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' 1v $7'%4”":z%f 1/, «17:74.3 £694 .. .wzg'fi”. ;, : fizlnié' I, ‘I‘Ir f,o>":p t :l'!/. ...- ’5']? I III. ! ".9""/.'4:f:' if?“ 'I )1}. .33!" '1? Crag; .,_-4‘.f’5? .55.... ., .1 'f,‘.‘.>-’ . . ,5'.’ ’3: . ,. a n r "$.62 ';l."fi4"" 'I , r':,..’. 71-9“ . f‘?‘ llllllllllllllll Illlllllllltlllll 3 1293 00854 9853 LIBRARY Michigan State University This is to certify that the thesis entitled ECOLOGIC AND TAPHONOMIC GRADIENTS IN STORM DISTURBED BRYOZOAN COMMUNITIES OF THE KOPE FORMATION (CINCINNATIAN SERIES, UPPER ORDOVICIAN), CINCINNATI ARCH REGION presented by Salvatore Frank Rabbio has been accepted towards fulfillment of the requirements for MS Geology degree in Major professor 431M 4,;ij bate May @4988 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution MSU LIBRARIES “ RETURNING MATERIALS: Place in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. . m we "Wd Rf“ FEB $3393} ' 9 v i J ECOLOGICAL AND TAPHONOMIC GRADIENTS IN STORM DISTURBED BRYOZOAN COMMUNITIES OF THE ROPE FORMATION (CINCINNATIAN SERIES, UPPER ORDOVICIAN), CINCINNATI ARCH REGION BY Salvatore Frank Rabbio A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geological Sciences 1988 ‘13 .108’ “._.__—__-‘_ ABSTRACT ECOLOGICAL AND TAPHONOMIC GRADIENTS IN STORM DISTURBED BRYOZOAN COMMUNITIES OF THE ROPE FORMATION (CINCINNATIAN SERIES, UPPER ORDOVICIAN), CINCINNATI ARCH REGION BY Salvatore Frank Rabbio The storm-dominated fossiliferous limestones of the Kope Formation show variation in biostratinomic features. This variation permits classification of limestones in a taphofacies model (taphonomic grading). Taphonomic grading provides a useful quantitative approach to facies analysis. Grading also delineates proximality trends, defines carbonate-clastic cycles and allows event bed correlation between adjacent and widespread stratigraphic sections. Gradient analysis using bryozoan generic abundance data provides bathymetrically controlled coenocorrelation curves indicating shallow waters in the lower Kope, a gradual deepening to the middle Kope and shallowing to the Fairview Formation. These curves are consistent with trends in bryozoan generic diversity, taphonomic grade, limestone/ shale ratios, bryozoan growth form and published sea-level curves. Coenocorrelation curves allow correlation of nearby and geographically widespread Kope sections. Taphonomy affects the gradients provided by ordination techniques. Axes become less continuous when taphonomically overprinted limestones make up the data and ordinations reflect taphonomically controlled patterns such as size sorting. :I .r ’C‘Joi'nlnt ,. > ;;-=1ded n. * .m 1r.“ £94.: 9 l ‘ ’. fig, 9.5.5 : 2'23 (magia's , 4f r. 'Tfll‘i'i’lnfi ~' It‘d-i rat-3. Nab drum," and " ‘- .‘ U , .I‘:ozrr . .. Ll'airl I n . p. 4‘- s . r' u I ". ho He! II So..- To my wife Amy ACKNOWLEDGEMENTS I am grateful for the guidance and encouragement provided me by Robert Anstey through my years at Michigan .State, and especially for this project. I also thank Douglas Erwin and Duncan Sibley for their constructive suggestions regarding study methods and manuscript improvements. Conversations with Gregory Schumacher, William Harrison and Danita Brandt helped shape some of the ideas on storm sedimentation and taphonomic grading presented in this thesis. Special thanks goes to my wife Amy who was a constant source of encouragement throughout the study. Financial assistance was provided by a Sigma Xi Research Society Grant and a Chevron-Standard Oil Field Oriented Thesis Research Grant. iv TABLE OF CONTENTS LIST OF TABLES . . . . . . . . . . . . . LIST OF FIGURES . . . . . . . . . . . . INTRODUCTION . . . . . . . . . . . . . . Previous Work . . . . . . . . . . Stratigraphic Setting . . . . . . Paleogeographic Setting I O O I I Purpose . . . . . . . . . . . . . Methods . . . . . . . . . . . . . STORM AND CYCLIC DEPOSITION . . . . . . Storm Processes . . . . . . . . . Proximality Trends . . . . . . . . Characteristics of Storm Deposits Shoaling-Upward Hemicycles . . . . Megacycles . . . . . . . . . . . Carbonate Clastic Cycles . . . . . Individual Limestone Beds . . . . TAPHONOMY AND TAPHONOMIC GRADING . . . . Biostratinomic Processes . . . . . Taphonomic Grading . . . . . . . . PALEONTOLOGY . . . . . . . . . . . . . . Brachiopods . . . . . . . . . . . Crinoids . . . . . . . . . . . . . Molluscs . . . . . . . . . . . . . Arthropods . . . . . . . . . . . . Bryozoans . . . . . . . . . . . . . . . . . . . . Bryozoan Faunal Zones . . . . . . . . . . . . . . Bryozoan Paleoecology . . . . . . . . . . . . . . Bryozoan Succession . . . . . . . . . . . . . . . Bryozoan Communities . . . . . . . . . . . . . . . Faunal Relationships . . . . . . . . . . . . . . . BATHYMETRIC, TAPHONOMIC AND DIVERSITY TRENDS Kope Paleobathymetry - Previous Work . . . . . . . Diversity Trends . . . . . . . . . . . . . . . . . Taphonomic Trends . . . . . . . . . . . . . . . . GRADIENT ANALYSIS AND EFFECTS OF TAPHONOMY . . . . . . . Introduction to Gradient Analysis Techniques . . . Previous Work . . . . . . . . . . . . . . . . . . Data Editing . . . . . . . . . . . . . . . . . . . Results With All Taphonomic Grades Included . . . Results With Taphonomic Grades 1-3 Only . . . . . Results With Taphonomic Grades 3-6 Only . . . . . Discussion and Summary . . . . . . . . . . . . . . CONCLUSIONS LIST OF REFERENCES . . . . . . . . . . . . . . . . . . . APPENDIX APPENDIX APPENDIX APPENDIX APPENDIX APPENDIX A B C D E F Collecting Localities . . . . . . . . . . . Measured Section Descriptions Key to the Kope Bryozoans . . . . . . . . . Taxonomic Listing of Kope Bryozoan Species. Tabulated Point Count Data . . . . . . . . Bryozoan Generic Ranges for Meas. Sections. vi 61 63 72 74 75 77 82 83 85 93 94 94 97 101 103 122 138 156 165 167 176 177 192 197 199 216 , Ls: p—a I N LIST OF TABLES Susceptibility of different types of invertebrate fossil skeletons to various biostratinomic processes . . . . .39 Potential utility of various invertebrate skeletal types as qualitative indicators of physical environmental parameters . . . . . . . . . . . . . . . . . . . . . .40 Average abundance of bioclasts by grade . . . .‘. . . .42 Mean branch diameter and taphonomic grade . . . . . . .42 Average log base 2 Brillouin diversity index and evenness for taphonomic grade (for all five sections) .90 Aspects of bryozoans used in DCA and RA plots . . . . .104 Discontinuity (D) of RA and DCA axes . . . . . . . . .121 LIST OF FIGURES 1. Approximate stratigraphic relations of major litho- stratigraphic units in the Cincinnati region . . . . . 4 2. Part of Eastern United States, showing dominant rock types, inferred depositional environments and paleolatitude in Late Cincinnatian time. . . . . . . . 7 3. Tectonic events in the eastern United States during Ordovician time. . . . . . . . . . . . . . . . . . . . 9 4. Locations of measured sections . . . . . . . . . . . . 12 5. Stratigraphic position of the five measured sections . l4 6. Classification for Kope Formation limestones . . . . . 17 7. Simplified storm processes model illustrating the relationship between barometric, wind and wave effects.20 8. Schematic diagram illustrating storm-generated currents produced by storms acting on the modern Atlantic shelf.20 9. Generalized model for shoaling- upward sedimentary cycles in the Cincinnati Group. . . . . . . . . . . . 2 10. Facies interpretation of three Cincinnatian Group shoaling- upward sedimentary cycles . . . . . . . . . 26 11. Graphic comparison of the "average megacycle" from six different formations in the Cincinnati Group . . . . . 30 12. Idealized vertical succession of sedimentary structures and lithologies in carbonate- -c1astic cycles, Martinsburg Formation, southwestern Virginia . . . . . . . . . . . 33 13. Carbonate-Clastic sedimentary cycle variants. . . . . 35 14. Integrated depositional model for Kope sedimentation. 36 15. Stages of benthic community succession in Cincinnatian seas . . . . . . . . . . . . . . . . . . . . . . . . . 44 16. Example of taphonomic grade 1 bed . . . . . . . . . . 45 17. Example of taphonomic grade 2 bed . . . . . . . . . . 47 18. Example of taphonomic grade 3 bed . . . . . . . . . . 49 19. Example of taphonomic grade 4 bed . . . . . . . . . . 50 viii 20. Example of taphonomic grade 5 bed . . . . . . . . . . 52 21. Example of taphonomic grade 6 bed . . . . . .'. . . . 53 22. Proportion of taphonomic grades . . . . . . . . . . . 55 23. Summary of energy relationships between taphonomic grades . . . . . . . . . . . . . . . . . . . . . . . 55 24. Stratigraphic plot of taphonomic grade illustrating how grade defines megacycles and suggested megacycle correlations . . . . . . . . . . . . . . . . . . . . . 58 25. Proportion of bryozoan genera . . . . . . . . . . . . 62 26. Stratigraphic ranges of Kope trepostome species in the study area of Anstey and Perry (1973). . . . . . . . . 64 27. Anstey and Perry (1973) collecting localities . . . . 65 28. Bryozoan generic ranges in ascending sequence in the southeastern sections composite (sections 1, 2, and 5).67 29. Bryozoan generic ranges in ascending sequence in the northwestern sections composite (sections 3 and 4) . . 68 30. Cumulative abundance of the seven dominant bryozoan genera for the section 1&5 composite showing the three bryozoan communities named from the three most dominant genera in each zone. . . . . . . . . . . . . . . . . . 76 31. Cumulative abundance of bryozoans, brachiopods, crinoids, and bivalves for the section 1&5 composite showing four communities named from the two most dominant groups in each zone. . . . . . . . . . . . . . . . . . . . . . . 78 32. Component line chart of rescaled crinoid, brachiopod, bryozoan, micrite, spar and other abundance for the section 1 & 5 composite. . . . . . . . . . . . . . . . 79 33. Component line chart of rescaled trilobite, bivalve, ostracode, crinoid, brachiopod, bryozoan and other abundance for the section 1 & 5 composite. . . . . . . 80 34. Smoothed second-order curves plotted against the smoothed first polar axis . . . . . . . . . . . . . . 86 35. Non-cumulative line chart of smoothed Brillouin diversity index and taphonomic grade for the section 1 & 5 composite. . . . . . . . . . . . . . . . . . . . . . . 88 36. Histogram of branch diameter of ramose bryozoans for all stratigraphic sections (N=2649). . . . . . . . . . 106 ix 37. R-mode growth habit plot of DCA axis 1 vs. 2 with all grades included. . . . . . . . . . . . . . . . . . . . 106 38. R-mode growth habit plot of DCA axis 1 vs. 2 with all grades included and rare genera omitted. . . . . . . . 107 39. R-mode growth habit plot of DCA axis 1 vs. 2 with all grades included and rare genera downweighted . . . . . 107 40. R-mode size plot of DCA axis 1 vs. 2 with all grades included and rare genera omitted . . . . . . . . . . . 109 41. R-mode size plot of RA axis 1 vs. 4 with all grades included and rare genera omitted . . . . . . . . . . . 109 42. R-mode subordinal plot of DCA axes 2 vs. 3 with all taphonomic grades included and rare genera omitted . . 111 43. R-mode subordinal plot of RA axes 2 vs. 4 with all grades and rare genera omitted . . . . . . . . . . . . 111 44. Q-mode stratigraphic plot of smoothed DCA axis 1 for all five measured sections . . . . . . . . . . . . . . 114 45. Q-mode (second-order) stratigraphic plot of DCA axis 1 with all grades included . . . . . . . . . . . . . . . 117 46. Q-mode stratigraphic plot (second-order) of DCA axis 1 with all grades included . . . . . . . . . . . . . . . 119 47. R-mode growth habit plot of DCA axes 1 vs. 2 with grade 1-3 beds only. . . . . . . . . . . . . . . . . . . . . 123 48. R-mode growth habit plot of DCA axes 1 vs. 2 with grade 1-3 beds only and rare genera omitted. . . . . . . . . 123 49. R-mode growth habit plot of RA axes 2 vs. 4 with grade 1-3 beds only and rare genera omitted. . . . . . . . . 50. R-mode size plot of DCA axes 1 vs. 2 with grade 1-3 beds only and rare genera omitted. . . . . . . . . . . 124 51. R-mode subordinal plot of DCA axes 2 vs. 3 with grade 1-3 beds only and rare genera omitted. . . . . . . . . 52. Q-mode stratigraphic plot of DCA axis 1 (smoothed) grade 1-3 beds only and rare genera downweighted . . . 131 53. Q-mode stratigraphic plot of DCA axis 1 (second order) with grade 1—3 beds only and rare genera downweighted. 134 54. Q-mode stratigraphic plot of RA axis 3 (second order) with grade 1-3 beds only . . . . . . . . . . . . . . . 137 55. R-mode growth habit plot of DCA axes 1 vs. 2 with grade 3-6 beds only. . . . . . . . . . . . . . . . . . . . . 139 56. R-mode growth habit plot of DCA axes 1 vs. 2 with grade 3-6 beds only and rare genera downweighted . . . . . . 139 57. R-mode growth habit plot of DCA axes 1 vs. 2 with grade 3-6 beds only and rare genera omitted. . . . . . . . . 140 58. R-mode size plot of DCA axes 1 vs. 2 with grade 3-6 beds only. . . . . . . . . . . . . . . . . . . . . . . 140 59. R-mode size plot of DCA axes 1 vs. 2 with grade 3-6 beds only and rare genera downweighted . . . . . . . . 142 60. R-mode size plot of DCA axes 1 vs. 2 with grade 3-6 beds only with rare genera omitted . . . . . . . . . . 142 61. R-mode subordinal plot of DCA axes 2 vs. 3 with grade 3-6 beds only. . . . . . . . . . . . . . . . . . . . . 143 62. R-mode subordinal plot of DCA axes 1 Vs. 2 with grade 3-6 beds only and rare genera downweighted . . . . . . 143 63. R-mode subordinal plot of DCA axes 1 vs. 2 with grade 3-6 beds only and rare genera omitted. . . . . . . . . 144 64. Q-mode stratigraphic plot of DCA axis 1 (smoothed) with grade 3-6 beds only and rare genera omitted. . . . . . 149 65. Q-mode stratigraphic plot of DCA axis 1 (second-order) with grade 3-6 beds only and rare genera omitted . . . 152 66. Q-mode stratigraphic plot of DCA axis 3 (second-order) with grade 3-6 beds only and rare genera downweighted. 154 67. Stratigraphic plots of ordination scores from Anstey et al. (1987a) and this study as well as Phragmodus undatus sea level curve of Sweet (1979). . . . . . . . . . . . 159 68. Sea-level curve for the Kope Formation in the study area . . . . . . . . . . . . . . . . . . . . . . . . . 161 xi INTRODUCTION Previous Work The fossiliferous limestones and shales of the Upper Ordovician Cincinnatian Series have been the subject of geologic research for nearly 150 years (see Weiss and Norman, 1960 for an extensive review). The earliest workers, before the advent of modern sedimentology and paleoecology, focused their studies on the abundant and well—preserved macrofossils that could be found in exposures. Thus, most of the research generated before the turn of the century was taxonomic and biostratigraphic in nature. From 1902 to 1960, workers concentrated on trying to define biozones in an attempt to subdivide the Cincinnatian Series into lithic and biostratigraphic units. Over the years those units became more finely subdivided, for example, the classification of Caster, Dalve and Pope (1961). A renaissance in the study of the Cincinnatian Series occurred from 1960 to the mid-1970’s with the advent of improved methods in carbonate petrography (e.g. Folk, 1959 and 1962; Dunham, 1962) and the appearance of the Code of Stratigraphic Nomenclature in 1961 (Tobin, 1982). These factors provided the impetus for research in two major areas: (1) the petrography of Cincinnatian limestones (e.g. Weiss and Norman, 1960b; Wetzel, 1968; Farber, 1968; Martin, 1975), and (2) lithostratigraphic reclassification of strata (e.g. Weiss and Sweet, 1964; Brown and Lineback, 1966; Peck, 1966; Ford, 1967). In the mid-1970’s, the emphasis shifted to the field of paleoecology. Workers studied paleocommunity structure and community succession (e.g. Lorenz, 1973; MacDaniel, 1976; Oldroyd, 1978; Harris and Martin, 1979), the autecology of selected Cincinnatian faunas (e.g. Richards, 1972; Anstey and Perry, 1973; Alexander, 1975; Frey, 1980), and biostratinomy (e.g. Brandt, 1980; Krumpolz, 1980; Meyer et a1., 1981). Recently, the concepts and models of storm sedimentation have been applied to Upper Ordovician sediments (e.g. Anstey and Fowler, 1969; Mahan, 1980; Mahan and Harrison, 1980; Meyer et a1., 1981; Tobin, 1982; Harrison, 1984; Schumacher, 1984, 1985 and 1986; Tobin and Pryor, 1985). The seeds for these "modern" ideas on storm sedimentation in the Cincinnatian were sown long ago by Perry (1889), Cumings (1908), and Bucher (1917, 1919). The storm generated facies and dynamic stratigraphy of the Kope Formation are discussed in detail below. Stratigraphic Setting In 1964, Weiss and Sweet introduced the Kope Formation to replace "Eden Shale" for the mudstone-rich rocks exposed in the Maysville, Kentucky and Kope Hollow, Ohio areas. The Kope Formation was named to avoid confusion with a chronostratigraphic unit, the Edenian Stage. Ford (1967, p. 924-925) extended the Kope Formation to the former Eden Formation in Hamilton County, Ohio. The Kope Formation generally spans the entire Edenian Stage except where it encroaches into the Maysvillian Stage at locations in southeastern Indiana and eastern Kentucky (Sweet and Bergstrom, 1971; Figure 1). The Kope ranges in thickness from around 200 feet (60 m) in southeastern Indiana (Brown and Lineback, 1966) to 270 feet (80 m) near Maysville, Kentucky (Peck, 1966). The Kope consists of 60 to 80 percent mudstone (commonly termed "shale," though not fissile) interbedded with 20 to 40 percent limestone and, in places, minor siltstone (Weir et a1., 1984). The mudstones are medium gray to greenish gray, weathering to yellowish gray. They are calcitic, silty and have a clay mineralogy composed dominantly of illite (including some mixed illite-montmorillonite), chlorite, and vermiculite (Bassarab and Huff, 1969). Fossils are generally sparse in the shale and siltstone but when they do occur, they are generally whole to slightly broken (due to compaction). The limestones of the Kope Formation vary in thickness from thin discontinuous lenses of between 1 and 8 cm thick to resistant sparry (and often megarippled) continuous beds of up to 35 cm thick. Ripple marks occur on the upper surface of many limestone beds. Thin packstone units have amplitudes generally less than 2 cm and wavelengths of less than 25 cm. Thick ledge forming sparry limestones commonly have amplitudes of 8 to 15 cm and wavelengths of 0.5 m to more than 1.0 m. Some limestones also exhibit crossbedding. NORTHERN AND EASTERN SE MES SOUMASTIIN SOU'NWESTEHN INDIANA OHIO CENTRAL RENYUCKY mum-enema Ashlee! Lalo formation h- fennel-on C-nemnlhm Meyevmmn Cello-rev Creel Lune-lone 2 S 9 > o a K o Ganuo Sallelon. formal-on Clay! ferry Formalion Huunl tongue Shannen.” CBImn'a-nmn vaon. Lumnlon. Approximate stratigraphic relation: of major litho— stratigraphic units in the Cincinnati region. Modified ' M from Sweet (1979, fig. 3, p. 613; in Vier (1984, fig. 50, p.80)). Figure 1 Hoffman (1966) has studied these structures in southern Ohio and suggests a dominant paleocurrent direction to the west northwest (down paleoslope). The Kope Formation grades to the south into the Clays Ferry Formation