W-Pb 00 3218 3219.6 2 W-Pcb 0 0 10 42 5 21 0 0 0 9 38 24 3 Whole core totals 311 7 487 11 1154 26 968 22 46 1 139 3 54 1 1307 29 4466

pg stromatolites stromatoporoids bryozoans crinoids opods/ostracodes tabulate corals rugose corals unidentified Total Faunal Number Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Count for of Phyla Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies Identified 5a-d 311 61 21 4 0 0 4 1 0 0 170 34 506 4 4 0 0 0 0 0 0 0 4 100 4 1 3b 0 412 100 0 0 0 0 0 1 0 413 2 3a 0 51 2 1067 33 905 28 35 1 136 4 50 2 978 30 3222 7 2 0 3 1 87 27 63 20 7 2 3 1 4 1 154 48 321 7 Whole core totals 311 6.96 487 10.90 1154 25.84 968 21.67 46 1.03 139 3.11 54 1.21 1307 29.27 4466

Table 5: Relative abundance and diversity when the sum of all fauna equals 100 percent.

135

brachiopods/gastropo stromatolites stromatoporoids bryozoans crinoids ds/ostracodes tabulate corals rugose corals unidentified Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent Percent of Percent Percent of Percent Percent of Sum of Percentage Total facies total core facies total core facies total core facies total core facies total core of facies total core of facies total core of facies total core facies area of facies percent surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface covered by area area (ft x Begin ftg. End ftg. Facies area area area area area area area area area area area area area area area area fauna covered 100) 2923 2929 5c 79.45 0.27 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3.53 0.59 82.98 13.83 600 2929 2931.66 3b 0.00 0.00 59.75 22.46 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.32 0.00 60.07 22.58 266 2931.66 2933.25 3a W-Bs 0.00 0.00 62.51 39.32 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 29.09 18.30 91.60 57.61 159 SB4 2933.25 2936.1 5a 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 23.19 8.14 23.19 8.14 285 2936.1 2949 5b 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.11 0.01 0.00 0.00 0.00 0.00 9.17 0.71 9.28 0.72 1287 2949 2978.1 5c/5d 262.30 5.16 189.74 6.52 0.00 0.00 0.00 0.00 0.06 0.00 0.00 0.00 0.00 0.00 303.11 10.42 755.21 25.95 2910 2978.1 2979 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 90 2979 2979.5 3a W-Ps 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 50 2979.5 2980.7 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 120 2983 2985.4 3a W-P 0.00 0.00 10.36 4.32 0.09 0.04 0.03 0.01 0.00 0.00 0.04 0.00 0.00 55.28 23.03 65.81 27.42 240 2985.4 2985.9 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 50 2985.9 3027 3a W-P 0.00 0.00 7.68 0.19 1.13 0.03 0.13 0.00 0.39 0.00 3.94 0.10 5.89 0.14 163.22 3.97 182.39 4.44 4110 3027 3027.5 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 50 3027.5 3028 3a W-P 0.00 0.00 0.00 0.00 0.00 0.00 0.83 1.66 0.00 0.00 0.00 0.00 0.00 0.00 0.73 1.46 1.56 3.12 50 SB3 3028 3028.5 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 50 3028.5 3067.1 3a W-P 0.00 0.00 1.33 0.03 0.08 0.00 0.16 0.00 0.31 0.01 25.87 0.67 12.66 0.33 86.10 2.23 126.52 3.28 3856 3067.1 3067.85 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 75 3067.85 3071 3a W-P 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.89 0.92 2.89 0.92 315 3071 3073 3a M-P 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 200 3073 3092 3a W-G 0.00 0.00 5.20 0.27 0.72 0.04 0.12 0.01 0.33 0.00 20.81 1.10 0.25 0.01 33.06 1.74 60.50 3.18 1900 3092 3095.25 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.27 0.39 1.27 0.39 325 3095.25 3095.6 3a M-P 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 35 3095.6 3142.5 3a W-G 0.00 0.00 9.65 0.21 1.80 0.04 1.59 0.03 0.27 0.01 51.45 1.10 0.14 0.00 46.88 1.00 111.78 2.38 4689 SB2 3142.5 3143 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 50 3143 3143.8 3a W-P 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 4.91 6.14 0.00 0.00 3.33 4.17 8.26 10.32 80 3143.8 3172 3a W-Pc 0.00 0.00 0.00 0.00 6.81 0.24 2.67 0.09 0.20 0.01 21.14 0.75 2.74 0.10 50.14 1.78 83.70 2.97 2820 3172 3173 3a B-Wb 0.00 0.00 0.00 0.00 3.58 3.58 0.25 0.25 0.19 0.19 0.00 0.00 0.11 0.11 2.98 2.98 7.12 7.12 100 3173 3177.5 3a W-Pc 0.00 0.00 0.00 0.00 2.01 0.45 3.23 0.72 0.07 0.02 4.00 0.89 0.00 0.00 5.59 1.24 14.91 3.31 450 3177.5 3189.8 3a W-Pbc 0.00 0.00 0.00 0.00 11.19 0.91 2.40 0.19 0.03 0.00 7.45 0.61 1.54 0.13 69.52 5.65 92.14 7.49 1230 3189.8 3199.25 3a W-Gc 0.00 0.00 0.00 0.00 6.66 0.70 2.11 0.22 0.40 0.04 15.91 1.68 3.96 0.42 31.63 3.35 60.67 6.42 945 3199.25 3207 2 Bb 0.00 0.00 0.00 0.00 1.06 0.14 0.42 0.05 0.00 0.00 2.15 0.28 0.00 0.00 10.04 1.30 13.66 1.76 775 3207 3207.6 2 W-P 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 60 3207.6 3208 2 M-Wb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.41 11.03 4.41 11.03 40 3208 3211 2 M-P 0.00 0.00 1.98 0.66 0.84 0.28 0.05 0.02 0.04 0.01 0.00 0.00 0.66 0.22 5.75 1.92 9.31 3.10 300 3211 3212 2 M-Wb 0.00 0.00 0.00 0.00 0.75 0.75 0.02 0.02 0.05 0.05 0.00 0.00 0.00 0.00 7.73 7.73 8.55 8.55 100 3212 3215 2 W-P 0.00 0.00 0.00 0.00 0.72 0.24 0.21 0.07 0.02 0.01 0.00 0.00 0.13 0.04 3.43 1.14 4.50 1.50 300 3215 3217.33 2 W-Pcb 0.00 0.00 0.00 0.00 0.40 0.17 0.15 0.06 0.00 0.00 0.00 0.03 0.28 0.12 34.19 14.67 35.01 15.02 233 3217.33 3218 2 W-Pb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 67 3218 3219.6 2 W-Pcb 0.00 0.00 0.00 0.00 0.65 0.41 0.04 0.03 0.00 0.00 0.00 0.00 0.00 0.00 1.78 1.11 2.47 1.55 160 Whole core totals 341.75 1.16 348.21 1.18 38.50 0.13 14.41 0.05 2.46 0.01 157.69 0.54 28.36 0.10 988.39 3.36 1919.76 6.52 29422

pg p stromatolites stromatoporoids bryozoans crinoids ds/ostracodes tabulate corals rugose corals unidentified Percentage Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent Percent of Percent Percent of Percent Percent of Sum of of facies Total facies total core facies total core facies total core facies total core facies total core of facies total core of facies total core of facies total core facies area area percent surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface covered by covered by area (ft x Facies area area area area area area area area area area area area area area area area fauna fauna 100) 5a-d 341.75 6.72 189.74 3.73 0.00 0 0.00 0 0.17 0.003 0.00 0 0.00 0 338.99 6.67 870.66 17.13 5082 4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.27 0.16 1.27 0.16 810 3b 0.00 0.00 59.75 22.46 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.32 0.12 60.07 24.52 266 3a 0.00 0.00 96.74 0.46 34.08 0.16 13.53 0.06 2.19 0.01 155.54 0.73 27.30 0.13 580.46 2.73 909.84 4.29 21229 2 0.00 0.00 1.98 0.10 4.42 0.22 0.88 0.04 0.10 0.01 2.15 0.11 1.06 0.05 67.33 3.31 77.92 3.83 2035 Whole core totals 341.75 1.16 348.21 1.18 38.50 0.13 14.41 0.05 2.46 0.01 157.69 0.54 28.36 0.10 988.39 3.36 1919.76 6.52 29422

Table 6: Density of fauna when the total area of the slabbed core surface equals 100 percent.

136

Appendix B

JACOB 1-36 (PN24987) RESULTS AND SUPPORTING TABLES AND FIGURES

137

Jacob 1-36 Results

Relative Abundance: Framework Density, Reef-Builder Diversity, and Composition of Reef-Builder Assemblages

Relative Abundance Analysis of the proportion of high level categories of fauna, when the sum of all fauna equaled 100 percent, showed that the most numerous faunal categories were the brachiopods and bryozoans (see Tables 1 & 5). The frame-builders were represented by tabulate corals, unidentified fauna, stromatoporoids, and rugose corals. The nonframebuilders included crinoids as well as the brachiopods and bryozoans. Stromatolites and cyanobacteria were also identified.

Percent of Population Faunal Category (when sum of all fauna equals 100%) Brachiopods 29.79 Bryozoans 26.39 Tabulate corals 11.93 Unidentified 10.13 Crinoids 9.79 Stromatoporoids 4.33 Stromatolites and cyanobacteria 4.21 Rugose corals 3.43 Table 1: Percent of population contributed by each faunal category.

Reef-Builder Diversity Faunal diversity, as expressed by the number of faunal categories represented, is summarized in Tables 2 & 5. Diversity was highest in the Reef Core Facies 3A with multiple occurrences of 7 categories of fauna represented. The Reef Debris Facies 3B also had one occurrence of 7 categories of fauna represented, but had only 0 or 2 categories represented below SB2. Restricted Facies had only 1 faunal category represented. There were several types of tabulate corals represented including favositids, thamnoporids, auloporids, halysitids, and unidentified encrusting tabulate coral.

138

Facies Number of Faunal Categories Represented Restricted Facies 5c 1 Skeletal Grainstone Facies 4 SB4 to SB3 3 SB2 to SB3 0 Below SB2 6, 0 Reef Core Facies 3A SB4 to SB3 2 SB2 to SB3 7, 7 Below SB2 5, 7, 5, 1 Reef Debris Facies 3B SB4 to SB3 7 Below SB2 0, 2 Exposure Interval SB3 to SB2 3 Below SB2 6, 1 Table 2: Number of faunal categories represented in each facies (a coarse indicator of diversity).

Framework Density When analyzed according to the percentage of the slabbed core surface that was covered by fauna, the total area covered was 4.44% of the 288 feet of studied core. Stromatolites had the highest percentage of coverage with 1.30% (Tables 3 & 6). Stromatoporoids and Tabulate corals each covered just less than 1%. All other faunal categories covered .5% (crinoid and bryozoan) or.

Faunal Category Percent of Slabbed Core Surface Coverage Stromatolites 1.30 Stromatoporoids 0.81 Tabulate corals 0.79 Crinoids 0.54 Bryozoans 0.45 Brachiopods 0.30 Rugose corals 0.17 Unidentified 0.09 Table 3: Density of faunal categories as a percentage of slabbed core surface coverage.

When analyzed by facies, the Restricted Facies 5c had the highest coverage with stromatolites occupying 12.34% of 30 feet (Tables 4 & 6). The Reef Core Facies provided 3.51% coverage and the Reef Debris Facies covered 1.86%.

139

Facies Faunal Categories with Most Coverage Restricted Facies 5c 12.34% stromatolites (30 ft.) Skeletal Grainstone Facies 4 6.17% (41 ft.) Reef Debris Facies 3B 1.86% (54 ft.) Reef Core Facies 3A 3.51% (154 ft.) Exposure Surfaces 1.58% (9 ft.) Table 4: Faunal category coverages per facies.

Composition of reef-building assemblages and distribution The bottom of the Jacob 1-36 core had a couple of favositid tabulate corals present at 3251’ and 3249’ along with branching bryozoans. Additional massive and branching tabulates and bryozoans occurred up through 3213’ where they are joined by the first instance of laminar to tabular stromatoporoids. At 3210’ the stromatoporoids become encrusting and solitary rugose corals are first noted at 3209 feet. From 3209 up through Sequence Boundary 2 at 3160 there are mostly encrusting stromatoporoids, massive favositid tabulate corals, branching tabulates (thamnoporids), halysites, auloporids, alveolids?, solitary rugose corals and branching bryozoans. Most of this is found as debris except between 3180’-3181’ where there is a thicket of thamnoporids, a large favositid and an encrusting stromatoporoid; and between 3163’-3161’ where there are encrusting stromatoporoids in place. Immediately above Sequence Boundary 2 at 3159’ there is en encrusting stromatoporoid and massive favositids. The favositids, branching tabulates and bryozoans continue up from 3159’ to 3107’ with several instances of encrusting stromatoporoids and occasional solitary rugose corals and possible halysitids. From 3107’-3106’ the stromatoporoids take on a laminar to tabular form. At 3099’ the stromatoporoids resume the encrusting form up to 3092’. From 3092’ up to Sequence Boundary 3 the fauna is sparce and usually unidentifiable except for a couple of favositids. Above Sequence Boundary 3 at 3051’ there are few identifiable fauna except for a favositid at 3050’. At 3043-3042 there are encrusting and laminar to tabular stromatoporoids. Fauna is again sparce between 3042’-3032’ except for a solitary rugose coral and unidentified and branching tabulates. From 3032’-2995’ there are scattered encrusting stromatoporoids and unidentified encrusters, favositids and a few branching tabulates (thamnoporids?). Of note is the last occurrence of solitary rugose corals at 3027’. Stromatoporoids are laminar to tabular from 2995’-2993’ with some domal to hemispherical forms. At 2992’ the stromatoporoids are smaller and are encrusting. From 2990’-2968 there are no identifiable fauna. From 2967’-2961’ at Sequence Boundary 4 the only identifiable fauna are laminar to tabular cyanobacterial mats. Above Sequence Boundary 4 at 2960’-2956’ are laminar to tabular cyanobacterial mats with hemispherical stromatolites and pieces of stromatolites. From 2949’-2947’ the cyanobacteria form laminar to tabular mats with hemispherical stromatolites. Starting at the top of 2947’ to the top of the core at 2934’, the cyanobacterial mats are more laminar to encrusting with anhydrite destroying fabric.

140

Cement The Jacob 1-36 core is on the interpreted leeward side of Ray Reef. It was expected that, due to less hydraulic energy on the lee side, that there would be less cementation here. The estimated percent of cement identified on the slabbed surface of this core was 13.63%.

In situ vs. Debris The examined slabbed surface of this core was comprised of 39% in situ fossils and 61% debris.

141

Unid Strom Rug Bryz Crinn ug Brach Tabulateab ryz rach Unid Strom T R B Cri B

-2960 2960 SB4

3002 HFSB -3000

-3040 3052 SB3 142

-3080

3118 HFSB -3120

3160 SB2 -3160

-3200 3208 HFSB 3235 HFSB

-3240

160 320 480 640 800 960 1120 1280 Figure 1: Spindle diagram showing the core depth in feet on the Y axis and fauna perimeter on the X axis. The solid lines represent 3rd order sequence boundaries (SB) and the dashed lines represent high frequency sequence boundaries (HFSB) with the footage depth noted to the left. From left to right the fauna measured are Unid=unidentified fauna; Strom=stromatoporoids; Tabulate=tabulate corals; Rug=rugose corals; Bryz=bryozoans; Crin=crinoids; Brach=brachiopods.

Jacob 1-36 Average Perimeter of Fauna Above SB4

Average Perimeter (millimeters) 0 50 100 150 200 250 300 350 2930

2935

2940

2945

Depth (feet) 2950

2955

2960

2965

Stromatoporoid Tabulate Rugose Unidentified Bryozoan Crinoid Brachiopod SB Cyano

Figure 2: Average perimeter of fauna vs. depth above Sequence Boundary 4.

143

Jacob 1-36 Average Perimeter of Fauna Between SB3-SB4

Average Perimeter (millimeters) 0 50 100 150 200 250 300 350 2950.0

2960.0

2970.0

2980.0

2990.0

3000.0

3010.0 Depth (feet) Depth

3020.0

3030.0

3040.0

3050.0

3060.0

Stromatoporoid Tabulate Rugose Unidentified Bryozoan Crinoid Brachiopod SB Cyano

Figure 3: Average perimeter of fauna between SB3 and SB4. 144

Jacob 1-36 Average Perimeter of Fauna Between SB2-SB3

Average Perimeter (millimeters) 0 100 200 300 400 500 600 3040.0

3050.0

3060.0

3070.0

3080.0

3090.0

3100.0

3110.0 Depth (feet) Depth

3120.0

3130.0

3140.0

3150.0

3160.0

3170.0

Stromatoporoid Tabulate Rugose Unidentified Bryozoan Crinoid Brachiopod SB Cyano

Figure 4: Average perimeter of fauna between SB2 and SB3.

145

Jacob 1-36 Average Perimeter of Fauna Below SB2

Average Perimeter (millimeters) 0 50 100 150 200 250 300 350 400 3150.0

3160.0

3170.0

3180.0

3190.0

3200.0

3210.0 Depth (feet) Depth

3220.0

3230.0

3240.0

3250.0

3260.0

Stromatoporoid Tabulate Rugose Unidentified Bryozoan Crinoid Brachiopod SB Cyano

Figure 5: Average perimeter of fauna below SB2.

146

Facies Jacob 1-36 Above SB4 laminar to domal to hemi dendroid robust delicate solitary colonial Ftg. 1 2 3A 3B 4 5 in situ debris encrust tabular or massive branch branch rugose rugose 2934 stromat 2935 stromat stromat stromat stromat stromat 2940 stromat stromat stromat stromat stromat 2945 stromat stromat stromat stromat stromat stromat stromat stromat 2950 Missing Missing Missing

2955 stromat stromat stromat stromat stromat stromat stromat 2960 stromat SB4

Figure 6: Stratigraphic column showing fauna, morphology, and in-situ vs. debris above sequence boundary 4.

147

Facies Jacob 1-36 Between SB3 and SB4 laminar to domal to hemi dendroid robust delicate solitary colonial Ftg. 1 2 3A 3B 4 5 in situ debris encrust tabular or massive branch branch rugose rugose SB4 stromat stromat

2965 stromat stromat stromat

2970

2975

2980

2985

2990 unknown

stromatop stromatop stromatop stromatop 2995 stromatop stromatop

Missing Missing Missing 3000 Missing Missing

(continued)

148

3000 Missing Missing

unknown - nm unknown - nunknown - nm 3005 stromatop unknown

stromatop

unknown - nm 3010 Missing Missing unknown unknown unknown - nm 3015 favositid - rejuv unknown - nm favositid favositid favositid favositid thamno 3020 thamno thamno

3025 favositid unknown thamno stromatop unknown rugose thamno; unknown unknown rugose 3030 exposure? thamno;unknown stromatop thamno;unknown stromatop unknown unknown;stromatop rugose 3035 unknown unknown unknown unknown unknown 3040

stromatop stromatop stromatop unknown 3045 unknown

3050 favositid unknown SB3

Figure 7: Stratigraphic column showing fauna, morphology, and in-situ vs. debris between sequence boundaries 3 and 4. 149

Facies Jacob 1-36 Between SB2 and SB3 laminar to domal to hemi dendroid robust delicate solitary colonial Ftg. 1 2 3A 3B 4 5 in situ debris encrust tabular or massive branch branch rugose rugose SB3

unknown 3055 favositid

favositid 3060 unknown

Missing

3065 unknown unknown

3070 unknown

tab

3075 unknown unknown

3080

bryz unknown 3085 stromatop

3090

stromatop unknown

3095 stromatop; unknown unknown stromatop bryz rugose unknown unknown stromatop 3100

favositid unknown

3105 favositid stromatop unknown bryz stromatop favositid auloporid bryz Missing (continued) 150

3105 favositid stromatop unknown bryz stromatop favositid auloporid bryz Missing Missing 3110 unknown rugose

unknown favositid unknown

3115 Missing Missing Missing

favositid bryz 3120 stromatop favositid bryz bryz; unknown halysites? rugose 3125 thamno; unknown bryz bryz unknown fav? Or aulopori stromatop favositid or halysites rugose 3130 stromatop stromatop unknown stromatop favositid favositid rugose Missing 3135 Missing Missing Missing Missing Missing 3140 stromatop favositid thamno rugose Missing

favositid bryz stromatop favositid thamno bryz 3145

favositid unknown unknown rugose 3150

unknown favositid bryz 3155 favositid favositid tab favositid favositid tab bryz stromatop favositid SB2

Figure 8: Stratigraphic column showing fauna, morphology, and in-situ vs. debris between sequence boundaries 2 and 3. 151

Facies Jacob 1-36 Below SB2 laminar to domal to hemi dendroid robust delicate solitary colonial Ftg. 1 2 3A 3B 4 5 in situ debris encrust tabular or massive branch branch rugose rugose SB2 3160 favositid; stromatop bryz favositid? stromatop stromatop bryz stromatop bryz thamno or emmonsia bryz rugose 3165 unknown tab bryz rugose favositids hamno; auloporids bryz rugose stromatop rugose thamno or emmonsia bryz rugose 3170 tab alveolid; unknown rugose favositids; unknown brz favositid nknown; halysites rugose favositid bryz Missing 3175 stromatop stromatop favositid bryz rugose stromatop stromatop favositid bryz unknown; tab; emmon bryz rugose unknown rugose stromatop bryz 3180 favositid stromatop favositid thamno thickets bryz rugose or tab? emmonsia? unknown bryz rugose Missing stromatop;tab unknown bryz rug or encr tab 3185 stromatop fav; emmonsia bryz rug or encr tab favositid? tab bryz emmonsia? rug or encr tab unknown; emmonsia bryz unknown rug or encr tab 3190 stromatop emmonsia?; thamn bryz rugose in an enc stromatop unknown mmonsia?; thamn bryz rugose? (voids) a unknown bryz tab; unknown - nm bryz unknown bryz 3195 stromatop bryz rugose bryz stromatop thamno; emmonsia bryz tab favositid; bryz tab bryz rugose 3200 stromatop bryz rugose

Missing Missing Missing Mi i (continued)

152

Missing Missing Missing 3205 Missing tab tab bryz tab; unknown bryz stromatop tab tab bryz rugose bryz rugose 3210 stromatop tab bryz tab stromatop tab bryz stromatop tab tab bryz tab 3215 tab tab bryz

tab bryz

tab tab 3220 bryz Missing Missing tab tab bryz unknown bryz 3225 tab bryz; unknown

unknown bryz

3230

3235 bryz bryz

3240

bryz 3245 bryz bryz

favositid; unknown 3250 bryz 3251 favositid bryz

Figure 9: Stratigraphic column showing fauna, morphology, and in-situ vs. debris below sequence boundary 2.

