Upper Vindhyan Sedimej^Tation in the Kota-Rawatbhata Area, Rajasthan
Total Page：16
File Type：pdf, Size：1020Kb
UPPER VINDHYAN SEDIMEJ^TATION IN THE KOTA-RAWATBHATA AREA, RAJASTHAN By Bisheshwar Dayal Bhardwaj M. Sc. (Aligarh) THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY IN GEOLOGY AT THE ALIGARH MUSLIM UNIVERSITY, ALIGARH 1970 T928 CONTENTS INTRODIK:TION ... ... I Purpose of study ... ... 1 Location and environs of the area ... -2 Scope of work ... ... 3 Acknowledgements ... ... 4 CHAPTER I - GEOLOGY OF THE AREA ... 5 Previous work ... ... 5 Stratlgraphic nomenclature and classification 7 Gross lithology and field characters ... 10 Kaimur sandstone 10 Bewa group 13 Bhander group 16 Laterite 19 Structure of the area 20 CHAPTER II - SEDIMENTARY STRUCTURES ... 21 Directional structures ... ... 22 Cross-stratification ... 22 Ripple marks ... ... 28 Parting lineation ... ... 31 Sole markings ... ... 32 Non-directional structures ... 36 Load structures ... ... 36 Flow rolls ... ... 37 Organosediraentary structures ... 38 Algal stromatolites ... ... 38 Doubtful organic structures ... 41 - i - - ii - CHAPTER III - PETROGRAPHY 42 Methods of study 42 Grain size analysis 42 Roundness of grains 43 Shape of grains 44 Modal composition 44 Heavy mineral separation 45 A. Non-glauconitic sandstones 45 Textures 45 Composition ... ... 56 Heavy minerals 68 B. Glauconitic sandstones ... 75 General remarks ... 75 Textures 75 Composition ... 77 C. Limestones ... ... 81 Interlarainated calcilutite and calcisiltite 82 Flat-pebble calcirudite breccia 83 Massive limestone 85 Insoluble residues 86 CHAPTER IV - PAUEOCURHENT ANALYSIS ... 89 Cross-stratification ... ... 89 Methods -of-raeasurement 89 Sampling ... ... -90- Variability of cross-stratification foreset dip azimuths 91 Linear current structures ... 98 Ripple marks ... ... 98 Parting lineation ... ... 100 Apposition fabric ... ... 102 General remarks ... ... 102 Fabric anisotropy and palaeocurrent directions 103 Methodology ... ... 104 Statistical analysis of grain fabric data 105 Palaeocurrent reconstruction ... 109 - iii - CHAPTER V - PROVENANCE 114 Introduction 114 Composition of provenance 115 Sedimentary rocks 115 Metamorphic roclcs 116 Basic igneous rocks .. 119 Granitic rocks 120 Composition & distribution of pre-Vindhyan rocks 121 Location of provenance ... 124 CHAPTER VI - SEDIMENTATION HISTORY AND DIAGENESIS 126 Sedimentation history 126 General remarks 126 Physical and geomorphic conditions of deposition 127 Tectonic framework of sedimentation ... 147 Diagenesis 151 Genera 1 remarks ... ... 151 Silica cementation 153 Glauconitisation 156 CHAPTER VII - CONCLUSIONS 162 REFERENCES 168 APPENDIX I - Cross-stratification foreset dip azimuths, inclinations and thicknesses in "Upper" Vindhyan sandstones i APPEMDIX II - Data of ripple marks in "l^per" Vindhyan rocks xxi APPENDIX III - Thin section size frequency distribution (per cent) of "Upper" Vindhyan sandstones xxvi APPENDIX IV - Size frequency percentile and parameters of "C^per" Vindhyan sandstones xxx APPENDIX V - Roundness data of detrital grains in "Upper" Vindhyan sandstones xxxv - iv - APPENDIX VI - Grouped data of elongation (length/breadth) ratio of detrital grains of "Upper" Vindhyan sandstones XXXVii APPENDIX VII - Heavy minerals of "t^per" Vindhyan sandstones xxxviii APPENDIX VIII- Insoluble residues of Bhander limestone 30Li APPENDIX IX - Parting lineation in "l^per" Vindhyan sandstones xLii APPENDIX X - Azirauthal distribution of grain long-axes in "l^per" Vindhyan sandstones in thin sections parallel to bedding xLiii APPENDIX XI - Inclination of grain long-axes in "l^per" Vindhyan sandstones in thin sections perpen- dicular to bedding and parallel to grain orientation xLv - V - LIST OF PLATES Facing page PLATE I 11 Figs, 1-3 Field photographs of Kaimur sandstone. Figs. 4-6 Field photographs df Rewa shale PLATE II 15 Figs. 1-6 Field photographs of Rewa sandstone PUTE III 17 Figs. 1-3 Field photographs of Bhander limestone Figs. 4-5 Field photographs of Bhander sandstone Fig. 6 Field photograph of a fold in Bhander limestone PLATE IV • • • • • • 24 Figs. 1-4 Field photographs showing cross-stratifi- cation. Figs. 5-6 Field photographs showing ripple marks. PLATE V * • • • • • 32 Figs, 1-2 Photogtaphs showing parting lineation. Figs. 3-4 Photographs showing flute casts. Fig. 5 Photographs showing groove cast, prod cast and bounce cast. Fig. 6 Photograph showing groove cast. PUTE VI • • • • • • 37 Figs. 1-4 Photographs showing load structures. Figs. 5-6 Photographs showing algal structures. Fig. 7 Photograph showing doubtful organic structures. PLATE VII • « • • • • 55 Figs. 1-4 Photoittjicrographs of thin sections of sandstones showing nature of grain contacts. - vi - PLATE VIII 62 Figs. 1-4 Photomicrographs of thin sections of