which is lithologically similar to the Kope except that the percentage of shale is less and the shale units thinner. Stratigraphically below the Kope Formation in the study area is the Point Pleasant Tongue of the Clays Ferry Formation most of which is late Shermanian in age; locally some upper beds are earliest Edenian. The Point Pleasant Tongue is characterized by planar to lenticular bedded limestones as is the Kope but has a higher percentage of limestones (about 60 percent) and less shale than the Kope. Tobin (1982, p. 160) suggests that the basal contact of the Kope Formation with the underlying Point Pleasant Tongue be defined as the base of the lowermost terrigenous stratum (shale unit) greater than two feet thick. In the study area, the upper Kope grades lithologically into the Fairview Formation. The Fairview is characterized by evenly bedded limestone (about 50-60 percent) interbedded with shale and siltstone (40-50 percent). The Kope- Fairview contact can be determined by the change in the limestone to shale ratio (the Kope having more shale and less limestone than the Fairview) and is easily recognized in the field. In northern Kentucky, the base of the Fairview is a prominent ledge, l to 2 m thick, of brachiopod limestone containing abundant valves of Strophomena. In northern north-central Kentucky, a similar ledge-forming set of limestone beds containing abundant small dalmanellid brachiopods marks the contact (Weir et a1., 1984). Ford (1967, p. 929) originally defined the top of the Kope Formation as the base of a limestone bed overlying the uppermost terrigenous stratum (shale unit) greater than two feet thick. The Fairview grades by a marked increase in shale content northwestward into the Dillsboro and, possibly also into the Kope Formation in Indiana, and southward into the Calloway Creek Limestone with an increase in limestone content and fossil content (Weir et a1., 1984; Figure l). Paleogeographic Setting The depositional environments and associated rock types of the midcontinent during the Late Cincinnatian extend from deltaic plains to deep shelf (Figure 2). Projected magnetic- pole positions, fossils, and rock lithologies suggest that the Cincinnati region was positioned at 220 south latitude during the Late Ordovician (Wier et a1., 1984). During the Early Ordovician, the eastern midcontinent was a broad, structurally passive continental shelf (King, 1977). Carbonate deposition was favored because of the subtropical environment and lack of erosional highlands to provide terrigenous Clastic sediment which would have inhibited carbonate precipitation. As a result, an extensive lcarbonate platform 3000 meters thick accumulated through the Late Cambrian and Early Ordovician (Figure 3a). Land 0 750 SW 750 KILOHETEIS : I I l _.l I o no 500 was EXPLANATION Sandstone. slltstone. Dolomite. shale. and ' and shale limestone Shale and siltstone g Umestone and shale Shale and limestone Figure 2: Part of Eastern United States, showing dominant rock types, inferred depositional environments and paleo- latitude in Late Cincinnatian time from Vier (1984, fig. 69, p. 109). A major regression in Early Middle Ordovician time marks the onset of subduction of the proto-Atlantic oceanic plate beneath the North American continental plate (Bird and Dewey, 1970). As the Taconic Highlands emerged and developed along the continental rise and slope, the carbonate shelf subsided to form the Appalachian Basin (Figure 3b). Subsequent weathering and erosion of the Taconic Highlands provided the source of Clastic sediments which were deposited in the subsiding Appalachian Basin. These clastic wedges and sheets became the interbedded layers of siltstone and shale of the Martinsburg and Normanskill Formations in the central and northern Appalachians, and the Bald Eagle, Oswego and Juniata deltaic and floodplain sands of the eastern Appalachians. Flooding of the craton in the Late Ordovician resulted in an epeiric sea which covered the midcontinent until the Late Ordovician-Early Silurian regression. The expanding Taconic landmass to the east continued to shed terrigenous sediment into the Appalachian Basin. This sediment nearly filled the Appalachian Basin with basinward prograding Clastic wedges by the close of the Ordovician resulting in a gradual shallowing of the Late Ordovician sea (Bird and Dewey, 1970; Figure 3c). The interbedded shales and limestones of the Cincinnatian Series were deposited in this shoaling environment. CONTINENTAL WM CONTINENTAL A. EARL Y ORDOVICIAN . RISING APPBAALQSH'AN TACONIC OROGEN \ 8. MIDDLE ORDO VICIAN TACONIC OROGEN 4&4 V I ‘~‘\ ’9” ~‘ . ~ ~ ——’ C. LA TE ORDO VICIAN Figure 3: Tectonic events in the eastern United States during Ordovician time (modified from Bird and Dewey, 1970; in Mahan (1980, fig. 4, p. 7). 10 Purpose There have been numerous studies over the past 10 years by paleoecologists utilizing the techniques of gradient analysis to aid in environmental interpretation of fossil assemblages, ecostratigraphic correlation, estimation of paleobathymetry, and tectonic relationships both locally within formations and regionally between formations (Anstey, Rabbio and Tuckey, 1986, 1987a, 1987b; Cisne and Rabe, 1978; Cisne et a1., 1982; Rabe and Cisne, 1980; Springer and Bambach, 1985). Although many of these studies focused on rock units which showed evidence of taphonomic effects such as post—mortem transport and current sorting, none of them attempted to test the effects taphonomy had on the gradients described. By use of a taphofacies model (taphonomic grading, described below), one can estimate proximity to storms and roughly quantify taphonomic effects. This model can then be used to test the effects of taphonomy on gradients by analyzing limestone beds of selected grades and comparing the resulting gradients. As mentioned above, gradient analysis is an effective method for determining axes of variation in fossil assemblages. Axes reveal changes in species distributions due to changes in physical or biological parameters along spatial gradients. Physical parameters may include substrate variation, water depth, salinity, agitation, turbidity and temperature among others. Biological parameters include potentially identifiable biotic interactions, such as: 11 spatial Competition on hard substrates, trophic partitioning and feeding interactions, and possibly taphonomic feedback. This study will attempt to describe the parameters affecting bryozoan generic distribution in the Kope Formation limestones, and, in turn, what information these controlling parameters impart about the bryozoans and limestones themselves. M_e_tho_ds Five stratigraphic sections from the study area around Cincinnati, Ohio (Figure 4) were measured and described during the summer and fall of 1986. Appendicies A and B). The five sections provide as much overlapping stratigraphic coverage as is possible in the limited Kope exposures around Cincinnati (Figure 5). The section transect was designed to approximately follow the northwest to southeast paleoslope direction to maximize any changes that occur with water depth, and therefore enhance the resulting gradients derived from gradient analysis. For each section, a datum was established by marking the Stratigraphically lowest limestone bed which was laterally continuous and easily traceable. The entire section was then measured with steel tape. Most of the exposure was cut into terraces or benches; each part of the section between terraces was measured separately, and then _totalled to get an overall thickness. Each shale unit and limestone unit was then measured with steel tape and 12 ~//,‘\ 275 _ \ Inmana 75 7, 28 N 74 . 131 3 «" . 9‘ a _\.6“ O“ ‘0‘ ‘v" Cincinnati ‘ 5‘0 / J '/ 275 3 Kentucky 5 u. 2 A l Florence I ' ‘0 "H“, =_———_ 75 ,_. =2 I; I0 In 5 O P 71 Figure 4: Locations of measured sections (1 - Brent North, 2- 3 - Mt. Airy, 4 - Hiamitown, 5 - Brent Sanfordtown, South). 13 described, beginning with the datum horizon and working upwards. Color, bedding style, sedimentary structures, fossil content and depositional features were recorded for each bed. In addition, the lithology of each bed was identified according to three different classifications: (1) a modified Dunham's (1962) classification by texture (Figure 6, see Mahan, 1980), (2) Folk's (1959) classification by rock type and fossil content, and (3) Weiss and Norman’s (1960a) classification of Cincinnatian limestones based on degree of fragmentation and orientation of fossils, including characteristics of the insoluble fractions. Each in situ limestone bed that was indurated enough to collect was pried from the surrounding rock, trimmed, and labelled with a sample number and a north arrow. No float material was collected. North arrows were placed on the top surface of the bed. A total of 172 beds were collected from the five sections. The beds were then slabbed perpendicular to bedding. Those beds judged to have abundant bryozoans were cut in two perpendicular directions to give a more accurate measurement of fragment volume and to account for any ramose fragment alignment by currents. The slabs were polished, in sequence, with 300, 600 and 1000 mesh grit. Slabs with abundant bryozoans were polished with fine alumina (0.3 microns) to bring out more detail in the etch making identification of bryozoan fragments easier. The beds were then etched in 0.5% formic acid for 6-7 .meo«uoea censuses o>uu ecu we couuqaon cage-um—neuuw "m ousmam causes acnneon ucqom Exo.v End U. 1 an soa>uumh. .5332: a»: .ux 5.3335» 5:8 95$ .35: 938 v coauuom n cognac» a ceauuou n eouuuon H eouuooa 15 minutes. Acetate peels were made using 0.05mm acetate and mounted between 1/8 inch glass plates cut to size. Edges were sealed with clear packaging tape. Approximately 325 acetate peels were made. Following the procedure outlined by Underwood (1970, p. 18), a pilot study was undertaken to determine the best sample and grid size for point counting Kope limestones. Underwood recommends that a point count grid should, on average, have only one node falling within each object being counted to avoid bias. To test what size grid would best approximate this, five grid sizes (2 mm, 3 mm, 5 mm, 7mm, 1 cm) were drawn on clear acetate and placed on four representative slides from different parts of the Kope. Number of grid node intersections within bryozoan fragments and total bryozoan fragments were counted to give an average number of intersections per fragment. The 3 mm grid size was found to be the best (0.93 grid intersections per bryozoan fragment). To determine the number of point counts needed until a stable fragment volume (Pp) was reached, volumes were plotted at 10 count intervals for between 250 and 300 total counts for all the representative slides using the 3 mm grid. Only the dominant bryozoan genus in each slide was counted. Volume estimates generally stabilized between 180 and 190 counts. Therefore 200 point counts were made on each slide with a 3 mm grid oriented at an angle to bedding (to damp any bias due to orientation of ramose forms). A total 'of 225 slides were point counted in this way. 16 As mentioned above, beds that had greater than 20% bryozoans were slabbed in two perpendicular directions. Peels were made on both cuts and both were point counted and averaged together to get a more accurate volumetric estimate of the bryozoan fraction. Bryozoans were identified to the genus level by the use of keys (Appendix C) and published thin section photo micrographs (especially Anstey and Perry, 1973). Because of random orientation of sections and poor preservation, some fragments were impossible to identify and were put in an unidentifiable category. Every ramose bryozoan cut in a transverse or nearly transverse orientation was measured to give a branch diameter. In addition to bryozoans, brachiopods, crinoids, bivalves, trilobites, gastropods, and ostracodes were also counted. These other allochems were lumped into broad phylum or class level groups, and no attempt was made to identify them at the generic level. Also counted were micrite, spar and dolomite. Each bed was identified within the modified Dunham (1962) classification (Figure 6) and taphonomically graded (discussed below) using both the slides and hand samples (Appendix E). The data were entered into dBASE III Plus (Ashton Tate) and Statgraphics (Statistical Graphics Corporation) on a personal computer. Most of the plots in the gradient "analysis section of this thesis were generated using Statgraphics. The gradient analysis runs were also done on a ‘personal computer using the DECORANA (DEtrended 17 TURN. NAME TEXTIIAL DESCRIPTION ew- - tw'oflw. counts: summit 1m mu- 5 new" no. USUALLY III M mucus. min-5mm). COI'IAINS caesium»: S uncut nun. nos 1: suoumum to sen sv 5 1:2 uno. POORLV-‘IASKD SIAI IS!“ GMII-sWPOIYED. coumus PAIYtALu-Iluaowcn slum mm 5 return sun. sun I; susoamun on ncxstou: aroma. to nun. nmrvtn arm rxcuns 2:1 nno. “All-SWPOIYED In a mo "cutout Mtlll. coumus LESS mm 5 recent sun. HID-SW'OITID. CNTAIIS HACK!!!“ ms my: ID nncur cums. WSWMIED. CNTAINS N087“! - came- num 10 nicest cum Figure 6 - Classification for Kope Formation limestones. Modified from Dunham, 1962 (in Meyer et a1., 1981, fig.6,p.40). 18 CORespondence ANAlysis) program of Hill (1979). STORM AND CYCLIC SEDIMENTATION The study area around Cincinnati Ohio was located at approximately 220 south latitude during the Late Ordovician (Wier et a1., 1984). Marsaglia and Klein (1983) inferred, by analogy with modern storm tracts, that this area occasionally experienced hurricane force storms (approximately one every 3000 years) and winter storms (less severe but more common - once or twice a year). The physical aspects of such storms and their effects on sedimentation are discussed below. Storm Processes The basic physical processes that occur during storms have been summarized by Allen (1982, 1984) in a simplified model. Allen’s model assumes simple laminar flow of a storm approaching the coastline at a perpendicular angle and with constant speed and direction. The effects of tides and the Coriolis-force are ignored in this model but will be discussed below. Three basic categories of processes and effects can be distinguished during storm sedimentation (Figure 7): barometric effect, wind effects, and wave effects. 1) Barometric effect - Cyclonic depressions are accompanied ,by a horizontal gradient of atmospheric pressure, thus 19 raising the water level at the shore (coastal set-up). Typical cyclones raise the water level at the coast about 0.5 meter. 2) Wind effects - Onshore blowing winds create a drag which not only contributes to coastal water set-up, but also results in a nearshore wind-drift current that also acts in the onshore direction. The tilt of the water surface due to the combination of barometric and wind effects is compensated by a near-bottom gradient flow in an offshore direction. Thus there is an onshore near-surface flow and a compensating offshore bottom current flow during a typical storm. As a result, predominantly onshore directed sediment transport would be expected in shallow, nearshore water (due to wind—drift currents). In deeper waters, offshore directed sediment transport prevails. 3) Wave effects - Waves cause near-bed oscillatory flows that are responsible for stirring up and mobilizing bottom sediments. Oscillatory wave-driven currents interact with unidirectional wind-driven currents to create bottom shear stresses greater than either current independently. The combined effect of both currents is the development of a very efficient system of erosion, transportation and redeposition of sediment. Beyond this simple model, a more complex model has been derived from studies examining the fluid and sediment dynamics of the present Atlantic continental shelf (Swift et ‘31., 1983). Storms, upon approaching the coastline or moving 20 BAROMETRIC WIND set-up & etiect effect Figure 7 - Simplified storm processes model illustrating the relationship between barometric, wind and wave effects. Simple case of onshore blowing storm, interactions with tides and the Coriolis force not considered (modified from Aigner, 1985, fig. 1). Figure 8 - Schematic diagram illustrating storm-generated currents produced by storms acting on the modern Atlantic shelf.(from Swift et a1., 1983, fig. 6). 21 out to sea, develop a pressure field from offshore to onshore (discussed above). The pressure field produces winds which move roughly parallel to the shore resulting in unidirectional currents (Figure 8). These currents are deflected landward by Ekman transport and the Coriolis-force and cause coastal setup. Over time, the entire shelf water column begins to flow alongshore (core flow, Figure 8) and intensifies. Bottom frictional drag leads to seaward veering of the water base (bottom flow, Figure 7, equivalent to gradient current discussed above). Coastal waters downwell to replace bottom waters moving offshore. Finally, the water movement onshore equalizes with water movement offshore. The net result of both models is the same: onshore directed sediment transport in shallow nearshore waters and offshore directed bottom gradient currents in deeper waters. Proximality Trends The intensity of storm events and the resulting effects on the seafloor vary with water depth. The systematic changes in the nature of storm stratification from nearshore (proximal) to offshore (distal) are termed "proximality trends" (Aigner, 1982; 1985; Aigner et a1., 1982). Storm effects (erosion and suspension of sediment) decrease with increasing water depth. Aigner et a1. (1982) found that storm layer frequency per meter core in the German North Sea reaches an optimum in a zone between the nearshore and offshore. In water 22 shallower (more proximal) than this "frequency optimum" zone, more storms affect the sea bottom; yet, at the same time, each storm tends to rework and erase previously deposited layers. Therefore, preservation potential is low. The result is thick storm layers and low frequency. In water deeper (more distal) than the optimum, the preservation potential of storm events is much better and the record more complete (disregarding the effects of bioturbation). However, as water depth increases offshore, fewer and fewer storms leave their record on the sea bottom. The probability of sediment influx from land also decreases in an offshore direction resulting in thin and more infrequent storm beds. Characteristics of Storm Deposits Storm beds can be recognized by their sedimentary features. Generally, no single sedimentary feature (except, perhaps, hummocky cross-stratification), is diagnostic of a storm bed; for most sedimentary structures, other causes could also be responsible. In combination, however, the features listed below offer strong support for storm origin. Kreisa (1981; Table 1, p. 843) lists several storm generated sedimentary features reported in the literature. Sedimentary features include: hummocky cross-stratification, interbedded coarse (storm) and fine (fair weather) beds, sharp/scoured base - gradational/ burrowed top, pot and gutter casts, lag suspension couplets, thickening and thinning and lenticular beds, reworked autochthonous fauna, infiltration textures 23 (e.g. shelter void porosity), escape burrows, wave-generated undulatory lamination, vertical sequence of sedimentary structures from plane-lamination to wave generated lamination, laminated beds with upward thinning laminae, increase in matrix and weak grading. In this chapter, Kope stratigraphy will be considered as a hierarchy of cycles, starting with regional shoaling upward trends containing smaller megacycles, which in turn contain finer scale carbonate-Clastic cycles. Also considered are the storm generated characteristics of individual beds. Shoaling-Upward Cycles Shoaling—upward (regressive) cycles range in thickness from 40 to 200 meters and are defined by the recurrence of lithologic sequences (formations or members) within the Cincinnati Series. These cycles are the product of either transgressive-regressive sea-level fluctuations or basin filling resulting from the sedimentation rate exceeding the rate of sediment compaction and/or basin subsidence. Tobin (1982, p. 147) defined four facies (A, B, C and D) which constitute an idealized shoaling-upward cycle for the Cincinnati Series (Figure 9). Facies A is Clastic rich, thick, and planar bedded. Facies B is mixed carbonates and clastics, intermediate in thickness, and planar bedded. 