CLAY MINERALOGY AND SEDIMENTARY PETROGRAPHY OF LOWER TO MIDDLE PALEOZOIC ROCKS FROM A SINGLE CORE FORM NORTHWEST GEORGIA A THESIS Presented to The Faculty of the Division of Graduate Studies by Ali Ihsan Gevrek In Partial Fulfillment of the Requirements for the Degree Master of Science in the School of Geophysical Science Georgia Institute of Technology August, 1978 MINERALOGY AND SEDIMENTARY PETROGRAPHY LOWER TO MIDDLE PALEOZOIC ROCKS FROM A SINGLE CORE FROM NORTHWEST GEORGIA Approved: CharlefE. Weaver, Chairman Kevin C. Beck Charles 0. Poiiara, Jr. Date approved by Chairman: ii ACKNOWLEDGMENTS I would like to sincerely thank Dr. Charles E. Weaver, my major director, for his guidance, advice, and for pro­ viding me with the thesis subject. I greatly appreciate Drs. Charles 0. Pollard, Jr., and Kevin C. Beck for being on the reading committee and for their fruitful criticisms. Thanks are also extended to Drs. John E. Husted and Howard R. Cramer for their suggestions on the Lower Paleozoic Appalachian problems. The Georgia Geological Survey is to be thanked for providing me the core. A number of people helped me in this work. Dianne Clark encouraged me and Annette Plunkett typed this thesis; special thanks go to them. Brad Broekstra, Robert J. Bullwinkel, and Rick Griffin helped by carrying the core boxes and correcting English grammar; special thanks to them. Finally, thanks to my father, Ismail Gevrek, and my mother, Meryem Gevrek, for their moral support. This research was supported by Government of the Turkish Republic. iii TABLE OF CONTENTS Page ACKNOWLEDGMENTS . ii LIST OF TABLES iv LIST OF PLATES vi LIST OF ILLUSTRATIONS vii SUMMARY viii Chapter I. INTRODUCTION . 1 Geologic Setting Depositional Environments of Formations in the Core II. METHODS AND PROCEDURES 10 III. RESULTS AND DISCUSSION 11 Sedimentary Structures Distribution of Sedimentary Structures in the Formations Mottled Matter in Formations Sedimentary Petrography Distribution of Clay Minerals in the Core IV. CONCLUSION 6 6 APPENDIX I. PREPARATION OF ORIENTED, FLAT-LAYERED SPECI­ MENS 6 8 II. PREPARATION OF RANDOM POWDER PACKS SPECIMENS . 7 0 III. IDENTIFICATION OF CLAY MINERALS WITH ORIENTED, FLAT-LAYER SPECIMEN 71 IV. CALCULATION OF CLAY PERCENTAGE 73 BIBLIOGRAPHY 74 iv LIST OF TABLES Table Page 1. Observed Stratigraphic Units in the Core .... 4 2. Stratigraphy of the Core 5 3. Sedimentary Structures in the Core 12 4. Distribution of Clay Mineral Percentages According to the Lithology and Depth 30 5. Illite Sharpness Ratio According to the Formations 32 6. Illite Crystallinity Index Distributions According to the Formations 3 2 7. Distribution of 2M Percentage 35 8. Observed Thin Section Samples in the Core ... 39 9. Grain Size and Degree of Roundness of Quartz Grains in the Observed Thin Sections 40 10. Data Sheet for the Thin Section Description of a Sample From the Floyd Shale Formation .... 41 11. Data Sheet for the Thin Section Description of a Sample From the Chattanooga Shale Formation . 4 2 12. Data Sheet for the Thin Section Description of a Sample From the Red Mountain Formation .... 43 13. Data Sheet for the Thin Section Description of a Sample From the Red Mountain Formation .... 48 14. Data Sheet for the Thin Section Description of a Sample From the Sequatchie Formation ..... 50 15. Data Sheet for the Thin Section Description of a Sample From Sequatchie Formation 51 16. Data Sheet for the Thin Section Description of a Sample From the Carters Formation 53 17. Data Sheet for the Thin Section Description of a Sample From the Lebanon Limestone Formation . 55 V Table Page 18. Data Sheet for the Thin Section Description of a Sample From the Ridley Formation 59 19. Data Sheet for the Thin Section Description of a Sample From the Pond Spring Formation .... 62 20. Data Sheet for the Thin Section Description of a Sample From the Knox Group 6 3 21. Data Sheet for the Thin Section Description of a Sample From the Knox Group 65 LIST OF PLATES Plate Page 1. Lenticular Bedding with Connected Thick Lenses and Lenticular Bedding with Isolated Lenses in the Floyd Shale Formation ........... 13 2. Wavy Bedding in the Floyd Shale Formation ... 14 3. Load Cast in the Chattanooga Shale Formation . 16 4. Interlayered Shale and Fine-Grained Sandstone Beds in the Chattanooga Shale Formation .... 17 5. Graded Bedding in the Red Mountain Formation . 18 6. Graded Bedding in the Red Mountain Formation . 19 7. Graded Bedding in the Red Mountain Formation ,. 21 8. Ptygmatopic Sandstone Dikes in the Red Mountain Formation 22 9. Trace Fossils in the Red Mountain Formation . 24 10. Interlayered Shale and Fine-Grained Sandstone Bedding in the Sequatchie Formation 25 11. Stylolites in the Limestone Bed of Knox Group . 26 12. Interlayered Calcareous Mudstone Bedding and Calcisiltite Bedding in the Ridley Formation . 