153

brachiopods/gastropo stromatolitesstromatoporoids bryozoans crinoids ds/ostracodes tabulate coralsrugose corals unidentified

Total Faunal Count Number of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of for Phyla Begin ftg. End ftg. Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies Identified 2934 2967.0 5c 97 100 0 0 0 0 0 0 0 97 1 2961.0 SB4 2967.0 2992.0 4 1 13 0 0 0 4 50 0 0 3 38 8 3 2992.0 3002.0 3A 0 13 76 0 0 4 24 0 0 0 17 2 3002.0 3051.0 3B 0 12 3 1 0 77 21 182 50 26 7 13 4 50 14 361 7 SB3 3052.0 3055.0 Exp 0 0 0 2 11 14 78 0 0 2 11 18 3 3055.0 3118.0 3A 0 12 4 10 4 70 25 122 44 17 6 8 3 41 15 280 7 3118.0 3119.0 4 0 0 0 0 0 0 0 0 0 0 3119.0 3160.0 3A 0 13 7 22 12 24 13 56 29 52 27 6 3 17 9 190 7 SB2 3160.0 3165.0 Exp 0 24 36 18 27 9 14 0 9 14 2 3 4 6 66 6 154 3165.0 3167.0 3A 0 0 1 6 0 1 6 14 78 1 6 1 6 18 5 3167.0 3168.0 Exp 0 0 0 0 0 0 2 100 0 2 1 3168.0 3208.0 3A 0 20 2 472 56 26 3 102 12 129 15 46 5 47 6 842 7 3208.0 3218.0 4 0 7 8 7 8 5 6 54 60 15 17 2 2 0 90 6 3218.0 3236.0 3A 0 0 83 25 15 4 152 45 14 4 0 71 21 335 5 3236.0 3238.0 3B 0 0 0 0 0 0 0 0 0 0 3238.0 3243.0 4 0 0 0 0 0 0 0 0 0 0 3243.0 3246.0 3B 0 0 1 25 0 3 75 0 0 0 4 2 3246.0 3251.6 3A 0 0 0 0 0 2 100 0 0 2 1 Whole core totals 98.00 4.21 101.00 4.33 615.00 26.39 228.00 9.79 694.00 29.79 278.00 11.93 80.00 3.43 236.00 10.13 2330

brachiopods/gastropo stromatolites stromatoporoids bryozoans crinoids ds/ostracodestabulate corals rugose corals unidentified

Total Faunal Count Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of for Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies 5c 97 100 0 0 0 0 0 0 0 97 4 1 1 7 7 7 7 5 5 58 59 15 15 2 2 3 3 98 3B 0 12 3 2 1 77 21 185 51 26 7 13 4 50 14 365 3A 0 58 3 588 35 135 8 437 26 228 14 61 4 177 11 1684 Exp 0 24 28 18 21 11 13 14 16 9 10 4 5 6 7 86 Whole core totals 98.00 4.21 101.00 4.33 615.00 26.39 228.00 9.79 694.00 29.79 278.00 11.93 80.00 3.43 236.00 10.13 2330 Table 5: Relative abundance and diversity when the sum of all fauna equals 100 percent.

brachiopods/gastro stromatolitesstromatoporoids bryozoans crinoids pods/ostracodes tabulate corals rugose corals unidentified

Percent Percent Percent Percent Percent Percent Percent Sum of Percentage Percent of total Percent of total Percent of total Percent of total Percent Percent of Percent of total Percent of total Percent of total facies of facies Total of facies core of facies core of facies core of facies core of facies total core of facies core of facies core of facies core area area percent surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface covered covered by area (ft x Begin ftg. End ftg. Facies area area area area area area area area area area area area area area area area by fauna fauna 100) 2934 2967.0 5c 370 12.337 0 0.000 0 0.000 0 0.000 0 0.000 0 0.000 0 0.000 0 0.000 370 12.337 3000 2961.0 SB4 #DIV/0! #DIV/0! 2967.0 2992.0 4 4 0.149 0 0.000 0 0.000 0 0.000 0 0.004 0 0.000 0 0.000 0 0.007 4 0.160 2500 2992.0 3002.0 3A 0 0.000 91 18.150 0 0.000 0 0.000 0 0.078 0 0.000 0 0.000 0 0.000 91 18.229 500 3002.0 3051.0 3B 0 0.000 19 0.386 0 0.001 4 0.075 14 0.295 46 0.930 0 0.009 9 0.191 92 1.887 4900 SB3 #DIV/0! #DIV/0! 3052.0 3055.0 Exp 0 0.000 0 0.000 0 0.000 0 0.009 0.2 0.076 0 0.000 0 0.000 0 0.045 0.4 0.131 300 3055.0 3118.0 3A 0 0.000 5 0.082 0 0.007 10 0.176 45 0.785 12 0.218 1 0.013 4 0.066 77 1.345 5700 3118.0 3119.0 4 0.000 0 0.000 0 0.000 5 5.000 2 2.000 0 0.000 0 0.000 0 0.000 7 7.000 100 3119.0 3160.0 3A 0 0.000 35 1.075 2 0.069 3 0.086 7 0.209 90 2.715 1 0.042 2 0.046 140 4.243 3300 SB2 #DIV/0! #DIV/0! 3160.0 3165.0 Exp 0 0.000 8 1.567 1 0.119 0 0.047 0 0.000 3 0.590 0 0.089 0 0.027 12 2.438 500 3165.0 3167.0 3A 0 0.000 0 0.000 0 0.026 0 0.000 0 0.051 8 3.802 0 0.023 0 0.178 8 4.079 200 3167.0 3168.0 Exp 0 0.000 0 0.000 0 0.000 0 0.000 0 0.000 0 0.000 2 1.627 0 0.000 2 1.627 100 155 3168.0 3208.0 3A 0 0.000 65 1.871 10 0.279 1 0.016 5 0.147 38 1.093 44 1.244 7 0.202 170 4.851 3500 3208.0 3218.0 4 0 0.000 10 1.041 104 10.422 109 10.909 6 0.557 12 1.201 1 0.066 0 0.000 242 24.197 1000 3218.0 3236.0 3A 0 0.000 0 0.000 8 0.488 1 0.092 4 0.249 18 1.135 0 0.000 3 0.171 34 2.136 1600 3236.0 3238.0 3B 0 0.000 0 0.000 2 1.000 3 1.500 2 1.000 0 0.000 0 0.000 0 0.000 7 3.500 200 3238.0 3243.0 4 0 0.000 0 0.000 0 0.000 0 0.000 0 0.000 0 0.000 0 0.000 0 0.000 0 0.000 500 3243.0 3246.0 3B 0 0.000 0 0.000 0 0.000 1 0.333 0 0.000 0 0.000 0 0.000 0 0.000 1 0.333 300 3246.0 3251.6 3A 0 0.000 0 0.000 1 0.167 20 3.333 0 0.000 0 0.000 0 0.000 0 0.000 21 3.500 600 Whole core totals 373.81 1.30 233.53 0.81 128.17 0.45 156.88 0.54 85.62 0.30 226.56 0.79 48.90 0.17 25.21 0.09 1279 4.440 28800

brachiopods/gastro stromatolites stromatoporoids bryozoans crinoids pods/ostracodes tabulate corals rugose corals unidentified

Table 6: Density of fauna when the total area of the slabbed core surface equals 100 percent.

Appendix C

PERCY 2-2 (PN25100) RESULTS AND SUPPORTING TABLES AND FIGURES

156

Percy 2-2 Results

Relative Abundance: Framework Density, Reef-Builder Diversity, and Composition of Reef-Builder Assemblages

Relative Abundance Analysis of the proportion of high level categories of fauna, when the sum of all fauna equaled 100 percent, showed that the most numerous faunal categories were stromatoporoids and unidentified fauna (see Tables 1 & 5). The frame-builders were represented by stromatoporoids, unidentified fauna, and tabulate corals only. No rugose corals were identified. Among the non-framebuilders, bryozoans and crinoids were the most numerous. Brachiopods were not identified in the studied core.

Percent of Population Faunal Category (when sum of all fauna equals 100%) Stromatoporoids 54.42 Unidentified 38.94 Tabulate corals 2.65 Bryozoans 2.65 Crinoids 1.33 Brachiopods 0 Stromatolites and cyanobacteria 0 Rugose corals 0 Table 1: Percent of population contributed by each faunal category.

Reef-Builder Diversity Faunal diversity, as expressed by the number of faunal categories represented, is summarized in Tables 2 & 5. Diversity was highest in the Restricted and Reef Core Facies with 3 faunal categories represented. The Reef Core Facies and Restricted Facies had similar representation of faunal categories. The Reef Debris Facies had lower representation of faunal categories.

Number of Faunal Categories Facies Represented Restricted Facies 5a and 5b 3, 3, 0 Reef Core Facies 3A 3, 3 Reef Debris Facies 3B 1, 2 Table 2: Number of faunal categories represented in each facies (a coarse indicator of diversity).

Framework Density When analyzed according to the percentage of the slabbed core surface that was covered by fauna, the total area covered was 1.8% of the 54.5 feet of studied core 157

(Tables 3 & 6). Stromatoporoids had the highest percentage of coverage with 1.43%. Unidentified fauna, tabulate corals, bryozoans, and crinoids all had .04% or less coverage.

Faunal Category Percent of Slabbed Core Surface Coverage Stromatoporoids 1.43 Unidentified 0.35 Tabulate corals 0.04 Bryozoans 0.01 Crinoids 0.002 Stromatolites 0 Brachiopods 0 Rugose corals 0 Table 3: Density of faunal categories as a percentage of slabbed core surface coverage.

When analyzed by facies (Tables 4 & 6), the Reef Core Facies 3A had the highest coverage with stromatoporoids occupying 5.41% of 7.5 feet. The Restricted Facies provided 1.36% coverage and the Reef Debris Facies totaled 0.059% coverage.

Facies Faunal Categories with Most Coverage Restricted Facies 5 Stromatoporoids 1.26 % of total 1.36 % of facies coverage (29.5ft.) Reef Debris Facies 3B 0.058% tabulate coral of total .059% of facies coverage (17.5 ft.) Reef Core Facies 3A Stromatoporoids 5.41% of total 7.74% of facies coverage (7.5 ft.) Table 4: Faunal category coverages per facies.

Composition of reef-building assemblages and distribution The Percy 2-2 core contains 54 feet of Wenlockian strata from Sequence Boundary 3 to Sequence Boundary 4. It contains Reef Core, Reef Debris, and Restricted Facies. Fauna in this core is sparse and mostly clumped between 3237- 3223 feet. Fauna is neither abundant nor diverse. There is a probable halysitid tabulate coral at 3248 feet which is the first identifiable fossil. There is also a tabulate at 3234 feet which is probably an alveolitid. Stromatoporoids are first identified at 3236 feet in a massive form. From 3229 feet up to 3226 feet, laminar to tabular stromatoporoids and branching bryozoans are present. The stromatoporoids take an encrusting form at 3226 feet. There was no fauna identifiable from 3223 to Sequence Boundary 4 at 3198 feet.

158

Cement The Percy 2-2 contained 12.2% cement and was mostly debris (16% in situ vs. 84% debris).

159

m z y UnidUnid StromStro Tab Rug Br CrinBrach -3198 Tabulate Bryz Brach

-3201 3198 SB4

-3204

-3207

-3210

-3213

-3216

-3219 160 -3222 3223 HFSB

-3225

-3228

-3231 -3234 3238 HFSB -3237

-3240

-3243

-3246 3252 SB3 -3249 200 400 600 800 1000 1200 1400 1600 Figure 1: Spindle diagram showing the core depth in feet on the Y axis and fauna perimeter on the X axis. The solid lines represent 3rd order sequence boundaries (SB) and the dashed lines represent high frequency sequence boundaries (HFSB) with the footage depth noted to the left. From left to right the fauna measured are Unid=unidentified fauna; Strom=stromatoporoids; Tabulate=tabulate corals; Rug=rugose corals; Bryz=bryozoans; Crin=crinoids; Brach=brachiopods.

Percy 2-1 Average Perimeter of Framebuilders Between SB3-SB4 Average Perimeter (millimeters) 0 100 200 300 400 500 600 700 3195 3200 3205 3210 3215 3220 3225 3230 Depth (feet) Depth 3235 3240 3245 3250 3255

Unidentified Stromatoporoid Tabulate Rugose SB

Figure 2: Average perimeter of frame-building fauna vs. depth between Sequence Boundaries 3 and 4. Note the absence of rugose corals. There are also no cyanobacteria/stromatolites identified.

161

Percy 2-2 Average Permimeter of Nonframebuilders Between SB3-SB4 Average Perimeter (millimeters) 0 20 40 60 80 100 120 140 160 180 3195 3200 3205 3210 3215 3220 3225 3230 Depth (feet) 3235 3240 3245 3250 3255

Brachiopod Bryozoan Crinoid SB

Figure 3: Average perimeter of nonframe-building fauna vs. depth between sequence boundaries 3 and 4. Note the absence of identified brachiopods.

162

Facies Percy 2-2 Leeward SB 3 to 4 dendroid laminar to domal to hemi or robust delicate solitary colonial Ftg. 1 2 3A 3B 4 5 in situ debris encrust tabular massive branch branch rugose rugose SB4

3200

3205

3210

3215

3220

unknown unknown unknown bryz unknown unknown 3225 unknown unknown stromatop stromatop stromatop stromatop bryz stromatop unknown bryz 3230

tab 3235 unknown unknown stromatop unknown unknown

3240

3245

tab

3250

3252 SB3

Figure 4: Stratigraphic column showing fauna, morphology, and in-situ vs. debris between Sequence Boundaries 3 and 4. 163

Percy 2-2 Average Perimeter of Fauna Between SB3-SB4

Average Perimeter (millimeters) 0 100 200 300 400 500 600 700 3195 3200 3205 3210 3215 3220 3225 3230

Depth (feet) Depth 3235 3240 3245 3250 3255

Stromatoporoid Tabulate Rugose Unidentified Bryozoan Crinoid Brachiopod SB Cyano

Figure 5: Average perimeter of all fauna between Sequence Boundary 3 and Sequence Boundary 4. Note total absence of rugose corals, brachiopods, and cyanobacteria/stromatolites.

164

brachiopods/gastro stromatolites stromatoporoids bryozoans crinoids pods/ostracodes tabulate corals rugose corals unidentified Total Faunal Number of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Count for Phyla Begin ftg. End ftg. Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies Identified SB4 3198 3212 5b 0 0 0 0 0 0 0 0 0 0 3212 3224.5 5a 0 49 83 1 2 0 0 0 0 9 15 59 3 3224.5 3230 3A 0 49 83 5 8 0 0 0 0 5 8 59 3 3230 3235.5 3B 0 0 0 0 0 5 100 0 0 5 1 3236 3238 3A 0 25 25 0 0 0 1 1 0 74 74 100 3 3238 3241 5 0 0 0 0 0 0 0 0 0 0 3241 3253 3B 0 0 0 3 60 0 2 40 0 0 5 2 SB3 Whole core totals 0 0.00 123 53.95 6 2.63 3 1.32 0 0.00 8 3.51 0 0.00 88 38.60 228 165

brachiopods/gastro stromatolites stromatoporoids bryozoans crinoids pods/ostracodes tabulate corals rugose corals unidentified Total Faunal Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Count for Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies SB4 5 0 49 83 1 2 0 0 0 0 9 15 59 3B00033007700010 3A 0 74 47 5 3 0 0 1 1 0 79 50 159 SB3 Whole core totals 0 0.00 123 53.95 6 2.63 3 1.32 0 0.00 8 3.51 0 0.00 88 38.60 228

Table 5: Relative abundance and diversity when the sum of all fauna equals 100 percent.

pg p stromatolites stromatoporoids bryozoans crinoids /ostracodes tabulate corals rugose corals unidentified Percentage Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Sum of of facies Total facies total core facies total core facies total core facies total core facies total core facies total core facies total core facies total core facies area area percent Begin End surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface covered by covered by area (ft x ftg. ftg. Facies area area area area area area area area area area area area area area area area fauna fauna 100) SB4 3198 3212 5b 0 0.00 0 0.00 0 0.000 0 0.000 0 0.000 0 0.000 0 0.000 0 0.00 0.00 0.00 1400 3212 3225 5a 0 0.00 37.20 2.98 0.05 0.004 0 0.000 0 0.000 0 0.000 0 0.000 2.88 0.23 40.13 3.21 1250 3225 3230 3A 0 0.00 37.41 6.80 0.35 0.06 0 0.000 0 0.000 0 0.000 0 0.000 7.6 1.38 45.36 8.25 550 3230 3236 3B 0 0.00 0 0.00 0 0.000 0 0.000 0 0.000 0.91 0.17 0 0.000 0 0.00 0.91 0.17 550 3236 3238 3A 0 0.00 3.17 1.59 0 0.000 0 0.000 0 0.000 0.98 0.49 0 0.000 8.54 4.27 12.69 6.35 200 3238324150 0.000 0.0000.00000.00000.00000.00000.0000 0.000.000.00300 3241 3253 3B 0 0.00 0 0.00 0 0.000 0.01 0.00001 0 0.000 0.11 0.01 0 0.000 0 0.00 0.12 0.01 1200 SB3 Whole core totals 0.00 0.00 77.78 1.43 0.40 0.01 0.01 0.0002 0.00 0.000 2.00 0.04 0.00 0.000 19.02 0.35 99.21 1.82 5450 166

pg p stromatolites stromatoporoids bryozoans crinoids /ostracodes tabulate corals rugose corals unidentified Percentage Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Sum of of facies Total facies total core facies total core facies total core facies total core facies total core facies total core facies total core facies total core facies area area percent surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface covered by covered by area (ft x Facies area area area area area area area area area area area area area area area area fauna fauna 100) SB4 5 0 0.00 37.20 1.26 0.1 0.002 0 0.00 0 0.00 0 0.000 0 0.00 2.88 0.10 40.13 1.360 2950 3B 0 0.00 0.00 0.00 0.0 0.00 0.01 0.001 0 0.00 1.02 0.058 0 0.00 0.00 0.00 1.03 0.059 1750 3A 0 0.00 40.58 5.41 0.4 0.05 0 0.00 0 0.00 0.98 0.131 0 0.00 16.14 2.15 58.05 7.740 750 SB3 Whole core totals 0.00 0.00 77.78 1.43 0.40 0.01 0.01 0.0002 0.00 0.00 2.00 0.04 0.00 0.00 19.02 0.35 99.21 1.820 5450

Table 6: Density of fauna when the total area of the slabbed core surface equals 100 percent.

Appendix D

BUSCH-TUBBS-KUHLMAN 1-36 (PN25203) RESULTS AND SUPPORTING TABLES AND FIGURES

167

Busch-Tubbs-Kuhlman 1-36 Results

Relative Abundance: Framework Density, Reef-Builder Diversity, and Composition of Reef-Builder Assemblages

Relative Abundance Analysis of the proportion of high level categories of fauna, when the sum of all fauna equaled 100 percent, showed that the most numerous faunal categories were bryozoans, crinoids, brachiopods, and tabulate corals (Tables 1 & 5). The frame-builders were represented by tabulate corals, stromatoporoids, unidentified fauna and rugose corals. Among the non-framebuilders, bryozoans, crinoids, and brachiopods were the first, second, and third most abundant fauna, respectively. Cyanobacteria/stromatolites were the least abundant with far less than 1 %.

Percent of Population Faunal Category (when sum of all fauna equals 100%) Bryozoans 40.10 Crinoids 19.00 Brachiopods 13.25 Tabulate corals 12.74 Stromatoporoids 5.63 Unidentified 5.14 Rugose corals 4.01 Stromatolites and cyanobacteria 0.12 Table 1: Percent of population contributed by each faunal category.

Reef-Builder Diversity Faunal diversity, as expressed by the number of faunal categories represented, is summarized in Tables 2 & 5. Diversity was highest in the Reef Core Facies 3A with up to 8 categories of fauna represented and the Bioherm Core Facies 2 with 7 categories represented. Exposure Surfaces, Flooding Surfaces, and the Reef Debris Facies had medium representation with 3 to 5 categories represented. The Restricted Facies 5 had the lowest diversity with only 2 categories represented. Tabulate corals were represented by favosities, auloporids, aulocysts and halysites, and emmonsia types and thamnoporid types.

Facies Number of Faunal Categories Represented Exposure Surface 3 Flood Surface 3, 0, 0, 4, 5 Restricted Facies 5 2 Reef Debris Facies 3B 4 Reef Core Facies 3A 3, 8, 8, 8, 3, 6, 6, 6, 7, 5, 6, 7 Bioherm Core Facies 2 7, 7 168

Table 2: Number of faunal categories represented in each facies (a coarse indicator of diversity).