'Facies C is carbonate rich (limestone), thin, and wavy to nodular bedded. Facies D is carbonate rich (dolomite), 24 .:.v .m: .NmmH .cunoa Eouwv ozone Humccaucfio ecu ca moauxo humucoedoom pumzmsumcfiamocm now Hooos penqamuocoo I .ivv. 2.3030 2s .Isn. £50.; .1 Sou-w . m ousoqm :0: :03 III N «I! .3 II .1: . .26. NH «1.. 4.5:; 2...... .33... 3.2.1.. .5: I. . c. : .- 3 . .. 2 .II n . E 3.: 2:3... 3.1. I: 3:. i... . Is . 85.. III 3 =8 31— .93 a]. I... 381 39.28. heat 4....— HH. V oas- . sea: vs- .II.- III a! .8; III 4 3.2 .21... I I | u 3!. 32: I I I a :5)... .a‘. I I: :1. .158: 3.8.2.... 3:. . I an . I 2 I l a. :3. club» Ute-not oi... I g 4fi~3 1 .‘o I I. C n :8 ‘ dealt». a I lee: 1a! _ _ _ _ I .=. _ - Ia— . 3 .lalI seao noes-a} . is}... l I I . . 1.. :8: .1: I." I I . u 2.3.... . a 5...... 8.3.3:... .851. 6:... .l. s 2 .s . I .38....» .83. s «3.... s... 5.3:... 3:. .8... 3:. . s. c . u 6 f. . £3. .1... £81 .I. 1.3... I. .2... a «.13.: lit.» .1! .33. It.) .I .33 all) I!!! seen . 8.!- Slls s dos. ale. gall cl! — .I. eel V ‘90:: at} JIZi _ {an In. .Ii 05:, U n~ . I v m :16 a toes-l I .i u I! all: .33..”— S. Isa. 41— n .00: a. 1!... .8 2 1! 2.... .1 {.01 is 2.1.3.. :1:- > .25.... . 0 m I. :3... 12.-.01. :30! ii: «:13: 2»: 33.0.... _ . Eud‘un! at: on: 3““: nun-u"; nun-“Ha 30.3.... I 3.2:. C u-uupa mane. ugx 25 intermediate in thickness to thin, and massive to nodular bedded. Shoaling-upward cycles were discussed by Anstey and Fowler (1969, p. 678) and later refined by Hay (1981) and Tobin (1982). Three shoaling-upward cycles can be recognized within the Cincinnatian (Figure 10). The first cycle ranges from the Kope Formation to the Bellevue Member of the Grant Lake Limestone. The second cycle ranges from the Corryville Member of the Grant Lake Limestone to the Waynesville— Liberty formational contact, and the third cycle from the Waynesville-Liberty contact to the Ordovician-Silurian unconformity. Only the Kope to Bellevue cycle will be discussed in detail here. The Kope to Bellevue sequence represents deposition a gently sloping marine ramp in the offshore to shoreface position (Tobin, 1982). The Kope represents deposition in the offshore zone defined as that part of the coastal sea floor that is almost always below wave base (Reineck and Singh, 1975). It ranges from low wave base (8 to 30m) to the outer edge of the continental shelf. Sediments in the offshore zone are disturbed only by large storms or hurricanes. This zone represents the distal facies of Aigner (1985). Mud-rich sediments predominate with some grainstones forming during high-energy storm events. Preservation of storm beds is excellent although there are fewer of them ‘(compared to the transition and shoreface zones). Consequently, there are more in situ and lag type deposits. 26 Wayneevllle to Oelude Sequence Corryvllle to Oveqenle Sequence I I C ‘ I I I l I I I O C ' .U'IIOII Kope to Ieflevue Sequence 1932, (from Tobin, - Facies interpretation of three Cincinnati Group shoaling—upward sedimentary cycles Figure 10 75). fig. 27 The overlying Fairview Formation probably represents deposition in the slightly shallower waters of the offshore to transition zone. The transition zone is defined as that part of the coastal sea floor that lies between average high wave base (i.e., fair weather wave base - 2 to 20m in depth) and average low wave base (i.e., wave base during mild storms - 8 to 30m in depth). Sediments in this zone accumulate mostly under low-energy conditions, but are frequently subjected to higher energy events (Tobin, 1982). Rock types are mostly packstones with some grainstones (more than in the Kope, Figure 9). There is a decrease in shale content and siltstone content and increase in grainstone content and degree of abrasion of bioclasts compared to the Kope. The Fairview lies in the "optimum" zone for storm preservation, being shallow enough to experience frequent storm effects but deep enough to prevent amalgamation of storm beds. Sediments in the overlying Bellevue Limestone were probably deposited in the shallowest setting (nearshore) of the three formations (Tobin, 1982). The shoreface zone is almost always above average wave base. As a result, shoreface sediments are constantly being moved around by wave action and are severely affected by storms which lower wave base well below the sediment-water interface. Limestones are mostly grainstones (65%) with very little ‘shale (18%). Preservation of storm-generated sedimentary features such as ripples and graded bedding is very poor due 28 to amalgamation and cannabilism of beds during storm events. Fossils are generally robust forms capable of withstanding a high degree of water turbulence. This zone corresponds to the proximal zone of Aigner (1985). Thus the Bellevue to Kope sequence represents a proximal-distal (onshore to offshore) trend with the Kope Formation occupying the distal portion. However, relatively more proximal and more distal types of beds occur within the Kope. Since the Kope is a distal type deposit, the term "proximal" will be used to refer to higher energy beds (grainstones and poorly washed grainstones, taphonomic grades 4-6) and "distal" to lower energy beds (wackestones, packstones and lags of taphonomic grade 1-3). Megacycles Megacycles are fining—upward repetitive sequences that occur throughout the Cincinnatian Series. The idealized megacycle is a two-part sequence with a carbonate hemicycle (lower grainstone and packstone units) and a shale hemicycle (Tobin, 1982; Figure 11). In the Kope Formation, megacycles are thick with resistant, generally sparry "proximal" type limestone beds at the base and thin "distal" type packstones and interbedded shales in the shale hemicycle. The carbonate and shale hemicycles are almost always present in the Kope Formation, but the character of the beds in the cycle varies. These variations include thickness, lithology and 29 number of basal beds in the carbonate hemicycle, and lithology and number of beds in the shale hemicycle (these beds are almost always thinner than the basal beds). The order of rock types in the shale hemicycle shown in Figure 11 has no particular meaning; siltstones as well as packstones may occur anywhere in the cycle or not at all (although there is usually at least one packstone present). Kope megacycles are most likely the result of alternating storm and non-storm events at any given geographic location (Tobin and Pryor, 1981). Thus a megacycle begins when a storm passes over an area depositing a proximal (high taphonomic grade) bed. After the storm subsides, subsequent more distal events will result in deposition of the shale beds and distal packstones (low grade beds) of the shale hemicycle. The megacycle ends and the next cycle begins when another storm passes over the area, resulting in deposition of another proximal (high grade) thick limestone. Any cyclicity in the length of time that is involved in megacycle formation is tied in with the cyclicity of storms passing near a particular point in space. If storm tracts are randomly located, then there is no true time-stratigraphic cyclicity between megacycles. Thus, the cyclicity involved refers to lithologic sequence and probably not time. Transgressive-regressive mechanisms for megacycle formation cannot be ruled out, however, especially in light of the second—order bathymetric dependent curves discussed AVERAGE .IALI IIIICVCLI 'J CAIIOIAVI nluochLl _vn Waynonfluo .uALl ulnuchtl CAIIOIATI ”(MICVCLI Corryville ‘IAt. NIUICVCLI CAIIOIAYI IIIUCVCLI Koo. 30 MEGACYCLES Illkl IIIICVCLI CAIIOIAVI IIIOCVCLC IIALI «(InCVCLI CAIIOCAYI "(HICVCLI Sunuot CHILI g'no'v IIIICVCLI ' CAIOOIA'I .3”. oumcvcu Fairview Figure 11 - Graphic comparison of the "average megacycle" from six different formations in the Cincinnati Group (from Tobin, 1982, £19.43). 31 below (Figure 53). Further work is required on the causal mechanisms of Cincinnatian megacycle formation. Carbonate Clastic Cycles The most abundant and obvious cycle in the Cincinnati Series is the alternation between carbonate and elastic beds or clastic and elastic beds (siltstone and shale). The origin of Cincinnati Series carbonate-Clastic cycles has been discussed in the literature for over 150 years (reviewed by Schumacher 1984 ). Proximal Kope storm layers are thicker than distal beds, have erosional bases, are graded and often rippled or megarippled. They generally are resistant partially winnowed packstones to crinoidal grainstones. Bioclastic material is moderately to highly fragmented and sorted indicating moderate to long distance transport. These beds are often overlain by a thin unit of laminated and sometimes burrowed siltstone which was deposited during the waning stages of the storm event. This package thus forms a "Kreisa sequence" (Figure 12) first described by Kreisa (1981) from the Martinsburg Formation (Upper Ordovician) of southwestern Virginia. Tobin (1982, p. 111-113) described nine variations of Kreisa’s idealized carbonate-Clastic cycle which occur in the Cincinnati Series (Figure 13). Distal Kope storm beds are generally thin packstone (units of two types: 1) finely broken skeletal material and ostracode valves which have been transported in suspension 32 and size sorted to a more distal location; and 2) lag deposits with autochthonous or parautochthonous whole to slightly broken skeletal material. The latter represents disruption and burial of a community with little or no transport. These beds generally have sharp erosional bases and often exhibit multiple storm episodes or microfacies. The degree of taphonomic feedback (Kidwell and Jablonski, 1983; Kidwell, 1986) in the lag deposits is often high with the remains of the previous community forming a firm substrate for a subsequent community to colonize. Multiply encrusted bryozoans (bryozoans encrusting on other bryozoans), and bryozoan encrusted crinoid stem segments are common. Alternatively, these beds can also be more proximal during weak winter storms which only have enough energy to stir-up the bottom and deposit a lag. In this case, distal areas would be undisturbed due to lack of significant bottom currents and would not leave a storm bed. During fair weather times, normal deposition would produce only carbonates. Terrigenous sediments were never deposited during fair weather on the Cincinnati shelf because of the greater distance from the Taconic source region. Therefore, a major influence of storm activity in the Cincinnati Series was to produce stratification by transporting allochthonous terrigenous sediments into the area from outside or resuspending terrigenous sediments 'deposited in an earlier event, thereby producing shale interbeds (Tobin, 1982). Many of the storm surges that 33 SHALE LfiMIHfiTED UNIT WHOLE FOSSIL FfiGKSTOHE SHQLE I SILT GRfiVEL ERAJJiSSIZE -——-—-% F1Qure 12 - Idealized vertical succession of sedimentary structures and lithologies in carbonate-Clastic cycles, Martinsburg Formation, southwestern Virginia (modified from Kreisa, 1981, fig. 3). 34 crossed the Cincinnati area were not shale bearing because of the greater distance between depositional site and terrigenous source area. Thus, some carbonate storm beds were capped by a protective shale layer and some were left exposed to the next storm surge. Individual Limestone Beds Generation of individual limestone beds is interpreted in this paper according to a model initially proposed by Mahan (1980; Figure 14). It is important to note the effect that storms had on community succession. Disruption by storms can result in either deposition of bioclastic debris and an insulating shale layer or deposition of debris with no protecting shale layer (Figure 14). In the former case, succession would start again from the pioneer stage, colonizing time top of the soft shale layer. In the latter case, the pioneer stage would be skipped because there is already a firm substrate of bioclastic debris on the seafloor. Therefore, by taphonomic feedback (Kidwell and Jablonski, 1983; Kidwell, 1986) from previous communities, communities reached higher states in the successional sequence, with diminished dependence on pioneer species to colonize unstable substrates (Mahan and Harrison, 1980). Storms thereby provide a very effective means of keeping diversity high by 'periodic "cropping" of communities and establishment of new communities on the old (Wilson, 1985). .Amm .mau .mmma .cdnos Eouuv ocounosaa «0 ocfix saw u mg .Aoamcn no ouoconumov noxwa swoon u um .Aouduadndoawo no ocoumcdwuw vague ocoumoEHH mean u an .Aocounxuwn no ocoumcdouo oozmmz xauooo .ocoumcuMHo onumoo. ocounoeda HmucoEmMHw n m .ocounuadn u m .ocouncdmuv no ocoumxomo HammON oaonz n 3 .udcs oo»MCasmH u q .oamnm u cm .mu:o>o Enoun camcan an ooudnoaoo one) Loan: pavedoom mo nuoxma ouococ nzouud .mucmaum> ofiuxu xumucoedoon oHuanuaoumconumo I ma ousmdm uldtlin‘ pll.l3.d -l(.lald pldllald hICIISOC 35 >ldll3.‘ 5.10.}.1 mhz<_m<> m40>0 :mOhm 36 .xumncwom UMEocozoou 30H n mma .Enoum xmumco cm“: 1 mm: .EuOum xwuoco no“: suo> u mmz> .Amv .osw .ommH .cmcm: sous molasses. cowumucoeficom oaox new Hopes Hmcowuunoaoo oouwuwvuca n he .Euoun xvuoco - «a ousmsm ZOHmZMLmDm 2H mmommmmm<0 mfizmmmDU AZOHBHmOmmD m4mm> onmzummsm mo 9:0 wqusmm / azmzHomm on»; 2.5 nele mmom ZZOBm UHQOHzmA AMIN mmommm so mzHma sestzzou mmzstzsssoo weak: 20.mmm00=m 295352048 .':.. ‘ '» gig;- ‘ Figure 16 r Typical grade 1 bed (4-25 1 ). Upper: photo illustrating successional sequence of brachiopods dominating lower portion of the bed and bryozoans gradually increasing in abundance to the top. Lower: photogram of the upper portion of 4-25 2 cut perpendicular to 4-25 1 (4X, scale bar is 1 cm). Immediately above the scale bar are brachiopods with a few crinoid ossicles; just to the right of the scale bar is the hollow ramose bryozoan Ceramophylla; the uppermost portion of the bed is dominated by Parvohallopora and Ceramophylla. 1+6 discussed below. These beds are always packstones. Fragmentation and abrasion are not evident tun: biotic corrosion by burrowing organisms may be (due to prolonged exposure before burial, i.e. low sedimentation rates). Disarticulation of skeletal elements is also more pronounced in this grade (Figure 16). Grade 2 - Interpreted as in situ autochthonous lag deposits, these beds exhibit little or no fragmentation of skeletal material auui are poorly sorted. Very fragile skeletal material may show some fragmentation. Crinoid stems and brachiopods are often articulated as the result of rapid burial and high sedimentation rates. Bryozoans usually dominate, followed by brachiopods and crinoids (Table 3). The packstone texture dominates (90%) with some partially winnowed packstones (10%). These beds are formed during low energy winter storm events or are distal deposits in more intense hurricane-force storms. Sometimes, they may show grading as the result of settling after a storm (Figure 17). Grade 3 - Interpreted as parautochthonous transported, poorly to moderately sorted and graded storm deposits or partially winnowed lag deposits. The degree of fragmentation of skeletal material is higher than in grade 2 with fragile forms moderately fragmented and more robust forms unfragmented in: slightly fragmented. These beds may often look superficially like a higher grade bed but can be easily distinguished by the coarser skeletal material found in them. Articulated brachiopods and bivalves are common. LP? ' "m: Figure 17 - Typical thin grade 2 bed (4-18). Upper: photo illustrating the bryozoan dominated packstone texture. Bioclasts are unsorted and whole to slightly fragmented. Lower: photogram of the area denoted in upper photo (4.5x, scale bar is 1 cm). The large bryozoan immediately above the scale bar, in the upper left and upper center are Ceramophylla. Whole disarticulated brachiopod valves are in the center. 48 Crinoid stem segments are rarely long (except on upper bed surfaces) and usually are broken into shorter segments cur disarticulated into separate ossicles. Bryozoans dominate, followed by brachiopods and crinoids (Table 3). Textures range from packstones (41.5%) to partially winnowed packstones (41.5%) to poorly washed grainstones (17%). These beds represent moderate energy winter storm deposition or distal to distal-medial beds during a hurricane-force storm. Grading is common and sometimes the beds will show small scale ripples and umbrella structures (Figure 18). Grade 4 - Interpreted as parautochthonous to allochthonous beds having undergone short to moderate transport with sorting of skeletal elements. Bryozoans (both robust and fragile) are fragmented and diminished in abundance (Table 3). Brachiopods and bivalves are slightly to highly fragmented.auui disarticulated. Disarticulated crinoid ossicles are usually a dominant component and individual ossicles may show abrasion (pitting and broken edges). Textures range from packstones (17%) to partially winnowed packstones (31%) to poorly washed grainstones (47%) to grainstones (5%). These beds represent high energy proximal type deposits. During a storm event, larger and heavier material is probably dragged along the bottom in the traction load and lighter material goes into suspension and is carried away some distance by bottom currents. This lighter material is deposited as thick sheets of bioclastic material with little or no mud. Grade 4 beds often exhibit Figure 18 - Typical grade 3 bed (4-17c). Upper: photo illustrating the bryozoan-brachiopod dominated partially winnowed packstone texture. Bioclasts are slightly sorted and whole to fragmented. Lower: photogram of the area denoted in upper photo (4.4x, scale bar is 1 cm). Articulated bivalve is in the center of the photogram and an articulated crinoid stem in the upper left. In the upper right is a longitudinal section of Parvohallopora, upper center is a transverse section of Heterotryp . Note fragmented valves. Figure 19 - Typical grade 4 bed (4-10a). Upper: photo illustrating the crinoid dominated partially winnowed packstone texture. Bioclasts are sorted and slightly to highly fragmented. Lower: photogram of the area denoted in upper photo (4.2x, scale bar is 1 cm). Umbrella structure is shown above scale bar; fragmented bryozoans are in the lower left; spar is in the lower right; ostracodes are to the left of the umbrella structure; disarticulated crinoid ossicles and fragmented valves throughout. 