February, 2021

SEDIMENTOLOGICAL STUDY OF LOKAPUR SEQUENCE OF KALADGI BASIN, KARNATAKA, INDIA

A THESIS SUBMITTED TO GOA UNIVERSITY

FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY IN GEOLOGY

by PURUSHOTTAM ANIL VERLEKAR

Under the Guidance of

Dr. Mahender Kotha School of Earth, Ocean and Atmospheric Sciences Goa University

SCHOOL OF EARTH, OCEAN AND ATMOSPHERIC SCIENCES GOA UNIVERSITY

FEBRUARY, 2021

This thesis is dedicated to

Grandmother

Smt. Shantabai Shantaram Rivonkar

CERTIFICATE

This is to certify that the thesis titled, “Sedimentological study of Lokapur sequence of Kaladgi Basin, Karnataka, India” submitted by Purushottam Anil Verlekar for the award of degree of Doctor of Philosophy in Geology is a record of research work done by him during the period of study and is based on the results of experiments carried out by him independently. The thesis or a part thereof has not previously formed the basis for the award to the research scholar for any other degree, diploma, associate ship, fellowship or other similar titles.

RESEARCH GUIDE

Dr. Mahender Kotha Professor, School of Earth Ocean and Atmospheric Sciences Goa University, Taleigao Plateau, Goa

STATEMENT

I hereby state that this thesis titled, “Sedimentological study of Lokapur sequence of Kaladgi Basin, Karnataka, India” for the award of Ph.D. degree is my original contribution and that the thesis or any part thereof has not previously formed the basis for the award of any other degree, diploma or other similar titles of any university or institute. To the best of my knowledge, the present study is the first comprehensive study of its kind from the study area. The literature pertaining to the investigated problem has been duly acknowledged. Facilities availed from other sources have also been duly acknowledged.

RESEARCH SCHOLAR

Mr. Purushottam Anil Verlekar,

School of Earth Ocean and Atmospheric Sciences

Goa University, Taleigao Plateau, Goa.

ACKNOWLEDGEMENT

I am deeply obliged and thankful to my supervisor Prof. Mahender Kotha for his continued support throughout this work. His unshaken belief in me has brought this thesis to the present stage

This thesis would not have got completed without the constructive and critical inputs of my VC’s nominee Dr. J. N. Pattan.

My sincere thanks to Dr. A. A. Viegas for his constant motivation and encouragement in completing the scholarly work.

A special word of gratitude to the three Deans, during whose tenure this work was undertaken. Prof. A. V. Salkar and Prof. Gourish Naik of Faculty of Natural Sciences, Goa University and Prof. H. B. Menon, Dean of School of Earth Ocean and Atmospheric Science.

I thank my soulmate Gargi, who was pillar of strength. She doubled up as my field companion, her editing enriched the work and her science background became an added asset in writing the thesis.

I wish to thank Adv. Surel Tilve, Shantal Rivankar and Abhishek Pissurlekar for their kind logistical support.

It would have been not possible without support of my Uncles, Shashank Rivonkar, Nishant Rivonkar and Aunt Mrs. Nirmala Rivonkar, Mrs. Nehal Rivonkar for opening up their house to me and creating a serene atmosphere for me to complete this scholarly work.

I am Indebted to Dr. Aditya Joshi for his kind hospitality during my stay at Vadodara.

I acknowledge the Director, National Institute of Oceanography- Goa for providing XRD facilities and the Director, Regional Geoscience Lab-Vadodara for providing SEM facilities which has enhanced the quality of work.

I am grateful to Nageshwar, Dwayne, Lewlynn, Satu, Gopal, Omkar, Aliston and Chinmay for spending their time with me in the field.

I acknowledge the kind support and affection of Mr. Premanand Gauns, Mr. Devidas Gaude, Mrs. Sangita, Mr. Dynaneshwar and entire support staff of Earth Science Department, Goa University.

I thank My colleagues, Dr. Niyati Kalangutkar, Dr. Sohini Ganguly and Mr. Raghav Gadgil for their constant support and encouragement at all times during the tenure of this thesis.

I would like to thank My teacher Mr. Harish Nadkarni of Parvatibai Chowgule College for kindling the light which brought all frontiers of Geology to me.

My humble thanks to my dearest sister Priyanka and brother in law Chetan for always being there with me and gratitude to my in-laws Kalpana and Kantikumar Lotlikar for their steadfast support.

I remember the encouraging words of my uncle Late Mr. Manohar Verlekar as this thesis is completed.

I am eternally indebted to my parents Kanchan and Anil Verlekar for taking me from the cradle to this memorable journey

And finally, my deep reverence to Dambab for all blessings he showered upon me.

C O N T E N T S Chapter No Topics Page no

List of Figures iii List of Table vi Abstract 1

Chapter 1 INTRODUCTION 1.1 Foreword 4 1.2 Introduction 5 1.3 Aims and Objectives 6 1.4 Previous Work 6

Chapter 2 GEOLOGY AND STRATIGRAPHY 2.1 General 11 2.2 Stratigraphy of Kaladgi Supergroup 13 2.3 Study Area 21

Chapter 3 METHODOLOGY 3.1 Field work 36 3.2 Laboratory investigations 40 3.3 Scanning Electron Microscopy 41 3.4 X-Ray Diffraction 42

Chapter 4 CLASTIC SEDIMENTOLOGY 4.1 Introduction 46 4.2 Detrital mineral composition 46 4.2.1: Quartz 48 4.2.2: Lithic Fragments 49 4.2.3: Feldspars 50 4.2.4: Matrix and Cement 50 4.2.5: Clay minerals 51 4.2.6: Accessory minerals 51 4.3 Texture 52 4.3.1: Mean 54 4.3.2: Standard deviation 54 4.3.3: Inclusive graphic skewness 54 4.3.4: Inclusive graphic kurtosis 55 4.3.5: Textural maturity 55 4.4 Classification 56 4.5 Diagenesis 57

Chapter 5 CARBONATE PETROGRAPHY AND DIAGENESIS 5.1 Introduction 64 5.2 Fabric and Texture 65 5.3 Carbonate Petrography and classification 5.3.1: Micrites 66 5.3.2: Biomicrites 67 5.3.3: Algal laminated biomicrites 67

5.3.4: Dolomircites and sparites 67 5.4 Identification of Carbonate Minerals 5.4.1: X-ray diffraction analysis 68 5.4.2: Determination of Calcite – Dolomite ratio 70 5.4.3: Results 70 5.5 Geochemistry of Carbonate rocks 5.5.1: Analytical Methodology 71 5.5.2: Major and selected Minor elements 72 5.5.3: Other elements 75 5.5.4: Rare Earth Elements (REE) 75 5.6 Diagenesis 5.6.1: Diagenesis of Carbonate Units of Lokapur Subgroup 79 5.6.2: Compaction 80 5.6.3. Replacement 80

Chapter 6 PROVENANCE AND DEPOSITIONAL HISTORY 6.1 Introduction 93 6.2 Interpretations 93 6.3 Depositional Environments 95 6.4 Paleoclimate 99

Chapter 7 SUMMARY AND CONCLUSION 7.1 Summary 106 7.2 Conclusion 109

BIBLIOGRAPHY 112

List of Photos and Figures Figure Description Page No. 2.1. Geological Maps of study area Geological map of the Kaladgi Basin (after Jayaprakash et al., 26 1987; Dey et al., 2009). 2.2 Map showing Sample Location for Carbonate samples 27 (Mahender 2004)

2.3 a Symmetrical ripples with bifurcating crests 28 2.3 b Symmetrical ripples

2.4 Contact between basement and Mesoproterozoic rocks 29 2.5 Disoriented clasts floating in Conglomerate

2.6 Natural vegetation at Hooli 30 2.7 Conglomerate interlayered in Sandstone at Savadatti

2.8a Thickly bedded planar parallel beds (inclined) observed near 31 Ramdurg 2.8b Massive Sandstones devoid of any structure exposed near Savadatti 2.9a Deformed crystalline limestone at Lokapur 2.9b Widen joints in Limestone 32

2.10 Alternating bands of Carbonate and Shale 33 2.11 Bimodal grain size distribution seen at Munavalli

2.12 Trough cross bedding observed in stream cut section 34 2.13 Horizontally disposed beds of Shale

3.1 Techniques used for atmospheric SEM 44 3.2 TM-3000 table top SEM at RGL Vadodara 4.1 Ternary diagram for classification of Arenaceous rocks of 59 Saundatti Quartzite Member with matrix less than 15% (Pettijohn 1984, modified after Dott 1964)

4.2 Petrography of Clastic rocks 60 a. Clasts of Monocrystalline Quartz in moderately well sorted Arenite b. Grain of Polycrystalline composite Quartz seen in sample collected from Savadatti. c. Polycrystalline Schistose Quartz grain d. Grains of Lithic Fragments as seen sample from Hooli Village e. Grain of Plagioclase Feldspar seen forming framework constituent in one of the samples. f. Grains of Pressure Quartz seen as framework grains in sample collected from Savadatti 4.3 Accesory Minerals 61

iii

a. SEM image showing Intergranular spaces occupied by Kaolinite b. SEM image of Vermiform overgrowth of Kaolinite seen in Void spaces c. SEM image showing well developed crystal faces of Kaolinite e. Distinct greenish to yellow coloured specs of Chloritoids, note flowage around quartz grains f. Slender prismatic habit of Tourmaline grain

4.4 Diagenesis 62 a. Quartz overgrowth around detrital grains. b. PPL image of well sorted Arenite with brownish ferruginous cement c. Corroded grain boundaries filled by clay minerals precipitated secondary minerals d. Framework grains exhibiting Sutured contacts in Sample collected from Lokapur e. Long contact observed along with deformation fractures seen in Sample from Hooli Village f. Subrounded grains of Quartz making framework

5.1 Field Photographs of Stromatolites 84 a. Typical concentric to cylindrical shaped stromatolites exposed at ground level near Lokapur. b. Outcrops of Dolomitic limestone showing folded structure exposed in fields around Lokapur.

5.2 Types of Stromatolites 85 a. Algal Stromatolite bedding of dolomitic limestone exposed on the Lokapur to Petlur Road b. Pseudo Columnar Stromatolites showing both upward convex and concave lamination (Lokapur) c. Deformed stromatolite mat seen in Dolomitic limestone d. Stromatolite possibly of Conophyton Cylindricus e. Common stromatolitic structures

5.3 Photomicrographs-Carbonates 86 a. Finely crystalline micritic limestone. (Petlur Limestone Member) XN b. Fine to medium grained micritic limestone displaying unidentified organic particle (Bamanbudni Dolomite Member) XN c. Medium grained algal laminated limestone (Chiksellikeri L.st Member). XN d. Typical xenotopic mosaic of anhedral to subhedral replacement dolomite XN e. Subhedral Dolomitic limestone (dolomicrite) displaying replaced organic remain (Chitrabhanukot Dolomite Member) XN f. Micro crystalline Dolomite displaying generation of secondary porosity (Chitrabhanukot Dolomite Member) XN

5.4 Photomicrographs – XRD 87 5.5 Photomicrographs – XRD 88

5.6 Carbonate diagenesis 89 a. Compaction effects shown be tight packing of finely crystalline dolomite leading to facture development (Chitrabhanukot Dolomite). b. Neomorphism fine to sparry calcite and replacement of dolomite (Chitrabhanukot Dolomite). c. Replacement showing former fabric (Petlur Limestone) d. Dissloution and replacement textures (Chiksellikeri Limestone) e. Xenotopic Dolomite replacement and silification (Nagnur Dolomite) XN f. Pressure solution effect leading to stylolite formation (Nagnur Dolomite) XN

5.7 Distribution of trace elements 90

5.8 REE distribution chart 91

6.1 Triangular Diagrams 101 a. Tectonic setting discrimination diagram based on Qt-F-L after Dickinson and Suczek 1979 b. Qm-F-Lt ternary diagram after Dickinson et. al. 1983

6.2 Depositional Environment 102 a. Mean size versus standard deviation b. Mean size versus skewness c. Mean size versus mean roundness d. Mean roundness versus sorting e. Bivariant plot of skewness versus inclusive graphic standard deviation, after Friedman (1967).

6.3 Bivariate plots a. Bivariant plot of inclusive graphic standard deviation versus 103 mean diameter, after Stewart (1958) and Moiola and Weiser (1968) b. Bivariant plot of skewness versus mean size, after Stewart (1958), Friedman (1961) and Moiola and Weiser (1968). c. Bivariant plot of kurtosis vs. skewness, after Mason and Folk (1958) and Moiola and Weiser (1968). d. Bivariant plot of mean size versus inclusive graphic standard deviation, after Friedman (1961) and Moiola and Weiser (1968) 6.4 Palaeoclimate 104 The effect of source rock on the composition after Suttner et. al. 1981 Climatic discrimination diagram of Suttner and Dutta (1986).

List of Tables:

Table no. Description Page No. 2.1 Generalized Stratigraphy of Kaladgi-Badami (after 12 Jayaprakash 1987)

2.2 Two-fold classification of the Kaladgi Series by Bruce Foote 13 (1876)

3.1 Bearings of structures 38

4.1 Data of Modal analysis 47

4.2 Recalculated data of Modal Analysis 48

4.3 Detailed textural data of Clastic units 52

4.4 Textural data of Clastic units 53

5.1 Results of X-Ray diffraction analysis 69

5.2 Stratigraphic Distribution of Average values of Major Oxide 72 Components

5.3 Correlation coefficient matrix 83

5.4 Summary of stratigraphic Distribution of average values of 76 REE

ABSTRACT

The Kaladgi Basin, one of the important Proterozoic Sedimentary basins of Peninsular India, exposes a thick sequence of Proterozoic succession composed of a variety of lithologies with a predominance of arenaceous rocks interrupted with Carbonate sediments at different stratigraphic levels. The present work focuses mainly on understanding the Sedimentological nature and diagenetic character of the Lower part of the Lokapur subgroup rocks exposed in and around Savadatti Town, Belagavi District of Karnataka, and Carbonate succession overlying these clastic sequences. The clastic succession comprises lithologies, which include Sandstones with minor conglomeratic facies at the lower regimes.

The thesis is an account of work wherein an attempt is made to identify the detailed petrographic character of the sandstones and to understand the provenance and depositional environments based on the careful petrographic observation. Emphasis is also given to decipher characteristics of the overlying carbonate rock units of the sequence.

The study suggests that the coarse clastic conglomerates, which are the lowermost unit of the succession, are essentially polymictic. The sandstones are sub-mature to mature (mineralogically), medium to coarse-grained, and categorized mainly into Sublith arenites and Quartz arenites. The minor occurrence of feldspars has also been seen occurring as the framework constituent of these rocks. However, their variable degree of alteration (from fresh to partially altered to completely altered grains) associated with textural maturity and nature of Quartz point towards the possibility of the derivation of these sediments from two different sources. The clastic sequences show the preservation of various primary depositional features, including ripple marks and trough cross-bedding. Palaeocurrent data that indicate an NW palaeoslope. The mineral composition of these sediments suggests the derivation of these rocks from a variety of granitic and gneissic crystalline complexes occurring along the basin margin. The maturity of the sandstones (Quartz Arenites) is attributed to the recycling and re-working of the older sediments. Analysis of Textural parameters of these rocks pointed towards deposition under beach environments. The lack in the preservation of much amount of feldspar in these sandstones is indicating a remote source and relatively dry-arid climate of the source area. However, to decipher paleoclimatic conditions, data were plotted over standard triangular and bivariate plots. These plots concentrate mainly in the humid zone. However, the composition got further modified during transportation and subsequent sedimentation. Granulometric analysis of sandstone

samples have been carried out for their statistical and textural parameters. Bivariant plots of textural parameters such as graphic skewness versus graphic standard deviation and skewness versus standard deviation point towards fluvial processes and beach environment of deposit for these sediments.