Framework Density When analyzed according to the percentage of the slabbed core surface that was covered by fauna, the total area covered was 10.58% of the 311 feet of studied core. Stromatoporoids had the highest percentage of coverage with 4.72% (Tables 3 & 6). Tabulate corals and crinoids had almost 2% coverage each. All other faunal categories had 0.66 % or less coverage.

Faunal Category Percent of Slabbed Core Surface Coverage Stromatoporoids 4.72 Tabulate corals 1.93 Crinoids 1.78 Bryozoans 0.66 Unidentified 0.55 Rugose corals 0.49 Stromatolites 0.35 Brachiopods 0.11 Table 3: Density of faunal categories as a percentage of slabbed core surface coverage.

When analyzed by facies, the Flooding Surface and the Reef Core Facies had the highest coverages with 15.6% in 3.35 feet of core and 13.11% in 207 feet of core, respectively (Tables 4 & 6). The Skeletal Grainstone Facies had the second highest coverage with 5% in 47 feet. The Exposure Surfaces provided 3.6% coverage in 27 feet. The Reef Debris Facies provided 1.3% coverage in 5 feet and the Restricted Facies provided 1.5% coverage in 21 feet.

Facies Faunal Categories with Most Coverage Reef Debris Facies 3B 24.5 % (2.6 ft.) – stromatoporoids 22.5%, unid Flooding Surface 15.6 % (3 ft.) – stromatoporoids 13%, crinoids Reef Core Facies 3A 13% (207 ft.) – stromatoporoids 6.6%, tabs 2.6%, crinoids 2.5%, rugose 0.7% Bioherm Core Facies 2 5% (47 ft.) – 2% bryozoans, 1.3% tabs Exposure Surface 3.6% (27 ft.) – cyano (2%), stromatoporoids (1.4%) Restricted Facies 5c 1.5% (21 ft.) – cyano 1%, unid .45% Table 4: Faunal category coverages per facies.

Composition of reef-building assemblages and distribution

169

Faunal density below Sequence Boundary 2 for the BTK core shows a Bioherm Facies and a Reef Core Facies indicating the establishment of the reef. However, the BTK core also has a flooding surface. Below SB2, faunal density for the Bush-Tubbs-Kuhlman (BTK) core included three shallowing upward high frequency sequences that showed community replacement of encrusting and branching bryozoans, thamnoporids, aulocytids, to laminar to massive tabulate corals, favositids, rugose corals, to encrusting and laminar to tabular stromatoporoids and domal smooth enveloped stromatoporoids. Between SB2 and SB3, there is one HFSB. From SB2 to the HFSB, there are branching bryozoans, thamnoporids, encrusting and laminar to tabular tabulate corals, encrusting, laminar to tabular and domal stromatoporoids. Ragged stromatoporoids are also noted in two places indicating higher energy and partial mortality of stromatoporoids due to smothering by sediment. From the HFSB to SB3, branching bryozoans, thamnoporids, alveolitids, rugose corals, and encrusting stromatoporoids are replaced by laminar to tabular and domal stromatoporoids near SB3. Above SB3, the BTK core goes from having only a Reef Core Facies to having Reef Core, Reef Debris, and Restricted Facies as well as an exposure and flooding surface. The BTK Reef Core Facies is diverse with a high density of stromatoporoids (>6%). The presence of both stromatoporoids and cyanobacterial mats in the exposure surface shows the rapidity of the facies transition. The BTK core includes one HFSB above SB3. From SB3 to the HFSB consists mostly of branching bryozoans, thamnoporids, and encrusting stromatoporoids. It is not until 3093 feet that favositids, auloporids, aulocytids, rugose corals, and domal stromatoporoids are seen. Stromatoporoids then go back to an encrusting form and multiple rugose corals are clustered until 3078 feet where favositids and laminar to tabular stromatoporoids are again encountered and rugose corals persist. At 3068 feet a colonial rugose (Fletcheria sp) is noted along with aulocytids and thamnoporids. The fauna then thins out and a hardground is located just before the HFSB. There is also core above the HFSB at 3057 feet to 2953 feet. The first fauna noted is branching bryozoans, solitary rugose corals, aulocytids, and more colonial rugose corals (Fletcheria sp.) which continue up to where encrusting stromatoporoids and favositids are noted. At 3050 feet the stromatoporoids and favositids are gone and replaced with solitary rugose corals and auloporid thickets. At 3042 and 3038 feet favositids are again seen along with solitary rugose corals and aulocytids and branching bryozoans. Above 3038 feet, only solitary rugose corals and aulocytids are seen until 3023 feet when favositids return and a laminar to tabular stromatoporoid is noted at 3016 feet. Cyanobacteria are the only fauna encountered between 3010-2998 feet, mostly as debris. Laminar to tabular stromatoporoids reappear at 2989 and continue with regularity to 2974 feet where they are domal to massive. From 2973-2962 feet no fauna are seen. Cyanobacteria are noted at 2961 feet, taking on hemispherical stromatolitic forms at 2956 feet, and continue to the top of the core.

170

Cement The BTK 1-36 core is on the interpreted crest of Ray Reef. The estimated percent of cement identified on the slabbed surface of this core was 21%.

In-situ vs. Debris The examined slabbed surface of this core was comprised of 16% in situ fossils and 84% debris.

171

m ose d bulate Unidni Stromtro Tabulatea Rugug Bryz Crin Brachrach U S T R Bryozoan Crinoid B -2960

-2980 2990 HFSB -3000

-3020

-3040 3058 HFSB -3060

-3080

3100 -3100 SB3

-3120 CoreCore Depth Depth (ft.) (ft.) 3128 HFSB

172 -3140

-3160 3175 SB2 -3180 3189 HFSB

-3200 3204 HFSB

-3220

-3240 3264 HFSB -3260 120 240 360 480 600 720 840 960 1080 Average Perimeter (mm)

Figure 1: Spindle diagram showing the core depth in feet on the Y axis and fauna perimeter on the X axis. The solid lines represent 3rd order sequence boundaries (SB) and the dashed lines represent high frequency sequence boundaries (HFSB) with the footage depth noted to the left. From left to right the fauna measured are Unid=unidentified fauna; Strom=stromatoporoids; Tabulate=tabulate corals; Rug=rugose corals; Bryz=bryozoans; Crin=crinoids; Brach=brachiopods.

BTK 1-36 Average Perimeter of Fauna

Average Perimeter (millimeters) 0 100 200 300 400 500 600 700 800 2950

2960

2970

2980

2990

3000

3010

3020

3030

3040

3050

3060

3070

3080

3090

3100

3110

Depth (ft) 3120

3130

3140

3150

3160

3170

3180

3190

3200

3210

3220

3230

3240

3250

3260

3270

Stromatoporoid Tabulate Rugose Unidentified Bryozoan Crinoid Brachiopod SB Cyano

Figure 2: Average perimeter of all fauna vs. depth of studied core.

173

BTK 1-36 Average Perimeter of Fauna Above SB3

Average Perimeter (millimeters) 0 50 100 150 200 250 300 2940

2950

2960

2970

2980

2990

3000

3010

3020

Depth (ft) Depth 3030

3040

3050

3060

3070

3080

3090

3100

3110

Stromatoporoid Tabulate Rugose Unidentified Bryozoan Crinoid Brachiopod SB Cyano

Figure 3: Average perimeter of fauna vs. depth above Sequence Boundary (SB) 3.

174

BTK 1-36 Average Perimeter of Fauna Between SB2-SB3

Average Perimeter (millimeters) 0 50 100 150 200 250 300 350 3100

3110

3120

3130

3140 Depth (ft)

3150

3160

3170

3180

Stromatoporoid Tabulate Rugose Unidentified Bryozoan Crinoid Brachiopod SB Cyano

Figure 4: Average perimeter of all faunal categories vs. depth between Sequence Boundaries 2 and 3. 175

BTK 1-36 Average Perimeter of Fauna Below SB2

Average Perimeter (millimeters) 0 50 100 150 200 250 300 350 400 3170

3180

3190

3200

3210

3220 Depth (ft)

3230

3240

3250

3260

3270

Stromatoporoid Tabulate Rugose Unidentified Bryozoan Crinoid Brachiopod SB Cyano

Figure 5: Average perimeter of all faunal categories vs. depth below Sequence Boundary 2. 176

Facies Busch-Tubbs-Kuhlman 1-36 Above SB3 dendroid laminar to domal to hemi or robust solitary colonial Begin ftg. SB 1 2 3A 3B 4 5 in situ debris encrust tabular massive branch delicate branch rugose rugose 2953 2954 cyano cyano 2955 cyano cyano unid bryz/unid 2956 cyano cyano hemi unid 2957 cyano cyano 2958 2959 2960 2961 cyano cyano 2962 2963 2964 2965 2966 2967 2968 missing 2969 2970 2971 2972 missing 2973 missing 2974 2974.4 strom strom/unid 2975 strom strom 2976 strom strom 2977 unid unid 2978 strom strom bryz/unid 2978.8 2979 strom strom 2980 missing 2981 missing 2982 missing 2983 bryz/strom strom 2984 ???? 2985 ???? 2986 missing 2987 missing 2988 2989 2989.1 strom 2990 unid 2991 missing 2992 missing 2993 missing 2994 missing 2995 missing 2996 missing 2997 missing 2998 cyano unid unid 2999 3000 3001 cyano cyano 3002 cyano cyano 3003 missing 3004 (continued)

177

3003 missing 3004 3005 cyano cyano 3006 3007 cyano cyano 3008 3009 3010 cyano cyano 3011 3012 missing 3013 missing 3014 missing 3015 missing 3016 3016.3 strom unid 3017 unid small 3018 bryz 3019 3020 cyano favositid bryz/chain tab not halysites 3021 chain tab - aulocystis? 3022 favosites bryz/thamno 3023 favositid/unid bryz/unid 3024 chain tab - aulocystis? 3025 bryz 3026 missing 3027 missing 3028 missing 3029 missing 3030 aulocysts small 3031 small 3032 aulocysts 3033 aulocysts 3034 aulocysts 3035 3036 missing 3037 unid small 3038 favositid bryz 3039 tab aulocysts med 3040 unid aulocysts/bryz 3041 aulocysts 3042 favositid/emmonsia thamno/bryz/aulocysts 3043 thamno/bryz med 3044 aulocysts/thamno/med-lrge 3045 aulocysts - rose small 3046 auloporid thicket! 3047 auloporid thickesmall-med 3048 unid small&med 3049 aulocysts large 3050 aulocysts/unid large 3051 strom favositid aulocysts 3052 unid 3053 strom unid bryz/aulocysts fletch 3054 strom small 3055 bryz aulocysts large fletch

(continued)

178

yy 3054 strom small 3055 bryz aulocysts large fletch

3056 fletch 3057 bryz 3057.8 3058 hardground 3059 bryz 3060 3061 bryz/thamno/unid 3062 thamno 3062.5 3063 3064 3065 thamno large 3066 thamno 3067 thamno/aulocysts 3068 aulocysts fletch 3069 missing 3070 missing 3071 strom aulocysts/unidsmall-med 3072 unid small-med 3073 strom strom unid large 3074 strom strom aulocysts/unid small 3075 strom strom unid small 3076 strom strom auloporid? 3077 3078 favo lingulids??!! 3079 strom aulocysts;bryzsmall-med 3080 strom/unid unid med-large 3081 aulocysts small-med 3082 strom unid small-med 3083 bryz/unid 3084 strom tab unid small 3085 strom unid 3086 aulocysts/unid medium 3087 strom unid medium 3088 bryz/unid medium 3089 strom strom hemi aulocysts/unid/bryz/t thamno? 3090 strom aulocysts/bryz/unid 3091 unid unid 3092 favositid (auloporid?) favo unk med 3093 strom favo 3094 strom 3095 strom 3096 strom bryz 3097 strom thamno? 3098 strom bryz/unid 3099 bryz 3099.6 unid-cyano? 3100 cyano 3100.5 3

Figure 6: Stratigraphic column showing fauna, morphology, and in-situ vs. debris for studied core above SB3.

179

Facies Busch-Tubbs-Kuhlman 1-36 Between SB2-SB3 dendroid robust solitary colonial Begin ftg. SB 1 2 3A 3B 4 5 in situ debris encrust laminar to tabular domal to hemi or massive branch delicate branch rugose rugose 3100.5 3 3100.5 strom-hemi bryz/unid 3101 strom strom-hemi bryz/unid/thamno 3102 strom alveolites? bryz small 3103 strom strom bryz/thamno/alveolites?/unid 3104 strom bryz/thamno 3105 unid 3106 strom strom-hemi unid large&sm 3107 missing 3108 missing 3109 bryz/thamno/unid 3110 bryz/thamno/unid 3111 missing 3112 bryz/thamno 3113 strom strom/unid bryz/thamno 3114 strom bryz/alveolites?/unid 3115 3116 strom/unid 3117 strom bryz 3118 bryz/thamno/unid 3119 strom strom bryz/thamno/unid 3120 bryz/unid 3121 bryz/unid 3122 strom tab bryz/unid 3123 strom bryz/unid 3124 alveolites? bryz/thamno 3125 tab-alveolites? bryz/unid 3126 tab-alveolites? bryz/unid 3127 bryz/unid 3128 bryz 3128.5 HF 3128.6 cyano 3129 cyano/strom 3130 strom-ragged domal unid unid 3131 bryz/unid 3132 bryz/unid 3133 bryz/unid/strom-stachyodes? 3134 bryz/unid/strom-stachyodes? 3135 bryz/unid 3136 bryz (continued)

180

3134 bryz/unid/strom-stachyodes? 3135 bryz/unid 3136 bryz 3137 unid bryz/unid 3138 bryz 3139 strom-ragged hemi bryz/unid 3140 unid bryz 3141 bryz/unid 3142 bryz/unid 3143 bryz/unid 3144 bryz 3145 strom bryz 3146 bryz 3147 bryz 3148 bryz large 3149 bryz 3150 bryz/thamno 3151 bryz/thamno 3152 bryz emmonsia type thamno 3153 missing 3154 missing 3155 strom bryz/thamno 3156 unid bryz 3157 tab 3158 tab 3159 tab tab 3160 tab emmonsia type/unid thamno 3161 tab tab thamno 3162 tab tab-alveolites? thamno 3163 tab unid 3164 tab alveolites? thamno/unid 3165 alveolites? thamno 3166 missing 3167 bryz 3168 alveolites? thamno/unid 3168.8 strom-hemi 3169 strom alveolites? bryz/unid 3170 3171 strom strom 3171.3 3172 unid bryz/thamno/unid 3173 unid bryz/unid 3174 3174.2 3174.5 2 Figure 7: Stratigraphic column showing fauna, morphology, and in-situ vs. debris for studied core between SB2 and SB3.

181

Facies Busch-Tubbs-Kuhlman 1-36 Below SB2 dendroid robust solitary colonial Begin ftg. SB 1 2 3A 3B 4 5 in situ debris encrust laminar to tabular domal to hemi or massive branch delicate branch rugose rugose 3174.5 2 3174.5 alveolites? thamno 3175 alveolites? thamno 3176 strom bryz/tab/auloporid not marked small 3177 tab bryz/tab 3178 tab alveolites? bryz 3179 strom alveolites? bryz/thamno 3180 strom bryz small 3181 strom bryz/thamno 3182 alveolites? bryz 3183 bryz/unid alveolites? bryz/thamno 3184 alveolites? Or strom? bryz 3185 alveolites? Or strom? unid bryz/thamno 3186 3187 bryz 3188 alveolites? Or strom? thamno thicket 3188.75 3189 HF 3189.6 unid unid 3190 unid alveolites? bryz 3191 3191.6 bryz 3192 alveolites? bryz 3193 tab alveolites or strom? bryz 3194 bryz unid bryz 3195 bryz/strom alveolites?/unid bryz 3196 strom 3197 strom alveolites or strom? bryz 3198 bryz 3199 strom strom tab bryz 3200 3201 unid 3202 unid strom 3203 missing 3203.5 3204 HF 3204.7 strom strom-hemi enveloped/unid bryz 3205 strom strom-hemi enveloped 3206 strom strom strom bryz/thamno 3207 strom unid bryz/thamno 3208 unid bryz/thamno 3209 strom strom unid bryz/thamno small 3210 strom bryz/thamno 3211 bryz/thamno 3212 bryz/thamno/halysites large 3213 tab bryz/thamno 3214 tab bryz/thamno med 3215 tab strom tab-alveolites? bryz med 3216 strom/bryz alveolites? med 3217 bryz/thamno/unid med 3217.2 (continued)

182

y 3217 bryz/thamno/unid med 3217.2 3218 alveolites? bryz/thamno 3219 missing 3220 missing 3221 strom bryz 3222 bryz 3223 bryz bryz/thamno 3224 missing 3225 missing 3226 missing 3227 missing 3228 tab-alveolites? 3229 strom bryz/halysites large 3230 bryz/unid 3231 tab bryz 3232 unid bryz 3233 tab bryz 3234 bryz bryz/thamno? 3235 bryz 3236 bryz bryz/thamno 3237 bryz bryz/thamno 3238 bryz 3239 bryz bryz 3240 3240.35 bryz 3241 tab bryz 3242 bryz/tab 3243 bryz/tab/aulocysts 3244 bryz/tab/aulocysts med 3245 bryz/unid med 3246 alveolites? bryz/unid 3247 bryz 3248 3248.25 bryz 3249 bryz 3250 bryz strom/unid 3251 tab bryz 3252 bryz/unid 3253 strom/alveolites? bryz 3254 favo bryz 3255 bryz 3255.5 3256 bryz/thamno/tab-aulocysts 3257 bryz 3258 bryz/aulocysts 3259 bryz/unid 3260 tab bryz 3261 bryz/thamno med 3262 tab bryz/thamno 3263 unid 3264 bryz bryz

Figure 8: Stratigraphic column showing fauna, morphology, and in-situ vs. debris for studied core below SB2.

183

pg stromatolites stromatoporoids bryozoans crinoids pods/ostracodes tabulate corals rugose corals unidentified Total Faunal Number of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Count for Phyla Begin ftg. End ftg. Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies Identified 2953 2974.4 5 5 0.22 0 0.00 0 0.00 0 0.00 0 0.00 0 0.00 0 0.00 0 0.10 5 2 2974.4 2989.1 3a 0 0.00 5 4.04 1 0.01 0 0.00 0 0.00 0 0.00 0 0.00 0 0.18 6 3 2989.1 3016.3 Exp 4 0.58 0 0.39 0 0.00 0 0.00 2 0.00 0 0.00 0 0.00 0 0.01 6 3 3016.3 3057.8 3a 1 0.01 1 0.09 46 0.07 11 0.24 2 0.01 9 0.59 1 0.41 8 0.10 79 8 3057.8 3062.5 3b 0 0.00 0 0.00 43 0.04 0 0.00 29 0.01 6 0.00 0 0.00 6 0.01 84 4 3062.5 3099.6 3a 1 0.05 134 1.86 27 0.01 202 0.40 48 0.00 98 0.79 149 0.30 120 0.11 779 8 3099.6 3100.5 Flood Surf 1 0.00 4 0.00 3 0.00 3 SB3 3100.5 3128.5 3a 2 0.11 315 4.87 244 0.10 500 1.10 304 0.02 313 1.84 306 0.69 370 0.35 2354 8 3128.5 3128.6 Flood Surf 00 3128.6 3151 3a Skel W 2 0.11 5 0.13 0 0.00 0 0.04 0 0.00 0 0.00 0 0.00 0 0.00 7 3 3151 3164 3a Crin W-P 0 0.00 2 0.01 22 0.01 44 0.35 112 0.03 221 0.45 0 0.00 5 0.05 406 6 3164 3168.8 3a Skel W-P 0 0.00 2 0.02 5 0.01 0 0.02 52 0.02 59 0.17 0 0.00 11 0.01 129 6 3168.8 3174.2 3a Crin W-P 0 0.00 59 0.45 7 0.01 110 0.09 39 0.01 84 0.07 0 0.00 21 0.12 320 6 SB2 3174.2 3174.5 Flood Surf 00 184 3174.5 3188.75 3a Skel W-P 0 0.00 25 0.22 114 0.14 43 1.08 253 0.05 132 0.31 4 0.01 8 0.02 579 7 3188.75 3189.6 Flood Surf 0 0.00 0 0.00 0 0.00 29 0.00 26 0.00 1 0.00 0 0.00 2 0.06 58 4 3189.6 3191.6 3a Skel W-P 0 0.00 0 0.00 49 0.02 1 0.01 37 0.00 11 0.05 0 0.00 1 0.02 99 5 3191.6 3203.5 3a Strom W-B 0 0.00 23 0.82 62 0.05 5 0.81 125 0.03 23 0.04 0 0.00 13 0.32 251 6 3203.5 3204.7 Flood Surf 0 0.00 3 0.45 2 0.00 4 0.00 17 0.00 0 0.00 0 0.00 1 0.00 27 5 3204.7 3217.2 3a Strom Bry W-P 0 0.00 46 1.19 623 0.54 126 0.31 333 0.03 101 0.17 14 0.05 12 0.11 1255 7 3217.2 3240.35 2 Crin M-P 0 0.00 7 0.02 837 0.25 334 0.10 53 0.01 116 0.18 1 0.02 3 0.01 1351 7 3240.35 3264.25 2 Skel W-P 0 0.00 55 0.13 2774 0.76 888 0.27 170 0.03 369 0.45 11 0.05 42 0.08 4309 7 Whole Core Totals 15 0.12 682 5.63 4857 40.10 2301 19.00 1605 13.25 1543 12.74 486 4.01 623 5.14 12112 pg stromatolites stromatoporoids bryozoans crinoids pods/ostracodes tabulate corals rugose corals unidentified Total Faunal Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Count for Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies Flood Surf 0 0 3 3.53 3 3.53 37 43.53 46 54.12 1 1.18 0 0 3 3.53 85 Exp 4 0.58 0 0.39 0 0.00 0 0.00 2 0.00 0 0.00 0 0.00 0 0.01 6 5 5 0.22 0 0.00 0 0.00 0 0.00 0 0.00 0 0.00 0 0.00 0 0.10 5 3b 0 0.00 0 0.00 43 0.04 0 0.00 29 0.01 6 0.00 0 0.00 6 0.01 84 3a 6 0.10 617 9.85 1200 19.16 1042 16.63 1305 20.83 1051 16.78 474 7.57 569 9.08 6264 2 Skel W-P 0 0.00 62 1.10 3611 63.80 1222 21.59 223 3.94 485 8.57 12 0.21 45 0.80 5660 Whole Core Totals 15 0.12 682 5.63 4857 40.10 2301 19.00 1605 13.25 1543 12.74 486 4.01 623 5.14 12112 Table 5: Relative abundance and diversity when the sum of all fauna equals 100 percent.