51 rippling or megarippling and sometimes cross-bedding (Figure 19). Alternatively, beds that do not show evidence of significant transport but have a high abundance of crinoids may simply be lag deposits from a crinoid- dominated community. Since Kope Formation crinoid ossicles from the common species are roughly the same size, such beds would appear hydraulically sorted but actually may have experienced minimal transport (Schumacher, personal comm. 1987). Grade 5 - Interpreted as allochthonous high energy transported and sorted proximal type thick storm deposits. Disarticulated crinoid columnals dominate, vHJfli other components of the fauna highly fragmented and diminished in abundance (Table 3). Textures range from partially winnowed packstones (13%) to poorly washed grainstones (67%) to grainstones (20%). Most of the mud has been winnowed except for occasional lenses trapped under shell fragments (umbrella structures) and coarse spar dominates. Megarippling and cross-bedding are common as are scour markings on the sharply defined bases of the beds (Figure 20). Grade 6 - Interpreted as thin distal allochthonous deposits composed of very highly fragmented and sorted skeletal material transported long distances. Bryozoans, brachiopods and bivalves are thin small forms which are fragmented. Ostracode valves (usually whole and disarticulated) dominate (Table 3). Textures range from packstones (67%) to partially Figure 20 52 ‘ . -' :. '5‘.» .Hi“: ~:."? ,.. “ Typical thick grade 5 bed (l~24). Upper: photo illustrating the crinoid dominated grainstone texture. Bioclasts are sorted and moderately to highly fragmented. Large rip-up clasts are shown in the left center. Two umbrella structures can be seen in the far right center. Lower: photogram of the area denoted in upper photo (4X, scale bar is 1 cm). Note the high degree of fragmentation and sorting, as well as the low abundance of bryozoans, and abundance of crinoids and spar. Figure 21 53 -.._r,.. Typical thin grade 6 bed (4-l4b). Upper: photo illustrating the size sorted ostracode-brachiopod dominated packstone texture. This bed represents two graded events: the first extends from the base of the bed with the large Ceramophylla colonies and fines upward to the layer of large crinoid ossicles (about 3‘cm from the base). These crinoids represent the base of the next event which fines upward again. Lower: photogram of the area denoted in upper photo (4x, scale bar is 1 cm). Lower portion of photogram is the upper portion of the first event. Note the high degree of size sorting. 5h winnowed packstones (17%) to poorly washed grainstones (8%) to grainstones (8%). These beds represent the very finest skeletal material plus mud put into suspension by storms and carried by bottom currents until current energy dissipates sufficienr1572for deposition of skeletal material and mud. Consequently, these beds are often graded vfiJfli larger fragments on the bottom of the bed with increasing ostracode and mud abundance towards the top of the bed (Figure 21). Grade 1, 2 and 3 beds make up almost 2/3 (64%) of the Kope limestones (Figure 22) indicating the majority of limestones have undergone little or no transport and sorting. This conclusion is consistent with other studies on the Kope (MacDaniel, 1976; Mahan, 1980; Tobin, 1982). The energy and taphonomic relationships between grades is summarized in Figure 23. Many interesting relationships involving taphonomic grade and other attributes of the Kope limestones have been found. For example, mean branch diameter of ramose bryozoans decreases with increasing grade (Table 4). Thus i situ and slightly transported lag deposits have larger (thicker) bryozoans than do more transported and sorted beds. This relationship seems obvious when one thinks of current transport mechanisms. Thick bryozoans cannot be transported far by the weak currents forming grade 1-3 beds. At best, they can be dragged a short distance in the mud before being buried. Even with higher energy currents, thick forms will travel very short distances and will not be carried as far 55 123456 e ee nmamwu rrrrrr GGGGGG unnaam o 1. 3 2L0 Figure 22 — Proportion of taphonomic grades. GRADE momizm flm>2mpOmfl mm>0§m2H>dOZ .IIIIII-nnnnwv 4| 04 00 ‘4. Eu RU ill mmeQ< taphonomic Summary of energy relationships between grades. Figure 23 — 56 as lighter material that comes to make up the higher grade beds. Thus, they will rarely be present in these higher grade beds and thin, easily transported forms will dominate. Taphonomic grade often helps delineate the Kope megacycles discussed above (Figure 24 and Appendix B). The thick beds that bound the cycles on top and bottom are usually of higher grade (4 or 5) and those in between are usually low grade lag or in situ deposits (grades 1, 2 or 3). Thus the carbonate hemicycle generally involves higher energy than the limestones in the shale hemicycle. The shale beds themselves are storm-generated. The high grade beds of the carbonate cycle are event beds and can be correlated between sections (Figure 24). Note that correlated beds often are of different grade so that a grade 4 bed can be correlated to a grade 5 bed and a grade 5 bed to a 6. This is simply a result of attenuation of storm energy away from the storm center. Grade 5 beds (thick grainstones) are most proximal to the storm center with grade 4 beds some distance further away, and distal grade 6 beds the product of fine-grained size sorted Haterial from the proximal areas carried away by bottom gradient currents. PALEONTOLOGY In this section, the faunal composition of the Kope Formation will be briefly described with emphasis on Figure 24 57 - Stratigraphic plot of taphonomic grade illustrating how grade defines megacycles and suggested megacycle correlations. Correlations are between high grade event beds (isochrons). Attenuation of storm energy away from the storm center results in changes in grade in event beds between sections. 58 W Figure 24 59 bryozoans (Appendix D). Brachiopods Bretsqu (1969) recognized three recurrent communities along a 600 mile transect of the Reedsville and Martinsburg Formations (Upper Ordovician) in the central Appalachians. These are tflua Sowerbyella-Onniella community, the Orthorhynchula-Ambonychia community and the Zygospira- Hebertella community. The Sowerbyella-Onniella community was found in an area extending from eastern Pennsylvania to central Virginia and is characteristic of the fauna of the Kope Formation in southern Ohio and northern Kentucky (Meyer et a1.,, 1981). Lorenz (1973) also identified a Zygospira- Rafinesguina community in the central Kentucky outcrop of the Clays Ferry Formation. Onniella, Sowerbyella and the less abundant Rafinesquina were adapted to living on soft substrates as evidenced by their concavo-convex shaped valves. Richards (1972) notes that a concave-upward life orientation allowed them to lift the commisure above the surface of the mud. Richards (1972) also suggests that Zygospira lived with its beak oriented toward the substrate, to which it was attached by a flexible pedicle. Zygospira has been observed attached to crinoid columnals and branching bryozoans. Crinoids Kope crinoids are usually disarticulated into stem 60 segments cu: individual ossicles and identification is impossible. Calices are better articulated vfiJfli ligaments auui are sometimes buried intact. From intact calices that have been found, Ectenocrinus, Heterocrinus, Iocrinus, and Gljptocrinus? are the most common genera (Cumings, 1908; Caster et a1., 1961). Cincinnatian crinoids either were attached by enmmusting bases or coiled the distal end of the column around objects such as bryozoans (Meyer et a1., 1981). Molluscs The most abundant bivalve genera in the KOpe are Ambonychia and Modiolopsis. Others include Similodonta and Praenucula? (reviewed by Pojeta, 1971). Gastropod genera include the abundant Loxoplocus and less abundant Liospira and Cyclonema. Molluscs are interpreted by Harris and Martin (1979) as appearing during the mature community stage. Arthropods Trilobites and ostracodes are abundant in some beds of the Kope Formation. Whole trilobites are often preserved in the shale layers (Brandt, 1980; Velbel, 1985). The most abundant trilobites are the distinctive Cryptolithus and Flexicalymene, followed by Isotelus and Odontopleura. 61 Bryozoans The dominant bryozoans found in the Kope Formation were (in order'cxf abundance) Parvohallopora, Ceramophylla, Batostoma, auui Heterotrypa (Figure 25). This differs from the abundances found by Anstey and Perry (1973; Figure 9, p. 36) from sections in southwest Ohio and southeast Indiana. They found Heterotrypa to be the most abundant trepostome bryozoan followed by Parvohallopora (formerly Hallopora), Peronqpora, Amplex0pora and Batostoma. These differences can potentially be accounted for by comparing the two studies. This study deals with stratigraphic sections in southwest Ohio and northern Kentucky; there may be a geographic change in bryozoan faunal composition from Anstey and Perry’s (1973) sections to the west and sections from this study to the east. Anstey and Perry (1973) dealt only with trepostome species whereas this study deals with all bryozoan_groups, thus they ignored the abundant genus Ceramophylla; if Ceramophylla is removed from Figure 25, the differences between the two studies become less pronounced. Anstey and Perry (1973) sampled their sections with a coarser collecting interval than this study, sampling only fragments exposed on the surfaces of limestone beds; they sectioned an average of 10 zoaria from each interval; the present study sampled and point counted all beds in the five measured sections retrieving a more complete census of bryozoan genera. 62 Rescaled Average Bryozoan Abundance (X) (averaged over all beds) 33.6 Parvohallorora Ceramophyl a Batostoma Heterotrypa Bgihopora Dekagla Stlgmatella Peronopora Others 21.0 3.5 3.5 4.2 [388888388 11.9 4.2 11.2 7-0 Figure 25 - Proportion of bryozoan genera. 63 Bryozoan Faunal Zones Anstey and Perry (1973) defined five assemblage zones based on five non-dominant bryozoan species: from lowest to highest, the Eridotrypa mutabilis Zone, the Sigmatella clavis Zone, the Balticoporella whitfieldi Zone, the Batostoma jamesi Zone and the Dekayia aspera Zone. The lowest occurrence of each zonal indicator defines the base of the zone; the top of each zone is the base of the overlying zone with the exception of the Stigmatella clavis Zone (Figure 26). The S; clavis Zone is defined as the interval between the top of the E; mutabilis Zone and the base of the B; whitfieldi Zone. The locations of the collecting localities in the Anstey and Perry (1973) study are shown in Figure 27. Exact locations can be found in Appendix 1 of Anstey and Perry (1973, p. 77). Note that section 6 in the Anstey and Perry study is the same as section 4 (Miamitown) in this study. The five faunal zones described above were also found in this study, with some minor exceptions. Only generic ranges were noted in this study so the species range names of Anstey and Perry (1973) will be shortened to generic range names. Eridotrypa was found only at the base of section 1 (Figure 28). This represents the top of the range of Eridotrypa le'the Point Pleasant Tongue (Karklins, 1984). Anstey and Perry (1973) found that the disappearance of Eridotrypa corresponded to the top of the Clays Ferry Tongue 64 A: lant, C = E: From variant 8, 9 8 Atasfgngrella var B: fleferntrxua variant A. fig. I D F 1972, 5P-: a l Eallgngra variant. the study area of Anstey and Perry (1972). n Anstey and Perry, m V S A R N w w m. M “$30 ‘ 3.2165. m .u u M h :QS: Stinky U m m 1 a >331. 3:: «E d u u a W” :9. 3649654 v, S a R E quota: 3.93.: GS: .. r. N F E E w m mm 3.6.525 3643 a: u u w n. in... S :2 .2er ex 5 6 I M n“ M 6 UP: is. ‘ a Etude»: a: m R M n 22‘: In 333 er“ I I'll"! V. Y m :63“. ~13 not um r mm 2Q; 264963? c W mm 3.3qu :oqoei 31‘ Q. C r < $9.59.. 3.6% :3. m. 3.3. S 32:03: wt 7 a l u U S 5 .l .l .| E4.) Q. hillllllllllllll o a M2.“ 1 I mt; C scoukufiutm R M. W [l E Shiite V g Cnoaoui :m u... M W woCQn‘ 1.?th .3 :29. e u o Emonoeul‘ % m M. Buzz. 282? ‘e 3.33: 312330 W R K ‘3: neouoeoqha m M ‘35:“. ueonoxw «4.: m :6 Soc: 3640 u out F 395 5 EL toe: ht mm mu 0 T Y 0 :m mm «w e a mm. mm N : nww a. S A D f E L m e M L L m “T D A C r. T I C H M T E E S O A S C n T S _ ;_ ‘;__:___ _;_______.____; o:__:_h new » u 1 z. a My L _ mmulx u. x w 6 5 _w 5 O Figure 26 - Stratigraphic ranges of Kope trepostome species in 65 :............ l o \ HAMILTON *‘ s DI-zAmmlm e “W - c \ 6 2. ' \ i _ I N . 1 ”" urination x 2 /~ 4 e ‘ .9. I Clem to“! noun a” liOONlfi OHIO “no“ So. ' §I\'|8I\ 0123458.: (”'—- SWITZERLAND \.:.\‘~ l' «mo ‘é. \ \ s GALLATIN _ Ham 1 ‘1'“. I, X‘ r , / d 1 I Figure 27 - Anstey and Perry (1972) collecting localities. From Anstey and Perry, 1972, fig. 1. 66 in eastern Indiana. The disappearance of Eridotrypa is noted by McFarlan and Freeman (1935, p.2001) as a widespread phenomenon over the Cincinnati Arch area at similar stratigraphic horizons. Anstey and Perry (1973) state that the disappearance of Eridotrypa was probably environmentally controlled because it corresponds closely to the change from the micritic limestones of the Clays Ferry Tongue (and Point Pleasant Tongue of the Clays Ferry Formation) to the predominant shale of the Kope Formation above. Therefore, Eridotrypa preferred shallower and less turbid waters than present in the deeper and muddier Kope. Anstey and Perry (1973) found Stigmatella to be present in both the lower and upper Kope but not in the middle. Dalve (1948) also reports Stigmatella in the upper and lower Kope but does not list it among species found in the middle. A similar pattern is noted in this study (Figure 28, dashed lines). The "barren" zone varies from section to section but its base is usually around 20m from the base of the section. Only the section 1 and 5 composite (Appendix F) shows the thickness of the "barren" zone (approximately 9.2m). Stigmatella was found in section 4 (Miamitown - Anstey and Perry section 6) in this study (Figure 29, Appendix F) but was not found by Anstey and Perry (1973, Figure 26). Stigmatella is very sparse ((1.0%) in this section, however, and tine abundance decreases upward to <0.5% near the top. The growth ferm of Stigmatella also changes upward in the Kope. From the base to about 3m above the base, Stigmatella 67 IEOuOO~lm «3.23.5.4 2398.9: . a. .2828: «32.3320 1 .1‘ 2.22.225 23:08.80 33.203:— 22.055— 323:9...— 22.2.2.0an 2.3325 1 Pt. Pleasant — Bryozoan generic ranges in ascending sequence in -Figure 28 (sections 1' the southeastern sections composite and 5). 2, 68 038.00 0. 3.305200 2 3.2.22... 0. .0. 0 £23.. 20082.... 00.33.52 002.230... 0.20.3.5 20n0.0..m 3.0.00... 20 200 0. .202... IsOQO£~> u . 2000.321 0. .2000EE.00£50< ll 2000x018< I 0. .20005200 20202011 Pt. Pleasant - Bryozoan generic ranges in ascending sequence in the northwestern sections and 4). 29 'Figure composite (sections 3 69 is a robust ramose form and is the most abundant bryozoan. Above this point, there is a drastic change in growth habit to predominantly a thin encruster on crinoid stem segments usually of minor abundance. This change in growth form corresponds to the upper limit of the Eridotrypa Zone and probably represents a response to deepening, muddier waters. Apparently, the ramose species of Stigmatella could not survive this environmental change. Similarly, Eridotrypa was not able survive either, and disappeared. The waters of the middle Kope may have been too deep for Stigmatella so it was absent there. The somewhat more limy shallower waters of the upper Kope provided a similar environment to the lower Kope and Stigmatella reappears as an.encruster on crinoid stems. Batostoma has long been known as a zonal index of the middle iKope (Nickles, 1902, p.72). Anstey and Perry (1973) found that Batostoma was restricted to the middle portion of the Kope in the northern part of their study area (composite 2, Figure 26) but was found only in the upper Kope in the southern part (composite 1, Figure 26). The present study finds Batostoma to range from the middle Kope to the upper Kope in both the northwest and southeast composites (Figures 28-29). The base of the Batostoma Zone is seen to shift downward slightly from northeast to southwest. The upward shift in this zone to the south is most likely controlled by a difference in the rate of terrigenous sedimentation between the north and south (Anstey and Perry, 1973). The source of some of the Kope’s terrigenous material may have 70 been the middle Ordovician Blount Delta in eastern Tennessee (approximately 200 miles south of time study area) as evidenced by the laterally gradational Garrard Siltstone in central Kentucky (Anstey and Perry, 1973). The rate of terrigenous sedimentation was therefore higher in the south. Dekayia was found to be a zonal indicator of the upper Kope in this study and by Anstey and Perry (1973). Its first appearance occurs in the deeper waters of the upper-middle Kope (Figures 28, 29, and 68) and it continues into the shallower water Fairview. The base of Dekayia’s range is lower in the north (composite 2, Figure 26 and Figure 29) and shifts upward to the south (composite 1, Figure 26 and Figure 28). This indicates that Dekayia was probably not tolerant of the higher levels of terrigenous influx in the south, thus causing Dekayia to appear later to the south. In the north, terrigenous influx was less of a factor allowing Dekayia to appear lower in the section. This earlier appearance in the northeastern sections may indicate deeper waters to the north, consistent with a northward dipping paleoslope (discussed above). Balticoporella was found in only two sections in this study (sections 1 and 2, Figure 28 and Appendix F). In the first section, the range for Balticoporella significantly overlaps the range of Eridotrypa. In section 2, Balticoporella was found at the base of the section, about 8m above the base of the Kope. Balticoporella was not found in section 4 (Miamitown) but was found at the very base of 71 that Section by Anstey and Perry (1973), in a bed that is no longer exposed. Other trends in the ranges of non-trepostome genera can be described (Figures 28-29). Arthrostylus, Graptodictya, Stictoporella and Stictopora are all