Extensive Carbonate successions which cover the older Clastic sequences have been studied for their geological character. Five different litho units representing these sequences are critically examined and described in detail concerning their microfacies classification, depositional and diagenetic properties. The present carbonate samples are devoid of any carbonate allochemical constituents (except a few detrital quartz, feldspar, etc.). All these carbonate rocks were categorized as orthochemical carbonate rock types with variable mineralogy and texture. All limestones are generally hard and compact and often bedded in character and display a significant colour variation. These units are white, grey, and show variegated nature. The dolomites/dolomitic limestone are generally thin-bedded/nodular and buff, pale grey to dark grey, and often traversed by Quartz veins. Various types of stromatolitic structures are observed in these dolomitic rock units.

CHAPTER 1:

INTRODUCTION

1.1 Foreword

At the end of the Archaean Eon, middle to late Proterozoic saw extensive development of Intracratonic Basins on the continental shields worldwide (Windley 1997, Condie 1989). Filling of these basins led to the formation of extensive sedimentary strata resting unconformably over Archean–early Proterozoic gneisses, high-grade rocks, granite- greenstones of Cratonic shields or metasedimentaries of Proterozoic mobile belts. These less disturbed and unmetamorphosed Proterozoic sedimentary basins in peninsular India are also known as the Purana Basins in the Indian context. Peninsular India exposes seven of such Proterozoic basins shared by all the major cratonic blocks, including aerially vast basins like Vindhyan, Cuddapah and Chattisgarh basin to regional basins like Pranhita-Godavari, Bhima, Bastar and Kaladgi Basins (Kale and Phansalkar 1991). There exists a profound hiatus known as the great "Great Eparchean Unconformity," separating these cover sediments from the basement crystallines. Apart from that, Proterozoic was a critical time for the evolution of life and global bio-geo-chemical cycles. During this period, the Stromatolites were widespread, Eukaryotic cells developed and eventually, so did the multicellular organisms. The Proterozoic Kaladgi basin is one such basin developed over the Dharwar craton and lay exposed in the northern region of Karnataka state.

The sediments of Kaladgi Basin mark the northern and northeastern fringes of the Dharwar craton, in an area of roughly 8000 sq. Km. These sediments are deposited over the Archean basement rocks, which constitutes detritus of gneisses, metasediments, and granites and covered under the extensive Deccan flood basalts of the late Cretaceous age towards its northern margin. Stratigraphically, the lithological package of this basin is classified into two groups, which are separated by a prominent angular unconformity. Comparatively undeformed younger Badami Group and structurally deformed older Bagalkot Group. Bagalkot Group further represents two cycles of Sedimentation, namely Lokapur and Simikeri Subgroups separated by a disconformity.

1.2 Introduction

Various aspects of the Proterozoic Kaladgi basin have been studied by different authors, which includes its Biotic nature, Mineralogical composition, Structural aspects, and its economic potential. However, detailed investigations on Individual lithological units, mineralogical composition, facies variation is still lacking. The tectonic and geologic history of a region controls the source area characteristics and the depositional environment in which sediments accumulate (Boggs, 2009). This line of thinking led to the study of sediments from Kaladgi Basin so that updated information on these sediments at the Formation scale can be made available. This study involves the identification of depositional environment, diagenetic processes it has underwent and provenance of the sediments. Besides, an attempt has also been made to know the geochemical characteristic of carbonate units occurring in the sequence.

The lower part of Kaladgi Supergroup. i.e., Lokapur Subgroup of Bagalkot Group forms the domain of this study. The choice of study was primarily based on the work of previous researchers, followed by reconnaissance studies. A transition from coarse clastic to fine clastic facies with intermediate carbonate succession was identified. This sequence is made up of Basal Conglomerate and Arenites, making up the bulk of the Clastic component while Limestone and Dolomite constitute the non-clastic component. Field investigations were carried out around towns of Savadatti, Ramdurg, and Lokapur. The locations are well connected by road network and even accessible by Public transport. Other sampling areas are Hooli village and Munavalli town.

The present thesis entitled “Sedimentological study of Lokapur sequence of Kaladgi Basin, Karnataka, India” is an account of studies made to know the mineralogy, sedimentology, geochemistry, and diagenesis these rocks have undergone during the long period of their formation. Primary information was gathered based on the reference to previous work, which was available. Further extensive fieldwork was carried out at the prominent locations within the geographical extent of the basin. Traverses were taken at Ramdurg, Lokapur, Hooli, Munavalli, and Savadatti.

Detailed Sedimentological and Mineralogical analysis was done using thin sections prepared out of fresh rock samples collected from the field. SEM analysis was carried out to study microstructural details, study grain to grain relations, and identify clay minerals. Carbonate

mineralogy was studied using the X-Ray diffraction technique, and XRF was employed to know the geochemistry of the carbonate rocks. The data thus generated is analyzed, interpreted, and has been supported by field evidence.

The thesis comprises of altogether seven chapters excluding bibliography. Chapter -1 is an introductory chapter which gives an overview of the study area and research problem. Chapter 2 is an illustration of Geology and Stratigraphy of the area concerned. The details of various analytical methods adopted in the present study are given in Chapter 3, adopted for the said research work has been described. Chapters 4 and 5 form the core chapters of the thesis wherein Clastic rock units and non-clastic formations have been described respectively. Chapter 6 is dedicated to provenance studies and interpretation of sedimentation history. The final chapter provides a summary and conclusion of the present study.

1.3 Aims and Objectives

Aim

To study the sedimentological aspects of the Lokapur sequence of Kaladgi basin to draw depositional history, tectonic set up and provenance of these ancient sediments.

Objectives

• The primary objective of the present research proposal is to understand the Geochemical and mineralogical aspects of rocks of Proterozoic Kaldgi Basin belonging to Lokapur sequence.

• Further, it also aims to understand the depositional environments and sedimentation history of these sediments and the role of tectonics in the study area.

• Comparing the outcome with existing data on other Proterozoic basins to arrive at fruitful regional understanding.

1.4 Previous work

The earliest description of the sedimentary basin in the northern region of Karnataka is found in Foote's classic work (1876), where he described the stratigraphy of this entire basin following the earlier works by Christie, Newbold, and Carter. Foote systematically mapped these rocks and suggested for the first time, two-fold classification as, ‘Lower Kaladgi

Series’ and an ‘Upper Kaladgi Series.' Later on, different schemes of classification of 'Kaladgi Series' have been suggested by Pascoe (1949) and Krishnan (1949), Nautiyal (1966), Viswanathiah (1977), Jayaprakash et al. (1987). Nautiyal (1966) defined the Upper and Lower ‘Series’ of the Kaladgi basin as deposits of two separate, but overlapping basins. Based on tectonic and metamorphic cycles, Nautiyal (1966) has reclassified the rocks of the 'Kaladgi Series.' However, Viswanathiah (1964) established a new series of rocks based on field relations, termed as the 'Badami Series.' He brought out the unconformable relationship between the Lower Kaladgi Series and the Upper Kaladgi Series, as classified earlier.

Viswanathiah (1964) demonstrated that a distinct angular unconformity separates the sequence into a younger, Badami Group and the older Kaladgi Group. The first report of primitive life in the Proterozoic formations in Karnataka was in the form of large colonies termed "Stromatolitic bioforms" occurring in a limestone bed lower Kaladgis near Bagalkot (Viswanathaiah et al., 1964). Subsequent workers later reported such algal stromatolitic structures.

Govindarajulu and Chandrashekhara Gowda (1968, 1972) recognized several forms of algal stromatolites in the uppermost divisions of both upper and lower Kaladgi series and also from southwestern and central parts of the Kaladgi basin. They have discussed the paleoenvironmental conditions that prevailed during the growth of the stromatolites and the conspicuous absence of the cell structures in thin sections. Vishwanathaiah and Sreedhara Murty (1979) and Chandrashekhara Gowda and Govindrajulu (1980) observed algal stromatolitic colonies in variegated limestones of this basin. Depending upon the morphologic similarities, they have recognized different forms and discussed the paleoecological significance of the stromatolites.

The algal stromatolites are the only organic activity that has been reported from this basin. Pillai, 1997; Sharma et al., 1998; Kulkarni and Borkar, 1997, based on the Palaeobiological studies based on stromatolite biostratigraphy and ichnological evidence have restricted the age of these sediments to Mesoproterozoic.

Sharma and Pandey (2012) have attempted the systematic study of the stromatolites of the Proterozoic Kaladgi Basin. The diversity and distribution of the various stromatolite forms occurring in the Bagalkot Group of the Kaladgi Supergroup have been well documented in their work. An assemblage of six taxa is recognized from the Bagalkot Group.

The sediments of Kaladgi basin are considered to have been deposited within a narrow intracratonic rift basin by some workers (Radhakrishna and Vaidyanathan, 1997) whereas some workers assumed the basin to be mostly marine in origin (Viswanathaiah, 1969; Jayaprakash et al., 1987; Peshwa el al, 1989; Kale et al., 1996). On the premise of the availability of an insufficient data Miall et al., (2015); Dey (2015) in his report reiterates the need to carry out intensive investigations on the age of sedimentary detritus, the nature of the evolution of the basin as well as its geological and tectonic history. He opines this will provide immense knowledge to understand the evolution of this intracratonic basin, to reconstruct Proterozoic supercontinents and to study the atmospheric changes and primitive life forms.

The detailed palynological investigation carried out by Vishwanathaiah et al., (1984) on Salagundi conglomerate of Bagalkot Formation has revealed the rich assemblage of acritarch and other filamentous forms of blue-green algal affinity. They noticed that the Salagundi microbiota as a whole shows simplicity and considerable primitiveness compared to overlying Lokapur Formation.

Seismites or the Syn sedimentary deformation (SSD’s) structures have been reported in this basin (Patil Pillai 2011). These structures are prolific in the Proterozoic shallow marine sediments of the Kaladgi Basin. They are observed mainly in the basal in both clastics and carbonates part of the succession (Lokapur Subgroup). The study of the occurrence of intraformational breccias in impure limestones of the Chikshellikeri Limestone Member (Kale et al., 1998) was the first record of SSDs from the Mesoproterozoic Bagalkot Group of the Kaladgi Basin.

Ramachandran et al. 2015 have reported Geochemistry of Proterozoic clastic rocks of the Kerur Formation of Kaladgi-Badami Basin. Comparing REE patterns and Eu anomalies of the source rocks reveal that the Kerur Formation it is concluded that the clastic rocks in this formation received a significant contribution of sediments from the Dharwar Craton.

The basal Salgundi Conglomerates are recently studied as terrestrial scree products formed along the margins of the basin and fan deposits that graded downslope to form braided sediments (Bose et al., 2008). The authors conclude that the tectonic influence on the gradient of the marginal slope of the basin controlled the sedimentary package's nature and a subsequent build-up of the sequence.

3D GIS technique has been attempted in the Proterozoic sedimentary Kaladgi Basin by Shivanna et al. 2011. In this study, the three-dimensional geological models based on a logical model by surface-mesh, wire-mesh and TIN in 3D GIS is applied to decipher the old marine terrain surface of the study area of the Kaladgi Basin using extensive database involving about 20,522 point elevations and a few kilometers of line elevation contours.

Three-dimensional facies variability studies were made by Bose et al. 2008 in coarse clastic sedimentary rocks (breccia, conglomerates, and coarse-grained sandstones) at the base of the Ramdurg Formation suggests terrestrial scree and fans giving way downslope to fluvial sediments along the margin of the Mesoproterozoic Bagalkot basin. Confined between an unconformity below and a granular lag succeeded by thoroughly wave-featured sandstone, and argillite-carbonate above, the coarse and poorly sorted clastic sedimentary rocks of the basal Ramdurg are interpreted as a base-level low stand product, for which the sedimentation rate exceeded the rate of space creation for sediment accumulation.

The recent work by Sukanta Dey et al. (2008a, 2008b, 2009, 2015) discusses the geochemical composition of shales of the Proterozoic Sequence of Kaladgi-Badami Basin for understanding the palaeoweathering and evolution of Dharwar Craton. They suggest the deposition within the basin to comprise a cyclic arenite-pelite-carbonate association resting unconformably over the Archean basement.

Mukherjee et al. 2016 brought to light that in the northern margin of the Kaladgi Basin, the Saundatti Quartzite and the Salgundi Conglomerate Members directly rests over the granites. The sedimentary cover rocks are stated to be mildly deformed in this part of the region, and a homocline has developed with intervening normal faults, but no cleavage development.

Devli and Mahender 2018 have reported paleocurrent, Deformation, and Geochemical studies of the Lower part of the Bagalkot Group of Kaladgi Basin. Their work suggests that the deposition has occurred along with marginal parts of the basin with a proximity to the source area. The source from which the constituents were drawn must have been originally a mafic igneous rock, which was later metamorphosed. Hot, humid, and oxidizing conditions must have prevailed during the rock's depositional history that underwent low temperature (<3000 C) deformation.

CHAPTER 2;

GEOLOGY

AND

STRATIGRAPHY

2.1: General The Kaladgi Sedimentary Basin, one of the seven Purana basins of Peninsular India, confined between lattitudes 150 33’ to 160 31’ North and Longitudes 740 10’ to 760 East constitutes a thick sedimentary sequence of Proterozoic rocks, well exposed in parts of Vijayapura, Belagavi and Dharwad districts of Karnataka and Kolhapur and Sangli Districts of Maharashtra. The basin covers an area of 8,300 sq km (Fig. 2.1). The present configuration of the basin is irregular due to extensive overlapping flows of Deccan Trap to the north and west.

During the middle Proterozoic fundamental changes were set, which created large sedimentary basin at the margin as well as in the interior parts of the Craton. There are no sedimentary sequence belonging to the early Proterozoic (2500 – 1600 million years) in Dharwar Craton. The sediments of the Kaladgi Supergroup were deposited on the northern fringes of the Dharwar Craton marked by the Eparchaean unconformity and are exposed on the southern fringes of the Deccan Trap Province. The Cratonization in Karnataka had occurred by 2500 Million years ago. The sedimentary basin like the Kaladgi and Bhīma which occur over the stable craton can be best is considered as Epicratonic. The bulk of the continental crust about 85% formed by the end of Archaean and much of the same was eroded and deposited in sedimentary basin during Proterozoic. The Sediments of Kaladgi Basin are exposed as least disturbed shallow marine sediments resting on the eroded edges of the underlying gneisses, schist and granite.

Shallow marine sediments comprising orthoquartzites (quartz-rich sandstones), argillites (mudstones and shales) and carbonates (limestones and dolomites) arethe principal constituents of the Kaladgi Supergroup. This sequence is practically unmetamorphosed but extensively deformed resulting into identifiable two main types of tectonic deformation, viz. inherited and superimposed (Patil-Pillai and Kale, 2011). According to Kale and Phansalkar 1991, three transgressive cycles of sedimentation, each floored by the clastic suite, and grading into cyclic argillite-arbonate (predominantly dolomite in the Bagalkot Group, but limestone in the Badami Group) suites can be recognized in the Kaladgi Supergroup. The clastics in the sequence indicate beach and nearshore (partly estuarine) depositional environments at the base of each of these cycles. Repeated marine transgressions on an episodically sinking, epicratonic shelf are responsible for the accumulation of this (more than 3500 m) thick pile of sediments in the Kaladgi basin.

Table-2.1: Generalized Stratigraphy of Kaladgi-Badami (after Jayaprakash 1987)

Thickness Formation Member (m)

Katageri Konkankoppa Limestone 85

Halkurki Shale 67 Belkhindi Arenite 39

Halgeri Shale 3 Proterozoic)

- Kerur Cave-temple Arenite 89 BadamiGroup

(Neo Kendur Conglomerate 3

Angular Unconformity Mallpur Intrusive 7 Hoskatti

Dodanhatti Argillite 695

Lakshanhatti Limestone 87 Karkalmatti Hematite schist 42 Arlikatti

Nirlakeri chert-breccia 39

Govindkoppa Argillite 80 Simikeri Subgroup Simikeri Kundargi Muchkundi Quartzite 182 Bevinmatti Conglomerate 15

Disconformity Yadhalli Argillite 58

Kaladgi Super Group KaladgiSuper Bamanbudni Dolomite 402

Muddapur Petlur Limestone 121 Meso Proterozoic) Meso

Jalikatti Argillite 43

–

BagalkotGroup Naganur Dolomite 93 Chiksellikeri Limestone 450 Palaeo Palaeo Yendigeri Hebbal Argillite 166 Chitrabhanukot Limestone 218

Yargatti

LokapurSubgroup Mutalgeri Argillite 502 Mahakut chert-breccia 133 Manoli Argillite 61 Ramdurg Soundatti Quartzite 383 Salgundi Conglomerate 31 Nonconformity Archaen: Granitoids, gneisses, metasediments

2.2: Stratigraphy of the Kaladgi Supergroup

The Kaladgi sediments were first identified around a small town called Kaladgi in the Bagalkot district by Bruce Foote (1876) who designated these sediments as the Kaladgi Series. These rocks also extended in parts of Bagalkote, Vijayapura, Belagavi, Dharwar and Raichur districts of Karnataka state. As a result of regional survey and synthesis, Bruce Foote has classified the Kaladgi Group sediments utilizing mainly lithological characters and structure as the parameters and estimated the total thickness as 4545 to 1212 m. According to him the Kaladgi sediments rest on upturned basement, which are crumpled and disturbed. He proposed a two-fold classification of the Kaladgi Series (Table 2.2).