pg p stromatolites stromatoporoids bryozoans crinoids ds/ostracodes tabulate corals rugose corals unidentified

Percent Percent of Percent of Percent of Percent of Percent of Percent Percent of Percent Percent of Percent Percent of Percent Percent of Percent Percent of Sum of Percentage Total of facies total core facies total core facies total core of facies total core of facies total core of facies total core of facies total core of facies total core facies area of facies percent surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface covered by area area (ft x Begin ftg. End ftg. Facies area area area area area area area area area area area area area area area area fauna covered 100) 2953 2974.4 5 22.38 1.05 0.00 0.00 0.40 0.02 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 9.56 0.45 32.35 1.51 2137 2974.4 2989.1 3a 0.00 0.00 403.91 27.57 0.75 0.05 0.04 0.00 0.02 0.00 0.00 0.00 0.00 0.00 18.28 1.25 423.01 28.87 1465 2989.1 3016.3 Exp 58.07 2.15 38.98 1.44 0.00 0.00 0.05 0.00 0.45 0.02 0.00 0.00 0.00 0.00 0.91 0.03 98.46 3.64 2707 3016.3 3057.8 3a 0.80 0.02 8.81 0.21 6.67 0.16 23.89 0.58 0.71 0.02 58.75 1.42 41.32 1.00 9.61 0.23 6.18 0.15 4150 3057.8 3062.5 3b 0.00 0.00 0.00 0.00 4.05 0.86 0.00 0.00 0.95 0.20 0.21 0.05 0.00 0.00 0.97 0.21 352.93 75.09 470 3062.5 3099.6 3a 5.31 0.14 186.29 5.02 0.88 0.02 39.79 1.07 0.35 0.01 78.87 2.13 30.34 0.82 11.10 0.30 352.93 9.52 3708 3099.6 3100.5 Flooding Surface 0.00 0.00 0.03 0.03 0.34 0.38 0.12 0.13 0.00 0.00 0.00 0.48 0.54 90 SB3 3100.5 3128.5 3a 10.63 0.38 486.56 17.40 10.12 0.36 110.50 3.95 2.44 0.09 183.79 6.57 69.48 2.48 34.65 1.24 908.18 32.47 2797 3128.5 3128.6 Flooding Surface 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 10 3128.6 3151 3a Skel W 10.71 0.48 12.50 0.56 0.00 0.00 4.00 0.18 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 27.21 1.21 2250 3151 3164 3a Crin W-P 0.00 0.00 0.80 0.06 1.13 0.09 35.32 2.72 3.32 0.26 44.89 3.46 0.00 0.00 4.88 0.38 90.33 6.96 1298 3164 3168.8 3a Skel W-P 0.00 0.00 3.62 0.76 2.83 0.59 72.63 15.16 8.37 1.75 106.72 22.28 0.00 0.00 10.71 2.24 204.89 42.77 479 3168.8 3174.2 3a Crin W-P 0.00 0.00 45.30 8.39 1.06 0.20 9.28 1.72 0.67 0.12 7.46 1.38 0.00 0.00 7.50 1.39 71.26 13.20 540

185 SB2 0.00 0.00 0.00 0.00 0.00 3174.2 3174.5 Flooding Surface 0.00 0.00 30 3174.5 3188.75 3a Skel W-P 0.00 0.00 21.73 1.49 13.52 0.93 107.85 7.41 5.28 0.36 30.96 2.13 0.69 0.05 2.09 0.14 182.11 12.52 1455 3188.75 3189.6 Flooding Surface 0.00 0.00 0.00 0.00 0.00 0.00 0.26 0.31 0.17 0.20 0.38 0.45 0.00 0.00 5.70 6.70 6.51 7.66 85 3189.6 3191.6 3a Skel W-P 0.00 0.00 0.00 0.00 2.46 1.23 1.06 0.53 0.39 0.20 5.12 2.56 0.00 0.00 2.39 1.19 11.42 5.71 200 3191.6 3203.5 3a Strom W-B 0.00 0.00 81.82 6.88 5.37 0.45 81.46 6.85 2.57 0.22 4.18 0.35 0.00 0.00 32.32 2.72 207.72 17.46 1190 3203.5 3204.7 Flooding Surface 0.00 0.00 44.72 37.27 0.12 0.10 0.09 0.08 0.11 0.09 0.00 0.00 0.00 0.00 0.23 0.19 45.28 37.74 120 3204.7 3217.2 3a Strom Bry W-P 0.00 0.00 118.60 9.49 54.06 4.32 30.90 2.47 3.25 0.26 16.71 1.34 5.03 0.40 10.69 0.86 239.24 19.14 1250 3217.2 3240.35 2 Crin M-P 0.00 0.00 2.28 0.10 25.41 1.10 10.04 0.43 1.04 0.05 17.70 0.77 1.53 0.07 0.65 0.03 58.65 2.54 2309 3240.35 3264.25 2 Skel W-P 0.00 0.00 13.33 0.56 76.44 3.20 26.51 1.11 2.93 0.12 45.02 1.88 5.19 0.22 7.96 0.33 177.37 7.42 2390 Whole Core Totals 107.89 0.35 1469.26 4.72 205.30 0.66 554.02 1.78 33.14 0.11 600.76 1.93 153.58 0.49 170.19 0.55 3294.15 10.58 31130 pg p stromatolites stromatoporoids bryozoans crinoids ds/ostracodes tabulate corals rugose corals unidentified

Sum of Percent Percent of Percent of Percent of Percent of Percent of Percent Percent of Percent Percent of Percent Percent of Percent Percent of Percent Percent of Sum of Percentage Total of facies Facies core facies total core facies total core of facies total core of facies total core of facies total core of facies total core of facies total core facies area of facies percent surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface covered by area area (ft x Facies area area area area area area area area area area area area area area area area fauna covered 100) Flood Surf 0 0 45 13.35 0.15 0.05 0.69 0.21 0 0.12 0 0 0 0 6 1.77 52.3 15.6 335 Exp 58.07 2.15 38.98 1.44 0.00 0.00 0.05 0.00 0.45 0.02 0.00 0.00 0.00 0.00 0.91 0.03 98.46 3.64 2707 5 22.38 1.05 0.00 0.00 0.40 0.02 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 9.56 0.45 32.35 1.51 2137 3b 0.00 0.00 0.00 0.00 4.05 0.86 0.00 0.00 0.95 0.20 0.21 0.05 0.00 0.00 0.97 0.21 6.18 1.31 470 3a 27.45 0.13 1369.94 6.59 98.85 0.48 516.71 2.49 27.37 0.13 537.45 2.59 146.86 0.71 144.22 0.69 2724.45 13.11 20782 2 Skel W-P 0.00 0.00 15.61 0.33 101.85 2.17 36.55 0.78 3.97 0.08 62.71 1.33 6.71 0.14 8.61 0.18 236.02 5.02 4699 Whole Core Totals 107.89 0.35 1469.26 4.72 205.30 0.66 554.02 1.78 33.14 0.11 600.76 1.93 153.58 0.49 170.19 0.55 3294.15 10.58 31130 Table 6: Density of fauna when the total area of the slabbed core surface equals 100 percent.

Appendix E

LASKOWSKI 4-1 (PN25547) RESULTS AND SUPPORTING TABLES AND FIGURES

186

Laskowski 4-1 Results

Relative Abundance: Framework Density, Reef-Builder Diversity, and Composition of Reef-Builder Assemblages

Relative Abundance Analysis of the proportion of high level categories of fauna, when the sum of all fauna equaled 100 percent, showed that the two most numerous categories were the unidentified and brachiopods (see Tables 1 & 5). The frame-builders had relative abundances from 1% to 6% for tabulate corals, rugose corals, and stromatoporoids. Nonframe-building fauna comprised from less than 1% to 4% for bryozoans, crinoids, and stromatolites.

Percent of Population Faunal Category (when sum of all fauna equals 100%) Unidentified 53.31 Brachiopods 26.38 Tabulate corals 6.13 Rugose corals 4.88 Bryozoans 4.11 Crinoids 2.62 Stromatoporoids 1.85 Stromatolites and cyanobacteria 0.71 Table 1: Percent of population contributed by each faunal category.

Reef-Builder Diversity Faunal diversity, as expressed by the number of faunal categories represented, is summarized in Tables 2 & 5. Diversity was highest in the Reef Core Facies (3A) with a range from 1 to 7 faunal categories represented. The Bioherm Core Facies (2) also had a high diversity with 6 categories of fauna represented. The Skeletal Grainstone Facies (4) and the Restricted Facies (5) were each represented by only one faunal category. In addition, the tabulate corals included favositids, thamnoporids, auloporids, and halysitids. There was also one instance of possible colonial rugose coral (Fletcheria sp.).

Facies Number of Faunal Categories Represented Restricted Facies 5c 1 Skeletal Grainstone Facies 4 1 Reef Core Facies 3A SB4-SB3 3, 5, 4, 5 SB3-SB2 2, 1, 2, 2, 4, 2, 5, 5 Below SB2 7, 0, 3 Bioherm Core Facies 2 6 187

Table 2: Number of faunal categories represented in each facies (a coarse indicator of diversity).

Framework Density When analyzed according to the percentage of the slabbed surface of the core that was covered by fauna, the total area covered was 2.4% of the 262 feet of core. Stromatolites had the highest percentage of coverage with 1.24% (Tables 3 & 6). The unidentified and stromatoporoids had the next highest total core coverages at less than .5%. All other faunal categories had total core coverages of .1% or less.

Faunal Category Percent of Slabbed Core Surface Coverage Stromatolites 1.24 Unidentified 0.43 Stromatoporoids 0.38 Crinoids 0.11 Tabulate corals 0.10 Brachiopods 0.10 Rugose corals 0.02 Bryozoans 0.01 Table 3: Density of faunal categories as a percentage of slabbed core surface coverage.

When analyzed by facies, the stromatolites covered more than 20% of the Restricted Facies contained within the top 16 feet of the core. The Skeletal Grainstone Facies was limited to 6 feet between sequence boundaries 3 and 4 in which over 4.5% of the core was covered by stromatoporoids (Table 4 & 6). The Reef Core Facies had the most diverse coverage with stromatoporoids as the greatest contributor at over 16% in the 66 feet of core between sequence boundaries 3 and 4. Coverage for all other fauna dropped to below 3% for rest of the core in the Reef Core Facies. The Bioherm Core Facies had a coverage of less than 1% of crinoids. All crinoids noted were below Sequence Boundary 3.

Facies Faunal Categories with Most Coverage Restricted Facies 5c >20% stromatolites between SB3-SB4 (16ft.) Skeletal Grainstone Facies 4 >4.5% stromatoporoids between SB3-SB4 (6 ft.) Reef Core Facies 3A >16% stromatoporoids between SB3-SB4 (66 ft.) <2% for all fauna between SB3-SB4 <3% for all fauna between SB2-SB3 (102 ft.) <1% for all fauna below SB2 Bioherm Core Facies 2 <1% crinoids below SB3 Table 4: Faunal category coverages per facies.

188

Composition of Reef-Builder Assemblages From the bottom of the core and building the reef up, a few encrusting bryozoans, laminar to tabular stromatoporoids and a favositid tabulate coral are seen at the very bottom of the core in Facies 2 (bioherm core) from 3240’ to 3213’. Facies 3a (reef core) shows an encrusting tabulate coral (auloporid?) as the first recognizable frame-builder at 3207’. This is followed by laminar to tabular stromatoporoids, favositid corals, robust dendroid branches of an unidentified fauna, and solitary rugose corals. This assemblage continues up through the core with a possible colonial rugose (Fletcheria?) appearing at 3180’ with favositids and an unknown just below sequence boundary 2. From Sequence Boundary 2 to Sequence Boundary 3 the recognizable fauna is scarce with most identifiable specimens just above Sequence Boundary 2. The assemblage is composed of robust dendroid branches of an unidentified fauna, solitary rugose corals and at least one encrusting tabulate coral (halysites?) at 3159’. Further up the core there are a few scattered favositids and robust dendroid branching unidentified specimens until 3085’ past which there are no further recognizable fossils. From Sequence Boundary 3 up to Facies 4, there is a fairly diverse assemblage. Beginning toward the bottom of the sequence there are robust dendroid branches of tabulate corals (thamnoporids? and syringoporids?), domal to hemispherical stromatoporoids, and encrusting bryozoans (3054’ – 3049’). There are also syndepositional vertical fractures/Neptunian dikes from 3048’-3046’. Further up, the bryozoans become more delicate but the thamnoporids are still present (3042’ – 3032’). Between 3022’-3021’ there are syndepositional vertical fractures/Neptunian dikes. At the bottom of 3023’ there is a laminar to massive tabulate coral (favositid?). A few possible thamnoporids appear at 3021’, 3016’ and 3009’. Laminar to domal stromatoporoids are seen between 3009’ - 3008’. Facies 4 (skeletal grainstone) starts at 3001’ with a laminar/tabular stromatoporoid at 3000’. No other fauna are noted through the rest of Facies 4 to 2995’. Facies 5 (Restricted) is the next facies encountered. This portion of the core consists of horizontal to angled laminar stromatolites and cyanobacterial mats from 2995’ to 2979’ with some showing peloids, rip ups, and anhydrite laths. Facies 5 ends at sequence boundary 4 (2979’).

Cement The Laskowski 4-1 core is on the interpreted windward (southeast) side of Ray Reef. It has much higher porosity and permeability than any of the other cores included in this study. Due to the increased hydraulic energy on the windward margin and results of previous studies, increased cementation was expected in this core. Although syndepositional cements were encountered, vuggy and vertical fracture porosity was also encountered. This may be due to the fact that the initial cementation was later dissolved during diagenesis resulting in the open pores seen. The estimated percent of cement identified on the slabbed surface of this core was 15.8%.

189

In situ vs. Debris The examined slabbed surface of this core was comprised of 32% in situ fossils and 68% debris.

190

te la Unidid Stromom u Rug Bryz Crin Brach 2979 SB4 r t Tab Un S Tab RugoseBryozoan Crinoid Brach

-3000 3013 HFSB

-3030

-3060 3067 SB3

-3090 191

-3120 3128 HFSB

-3150 3169 SB2

-3180 3198 HFSB

-3210

160 320 480 640 800 960 1120 1280

Frame-Building Fauna Perimeter vs Depth

Average Perimeter (millimeters) 0 50 100 150 200 250 300 2950 SB4 3000

3050 SB3 3100

3150

Depth (feet) Depth SB2 3200

3250

3300

stromatoporoid tabulate coral rugose coral SB

Figure 2: Average perimeter of frame-building fauna vs. depth with sequence boundaries (SB). Note that rugose corals are clustered just below and slightly above SB2 and that tabulate corals are more prolific just above SB3. Stromatoporoids increase in size moving up to the next sequence boundary.

192

NonFrame-Building Fauna Perimeter vs Depth

Average Perimeter (millimeters) 0 1020304050607080 2950 SB4 3000

3050 SB3 3100

3150

Depth (feet) Depth SB2 3200

3250

3300

brachiopod bryozoan crinoid SB

Figure 3: Average perimeter of nonframe-building fauna vs. depth with sequence boundaries (SB). Note that crinoid debris is most prevalent above sequence boundary 2 and absent above sequence boundary 3. Bryozoans are most prevalent above sequence boundary 3 with spurts of increasing size. Brachiopods are most prevalent below and above sequence boundary 2.

Stromatolite Perimeter vs Depth

Average Perimeter (millimeters) 0 100 200 300 400 500 600 700 800 2950 3000 SB4 3050 3100 3150

Depth (feet) Depth 3200 3250 3300

Figure 4: Average perimeter of stromatolites and cyanobacterial mats vs. depth with sequence boundary 4 at top of studied core. 193

Facies Laskowski 4-1 Between SB3 and SB4 domal to dendroid laminar to hemi or robust delicate colonial solitary Begin ftg. 1 2 3A 3B 4 5 in situ debris encrust tabular massive conical branch branch rugose rugose SB4 2979 2980 2981 stromat 2982 2983 stromat 2984 stromat 2985 2986 2987 2988 2989 stromat 2990 stromat 2991 stromat 2992 stromat 2993 stromat 2994 2995 2996 2997 2998 2999 3000 strmtop 3001 3002 3003 3004 3005 3006 3007 3008 strmtop strmtop 3009 strmtop strmtop thamnop 3010 3011 3012 3013 3014 3015 3016 thamnop 3017 3018 3019 3020 3021 thamnop 3022 3023 fav? fav? (continued)

194

3021 thamnop 3022 3023 fav? fav? 3024 3025 3026 3027 3028 3029 3030 3031 3032 thamnop 3033 3034 3035 3036 thamnop/coen? 3037 3038 thamno 3039 3040 thamno bryz 3041 thamno bryz 3042 thamno; unknown 3043 3044 unknown 3045 3046 3047 3048 3049 strmtop 3050 bryz 3051 strmtop syringoporid 3052 strmtop strmtop syringop 3053 bryz strmtop thamno 3054 strmtop thamno 3055 3056 3057 3058 3059 3060 thamno 3061 3062 3063 3064 3065 3066 SB3

Figure 5: Fauna noted between SB3 and SB4.

195

Facies Laskowski 4-1 Between SB2 and SB3 domal to dendroid laminar to hemi or robust delicate colonial solitary Begin ftg. 1 2 3A 3B 4 5 in situ debris encrust tabular massive conical branch branch rugose rugose SB3 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 unknown 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 unknown 3111 3112 3113 3114 3115 3116 (continued)

196

3115 3116 3117 3118 3119 3120 3121 3122 unknown 3123 3124 3125 3126 3127 3128 favosit ww 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 ww 3141 3142 3143 favosit 3144 ww 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 halysites unknown 3160 unknown 3161 unknown 3162 unknown rugose 3163 unknown rugose 3164 rugose 3165 3166 3167 unknown 3168 unknown SB2

Figure 6: Fauna noted from Sequence Boundary 2 to Sequence Boundary 3.

197

Facies Laskowski 4-1Below SB2 domal to dendroid laminar to hemi or robust delicate colonial solitary Begin ftg. 1 2 3A 3B 4 5 in situ debris encrust tabular massive conical branch branch rugose rugose SB2 3169 3170 unknown 3171 favosit 3172 favosit 3173 unknown rugose 3174 3175 3176 rugose 3177 3178 rugose 3179 unknown rugose 3180 unknown Fletcheria 3181 unknown 3182 3183 3184 rugose 3185 3186 unknown rugose 3187 favositid 3188 favositid rugose 3189 3190 favositid 3191 3192 favositid unk 3193 3194 stromatop unk rugose 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 auloporid 3208 3209 3210 3211 (continued)

198

3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 favositid 3234 3235 3236 stromatop 3237 3238 bryz 3239 unk/bryz stromatop 3240

Figure 7: Fauna noted below Sequence Boundary 2.