27 13. Sedimentary Boudinage in the Pond Spring Forma­ tion 28 vii LIST OF ILLUSTRATIONS Figure Page 1. Index Map of Georgia Showing Location of Floyd County and of the Studied Core 2 2. Lithologic Log of the Core 6 3. Distribution of Clay Minerals in the Sedimen­ tary Environment 34 4. Curve for Determination of Percent 2M Dioctahedral Mica 3 6 5. Siderite Inclusions in Quartz From Sample No. 19 44 6. Microcrystalline Quartz Grains in Limonite Cement From Sample 19 4 5 7. Secondary Quartz Overgrowths From Sample No. 23 49 8. Angular and Subangular Quartz Grains in the Silt-Shale Bed of the Sequatchie Formation . 52 9. Quartzitic Calcarenite From Sample No. 45 . 54 10. Bryozoon Fossil in the Lebanon Limestone From Sample No. 47 56 11. Trilobite Fossil in the Lebanon Limestone From Sample No. 47 57 12. Brachioped Fragments in the Lebanon Limestone From Sample No. 4 7 5 8 13. Dolomite Rhombs in Hemetitic Cement From Sample No. 4 8 6 0 14. Dolomite Rhombs in Hematitic Cement From Sample No. 48 61 15. Stylolite in Microcrystalline Calcite Ooze From Sample No. 51 64 viii SUMMARY A single core from Floyd County, Georgia, 2000 feet long and four inches in diameter, was analyzed for its clay minerals and sedimentary petrography. The column of rocks represented ranges from the Knox Group through the Floyd shale. The following results were found. 1. Illite and iron-rich chlorite were the most abundant clay minerals, and a major amount of kaolinite was pre­ sent only in a portion of the Red Mountain formation. Illite and iron-rich chlorite were allogenetic, but kaolinite was authigenic. 2M illite type of mica poly­ morph was present throughout the core but the lMd type was dominant. 2. Illite percentages showed little relation to depositional environment. Iron-rich chlorite percentages remained fairly constant throughout the core. The illite sharp­ ness ratio diminished with increasing depth and was lower in rocks from nonmarine environments than in those from marine environments. The illite crystallinity index remained fairly constant throughout the core. 3. Megascopic sedimentary structures from the core were described. Lenticular bedding with connected thick lenses, lenticular bedding with isolated lenses, wavy bedding, graded bedding, trace fossils, sedimentary boudinage ix sandstone dikes, and load casts were found. Petrographic studies of the core indicated that the Floyd shale was deposited as a fine-grained arqillaceous mud. hematite in the Red Mountain formation was postdeposi- tional. A high degree of pressure solution was observed in the Red Mountain formation. Siderite cement was pre­ sent in the Red Mountain formation, and dolomite cement was present in the Sequatchie formation. These carbonate cements occurred as secondary pore-filling without any replacement of grains. The Lebanon Limestone formation was fossiliferous. The Ridley formation was dolomitic. The Pond Spring formation was intraclastic. The lime­ stone bed of the Knox Group was nonfossiliferous. 1 CHAPTER I INTRODUCTION The purpose of this study was to determine the distri­ bution of the various clay minerals and the sedimentary petrography of a single core, 2000 feet long and four inches in diameter, taken from Floyd County, Georgia. The Lower Paleozoic section and sedimentary environments of Northwest Georgia had been investigated by field observations (Butts and Gildersleeve, 1948; Milici and Smith, 1969; Chcwns, 1972). Weaver (1958) had given the X-ray diffraction analyses of clay minerals for the solution of geological problems concerning Upper Mississippian-Lower Pennslyvanian sediments of Central United States. In his work, the distribution of the clay mineral suites are discussed in terms of the sedimentary environments. The method of his research was considered to be effective and therefore applied to study the sample core taken from Floyd County, Georgia (Figure 1). In addition to the X-ray analyses, seventeen thin sections of the core were observed under a petrographic microscope to obtain petro- graphic information. Geologic Setting The area in which the well was drilled was mapped and described by Butts and Gildersleeve (1948). Detailed investi- Miles £ Drilled Area Figure 1. Index Map of Georgia Showing Location of Floyd County and of the Studied Core (Map is from Cressler, 1970). 3 tion have been reported by Milici and Smith (1969), Cressler (1970), Nunan (1970), and Chowns (1972). The author used the interpretation of Milici and Smith (1969) for stratigraphy and Chowns (1972) for sedimentary environments. With this writer's knowledge, it is impossible to determine true stratigraphic thicknesses, and relationships for the following reasons: 1. The sedimentary rocks in the core was heavily deformed. 2. One would need several more cores to make three-dimensional correlations. 3. Some parts of the core were not available. Description of Formations in the Core The comparison of the lithologic well log data of the researched core with field observations of Milici and Smith (1969), and Chowns (1972) was used to identify the stratigraphic units of the investigated core. These descriptions are seen to be in agreement with Weaver (personal communication), and are listed in Table 1 and Table 2.