Table 2.2: Two-fold classification of the Kaladgi Series by Bruce Foote (1876) Upper Kaladgi series 6. Shales, limestones and haematite schists 5. Quartzite with local conglomerate and breccias Lower Kaladgi Series 4. Limestones, clays and shales 3. Sandstones and shales 2. Siliceous limestones, hornstones and chert breccias 1. Quartzites, conglomerates and sandstones

The lower Kaladgi sediments occupy the major portion of the basin, especially the whole of western and southern part, whereas the occurrence of the upper series is restricted to northeastern part of the basin. Bruce Foote considered Kaladgis as Azoic, because of the absence of life. But later with the advent of the concept of Azoic succession was negated away by several work done on the stromatolite occurrences in the Kaladgi Basin.

Nautiyal 1966, proposed the Kaladgi sediments under 'Epi Proterozoic Group' and classified them into lower and upper Series. Nautiyal’s classification is based on metamorphic and tectonic cycles as well as igneous activity of the Precambrian. He envisaged a shear contact at the base of Kaladgis and unconformable relation between lower and upper Series. The upper series are free from tectonic and metamorphic processes and are almost horizontal.

Based on the local lithostratigraphic and regional studies, using detailed field data and other measurements of several stratigraphic sections Viswanathiah 1977 along with the team of

researchers proposed a classification. In his stratigraphic chart, the upper series of the Kaladgi sediments rests unconformably over the Kaladgis and Dharwars, and has been separated from the folded Kaladgis and designated as 'Badami Group'. The order of younger sequence and different lithofacies the Kaladgi Group is further divided into three formations; Bagalkot, Lokapur and Mudhol, in which the geographical locality name combined with the lithostratigraphic unit term. In this Stratigraphy he places Ramdurg Formation under Badami Group.

Chandrasekhara Gowda (1981), divided the Kaladgi Group into five formations based on changes in lithofacies. Each individual formation is characterized by distinctive lithologic association and homogeneity and practically named after the geographic place where the lithostratigraphic unit is typically developed. According to him, the five formations of the Kaladgi Group are named as Ramdurg, Solapur, Lokapur, Mallapur and Danhatti. These formations are resting conformably one above the other and each formation is further subdivided into different members.

Following standard classification scheme and nomenclature Jayaprakash et al. 1987, have suggested that the entire sequence to be recognized as the Kaladgi Supergroup and have renamed the older unit as the Bagalkot Group and younger as Badami Group. The generalised lithography of the Kaladgi Basin is given in Table 2.1. Badami Group is considered to be separated by angular unconformity from younger sediments deposited over Bagalkot Group. It comprises of two formations namely Kerur and Katageri. Whereas the Bagalkot Group again divided into two Subgroups namely Simikeri and Lokapur. The Bagalkot Group has been further divided into eight formations in that, three formations are classified under Simikeri Subgroup and rest under Lokapur Subgroup. Each formation belongs to different lithounits of this area and its features are known members. Simikeri and Lokapur Subgroups are separated by disconformity between Yadhalli and Kundargi Formations. The nonconformity is considered as separating the Kaladgi sediments and basement Dharwar Supergroup of granitoids, gneisses and metasediments.

2.2.1: Basement The Archaen Peninsular Banded gneisses and pink granite (Dharwar Batholith) and the various granite bodies occurring as inliers near Murgod, Sirur, Amingarh and other places and the Greenstone belts (Hungund-Kushtagi, Dharwar) schist belt near Bagalkot, Closepet

granite and inliers of schists near Mulgali underlie the basin with an angular unconformity form the basement of the kaladgi basin over which the evolution of the basin has been initiated.

The older succession of Kaladgi basin is called the Bagalkot Group that corresponds to the Cuddapah Supergroup, and the upper succession is called the Badami Group that is the possible equivalent of Kurnool Group. Bagalkot Group is divided into the lower Lokapur Subgroup and the upper Simikeri Subgroup. The lithostratigraphy of the Kaladgi-Badami basin is described below:

2.2.2: Bagalkot Group The Rocks belonging to Bagalkot group are mainly clastic types which include Conglomerate, Quratzarenites, Shale and Breccia, however the occurrence of non-clastic component in the form of Dolomite and Limestone is also noticeable in central domical regions of the Kaladgi Basin. The lower boundary of this unit is an unconformity with the basement Granites and Gniesses of Dharwar Supergroup. Upper boundary is marked by a prominent angular unconformity with younger Badami Group. This group is further classified as older Lokapur Subgroup and younger Simikeri Subgroup.

2.2.2.1. Lokapur Subgroup The flanks and Basin margin region are composed of mainly Argillaceous to Arenaceous facies rock types whereas towards the centre of the basin the rocks are consisting of non- clastic carbonate facies. Altogether Five Formations and thirteen members constitute the Subgroup.

• Ramdurg Formation: This marks the basal unit resting directly over the Archaean Basement and is mainly represented by Clastic component of Conglomerate, Arenite and Argillite. Three members are included in this Formation.

Salgundi Conglomerate: This is a basal conglomerate resting unconformably over granitoids and schists. It is composed of Subrounded, cobble sized, clasts of Quartzites, banded haematite quartzite, vein quartz and chert.

It is oligomictic in nature, matured and well sorted well-rounded pebbles of vein quartz, quartzite, chert, jasper, and fresh feldspars.

Saundatti Quartzite: Wherever the basal conglomeratic unit is insignificant, this quartzite Member constitutes lowermost unit of the Kaladgi Supergroup. As this forms the most resistant and persistant unit in the Lokapur Subgroup, it has a prominent geomorphic expression. The Saundatti Quartzites form a marker horizon and demarcates the basin boundary of the Bagalkot Group. This member shows varying petrological composition from quartzarenite, felsarenite, subfelsarenite to quartzwacke. Savadatti is the type area for this Member.

Munoli Argillite: This member is well developed around Munavalli and occurs as thin and discontinuous band in the eastern part of basin. It has a gradational contact with the Arenites lying under it and is brown and purplish in colour.

• Yargatti Formation: This formation essentially composed of Chert Breccia, argillite and dolomites. Presence of Argillite is sparse.

Mahakut Chert- Breccia: This member is composed of pink, fine grained, crypto crystalline to microcrystalline tough matrix in which angular fragments of chert of varying size are welded together. It occurs as lensoidal bodies in southern and western part of the basin.

Muttalgeri Argillite: Though the outcrops of this unit are very few, this is one of the thickest members of Bagalkot Group. This argillite is locally carbonate rich. It is also represented by purple coloured manganiferous argillite.

Chitrabhanukot Dolomite: Near the core of the basin, at Chitrabhanukote this carbonate Member forms a roughly circular dome. Colour of the rock varies from grey, blue-grey to dark grey. Presence of stromatolites marks the characteristic of this unit. (Plate 2.3)

• Yendigeri Formation: A limestone bed exceeding 800m in thickness is important lithounit of this formation and is extensively exploited for industrial purpose. Apart from this it is also comprised of smoky blue argillite and dolomites.

Hebbal Argillite: This is Characteristically soft, friable, smoky blue rock. It is intruded by small quartz veins parallel to bedding.

Chikshellikeri Limestone: This is the thickest member of the Bagalkot Group. It is inforamally divided into a Varigated Limestone and grey limestone. This is devoid of any organo-sedimentary structures which are present profusely in other dolomite members.

Naganur Dolomite: Presence of organic carbon gives a black colour appearance to this Dolomitic member. It has a maximum thickness of around 100m.

• Muddapur Formation: Except that the dolomite member attains maximum thickness of 400 m and is Stromatolite bearing, this Formation is similar to that of Yendigeri Formation.

Jalikatti Argillite: This forms the marker horizon and display folding and deformation. The rock is phyllitic and has developed a prominent cleavage parallel to the bedding plane.

Petlur Limestone: this member has a limited areal extent and thickness and is subdivided into (a) variegated limestone and (b) grey limestone.

Bamanbudni Dolomite: This rock generally occurs in light grey colour and composed essentially of dolosparite and partly of dolomicrite.

• Yadhalli Formation: This is the uppermost member of the Lokapur Subgroup and it occurs as Smoky blue to purple coloured soft, fissile to massive Argillite unit.

• Disconformity: It appears that sea retreated for a short period of time after deposition of Lokapur Subgroup and underwent upliftment, weathering and erosion of the previously deposited formations. This gave rise to a disconformity between the individual subgroups of Bagalkot Group.

2.2.2.2. Simikeri Subgroup This is similar in lithological composition to that of Lokapur Subgroup but has a limited areal extent. It is confined to the central portion of the basin and always occurs as elongated doubly plunging syncline. It constituted of Three Formations and Seven Members.

• Kundargi Formation: This is another Clastic dominated sequence within Bagalkot Group. This includes three Members of which argillite is a prominent one. Other includes Quartzite and Conglomerate.

Bevinmatti Conglomerate: This occurs as discontinuous lenses, developed with maximum thickness of 15m. At places, the clasts here are elongated or stretched parallel to the bedding plane.

Muchkundi Quartzite: It is developed to a maximum thickness of 200m. It is medium to thickly bedded and well sorted.

Govindkoppa Argillite: This rock unit similar to that of Manoli argillites. Good exposures are present at very few places.

• Arilkatti Formation: Presence of a Schist member in this sequence is its unique character. It also includes Carbonate horizon and layer of Breccia between which the haematite band is sandwiched.

Niralkeri Chert Breccia: these are in sharp contact with underlying underlying argillites and are exposed as ridges. It forms smooth to flat topped linear ridges along quartzites.

Kerkalmatti Hematite Schist: Though the thickness of this unit is varying and has limited areal extent, this member is in sharp contact with underlying and overlying units. It is distributed throughout the basin in discontinuous patches. Hematite is massive with thin bands of chert, jasper and quartzite; compositionally the schist is argillaceous or siliceous.

Lakshanhatti Dolomite: This dolomite is grey to smoky blue in fresh cuttings and deep grey on weathered surfaces, with interbedded dark brown, black and white cert ribbons.

• Hosakatti Formation: Series of minor folds exhibited by single argillite member is the characteristic of this Formation.

Dadanhatti Argillite: This Members occurs at the core of Kaladgi Basin and has suffered maximum deformation. As a result of this, the member exhibits development of many minor folds. It marks the youngest sedimentary rock unit of the Bagalkot Group.

Mallapur Intrusive: Rocks of Bagalkot Group are intruded with both acid intrusive consisting of quartz vein and pegmatite veins of hydrothermal origin parallel to the bedding plane as well as basic intrusive represented by dolerite dykes. Nowhere these dykes have been seen to intrude the younger Badami Group of rocks.

2.2.3: Badami Group: A distinct Angular Unconformity separates the deformed sedimentary rock units of Bagalkot Group from that of Horizontal, less deformed Badami Group. It is marked by presence of a prominent conglomerate horizon. Two Formations and Six Members constitute this Group.

• Kerur Formation: This consists of four Members which are mostly arenaceous in character. The basal conglomerate member is important in stratigraphic terms as it marks separating horizon between the Bagalkot Group and the younger Badami Group of rocks.

Kendur Conglomerate: This conglomerate with a thickness of 5m is seen overlying the granitoids, meta sediments and a few members of Bagalkot Group thus suggesting a major unconformity and hiatus commencing the deposition of a new cycle of sedimentation.

Cave-temple Arenite: The Cave-Temple Arenite Member of Badami Group comprising predominantly of sandstone forms one of the most interesting litho-units exposed around Badami. It has a prominent topographic expression in form of flat- topped barren hillocks. These arenites are medium to coarse grained, moderate well sorted, subrounded to well-rounded and can be classified into the quartz arenite to sub-arkose categories.

Halgeri Shale: This horizon has a very less thickness and is constituted of beds of shales which are bottle green to greenish yellow in colour, friable with convolute laminations and rich in micaceous minerals. This shale acts as a key bed to separate the arenite members in the Badami Group.

Belikhindi Arenite: This unit is in sharp contact with the underlying unit. These arenites lack ferruginous matter and have peculiar geomorphic expression i.e. forming smooth hills with a lighter tone and a thin soil cover supporting thorny bushes. While primary sedimentary structures like cross bedding, ripple marks, casts and convolute lamination are present in cave temple Arenite member, these are rarely recorded in this Member.

• Katageri Formation: A shale overlain by Limestone represents this Formation. The shale has a large Areal spread and the limestone is mostly flaggy.

Halkurki Shale: The rock is chocolate brown to dark brown in colour, finely laminated distinctly bedded with prominent bedding fissility.

Konkankoppa Limestone: This is the youngest Member of the Kaladgi Supergroup with gradational contact with the underlying shale. The limestone is flaggy, medium bedded, bottle green, cream, buff and pale grey with frequent partings and fine colour banding.

2.3: Study Area: The Study area is located in the northern region of Karnataka and it comprised of Bagalkote and Belagavi district of Karnataka state. It falls within the Northern Maidan region and is well situated in interior region of Deccan Plateau of Peninsular India. The region is around 210 km from Western Coast of India and falls in the Rain Shadow region of Western Ghats. The average height above mean sea level is 450-800 meters. The Bagalkot district lies between the northern from 15°49’ to 16°46’ North latitude and from 74°55’ to 76°20’ East longitude and Belagavi district is located in the north-western corner of the State and lies between 15° 23' and 16° 58' North latitude and 74° 5' and 75° 28' East longitude. The geological map of Study area is provided in Figure 2.1. The region has a good accessibility by motorable road and important locations are well connected by Karnataka State Transport buses. Two domestic Airports are located near this area. Belagavi Airport is 94 km from Lokapur and Huballi Airport is 80 km from Savadatti.

2.4.1: Topography:

Topography plays an important role in the land use pattern of an area, its relief, slope, drainage and soil types. These aspects have an enormous amount of influence both directly and indirectly over land use pattern. The study area forms part of Maidan region of northern Karnataka. These are mostly low-lying flat lands with presence of prominent hills and flat- topped plateaus. It exhibits a rugged and undulating terrain, traversed by chains of detached hills trending in east - west direction. The terrain is highly eroded and dissected by the rivers namely Krishna, Malaprabha and Ghataprabha. There are ranges known as North Ghataprabha and North Malaprabha ranges. The Western part of the region is elevated where the maximum height is 650 meters and the terrain then gradually slope down towards the east where the minimum height is 530 meters.

2.4.2: Climate

As the Location forms the part of Rain Shadow Zone of Western Ghat, it experiences mostly a dry climatic condition with scanty rainfall. Dryness and hot weather prevail in major part of the year. The area falls under Northern Dry climatic zone of Karnataka state and is categorized as drought prone. The climate of the study area is quite agreeable and free from extremes.

Seasonal rainfall pattern indicates that, major amount of (326 mm) rainfall is received during South-West Monsoon seasons, which contributes to about 60% of the annual normal rainfall, followed by North-East Monsoon season (148 mm) constituting about 27% and remaining (70 mm) 13% during pre-monsoon season. The average temperature of the region is 33o C. The minimum temperature is recorded in the month of January and it is 17° C and maximum temperature of May is 40° C, the mean maximum temperature in the monsoon months does not differ appreciably from that of the winter months.

2.4.3: Drainage

A well-developed dendritic drainage is characteristic drainage pattern of the study area. It is part of Krishna River basin of which River Malaprabha and River Ghataprabha are important rivers flowing through this region. These rivers have carved out deep valleys across the study area. Several tributaries of these principal rivers have made the region gentler.