thin stick-like forms which can be described as taphonomically sensitive genera because they are easily transported in suspension and are often the dominant bryozoans in highly size sorted beds (especially grade 6). Thus, their ranges may be artificially extended by downslope or upslope transport. Cryptostomes, with tflua exception of Stictoporella, are not found in the shallow uppermost portion of section 5 (Figure 28), possibly because of the shallower waters and more limy and firm substrates of the upper Kope (Figure 68). Ettensohn et al. (1986) found cryptostomes abundance increased from intermediate to offshore facies of the Sulpher Well Member (xf the Lexington Limestone, but were not found in the nearshore facies. The abundance of Arthrostylus increases from the middle to the upper portion of the Kope, which may reflect its ability to tolerate shallower, higher energy waters of the upper Kope (Figure 68) because of its jointed zoarium. Ceramophylla ranges throughout the Kope except for a few meters at the base where it is not present. Ceramophylla is a taphonomically sensitive genus because of i135 hollow' endozone making it very light and resulting in a hydrodynamic behavior similar to the very thin cryptostomes 72 and Arthrostylus. Ceramophylla is often found size sorted along with these thin forms in grade 6 beds. Thus the range zones of Ceramophylla and the other hollow ramose ceramoporines (Crepipora and Ceramoporella) may be artificially extended by downslope or upslope transport. Bryozoan Paleoecology Studies of both Recent and fossil tuyozoans suggest that colony growth forms vary in some way with water depth. It is uncertain which environmental factors that covary with depth are responsible for these responses (Anstey et al., 1987a). Stach (1935, 1937), from a study of Cenozoic cflmfllostomatous bryozoans, concluded that a definite relationship exists between the various zoarial growth forms and their habitat. The particular feature of the habitat which influenced zoarial growth form in Stach’s work was the nature of the substrate. Rucker (1967), in his study of Cenozoic bryozoans along the coast of Venezuela and British Guiana, also concluded that substrate was the principal factor influencing the distribution of bryozoans along the shelf. Lagaaij and Gautier (1965) studied Recent specimens from the Rhone Delta. They concluded that the rate of sediment deposition is one of the major controlling factdrs on distribution of bryozoans and that temperature and depth also play important roles. Askren (1968) inferred depth- 73 related changes in zoarial growth habit in Upper Eocene and Oligocene bryozoans from Alabama. He notes that encrusters replace erect forms as water depth decreases and amount of terrigenous material and agitation increases. Similarly, the ratio of rigid to jointed ramose forms decreases with decreasing water depth and increasing turbidity. Similarly, Schopf (1969), in his study of Recent bryozoans off the New England Coast, found that the proportion of species that are erect rather than encrusting increases in a regular manner with depth; and that erect species that are rigid rather than flexible are found extensively in samples from deeper than 35 meters but are rare in shallower water. Schopf (1969) and Lagaaij and Gautier (1965) found that species diversity of bryozoans increases with increasing water depth to a maximum of 50 meters, then decreases in deeper waters (up to 250 meters). Ettensohn et a1. (1986) also found increasing bryozoan diversity with depth in the Middle Ordovician Sulpher Well Member of the Lexington Limestone in central Kentucky (Figure 1). They alSo note a change in growth habit from stout ramose colonies in shallow waters to encrusting and platy foliaceous zoaria in deeper waters (just the opposite of Askren 1968 and Schopf 1969 ). Depth-related changes in bryozoan generic diversity and growth form can also be documented from the Kope Formation and are discussed below. 7L, Bryozoan Succession Grade 1. (i_ sit_) beds offer an opportunity to study the process of succession in Edenian communities. As mentioned above, the lower portions of grade 1 beds are brachiopod dominated and the upper portions are bryozoan dominated. Of the five grade 1 beds found.iJi'this study, four are from the upper Kope (specimens 3-19, 3-20, 3-23 and 4-25) and one is from the middle Kope (1-26). In the upper Kope beds, the dominant pioneer genera appear to be Bythopora, some Parvohallopora and Ceramophylla. The abundance of Bythopora gradually decreases towards the top of the bed while that of Parvohallopora and Ceramophylla increases in a parallel manner. The climax community is dominated by Parvohallopora with Ceramophylla next in abundance and others (Perongpora, Stigmatella, Heterotrypa, Bythopora and the cryptostomes Graptodictya, Stictoporella, and Stictopora) subordinate. Bryozoan diversity is highest in the upper portion of the beds. The bilaminate genera (Peronopora, Graptodictya, Stictoporella and Stictopora) are usually only present in the uppermost portions of the bed and can be considered members of the mature stage of successiOn. Bythopora, a thin ramose form, can be considered an opportunistic, colonizing genus because of its dominance in the pioneer stage of community development. Bryozoan abundance in bed 1-26 is low, so not much can be said in specific about succession, but in general it 75 appears that Batostoma is dominant in the lower portions of the bed with some Parvohallopora present. Parvohallopora becomes dominant near the top of the bed. Bythopora is quite sparse in the middle Kope, possibly due to the deeper waters. Pachut and Anstey (1979), in a study of developmental relaxation in trepostomes, concluded that Parvohallopora and Heterotrypa were r-selected Opportunistic genera (opposite this study) and that Amplexopora and Peronopora were K- selected equilibrium genera. Further study of succession in both the bryozoans and the other community members in grade 1 beds in the Cincinnatian is needed. Bryozoan Communities A plot of grade 1-3 beds showing the abundance of the seven most abundant bryozoan genera identifies three different bryozoan communities (Figure 30). These communities are named for the three most dominant bryozoan genera within each zone. The three communities are, in- ascending order: 1) Parvohallopora-Ceramophylla-Stigmatella; 2) Parvohallopora-Heterotrypa-Ceramophylla; and, 3) Parvohal1opora-Batostoma-Ceramophylla. The intergrading nature of these communities suggests distribution along a continuum. The trend in abundance of Ceramophylla closely parallels the trends in sea-level (Figure 68) being highest in the shallow-water zones, suggesting Ceramophylla 76 a Parvohallopora BCeramophylla B Batostoma ('3 g Heterotrypa é a Bythopora l' m Dekayia S B Stigmata! la Cum. Abundance Figure 30 — Cumulative abundance of the seven dominant bryozoan genera for the section 1&5 composite showing the three bryozoan communities named from the three most dominant genera in each zone. Abundance curves are smoothed using a simple moving average and the plot extends to 100% (not shown). P-C-S = Barrehailm—Qeramgbhrlla- Stigmatella; P-H-C = Wi-W' Ceramophxlla; P-B-C = WM: narostdma- Ceramophylla, The plot is of bed number and ignores the intervening shales, thus the vertical meter scale is not linear. 77 preferred shallow waters. A plot of bryozoan, brachiopod, crinoid and bivalve abundance for grade 1-3 beds (Figure 31) suggests that the majority of the Kope communities overall were tmyozoan- brachiopod dominated. Bryozoan-crinoid and brachiopod- crinoid dominated communities occur in the zone of highest crinoid abundance (from about 4 m to 20 m above the base of the Kope). Faunal Relationships Vertical trends in relative abundances of the various constituents that make up the Kope limestones have been noted previously by Mahan (1980, p. 69-75, figs. 27 and 28). He notes a strong inverse relationship between the distribution patterns of crinoids and bryozoans and a weak inverse relationship between the distribution of bryozoans and brachiopods in the Brent road cuts. Data from this study indicate that crinoids generally increase as bryozoans decrease, and vice versa. This inverse relationship is illustrated by a cumulative line chart of 'moving averages to udnimize local effects (Figures 32 and 33). No consistent relationship can be observed between the relative abundances of bryozoans and brachiopods (Figures 32 and 33). An overall pattern of three peaks separated by three lows in both bryozoan and brachiopod abundance can be seen in Figure 32. The overall trend for crinoids is low near the base of the section and gradually increases to a 78 E Bryozoans E Brachi0pods a Crinoids B Bivalves UT-KDF+(DEB 0 60 PP 50 40 30 20 10 0 Cum. Abundance Figure 31 - Cumulative abundance of bryozoans, brachiopods and crinoids for the section 1&5 composite showing four communities named from the two most dominant groups in each zone. Abundance curves are smoothed using a simgle moving average and the plot extends to 1 0% (not shown). B-Br = Bryozoan-Brachiopod, B-C = Bryozoan-Crinoid and. Br-C = Brachiopod-Crinoid communities. The plot’ is of bed number and ignores the intervening shales, thus the vertical scale is not linear. “(D0352 Q0303 Figure 32 79 _-Zj:-Ij:-I'- Crinoids ................... -. "'3: .2 Brachiopods _::::::::::::::::}- ':::'-.::':.' Bryozoans ............. Mlctlte Spar El Other 20 80 100 Rescaled Pp - Component line chart of rescaled crinoid, brachiopod, bryozoan, micrite, spar and other abundance for the section 1 a 5 composite. Others include trilobites, bivalves, ostracodes and unidentifiable fragments. The y-axis plots only the limestone beds and ignores the intervening shales. d N u m b e r 60 Figure 33 80 Trilobites ' Bivalves Ostracodes Crinoids Brachiopods - Bryozoans Other' 50 4o 30 20 10 0 Rescaled Pp - Component line chart of rescaled trilobite, bivalve, ostracode, crinoid, brachiopod, bryozoan and other abundance for the section 1 a 5 composite. Others includes micrite, spar and unidentifiable fragments and extends to 100 (not shown). The y-axis plots only the limestone beds and ignores the intervening shales. 81 peak corresponding to the first low in brachiOpod and bryozoan abundance, then gradually decreases to the Fairview contact. The trend in bivalve abundance is bimodal, being highest in the middle of the section and lowest near the base and top (Figure 33). The peak in bivalve abundance corresponds to a peak in bryozoan abundance._Ostracode abundance patterns are the inverse of that for bryozoans (Figure 33), having two central highs corresponding to the lows in bryozoan abundance, and a central low corresponding to a high in bryozoan abundance. Ostracode abundance is also low near the base and top of the sections, the opposite of that of bryozoans. Trilobite abundance gradually decreases from the bottom of the section to the top. The predictable inverse relationship between the amount of spar and micrite is shown in Figure 32. The amount of micrite is high in the base, middle, and top of the Kope with lows in the lower and upper middle. Spar has highs corresponding to lows in micrite and lows corresponding to micrite highs. The overall trend in micrite abundance roughly parallels the abundance trend for bryozoans. The other three sections show very similar abundance trends to the Brent sections with some slight shifting of peaks stratigraphically up or down. This suggests that the factors controlling abundance of organisms in the KOpe were geographically widespread but diachronous between sections. The most likely causal mechanism would be regional sea-level 82 changes which would affect the somewhat shallower southwest sections differently than the deeper northwest sections along tflua paleoslope and result in diachronous faunal abundance "signatures" between sections. Sea-level changes in the Kope will be discussed further below. Alternatively, differing rates of sedimentation between the various sections could also produce apparently diachronous shifts in faunal abundance "signatures." This could be accomplished by depositing more or less limestone or shale in one section compared to another so that a isochronous faunal abundance "signature" would be shifted up or down when compared to another section, thus appearing diachronous. BATHYMETRIC, TAPHONOMIC AND DIVERSITY TRENDS At first glance, the monotonous interbedded shales and limestones of the Kope Formation would lead one to believe that sea-level was fairly constant throughout Kope deposition. This is not the case, however. A closer look reveals stratigraphic changes in the shale to limestone ratio, texture of the limestones, taphonomy, and faunal diversity. This section briefly discusses previous work (n1 paleobathymetry of the Kope Formation and compares these results with evidence for changes in sea-level from taphonomy and bryozoan diversity trends. 83 Kope Paleobathymetry - Previous Work Anstey and Fowler (1969) inferred an upward shallowing of water in the Kope which continues into the overlying Dillsboro (Figure 1). This relationship is suggested by an upward decrease in the wavelength of megaripples, an upward increase in limestone content, an upward increase in faunal abundance and diversity, and the presence of oncolites and mud cracks in the Dillsboro (Anstey and Fowler, 1969). They note that bryozoan growth forms present in the Kope suggest deposition in relatively deep, quiet water, most likely 20 m or more in depth. ' Anstey and Perry (1973) concluded that indices of bryozoan taxonomic diversity generally have maximum values near the baSe and top of the Kope and minimum values in the middle. Pachut and Anstey (1979; Figure 10, EL. 182) plot Brillouin diversity indices based on samples from the study of Anstey and Perry (1973). Averaging diversity indices over all sections shows a high diversity zone from the base of the section to about 27 m above the base; a low diversity zone from 27 m to 40 m; and a high diversity zone from 40 m to the Fairview. Coarseness of samplimg intervals and potential sampling of taphonomically overprinted beds makes comparisons difficult, however. Similar trends in diversity were found in this study (discussed below) with a high diversity from the base of the section to about 35 m above the base; a low diversity zone from 35 m to 45 m; and a high diversity zone from 45 m to the Fairview (Figure 68). Anstey 84 and Perry (1973) suggest that these values reflect shallower water conditions at the beginning and enui of Kope sedimentation, and deeper water near the middle based on analogy to patterns noted by Schopf (1969) on Recent bryozoans. MacDaniel (1976, fig. 18) suggests a similar pattern of gradual deepening of waters to the middle Kope, then a gradual shallowing through the upper Kope up to the Bellevue based on fossil community analysis. The lower Kope is dominated by a Rafinesquina-Zygospira nearshore type community which is gradually replaced by an Onniella- Sowerbyella offshore community in the middle Kope. Continued shallowing of waters leads to replacement of the Onniella- Sowerbyella by a Rafinesquina-Zygospira community in the upper Kope which is replaced by a Platystrophia-Hebertella rmmrshore shoal community in the upper Fairview through Bellevue sequence. The resulting symmetric sea-level curve for the Kope follows the curve of Flower (1946, Fig. 8) that was supposed to illustrate invasions from the "austral" and "boreal" cephalopod provinces. A similar pattern of faunal displacement to that found by MacDaniel (1976) for brachiopods and Flower (1946) for cephalopods was found by Anstey (1986) and Anstey et al. (1987a) for bryozoans. They found a gradual process of biome displacement in response to changes in both the supply of -siliciclastic sediments and sea-level. Gradient analysis of two stratigraphic sections, the Moffett Road cut in northern 85 Kentucky (Point Pleasant through Kope) and the Tanner’s Creek section in southeastern Indiana (uppermost Kope through lowermost Whitewater), showed a predominance of Reedsville-Lorraine (nearshore siliciclastic) taxa in the Point Pleasant, a predominance of Cincinnatian (intermediate carbonate-Clastic) taxa in the upper Kope and lower Dillsboro (Fairview), and a predominance of Red-River Stony Mountain (offshore carbonate) taxa in the upper Dillsboro. (Anstey et a1., 1987, p. 170-171). Anstey et a1. (1987, fig. 8) note consistent patterns in smoothed second-order curves of proportion of the bathymetrically sensitive conodont Phragmodus undatus (Sweet, 1979), reciprocal averaging of species diversity first axis, the three biome signatures of Anstey (1986), and the sea-level curve of Hay (1977, Figure 34). These patterns represent synchronous stratigraphic fluctuations in bryozoans, conodonts, and both minor lithologic and major bedding characteristics. They note that an overriding mechanism to explain such correlations from heterogeneous sources could be second-order fluctuations in water depth. Averaging all 6 curves thus gives an overall sea-level curve (Figure 34). This sea-level curve shows a gradual deepening of water to the middle then a rather abrupt shallowing ixi the uppermost Kope. This curve is consistent with the conclusions noted above. .Diversity Trends The distinction between biological diversity and 86 3. HAY(1977) Redflwmr ’ RNPSD , - -- Clnclnnatl DILLSBORO' l KOPE Figure 34 - Smoothed second—order curves plotted against the smoothed first polar axis (dashed lines). The mean curve was determined by averaging the values of the six smoothed curves. The scale on all curves increases from zero (at left) to 100% (at right). Higher values of the mean curve are inferred to represent deeper water. After Anstey et al. (1987a), fig. 8, p. 173. 87 taphonomically overprinted diversity is an important one and one that is often ignored in paleoecological analysis. Biological diversity refers to diversity in those beds which exhibit no or minimal taphonomic effects. Taphonomically overprinted diversity refers to diversity in those beds which exhibit moderate to high taphonomic effects (multiple reworking and condensation, transport, sorting and extreme fragmentation) which tend to alter the original diversity of a particular community. Diversity generally is inversely proportional to grade (as grade increases, diversity decreases) with one exception (Table 5, Figure 35). Cross-correlation indicates a correlation coefficient of.-0.61. Average diversity decreases from grade 1 to grade 5 beds, then increases slightly in grade 6 beds. This is exactly the same pattern as seen in the average abundance distribution of bryozoans and brachiopods (Table 4). Grade 6 beds are distal accumulations of highly fragmented and sorted bioclasts so that diversity is artificially concentrated. Evenness, a measure of how evenly species are distributed in a community (maximum evenness occurs if all the species abundances are equal Pielou, 1969, p. 222 ) follows the same pattern as the diversity index. Thus, in low grade beds, communities are buried with little or no transport and sorting and may be mixed with .subsequent communities that colonize on its remains, giving a high diversity assemblage with potentially high evenness. 