199

stromatolites stromatoporoids bryozoans crinoids brachiopods/gastro tabulate corals rugose corals unidentified Total Faunal Number of Begin End Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Count for Phyla ftg. ftg. Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies Identified SB4 2979 2995 5c 12 100.00 12 1 2995 3001 4 8 100.00 81 3001 3013 3a 3 14.29 13 61.90 5 23.81 21 3 3013 3052 3a 4 1.90 27 12.80 12 5.69 52 24.64 116 54.98 211 5 3052 3054 3a 10 27.78 9 25.00 1 2.78 16 44.44 36 4 3054 3067 3a 1 1.52 1 1.52 25 37.88 17 25.76 22 33.33 66 5 SB3 3067 3097 3a 6 10.00 54 90.00 60 2 3097 3105 3a 1 100.00 1 1 3105 3115 3a 7 22.58 24 77.42 31 2 3115 3123 3a 27 19.71 110 80.29 137 2 3123 3131 3a 1 0.91 94 85.45 1 0.91 14 12.73 110 4 3131 3132 3a 5 71.43 2 28.57 7 2 3132 3149 3a 5 4.10 19 15.57 64 52.46 1 0.82 33 27.05 122 5 3149 3169 3a 4 0.86 61 13.12 3 0.65 21 4.52 376 80.86 465 5

200 SB2 3169 3198 3a 3 1.01 9 3.03 9 3.03 66 22.22 6 2.02 61 20.54 143 48.15 297 7 3198 3199 3a 00 3199 3213 3a 3 5.88 47 92.16 1 1.96 51 3 3213 3241 2 2 4.55 2 4.55 6 13.64 30 68.18 1 2.27 3 6.82 44 6 Whole core totals 12 0.71 31 1.85 69 4.11 44 2.62 443 26.38 103 6.13 82 4.88 895 53.31 1679

stromatolites stromatoporoids bryozoans crinoids brachiopods/gastro tabulate corals rugose corals unidentified Total Faunal Begin End Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Count for ftg. ftg. Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies SB4 2979 2995 5c 12 100.00 12 2995 3001 4 8 100.00 8 3001 3067 3a 18 45.47 50 101.22 38 46.34 90 118.66 138 88.31 334 SB3 3067 3169 3a 5 4.10 29 88.77 262 331.89 5 2.37 21 4.52 611 368.35 933 SB2 3169 3213 3a 3 1.01 12 8.91 9 3.03 113 114.38 7 3.98 61 20.54 143 48.15 348 3213 3241 2 2 4.55 2 4.55 6 13.64 30 68.18 1 2.27 3 44 Whole core totals 12 0.71 31 1.85 69 4.11 44 2.62 443 26.38 103 6.13 82 4.88 895 53.31 1679 Table 5: Relative abundance and diversity when the sum of all fauna equals 100%.

pg stromatolites stromatoporoids bryozoans crinoids pods/ostracodes tabulate corals rugose corals unidentified

Percent Percent Percent Percent Percent Percent Percent Percent Sum of Percenta Percent of total Percent of total Percent of total Percent of total Percent of total Percent of total Percent of total Percent of total facies ge of Total of facies core of facies core of facies core of facies core of facies core of facies core of facies core of facies core area facies percent Begin surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface covered area area (ft x ftg. End ftg. Facies area area area area area area area area area area area area area area area area by fauna covered 100) SB4 2979 2995 5c 325.61 20.35 325.61 20.35 1600 2995 3001 4 27.16 4.53 27.16 4.53 600 3001 3013 3a 34.22 2.85 0.43 0.04 0.37 0.03 35.02 2.92 1200 3013 3052 3a 3.75 0.10 1.21 0.03 0.60 0.02 7.36 0.19 42.03 1.08 54.94 1.41 3900 3052 3054 3a 26.54 13.27 0.34 0.17 0.04 0.02 0.76 0.38 27.68 13.84 200 3054 3067 3a 5.41 0.42 0.08 0.01 0.96 0.07 1.04 0.08 9.15 0.70 16.63 1.28 1300 SB3 3067 3097 3a 0.47 0.02 7.57 0.25 8.04 0.27 3000 3097 3105 3a 0.09 0.01 0.09 0.01 800 201 3105 3115 3a 0.17 0.02 0.62 0.06 0.79 0.08 1000 3115 3123 3a 2.87 0.36 2.66 0.33 5.53 0.69 800 3123 3131 3a 0.04 0.005 8.29 1.04 1.78 0.22 0.15 0.02 10.26 1.28 800 3131 3132 3a 0.12 0.12 0.10 0.10 0.22 0.22 100 3132 3149 3a 0.40 0.02 0.41 0.02 3.62 0.21 8.66 0.51 3.28 0.19 16.37 0.96 1700 3149 3169 3a 1.41 0.07 2.39 0.12 0.04 0.002 1.41 0.07 32.50 1.62 37.76 1.89 2000 SB2 3169 3198 3a 1.67 0.06 0.35 0.01 1.37 0.05 4.14 0.14 4.18 0.14 3.49 0.12 14.50 0.50 29.71 1.02 2900 3198 3199.0 3a 0.00 0.00 100 3199 3213 3a 0.14 0.01 2.68 0.19 0.08 0.01 2.90 0.21 1400 3213 3241 2 0.85 0.03 0.16 0.01 25.00 0.89 1.08 0.04 3.09 0.11 0.53 0.02 30.70 1.10 2800 Whole core totals 325.61 1.24 99.61 0.38 3.10 0.01 28.34 0.11 27.49 0.10 27.37 0.10 4.90 0.02 112.98 0.43 629.40 2.40 26200

stromatolites stromatoporoids bryozoans crinoids brachiopods/gastro tabulate corals rugose corals unidentified

Appendix F

LASKOWSKI 5-1 (PN25832) RESULTS AND SUPPORTING TABLES AND FIGURES

202

Laskowski 5 Results

Relative Abundance: Framework Density, Reef-Builder Diversity, and Composition of Reef-Builder Assemblages

Relative Abundance Analysis of the proportion of high level categories of fauna, when the sum of all fauna equaled 100 percent, showed that the most numerous faunal categories were brachiopods, stromatolites/cyanobacteria, and crinoids (see Tables 1 & 5). The framebuilders were represented by unidentified fauna and tabulate corals only. No stromatoporoids or rugose corals were identified. Among the non-framebuilders, bryozoans were not identified. Brachiopods were the most abundant at 62% while crinoids comprised 10% of the total fauna identified.

Percent of Population Faunal Category (when sum of all fauna equals 100%) Brachiopods 62.43 Stromatolites and cyanobacteria 18.78 Crinoids 9.94 Unidentified 5.52 Tabulate corals 3.31 Rugose corals 0 Bryozoans 0 Stromatoporoids 0 Table 1: Percent of population contributed by each faunal category.

Reef-Builder Diversity Faunal diversity, as expressed by the number of faunal categories represented, is summarized in Tables 2 & 5. Diversity was highest in the Bioherm Core Facies 2 with 8 categories of fauna represented. The Reef Core Facies and Restricted Facies had similar representation of faunal categories. Tabulate corals were restricted to thamnoporid an auloporid types.

Facies Number of Faunal Categories Represented Restricted Facies 5c 4, 3 Reef Core Facies 3A 2, 4 Bioherm Core Facies 2 8 Table 2: Number of faunal categories represented in each facies (a coarse indicator of diversity).

Framework Density When analyzed according to the percentage of the slabbed core surface that was covered by fauna, the total area covered was 2.28% of the 50 feet of studied core (Tables 203

3 & 6). Stromatolites had the highest percentage of coverage with 2.17%. Brachiopods, unidentified, tabulate corals and crinoids all had .05% or less coverage.

Faunal Category Percent of Slabbed Core Surface Coverage Stromatolites 2.17 Brachiopods 0.05 Unidentified 0.04 Tabulate corals 0.02 Crinoids 0.01 Stromatoporoids 0 Rugose corals 0 Bryozoans 0 Table 3: Density of faunal categories as a percentage of slabbed core surface coverage.

When analyzed by facies (Tables 4 & 6), the Restricted Facies 5c had the highest coverage with stromatolites occupying 9.86% of 11 feet. The Reef Core Facies provided 0.20% coverage and the Bioherm Core Facies totaled 0.11% coverage.

Facies Faunal Categories with Most Coverage Restricted Facies 5c 9.86% stromatolites between (11ft.) Reef Core Facies 3A 0.20% (19 ft.) Bioherm Core Facies 2 0.11% (20 ft.) Table 4: Faunal category coverages per facies.

Composition of reef-building assemblages and distribution Starting at the bottom of the studied core just above Sequence Boundary 2 there is an unidentified branching fauna. Moving up through the Bioherm Core Facies 2 from 3250’ – 3230’ a few thamnoporid and auloporid tabulate corals are noted along with other unidentified branching fauna. In the Reef Core Facies 3A (3213’-3231’ and 32008’-3009’) there is very little fauna. In fact, there is only one instance and the fauna is unidentifiable. The Restricted Facies 5c (3209’-3212’ and 3191’-3199’) is comprised mostly of laminar stromatolites and cyanobacterial mats with unidentified fauna at 3192’ and 3194’.

Cement The Laskowski 5-1 core is on the interpreted windward (southeast) side of Ray Reef. It has higher porosity and permeability than the other cores included in this study. Due to the increased hydraulic energy on the windward margin and results of previous studies, increased cementation was expected in this core. The estimated percent of cement identified on the slabbed surface of this core was 28.12%.

204

In situ vs. Debris The examined slabbed surface of this core was comprised of 20% in situ fossils and 80% debris.

205

Unid Strom Tab Crin Brach

te e s o id g z n u rin 3191 SB3 U Strom Tabula R Bry C Brach -3192

-3198

-3204 3209 HFSB -3210 206

-3216 Core Depth (ft.)

-3222

-3228

-3234

-3240 3250 SB3 20 40 60 80 100 120 140 160 180 Average Perimeter (mm)

Frame-Building Fauna Perimeter vs. Depth

Average Perimeter (millimeters) 0 20 40 60 80 100 120 3185 3190 SB3 3195 3200 3205 3210 3215 3220 3225

Depth (feet) Depth 3230 3235 3240 3245 3250 SB2 3255

unidentified stromatoporoid tabulate coral rugose coral SB

Figure 2: Average perimeter of frame-building fauna vs. depth between Sequence Boundaries 2 and 3. Note the absence of stromatoporoids and rugose corals. Tabulate corals are limited to a ten-foot interval. Unidentified fauna increase in size above 3230 feet.

207

Nonframe-Building Fauna Perimeter vs. Depth

Average Perimeter (millimeters) 02468101214 3185 3190 SB3 3195 3200 3205 3210 3215 3220 3225

Depth (feet) Depth 3230 3235 3240 3245 3250 SB2 3255

brachiopod bryozoan crinoid SB

Figure 3: Average perimeter of nonframe-building fauna vs. depth between Sequence Boundaries 2 and 3. Note the absence of identified bryozoans. Average perimeter of brachiopods generally increases with shallowing upward cycle. Crinoids show a wide range of perimeters in a small interval (~20 feet).

208

Stromatolite Perimeter vs. Depth

Average Perimeter (millimeters) 0 20 40 60 80 100 120 140 3185 3190 SB3 3195 3200 3205 3210 3215 3220 3225

Depth (feet) 3230 3235 3240 3245 3250 SB2 3255

stromatolite SB

Figure 4: Average perimeter of stromatolites and cyanobacterial mats vs. depth between Sequence Boundaries 2 and 3.

209

Facies Laskowski 5-1 Between SB2 and SB3 domal to dendroid laminar to hemi or robust delicate solitary colonial Ftg. 1 2 3A 3B 4 5 in situ debris encrust tabular massive branch branch rugose rugose SB3 3191 stromat stromat stromat stromat unknown 3195 stromat stromat stromat stromat missing 3200 missing missing missing missing missing 3205 missing missing missing stromat stromat 3210 stromat

vertfrac

3215 missing

3220 unknown

3225

3230 thamno?

unknown

unknown 3235

thamno?/auloporid?

3240

3245

unknown 3250 SB2 Figure 5: Stratigraphic column showing fauna, morphology, and in-situ vs. debris between Sequence Boundaries 2 and 3. 210

stromatolites stromatoporoids bryozoans crinoids brachiopods/gastrop tabulate corals rugose corals unidentified

Total Faunal Number of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Count for Phyla Begin ftg. End ftg. Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies Identified SB3 3191 3199 5c 22 55.00 0 0 0 16 40.00 0 2 5.00 40 4 3199 3208 missing 00 3208 3209 3A 3 75.00 0 0 1 25.00 0 0.00 4 2 3209 3212 5c 9 100.00 0 0 0 0 0 0 0.00 9 3 3212 3231 3A 0 0 0 7 10.45 55 82.09 4 5.97 0 1 1.49 67 4 3231 3251 2 0 0 0 0 0 0 11 18.03 41 67.21 2 3.28 0 0 7 11.48 61 8 SB2 Whole core totals 34 18.78 0 0 0 0 18 9.94 113 62.43 6 3.31 0 0 10 5.52 181

stromatolites stromatoporoids bryozoans crinoids brachiopods/gastrop tabulate corals rugose corals unidentified

Total Faunal 211 Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Count for Facies Count Population Count Population Count Population Count Population Count Population Count Population Count Population Count Population Facies 5c 31 64.58 0 0 0 0 0 0 16 33.33 0 0 0 0 2 4.17 49 3A 3 4.23 0 0 0 0 7 9.86 56 78.87 4 5.63 0 0 1 1.41 71 2 0 0 0 0 0 0 11 18.03 41 67.21 2 3.28 0 0 7 11.48 61 Whole core totals 34 18.78 0 0 0 0 18 9.94 113 62.43 6 3.31 0 0 10 5.52 181

Table 5: Relative abundance and diversity when the sum of all fauna equals 100 percent.

pg p stromatolites stromatoporoids bryozoans crinoids /ostracodes tabulate corals rugose corals unidentified Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Sum of Percentage Total facies total core facies total core facies total core facies total core facies total core facies total core facies total core facies total core facies area of facies percent Begin End surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface covered by area area (ft x ftg. ftg. Facies area area area area area area area area area area area area area area area area fauna covered 100) SB3 3191 3199 5c 90.95 11.37 0.00 0.00 0.00 0.36 0.04 0.00 0.00 0.03 0.03 91.34 11.42 800 3199 3208 missing 3208 3209 3A 0.87 0.87 0.03 0.03 0.90 0.90 100 3209 3212 5c 16.93 5.64 0.00 0.00 0.00 0.00 0.00 0.00 0.00 16.93 5.64 300 3212 3231 3A 0.00 0.00 0.00 0.16 0.01 1.28 0.07 0.51 0.03 0.00 0.94 0.05 2.89 0.16 1800 3231 3251 2 0.00 0.00 0.00 0.11 0.01 0.82 0.04 0.32 0.02 0.00 0.88 0.04 2.14 0.11 2000 SB2 Whole core totals 108.75 2.17 0.00 0.00 0.00 0.00 0.27 0.01 2.48 0.05 0.84 0.02 0.00 0.00 1.85 0.04 114.20 2.28 5000

pg p stromatolites stromatoporoids bryozoans crinoids /ostracodes tabulate corals rugose corals unidentified

212 Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Percent of Sum of Percentage Total facies total core facies total core facies total core facies total core facies total core facies total core facies total core facies total core facies area of facies percent surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface surface covered by area area (ft x Facies area area area area area area area area area area area area area area area area fauna covered 100) 5c 107.88 9.81 0.00 0.00 0.00 0.00 0.00 0.00 0.36 0.03 0.00 0.00 0.00 0.00 0.03 0.02 108.26 9.86 1100 3A 0.87 0.05 0.00 0.00 0.00 0.00 0.16 0.01 1.31 0.07 0.51 0.03 0.00 0.00 0.94 0.05 3.80 0.20 1900 2 0.00 0.00 0.00 0.00 0.00 0.00 0.11 0.01 0.82 0.04 0.32 0.02 0.00 0.00 0.88 0.04 2.14 0.11 2000 Whole core totals 108.75 2.17 0.00 0.00 0.00 0.00 0.27 0.01 2.48 0.05 0.84 0.02 0.00 0.00 1.85 0.04 114.20 2.28 5000

Table 6: Density of fauna when the total area of the slabbed core surface equals 100 percent.

Appendix G

WINDWARD VS LEEWARD EFFECTS ON FAUNAL DISTRIBUTION AND RESERVOIR CHARACTERISTICS: SIMILARITIES BETWEEN RAY REEF (SILURIAN) AND THE MARGIN AND FORESLOPE OF THE TONGUE OF THE OCEAN, BAHAMAS

213

WINDWARD VS LEEWARD EFFECTS ON FAUNAL DISTRIBUTION AND RESERVOIR CHARACTERISTICS: SIMILARITIES BETWEEN RAY REEF (SILURIAN) AND THE MARGIN AND FORESLOPE OF THE TONGUE OF THE OCEAN, BAHAMAS

Abstract

Niagaran (Silurian) reefs are important sources of hydrocarbons in the Michigan Basin and have been since their discovery in southwest Ontario in the early 1900’s. In addition, some of these reservoirs have been used for gas storage and may be viable as potential CO2 sequestration sites. Despite extensive research on Niagaran reefs, most studies concerning faunal abundance and distribution have been qualitative studies conducted by paleontologists with an emphasis on taxonomy, paleoecology, and evolution. Few studies have focused on the windward/leeward influence on reef geometry, facies distribution, faunal distribution, and cementation. This study is the first semi-quantitative study utilizing multiple subsurface cores to determine the relative abundance and general distribution of fauna in a single Wenlock reef located in the southern pinnacle reef belt of the Michigan Basin. This study used facies descriptions and stratigraphic sequences of Wold (2008) as a starting point for further examination of subsurface cores to determine relative faunal abundance, faunal density, and faunal diversity (phyla richness) on the crest, windward, and leeward margins of Ray Reef. Relative abundance on the leeward side was dominated by stromatoporoids, bryozoans, brachiopods and other unidentifiable fauna. Relative abundance of faunal constituents on the windward side was dominated by unidentified skeletal grains and

214

brachiopods. The crest of the reef was dominated by bryozoans and crinoids as well as unidentified fauna. Faunal density and diversity were highest in the crest cores and Reef Core Facies. Syndepositional cementation was most abundant on the windward side and least abundant on the leeward side. Community replacement repeatedly occurred in shallowing upward cycles coinciding with sequence boundaries which are most likely associated with eustatic sea level changes. Results from this study support the findings of other workers using a sequence stratigraphic approach (Ritter, 2008; Wold, 2008; Qualman, 2009) that helped to explain why these reefs are more heterogeneous than previous models suggest. This study also finds similarities with a modern margin and slope analog in the Bahamas, from the standpoint of the windward/leeward influence on reef/slope geometry, facies distribution, faunal distribution, and cementation. These similarities suggest that, although not a one-to-one correlation, growth and development of reefs during the Silurian may have occurred through processes comparable to those seen in the Pleistocene to modern.

INTRODUCTION

Figure 1: Paleogeographic reconstruction (Blakey, 2011) of Laurentia and the epicontinental and epeiric seas during the Silurian (430 Ma) with the location of the Michigan Basin indicated by the box. Arrows show the surface winds between the equator and 30 degrees south blowing from the south-southeast to the north-northwest.

The most intense research on Silurian reefs of the Michigan Basin (Niagaran age) was conducted in the 1950’s through 1980’s. Most of these studies predate the methods used in sequence stratigraphic analysis (Briggs and Briggs, 1974; Gill, 1973, 1977; Huh et al., 1977; Jodry, 1969; Lowenstam, 1950; Shaver, 1974, 1977;

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Textoris and Carozzi, 1964) and produced models of pinnacle reef growth that do not express the vertical or lateral heterogeneity that has since been shown to occur in these reservoirs. In addition, most of the published literature on Silurian reefs in the Great Lakes area do not focus on the pinnacle reefs and complexes in the northern and southern trends of the Michigan Basin proper, but rather focus on outcrops or quarries in the surrounding areas of Illinois (Ingels, 1963), Wisconsin (Watkins, 1993), Indiana (I.U. Paleontology Seminar, 1976, 1980; Kissling and Lineback, 1967; Lehmann and Simo, 1989, 2000; Peters and Bork, 1999; Shaver, 1974), Ohio (Schneider and Ausich, 2002), and Canada (Copper, 2002; Copper and Fay, 1989). Of the studies that have been conducted on Silurian reefs in the area, the number of studies that have focused on the relative abundance and general distribution of reef fauna are few (Balogh, 1981; Ingels, 1963; Lehmann and Simo, 1989; Schneider and Ausich, 2002; Watkins, 1993). The primary goal of this study was, therefore, to quantitatively analyze relative abundance (including framework density and diversity) and general distribution of fauna in a single Wenlock reef complex and determine whether these parameters are consistent or variable on the windward and leeward sides of the reef, as well as on the crest. Additionally, the effects of wind and wave energy on reef geometry, facies distribution, cementation, and their combining effects on reservoir properties will also be discussed. The findings of this study will improve our understanding of Silurian reef growth and reservoir development. The reef chosen for this study is Ray Reef which is located in Macomb County, Michigan, along the southern trend of pinnacle reefs (Figures 2 & 3). Ray Reef was chosen because a previous study (Wold, 2008) determined facies and third order sequence stratigraphic boundaries that were correlated across the reef and used 217

to create 3-D facies and porosity/permeability models. The third order sequence boundaries identified by Wold (2008) were used in this study as time correlative surfaces for evaluating community replacement, relative abundance and distribution analysis of fauna across the reef.

Figure 2: Michigan Basin region showing basin in dark gray and platform reef banks in light gray. Pinnacle reefs grew on the ramps sloping down from the platform into the basin creating the northern and southern pinnacle reef belts. Ray Reef is located in the southern reef trend and is denoted with a black circle. Redrafted from Gardner and Bray (1984) and Lehman and Simo (1989).

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Figure 3: (left) Map of the studied cores in Ray Reef with the paleowind direction from the south-southeast. Ray Reef is located in Macomb County (right) which is highlighted in brown on the inset map of Michigan.