2.4.4: Soils:

The study area has few types of soils formed under semi-arid climate, which are grouped into three categories i.e. Deep black soil, Shallow black soil and Mixed red and black soil

• Deep Black soil: The colour of this soil varies from dark brown to greyish brown. Salty clay texture is also common. These are calcareous and alkaline. These soils are moderately drained and are highly retentive of moisture and also fertile.

• Shallow Black Soil: These soils are dark brown to dark reddish brown in colour. As this soil group belongs to the Deccan trap, it is usually encountered on undulating topography and also on schist and limestone uplands. Such soils are weak, alkaline and have moderate to high water holding capacity.

• Mixed Red and Black Soil: This type of Soils occurs on gentle undulating plain of gneisses, schists and sedimentary rock formations of the region.

2.4.5: Natural Vegetation

The region under study of Bagalkot and Belagavi districts, exists in the semi-arid region, experiences hot summer, dry winters and erratic distribution of rainfall. As a result of it, very sparse distribution of natural vegetation is observed in the region (Plate 2.4A). The distribution of vegetation is also not similar all over the region. The highest concentration is in the southern region and the lowest is in the northern region. Most of the vegetation of the region is open thorny to Shrubs and stunted trees.

2.4.6: Geology • Lokapur Town:

Most of the area at Lokapur is composed of Carbonate units which are characterised by flat topographic features. These limestones vary from massive sparry limestones to stromatolitic limestones. On detailed observation it was observed that some of the limestones were completely crystalline in nature and were devoid of any terrigenous clasts. These laminae were observed to be of without any significant internal stratification and display parallel stratification. (Figure 2.9a). Such a nature of Carbonate rock unit is suggestive of deposition under quiet water condition, free of current or wave influence (Collinson and Thompson 1982, Doglioni et al. 1989, Miall 1990). The bedding planes in some of these display a remarkably parallel laminated geometry. The alteration of pure limestone and clayey material has been observed at the fringes of Lokapur town. At such outcrops, the clay band stands out and forms a rugged surface resulting from inequal resistance to weathering by these units. (Figure 2.10). Such laminations are suggestive of very flat, low gradient depositional interface (Wilson 1975, Tucker 1988).

Limestone outcrops around Lokapur are observed to be deformed and jointed. These joints marks avenues for circulating meteoric waters. This has led to widening of these joints and precipitation of secondary minerals along them. Development of Karstic structures and Cave-ins at many locations around Lokapur is attributed to such post depositional activity. (Figure 2.9b)

All limestones are generally hard and compact and often bedded in character and display a great variation in the color, white, grey, and variegated. The dolomites/dolomitic limestone

are generally thin bedded/nodular and buff, pale grey to dark grey and is often seen traversed by Quartz veins. Stromatolite structures (Figure 5.1, 5.2) of various types are seen in only the dolomitic rock units. No other depositional structures are observed in the carbonate rocks. Most of these carbonate units are highly disturbed and folded and display deformational structures resulting due to both cataclastic and ductile types of deformation.

• Around Munavalli Village

The Arenites of Saundatti Quartzite Member observed here display characteristic bimodal grain size distribution. Though medium size clasts dominate the rocks, coarse clasts occur as floating grains surrounded by medium grained matrix. (Figure 2.11). Further, these rocks attain general massiveness devoid of any internal structure. It can be attributed to rapid settling. These massive arenites also preserve primary sedimentary structures like ripple marks.

• Savadatti Town

The Proterozoic sedimentary rocks belonging to Ramdurg Formation is well exposed here. These are composed of Arenites which are rich in Quartz as clasts. A band of Conglomeratic horizon around half a meter thick is observed occurring within the Arenite unit at a road cut exposure. A thickly bedded planar parallel bedding is characteristic bedding observed in these rocks (Figure 2.8b). Thickness of beds varies between 30 cm to 50 cm. The bedding planes also exhibits preservation of well-developed primary sedimentary structure like ripple marks. These are a wave-like bed form that occurs in fine sands subjected to gentle traction currents. These are wave formed symmetrical ripples with straight and bifurcating crests (Plate 2.3a, b). Ripple index as estimated to be 10, having more rounded troughs and flattened crests.

• Ramdurg

Thick beds of Quartz rich Arenites are exposed which preserve primary sedimentary structures. Presence of Asymmetrical ripple marks in these rock units is attributed to be formed under conditions, where abundant sediment was present, particularly sediment in suspension, which quickly got buried and preserved rippled layers. At a stream cut outcrop near Ramdurg, cross-lamination were observed (Figure 2.12). Cross-bedding is one of the most common and most important of all sedimentary structures. It is ubiquitous in traction current deposits in diverse environments. Basically, two main types of cross-bedding can be

defined by the geometry of the fore sets and their bounding surfaces: tabular planar cross- bedding and trough cross-bedding (McKee and Weir, 1953). The ones that are observed here are trough cross bedding. The upward concave fore sets lie within erosional scours which are elongated parallel to current flow, closed up current and truncated down current by further troughs. The co-set thickness as measured is around 40cm with a set thickness of 20cm. The cross laminae are observed to be of 5-10 cm thick. Sedimentary structures of this type are understood to be formed under conditions where a balance is achieved between traction transport and sediment supply so that ripples do not migrate despite a growing sediment surface. (Boggs 2009). The palaeocurrent analysis of the cross-bedding structures suggest northwesterly direction of the sediment transport.

• Hooli Village

The rock conglomerate here is matrix supported which is ferruginous. These beds have planar base and their clasts include Quarts, Jasper, and lithic fragments and are chaotic and disoriented (Figure 2.5). The quartz is granular and colourless. The rock is poorly sorted, oligomictic and matrix supported. Such a feature can be attributed to Debris-flow conglomerate facies (Blair and McPherson, 1994). Chaotic orientation of clasts and their protrusion above bed surface indicate high matrix strength of the parent flows. The conglomerates can be a result of mass flow as well as traction current deposits within and without channels (Mazumder and Sarkar, 2004)

Geological Map of Study Area

Basin (after Jayaprakash et al., 1987; al., 2009) al., et et Jayaprakash (after Basin Dey

Figure 2.1: Geological map of the Kaladgi the of map Geological 2.1: Figure

Figure 2.2: Map showing Sample Location for Carbonate samples (after Mahender, 2014)

Field photographs

Figure 2.3 a. Symmetrical ripples with bifurcating crests as seen at Ramdurg

Figure 2.3 b. Symmetrical ripples as seen at Savadatti

Field photographs

Figure 2.4. Toppled boulders of Salgundi Conglomerate over Gneissic Rocks at Hooli Hooli Village is the location where Mesoproterozoic Sedimentary sequences are seen resting directly over Archaean basement.

Figure 2.5: Disoriented clasts seen in matrix supported conglomerate at Hooli

Field photographs

Fugure 2.6: Sparsely distributed Natural vegetation cover at study area. (Hooli Village)

Figure 2.7: A thin Conglomeratic band seen within sandstone unit at a Road cut section Savadatti

Field Photographs

Figure 2.8 a. Thickly bedded planar parallel beds (inclined) observed near Ramdurg

Figure 2.8 b.: Massive Sandstones devoid of any structure exposed near Savadatti

Field photographs

Figure 2.9 a.Deformed strata of Crystalline Limestone, devoid of any internal stratification near Lokapur

Figure 2.9b: Widened joints due to percolating meteoric waters in Limestone outcrop at Lokapur.

Field photographs

Figure 2.10: Outcrops exposing clay bands prominently preserved in intercalating unit of Clay-Limestone

Figure 2.11: Bimodal distribution of Grain size probably a result of local variation in energy conditions at depositional point as observed in Arenite at Munavalli.

Field photographs

Figure 2.12: Stream cut section near Ramdurg exposing preserved cross stratification structure

Figure 2.13: A near horizontal unit of Argillite seen occurring in the field traverse taken at Munavalli.

CHAPTER 3: METHODOLOGY

A thorough field work forms part of any geological study. As this thesis deals with understanding the sedimentological characteristic of lower sequence of Proterozoic sediments of Kaladgi Basin, important field areas were identified by going through previously available literature and doing a reconnaissance survey of the same. Based on it, the area around Savadatti town, Ramdurg, Hooli Village, Munavalli and Lokapur was marked for the present study. Field studies were carried out with the objective of knowing the extent of the individual litho units, field checks and sampling along various traverses within the basin. An account of these field techniques followed is presented in this Chapter. Petrographic studies have been made in thin sections prepared from the hard sandstone specimen collected from different field exposures. Different constituents were identified under the microscope for petrographic analysis.

Various laboratory techniques employed for the analysis and study of these rocks is also presented in this chapter. Initially, rock specimen collected from field were cleaned and thin sections of the same were prepared to be studied under the microscope. Further, the selected samples were broken and crushed to powder level for geochemical analysis. Thin sections were studied for petrographic analysis as well to make the modal analysis. As some minute observations were required to be made, chips of carbonate samples were observed under Scanning electron microscope at facility provided at Department of Electronics, Goa University and chips of clastic rock samples were studied at Table top SEM at the RGL, ONGC Vadodara.

3.1 Field Work

Sedimentary rocks, especially siliciclastic rocks are rewarding when studied in field. Interpretations can be made out regarding their mode of formation from field observations. With regards to Carbonate rocks it is bit tricky to draw conclusins due to their fine grained nature and hence their study can benefit greatly from follow up microscopic work and geochemical analysis.

Field Investigations primarily focussed on recognition and mapping of various lithological units, identification of stratigraphic and lithological attributes which includes identification of lithological contacts, rock type, structural features and other parameters. For the present work, field was undertaken principally in the areas of Savadatti town, Munavalli, Ramdurg, Hooli village and the outskirts of Lokapur town of Karnataka. Field investigations involved taking traverses along road cut sections, canal sections and stream sections wherever best

exposed. During the course of field work, the prominent locations for their occurrences have been identified and their mutual relationships between different litho units were studied. Brief description of field locations is given here.

Outskirts of Lokapur:

The studied exposures at Lokapur lie between the latitude 16°9’54” N to 16°9’24” N and Longitude 75°22’54” E to 75°31’03” E. In general, the town is having flat topographic character however, it is bounded by contrasting hilly terrain towards the East. Hills are rising at an elevation upto 100 to 150 m above the plain areas. The hilly region is mainly composed of Hard compact Sandstones whereas the low-lying plains are dominated by Carbonate rocks. The area is a semi-arid region and a part of rain shadow region of Western Ghats. Vegetation is sparse, devoid of any large canopy tree and is mainly composed of thorny bushes.

Munavalli Village:

The studied area lies at Latitude 16°20’00” N to 16°20’29” N and Longitude 75°26’22” E to 75°37’48” E. Munavalli is a village in the Ramdurg Taluka of Belagavi district. This region is characterised by presence of isolated hills which are mainly composed of Arenites. Vegetation is sparse and it is mainly comprised of thorny bushes. Presence of shale horizons (Figure 2.13) has been observed at small isolated regions in fields around this village.

Savadatti Town:

The study area lies between the Latitude 15°46’56” N to 15°49’03” N and Longitude 75°08’06” E to 75°07’18” E. It is Located around 80 km towards South East of Belgavi. The altitude of the region ranges from 600 to 900 meters above sea level. But there are some isolated peaks such as Yellamma hill. These hills are generally flat topped and have steps slopes. A major stream cascading over the hill slopes forming a prominent waterfall is striking geomorphological feature at this area.

Ramdurg:

The town of Ramdurg, located about 30 km from the town of Savadatti lies between latitude 16°05’00” N to 16°05’15” N and longitude 75° 52’20” E to longitude 75° 52’30” E. The terrain is hilly, vegetation is scanty and is marked by thorny bushes.

Hooli Village:

The studied area is on the main road from Savadatti towards Ramdurg. It lies at 15°47'38.7"N latitude and 75°11'07.8"E longitude. At this location the younger Proterozoic rocks rests directly over the Gneissic basement of Dharwarian rocks (Plate 2.4). The peneplane region is covered by Gneisses whereas the adjoining hills ranging up to height of 200m from plains are composed of Conglomerate and Arenites of Kaladgi Supergroup. The rocks are jointed and fractured. Vegetation in the area is scanty and dominated by thorny bushes and shrubs.

3.1.2: Primary Sedimentary structures:

Sedimentary structures give direct clues about processes responsible for the deposition of sedimentary rock. Specific information regarding depositional setting can also be derived from some structures. On different traverses taken in study area, some of the primary sedimentary structures which are observed includes, Ripple marks, cross stratification and trough cross stratification. In carbonate units, different type of stromatolitic structures were observed.

Ripple Marks:

Ripples are very common and occur on bedding surfaces, but the larger-scale dunes and sand-waves are rarely preserved intact as the bedforms. On careful examination of these structures they were identified to be Wave formed ripples as the crests of this type of ripples are generally straight and the bifurcation of crests is commonly observed (Figure 2.3a, b). Crests seen re-joining to enclose small depressions (called tadpole nests!). In profile, the troughs tend to be more rounded than the crests which can be pointed or flattened. Wavelength is controlled by sediment grain-size and water depth, larger ripples occurring in coarser sediment and deeper water. Their wavelength ranges between 1.9 to 2.2 cm. The ripple index of wave-formed ripples is calculated to be around 10.

Bearings of these ripple marks were noted at Savadatti hill section, at outcrops from Munavalli towards Savadatti and around Ramdurg.

Table 3.1: Bearings of ripple marks recorded at various locations

Savadatti Munavalli Ramdurg N40 N310 N220 N35 N140 N190

N50 N135 N200 N10 N150 N196 N35 N120 N210 N45 N160 N200

Cross Stratification:

Cross-stratification is an internal sedimentary structure of many sand-grade, and coarser, sedimentary rocks and consists of a stratification at an angle to the principal bedding direction. Much cross-stratification is formed as a result of deposition during the migration of ripples, dunes and sand-waves. However, cross-stratification in sand-grade sediments can also be formed through the filling of erosional hollows and scours, the growth of small deltas (as into a lake or lagoon), the development of antidunes and hummocks, the lateral migration of point bars in a channel and deposition on a beach foreshore (Tucker, 1982).

The three-dimensional shape of cross-stratified units defines two common types: tabular cross-strata, where the inter-set boundaries are generally planar, and trough cross-strata, where the inter-set boundaries are scoop shaped. In the present study area the latter variety was observed along stream cut sections on Hooli- Ramdurg Road. Trough cross beds usually have tangential bases, and in bedding-plane view the cross-beds have a nested, curved appearance. (plate). results from curve crested (i.e. three-dimensional) bedforms.

Massive Beds:

Massive beds have no apparent internal structure and were prominently seen at entire road traverse from Savadatti to Ramdurg. Massiveness in the sedimentary rock strata can be attributed to two major alternative interpretations. Which can be, it was deposited without any structure or that the depositional structure was subsequently obliterated by later processes such as bioturbation, recrystallisation, dolomitization and dewatering. However, the present outcrops are suggestive of former interpretation. This type of condition mainly arises through rapid sedimentation, where there was insufficient time for bedforms to develop. (Figure 2.8 a, b)

3.2: Laboratory investigations The observations of primary sedimentary depositional structures in the field reveal some information regarding depositional environment of these sediments to be deposited under shallower fluvial set up. Lithology, texture was also observed to be varying with traverses taken laterally within the extent of basin. For detailed and minute observations, selected samples collected from field were then subjected to laboratory analysis.

3.2.1: Thin section studies

The selected samples collected from the field were utilized in the laboratory for laboratory investigations. It involved detail analysis of the sandstones and carbonates occurring in the area. The petrographic studies were made from the thin sections of hard Arenites as well as carbonate samples. The primary detrital constituents like quartz, feldspars, mica, and rock fragment were studied with the help of petrological microscope. These studies for petrographic observations were made under Petrological microscope Model: NIKON Eclipse E200 at the Department of Earth Science Goa University. Different types of quartz present in the Saundatti Quartzite Member of the study area were also studied. Sixteen representative sandstone samples were selected for modal analysis. Mineralogical composition of these samples was determined by modal analysis. Point counting was carried using the Gazzi-Dickinson method (Dickinson, 1970; Gazzi, 1966; Ingersoll el. al. 1984). More than 500 points were counted for each thin section, using the maximum grid spacing to give full coverage of the slide.