88 E Brlll.Dlverslty Index . m Taphonomic Grade . 44 B e d N U m b e r 22 0 5 4 3 2 1 0 Grade. Index Figure 35 - Non-cumulative line chart of smoothed Brillouin diversity index and taphonomic grade for the section 1 a 5 composite. The y-axis plots only the limestone beds and ignores the intervening shales. smoothing was performed using a simple moving average. 89 Selective transport of all but large bioclasts in higher grade beds leads to very low diversity and relatively high abundances of one or two genera resulting in low evenness. Diversity indices plotted stratigraphically’(Figure 35) show an initial high in the lowermost Kope, a low throughout the middle Kope, then another high in the upper Kope. This is the same pattern found by Anstey and Perry (1973) discussed above. The other sections show the same pattern of low diversity in the middle Kope and high in the upper Kope. This suggests that water depth was shallower in the upper and lower Kope and deeper in the middle. In the section 1 and 5 composite, the average diversity index for time lower Kope is 1.25, 0.75 in the middle low diversity zone, and 1.17 in the upper Kope. In the other sections, the low diversity zone ranges from 0.70 in section 4 (Miamitown) to 1.28 in section 3 (Mt. Airy). The upper high diversity zone ranges from 0.85 in section 2 (Sanfordtown) to 1.57 in section 3. The total percentage of shale is also higher in the low diversity zone indicating deeper waters (Figure 68). For the sections 1 and 5 composite, the lower Kope high diversity zone is 81% shale, the middle low diversity zone is 91% shale, and the upper high diversity zone 83% shale. The low diversity and upper high diversity zone (respectively) shale percentages for section 3 are 91 and 88, and for section 4, 96 and 85. The proportion of jointed erect forms is higher in the 90 Table 5 Average log base 2 Brillouin diversity index and evenness for taphonomic grade (all five sections). Grade ' W Ennnesa 1 1.75 0.60 2 1.54 0.57 3 1.33 0.53 4 0.71 0.40 5 0.51 0.29 6 0.69 0.38 91 the upper Kope indicating shallower, more agitated waters in this zone (discussed above, Figure 68). In the upper Kope, the proportion of Arthrostylus, a jointed rhabdomesid stick- like form, increases. The proportion of encrusting forms was found by Anstey and Perry (1973) to be higher in the southern part of their study area than in the north, but data from this study shows no consistent patterns. The above conclusions of higher diversity 1J1 shallow waters seem to be contrary to work by Schopf (1969). Some features of Schopf’s (1969) study, however, make application of his conclusions questionable in Paleozoic epeiric seas. These features stem from the problem of comparing data from marginal seas (in this case the Atlantic Ocean) to shallow epeiric seas: 1) Substrate - Schopf (1969, fig. 3) notes a high percentage of sand in shallower samples up to about 150 m, a high percentage of silt and/or clay in deeper waters, and about the same percentage of gravel independent of depth. At the time of deposition of the shale-dominated Kope, the substrate was nearly all silt and/or clay at depths less than 50 m. The variety of depth dependent substrates available for bryozoans (Schopf, 1969, fig 4) is much greater off the Atlantic coast (hydroids, loose forams and sand grains, shells and rocks) than in the Kope (shells). 2) Depth and energy gradients - depth and energy gradients are much steeper off the Atlantic coast than in low relief epeiric seas such as existed in the Middle and Upper 92 Ordovician. This is especially true when looking at a small portion of an epeiric sea, such as the Cincinnati region. Schopf (1969, EL. 240) notes that storms in the North Atlantic may have wave lengths of 156 to 225 m (wave bases = 3.5 mm) based on breaks in size distribution (Figure 36; Table 6). RA and DCA assign a unique score to each genus (in R- mode) and bed (in Q-mode) for all four axes. These axes can ‘then be plotted by themselves or against each other resulting in each genera or bed occupying a single point in 104 Table 6 Aspects of bryozoans used in DCA and RA plots No. Genus Pref. Growth Avg. Size(mm) Suborder 1 AgantngcgramL Hemispherical 12.0 Ceramoporina 2 Amplgxgpgra, Encrusting 4.2 Amplexoporina 3 Arthrostyln: Thin ramose 0.2 Rhabdomesina 4 Atagtgngna Encrusting 0.4 Amplexoporina 5 Atactgpgrella, Encrusting 0.5 Halloporina 6 Baltiggpgrg111_Ramose 3.0 Halloporina 7 Batostoma_ Ramose 3.5 Halloporina 8 Bribenera. Thin ramose 0.5 Halloporina 9 Ceramgpnxlla Hollow ramose 2.5 Ceramoporina 10 Ceramoporella_ Hollow ramose 2.3 Ceramoporina 11 Crepipgra Hollow ramose 2.3 Ceramoporina 12 Dekaxha Ramose 2.5 Halloporina 13 Eridotrypa, Ramose 3.5 Halloporina 14 Graptodictya, Thin bilam. ramose 0.3 Ptilodictyina 15 Heterotrypa Ramose 3.4 Halloporina 16 ugmgtryp§_ Ramose 3.5 Halloporina 17 Earxgnallgpgra Ramose 1.6 Halloporina 18 Eergngpgza, Frond. bilaminate 1.4 Halloporina 19 Stictopora Thin bilam. ramose 0.3 Ptilodictyina 20 fitictgnorglla, Thin bilam. ramose 0.3 Ptilodictyina 21 Stigmatella Encrusting 2.4 Halloporina 105 ordinatixni space. Those points that have a particular attribute in common can be divided into fields. Distinct fields exhibit two properties: 1) they occupy a unique portion of ordination space and do not overlap other fields, and 2) they cluster points with like attributes together. The more distinct a field is, the better the ordination with respect to that attribute. DCA axes l and 2 when plotted against each other show a fairly distinct zonation of the growth habit fields (Figure 37). Axis I ordinates from predominantly ramose forms in the left portion of Figure 37 to encrusting forms to the right and bilaminate forms in the center. This pattern is even more distinct when the data are run with time rare genera omitted (Figure 38) but becomes less distinct when the rare genera are downweighted (Figure 39). RA plots for growth habit showed a high degree of point clustering and therefore are not considered here. A closer look at Figure 37 reveals some interesting patterns. For example, Stigmatella is a predominantly ramose form in the Eridotrypa zone of the lower Kope and becomes an encrusting form above that. Thus Stigmatella (21), a predominantly encrusting form, plots near the ramose field and adjacent to Eridotrypa (13). The hollow ramose ceramoporids (Ceramophylla 9 , Ceramoporella 10 , and Crepipora 11 ) all group closely together as do the bilaminate forms (Graptodictya l4 , Peronopora 18 , Stictopora 19 and Stictoporella 20 ). COSQCJOW‘ N m—oxp 400 . P -verythln thln medium thick lllllllllillllllll 2 4 6 8 Branch Diameter (mm) Figure 36 - Histogram of branch diameter of ramose bryozoans for all stratigraphic~ sections (N=2649). Thickness divisions are used in subsequent R-mode plots. ' llllllllllllll § . Figure 37 - R-mode growth habit plot of DCA axis 1 vs. 2 with all grades included. H=hemispherical, R=ramose, B=bilaminate, Esencrusting. Numbers refer to bryozoan genera listed in Table 6. 1lllllllllllll lllL Figure 38 - R-mode growth habit plot of DCA axis 1 vs. 2 with all grades included and rare genera omitted. R=ramose, Babilaminate, E-encrusting. Numbers refer to bryozoan genera listed in Table 6. 5” ’ T T r 1 I I I I I I I I T I I I 1 I I - 420 ' 5 —3 5 A 32° ° 9 d: X , 3 1 22° R 2 130 15 -E I '12 1 7 '11 3° #1 7 — -m i 4.. J 1 _L J I 1 1 1 1 L 1 1 1 1 : o 100 300 , 300 400 AXflii Figure 39 - R-mode growth habit plot of DCA axis 1 vs. 2 with E=encrusting. Numbers all grades included and rare genera downweighted. H=hemispherical, R=ramose, B=bilaminate, refer to bryozoan genera listed in Table 6. 108 RA and DCA plots for colony size with all genera included showed very indistinct fields with a high degree of overlap with RA again showing a clustering problem. Downweighting rare genera helps delineate the fields but the rare genera must be omitted before a pattern emerges. The DCA plot (Figure 40) of axes 1 vs. 2 with rare species omitted shows that axis one is ordinating from thick forms to the left and thin on the right with very thin forms occupying the central portion of the plot. Crosstabulation indicates that this correlation is significant at time 74% level (contingency coefficient = 0.94). The RA plot of axes 1 vs. 4 (Figure 41) shows a similar pattern. Considering both the growth habit and size plots for the first DCA axis (Figures 37-40), a potentially bathymetrically controlled pattern emerges. Axis l ordinates from ramose to encrusting and from thick to thin, the same pattern found by Ettensohn et a1. (1986) in the Lexington Limestone. In their interpretation, thick ramose forms occupied a shallower near-shoal position with encrusters more offshore. Thin and very thin bilaminate forms occupy an intermediate position on DCA axis 1. Ettensohn et a1. (1969, fig. 10) note that cryptostomes occupy an intermediate to offshore position. This pattern may also be related to sedimentation rate (Lagaaij and Gautier, 1965) with higher sedimentation rates expected nearshore and slow sedimentation offshore allowing encrusters to grow without being overcome and/or buried by sediment. E 300:— A ” ‘ ’x‘ :3 ‘ 8 2a)::- 2 t: 'iOO— ' 0,14 1114 1 Llfil 1 1 1 l 1 L 1 17 0 100 20) 3d) 40m $0811 Figure 40 - R—mode size plot of DCA axis 1 vs. 2 with all grades included and rare genera omitted. T=thick, M=medium, Th=thin, VThavery thin. Size divisions are shown in Figure 36. Numbers refer to bryozoan genera listed in Table 6. 37o- . r . _ 27o .5 170 .: 5 7° ”5 4 -m '- _: : : ~1ao 1;— ‘5 Z :I -230 b 4 - 1 '- 470 '8‘ RXHBi Figure 41 - R-mode size plot of RA axis 1 vs. 4 with all grades included and rare genera omitted. T=thick, H=medium, Th=thin, VTh=very thin. Size divisions are shown in Figure 36. Numbers refer to bryozoan genera listed in Table 6. 110 Plots of bryozoan genera grouped according to their subordinal membership (Table 6) are shown in Figures 42 and 43. The plots for DCA with the original abundance data show a high degree of overlap of the subordinal fields. Downweighting rare genera reveals the same indistinct pattern. When rare genera are omitted, DCA axis 22 (Figure 42) ordinates from Suborder Halloporina to the left to Ptilodictyina on the right. The actual gradient may be slightly oblique to DCA axis 2 in which case the ordination would be from Halloporina to the left and Ceramoporina and Rhabdomesina on the right. RA axis 2 with rare genera omitted (Figure 43) shows a similar pattern to the DCA second axis. However, the quadratic dependency of the RA second axis to the first axis makes this ordination suspect. This gradient emphasizes the differences between the various suborders. Members of the Suborder Halloporina are ramose tun encrusting with a well defined endozone and exozone with mesopores and may or may not have acanthostyles, diaphragms/cystiphragms, and monticules. Ptilodictyines are thin branching forms with elliptical branches (in transverse section) with a central band or mesotheca from which zooecia originate. The rhabdomesine Arthrostylus is a thin jointed ramose form with an axial region from which zooecia radiate. The ceramoporine Ceramophylla is a hollow ramose form with a basal layer of .dense calcite from which zooecia arise. Lunaria are common as are exilazooecia; diaphragms are absent. m I U I T 1 I I I U l I I I I I V I I U 400 -E A a“) 8 -E EM 3 3 * 7 H '17 E i 100 '12 18 o k J_ J _ L1? 1 1 1 Al 0 100 3a) 400 0X18 2 - - ode subordinal plot of DCA axes 2 vs. 3 with Figure 42' aglmtaphonomic grades included and rare genera omitted. . H=Halloporina, P=Ptilodictyina, R=Rhabdomesina, C=Ceramoporina. Numbers refer to bryozoan genera listed in Table 6. ab m—XD “th lllllllll Illjlllllllll 1 420 N 220 OXHBZ p ‘8’ Figure 43 - R-mode subordinal plot of RA axes 2 v. 4 with all grades and rare genera omitted. N=Halloporina, R=Rhabdomesina, C=Ceramoporina, P=Ptilodictyina. Numbers refer to bryozoan genera listed in Table 6. 112 Q-mode (sample by sample) data illustrate gradients stratigraphically and geographically. None of the DCA or RA axes with all grades included show any linear dependence with time. Crosstabulation of the gradient scores indicates that some of the axes do, however, show significant correlations with taphonomic grade and diversity. DCA axes 1 and 2 with all genera included show a significant correlation with taphonomic grade (at the 96% level). Since taphonomic grade delineates cycles in the Kope (as discussed above), these axes also illustrate stratigraphic cyclicity. The correlation with taphonomic grade decreases in significance when rare genera are downweighted or omitted, with the most significant correlation occurring with DCA axis 1 with rare genera omitted (at the 87% level). None of the RA axes showed significant correlations with taphonomic grade. The correlation of DCA axis 1 with the Brillouin log base 2 diversity index is even more significant (at the 99% level) than that for taphonomic grade. The significance of correlations again decreases as rare genera are downweighted or omitted, with the most significant correlation occurring iwith DCA axis 1 with rare genera omitted (at the 88% level). None of the other DCA or RA axes showed any significant correlations with diversity. Stratigraphic plots of DCA axis 1 and 2 ordination 'scores (Figures 44-46) show consistent patterns between sections. Second order curves represent original ordination 113 Figure 44 - Q—mode stratigraphic plot of smoothed DCA axis 1 for all five measured sections. Smoothing was performed using a simple moving average.Reference line (dashed) is at 140 for all sections. Horizontal lines are suggested correlation lines between sections based on kicks. 111+ DCMflfilLENWTH I'n'll '|"llll Figure 44 115 scores (Figures 45, 46). First order curves are smoothed using an equally weighted moving average of points in a time series. The robustness of DCA can be seen by the overlap in the curves from sections 1 and 5. This overlap is between beds which occur at the top of section 1 and in the base of section 5 (approximately 200 yards away), but have similar ordination scores (Figures 45 and 65). Second order (unsmoothed) curves show numerous prominent kicks or bulges which are correlated to other sections. For example, the curve for the section 1 and 5 composite (Figure 45) when compared to the section 2 curve shows nine well correlated kicks shown by horizontal lines (isocenes - lines of relative ordination score). The overall pattern for this curve, which is significantly correlated with diversity (discussed above), can be seen when the ordination scores are smoothed (Figure 44). Note how the curves for section 1 & 5 and section 2 parallel each other, as do the curves for sections 3 and 4. Scores are higher in the lower and upper Kope with a gradual decrease in the middle Kope, suggesting that high diversity is associated with high DCA first axis ordination scores (Figure 68). Similar high ordination scores occur stratigraphically higher in section 4 than in sections 1 or 2, which suggests the low diversity zone (deeper water) may have occurred somewhat later to the northwest. However, section 4 does not ‘ extend stratigraphically downward enough to fully evaluate this idea. Figure 45 116 Q-mode (second order) stratigraphic plot of DCA axis 1 with all grades included. Values plotted are actual ordination scores. Reference line (dashed) is at 140 for all sections. Horizontal lines are suggested correlation lines between sections based on kicks. 117 I. I II A 3 Pi. Pleas-M Figure 45 Figure 46 118 Q-mode stratigraphic plot (second order) of DCA axis 2 with all grades included. Values plotted are actual ordination scores. Reference line (dashed) is at 120 for all sections. Horizontal lines are suggested correlations between sections based on kicks. 119 Pt Pleasant Figure 46 120 Second order stratigraphic plots of the second DCA axis qumelated with taphonomic grade, discussed above) also show numerous well correlated kicks between sections (Figure 46). Somewhat higher ordination scores occur in the middle Kope where taphonomic grade is, on the average, higher. This suggests that higher ordination scores occur in higher grade beds and lower scores in lower grade beds. Large storm events which would affect a widespread geographic area should manifest themselves in high kicks (to the right) in nearby stratigraphic sections in Figure 46. A high kick occurs between 15 and 20 meters in section 1 and in section 2 which are approximately 8.8 km (5.5 miles) apart, well within the range of influence of modern hurricanes (Ball et a1., 1967; Perkins and Enos, 1968). Less severe winter storms would not be expected to result in very widespread event beds of a similar high grade because of rapid attenuation of energy away from the storm center. Thus, ordination scores would decrease away from the storm center so that a high kick near the storm center may be correlated with a kick in the opposite direction in a distant section. As expected, the value of discontinuity (D) is less for the DCA axes than it is for the RA axes (Table 7), indicating that DCA axes are more continuous than RA axes. The high values of D for the RA axes are the result of clustering of data points. Although the first DCA and RA waxes ordinate samples and genera identically, the values of D are much higher (less continuous) for the first RA axis. 121 Table 7 Discontinuity (D) of RA and DCA axes Axis A11 Genera Downweighting Omission DCA 1 All 55.6 54.5 54.9 DCA 2 All 35.7 56.6 55.8 RA 1 All 77.8 74.2 75.8 RA 2 All 73.7 71.9 72.4 DCA 1 1-3 55.1 53.2 52.8 DCA 2 1-3 40.9 54.7 54.4 RA 1 1-3 84.1 78.6 79.3 RA 2 1-3 71.8 67.1 67.0 DCA 2 3-6 6‘03 6005 6402 RA 1 3-6 80.1 85.5 86.8 RA 2 3-6 83.5 75.7 99.6 122 This is the result of the tendency of reciprocal averaging to compress axis ends relative to the axis middle making the axis less continuous, a problem eliminated in DCA (Hill, 1979). The effects of downweighting and omitting rare genera on the value of D are not generally to decrease the value of D (make the axes more continuous) except in the second DCA axis which shows the opposite pattern. Results With Taphonomic Grades 1-3 Only In this section, bryozoan generic data from beds which have a taphonomic grade of 4 or higher were eliminated from the data matrix and then run again with DECORANA. The R-mode plots of some of the DCA and RA axes show a distinct zonation of the growth habit fields. A plot of DCA axes 1 vs. 2 with all genera included (Figure 47) shows that axis 2 ordinates from encrusters to ramose forms, with bilaminate forms occupying a central position. The plots of DCA with downweighting and RA with all genera and downweighting show no distinct patterns. With the rare genera omitted, the DCA first axis (Figure 48) and RA second axis (Figure 49) show a segregation of the growth fields with ramose forms on the left, bilaminate forms in the central region and encrusters to the right. Thus, omission of the rare genera shifts the axis correlated with growth form from DCA axis 2 (Figure 47) to the more significant (in terms of eigenvalues) DCA axis 1 (Figure 48). Plots of DCA axes 1 vs. 2 with only grades 1-3 included 123 440 : 340 "E “340 ’5 ’1‘ :1 2 -.