GEOLOGIC SETTING

During the Silurian, 412-438 million years ago, what is now the Michigan Basin was located 10-15 degrees south of the equator (Briggs and Briggs, 1974), and was covered in a warm, shallow, epicontinental sea which extended from the Taconic highlands (present-day Atlantic seaboard) across the Allegheny Trough in the Appalachians and across most of the central part of the continent (Figure 2). The coastline was located on the southern edge of the Canadian Shield, which was to the

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north (Briggs and Briggs, 1974). Midcontinental arches partitioned the basin with the Kankakee Arch to the southwest, Findlay-Cincinnati Arches to the south and southeast, Algonquin Arch to the east (Briggs and Briggs, 1974), and the Wisconsin Arch to the west (Gardner and Bray, 1984) as shown in Figure 2. Warm ocean waters met a barrier of patch reefs which encircled the subsiding saucer-shaped (Howell and van der Pluijm, 1999) Michigan Basin. Pinnacle reefs have been interpreted as being developed on the shelf sloping down into the basin, which reached its maximum depth at its center at approximately 200-300 meters (656-984 feet) (Liebold, 1992). The term “pinnacle” has been applied to these reefs due to their isolation, high relief, and small areal extent (Gill, 1977). Shouldice (1955) defined pinnacles as structures over 250 feet (76 meters) high with a length of less than two miles (<3.2 km). Ray Reef meets these criteria with an approximate height of 300 feet (91 meters) and an area of two square miles (5 square kilometers). Today, the Michigan Basin is roughly circular and covers approximately 207,000 square kilometers (80,000 square miles) (Catacosinos, 1991). It is 400 km (248.5 miles) in diameter and almost 5 km (3.1 miles) deep (Howell and van der Pluijm, 1999). The majority of the Basin is contained in the lower peninsula of Michigan, but it also extends into the southern portion of the upper peninsula of Michigan and the bordering edges of the surrounding Canadian province and Midwestern US states (in a clockwise direction: western parts of Ontario Canada close to Lakes Huron and Erie, northern Ohio and Indiana, northeastern Illinois, eastern and northern Wisconsin – see Figure 2). The 90–150 meter tall (300-500 feet) Niagaran pinnacle reefs are encased in evaporites and dolomite/limestone. Overlying the Silurian deposits are Devonian and Carboniferous sediments, Jurassic red beds, and glacial till. 220

Many Niagaran reefs in the Michigan Basin have been thoroughly dolomitized and show signs of karsting, dissolution and recrystallization (Gill, 1977). However, moving from the 210 meter (700 foot) thick reef and bank area of the pinnacle belts into the center of the basin, the Niagara Formation becomes progressively less dolomitic. It thins to approximately 30 meters (100 feet) in the center of the basin where it is mostly limestone (Catacosinos, 1991).

Regional Stratigraphy

The regional stratigraphy of the European Wenlockian Series of rocks in Michigan includes the following groups: Burnt Bluff, Manistique, and Niagara (Catacosinos et al., 2000). The Niagara Group is split between the Lockport Dolomite and the Guelph Dolomite Formations. The interval of interest for this study is the Guelph Dolomite Formation. This formation has also been referred to by the following names: Brown Niagara, Niagaran Reef, Pinnacle Reef, and Engadine Dolomite (Catacosinos et al., 2000). Despite recent work on the correlation of the Silurian Provincial Series of North America (Cramer et al., 2011), it is still not possible to correlate Michigan stratigraphy with the rest of North America or the world. Figure 4 shows the stratigraphic nomenclature for the Michigan Basin and the chronostratigraphy for the revised North American classification.

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Figure 4: Stratigraphic Nomenclature for Silurian strata in Michigan (Guelph Dolomite Formation highlighted) compiled from Catacosinos et al., 2000; Simo and Lehman, 2000. Note that, in the Michigan Subsurface Group and Formation columns and in the Informal Literature column, the rows are not to scale for sediment thickness or time. Last two columns (Revised North American and Global chronology) from Cramer et al., 2011.

Changes in Sea Level and Climate During the Silurian

(Cramer and Saltzman, 2007). Several sea level curves for the Silurian have been published. Some are global eustatic sea level curves (e.g. Haq and Schutter, 2008; Loydell, 1998; Johnson, 2010) and others are regional (e.g. Johnson 1996; Spengler and Read, 2010). Ross and Ross (1996) developed a global sea level curve that has been questioned as being truly global since Ross and Ross (1996) used data from sections of only one continent, Laurussia (Munnecke et al., 2010). There are inconsistencies between different sea level curves. The researchers neither used the same methods nor do they agree on every highstand or lowstand of sea level or their amplitude. Munnecke et al. (2010) provided a review of these sea level curves. Ross and Ross (1996) used depositional sequences to create their sea level curve with fluctuations of 60 meters (~197 ft.) throughout the Silurian. All of the sea level curves created by Johnson have been tied to generalized graptolite zones. Johnson (2010) reported 10 global highstands with magnitudes ranging from several tens of meters (~65 feet) to more than 70 meters (230 feet) by calibrating highstands with buried coastal topography. The sea level curve produced by Haq and Schutter (2008) was determined using sequence stratigraphy and includes 15 highstands and implies fluctuations of up to 140 meters (~459 feet). A regional sea level curve by Spengler and Read (2010) shows 11 highstands interpreted as 3rd order sequences in the area of the Wabash Platform based on high frequency sequence stratigraphy. Although sea level curves are provided, no amplitudes for fluctuations are proposed. Ross and Ross (1996), showed seven sea level highstands, two of which occurred in the Wenlock (Figure 5) and a third in the overlying Cain Formation (A-0 Carb) of the Ludlow series. Ross and Ross (1996) considered these to be 1-3 million 223

years, 3rd order sea level fluctuations affecting cratonic shelves but not basins. These three sea level changes were also identified in the cores of Ray Reef studied by Wold (2008) and were correlated across the Michigan Basin by Ritter (2008). Figure 5 shows sea level curves from Ross and Ross (1996) and Spengler and Read (2010) for comparison on a regional level and Johnson (2010) and Haq and Schutter (2008) for a more global perspective.

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Figure 5: Global sea level curves determined using sequence stratigraphy (Haq & Schutter, 2008) and generalized graptolite zones (Johnson, 2010). Regional sea level curves determined using high frequency sequence stratigraphy of the Wabash Platform (Spengler & Read, 2010) and graptolite and conodont assemblages from the Illinois Basin (Ross & Ross, 1996). Arrows indicate eustatic sea level highstands identified in Ray Reef by Wold (2008) and across the Michigan Basin by Ritter (2008). (redrafted from Cramer et al., 2011; Munnecke et al., 2010; and Ross and Ross, 1996).

Wind Direction on Reefs in the Michigan Basin During the Silurian

region. As the air travels poleward, it cools and becomes drier and denser and begins to descend in the subtropics, around 30 degrees latitude, both north and south. These circulation cells between the equator and 30 degrees north latitude in the northern hemisphere, and between the equator and 30 degrees south latitude in the southern hemisphere, are called Hadley cells (Thurman and Trujillo, 1999). The high pressure zones that are created around 30 degrees latitude from the dry descending air masses are referred to as subtropical highs. These areas usually experience conditions that are dry and clear. The area of low pressure near the equator where air is moist and rising is referred to as equatorial lows (Thurman and Trujillo, 1999). The air movement along the surface of the Earth is what creates the wind belts. Between the equator and 30 degrees, the air moves from the subtropical highs to the equatorial lows. These are called the trade winds. In the southern hemisphere, the wind blows from the southeast to the northwest due to the Coriolis effect creating the southeasterly trade winds (Thurman and Trujillo, 1999). In the northern hemisphere, the wind blows from the northeast to the southwest creating the northeast trade winds. A south to southeasterly dominant wind direction during the Silurian is assumed for the Michigan Basin since it was located between the equator and 30 degrees south latitude (Copper, 2002; Scotese, 2003; Blakey, 2011) (Figures 6 and 7). Wold (2008), in addition to assumed easterly trade winds, based the interpretation of a predominantly south to southeast wind direction on Ray Reef by a combination of reef geometry and reservoir characteristics. The southern end of the reef has a steep margin with thick packages of stacked facies which have higher porosity and permeability values (Figures 6 and 7). This was interpreted as being caused by increased cementation of skeletal grains which allowed the angle of declivity to become greater as it aggraded and prograded and was interpreted to be the 226

windward side of the reef. The northern end of the reef has a lower angle of declivity, contains thinner packages of stacked facies which prograde, contains more fine-grained sediment which was swept off of the reef crest, and has lower porosity and permeability values and was therefore interpreted to be the leeward side of the reef (Figures 6 and 7).

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B) C)

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Sequence Stratigraphy Boundaries

Since this study relied on previously interpreted sequence boundaries (SB) in making interpretations, a short overview of this information is in order. The entire Silurian comprises one 2nd order sequence. Although the Silurian is the shortest period in the Phanerozoic (443-416 Ma), it falls within the 10-50 million year time span of second order cycles that are thought to be driven by a combination of tectonics and the volume of ocean basins, with lesser influence caused by ice volume changes (Read et. al, 1995) . Within this second order cycle of the Silurian are multiple superimposed third order cycles. Third order cycles range from .5 – 5 million years long and are thought to be caused by changes in ice volume (Read et. al, 1995). High frequency cycles (fourth and fifth order sequences or Milankovitch cycles) are thought to be driven by the shape of the Earth’s orbit around the sun (eccentricity) of 100 kyrs and 400 kyrs, changes in the Earth’s tilt (obliquity) of 40 kyrs, and changes in the Earth’s “wobble” (precession) of 20 kyrs (Read et. al, 1995). It is the fourth and fifth order sequences that are thought to control reservoir quality in carbonates (Grammer et al., 2004). Within the Ray Reef cores, Wold (2008) identified three 3rd order sequences. The datum for the 3-D model was set at the stratigraphic top of the Lockport

4000 API). Wold (2008) also identified fourth order high frequency sequence boundaries (HFSB) across Ray Reef.

Previous work

James et al. (1976) found that the distribution of early submarine cementation on reefs was influenced by wind and currents. Studies by Marshall and Davies (1981) and Gischler (1995) showed that reefs exposed to higher water energy were better cemented than those exposed to low or medium water energies. Studies by Klovan (1974) and Grammer et al. (1993a, 1993b, 1999) have shown that windward margins experience rapid cementation with steeper margins and abrupt facies changes while leeward margins have more gently sloping sides with gradual facies changes over longer distances. Like Klovan (1974) and Grammer et al. (1993a), Wold (2008) found that the windward margin of Ray Reef was steeper with more abrupt facies changes than the leeward margin which had a much gentler slope and gradual change in facies. Wold also found, as Grammer et al. (1993a) did, that the windward margin with its predominantly skeletal grainstones had higher porosity and permeability values. Wold identified three stages/facies groups in general agreement with previous workers: Facies 1&2 mud-rich bioherm; Facies 3&4 reef; Facies 5 restricted. Wold also identified three 3rd order sequence boundaries which were correlated between multiple cores. Fourth and fifth order sequences were also identified in the cores but did not correlate with each other. Wold found that the 4th order sequences controlled the reservoir distribution and facies variability and suggested that wind could have been an influential factor. This study will build on previous knowledge of Ray Reef to determine if wind and water energy affect faunal abundance, density, diversity, 230

general distribution, cementation, and reservoir characteristics.

METHODS

There are sixteen sub-surface cores available for study from Ray Reef which are housed at the Michigan Repository for Research and Education. Of those, Wold (2008) chose eight cores for description and use in determining stratigraphic sequences due to their quality and continuity of core footage. This study incorporated the previous descriptions, facies determinations, and sequence stratigraphic boundaries of these cores and focused on the further examination of six of the eight cores to determine relative faunal abundance, framework density, diversity, and general distribution throughout Ray Reef (Table 1). This study employs four parameters to characterize the abundance and distribution of reef fauna: 1) relative abundance, 2) framework density, 3) reef- builder diversity, and 4) composition of reef-building assemblages. These parameters were studied on fauna grouped into the following categories: cyanobacteria (mats or stromatolites), stromatoporoids, tabulate corals, rugose corals, bryozoans, crinoids, brachiopods, and unidentifiable fauna. The unidentifiable fauna are so called because they still retain enough of their original shape, size, or texture to be recognized as skeletal clasts or grains but have been diagenetically altered to the point that they cannot be placed into one of the above mentioned categories. Relative abundance, in this study, is an expression of the percentage of an individual phylum when the sum of all phyla counted equals one hundred percent. Faunal categories that have relative abundances of 20% or more are interpreted as dominant fauna. General distribution, in this study, refers to the location on the reef in which different assemblages of fauna are located in relation to hydraulic energy, 231

e.g. windward side, crest, or leeward side.

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Table 1: Comparison of Cores in Ray Reef

Core S Faunal Core In Well Name Length (ft) B Relative Abundance Density Density Cement situ Debris Leeward Stromatop 1.43%, Unid 0.35%, 3198-3252 4 Stromatop 54%, Unid 39%, Tab 0.04%, Bryz 0.01%, Percy 2-2 (54.5) 3 Tab 3%, Bryz 3%, Crin 1% Crin 0.002% 1.82% 16% 16% 84% Brach 30%, Bryz 26%, Cyano 1.30%, Stromatop 0.81%, 4 Tab 12%, Unid 10%, Tab 0.79%, Crin 0.54%, 2934-3251 3 Crin10%, Stromatop 4%, Bryz 0.45%, Brach 0.30%, Jacob 1-36 (288) 2 Cyano 4%, Rugose 4% Rugose 0.17%, Unid 0.09% 4.44% 21% 39% 61% Crest Unid 29%, Bryz 26%, Unid 3.88%, Stromatop 0.80%,

233 4 Crin 22%, Stromatop 12%, Cyano 0.56%, Tab 0.42%, Halmich 2- 2923-3219 3 Tab 4%, Cyano 4%, Bryz 0.41%, Crin 0.35%, 1 (294) 2 Rugose 1%, Brach 1% Rugose 0.05%, Brach 0.03% 6.51% 19% 16% 84% Bryz 40%, Crin 19%, Stromatop 4.7%, Crin 1.8%, Brach 13.2%, Tab 12.7%, Tab 1.9%, Bryz 0.66%, 2952-3264 3 Unid 5%, Stromatop 5.6%, Unid 0.55%, Rugose 0.49%, BTK 1-36 (311) 2 Rugose 4%, Cyano 0.12% Cyano 0.35%, Brach 0.11% 10.58% 24% 16% 84% Windward 4 2979-3241 3 Lask4 (220) 2 Unid 53%, Brach 26% Cyano 1.24%, Unid .43% 2.40% 22% 32% 68% Brach 62%, Cyano 19%, Crin 3190-3250 3 10%, Unid 6%, Cyano 2.17%, Brach 0.05%, Lask5 (50) 2 Tab 3% Unid, Tab, Crin <0.05 2.29% 29% 20% 80% Averages: 4.67% 22% 23% 77%

Framework Density

In developing a new quantitative method for determining ancient reef zonation, Perrin (1995) defined framework density using three quantitative parameters: 1) reef-building fauna preserved in growth position, 2) sediment, 3) cement, and 4) primary porosity. This study was not able to follow this definition for several reasons. As concerns fauna found in growth position, this study, like others, shows that the majority of the reef is composed of debris and not fauna in growth position (Friedman, 1985; James, 1983). Since density is closely dependent on the abundance, (the number of individuals or colonies), size, and morphologies of the reef builders (Perrin et al., 1995), all fauna were included in calculations of density, whether they were in growth position or not. Fauna size was captured by image analysis software and analyzed by perimeter as discussed below. Fauna morphology and specimens found in situ were noted. In regards to amount of sediment and primary porosity, the cores from Ray Reef are all dolomitized making it very difficult to distinguish originally micritic sediment from micritic cement in dolomitized core (Friedman, 1985). Diagenesis, especially dolomitization, has also altered the primary porosity and original cementation. As a result, framework density, as calculated in this study, is expressed as the percentage of subsurface slabbed core that is covered by fauna when the total slabbed core surface area equals one hundred percent. For example, if in one foot of slabbed core there were densities of: stromatoporoid 10%, unidentified fauna 10%, tabulate coral 5%, rugose coral 5%, bryozoan 2%, and crinoid 2%, then the total faunal coverage would equal 34% with the remaining 66% of the coverage consisting of undistinguished matrix, cement, and pore space. The sum of all fauna and non-fauna equals 100% coverage of the slabbed surface of the

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core. Framework density was analyzed in categories of entire cores, facies, and sequences across the reef to make interpretations concerning faunal distribution in different hydraulic settings and vertical changes in communities through time.

Diversity

Diversity, as expressed in this study, refers to taxonomic richness only, e.g. facies with greater numbers of different phyla present (or greater numbers of families of tabulate corals) are considered more diverse than facies with fewer numbers of different phyla present. No complex calculations such as the Shannon-Weaver index of diversity (Hammer et al., 2001) were conducted.

Distribution and Composition of Reef-Building Assemblages

This study used a combination of faunal identification, abundance and dominance, morphology, and hydraulic energy settings to determine the vertical change or community replacement in six subsurface cores located throughout the reef. Dominance was expressed as fauna with greater than 20 percent relative abundance. It is generally accepted that ecological succession is expressed as increases in species diversity, biomass, structural complexity, and stability through time (James and Bourque, 1992). Biomass has also been shown to increase with shallowing upward water conditions (Riding, 1981). This study used the average perimeter of fauna as an indicator of biomass which was analyzed using spindle diagrams (Hammer et al., 2001), correlated to previously interpreted third order sequence boundaries and high frequency sequence boundaries (Wold, 2008) to evaluate changes in biomass with shallowing upward sequences that could indicate community 235

replacement. Although Stearn (1982) argued that modern corals show no general morphologic patterns and should not be used as indicators of ancient environments, there are many published articles that argue that morphology is indicative of environmental conditions. This study used the findings of workers who have used modern coral reefs as models to interpret ancient reefs (Gischler, 1995; James, 1983; James and Bourque, 1992; Klovan, 1974).

Procedure

Each core slab was wetted with water, scanned using a desktop flat-bed scanner, and saved as an image file. The core slab was then examined using a hand lens and/or low power binocular microscope. Skeletal fragments or molds were assigned to the following categories: Cyanobacteria (including mats and stromatolites), stromatoporoids, tabulate corals, rugose corals, crinoids, brachiopods, bryozoans, and unidentifiable fauna. Each fossil category was assigned a color code. Identified fossil fragments approximately 4 mm in size or larger were color-filled on the images using graphic software. Growth forms, when detectable, were noted in a spreadsheet as were fossils that were found in situ. Identification of tabulate corals to

families (e.g. favositids, auloporids, halysitids, heliolitids, and thamnoporids) was noted when possible. Percentage of core coverage of skeletal fragments less than 4 mm in size were estimated using visual estimate charts (Baccelle and Bosellini, 1965) and entered into the spreadsheet. Color-filled images were analyzed using an image analysis program. The faunal count and the faunal density of each fossil category was calculated by the image analysis program and output to a spreadsheet. The program also collected 236

additional data for each component (e.g. perimeter, maximum width, maximum length, minimum width, minimum length, etc.). Calculations were made from the spreadsheets for relative abundance, framework density, and average perimeter by foot, facies, sequences, and total cores.

Evaluation of Porosity

Results and Discussion

Relative Abundance

When the total of all cores were analyzed, the Percy core (leeward margin) had dominant relative abundances of stromatoporoids with other unidentifiable fauna. The Jacob core (crest to leeward margin) had dominant relative abundances of brachiopods and bryozoans (Table 1 and Figure 8). The crest cores had dominant relative abundances of bryozoans, crinoids, and other unidentifiable fauna in the 237

Halmich core and bryozoans and crinoids in the Busch-Tubbs-Kuhlman (BTK) core (Table 1 and Figure 8). The windward cores had dominant relative abundances of brachiopods and unidentifiable fauna in the Laskowski 4-1 core and brachiopods in the Laskowski 5-1 core (Table 1 and Figure 8). Since this study is capturing data for faunas with a wide range of sizes, relative abundance does not necessarily indicate which fauna actually make up most of the reef. Framework density is a much more indicative measure of reef composition because it expresses the percentage of surface area which fauna occupy. However, the relative abundance numbers do indicate that, among the smaller sized fauna, brachiopods are more abundant on the windward side of the reef while bryozoans and crinoids are more abundant on the crest.

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Relative Abundance of Fauna Across Wells in Ray Reef

20 Relative Abundance (%)

0 Lask5 Lask4 BTK Hal Jacob Percy

Unid Stromatoporoid Tabulate Rugose Bryozoan Crinoid Brachiopod

Figure 8: Relative abundance of fauna across wells in Ray Reef. Relative abundance is the percentage of each fauna when the sum of all fauna equals one hundred percent. Laskowski 5 (Lask5) and Laskowski 4 (Lask4) wells are on the windward side of the reef. The Halmich (Hal) and Busch-Tubbs-Kuhlman (BTK) wells are on the reef crest. The Jacob and Percy wells are on the leeward side of the reef. Refer to Figure 3 for well locations. (unid = unidentifiable).