The raw analytical data has been processed from mineralogical classification made on the basis of the percentage of quartz, feldspar and rock fragments resulted from the compositional study plotted in triangular diagrams. The results of the petrographic studies were also used for to give meaningful interpretations about the provenance (Dickinson and Suczek, 1979), palaeoclimate (Suttner and Dutta, 1986) and plate tectonic setting of the sandstones (Dickinson and Suczek, 1979, Dickinson et. al, 1985).

3.2.2: Acid etching and staining

Acid etching and Staining is one of the most useful techniques in mineralogical analysis of sedimentary rocks, particularly in carbonate rock analysis. It can be used in modern carbonate sediments and in partially or wholly consolidated Pleistocene rocks

to identify the metastable carbonate minerals aragonite and magnesium calcite, dolomite, gypsum and anhydrite in modern and ancient limestones, dolostones and evaporites.

Many stains have been developed to promote identification of carbonate minerals some are more effective and some “take” more rapidly than others. Alizarine red-S, an organic stain, is the most effective stain for calcite. Calcite is stained deep red within 2-3 minutes. Whereas dolomite is not stained. For aragonite determination the most sensitive stain is Feigl's solution, which turns aragonite black but does not affect calcite.

In the present study, small polished slabs (up to 800 grade) and uncovered thin sections have been etched with 8-10% HCl for 2 to 3mts. and then have been stained using the 2% solution of alizarine red-S. The stained slabs and sections have been observed under the microscope for the observation of the mineralogy. Presence of aragonite and calcite was confirmed in the miliolitic limestone samples by staining method. Further to substantiate the staining results mineralogical studies have been carried out including XRD, petrography, SEM observation and chemical analysis.

3.3: Scanning Electron Microscopy

The scanning electron microscope has been widely used in geology for a considerable period. Due to the high resolution attainable (about 40 A in most new commercial instruments) and the great depth of field, the secondary electron (SE) mode has been most commonly used to examine fine surface detail on a wide variety of geological materials including sand grains, microfossils, and carbonate cements (Krinsley and Doornkamp 1973; Whalley 1978; Smart and Tovey 1981). SCANNING electron microscopes (SEMs) (which are used to observe microscopic features) have become essential tools in numerous different areas of research and development. The specimen chamber of an SEM is typically maintained at a pressure between 10-5 Pa (hard vacuum) and 102 Pa (soft vacuum). This is done to keep the path of the electron beam free of gases because of the scattering that occurs when electrons collide with gas molecules.

For SEM analysis purpose around 40 representative samples of Clastic rocks as well as of Carbonates was prepared at Hard Rock laboratory of Department of Earth Science, Goa University. Well defined surface of the specimens was identified to be focused under SEM. These studies were made at the SEM facility at the Department of Electronics, Goa University and at Regional Geoscience Lab, ONGC, Vadodara. (Figure 3.2)

The SEM images were captured on Hitachi table top microscope TM-1000. This instrument has allowed stereoscopic observation of grain surface with a high focus depth. (Figure 3.1).

Recently, increasing use has been made of backscattered electron (BSE) imaging in both the physical and biological sciences (Abraham and Denee 1974; Kiss and Briskies 1976; Becker and Sogard 1979; Healy and Mecholsky 1981; Hall and Lloyd 1981). Particularly when used to study polished specimens, BSE imagery offers a number of important advantages over SE imagery and provides a valuable petrographic technique for the analysis of fine-grained rocks (Krinsley et at. 1983; Pye and Krinsley 1983). Even when applied to coarser-grained rocks, BSE microscopy can provide useful data to supplement the results of optical thin- section work (waychunas and Thiel 1981; Bisdom et al. 1983a).

3.4: X-Ray diffraction

A century has passed since the first X-ray diffraction experiment (Friedrich et al. 1912). During this time, X-ray diffraction has become a commonly used technique for the identification and characterization of materials and the field has seen continuous development. Advances in the theory of diffraction, in the generation of X-rays, in techniques and data analysis tools changed the ways X-ray diffraction is performed, the quality of the data analysis, and expanded the range of samples and problems that can be addressed. X-ray diffraction was first applied exclusively to crystalline structures idealized as perfect, rigid, space and time averaged arrangements of atoms, but now has been extended to virtually any material scattering X-rays. Materials of interest in geoscience vary greatly in size from giant crystals (meters in size) to nanoparticles (Hochella et al. 2008; Waychunas 2009), from nearly pure and perfect to heavily substituted and poorly ordered.

Most X-ray diffraction techniques rely exclusively on the portion of X-rays elastically scattered by electrons (Thomson scattering). The diffraction event can be visualized as a consequence of the interaction between electromagnetic radiation and electrons. The electromagnetic radiation enters the material with a certain frequency and the electrons in the material “ride the waves”, oscillating in the direction of the polarization of the incident light. Since an accelerating electron in turn creates electromagnetic radiation, the oscillating electrons in the material give off light in spherical distributions, all with the frequency of the oscillating electrons. The transfer of energy from the incident light into the oscillation of the electrons takes place by decreasing the intensity of the incident X-rays. In order for X-rays to be diffracted, namely to be spherically scattered and then experience constructive

interactions in particular directions, they have to interact with a material showing a periodicity in the distribution of electrons comparable to the X-ray wavelength (λ). The wavelength of X-rays, ranging from 0.1 to 100 Å (equivalent to energies of about 120 to 0.1 keV) is in the range of interatomic distances or unit cell sizes, and therefore diffraction can be produced by the elastic interaction of X-rays with matter having some degree of ordering.

The interpretation of modern X-ray diffractograms require several steps during which the nameless electronic peaks of the diffractograms are connected and interpreted into significant geologic data.

The following are the important steps: i) measurement of molecular plane repeat distances (d-spacing) which can be obtained or read from the conversion tables (2 Ɵ to D-spacings) given in many books, ii) identification of mineral species using ASTM/JCPDS powder data files, iii) qualitative and semi-quantitative and quantitative interpretation of mineral abundances and iv) measurement of average crystalline size of selected minerals.

In the present study the carbonate fraction limestone has been powdered to 400 f size and the powdered samples have been analysed at the laboratories of NIO, Goa, using the Philips X-ray Diffractometer. The following specifications have been used for the analysis: - Target: CuKa & Fe; Scanning speed: 2cm/min.; scanning range of 2 Ɵ: 20 to 65. The 2Ɵ values of various characteristic peaks identified have been converted to respective d-spacing values using the conversion tables given in Carver (1973). The peak heights have been measured and the relative intensities of peaks are calculated by taking the strongest peak as 100%. The d-spacing values along with corresponding relative intensities have been compared with the JCPDC powder data files for identification of different mineral phases.

Scanning electron microscopy

Figure 3.1: Techniques for Atmospheric SEM Imaging. The observation of bulk material is difficult when the membrane and the specimen are in contact as in diagram (a). When there is no contact between the membrane and the specimen, as in diagram (b), the observation of bulk material is easy, however the electron beam is scattered by the intervening gas molecules. (Hitachi Review Vol. 65 (2016), No. 7)

Figure 3.2: Hitachi TM3000 SEM used at RGL-ONGC, Vadodara

CHAPTER 4: CLASTIC

SEDIMENTOLOGY

4.1. Introduction:

Sandstones are composed of framework grains, matrix, and chemically precipitated cement and pores. Framework grains of sandstones are derived from a diverse type of source rocks. These clastic framework constituents are subjected to various types of modifications during transportation, deposition, and diagenesis. These changes lead to modifications in their shape, size, and relative abundance. Hence, the changes in composition and texture are dependent upon the process it undergoes and time. Composition of framework constituents can also be used to decipher the paleoenvironmental conditions under which the rocks were formed. Also, the study of the clastic constituents can be used as a tool for the sandstone classification. It also helps us know the character and type of sandstones, degree of diagenesis, compaction, cementation, lithification, pressure solution, and the effects of tectonic control on the sedimentation. Detrital modes of sandstone suits also provide information about the tectonic setting of the basin of deposition and associated provenance (Dickinson, 1985). Petrographical studies also help reconstruct the paleoclimate as existed during the time of deposition (Suttner and Dutta, 1986). Moreover, the petrography of sandstone depends significantly on the composition of the source rock.

Therefore, the sandstone petrography is used as an essential tool to determine the provenance and tectonic setting of the depositional basin of sandstones (Basu et al., 1975; Dickinson and Suczek, 1979; Zuffa, 1980; Dickinson, 1985; Ingersoll et al., 1995; Uddin and Lunberg, 1998; Das and Singha 1999; Das, 2008, Das et al., 2008; Das and Sharma, 2009).

As Petrography provides important clues regarding tectonic history, provenance, and other characteristics of the sediments, a very detailed study has been made of the samples collected from Saundatti Quartzite Member of the study area. The thin sections of the present sandstones were also observed under Scanning Electron Microscope to know their mineralogical constituents, character and type, diagenetic effects, provenance, tectonic framework, and the palaeoclimate prevailing at the time of deposition of the sandstones under study.

4.2. Detrital Mineral Composition:

An account of various detrital mineral constituents that occur in clastic sedimentary rocks of Saundatti Quartzite Member is presented here. The data of Modal analysis carried out

for Samples belonging to Saundatti Quartzite Member is presented in table 4.1. The recalculated tabulated data from table 4.1 for classification is given in table 4.2.

Table 4.1: Data of Modal Analysis of studied samples of Saundatti Quartzite Member Lithic Quartz Total Feldspar Sample Sample Fragments No. ID Monocrystalline Polycrystalline

1. RDG-1 50 8 58 5 9

2. RDG-2 70 6 76 5 2

3. HOO-1 20 3 23 0 2

4. HOO-1B 15 2 17 0 0

5. HOO-2A 43 2 45 0 14

6. HOO-2B 44 2 46 0 4

7. HOO-2C 52 0 52 0 2

8. HOO-2D 72 0 72 2 11

9. HOO-3 70 1 71 0 2

10. SAU-5 48 1 49 0 3

11. SAU-5B 56 1 57 3 4

12. SAU-5C 62 2 64 1 4

13. SAU-6A 55 9 64 1 4

14. SAU-6B 78 2 80 0 7

15. SAU-8A 35 4 39 0 7

16. SAU-7 30 1 31 0 4

Table 4.2: Recalculated tabulated data from modal analysis Sample Sample ID Data for QFR diagram Data for QmFRt diagram no. Q F Rt Qmt F Rt 1. RDG-1 82 6 12 78 8 14 2. RDG-2 91 6 3 91 8 1 3. HOO-1 92 0 8 91 0 9 4. HOO-1B 100 0 0 100 0 0 5. HOO-2A 76 0 24 64 0 36 6. HOO-2B 92 0 8 92 0 8 7. HOO-2C 96 0 4 93 0 7 8. HOO-2D 85 2 13 87 2 11 9. HOO-3 97 0 3 97 0 3 10. SAU-5 94 0 6 94 0 6 11. SAU-5B 90 4 6 93 3 4 12. SAU-5C 93 1 6 94 1 5 13. SAU-6A 93 1 6 93 2 5 14. SAU-6B 92 0 8 88 0 12 15. SAU-8A 85 0 15 83 0 17 16. SAU-7 89 0 11 86 0 14

4.2.1. Quartz

Quartz is the most dominant framework constituent of the sediments in the present study and is identified by several distinctive features like undulose extinction, strained nature, crystal shapes, inclusions, etc. Both Monocrystalline, as well as Polycrystalline varieties of Quartz (Conolly, 1965; Blatt, 1967), is present in the sandstones. Quartz types are classified following Dotty and Hubert (1962) and Conolly (1965).

Monocrystalline Quartz is characterized by single-unit grain boundary. Unit Quartz and Unit Undulose Quartz are the two varieties of Monocrystalline Quartz seen in the samples. (Figure 4.2 a.)

Unit Quartz is also known as common or non-undulose quartz. Quartz grains, which show uniform extinction, may vary from 1° - 3°, which are called unit quartz. These occur as Rounded to Subrounded grains with straight and sutured grain boundaries.

Undulose Quartz is identified by their unit boundary and extreme Undulose extinction. Undulose extinction is wavy extinction sweeping from one end to another. Grain boundaries show straight or sutured nature. Undulose quartz is thermodynamically less stable than non- Undulose quartz and tends to break into small grains (Blatt et al., 1980).

Folk (1961) used the degree of undulatory extinction and the nature of polycrystalline grains to assign quartz to various presumed igneous and metamorphic parent rocks. suggested that most highly Undulose quartz (undulose extinction > ~ 5 degrees) is diagnostic of metamorphic rocks and nonundulose quartz is diagnostic of igneous rocks. Polycrystalline quartz was considered to be most indicative of metamorphic origin.

Polycrystalline Quartz is the Quartz grains that show two or more units under cross-nicols but look like a single grain under polarized light (Conolly, 1965). Some of the polycrystalline quartz grains are larger than monocrystalline quartz. The average number of internal crystal units varies depending upon the nature of the source rocks (Blatt et al., 1980; Basu et al., 1975). Polycrystalline quartz (Figure 4.2 b.) was considered to be most indicative of metamorphic origin. The varieties of Polycrystalline Quartz observed in specimens under study include:

Composite Quartz is Composed of many monocrystalline units having optically different extinction positions with straight-slightly curved inter-unit boundaries. (Figure 4.2b)

Schistose Quartz is characterized by the presence of a number of monocrystalline grains with sutured grain boundaries and a certain degree of parallel orientation of the constituent grains. (Figure 4.2c)

Pressure Quartz is identified by their mosaic-like appearance within a single grain under plane-polarized light and cross-nicols, constituent interlocking grains show undulatory extinction and crenulated boundaries (Figure 4.2, f.),

4.2.2: Lithic Fragments:

Lithic Fragments are the second important framework component of these Clastic Sedimentary rocks. These grains are the pieces of disintegrated source rocks and are of

immense importance in provenance study and tectonic setting of the source areas. Detrital rock fragments in sandstones and conglomerates provide the most unequivocal evidence of source-rock lithology. Rock fragments can be of igneous, metamorphic, and sedimentary origin. Metamorphic rock fragments are identified by their aggregate nature, preferred orientation, and high interference colour under cross nicols. Igneous rock fragments show black dotted nature under the cross nicols. Sedimentary rock fragments show some sedimentary characters. The Lithic Fragments in the studied samples are mainly showing Metamorphic signatures (Figure 4.2d). The average modal composition of Lithic Fragments is found to be 8.31%.

4.2.3: Feldspars:

Feldspar ranks third in dominance in the present specimens. The Feldspars are Plagioclase, Orthoclase, and Microcline, of which mainly Plagioclase and Orthoclase are observed in the studied samples. These grains are medium-grained, mostly subhedral in shape. The identifying character of Plagioclase feldspar is lamellar twinning (Figure 4.2e). Orthoclase is mostly untwined and gives a cloudy appearance. The Feldspars are fresh to weathered in nature. The modal percentage of the feldspars varies from 0% - 8%.

4.2.4: Matrix and Cement:

Cements are authigenic minerals that fill interstitial areas that were originally open pore spaces. Cement crystals may be any size up to or larger than the sizes of the individual pores they fill. A single crystal of calcite, for example, can fill several adjacent pores. Cements visible under a petrographic microscope rarely make up more than about 30 percent of the total volume of sandstones and commonly are much less abundant.

Cement is chemically precipitated materials within the intergranular spaces that binds the grains in clastic rock like sandstone. The various types of cement are the critical constituents of sandstones. In the present samples of Saundatti Quartzite Member, the cement is dominantly siliceous (Figure 4.4a). Cement is also observed to be occurring as an overgrowth on detrital quartz grain where the grain's original boundaries can be seen under plane-polarized light. Ferruginous Cement (Figure 4.4b) is also observed in some specimens.