=. Llll D o. 8 01081 Figure 47 - R—mode growth habit plot of DCA axes 1 vs. 2 with grade 1-3 beds only. Hehemispherical, R=ramose, B=bi1aminate, E=encrusting. Numbers refer to bryozoan genera listed in Table 6. ‘m I I I 1 ' 1 —r I I 1 I y .- 1 37° '2 I Q 270 .9 l -_ 2 :70 R 1 O . 2 3 , 15 '8 .__. 7° 7 12 : -m 7 1 1 1 1 J I 1 1 1 1 l 1 1 1 1 1 -4O 60 i60 260 360 Figure 48 - R-mode growth habit plot of DCA axes 1 vs. 2 with grade 1-3 beds only and rare generaomitted. R=ramose, B=bilaminate, E=encrusting. Numbers refer to bryozoan genera listed in Table 6. 124 I I1 1". UT—l 1.1 I I '1.IVIIVVIU § § '1 l L A l 1 l I l l l l 1 LI 1 l l m_ 1 1 1 '-250 -50 so 150 250 ' 1x132 g lillllllllllllllllllll ith 9 - R-mode rowth habit plot of RA axes 2 vs. 4 w Figure 4 grade 2-3- beds only and rare genera omitted. B=bilaminate, R=ramose, Eaencrusting. Numbers refer to bryozoan genera listed in Table 6. 3 21‘ '1 3H) AXN31 Figure 50 - R-mode size plot of DCA axes 1 vs. 2 with grade 1-3 beds only and rare genera omitted. T=thick, N=medium, Th=thin, VTh=very thin. Size divisions are shown in Figure 36. Numbers refer to bryozoan genera listed in Table 6. 125 (Figure 47) show similar patterns to the same plot with all taphonomic grades included (Figure 37, discussed above). Stigmatella (21) and Eridotrypa (13) again plot near each other, and the hollow ramose ceramoporids and bilaminate taxa form distinct clusters (Figure 47). The plot of DCA axes 1 vs. 2 with all taphonomic grades and rare genera omitted (Figure 38) when compared to the plot of DCA axes 1 vs. 2 with taphonomic grades 1-3 and rare genera omitted (Figure 48) also show very similar patterns. Plots of bryozoan size indicate that none of the DCA or RA axes with taphonomic grades 1-3 and all genera included or with rare genera downweighted (not illustrated) show any interpretable patterns, as was the case with all grades and all genera included (discussed above). Only VHHNI rare species are omitted does any type of pattern emerge. Figure 50 shows that DCA axis 1 ordinates from thick forms to the left and thin forms to the right with the very thin forms occupying the central portion of the plot. Crosstabulation indicates that this correlation with size is significant at the 89% level (contingency coefficient = 0.94). This is the same pattern seen for DCA axis 1 with all taphonomic grades included and rare genera omitted (Figure 40). Subordinal membership plots again show that all DCA and RA axes with all genera included and with rare genera downweighted (not illustrated) are uninterpretable. When rare genera are omitted, DCA axis 2 (Figure 51) ordinates from Halloporina to the left and Ptilodictyina to the right. 126 R X g 170 3 7 70 I. -m A -30 Figure 51 a S: 52’ 3 '5 - R—mode subordinal plot of DCA axes 2 vs. 3 with grade 1-3 beds only and rare genera omitted. H=Halloporina, R=Rhabdomesina, C=Ceramoporina, P=Ftilodictyina. Numbers refer to bryozoan genera listed in Table 6. 127 This is the same pattern seen in Figure 42 with all taphonomic grades included. A comparison of the two plots shows that the rhabdomesine Arthrostylus (3) is placed within the Halloporina field near Dekayia (12) when only grades 1-3 are considered (Figure 51). The stratigraphic range charts for bryozoan genera in the Kope (Figures 28-31) illustrate that the Dekayia zone is confined to the upper Kope, and, as discussed above, Arthrostylus increases in f abundance upward in the section to reach its zenith in the Dekayia zone. This suggests that when taphonomic factors are eliminated from the data, more meaningful stratigraphic relationships may emerge. None of the Q-mode DCA or RA axes show any significant correlations with time. Crosstabulation of the gradient scores indicates that some of the axes do, however, show significant correlations with taphonomic grade. The most statistically significant correlation with Brillouin diversity index occurs with the first DCA axis with rare genera downweighted. Crosstabulation shows that this correlation is significant at the 99% level (contingency coefficient = 0.90). The first DCA axis with all genera included is somewhat less significantly correlated (significance - 89%), and with rare genera omitted the significance decreases to the 75% level. The third DCA axis, with rare genera omitted, also showed a significant correlation with diversity (significance = 98%, contingency coefficient = 0.88). None of the other DCA axes 128 showed a significant correlation with diversity. The first RA axis with rare genera downweighted shows a significant correlation with diversity at the 91% level (contingency coefficient = .90), but it is not as significant as the DCA result (discussed above). The first RA axis with all genera included is not significant (as it is in the DCA first axis), but the second RA axis shows a significant correlation at the 93% level (contingency coefficient = 0.89). This is a good example of how the quadratic dependency (arch effect) of the second RA axis on the first can sometimes result in better resolution of a first axis gradient (Hill, 1973, 1974; Gauch et a1., 1977). Since diversity is arched downward, so that diversity is higher in the bottoms and tops of sections and lower in the middle, the second RA axis may arch the middle upward resulting in a net straightening of the gradient. The second RA axis with rare genera omitted also shows a significant correlation with diversity (significance = 94%). None of the other RA axes are significantly correlated with diversity. The correlation of DCA axes with taphonomic grade is very weak. The most significant correlations occur with the third DCA axis with all genera included (significance = 78%) and with the second DCA axis with rare genera omitted (significance = 74%). The other DCA axes were even less significantly correlated with grade. The most significant correlation with taphonomic grade occurs with the third RA axis with all genera included 129 (significance = 89%, contingency coefficient = 0.79). With rare genera omitted, the significance decreases to 75%. None of the other RA axes showed any significant Correlations with grade. Stratigraphic plots of DCA and RA axes (Figures 52-54) again show consistent patterns between sections. It should be noted that all the taphonomic grade 4-6 beds have been eliminated from the data so some curves will start stratigraphically higher and/or finish stratigraphically lower when compared to the curves with all grades included (Figures 44-46). This elimination of beds also accounts for the gap between the base of section 5 and the top of section 1. Since taphonomic grade 1-3 beds are more distal and have been affected by storms only slightly (bringing about a community’s demise but not significantly biasing its final composition through size sorting), these curves should km: excellent indicators of biological diversity changes but poor indicators of intense storm events. A striking similarity occurs between section 1 and 2 in the overall trend of DCA axis 1 with rare genera down- weighted (correlated with diversity, Figure 52). There is a gradual increase in ordination score to the lower middle Kope, then a gradual decrease in scores to near the top of section 5 where scores increase slightly. Note how well the gradual decrease in section 1 is taken up by section 5 at almost the same ordination score. If higher ordination Figure 52 130 - Q-mode stratigraphic plot of DCA axis 1 (smoothed) with grade 1-3 beds only and rare genera downweighted. Smoothing was performed using simple moving average. Reference line (dashed) is at 140 for all sections. Horizontal lines are suggested correlation lines between sections based on kicks. ~ 131 ‘ DCADN1-3_SMTH 1&5 Pt. PIC-uni Figure 52 132 scores are equated with higher diversity (as suggested above), then diversity is low to about 5 m from the base, increases to about 22 m from the base, then gradually decreases almost to the top of the section. Since diversity seems in) parallel changes in sea-level suggested by other authors (discussed above), these curves (Figures 52-53) can 1N3 viewed as sea-level curves with shallower water to the right and deeper water to the left. The smoothed curve (Figure 52), when averaged over all five sections, provides an overall sea-level curve for the Kope (Figure 68). Thus, a ditonic bathymetric pattern emerges with shallower waters in the lower Kope, gradually increasing in depth to the lower- middle Kope, then gradually decreasing again to the Kope- Fairview contact. The curve for section 4 (Figure 52) shows the same general trend of decreasing ordination score upwards. Although the section 3 curve (Figure 52) shows an increase in ordination score upwards, the scale for that curve is quite low (80-140) so that ordination scores are comparable to the section 5 and 4 ordination scores. This curve is illustrating finer scale changes in diversity and bathymetry in the upper Kope. Second order DCA first axis curves (Figure 53) show consistent patterns between sections, though the number of kicks is decreased because of elimination of beds resulting in EH1 artificial "smoothing" of the curves. The third section curve is quite erratic because of the low number of higher grade beds in that section. 133 Figure 53 - Q-mode stratigraphic plot of DCA axis 1 (second order) with grade 1-3 beds only and rare genera downweighted. Values plotted are actual ordination scores. Reference line (dashed) is at 160 for all sections. Horizontal lines are suggested correlations between sections based on kicks. 134 I‘m EXQAHJV143 Pi. Pleeeeni Figure 53 135 The stratigraphic plots for RA axis 3 (correlated with taphonomic grade, Figure 54) with taphonomic grade 1-3 beds show parallel patterns between neighboring sections. The curves for sections 1 and 2 (Figure 54) show a consistent pattern of kicks at 12 m, 18 m, and 26 m from the base. The (nuves for sections 3 and 4 (Figure 54) show a parallel trend of increasing ordination score upwards. These curves are nearly the inverse of curves for the second DCA axis with all grades included (Figure 46). Higher taphonomic grade beds have lower ordination scores than do lower grade beds. Elimination of the higher grade beds reveals a strong low taphonomic grade gradient in the data which RA extracted with the lowest grade (1 and 2) beds at the positive pole and highest grade beds (3) at the negative. Since low grade more distal type beds are somewhat insensitive to all but the most severe storms, correlation of storm events is probably not possible. Instead, correlations exist only in the form of broad and gradual changes in ordination scores between sections. Patterns of discontinuity (D) with taphonomic grades 1- 3 are consistent with the patterns seen with all grades included. Table 7 shows that the continuity of DCA and RA axes generally increases (D decreases) as the rare genera are downweighted and then omitted. DCA axis 2 shows the opposite pattern, however. The RA axes are less continuous (D is larger) than the DCA axes because of the clustering of points with RA (discussed above). The first RA axis is again 136 Figure 54 - Q-mode stratigraphic plot of RA axis 3 (second- order) with grade 1-3 beds only. Values plotted are actual ordination scores. Reference line (dashed) is at 0 for all sections. Horizontal lines are suggested correlation lines between sections based on kicks. 137 I‘m RA3143 :1: Pi. ems-m Figure 54 138 less significant than the first DCA axis. Results With Taphonomic Grades 3-6 Only R-mode DCA and RA axes with bryozoan generic abundance data from taphonomic grade 3-6 beds plotted against each other produce unsatisfactory results for most growth habit fields. Fields are sinuous and stretched out, and overlap in places. Even when rare speCies are omitted, most of the fields are elongate. For comparison purposes, plots of DCA axes 1 vs. 2 for all genera (Figure 55), rare genera downweighted (Figure 56), and rare genera omitted (Figure 57) are included. The bryozoan colony size fields are also elongate and overlapping in most cases. An exception is DCA axis 2 which ordinates, in general, from thick forms in the lower portion to very thin forms in the upper portion of the plot (Figure 58). Axes with all taphonomic grades and grades 1-3 did not show any significant correlations until rare genera were omitted. Though the ordination shows a high degree of elongation and "curling" of size fields upwards at their ends so that they jut into other size fields, the overall pattern of size differentiation is still evident. In taphonomic grade 4-6 beds, the degree of sorting is usually quite high. As a result, fragment size is a dominant factor in these beds. It is not surprising, therefore, that the DCA second axis ordinates on size with all genera (Figure 58; significancer== 62%, contingency coefficient = 0.79), rare m Vfir I I I I T I I I I I I I I I—r T I l I—I I I 300 ' —-Z —J i 3 : g aa>+—L q " 1 2 I 100 Z.- I F : e 1 o flk1 l4 1 1 1 l 1 1 1 1 l 1 1 1 1 1 1 1 L 1 - -30 70 170 270 370 470 AXIS 1 Figure 55 - R-mode growth habit plot of DCA axes 1 vs. 2 with grade 3-6 beds only. H=hemispherical, R=ramose, B=bilaminate, E=encrusting. Numbers refer to bryozoan genera listed in Table 6. .6. “ 1 3°- 1' 380 Figure 56 - R-mode growth habit plot of DCA axes 1 vs. 2 with grade 3-6 beds only and rare genera downweighted. R=ramose, H=hemispherical, B=bilaminate, E=encrusting. Numbers refer to bryozoan genera listed in Table 6. g illjlllll 1x151 Figure 57 - R-mode growth habit plot of DCA axes 1 vs. 2 with grade 3-6 beds only and rare genera omitted. R=ramose, ‘ B=bilaminate, Eaencrusting. Numbers refer to bryozoan genera listed in Table 6. lllll ‘— [Ill [ll Ill Ill o7 1r11_111f111—1{111111111 -30 70 170 270 370 470 ”(131 Figure 58 - R-mode size plot of DCA axes 1 vs. 2 with grade' 3-6 beds only. T=thick, M=medium, Th=thin, VTh=very thin. Size divisions are shown in Figure 36. Numbers refer to bryozoan genera listed in Table 6. 141 genera downweighted (Figure 59; significance = 73%, (xxuingency coefficient = 0.96) and rare genera omitted (Figure 60; significance = 92%, correlation coefficient = 0.88). RA plots do not show any interpretable patterns until rare species are downweighted or omitted in which case the RA second axis ordinates on size. This second RA axis must always be suspect, however, so it will not be discussed further. ' Plots of bryozoan subordinal membership (Figures 61-63) show that DCA axis 2 ordinates from halloporines to rhabdomesines with ptilodictyines and ceramoporines in the center. As in the size plots, the second DCA axis ordinates on subordinal membership with all genera, and with rare genera downweighted or omitted. Recall that interpretable patterns for subordinal membership did not emerge until rare genera were omitted with all taphonomic grades and with grades 1-3 only (Figures 42, 43 and 50, respectively). Comparison of the subordinal (Figures 61-63) and size plots (Figure 58-60) for taphonomic grade 3-6 beds illustrates a relationship between size and suborder. The halloporines are generally restricted to the thick to medium portion of the size plots. The rhabdomesines and ptilodictyines are restricted to the thin to very thin portion of the size plots. The ceramoporines, though in the very thin to thin portion of the subordinal plot, show up as thick to medium in the size plot. This is not unexpected since the three ceramoporine genera present in the Rope d ~ _ all .— - u—J ‘ - — - j — AXIS 1 Figure 59 - R-mode size plot of DCA axes 1 vs. 2 with grade .mb U I T W I—U T l I l U j I, T T I I T I 400 E- 300 E— .. I I —( zoo -— :1 100 -E 1 l 1 1 1 1 1 1 1 1 1.— 340 3—6 beds only and rare genera downweighted. T=thick, M=medium, Th=thin, VTh=very thin. Size divisions are shown in Figure 36. Numbers refer. to bryozoan genera listed in Table 6. 0- . a -60 40 140 240 AXIS 1 Figure 60 — R-mode size plot of DCA axes 1 vs. 2 with grade 3-6 beds with rare genera omitted. T=thick, M=medium, Th=thin, VTh=very thin. Size divisions are shown in Figure 36. Numbers refer to bryozoan genera listed in Table 6. U m—XD _ 1 0 mo 200 2 300 400. ms 2, Figure 61 - R—mode subordinal plot of DCA axes 2 vs. 3 with grades 3-6 beds only. AaAmplexoporina, H=Halloporina, P=Ptilodictyina, C=Ceramoporina, R=Rhabdomesina. Numbers refer to bryozoan genera listed in Table 6. SIB 0 500 400 9‘” F: a 2200 12 ' 18 , H ' i7 0 i 7 1 1 l 1 : 1 1 I 1 ~20 so :90 AXIS i Figure 62 - R-mode subordinal plot of DCA axis 1 vs. 2 with grade 3-6 beds only and rare genera downweighted. A=Amp1exoporina, H=Halloporina, P=Ptilodictyina, C=Ceramoporina, R=Rhabdomesina. Numbers refer to bryozoan genera listed in Table 6. 144 WA U V r U I r ‘- 400 w“ . 19 : 9‘” d" 1 '12 , E 2 200 -— . 3 mo ’5 _j . . 1? NUSJI Figure 63 - R-mode subordinal plot of DCA axes 1 vs. 2 with: grade 3-6 beds only and rare genera omitted.v H=Halloporina, P=Ptilodictyina, C=Ceramoporina,f R=Rhabdomesina. Numbers refer to bryozoan genera' listed in Table 6. 145 (Ceramophylla, Ceramoporella, and Crepipora) are hollow ramose forms which are light and could have easily been picked up and carried by currents. Thus their hydrodynamic behavior is much like the thinner forms. In summary, the R-mode DCA and RA ordination techniques using taphonomic grade 3-6 beds show a strong tendency tx> extract taphonomically controlled gradients, such as bryozoan fragment size (and the related subordinal membership), but do a poor job of extracting non- taphonomically controlled gradients, such as growth form. In the Q-mode analysis, none of the RA or DCA axes showed any significant linear relationship vfiJfli time. Crosstabulation indicates strong correlation with the Brillouin diversity index and weak correlation with taphonomic grade. The DCA first axes with all genera, rare genera downweighted and with rare genera omitted all show significant correlations with the Brillouin diversity index, the highest significance occuring with rare genera omitted. The significance levels and contingency coefficients (respectively) are as follows: all genera - 97%, 0.90; rare genera downweighted - 92%, 0.90; and rare genera omitted- 99%, 0.90. The first RA axis with all genera included showed a significant correlation with diversity at the 91% level (contingency coefficient = 0.90). With rare genera omitted, the significance of the first RA axis correlations increases to 96% (contingency coefficient = 0.89). 