Framework Density

The general trend, in modern coral reefs, of the density of reef-builders is that it initially increases with water depth on the upper part of the reef slope and then decreases with depth (Wells, 1957; Liddell and Ohlhorst, 1988). On the reef flat, it increases to the reef crest where corals may be replaced by coralline algae (Tracey et al., 1948; Wells, 1957; Chevalier and Beauvais, 1987; Hubbard et al., 1990) and on the deep slopes, it decreases quickly as scleractinian corals are replaced by other fauna such as coralline algae (Minnery et al., 1985; Minnery, 1990), sclerosponges 239

(Land and Moore, 1977; Liddell and Ohlhorst, 1988), or encrusting foraminifera (Reiss and Hottinger, 1984; Perrin, 1989, 1990, 1992), or by sediment. Below certain depths, colonies may decrease in size and change morphologies to more delicate foliaceous or platy shapes. This lowers their framework densities (Perrin et al., 1995). In Ray Reef, the highest framework density was found in cores that are interpreted as being on the reef flat to reef crest. Total framework density was 6.5% for the Halmich 2-1 (crest) core and 10.6% for the Busch-Tubbs-Kuhlman 1-36 (crest) core (Table 1 and Figure 9). Both windward and one leeward core (Percy 2-2 = 1.82% total density) had the lowest framework densities. The Laskowski 4-1 (windward margin) core had a total framework density of 2.4% and the Laskowski 5- 1 (windward margin) core had 2.3% (Table 4 and Figure 32). The Jacob 1-36 (crest to leeward margin) core had a medium range of framework density of 4.44% (Table 1 and Figure 9). Although these percentages of framework density seem to be very low, they are similar to densities of framework fauna found in other reefs (Friedman, 1985). Coral fragments are found to comprise only 2%-15% of the total debris contiguous to the Great Barrier Reef (Bennett, 1971). Reefs are comprised mostly of mud and debris, not in situ fossils (Friedman, 1985). The findings of this study confirm that most of the reef is composed of matrix and cement, with lesser amounts of skeletal grains and pore space. The leeward and crest cores all had stromatoporoids as either the number one or number two contributor of framework density ranging from 0.80% to 4.7% (see Table 4 and Figure 32; Percy (leeward margin) = stromatoporoid 1.43%, unidentifiable fauna 0.35%; Jacob (crest to leeward margin) = stromatoporoid 0.81%, tabulate corals 0.79%; Halmich (crest) = unidentifiable fauna 3.88%, stromatoporoid 240

0.80%; BTK (crest) = stromatoporoid 4.7%, crinoid 1.8%). This indicates that the energy level of the water was high enough to provide sufficient oxygen and nutrient levels but not so energetic as to inhibit the stromatoporoids. In contrast, the windward cores did not have stromatoporoids as either dominant in relative abundance or framework density but rather unidentifiable fauna of 0.43% in the Laskowski 4-1 (windward margin) core and in the Laskowski 5-1 (windward margin) core, brachiopods of 0.05% and unidentifiable fauna, tabulate corals, and crinoids each with less than 0.05% (see Table 1 and Figure 9). The Laskowski 4-1 (windward) core is interpreted as being located on the forereef slope at a depth high enough to be in rough water causing lower densities and lack of stromatoporoids. The Laskowski 5-1 (windward margin) core is interpreted to be in deeper water than the Laskowski 4-1. Most fauna were found as rubble, debris or molds (e.g. brachiopods). This may be due to the increased energy on the windward margin breaking down fossils, followed by dissolution and recrystallization rendering the fauna unidentifiable. Additionally, the increased water energy on the windward margin winnowed finer-grained material away and increased the precipitation of cements. Later dissolution of these cements and other skeletal grains produced moldic and vuggy secondary porosity. This also made identification of fauna more difficult.

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Density of Fauna Across Wells in Ray Reef

5 4.5 4 3.5 3 2.5 2 Density (%) 1.5 1 0.5 0 Lask5 Lask4 BTK Halmich Jacob Percy

Unid Stromatoporoid Tabulate Rugose Bryozoan Crinoid Brachiopod

Figure 9: Density of fauna across wells in Ray Reef. Density of fauna is the percentage of the core that is covered by each category of fauna when the total slabbed core surface equals one hundred percent. Highest densities are found in the crest cores (BTK and Halmich). Laskowski 5 (Lask5) and Laskowski 4 (Lask4) wells are on the windward side of the reef. The Halmich (Hal) and Busch-Tubbs-Kuhlman (BTK) wells are on the reef crest. The Jacob and Percy wells are on the leeward side of the reef. Refer to Figure 3 for well locations. (unid = unidentifiable).

Diversity

Chappell (1980) created theoretical curves to account for the lateral and vertical diversity of corals caused by the interaction of biotic and physical factors such as light, hydrodynamics, sediment influx, and subaerial exposure. On modern coral reefs, the general trend in diversity on the fore-reef is that there is a gradual increase in diversity in shallow water up to wave-base. Further down the slope, diversity decreases with deeper water due to increases in sediment influx as well as a reduction in light intensities. On the reef flat, diversity increases with water coverage

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and less subaerial exposure but decreases toward the reef front where wave energy is highest. In the back reef area, diversity increases with shallow water and lower water energy and less sediment, reaches a point where it remains constant, and then decreases with depth as light intensity is reduced (Chappell, 1980). In Ray Reef, diversity was lowest in the reef facies of the deeper leeward Percy core with only halysitid and possible alveolitid tabulate corals and the deeper windward core of Laskowski 5 with only thamnoporid and auloporid tabulate corals (Figure 10). The Laskowski 4 windward core had higher numbers of phyla and also had more diverse tabulate corals including favositid, thamnoporid, halysitid, and auloporid specimens as well as the colonial rugose coral Flethcheria sp (Figure 10) consistent with a more shallow forereef interpretation. The Jacob 1-36 (crest to leeward margin) core had several instances where 7 of 8 possible phyla were present in the reef facies and favositid, thamnoporid, halysitid, and auloporid tabulate corals were present (Figure 10) consistent with a reef flat to back reef interpretation. The Halmich 2-1 (crest) and BTK 1-36 (crest) cores were the most diverse with several instances of 5-8 phyla represented in the reef facies and included all of the previously listed types of tabulate corals (Figure 10) consistent with a reef flat or crest interpretation.

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Diversity Across Ray Reef by Well and Facies

8 7 6 5 4 3 2 1 0

Number of Phyla Present (Max = 8) Lask5 Lask4 BTK Halmich Jacob Percy

Exp FS 5-Restriced 4-Skel Grnstn 3A-Reef Core 3B-Reef Debris 2-Bioherm

Figure 10: Diversity by facies across wells in Ray Reef. Diversity is expressed as the number of phyla represented with a maximum of eight possible. Generally, crest cores show the highest diversity in the Bioherm and Reef Core Facies with the more marginal windward core (Lask4) with similar values and the crest to leeward (Jacob) core showing similar values in the Reef Core Facies and the Reef Debris and Skeletal Grainstone Facies. The lowest diversities were in the deeper windward foreslope Lask 5 and deeper leeward Percy cores. Laskowski 5 (Lask5) and Laskowski 4 (Lask4) wells are on the windward side of the reef. The Halmich (Hal) and Busch- Tubbs-Kuhlman (BTK) wells are on the reef crest. The Jacob and Percy wells are on the leeward side of the reef. Not all facies are present in all wells. Refer to Figure 3 for well locations. Exp = exposure; FS = flooding surface.

Distribution and Community Replacement vs. Succession

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(Copper, 1988). Some workers have suggested using the term “community replacement” as was done by Johnson (1977) and Rollins et al. (1979) when succession of organisms is thought to be due to external forces such as climate or sea level change (Copper, 1988). Other biologists have used the term “colonization sequence” (Gray, 1981) in order to avoid the term “succession” and its implications (Copper, 1988). The intention of this paper is not to investigate ecological succession theory, but rather to provide additional evidence to previous studies (Ritter, 2008; Wold, 2008; Qualman, 2009) which have used sequence stratigraphy to improve the model used in these pinnacle reefs to show their lateral and vertical heterogeneity. This study seeks to show that the changes in community replacement are repeatedly seen throughout the main sequences of reef growth in this Wenlock pinnacle reef complex and that this affects the heterogeneity of these reefs and their reservoir characteristics. Since sequence stratigraphy was used to determine third order sequence boundaries, changes seen in the reef community at this level may be considered allogenic and will be referred to as “community replacement” as reflected in shallowing upward sequences which coincide with eustatic sea level changes. This is not a new method or interpretation, but a combination of newer (sequence stratigraphic) methods with older interpretations (Klovan, 1974; James 1983; James and Bourque, 1992; Gischler, 1995). Riding (1981) in describing the sediment, biota, size and geometry of four different types of bioherms and biostromes in the Silurian of Northern Europe, concluded that the different types of reefs were “stages in the response of reef building organisms to progressively shallower and more turbulent conditions”. The higher frequency fourth order sequence boundaries may be autogenic and due to “true succession” caused by the organisms themselves or they 245

may simply be “community replacements” due solely to external forcings. This paper will not attempt to differentiate the cause, but will use the term “community replacement” for all observed changes. Additionally, this paper will incorporate the trends of increasing diversity and biomass (as interpreted from perimeter measurements) as indicators of community replacement. As an aside, these are typically among the attributes used in determining ecological succession (Chappell, 1980; Copper, 1988; James and Bourque, 1992; Perrin 1995; Scrutton 1999).

Community Replacement

The community replacement expressed in a shallowing upward sequence is best visualized by plotting the average perimeter of fauna on the x-axis and the core depth in feet on the y-axis in a spindle diagram. As can be seen in Figure 11 of the Busch-Tubbs-Kuhlman (BTK) (crest) core, there is a general trend between increasing stromatoporoid and tabulate coral perimeter (or biomass) with shallowing upward sequences marked by third order sequence boundaries and high frequency sequences. This is seen throughout the cores across the reef. When analyzed in sequences, the pattern of reef growth becomes more apparent and is in stark contrast with the “bucket models” of the 1970’s and 1980’s that imply 300-600 ft of uninterrupted reef growth.

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n te a la d m u zo h b o c Unid Stromtro Tabulate Rug Bryz Crin Brach Unid S Ta Rugose Bry Crinoi Bra -2960 -2980 2990 HFSB -3000

-3020

-3040 3058 HFSB -3060

-3080 3100 -3100 SB3

-3120 Core Depth (ft.) (ft.) Depth Depth Core Core 3128 HFSB 247

-3140

-3160 3175 SB2 -3180 3189 HFSB -3200 3204 HFSB

-3220

-3240

-3260 3264 HFSB 120 240 360 480 600 720 840 960 1080 Average Perimeter (mm) Figure 11: Busch-Tubbs-Kuhlmann (BTK) core showing average perimeter of fauna in millimeters (x-axis) with core depth in feet (y- axis). High Frequency Sequence Boundaries (HFSB) are marked across faunal categories with dashed lines and their corresponding core depth is noted on the left. Third order Sequence Boundaries (SB) are marked across faunal categories with solid lines and their corresponding core depth is noted on the left. Note the increase in faunal perimeter, especially in framebuilding stromatoporoids (Strom) and tabulate corals, coincident with sequence boundaries. This is suggestive of biomass increasing with shallowing upward sequences which indicates community replacement.

Cementation

Syndepositional cementation was expected to be highest in the windward cores based upon previous work (e.g. Grammer et al., 1993a) and this was found to be true in this study with the Laskowski 4-1 (windward margin) core containing 28.12% cement. However, the windward Laskowski 5-1 core had 15.8% cement which was only slightly higher than the cores from the leeward side with the Percy 2-2 (leeward margin) at 12.20% and the Jacob 1-36 (crest to leeward margin) at 13.63% (see Table 4). The percentage of cement was lowest in the leeward Percy 2-2 core with 12.20%. The crest Halmich 2-1 core had 24.74% and the crest BTK 1-36 core had 21.02% cement (Table 4). Based upon the presence of moldic and vuggy porosity observed in the core, it is interpreted that there was secondary dissolution of some cements in the windward cores. Therefore, the original amount of syndepositional cementation of these cores is not known but is presumed to be higher than the estimated amounts presented here.

Comparisons with Ancient Analogs

Generally, the community succession put forth by Klovan (1974) when working on the Western Canadian Devonian reefs is the closest to what is observed in Ray Reef. As Klovan suggested, the Thamnoporid-Disphyllid-Alveolites community was observed in lower energy settings below storm wavebase. Small rugose corals could be added to this community for Ray Reef in the Silurian of the Michigan Basin southern pinnacle belt trend. Intermediate energy settings contained a tabular stromatoporoid community which was interpreted by Klovan to be analogous to the modern Diploria-Montastrea-Porites community located between wavebase and storm 248

wavebase. Rugose corals and tabulate corals with similar domal-multilobate- branching forms could be added to this community for Ray Reef. The highest energy settings in Klovan’s model included the massive stromatoporoid community located between sea level and wavebase. In this study, domal to hemispherical stromatoporoids were included in the higher energy massive stromatoporoid community with specimens displaying ragged non-enveloping forms interpreted as being in higher energy settings than smooth enveloping forms. James and Bourque (1992) described reef facies and water depth differently. They considered the Reef Front Facies to comprise water depths between 10 m (the base of surface wave action) and 100 m with the Reef Crest Facies to a depth of 15 meters at most. This is different from the Klovan model with the highest energy in the 3-9 meter range (10-30 ft.) corresponding to just below sea level to wave base, the intermediate energy in the 9-21 meter range (30-70 ft.) corresponding to wave base to storm wave base range, and the lowest energy from 21-24 meters (70-85 ft.) considered below storm wave base. James and Bourque (1992) also differentiated stromatoporoid forms and energy settings by placing encrusting or large non-enveloped, ragged margin (i.e. massive) stromatoporoids in the high energy reef crest facies and the totally enveloped smooth stromatoporoids in quiet water below wave base or in sheltered areas in the back reef with domal, bulbous, and dendroid forms. The current study also found domal stromatoporoids and interpreted the ragged, non-enveloped ones as being in higher energy settings than those that were smooth and enveloped. The BTK (crest) core contained a colonial rugose coral Fletcheria sp. just above a HFSB between 3053’-3056’ and above SB3 along with thamnoporids, rugose corals, encrusting stromatoporoids and bryozoans. Gischler (1995) noted very similar 249

fauna in the leeward forereef where a possible channel connected a lagoon to the open ocean in a Devonian atoll. Gischler assigned it to a quiet, low energy environment. The BTK (crest) core is interpreted as being on the crest to leeward side of the reef in a similar environment as that described by Gischler and would be consistent with a “leeward forereef” interpretation. Schneider and Ausich (2002) compared the diversity of fauna in a patch reef, located in a southwestern Ohio quarry of Early Silurian age, in the Brassfield Formation to the Jupiter Formation of Quebec. Findings on Ray Reef compared to Schneider and Ausich (2002) are in agreement that stromatoporoids are more abundant on the leeward side than the windward side. In the Ray Reef, however, stromatoporoids were most abundant in the cores from the reef crest. Also, Schneider and Ausich (2002) found solitary and colonial rugose corals more abundant on the windward side. In Ray Reef, no rugose corals were readily identifiable on the windward side, although this may be due to secondary diagenesis as previously discussed. Identifiable rugose corals in Ray Reef were found more often in lower energy settings and gradually increased in size and decreased in abundance as sequences shallowed upward toward sequence boundaries. Schneider and Ausich found that tabulate corals, crinoids, and bryozoans were evenly distributed across the reef. In Ray Reef, bryozoans and crinoids were most abundant in the reef crest cores. Crinoids and bryozoans were sparse in the windward cores. Tabulate corals were more abundant as thamnoporids in lower energy settings and were replaced by favositids with increasing energy, as reported by Klovan (1974). The larger favositids were found in the higher energy settings but were not found with the highest energy (ragged domal, non-enveloped) stromatoporoids.

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Modern Analog – Tongue of the Ocean, Bahamas

The Niagaran reef and slopes of the Michigan Basin during Silurian time were similar in some ways to the margins and upper slopes of the intraplatform basins in the Bahamas. Variations in the composition and make up of marginal deposits as well as upper slope deposits in response to windward and leeward positioning suggest that many of the same processes may be operating in each environment. In addition, the modern day Bahamas are located in a subtropical setting affected by easterly trade winds similar to the Silurian reefs in the Michigan Basin as discussed previously. Grammer et al. (1993a) have shown that several characteristics of the margin and upper slope environment such as slope geometry, facies and faunal distribution and relative amounts of cementation, in the Tongue of the Ocean (TOTO), Bahamas, were influenced by the windward or leeward orientation of the margin. Grammer et al. (1993a) divided the foreslope of margins in Tongue of the Ocean (TOTO) into four zones, each with a distinct morphology: 1) Platform Edge, 2) The Wall, 3) Cemented Slope, and 4) Sediment Slope (Figure 12). The following is summarized from Grammer et al. (1993a).

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Figure 12: Data gathered from 134 dives in a submersible from 1987, 1988, and 1990 was synthesized to construct this representative profile of upper slope environments around Tongue of the Ocean, Bahamas. No vertical exaggeration. Modified from Grammer and Ginsburg (1992).

Platform Edge

The platform on the edge of TOTO margin is in shallow water and contains Holocene-aged sediments. These sediments may reach thicknesses of 24 meters near the leeward edge of the platform (Palmer, 1979). Off the edge of the platform, reefs grow to depths of 40-60 meters. The windward (east-facing) margins have better developed reefs. Sediment chutes frequently dissect the reefs and continue to the escarpment.

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The Wall

This escarpment has declivities of 70-90 degrees. The wall is present from depths starting at 40-60 meters and continues down to 130-140 meters. The wall supports a variety of organisms including deep-water, plate-like corals (e.g. Montastrea annularis and Agaricia spp.), encrusting coralline algae, boring sponges, sclerosponges, and at least three species of Halimeda (H. opuntia, H. copiosa, and H. cryptica). Abundance and diversity of organisms is greater on windwards margin than on leeward margins with the majority found higher in the water column (50-75 meters).

Cemented Slope

From the base of the wall (130-140 meters) to depths greater than 365 meters is a well-lithified surface with steep angles of 35-45 degrees. The slope has decimeter thick internal bedding which consists of elongated lenses of course or angular debris. Most finer-grained sediment from the platform bypasses this cemented slope. Therefore, there is only a thin veneer of unconsolidated sediment (less than 1-2 cm) found on the cemented slope surface and it is usually only present in localized topographic lows. Bioclasts and cements from these slopes were AMS

radiocarbon dated at 10,000-14,000 ybp. This time frame corresponds to the latest transgression after the last glacial maximum (sea level lowstand) of 18-20 kybp. Also characteristic of the lower cemented slope are localized, cemented-in- place lenses of debris. They consist of large talus blocks or piles of rubble on the downslope end and coarse-grained sands, gravels, and boulders on the upslope end. Most of the sediment is angular or elongate in shape showing some imbrication in the upslope direction, indicative of grain flow deposition. These trains of sediment are 253

interpreted as being the last episodes of deposition on the cemented slope. Neptunian dikes (arcuate, convex-up cracks) run parallel to the slope contours and are common on the cemented slope surface and may be areas of incipient slope failure.

Sediment Slope

At the base of the cemented slope, a wedge of unconsolidated sediment onlaps the cemented slope obtaining 25-28 degree angles. This sediment is a mixture of skeletal (dominantly Halimeda) and nonskeletal (dominantly hardened peloids) sands and varying amounts of carbonate mud. These sands are derived from both the wall and outermost margin of the platform as revealed by compositional analysis. There are minor amounts of sands from the platform interior (Grammer and Ginsburg, 1992). Droxler and Schlager (1985) found that sediment from cores taken further in the basin of the cul-de-sac of TOTO were mud-sized carbonate from the platform with subordinate contributions from planktonic material.

Variation Between Windward and Leeward Margins

There are considerable differences between the amounts of Holocene

sediment deposited on the windward margin when compared to the leeward margin. Using a submersible, Grammer et al. (1993a) saw that unconsolidated, fine-grained sediment began to onlap onto the cemented slope at a depth of more than 360m on the windward margin but was seen at a depth of only 240m on the leeward margin suggesting that the leeward margin had a thicker sediment wedge. This was confirmed using seismic reflection profiling which revealed up to 80 meters of platform derived sediment deposited on the leeward margin and only 20 meters of 254

sediment deposited on the windward margin (Figure 13). The cause for this difference was presumed to be more sediment being swept off of the open leeward platform. Wilber et al. (1990) reported similar findings along the leeward margin of Great Bahama Bank. Additionally, during one submersible dive carbonate mud was seen being swept off of the platform during 20 knot east-southeast winds that had been blowing for 4-5 hours (Grammer and Ginsburg, 1992). As Hine et al. (1981) suggested, sand-sized particles on the leeward margin are probably only entrained during storms.

Figure 13: Seismic profile of the leeward margin of the Tongue of the Ocean showing an 80+ meter Holocene sediment wedge and a distinct decrease in declivity. (Grammer et al., 1993a; Palmer, 1979)

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Characteristics of the Steeply-Dipping Cemented Slope Deposits

The interior of the cemented slope contains well- to very well-indurated, poorly sorted, skeletal packstones-grainstones with textures locally variable to wackestones. In most of the samples, grain size varies from silt to pebble size. Localized clasts of coral up to 30 cm long are present in some hand samples. Of the sand and coarser fraction, thin-section point-count revealed 94% to be skeletal components. The rocks on the cemented slope are mostly composed of Halimeda (48%) with lesser amounts of coralline algae (13%), coral (11%), mollusks (8%), benthic foraminifera (5%), bryozoans (3%), serpulid worm tubes (3%), echinoderms (2%), and planktonic foraminifera (2%). Coral and mollusk fragments, determined by point-counting, are probably underestimated for two reasons: 1) more than 50% (visual estimate) of some samples were of silt-sized sediment fraction and were dominated by coral and molluscan fragments. These were not counted during point- counting of the sand and coarser fraction; 2) because of their large size, cobble to boulder sized clasts of coral were collected but not included in the thin-section point- count data. Due to the high percentage and the compositional distribution of skeletal fragments in these samples, the rocks were interpreted as being derived from a reef or reef-like environment. The morphology and species of corals (platy Agaricia spp.; platy and massive Montastrea annularis; Madracis mirabilis, Madracis decactis, and Siderastrea sidereal) as well as the dominant species of Halimeda (primarily Halimeda copiosa) also suggest that this reef was growing in a relatively deep (greater than 20 m) environment (Blair and Norris, 1988; Johns and Moore, 1988; Suchanek, 1989). 256

Cementation

The samples taken from the surface and near-surface have distinctly different cement types and abundances from the samples taken from the interior of the cemented slope. The rocks on the surface or near surface are thoroughly bioturbated, matrix-rich wackestones and packstones and are generally cemented with matrix micrite and peloidal micrite (approximately 80-90% of cement by visual estimate), with lesser amounts of bladed Mg-calcite (approximately 10%) and fibrous aragonite (<5% by visual estimate). Rocks from the interior of the cemented slope have cement distributions that average approximately 31% bladed Mg-calcite, 18% matrix micrite (Mg-calcite), 13% fibrous aragonite, 12% botryoidal aragonite, and 12% peloidal micrite (Mg- calcite). Total abundance of cement varies from approximately 15-50% and averages 20-30% (by visual estimate). As expected, cement is less abundant in the packstones than in the grainstones. The majority of cementation took place within a few hundred years. This is suggested by the similarity of radiocarbon ages between some botryoidal cements and coexisting skeletal fragments, as well as data presented on the growth rates of botryoidal aragonite cements (Grammer et al., 1993b). Porosity within the samples varies from ~0-25% (combined point-count and visual estimates).