The matrix consists mainly of fine-size quartz, feldspars, micas, and clay minerals, which likely form diagenetically by alteration of detrital feldspars and rock fragments. With

regards to matrix the studied specimen contains very minor amounts of matrix and few of them are observed to be matrix free. The matrix in the rocks consists of both the detrital and the authigenic constituents of argillaceous and siliceous materials. The grains with 0.03 mm diameter or less, without grain boundaries trapped within framework grains, are defined as the matrix. The Studied samples of Saundatti Quartzite Member are devoid of any Matrix where the grains are observed to be held by some cementing material.

4.2.5: Clay Minerals:

Kaolinite and Chlorite are the main clay mineral species observed in the sandstones. Kaolinite is the simplest clay mineral in structure and the purest in composition. It is formed from feldspars both by hydrothermal alteration and by superficial weathering. Kaolinite dominates over Chlorite in terms of abundance. Kaolinite often undergoes considerable crystallization during diagenesis to form characteristic ‘book’ form. Aggregates of long accordion or worm-like crystals are also observed under some specimens. As observed under SEM, samples of Saundatti Quartzite Member show Kaolinite occupying the intergranular spaces between framework grains (Figure 4.3a). Kaolinite is present in various forms, including Vermiform (Figure 4.3b), Book shaped, well crystallized, and blocky forms (Figure 4.3 c). The predominance of Kaolinite with little or no Illite indicates the sedimentary origin under continental conditions (Lonnie 1982, Tsuzuki and Kawabe 1983).

4.2.6: Accessory Minerals:

These heavy minerals are seen to constitute a small percentage of the detrital constituents of sandstones, particularly the chemically stable heavy minerals such as zircon, tourmaline, and rutile. These include the minerals which can be divided into opaque and non-opaque minerals. Heavy minerals present in the samples were observed under thin sections and Scanning Electron Microscope images. These heavy minerals include Zircon (colourless to pale grey), Tourmaline (brown, greenish-brown, yellow and green) (Figure 4.3 e), Rutile (blood red), and Sphene. (Figure 4.3f). Grains of heavy minerals are very fine and show moderate abrasion.

4.3. Texture: Sediment texture refers to the shape, size, and three-dimensional arrangement of the particles that make up the sedimentary rock. Particle size distribution of a clastic sedimentary rock is sensitive to the transporting media's physical changes and the depositional basin. Systematic presentation and analysis of grain size data provide the basis for reconstructing sedimentary processes, including identifying the depositional environments. Texture is an important aspect in the description of sedimentary rocks and can be useful in interpreting the mechanisms and environments of deposition. It is also a major control on the porosity and permeability of a sediment. Various Textural parameters for sediments of Saundatti Quartzite Member was calculated and given in Table 4.3. A description of each of the parameters is presented here.

Table 4.3: Detailed textural data of Sandstone samples of Saundatti Quartzite Member. Sr. Sample Mean Median Standard Skewness Kurtosis no. Id Mz deviation SkI KG σI 1. HOO- 0.91 0.81 0.54 MWs 0.48 Fine 0.41 Leptokurtic 1B Skewed 2. HOO- 1.66 1.30 0.56 MWs -0.36 Very -0.72 Platykurtic 2A Coarse Skewed 3. HOO- 1.82 1.82 0.31 Very - Near 0.30 Platykurtic 2C Ws 0.075 symmetrical 4. HOO- 1.56 1.56 0.42 Ws -0.31 Very 0.76 Platykurtic 2D Coarse Skewed 5. HOO-3 1.23 1.19 0.35 Ws 0.11 Near 0.13 Platykurtic symmetrical 6. KDG- 1.54 1.59 0.43 Ws -0.41 Very -0.73 Very 1A Coarse platykurtic Skewed 7. RDG-2 1.02 0.98 0.61 MWs -0.22 Coarse -0.16 Very Skewed platykurtic 8. SAU-1 1.60 1.51 0.51 MWs -0.34 Coarse -0.67 Very Skewed platykurtic 9. SAU-2 2.06 2.05 0.29 Very 0.01 Near -0.20 Very Ws symmetrical platykurtic 10. SAU-5 1.49 1.44 0.47 Ws 0.31 Fine -0.09 Very Skewed platykurtic 11. SAU- 1.15 1.16 0.33 Very -0.02 Near 0.23 platykurtic 5C Ws symmetrical

12. SAU- 1.11 1.07 0.36 Very 0.36 Very -0.54 Very 6A Ws Coarse platykurtic Skewed 13. SAU- 1.37 1.38 0.34 Very 0.08 Near - Very 6B Ws symmetrical 0.038 platykurtic 14. SAU- 0.99 0.99 0.55 M -0.21 Coarse 0.46 platykurtic 8A Ws Skewed 15. SAU- 1.24 1.87 0.54 M 0.24 Coarse -0.87 Very 8B Ws Skewed platykurtic

(Mz-mean size, σI-standard deviation, SkI-skewness, KG-kurtosis, Ws- Well sorted, MWs- Moderately well Sorted)

Table 4.4: Textural data of Sandstone samples of Saundatti Quartzite Member. Sr. no. Sample Avg. grain Wentworth Grain Grain Grain No. size (in mm) scale term roundness Sorting Contact 1. RDG-1 0.25-0.5 Medium R-SR M-Ws L, S sand 2. RDG-2 0.25-0.5 Medium R-SR M-Ws L sand 3. HOO-1A 1.0-1.5 Very coarse SR-SA Ms L,S sand 4. HOO-1B 2.0-2.5 Very coarse SA Ms L sand 5. HOO-2A 0.5 Medium SR-SA Ws L,S,C sand 6. HOO-2B 1.0-2.0 Very coarse SA Ms L,C sand 7. HOO-2C 0.25 Medium SA Ws L, S sand 8. HOO-2D 0.5-1.0 Coarse sand SA M-Ws L,S 9. HOO-3 0.5-0.75 Coarse Sand SR Ws L.S 10. SAU-5 1.0 Coarse Sand SA Ms L 11. SAU-5B 0.5 Medium SA M-Ws L,S sand 12. SAU-5C 0.5-1.0 Coarse Sand SR-SA Ws L,S,C 13. SAU-6A 0.5 Medium SR Ws L,C sand 14. SAU-6B 0.5-1.0 Coarse Sand SA Ws L,S 15. SAU-8A 1.0-1.5 Very coarse SR Ms L sand 16. SAU-7 1.0-1.5 Very coarse SR-SA Ms L,C sand

SA= Sub Angular, SR= Sub Rounded, R=Rounded, Ws= Well Sorted, Ms= Moderately sorted, M-Ws= Moderately well sorted, L=Long contact, S=Sutured contact, C=Concave- convex contact 4.3.1: Mean

Mean represents the average size of the total distribution of sediments. It serves as an index to measure nature as well as the depositional environment of the sediments. It is the function of the total amount of sediment available, the amount of energy imparted to the sediments, and the transporting agent's nature. The energy of the transporting agent includes the degree of turbulence and the role played by currents and waves.

The mean size of the present sandstone samples from the study area ranges from 0.91 φ to 2.06 φ, indicating a medium-grained size.

4.3.2: Standard Deviation

Standard deviation is a measure of uniformity or sorting. It is also the resultant character of sediments controlled by size, shape, specific gravity of sediments, energy, and time involved in transporting fine-grained sediments. Cadigan (1961) states that the function of sorting is inversely proportional to the standard deviation. The sorting of sediments is controlled to a certain extent by the size distribution of the source material. It is observed that the standard deviation decreases with the decrease in mean size. In other words, the sorting improves with the lowering of mean size. As a result, the sediments having fine sand exhibit well- sorted nature. (Table 4.3)

The standard deviation value for sandstone ranges from 0.29 φ to 0.52 φ, indicating a very well sorted to moderately well-sorted nature in the study area. The well-sorted nature indicates deposition in a place where there is a continuous, slow deposition of sediments.

4.3.3: Inclusive Graphic Skewness:

It measures the asymmetry of the frequency distribution and marks the deviation mean from the median. If there is more material of the sample in the coarse tail of the graph, the sample is coarsely skewed; the skewness is referred to as negative skewed if the mean is towards the coarser side of the median. On the other hand, if more material of the sample is in the fine tail of the graph, the sample is finely skewed, and the skewness is referred to as positive skewness.

The inclusive graphic skewness ranged from – 0.41 φ to 0.48 φ, reflecting that the sands are coarse to very Coarse skewed with some specimen showing near Symmetrical skewness. In a fine skewed sediment population, the distribution of grains will be from coarse to fine, and the frequency curve chops at the coarser end and tails at the finer. The reverse condition is characteristic of sediments, which are coarsely skewed. (Table 4.2)

4.3.4: Inclusive Graphic Kurtosis:

It measures the ratio between sorting in the tails of the frequency distribution and the sorting in the central portion of distribution or it is a ratio of sorting within the central 90% of the distribution to the central 50% of the distribution. Cadigan (1961) defines kurtosis as, the measure of peakedness or broadness of the curve, would be affected by deviations near the center of the distribution. The kurtosis values are similarly a function of standard deviation and are inversely proportional to it.

For a normal distribution, the kurtosis is unity, and if a value of kurtosis is greater than unity, it then indicates that the velocity of fluctuations was restricted within the central 50% of the average velocity. Kurtosis values of the Saundatti Quartzite sediments vary from – 0.87 φ to 0.46 φ, suggesting platykurtic to the very platykurtic distribution of sediments.

4.3.5: Textural Maturity:

Folk (1961) defined textural maturity as a degree to which sand is free of interstitial clay and is well sorted and well rounded. The final depositional environment controls textural maturity. Thus, a well-rounded, well-sorted, clay free shelf sands may be mixed deep water clay fractions to produce framework textural inversions.

Folk (1961) subdivides the textural maturity into four stages:

i. The immature sands having > 5% clay, poorly sorted, angular grains. ii. ii. The sub-matured sands having 5% clay, moderately sorted, subangular to subrounded grains. iii. The mature sands are having less than 5% clay and rounded grains. iv. The super mature sands in which the clay fraction is almost absent and the grains are well-sorted and well rounded.

Accordingly, the present sediment samples of the Saundatti Quartzite Member can be classified as mature, where the clay fraction is around 5% or less and are well to

moderately well sorted. The grains are rounded to subrounded, which clearly displays their textural maturity.

4.4. Classification: Various workers have proposed different classification schemes to classify sandstones based upon their textural and Mineralogical parameters. Most of these use Triangular plots with Quarts, Feldspar, and rock fragments as End members. The triangular plot is divided into various fields, and rocks with a specific modal composition falling within a particular field are given a specific name. Dott (1964) gave an accepted and most widely used scheme for the classification of sandstone. Pettijohn et al. (1987) later modified this scheme. This classification scheme is simple and can be applied for both ancient and modern sediments because it uses mineralogy of both framework grains and matrix. This scheme is represented by three ternary diagrams with three end members i.e., Quartz, Feldspar, and Rock Fragments. Based on matrix percentage, Arenaceous rocks are classified into three major groups. If the matrix percentage is less than 15%, then the rock is classified as Arenite. If the matrix percentage is more than 15% to 75%, then the rock is classified as Wacke. Mudstones are the rocks that have more than 75% matrix. These are represented in the First, Second, and third Triangular plots, respectively.

As all of the samples collected from the study area have less than 15% of the matrix, only the first ternary diagram has been used to classify these samples. According to this classification, Arenaceous rocks of the study area falls under the Arenite group. For further subdivision of these Arenites, the percentage of Quartz, Feldspar, and Rock fragments obtained from the modal analysis are plotted in a Triangular diagram. Depending upon the relative proportions of Quartz, Feldspar, and Lithic Fragments, the group is further subdivided into categories like Quartz Arenite, Subarkose Arenite, Sublithic Arenite, Feldspathic Arenite, and Lithic Arenite. These plots indicate that Saundatti Quartzite Member's samples can be classified as Quartz Arenite and Sublithic Arenite.

Quartz Arenite:

Quartz arenites are composed of > 90–95 percent siliceous grains (quartz, chert, quartzose rock fragments). The rock in the present study are observed to be well lithified and well cemented with silica or ferruginous cement. Quartz arenites typically occur in association with assemblages of rocks deposited in stable cratonic environments such as eolian, beach,

and shelf environments. According to Folk’s (1951) textural maturity classification, most quartz arenites are texturally mature to super mature however the ones under present study are mostly identified as matured.

4.5. Diagenesis: Diagenesis is a process of compaction and lithification and cementation. It is any chemical, physical or biological change undergone by the sediment after its initial deposition and during and after its lithification. Dapples, (1962). The term 'Diagenesis' was first introduced in 18read88 by Von Gumbel (Pettijohn, 1984). It includes the many post-depositional processes that alter sediment to rock, sand to sandstone. Hence, Diagenesis is a complex and lengthy process that converts newly deposited sediments into hard and compact sedimentary rocks.

Diagenesis of sandstones depends upon pressure, temperature, porewater chemistry, fluid influx, sand-shale ratio, texture and mineralogy of the rocks and time (Blatt et al., 1980). Diagenetic processes are generally temperature controlled. Many of these factors appear to have been related to the pre-burial tectonic setting, provenance, and depositional environment (Mc Bridge, 1985).

The studies done by Siever (1979), Read and Watson (1962), Dapples (1972), Fairbridge (1983), Singer and Muller (1983), Tucker (1989) discuss that diagenesis embraces all those processes, which begin at the moment when a sedimentary particle comes to rest and continues to the point of deep burial and orogenic buckling that cause the initiation of metamorphism, or when emergence leads to exposures and the initiation of weathering and erosion. These include compaction, cementation, authigenesis, mineral replacement, and dissolution of pre-existing phases that occur at a temperature of 200°C - 300°C and 1 kb pressure.

Cementation refers to the precipitation of minerals into the sediment's pore space, thereby reducing the porosity and bringing out lithification of the sediment. Silica cement is the most common; however, feldspar, iron oxide, pyrite, and many other minerals may also form cement. Quartz cementation is favored by a high concentration of silica in pore waters and by low temperatures. Silica may also be imported from other areas of the sedimentation basin during tectonic activity. Dissolution of framework silicate grains may occur during deep burial under conditions that are essentially the opposite of those required for

cementation. Rock fragments and low stability silicate minerals, such as plagioclase feldspar, pyroxenes, and amphiboles, may dissolve out due to increasing burial temperature and the presence of acidic pore water. Selective dissolution of less stable framework grains or parts of grains takes place during diagenesis by intrastratal solution. The dissolution of framework grains and cement increases porosity, particularly in sandstone, which occurs through intrastratal solution activity.

Compaction during diagenesis starts at the sediment-water interface and proceeds with further sedimentation over it, resulting in mechanical compaction till the large-scale stresses come into play during basin subsidence and basinal tectonics resulting in chemical compaction. The chemical Compaction involves the pressure dissolution of grains along contacts and the formation of stylolites (Heald, 1955). Mechanical compaction is perhaps the dominant diagenetic process during the early stage of diagenesis, which results in the rearrangement of the framework grains forming long and sutured contacts. (Figure 4.4d)

Three types of grain contacts are predominantly observed in the sandstone samples under the present study. These include straight contact, concavo-convex contact, and sutured contacts. (Figure 4.4 d) The compaction brings the grains into closure contacts or concavo- convex boundaries. Under more usual conditions, the sandstones' point or tangential contacts suggest early burial stage of diagenesis that on the increase of overburden load under deep burial stage, come into closure contact along long and concavo-convex grain boundaries (Blatt, 1980). Taylor (1964) attributed this change to the intrastratal solution and precipitation effect. The study reveals that the sandstones with a higher frequency of concavo-convex and sutured grain contacts indicate a moderate pressure solution. Blatt et. al (1980) explained that at a depth of burial or during phases of marked tectonism, the buried loaded sand may have a much higher proportion of closer, long and concavo-convex and sutured grain contacts.

Cementation is the process whereby new minerals are precipitated as a syntaxial overgrowth in detrital 'seeds' or as authigenic phases into the pore spaces from intraformational fluids (Ahmad and Sayeed, 2004). The cementation in clastic sediments generally leads to loss of porosity. Two main types of cementing material observed in Saundatti Quartzite Member include Silica and Ferruginous types of cement. The silica cement occurs in the form of quartz overgrowth around detrital grain boundaries. Quartz overgrowth may be formed from the pressure solution of quartz (Heald, 1955; Dapples, 1972; Morris et al., 1979). The source

of silica cement may be the descending meteoric water saturated with silica or pressure solution of detrital quartz and other silicates at grain contacts. Decomposition or alteration of feldspars during diagenesis may release silica saturated solutions (Mc Bridge, 1989).