146 Some of the third RA and DCA axes also show significant correlations with diversity. The third DCA axis with all genera included has a significance of 92% (contingency coefficient = 0.88), and with rare genera omitted the significance increases to 98% (contingency coefficient = 0.89). The third RA axis with all genera is significant at the 95% level (contingency Coefficient = 0.90). None of the DCA or RA second axes showed any significant correlation with diversity. As shown in Table 5 (discussed above), diversity is inversely related to taphonomic grade. As in the case of bryozoan colony size, RA and DCA are both ordinating strongly on taphonomically-induced gradients when diversity data from grade 3-6 beds are used for the analysis. A strong diversity gradient is present with grades 3-6 beds because of an almost linear inverse relationship between grade and diversity. Only one axis (the third DCA axis with rare species downweighted) shows any significant correlation with taphonomic grade (significance = 93%, contingency coefficient = 0.84). This is the result of the strong taphonomically imposed diversity gradient present in high grade beds. The correlation with grade occurs with one of the third DCA axes that does not have a significant correlation with diversity. Stratigraphic patterns for RA and DCA ordination scores with data from grade 3-6 beds are shown in Figures 64-66. 147 Diversityq (Nl'the average, decreases as taphonomic grade increases (Table 5). High grade beds are formed by moderate to high intensity storm events which, if strong enough, should affect large geographic areas. The dependence of diversity on grade and grade on storm events should provide an optimum detailed correlation between sections in both the DCA grade and diversity dependent curves. Since diversity is dependent on grade, the diversity dependent first DCA axis (Figures 64-65) is biased and does not represent stratigraphic trends in biologic diversity. A comparison of Figure 64 with Figures 44 and 52 (all grades and grades 1-3, respectively) shows a mirror image diversity trend when only grades 3-6 are included in the data (Figure 64). Ordination scores are low in the lower high diversity zone, high in the low middle low diversity zone (shown in section 4) and decrease in the upper high diversity zone to the Fairview. Since the stratigraphic curves can be plotted with a reversed scale (which direction the poles are plotted does not matter, as long as the order of samples between poles is not changed), the curves with all grades (Figures 44-45), grades 1-3 (Figures 54-55) and grades 3-6 actually show the same patterns. The inverse relationship between taphonomic grade and diversity is especially strong in grades 3-6 (Table 5). Thus a strong diversity gradient is imposed on the data and DCA extracts it, revealing a parallel pattern to that seen in the all grades and grades 1-3 curves. Figure 64 148 - Q-mode stratigraphic plot of DCA axis 1 (smoothed) with grade 3-6 beds only and rare (genera omitted. Smoothing was performed using a simple moving average. Reference line is an: 180 for all sections. Horizontal lines are suggested correlation lines between sections based on kicks. 149 DCHUHEK334BSNHTI .1} Pt. Pleasant ”‘1“ 1‘8 Figure 64 150 Second order curves of the diversity dependent DCA first axis with rare genera omitted (Figure 65) show correlation of sharp kicks between neighboring sections which are interpreted as storm event beds. There are about 6 well correlated kicks between sections 1 and 2, and a correlated kick in the overlapping section 1 and 5 beds. The sparseness of high grade beds in section 3 results in an artificial smoothing, but 3 well correlated kicks can be seen when compared to section 4. Comparison of areas of overlap between three curves (sections 1, 2 and 4 and sections 5, 3 and 4; Figure 65) also show correlated kicks indicating that some very severe storm events may deposit ‘widespread beds which act as isochrons for correlation of sections up to at least 39 km (24.5 miles) apart. The third DCA axis with rare genera downweighted and grades 3-6 only (Figure 66) is significantly correlated with grade (discussed above). There is a direct relatnnmhip between taphonomic grade and ordination score so that higher ordination scores indicate higher grade. This is the same relationship noted for the DCA second axis with all grades included (Figure 46) but Opposite the RA third axis with grades 1-3 only (Figure 54). The correlation of kicks between sections is not as strong as in the DCA first axis, but correlations do exist. The correlations appear stratigraphically offset slightly up or down, especially when distant sections are compared. The discontinuity (D) of ordination axes with bryozoan Figure 65 151 Q-mode stratigraphic plot of DCA axis 1 (second order) with grade 3-6 beds only and rare genera omitted. Values plotted are actual ordination scores. Reference line is at 120 for all sections. Horizontal lines are suggested correlation lines between sections based on kicks. 152 DCAIRGO 3' 6 m 115 Pt. Pleasant ‘Figure 65 153 Figure 66 - Q-mode stratigraphic plot of DCA axis 3 (second- order) with grade 3-6 beds only and rare genera downweighted. Values plotted are actual ordination scores. Reference line is at 140 for all sections. Horizontal lines are suggested correlation lines between sections based on kicks. 154 4 [KHVHIN343 no Ar Id. 128 Pt. Pleeeent Figure 66 155 abundance data from grade 3-6 beds is shown in Table 7. As in the case with all grades and grades 1-3, the values of D for the DCA axes is less (more continuous) than that for the RA axes. Also consistent with previous observations is the fact that the first DCA axis D is less than (more continuous) the value for the first RA axis, even though the two ordinate samples and genera the same (discussed above). Not consistent with previous observations with data from all grade and grade 1-3 beds is the fact that, in grade 3-6 beds, downweighting and omission of rare genera makes time axes less continuous (increasing D) rather than more continuous. The rare genera only are found in grade 1-3 beds where the diversity and abundance of bryozoans is higher and thus the chance of finding them is higher. The higher grade beds segregate the bryozoans into colonies or fragments of colonies with similar hydrodynamic properties so the chance decreasing the importance of the least dominant genera (these genera are considered rare within a bed, but not rare within the Kope Formation) which may increase D slightly since diversity is low in these beds to begin with. In the lower grade beds, diversity is much higher so the effect of downweighting is to improve the ordination by lessening the tendency to place rare genera at the poles of axes. Omitting the rare genera that occur in grade 3 beds has the same effect as downweighting when considering the RA and DCA 156 results with grade 3-6 bryozoan data. Discussion and Summary The similarity between the DCA diversity dependent first axes with all grades included, grades 1-3, and the inverse of the curve with grades 3-6 only (Figure 67) suggests the following: 1) the high proportion (2/3) of low taphonomic grade beds in the Kope results in a nearly identical ordinations between curves with grades 1-3 and all grades included; and, 2) the strong inverse relationship between taphonomic grade and bryozoan diversity index results in nearly identical ordinations between the grade 3- 6, 1-3 and all grades DCA first axes, and may play a part in the similarity between the all grades and grades 1-3 DCA first axes. This has implications for other studies: 1) if the prOportion of high taphonomic grade beds is high (>1/3), ordination patterns may be altered from the true patterns; and 2) if a strong inverse relationship exists between taphonomic grade and a variable that can be measured within the particular data used, then ordination patterns of axes dependent on that variable will be nearly the same with all taphonomic grade beds included or with the high grade beds taken out of the data matrix. These implications illustrate the importance of taphonomically grading rocks when performing ordination studies. Anstey et al. (1987a) note that the first RA axis using bryozoan species diversity is the most likely candidate for 157 a bathymetrically controlled gradient (Figure 67 and 34). This curve shows the same ditonic pattern as do the sea- level curves of Sweet (1979) generated from the relative proportion of the bathymetrically sensitive conodont Phragmodus. The same pattern of a gradual increase in ordination score to the middle Kope, then a gradual decrease followed by an increase to the Fairview (lower Dillsboro) is seen in the diversity dependent DCA first axes with all tapmmumfic grades included (Figures 44 and 45) and with grades 1nfi3 only (Figures 52 and 63) with bryozoan generic abundance data (Figure 67). Therefore, these axes are most likely bathymetrically controlled and provide second-order sea-level curves for the Kope Formation. The first DCA axis with grades 3-6 only shows a mirror image pattern when compared to the DCA first axis with all grades and grades 1- 3 only (Figure 67). The overall sea-level curve for the Kope Formation (Figure 68), derived by averaging together smoothed DCA axis 1 curves with grades 1-3 only (Figure 52), shows two regressive and one transgressive event. The base of the Kope has the highest ordination score and thus is the shallowest part of the section, continuing the trend from the shallow Point Pleasant beds less than a meter below. The lower shallow (high diversity) zone extends from the base of the Kope to about 24 m above the base and is interrupted twice by short transgressive events at 3 and 14 m. From 24 m above the base to 34 m is a gradual transgressive event which 158 Figure 67 - Stratigraphic plots of cmdination scores from Anstey et al. (1987a) and this study, as well as the Phragmodus undatus sea-level curve of Sweet (1979). From left to right: RAl-PA= first RA presence-absence; POl= first polar ordination axis; RAl-SD= first RA species diversity axis; RAZ-PA= second RA presence-absence axis; Phragmodus= Phragmodus undatus (bathymetrically sensitive conodont) abundance (sea-level) curve; DCAlDNl-3= first DCA axis with rare genera downweighted and grade 1-3 beds only; DCAl-All= first DCA axis with all taphonomic grades included; DCAlRGO3-6= first DCA axis with rare genera omitted and grade 3-6 beds only. The first five curves are in the Moffett Road section (northern Kentucky) and have scales from 50 at the left to 100% to the right (rescaled). The last three curves have scales from 80 to 320, 60 to 340 and 0 to 240, respectively. 159 942098 WOO 11V'WOO c—mowoo NW smnmfififiud va-zyu OS- WEI IOd Pt. Pleasant Figure 67 ‘ va-wu .‘. 60 45 30 15 160 Figure 68 - Sea-level curve for the Kope Formation in the study area. Constructed by averaging the smoothed DCA first (diversity dependent) axis with grades 1-3 over all five sections. Lower ordination scores are inferred to represent deeper waters and are correlated with low bryozoan generic diversity. Higher ordination scores are inferred to represent shallower water and are correlated with high bryozoan generic diversity. 161 so a a 40 30 20 10 Deepening _ . II 2 Figure 68 162 reaches a maximum at 34 m. A regression begins at 44 m above the base and continues through the uppermost Kope into the shallower water Fairview. The average Brillouin diversity index for bryozoan genera in the low diversity zone is 1.4, in the lower high diversity zone 1.5, and in the upper high diversity zone 1.7. Anstey and Perry (1973) also found high bryozoan diversity zones in the lower and upper Kope and a low diversity zone in the middle Kope. They note that the higher diversity zones represent shallower waters and the low diversity zone deeper waters based on the general decrease in taxonomic diversity of bryozoans associated with increasing water depth noted by Schopf (1969). This vertical sequence of changes is also paralled by the following: 1) a higher proportion of limestone le‘the upper and lower Kope and less limestone in the middle; 2) higher taphonomic grade in the lower (average == 3.5) and upper (average = 3.2) Kope than in the middle Kope (average = 3.0 - higher taphonomic grades would be expected in shallower waters); 3) an upward increase in the flexible, jointed bryozoan Arthrostylus (adapted to shallow, high energy environments Schopf, 1969 ) from the middle Kope the the Kope-Fairview boundary; 4) an upward increase in the abundance of Dekayia from the upper-middle Kope into the Fairview in response to shallowing waters (discussed above); and, 5) the gradual shift from a more onshore Rafinesquina- Zygospira community in the Point Pleasant and lower Kope to 163 a more offshore Onniella-Sowerbyella community in the middle Kope, then replacement upwards by the Rafinesquina-Zygospira community giving a sea-level curve that parallels Figure 68 (MacDaniel, 1976). The sea-level curve proposed in this study is similar to the curves of Sweet (1979, Figure 34), and the RAl-SD and mean bathymetric curves of Anstey et al. (1987a, Figure 34). In summary, taphonomic grading provides a useful method for classifying fossiliferous limestones which are subject to differential environmental energies (especially storms). It allows the investigator to approach facies analysis in a :more quantitative manner and makes it easier to interpret otherwise unapparent trends in the data than more cumbersome descriptive nonquantitative methods. Taphonomy effects the ordinations provided by gradient analysis techniques and should not be ignored by investigators if a high proportion of the rocks in question show any appreciable taphonomic affects. If so, taphonomic grading provides a technique for separating out higher grade units. Almost two-thirds of the Kope limestones are of low grade (1-3) so the ordinations with all grades included showed very much the same pattern as ordinations with grades 1-3 only. The almost linear inverse relationship between bryozoan generic diversity and grade imposes a strong diversity gradient which parallels the diversity patterns seen in DCA first axes with all grades and grade 1-3 only. With only high grade beds included, R-mode plots illustrate the effects CHE size 164 sorting of bryozoan genera. Gradient analysis using bryozoan generic abundance data in the Kope Formation provides bathymetrically controlled stratigraphic plots and therefore sea-level curves. These stratigraphic curves have some utility in providing correlations between sections. 165 CONCLUSIONS l) The Kope Formation is a storm-dominated offshore deposit. 97% of the Kope limestones have been affected to some degree by storms, though bioclasts in nearly two-thirds of the beds show no significant transport. 2) Original (non-taphonomically overprinted) Kope communities were mainly bryozoan-brachiopod dominated. Bryozoan communities are intergradational along a continuum, with a Parvohallgpora-Ceramophylla-Stigmatella community in the lower Kope, a Parvohallopora-Heterotrypa-Ceramophylla community in the middle Kope, and a Parvohallopora- Batostoma-Ceramophylla dominated community in the upper Kope. 2) Taphonomic grading, a method of classifying fossiliferous limestones based on their biostratinomic properties, provides £1 quantitative approach to facies analysis which makes trends in the data more apparent than in more cumbersome descriptive non-quantitative methods. Grading also illustrates energy relationships (proximalitqr‘trends) between beds and defines carbonate-Clastic cycles. 3) Taphonomy affects the ordinations provided by gradient analysis techniques. Including high grade beds in the data alters the ordinations compared to data with only low grades included except for variables correlated with taphonomic grade. These variables (diversity, in this case) show very similar ordinations with all grades, grades 1-3 only and grades 3-6 only included in the data. 166 4) Gradient analysis using bryozoan generic abundance data in the Kope Formation provides bathymetrically controlled stratigraphic plots and therefore sea-level (coeno- correlation) curves. An overall sea-level curve for the Kope shows a relatively shallow water zone from the base of the Kope to about 35 m above the base, with a gradual transgression from 26 m to 35m, deeper waters from 35 m to 45 m, and a gradual shallowing from 45 m to the Kope- Fairview contact. This curve is consistent with trends in bryozoan generic diversity, taphonomic grade, limestone/ shale ratios and bryozoan growth form, as well as published sea-level curves. 5) Second-order coenocorrelation curves allow detailed correlations between geographically widespread Kope sections based on consistent trends in ordination score. LIST OF REFERENCES List of References Aigner, T., 1982, Calcareous tempestites: storm-dominated stratification in Upper Muschelkalk limestones (Triassic, southwest Germany), in Einsele, G. and Seilacher, A., eds., Cyclic and Event Stratification: Berlin, Springer-Verlag, p. 180-198. Aigner, T., 1985. Storm Depositional Systems: Dynamic Stratigraphy in Modern and Ancient Shallow Marine Sequences: Berlin, Springer-Verlag, l74pp. Aigner, T., and Reineck, H.E., 1982, Proximality trends in modern storm sands from Helgoland Bight (North Sea) and their implications for basin analysis: Senck. Marit. v. 14, p. 183-215. 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Askren, L.T., 1968, Bryozoan paleoecology from the Tertiary of Alabama: Southeastern Geology, v. 9, p. 157-163. Ball, M.H., Shinn, E.A. and Stockman, K.W., 1963, Geologic record of hurricanes: American Association of Petroleum Geologists Bulletin, v. 47, p. 349. Bassarab, D.R. and Huff, W.D., 1969, Clay mineralogy of Kope and Fairview Formations (Cincinnatian) in the Cincinnati area: Journal of Sedimentary Petrology, v. 39, p. 1014- 1022. Bird, J.M, and Dewey, J.F., 1970, Lithosphere plate- continental margin tectonics and the evolution of the Appalachian Orogen: Geological Society of America Bulletin, v. 81, p. 1031-1060. Brandt, D.S., 1980, Phenotypic variation in paleoecology of Flexicalymene (Arthropoda Trilobita) in the Cincinnatian Series (Upper Ordovician) near Cincinnati, Ohio. Unpub. M.S. Thesis, Univ. of Cincinnati, Cincinnati, Ohio. Bray, J.R. and Curtis, J.T., 1957, An ordination of the upland forest communities of southern Wisconsin: Ecological Monograph, v. 27, p. 325-349. Bretsky, P.W., 1969, Central Appalachian Late Ordovician communities: Geological Society of America Bulletin, v. 80, p. 193-212. Brett, C.E. and Baird, G.C., 1986, Comparitive taphonomy: a key to paleoenvironmental interpretation based on fossil preservation: Palaios, v. 1, p. 207-227. Brown, G.P. and Iineback, J.A., 1966, Lithostratigraphy of the Cincinnatian Series (Upper Ordovician) in southeastern Indiana: American Association of Petroleum Geologists Bulletin, v. 50, p. 1018-1023. 169 Bucher, W.H., 1917. Large current ripples as indicators of paleogeography: Proceedings of the 0.8. National Museum, v. 3, p. 285-291. Bucherq IN.H., 1919, On ripples and related sedimentary surface forms and their paleogeographic interpretation: American Journal of Science, v. 47, p. 149-219. 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