Similarities between TOTO, Bahamas and the Silurian Michigan Basin Reefs and Margins

257

more gradual changes in facies. Wold also found, as Grammer et al. (1993a) had documented, that the windward margin with its predominantly skeletal grainstones had higher porosity and permeability values compared to the nonskeletal grainstones of the leeward margin (Figure 7). In this study of relative abundance and general distribution of fauna in Ray Reef, there are general similarities with findings in the Bahamas (Grammer et al., 1993a) even though the fauna are different. Studies conducted by Grammer et al., 1993a found that faunal abundance and diversity were greater near the top of the wall (50-75 meter water depth) and decreased with depth in the Tongue of the Ocean. A similar trend was recognized in Ray Reef with faunal abundance and diversity increasing upsection in what have been interpreted as high frequency shallowing upward cycles (this study, Wold (2008) and Ritter (2008)). Similarities are also observed in the increased amount of syndepositional cement found in the windward forereef slope of Ray Reef and Tongue of the Ocean (Grammer et al., 1993a). Grammer et al. (1993b, 1999) documented the rapid growth rates of cements (8-10 mm/100 years) indicating rapid cementation rates (10s-100s of years) of the slope deposits, which allowed slopes to retain the high angles of declivity. Grammer et al. (1993) found pore-filling botryoidal cement in the coarse skeletal packstones and grainstones of the interior of the marginal (“cemented”) slope fronting the TOTO, Bahamas. In Ray Reef, the windward Laskowski 4 core has higher amounts of syndepositional cement, including botryoidal cements, as well as syndepositional vertical fractures (i.e. neptunian dikes) which are also common on the surface of cemented slopes in Tongue of the Ocean, Bahamas (Grammer et al. 1993a).

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Reservoir Characteristics

Although this study was primarily concerned with the relative abundance and general distribution of fauna, the application of these results involves reservoir characteristics of porosity and permeability. Of special interest was whether or not trends, or lack of trends, seen by previous workers could be observed in Ray Reef. A cross-plot of porosity and permeability averages for the Reef Core Facies in all wells across Ray Reef shows the highest values in the windward Lask4 core and the lowest values in the windward Lask5 core (Figure 14). This would appear at first glance to indicate that there is no relationship between windward or leeward positions on a reef and reservoir characteristics of porosity and permeability. However, when other aspects such as sediment texture, reef morphology, and diagenesis are taken into consideration, these apparent contradictory findings can be explained.

Windward vs. Leeward Reef Core Facies 3a Average

80 70 Lask 5 60 50 Lask4 40 Halmich 30 BTK 20 Jacob

Permeability (mD) Permeability 10 0 024681012

Porosity (%)

Figure 14: Cross-plot of average values for permeability and porosity in the Reef Core Facies (3a) for five cores across Ray Reef. The Laskowski 4 core, interpreted as being in a windward forereef position, shows the highest values. The lowest values are in the Halmich (crest), BTK (crest), and Lask 5 (windward) cores. The Jacob (crest to leeward) core has intermediate values. Whole core analysis was not available for the leeward Percy core. 259

In studying three cores from the northern and southern pinnacle reef trends in the Michigan Basin, Ritter (2008) found that porosity and permeability values were higher near 3rd order sequence boundaries due to preferential dissolution and porosity enhancement associated with subaerial exposure. Ritter (2008) also found, in contrast, that porosity and permeability values were lower in facies closer to 4th order sequence boundaries due to porosity occlusion resulting from early cementation. Using the 3rd order sequence boundaries identified by Wold (2008), this study found that the three 3rd order sequence boundaries did not always show the same trends. The windward Laskowski 4, the crest BTK, and the crest Halmich cores show that there is a general trend in porosity and permeability values increasing from the transgressive phase to the regressive phase in the first sequence up to SB2 (Figure 15a, 15b and 15c). In the second sequence, between SB2 and SB3 porosity and permeability values again increase from the transgressive to the regressive phase (Figure 15a, 15b and 15c). In contrast, the third sequence from SB3 to SB4 shows the porosity and permeability values either remaining about the same or decreasing from the last transgressive phase to the regressive phase (Figure 15a, 15b and 15c). Also, the porosity and permeability values of the transgressive phase increases substantially from Sequence 1 to Sequence 2 to Sequence 3 (e.g. the Lask4 values for the transgressive phase of Sequence 1 are ~8 mD/6%, Sequence 2 increases to 75mD/11%, and Sequence 3 increases to 100 mD/13%) in the Lask4 windward and BTK crest cores. In the Halmich crest core the transgressive phase values increase from Sequence 1 to Sequence 2 but only slightly increase to Sequence 3. However, the results for the Jacob (crest to leeward) core (Figure 38d) were different. Although the Jacob (crest to leeward) core showed an increase in the porosity/permeability values from the transgressive phase to the regressive phase 260

during the first sequence up to SB2, as was seen in the Lask4, BTK, and Halmich cores, in the second sequence from the transgressive phase to the regressive phase between SB2 and SB3, permeability values decreased, in contrast to what was observed in the windward and crest cores. The cause for this decrease is unknown, but may have been due to this area of the reef transitioning from a crest position and exposure to a more leeward position, as will be explained in the next section. The transition to more mud-rich sediments with decreased fauna would decrease the original porosity/permeability values and seal those sediments from secondary dissolution enhancement.

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Windward Lask 4 Reef Core Facies 3a 3rd Order Sequence Averages R3001-3052 Sequence 3 1000 T3052-3067 SB3

Crest BTK Reef Core Facies 3a 3rd Order Sequence Averages T2980-2989

R2990-3072 (exp) 100 Sequence 3 T3072-3100 SB3

Sequence 3 R3100-3161 Sequence 2 10 Sequence 2 T3161-3174 SB2

Sequence 1 R3174-3220 Sequence 1

Permeability (mD) Permeability T3220-3264 Facies 2 1 2952-2974 Facies 5 0246810 Porosity (%) 2975-2980 Facies 3a

262

Crest Halmich Reef Core Facies 3a 3rd Order Sequence Averages R2934-3018 Sequence 3 100 T3019-3027 SB3

R3029-3108 Sequence 2 Sequence 2 T3109-3142 SB2 10 R3143-3204 (F2 & F3) Sequence 3 Sequence 1 Sequence 1 Permeability (mD) Permeability T3205-3218 (F2) 1 0246810 Porosity (%)

Crest to Leeward Jacob Reef Core Facies 3a 3rd Order Sequence Averages R2935-2992 (F5&4)

Figure 15: Cross-plot of average values for permeability and porosity during the transgressive and regressive phases of the three 3rd order sequences across Ray Reef. Most all of the sequences, except for the Jacob sequence 2, show increases in porosity and permeability going up in sequence and from the transgressive leg to the regressive leg (except for sequence 3). Note that Sequence 3 on the Jacob core is broken out between the regressive phase Reef Debris Facies (F3b – hollow triangle) and regressive phase Reef Core Facies (F3a – filled triangle) in order to show that values increased in the Reef Debris Facies part of the sequence and then decreased in the Reef Core Facies part of the sequence. 263

To further explore these trends, it is useful to look at the facies and faunal morphology and density in each of these three cores during these three sequences.

Analysis of Core up to Sequence Boundary 2 (SB2)

In the first sequence, the Lask4 (windward), the BTK (crest), and the Halmich (crest) cores are changing from a mud-rich bioherm facies to a reef facies (Figure 16). This accounts for the increase in porosity/permeability values from the transgressive leg to the regressive leg up to SB2. From the bottom of the cores up to SB2 (Figure 16), the Lask4 windward core had a Bioherm Facies of mostly crinoid debris and a Reef Core Facies. The Halmich (crest) core had a Bioherm Facies and a Reef Core Facies. The BTK (crest) core had a Bioherm Facies, a flooding surface with a high density of stromatoporoids, and a Reef Core Facies consisting of equal densities of stromatoporoids and crinoid debris. The BTK core also had the highest density of all the cores and had a diverse representation of fauna, inferring that it was a well established and healthy part of the reef. The Jacob (crest to leeward margin) core included a Reef Core, and Reef Debris Facies of approximately 1% or less faunal density, a Skeletal Grainstone Facies consisting of 7% bryozoans and 7% crinoid debris, and an exposure surface. From the facies and faunal density descriptions, the Lask4 (windward margin) core was interpreted as being deeper down, around fair weather wave base, on the windward foreslope. The Halmich (crest) and the BTK (crest) cores are thought to have been on the reef crest to flat and closer to sea level since the Halmich shallows to a grainstone and the BTK shows a flooding surface. The Jacob (crest to leeward margin) was probably on the upper portion of leeward foreslope and closest to sea level as there is evidence of subaerial exposure. These interpretations support 264

increasing porosity and permeability values due to early cementation and later dissolution in the crinoid and debris rich windward Lask4 core. The shallowing of the Halmich (crest) core from a mud-rich bioherm to a skeletal grainstone would account for the increase in porosity and permeability. The change from a muddy crinoid and bryozoan rich bioherm to a reef core with equal densities of stromatoporoids and crinoids allows for increased porosity and permeability values in the BTK (crest) core. Core from the Jacob (crest to leeward) well also showed an increase in the porosity/permeability values from the transgressive phase to the regressive phase during the first sequence up to SB2 (Figure 15c and 15d). However, the Jacob (crest to leeward) core was already in a reef to skeletal grainstone facies in the first sequence and experienced an exposure surface at SB2. It is thought that dissolution due to exposure greatly increased the porosity/permeability values from the first sequence up to SB2.

265

266

Figure 16: Facies, texture, faunal density, percentage of cement, percentage of porosity, and permeability (mD) below Sequence Boundary 2 for all six wells studied across Ray Reef. The Lask4-1 (windward), the Halmich (crest), and the BTK (crest) cores are transitioning from mud-rich Bioherm Facies into Reef Core Facies. The Jacob well was already in an established reef position as shown by the Reef Core, Reef Debris, and Skeletal Grainstone Facies consisting mostly of crinoid and bryozoan debris, and exposure surfaces. Since the BTK and Jacob cores are the only ones below Sequence Boundary 2 that show an exposure surface, they are interpreted to have been closer to sea level than the other cores during this sequence. 267

Analysis of Core from Sequence Boundary 2 (SB2) to Sequence Boundary 3 (SB3)

In the second sequence (Figure 17), the Lask4 (windward) and BTK (crest) cores both contain only reef facies skeletal wackestones –packstones. The presence of skeletal wackestones-packstones that were not sealed by finer grained sediments could be the reason for the increased porosity/permeability values from the sequence below. During the third sequence from SB3 to SB4, the Lask4 (windward) core shallows up from reef facies, to skeletal grainstone facies, to restricted cyanobacterial mat facies while the BTK (crest) core changes from reef facies, to reef debris facies, back to reef facies, an exposure interval, reef facies, and finally a restricted cyanobacterial mat facies. The change from a reef facies to the restricted cyanobacterial mat facies and anhydrite sealed and prevented the preferential dissolution of the surface during the last exposure causing the porosity/permeability values to be lower. Between SB2 and SB3 (Figure 17), the Lask4 (windward margin) core consisted of only a Reef Core Facies with a very low faunal density that included less than 1% of fauna including brachiopods, tabulate corals, and unidentified fauna and was interpreted as being on the windward foreslope between sea level (SL) and the fair weather wave base (FWWB). The BTK (reef crest) core was much more diverse including all faunal categories identified, with over 7% density of stromatoporoids, over 4% tabulates, and over 3% crinoid debris. The BTK core is also interpreted to have been between SL and FWWB during this time. The Halmich (crest) core was composed of Reef Core wackestones to grainstones with a diversity of fauna. The Jacob (crest to leeward margin) core had both a Reef Core Facies of slightly more than 1% tabulates and a Skeletal Grainstone Facies with 5% crinoids and 2%

268

brachiopods and an exposure surface and was interpreted as being on the leeward foreslope. Porosity and permeability values increased slightly for the Lask4 (windward margin) core presumably due to secondary dissolution of syndepositional cements. The Halmich (crest) core also showed an increase in porosity/permeability values which is probably due to the change in texture to a skeletal grainstone. The BTK (crest) core shows a flooding surface at SB3 and vuggy and moldic porosity implying dissolution. However, porosity and permeability decreases in the Jacob leeward forereef core may be explained not by the low densities of fauna in the Reef Core Facies, which were similar to the previous sequence up to SB2 of around 1% of tabulates and stromatoporoids, but rather to the decrease in the density of fauna in the Skeletal Grainstone Facies (from 7% crinoids and 7% bryozoans up to SB2 and only 5% crinoids and 2% brachiopods at SB3). Additionally, below the exposure surface at SB3, leaching and salt fill is noted. Both the decrease in the skeletal grainstone facies and leaching followed by salt plugging may account for the decrease in porosity and permeability values in the Jacob core.

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270

Figure 17: Facies, texture, faunal density, percentage of cement, percentage of porosity, and permeability (mD) between Sequence Boundary 2 and Sequence Boundary 3. Sequence Boundary 3 shows strong control over faunal density as there is an extreme paucity in fauna below SB3 in the windward Laskowski 4 and Laskowski 5 cores and to a lesser extent in the crest-leeward Jacob core. The increase in permeability in the Lask 4 core is thought to be due to dissolution of cements and secondary porosity and permeability enhancement. The Jacob (crest to leeward) and BTK (crest) cores also show possible exposure and flooding surfaces at SB3 with low poro/perm values. The Laskowski 5 (windward) core completes its reef life cycle between SB2 and SB3 with the end of reef growth at this position noted by a Restricted Facies consisting of cyanobacterial mats at SB3. The Halmich core (crest) shows a change to a Reef Debris Facies consisting of skeletal grainstones at SB3 consisting mostly of crinoids and unidentifiable debris and medium poro/perm values. 271

One of the most striking characteristics of the Laskowski 4 (windward margin) core is the visually apparent moldic and vuggy porosity (Figure 18) that is more connected than the molds and vugs of the representative Jacob (crest to leeward margin) core (Figure 19). The enhanced porosity of the windward margin core is hypothesized to be due to the lack of fine-grained sediment originally deposited due to the higher energy of the wind driven water onto the reef. The flushing of water on the windward margin would have made precipitation of cement between grains more favorable due to a constant resupply of ions and carbon dioxide outgassing. This increased cementation also accounts for the higher degree of declivity on the windward margin of the reef as seen by Grammer et al., (1993a) and interpreted by Wold (2008) on Ray Reef in comparison to the leeward margin. It is hypothesized that the preferential secondary dissolution of some of those cements may be the cause for the enhanced vuggy porosity seen in the cores at present. Since the leeward margin had more fine-grained sediments which fell out of suspension due to a decrease in water energy, there may have been less intergranular space and less favorable conditions for precipitation of cements due to the less energetic and ion depleted waters.

272

Figure 18: Core slab a) without pore space highlighted in black and b) same core slab showing enhanced porosity due to secondary dissolution of cements highlighted in black from a windward core (Laskowski 4). Whole core analysis values are porosity () = 16.4%, permeability (K) = 121 mD.

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Lask4 3157’ (=12.2%, K=124 mD)

a) b) Jacob 3063’ (=7.1%, K=1.2 mD)

Figure 19: CT scanned cores comparing moldic and vuggy porosity that has (a) and has not (b) been enhanced due to secondary dissolution showing extent of permeability enhancement. Orange fill denotes pore space. 274

However, the Laskowski 5 core is also on the windward side of the reef but has the lowest average porosity and permeability values. This can be attributed to two things: 1) the Laskowski 5 core only contains 50 ft. of sediment from between SB2 and SB3 as compared to the Laskowski 4 core which contains 220 ft. of sediment from below SB2 to above SB4 and 2) the Laskowski 5 core contains only three facies, two of which are mud-rich and have poor original porosity and permeability: Bioherm Facies 2 (mud rich), Reef Core Facies 3, and Restricted Facies 5 (mud and cyanobacterial mat rich). The highest framework density is in the Restricted Facies with cyanobacteria as the only identifiable fauna. In the reef core facies, the identifiable fauna were thamnoporid and auloporid tabulate corals along with brachiopod molds and crinoid pieces. This would indicate a lower energy environment below storm wave base (70 ft.) according to Klovan. It is interesting to note that no rugose corals were seen in this core. Additionally, an extreme paucity of fauna is found in both the Laskowski 4-1 and in Laskowski 5-1 cores directly below SB3. Sequence Boundary 3 is marked by an exposure interval/flooding surface in the Jacob (crest to leeward) and a flooding surface in the BTK (crest) core. It is not known whether this lack of fauna is due to diagenesis, an environment at the time of deposition that was too harsh for viability, or possibly sediment bypassing a cemented slope as was shown in the TOTO (Grammer, 1993a) and being deposited as a “lowstand fan” (Figures 20 & 21). This would account for the severe paucity of fauna on the higher foreslope Laskowski 4 (windward) core and the lack of fauna and the low porosity and permeability of the Laskowski 5-1 (windward) core located deeper on the foreslope due to the finer- grained sediment being deposited here as a “lowstand fan”.

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Figure 20: Sequence of diagrams illustrating the development of the Tongue of the Ocean foreslopes during the last ~20,000 years. Reef-dominated, coarse talus debris is deposited during the transgressive phase before sea level reaches the top of the platform. These deposits may be either good reservoirs or conduits. After the platform is flooded, sediment is transported down slope creating highstand wedges. Fine-grained sediments bypass the steep slopes and are deposited in “lowstand fans” which are of poor reservoir quality. (From Grammer and Ginsburg, 1992).

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Figure 21: Illustration of the present-day 3-D interpretation inferred from surface characteristics of the foreslopes of the Tongue of the Ocean, Bahamas (modified from Grammer and Ginsburg,1992). A near-vertical escarpment characterizes the margin. This formed as a result of erosional during multiple Pleistocene-Holocene sea level fluctuations. Constructive growth of organisms augmented the erosion process, resulting in 70-90 slope angles for the escarpment. Deposition of the steeply dipping (35-45) slope deposits, shown in light purple, occurred during the lowstand and early rise of sea level following the last major lowstand. These units have high initial porosities and are composed of sediments derived from fringing reefs growing along the escarpment. The highstand wedge of sediment deposited downslope is comprised of fine-grained sediment derived from the platform top. This wedge of sediment, which is as much as 90 m thick, was deposited during the last 7000 yr so when the platform top was fully flooded. See Grammer and Ginsburg (1992) and Grammer et al. (1993a) for further discussion.

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Analysis of Core Above Sequence Boundary 3 (SB3) or between SB3 and Sequence Boundary 4 (SB4)

The last sequence studied, between SB3 and SB4 (Figure 22), shows the Lask4 (windward margin) core containing a Reef Core Facies of less than 1% density with syndepositional vertical fractures, Skeletal Grainstone Facies consisting solely of stromatoporoid debris of less than 5%, and a Restricted Facies of cyanobacterial mats of over 20% density. The Halmich (crest) core is transitioning from a peloidal

278

The presence of both stromatoporoids and cyanobacterial mats in the exposure surface of the BTK (crest) core shows the rapidity of the change in depositional environment and the corresponding change in facies. The Lask4 (windward margin), BTK (crest), and Jacob (crest to leeward) cores all show the end of reef growth and the development of Restricted Facies with cyanobacterial mats. The higher density of cyanobacterial mats in the Lask4 (windward margin) and BTK (crest) cores may account for the decrease in porosity and permeability seen in these cores during this sequence. The Jacob (crest to leeward margin) core shows a Reef Core Facies containing over 18% stromatoporoids, a Reef Debris Facies of almost 1% tabulate corals, a Skeletal Grainstone Facies of less than 1% faunal density, and a few feet of Restricted Facies with cyanobacterial mats of less than 1% density. The increase in porosity and permeability values in the Reef Debris (Facies 3B) Facies, located below the exposure surface, accounts for most of the increase in this sequence as seen in Figure 15d. Due to the inability to correlate 4th order High Frequency Sequences across the reef, no attempt was made to infer trends in reservoir characteristics at this scale.

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280

Figure 22: Facies, texture, faunal density, percentage of cement, percentage of porosity, and permeability (mD) between Sequence Boundary 3 and Sequence Boundary 4. All cores except the Halmich (crest) core show the end of reef growth at SB4 with Restricted Facies consisting of cyanobacterial mats in the Lask4 (windward), Jacob (crest to leeward), and the BTK (crest) cores. The presence of both stromatoporoids and cyanobacterial mats in the exposure surface shows the rapidity of the facies transition. The Jacob core shows a Reef Core Facies consisting mostly of stromatoporoids. It also has a Reef Debris Facies rich in tabulate corals and a Skeletal Grainstone Facies. The Jacob core has a less dense restricted facies with cyanobacterial mats indicating that it may have been deeper on the leeward foreslope during this interval. The Halmich (crest) core is transitioning from a peloidal mudstone-grainstone with mostly unidentifiable debris back into a Reef Facies before ending reef growth with Restricted Facies of cyanobacterial mats. This indicates that the Halmich (crest) core was in deeper water than the other cores at SB4. The Percy core completes its reef life cycle between SB3 and SB4 and ends at SB4 with a Restricted Facies of mudstone with anhydrite. 281

Conclusions

Major Findings

Relative Abundance

282

Framework Density

Diversity

Morphology

Faunal distribution

Cement

Cement averaged 19.25% with a high of 28.12% on the windward side and a low of 12.20% on the leeward side. The crest ranged from 21% to 25% cement.

In situ vs. debris

The reef was composed mostly of rubble or debris with the average for the six cores being 23% in situ fauna and 77% debris.

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