: Ternary diagram for classification of Arenaceous rocks of Saundatti Quartzite Member rocks Saundatti of of classification matrix with Quartzite for Arenaceous diagram Ternary : less than 15% (Pettijohn 1984, modified after Dott (Pettijohn 1964) after modified 1984, 15% than less 4.1 Figure

Figure 4.2 Photomicrographs – Petrography

4.2 a: Clasts of Monocrystalline Quartz in 4.2 b: Grain of Polycrystalline composite moderately well sorted Arenite. Quartz seen in sample collected from Savadatti.

4.3 c: Polycrystalline Schistose Quartz grain. d: Grains of Lithic Fragments as seen sample (lower center) from Hooli Village.

4.2 e: Grain of Plagioclase Feldspar seen 4.2 f: Grains of Pressure Quartz seen as forming framework constituent in one of the framework grains in sample collected from samples. (upper right) Savadatti. (lower left)

Figure – 4.3 Photomicrographs – Accessory Minerals

a. SEM image showing Intergranular spaces b. SEM image of Vermiform overgrowth of occupied by Kaolinite Kaolinite seen in Void spaces

c. SEM image showing well developed d. Distinct greenish to yellow colored specs of crystal faces of Kaolinite Chloritoids, note flowage around quartz grains

e. Slender prismatic habit of Tourmaline f. Pale green, characteristic wedge-shaped grain grain of Sphene

Figure – 4.4 Photomicrographs- Diagenesis

a. Quartz overgrowth around detrital grains. b. PPL image of well sorted Arenite with Original grain boundaries can also be seen. brownish ferruginous cement

c. Arrows showing corroded grain boundaries d. Framework grains exhibiting Sutured contacts filled by clay minerals precipitated secondary in Sample collected from Lokapur minerals

e. Long contact observed along with deformation f. Subrounded grains of Quartz appearing as fractures seen in Sample from Hooli Village framework constituent in Sample collected from Savadatti.

CHAPTER 5: CARBONATE

PETROGRAPHY AND

DIAGENESIS

5.1 Introduction:

Petrography is the most effective way of knowing the mineralogical and other constituents of carbonate rocks. The primary aim of petrography is to identify the framework composition and their interrelationships to know its origin. Carbonate sediments and rocks preserve valuable information regarding the physical, chemical, and biological conditions that have prevailed during the deposition and post-depositional conditions that have passed through it. The texture and composition of limestones and their progressive development in characteristic forms are very important. Thus, the study of carbonate rocks is impressive compared to that of clastic rocks. The limestone's texture and composition reveal as much about the depositional setting as that of any clastic sedimentary rocks viz., sandstone, conglomerate, and breccia. Besides broken or whole skeletal material, many limestones contain composite grains (ooids and intraclasts) formed of an interlocking mosaic of calcite or aragonite, which often experience a history of transport and deposition as clasts.

Limestones, as well as the Dolomites, make up the Carbonate units in the present study area. All limestones are generally hard and compact and often bedded in character and display a considerable variation in the color, white, grey, black, and variegated. The dolomites/dolomitic limestone generally thin-bedded/nodular and buff, pale grey to dark grey and is often seen traversed by Quartz veins. Stromatolite structures (Figure 5.2 a,b) of various types are seen in only the dolomitic rock units. No other depositional structures are observed in the carbonate rocks. The primary depositional structures (Current bedding, graded bedding, ripple marks, etc.) are observed only in the associated clastic rocks. Most of these carbonate units are highly disturbed and folded and display deformational structures.

The study area is dominated by clastic sequences, however large area is covered by extensive carbonate sequences that cap the underlying clastics. The Present study is restricted only to five litho units representing limestone and dolomite sequences of Lokapur Subgroup. These are exposed at various locations in Proterozoic Kaladgi Basin. The important locations where outcrops are present include Lokapur, Chitrabhanukote, Chiksellikeri, Kaladgi, Bagalkot, Petlur, and Nagnur.

A total of 50 thin sections of Carbonate thin sections were studied using a petrological microscope to understand framework elements, texture, depositional facies, and nature of the diagenetic modification. These carbonate samples were stained with a 2 % dilute HCl

solution of Alizarine red-S to distinguish calcite from dolomite. The staining test has revealed that the majority of the sections show the presence of dolomite and calcite. The detailed mineralogical studies were carried out by XRD analyses; the results of the same are discussed in this Chapter.

5.2. Fabric and Texture:

The study of the microstructure of any Carbonate rock is vital as it gives insight into the chemical activity and mode of occurrences within the carbonate sediments. The term 'fabric' and 'texture' were coined by Friedman (1965) for diagenetically altered rocks. Usually, the calcite grains are subhedral, and the carbonate minerals and quartz occur as anhedral grains.

The limestones from the study area are in general fine to medium-grained, pale to deep grey, hard, compact in hand specimens, and exhibit a typical non-clastic crystalline texture consisting of interlocking crystals molded to each other as in a mosaic. The individual crystals are smooth and regular to jagged and irregular in outlines. The individual calcite crystals are subhedral to anhedral in habit, whereas the dolomite crystals show subhedral to euhedral forms. The dolomitic limestones and dolomites varieties have variable crystal sizes. They show a typical xenotropic texture with non-planar, tightly packed subhedral dolomite crystals with curved, serrated, or otherwise irregular intercrystallite boundaries. (Figure 5.3)

5.3 Carbonate Petrography and classification:

The carbonate rocks of five different litho units of Lokapur Subgroup have been critically examined under the microscope. They are described in detail concerning their microfacies classification, depositional and diagenetic properties. Carbonate rocks are composed of two elements, which include the allochemical and the orthochemical particles. Allochem particles are the main framework elements that are deposited in any marine basin. These elements are bounded together to form carbonate rock by the syndepositional or post- depositional material called cement and matrix, which are the orthochemical particles. During diagenesis, both these particles get highly modified, resulting in changes in their composition and texture with different environmental setup. The present carbonate samples are devoid of any carbonate allochems (except in some cases a few detrital quartz, feldspar, etc.), and all these carbonate rocks can be categorized as orthochemical carbonate rock types with variable mineralogy and texture. The popular classifications of Carbonate rocks of Folk

(1961) and Dunham (1962) could not be applied for these rocks as hardly any depositional texture is preserved.

The orthochemical particles are matrix or cement precipitated from the seawater and the interstitial solutions. These orthochemical particles are generally aragonite or high Mg calcite in the carbonate sediments, and then these particles are modified into different morphologies and have characteristic textural patterns. Accordingly, early diagenetic and late diagenetic types of cement have different textures and mineralogy. Usually, orthochemical particles show low Mg-calcite mineralogy in the ancient carbonate sediments since both aragonite and high Mg-calcite are metastable.

Based on the general field characters, three distinct varieties of limestones and two varieties of dolomites have been identified. The three distinct limestone types include the dark grey limestone, pale grey to yellow limestone, and variegated limestones. Dolomitic limestones /dolomites are represented by the types associated with stromatolitic structures and the other ones with chert.

Petrographically, carbonate rocks from the present study can be categorized into Micrites, Biomicrites, Algal laminated biomicrites, and dolomicrites/sparite varieties.

5.3.1. Micrites (finely crystalline calcitic limestones):

These petrographic varieties are represented by the clear calcite grains of 1-4mm in diameter, sub translucent with a faint brownish cast in thin sections, which have been subjected to considerable compaction. (Figure 5.3)

Folk (1959) used the term 'Micrite' for microcrystalline calcite and are 'clay-sized carbonate' materials measuring 1 to 4 microns in size. It is basically a Carbonate mud. The upper size limit of micrite is variously taken as 0.03-0.04 mm in diameter. Materials of 5 to 10 micron (or even 50 microns) were termed microspar. Micrite may be present in small quantities as a matrix within a grain-supported carbonate sand, or may be so abundant that it forms a carbonate mudrock, termed "micrite" or "calcilutite". Micrite can also form as a cryptocrystalline cement in certain circumstances. Because of this it must be used with care as an index of depositional energy. In hand specimen, micrite is a dull, ultrafine-grained material ranging from white through grey to black. Under a petrological microscope, it is sub-translucent and a fine brownish. Grey micrite is considered to form by rapid chemical

or biochemical precipitation of the seawater, settling to the bottom and, at times, suffering some later drifting by weak currents (Folk, 1951).

5.3.2. Biomicrites

The Biomicrites also comprises of finely crystalline calcitic matrix with suspected organic particles of doubtful nature, which are seen as dark, rounded particles that are identifiable. (Figure 5.3c)

5.3.3. Algal laminated biomicrites

These types display a fine-scale lamination of alternating algal and micrites. The overall grain size of these carbonate varieties is also fine-grained. (Figure 5.3c)

5.3.4. Dolomircites and sparites

These types show a variable crystal size and show a typical xenotopic texture with non- planar, tightly packed subhedral dolomite crystals with curved, serrated, or otherwise irregular intercrystalline boundaries. (Figure 5.3e, f)

Friedman and Sander (1967) used the term 'spar' for its relative clarity both in thin section and hand specimens, which distinguishes it from the microcrystalline calcite matrix. Sparry calcite (spar) distinguished from micrite by its clarity and coarser crystal size, which may range up to 10 microns or more and occur as pour filling cement. Sparry calcite matrix is a clear, coarsely crystallized material showing well-defined grain boundaries and often displays cleavage traces. The grain size or crystal size of sparry calcite (spar), depends upon the size of the pore space and rate of crystallization.

5.4. Identification of Carbonate Minerals

In Carbonate rocks, either formed by chemical or mechanical deposition Calcite (CaCO3),

Dolomite (Ca Mg (CO3) 2), and Aragonite (CaCO3) constitute the main rock-forming minerals. According to their crystallographic characteristics, Carbonate minerals are categorized into two groups: The Calcite group and the Aragonite group.

Calcite and Dolomite are the two dominant Rhombohedral minerals of the Calcite group found in Sediments. Based on its purity or Iron and Magnesium content, Calcite can be found pure calcite, ferrocalcite, and magnesium calcite. Likewise, depending upon its Iron content,

Dolomite can be called as pure dolomite and ferrous dolomite based on its proportion. The other calcite group minerals include Ankerite [CaFe(CO3)2], Magnesite (MgCO3), Siderite

(FeCO3), Smithsonite (ZnCO3), Rhodochrosite (MnCO3) and Spherocobaltite (CoCO3).

Aragonite (CaCO3) is the most important mineral in the Aragonite group. The other minerals in this group include Witherite (BaCO3), Strontianite (SrCO3), Cerussite (PbCO3), and

Alstonite [(Ba,Ca) CO3]. The optical and Crystallographic characteristics of Carbonate minerals are almost similar to each other, making their identification in hand specimen and even in thin sections rather tricky. In such a situation, the Refractive Index becomes the only property by which these minerals can be identified precisely. The determination of R.I.'s can be carried out by the oil-immersion method. The identification and discrimination of carbonate minerals in hand specimens or thin sections are made easier by using simple chemical staining methods.

The present Proterozoic limestone and dolomite samples of Kaladgi Super Group have been subjected to mineralogical analysis using an initial acid etching and staining to identify carbonate minerals, and the detailed mineralogical analysis is done by using X-ray Diffraction analysis.

5.4.1: X-ray diffraction analysis

In the present study, the carbonate fraction of limestone has been powdered to 400 phi size. The powdered samples have been analyzed at the laboratories of NIO-Goa, using the Philips X-ray diffractometers, respectively.

The following specifications have been used for the analysis: - Target: CuK & Fe; Scanning speed: 2cm/min.; scanning range of 2Ɵ: 20 to 35.

The 2Ɵ values of various characteristic peaks (Figure 5.4, 5.5) identified have been converted to respective d-spacing values using the conversion tables given in Carver (1971). The peak heights have been measured, and the relative intensities of peaks are calculated by taking the strongest peak as 100%. The d-spacing values and corresponding relative intensities have been compared with the JCPDC powder data files for the identification of different mineral phases. The results are given in Table 5.1.

Table 5.1: Results of X-Ray diffraction analysis and interpretation.

Sample no. 2Ө d I/I Mineral

Sam-L-8 29.46 3.030 100 Calcite

30.94 2.886 100 Dolomite

Sam-L-20 29.5 3.030 100 Calcite

Sam-L-22 29.4 3.030 100 Calcite

26.62 3.343 100 Quartz

39.42 2.945 20 Calcite

Sam-L-24 31.00 2.834 <5 Calcite

Sam-L-23 30.94 2.886 100 Dolomite

41.12 2.198 30 Dolomite

26.64 3.343 100 Quartz

Sam-L-26 30.9 2.886 100 Dolomite

41.16 2.192 30 Dolomite

Sam-L-27 29.42 3.030 100 Calcite

Sam-L-30 29.44 3.030 100 Calcite

Sam-L-11 29.4 3.030 100 Calcite

Sam-L-12 29.44 3.030 100 Calcite

30.94 2.886 100 Dolomite

Sam-L-18 30.98 2.886 100 Dolomite

5.4.2: Determination of Calcite – Dolomite ratio:

Calcite and dolomite concentrations were estimated using a working curve drawn with pure standards. All samples contain only two carbonate minerals viz., calcite, and dolomite. From the measured peak intensity ratio of calcite/dolomite (Ci/Di), the weight percent of dolomite in the sample is calculated using the working curve given in Carver (1973) and following the procedures by Lowenstein (1954). The Data of X-Ray Diffraction analysis of Carbonates of Kaladgi basin are presented in Figure 5.4, 5.5 and Table-5.1.

5.4.3: Results a) Calcite: This is one of the carbonate minerals in the present samples in the carbonate fraction. It gives its characteristic d-spacing of 3.023, 2.837, 2.508, 2.485, and 2.103. a) Dolomite: Dolomite is identified in the rocks based on its characteristic peaks, and the quantitative estimation of dolomite gives a range of 12 to 58%. c) Other non-carbonate minerals: Quart, feldspar, mica are the other detrital non-carbonate minerals identified from XRD charts.

5.5. Geochemistry of Carbonate rocks

The study of the bulk chemical composition of sedimentary rocks can be a useful tool to infer the factors that controlled sediment characteristics during and after their deposition. Bulk chemical composition of sedimentary rocks has been widely used to delineate specific units of clastic and carbonate strata.

Chemical studies of ancient carbonate rocks (Veizer and Demovic 1974) have shown that their composition is facies controlled. This is particularly true for elements and isotopes associated with carbonate lattice (Veizer et al. 1978). Such chemical criteria may only be of supplementary importance in Phanerozoic rocks with abundant biota, but they may be indispensable for interpretation of unfossiliferous, particularly Precambrian carbonates. Furthermore, the knowledge of variations in the chemical composition of particular facies will aid in the quantitative reconstruction of diagenetic history. Modification of trace element chemistry during diagenesis serves as an important clue to the lithification process. For any element, one must consider the possibility that diagenetic fluids did not introduce

it, but somewhat derived from local non-carbonate minerals and redistributed on a small scale during diagenesis (Banner and Hanson 1990).

The carbonate samples of Kaladgi Basin are composed of various mineral and chemical components that may have similarities and dissimilarities in behavior due to varying conditions. In such cases, it is most appropriate to discern the relationships and variability of these components in rocks for their geochemical behavior using various statistical methods such as correlation analysis, etc.

5.5.1: Analytical Methodology

In the present study, the limestone samples have been wholly or selectively analyzed for selected major, minor, and trace and REE elements to know their relative abundances and the distributions. The following procedure of sample decomposition and analysis has been used: To obtain the sample solutions, powdered samples of 0.2 gm. are dissolved in 3% (8% v/v) HCl for three and half hours. After this length of time, the insoluble residue was extensively leached, and the non-carbonate insoluble have been separated by filtering. The carbonate solution aliquots have been made and diluted to the required volumes. The diluted aliquots have been analyzed for the various elements as follows:

i) CaO and MgO have been determined by EDTA titration method,

ii) XRF determined the major Oxide composition of the carbonate samples

iii) Selected trace and rare earth elements have been analyzed using ICP-AES at the laboratories of National Institute of Oceanography, Goa,

iv) Insoluble residue content has been determined by acid digestion method using a 15 % HCl solution.