sandstones showing nature of secondary overgrowths. PLATE IX 66 Figs. 1-3 Photomicrographs of thin sections of sandstones showing nature of cements. Fig. 4 Outcrop of Bhander sandstone showing replacement relationship of cements. PLATES X - XII 71 Photomicrographs of heavy mineral grains (1/8 - 1/16 mm grade). PLATE XIII 78 Figs. 1-6 Photomicrographs of thinsections of glauconitic sandstones. PUTE XIV • • • • • • 83 Fig. 1 Photomicrograph of interlaminated calei rudi t e-calei s i Iti te. Fig. 2 Photograph of a slab of calcirudite breccia. Fig. 3 Photomicrograph of thin section of calci- rudite breccia. Fig. 4 Photograph of a polished specimen of cal- cirudite breccia. Fig. 5 Photomicrograph of thin section of cal- cirudite breccia. Fig. 6 Photomicrograph of massive limestone. - vil - LIST OF FIGORES Following page FIGURE 1 Flowsheet showing the plan and methodology of the present investigation FIGURE 2 Geological map of Kota-Rawatbhata area, Rajasthan, showing sample localities (Cover Packet) FIGURE 3 Stratigraphic sections of the "C^per" Vindhyan formations in the Kota-Rawatbhata area 9 FIGURE 4 Histograms showing frequency distribution of cross-stratification inclinations 26 FIGURE 5 Cumulative curves showing mechanical composition of Kaimur sandstone 45 FIGURE 6 Cummulative curves showing mechanical composition of Rewa sandstone 45 FIGURE 7 Cummulative curves showing mechanical composition of Bhander sandstone 45 FIGURE 8 Histograms showing mechanical composition of non- glauconitic sandstones 46 FIGURE 9 Histograms showing roundness characteristics of detrital grains in sandstones 52 FIGtKE 10 Elongation distributions of quartz grains from Kaimur, Rewa, and Bhander sandstones (a-c) com- pared with data in. Bokman (1952) (d-f) 53 FIGURE 11 Average mineral composition of non-glauconitic sandstones 56 FIGURE 12 Part of sandstone classification according to Folk (1954) showing composition of Kaimur, Rewa, and Bhander sandstones 57 FIGURE 13 Histograms showing mechanical composition of glauconitic sandstones 75 FIGtBE 14 Cumulative curves showing mechanical composition of glauconitic sandstones 76 - viii - Following page FIGURE 15 Distribution of cross-stratification dip azimuths in the study area (in cover pocket) FIGURE 16 Palaeocurrent map showing azimuths of linear structures 98 FIGURE 17 Grain fabric of "Upper" Vindhyan sandstones in thin sections parallel to preferred grain orien- tation and perpendicular to bedding 108 FIGURE 18 Summary diagrams of directional sedimentary structures in the "l^per" Vindhyan sediments Facing page 111 FIGURE 19 Sketch map showing the present day distribution of outcrops of Vindhyan and pre-Vindhyan rocks east of the study area Following page 121 - ix - LIST OF TABLES TABLE 1 Informal classification of Vindhyan rocks in the Kota-Rawatbhata area 9 TABLE 2 Grain size characteristics of non-glauconitic sandstones 48 TABLE 3 Roundness characteristics of detrital grains in non- glauconitic sandstones 52 TABLE 4 Volumetric modal composition of sandstones 58-61 TABLE 5 Heavy minerals of non-glauconitic sandstones 70 TABLE 6 Statistical parameters of size frequency distri- bution of glauconitic sandstones 77 TABLE 7 Mineral composition (per cent by volume) of the glauconitic sandstones 79 TABLE 8 Distribution of insoluble residues in Bhander limestones 86 TABLE 9 Vector mean (9^), vector magnitude (L %), standard deviation (<r ) and variance ($2) of cross-strati- fication dip azimuths 92-95 TABLE 10 Grain orientation data of thin sections parallel to bedding 106-107 TABLE 11 Grain imbrication data of thin sections perpen- dicular to bedding and parallel to preferred grain orientation 110 TABLE 12 Sedimentary characteristics and depositional environ- ments of Kaimur sandstone. 130 TABLE 13 Sedimentary characteristics and depositional environ- ments of Rewa group. 135 TABLE 14 Sedimentary characteristics and depositional environ- ments of Bhander group. 139 INTRODUCTION Purpose of Study The thick sequence of Vindhyan sediments (? Late Precambrian) f has been a subject matter of keen geological interest ever!since it attracted the attention of the Indian Geological Survey in 1854. From that time onwards a great deal of work has been done on these interest- ing rocks, but in view of the enormity of the Vindhyan basin, much more work is still needed before any attanpt is made to answer many of the intriguing questions concerning its mode of formation and palaeogeography. The Vindhyan rocks offer excellent opportunities for studying ancient sedimentary processes and products. Perhaps they present one of the very few cases of unmetamorphosed and undeformed sequences of a very ancient age which contain within them such a wide spectrum of lithological characters and sedimentary structures, and were deposited under so varied