5.5.1.1: Data Presentation

The data on the various chemical parameters of samples from the Kaladgi basin analyzed by the above methods is presented in Table 5.2. The vertical variation of chemical parameters (Oxides, Trace/minor elements, REE) are shown in Figs. 5.7 and 5.8.

Table 5.2: Stratigraphic Distribution of Average values of Major Oxide Components

Carbonate Unit SiO2 Al2O3 TiO2 Fe2O3 MnO MgO CaO Na2O K2O P2O5

Bamanbudni 15.290 3.208 0.138 1.320 0.012 9.365 31.596 0.238 1.535 0.042 Dolomite

Petlur 8.926 0.549 0.024 0.369 0.012 10.452 36.390 0.089 0.181 0.010 Limestone

Nagunur 9.636 1.016 0.041 0.517 0.001 0.600 47.875 0.127 0.280 0.034 Dolomite

Chiksellikeri 2.825 0.516 0.026 0.402 0.020 3.470 49.220 0.112 0.391 0.038 Limestone

Chitrabhanukot 16.183 4.339 0.236 3.065 0.006 11.602 25.376 0.098 1.974 0.049 Dolomite

5.5.1.2: Data Interpretation

The correlation analysis of chemical data of Kaladgi samples reveal the following significant correlations:

i) Ca shows a significant negative correlation with Mg, Fe, Mn, Na, and IR while positively correlated with Sr,

ii) Mg is positively correlated with IR, Fe, Mn, and Na and negatively linked with Sr,

iii) Fe is positively related with Mn, IR and Na and iv) Sr negatively correlated with Mg, IR, Fe, and Mn and shows no correlation with Na.

5.5.2: Major and selected Minor elements

Ca, Mg and Insoluble Residue (IR)

In recent years considerable attention has been paid to understanding the relationship between Ca, Mg, and IR contents of the limestones. These studies have indicated that a direct relationship between Mg and IR contents and an inverse relationship of Ca with Mg and IR. The present study on carbonate samples of Kaladgi confirms the above relationship between Ca, Mg, and IR (Table 5.3). The positive correlation of Mg with IR (r=0.5364, Table-7.2) is attributed to the selective leaching effect of Ca by the primary solution resulting in the enrichment of Mg and IR (Chilingar et al., 1979). The negative correlation between Ca and

Mg confirms the above view. The significant positive correlation of IR with Mg suggests that IR acts as a barrier (or membrane), preferentially concentrating Mg from the entrapped interstitial solutions squeezed out during syn diagenetic and late diagenetic stages of diagenesis.

In general, in the present samples, CaO varies between a very narrow limit. In contrast, MgO shows a relatively more significant variation (Table 5.1), which can be attributed to the variation in dolomitization. The significant factors that influence the Mg content are mineralogy, water, and type of organisms living, factors such as salinity, water depth, and size of individual organisms as secondary (Chave, 1954). The most crucial factor that controls the amount of Mg in the present samples is the shell mineralogy of organisms. Because of the large amount of terrigenous material and low aragonite content, the variation of Mg with mineralogy could not be seen in the present samples, since the substantial contribution from detrital materials masks such small variations.

Fe and Mn

The first order control for the abundant Fe in limestones of all ages is provided by the iron oxide coatings of clays and various carbonate particles. The substitution of Fe for Ca and Mg play a secondary role with dolostones showing a higher concentration of Fe than in limestones (Veizer, 1978). In the present study, the negative correlation between Ca and Fe and a significant positive correlation of Mg with Fe supports the above view.

The distribution of Mn is substantially analogous to that of Fe, which could suggest a common source for the two elements undergoing uniform weathering that could have freed Mn and Fe in more or less constant proportions (Turi et al., 1990). The positive correlation of Fe with Mn (r=0.3452) in the present samples is in agreement with the above explanation. In general, the Fe content decidedly increases with an increase of clay fraction in the samples (Turi et al., 1990). It is also possible to note that dolomitization makes the Fe content increase sharply. Turi et al. (1990) have also observed that the Mn is associated mainly with the carbonate fraction, while Fe is associated with clay fractions.

Fe and Mg's present samples show a clear significant positive correlation indicating that the Fe increases with an increase in Mg content. Further, the positive correlation of Fe with IR suggests the association of Fe with a non-carbonate fraction. However, the significant negative correlation of Mn with Ca does not support the association of Mn with the carbonate phase.

Strontium

Sedimentary geochemists prefer to use Sr as a tool for facies analysis; petroleum geochemists use Sr to identify oil basins associated with carbonates. Generally, Sr concentration is more in seawater than in freshwater, and therefore, it reflects the nature of depositional basin water characteristics. Sr content in the present samples ranges from 485 to 1611 ppm (Table-7.1). The Sr/Ca ratio ranges from 1.39 X 10 to 4.61 X 10. In purely aragonitic corals, this ratio is identical to that of seawater, i.e., equal to 2 X 10, and the Sr concentration is 8000 ppm. In pure calcite, the Sr concentration is 1400 ppm. There appears a positive correlation between Calcite and Sr contents of Kaladgi limestone, from which the Sr concentration of pure calcite is deduced to 1438 ppm. which is in good agreement with (1-2) X 10 ppm, as reported in literature (Turekian and Kulp, 1956; Milliman, 1974.). According to Kinsman (1969), the calcite precipitated in equilibrium with seawater contains approximately 1375 ppm. of Sr. During the conversion of aragonite to calcite through dissolution-precipitation processes, Sr is lost. Harris and Matthews (1968) have estimated >90% Sr loss during this process for Pleistocene reef limestones. Therefore, the overall concentration depends on the fractions of aragonite and high-magnesium calcite replacements and the rate of dissolution and reprecipitation processes versus the rate of movement of the pore fluid through the rocks. Kinsman (1969) has interpreted the values of Sr in Calcite as a result of the passage of a large volume of fluid through the sediments. During his study, he found the average Sr concentration in calcite to be 418 ppm, thereby indicating the process of diagenesis in an open system and less saline environment.

Extrapolating this reasoning for the Kaladgi carbonate samples which are completely devoid of aragonite and very low amount of Sr contents, it is possible that initially there was some finite amount of aragonite or High Mg-Calcite which later got converted into calcite and subsequently to Dolomite accordingly decreasing the strontium contents, which is in accordance with the Kinsman's (1969) studies. The absence of a significant correlation of Sr with Na is an interesting point to note that it indicates the less saline nature of depositional waters. The possible freshwater influx into the depositional site is probably in the early diagenetic stages.

Lead, Zinc, and Nickel

The uniform presence of Pb, Zn, and Ni in the present samples is interesting. Pb shows a positive correlation with Fe indicates an external source. Generally, limestones and

dolomites are low in lead content. Generally, pelagic clays show higher concentrations of Zn than the nearshore. The relatively lower concentrations of Zn (10.27 to 20.91) in these rocks are related to the shallow water phase. Nickel is very stable in aqueous solutions and capable of migration over a long distance. The weathering of source rocks gives rise to Fe, Ni, and Si. As the aqueous solution sinks, Fe oxidizes and precipitates as ferric hydroxides and then loses water ultimately to form goethite and hematite in which small amounts of Ni ions are trapped. Generally, deep see sediments show a higher concentration of Ni up to 1000 ppm, whereas shallow-water sediments show low concentrations (Davies, 1974). The lower values of Ni (17.97 to 26.70 ppm) in the present samples can be related to the shallow water environment of deposition.

5.5.3: Other elements

The other trace elements analyzed include V, Cr, Co, Cu, Ga, Rb, Y, Zr, Nb, Cs, Ba, Hf, Ta, Bi, Th, U, and REE been used in the interpretation of origin and provenance. The distribution of these elements and their interrelationships are shown in Table 5.4 and Figure 5.8. In general, the elements with low water rock coefficients and low residence time values, including Zr, Hf, Ga, Y, Th, Nb, Be, and REE are strongly excluded from natural waters and remain in the oceans for less time than average ocean mixing times. Consequently, these elements are likely transferred quantitatively into sedimentary rocks and give the best information regarding source rock composition. Therefore, their distribution in the sedimentary rocks is most useful for provenance studies. The concentrations of these elements in the present samples closely resemble the upper crustal composition.

5.5.4: Rare Earth Elements (REE)

The rare earth elements (REE) are a group of 14 elements from La to Lu that generally exhibits similar chemical behavior. Owing to their electronic configurations, these elements form ions that are nearly all trivalent, with smoothly decreasing ionic radii. Notable exceptions are stabilization of Ce4+ and Eu2+ under appropriate oxidizing and reducing conditions, respectively. Goldschmidt (1954) was first to suggest that the constant distribution of REE in sedimentary rocks is the result of homogenizing effects of sedimentary processes. Therefore, the REE pattern of sedimentary rocks reflects the continental crustal abundances. The generally higher prevalence in the nature of even atomic numbers is manifest by ratios of up to an order of magnitude between neighboring pairs of elements. Consequently, comparisons among the REE are facilitated by normalizing

analytical values to an appropriate reference, such as Chondrite. However, the preferred reference for sedimentary rocks is the North American Shale Composite (NASC), a representative of the average upper crust (Gromet et al., 1984; Condie, 1993). Concerning such a reference, specific fractionation effects may enhance the light REE (LREE) or the heavy REE (HREE), and those may be quantified by the ratio of normalized Lan/Lun>1 (La/Lu>9.63) or Lan/Lun<1 respectively. Curvature in an REE plot may document an enhancement of the middle REE (MREE) concerning both LREE and HREE. The resulting "hat-shaped" REE plat may be quantified by a ratio such as 2GDn/ (Lan/Lun)>1.

5.5.5.1: REE distribution in Proterozoic Carbonate succession

In the present study, the REE has been analyzed to understand their distribution in the Proterozoic Carbonate samples of Kaladgi and interpret the sedimentary processes. The average values of the total concentration of REE (∑REE) in the present samples vary from 11.13 to 60.86 (Table. 5.4) and are much below to the crustal average of 151.10 (after Mason and Moore, 1982). The Chondrite normalized REE patterns (Figure 5.8) of these rock samples are very similar to each other, (i) being enriched in the LREE relative to the HREE - show a higher degree of rare earth element fractionation when compared to source rock, as indicated in their (La/Yb)N ratio of 14.83, (ii) fractionated LREE and flat HREE and (iii) a negative europium anomaly. The difference in the relative degrees of fractionation among

LREE and HREE is reflected in their high LaN/SmN ratios (2.13 to 4.73; mean - 4.12 but relatively lower GdN/YbN mean ratios. This kind of fractionation is characteristic of post- Archaen sediments (McLennan and Taylor, 1991).

Table 5.4: Stratigraphic Distribution of summary Average values of REE

Member ∑REE LREE HREE La/Sm Gd/Yb Bamanbudni dolomite 60.86 53.74 7.12 4.16 1.51 Petlur Lst 18.03 16.02 2.01 4.83 1.57 Nagunur Dolomite 28.5 24.58 3.92 4.63 1.86 Chiksellikeri Limestone 29.09 26.25 2.84 4.93 2.28 Chitrabhanukot Limestone 14.84 13.07 1.77 3.94 1.85

Shale normalized REE abundance of the samples gives a relatively flat pattern with approximately 0.2 times NASC. The concentration of REE in the present samples compared

to NASC (REE of NASC is 173.2) is due to the relatively silty nature of samples with much clay minerals and rock fragments that contain high REE among the eroded materials. Although their REE is concentration high, the variability in terms of bulk rare earth elements and LREE/HREE ratio for all the samples is low. This kind of similarity among sediment samples could be attributed to the homogenization due to erosion and transportation (Goldschmidt, 1954). The LREE enrichment, as compared to HREE, is attributed to the weathering and recycling of the provenance rocks (Duddy, 1980).

The restricted elemental concentration SREE varying from 11.13 to 60.86 for the entire sequence, as seen in samples from different locations of Kaladgi Basin, which had undergone varying degrees of sediment transport processes, reflect relatively stable tectonic conditions corresponding to the formation of carbonate.

5.5.5.2 REE anomalies

The most distinctive deviations from the REE's normal behavior are "anomalous" levels of Ce and Eu. Understanding the origin of the depletion in Eu and Ce, relative to the other normalized REE in clastic/carbonate sedimentary rocks, is fundamental to most crustal composition and evolution interpretations. A deviation of Ce and Eu may be quantified as a ratio to Ce* and Eu* respectively by interpolating neighboring REE {Cean = Cen/[(Lan)(Ndn)]1/2 and Euan = Eun/[(Smn)(Gdn)]1/2}.

5.5.5.3 Eu anomaly

Almost all the post-Archean sedimentary rocks (except volcanogenic sediments) are characterized by Eu depletion (Taylor & McLennan, 1985). The negative Eu anomaly in some of these rocks indicates preferential removal of feldspar due to weathering (Nesbitt et al. 1996). The samples have a relatively lower mean value than the NASC representing the typical post-Archean sub mature sediments derived from differentiated upper continental crustal provenance (Eriksson et al. 1992). Though the rare earth elements are known to be immobile in weathering, Eu has slightly higher mobility than other REE (Albarede & Semhi, 1995).

5.5.5.4. Ce anomaly

The possibility that Ce anomaly could be used as a possible indicator of redox conditions in natural water masses and their associated sediments, and that such sediments were preserved as a reliable indicator of palaeo redox in ancient oceans, attracted a good deal of attention in recent years (Wright et al., 1987,88). The prominent feature observed in REE distribution in present-day waters, and palaeo seas is a negative Ce anomaly. If an oxic-suboxic boundary is encountered in a basin, the Ce anomaly reduces sharply to zero as Ce is re-mobilized (Sholkovitz et al. 1992). In general, strongly negative to zero Ce anomalies, and more rarely a weakly positive Ce anomaly are prominent features of REE distribution in a wide variety of modern and ancient sedimentary environments.

5.6 Diagenesis

Diagenesis can be defined as the changes which occur in the character and composition of sediments, beginning from the moment of deposition and lasting until the resulting materials (rocks) are either moved into the realm of metamorphism or become exposed to the effects of atmospheric weathering. The diagenesis of carbonate sediments includes all the processes which affect the sediments after deposition until the realms of incipient metamorphism at elevated temperatures and pressures. Diagenesis includes distinct processes such as cementation to produce limestone and dissolution to karst development. However, it also includes more subtle processes such as the development of micro-porosity and change in trace element and isotopic signatures. Certain factors will initiate diagenesis, whereas the same factors will perpetuate the old and/or cause the commencement of new diagenetic processes. The sediments have a tendency to adjust to new physical and chemical conditions and would, theoretically, reach equilibrium. The micro- and macro-environmental conditions above and within the sediments, however, change continuously.

The majority of ancient limestone is composed entirely of low-Mg calcite or dolomite (if dolomitized). The studies of carbonates thus involve trying to identify the original mineralogy of the various cement, their significance in pore fluid chemistry and diagenetic environment, and the relative timing of precipitation and any alteration. Diagenesis includes six major processes, namely cementation, microbial micritization, neomorphism, dissolution, compaction (including pressure dissolution), and dolomitization. The patterns of diagenesis vary significantly from one formation to another, and there are frequent

variations both laterally and vertically within one limestone sequence. Various factors determine the nature of the end product of diagenesis:

1) The composition and mineralogy of the original sediments.

2) Interstitial fluid chemistry and their movements.

3) The physical and chemical processes involved and the time subjected to them involve burial/uplift, the influx of fluids, and the prevailing climate.

5.6.1: Diagenesis of Carbonate Units of Lokapur Subgroup:

Different diagenetic processes have been observed to occur within the different units of carbonate rocks of the Lokapur Subgroup. These can be ascribed to late diagenetic modifications that take place under physicochemical conditions that differ from those of the original depositional conditions, both during burial to increasing depths beneath younger deposits and uplift and exposure to circulating groundwater or vadose solutions. The significant diagenetic changes observed include the compaction, dissolution, recrystallization, and replacement (dolomitization, Silicification / Chertification), etc., which corresponds to burial diagenesis.

Burial environments are conventionally subdivided into shallow burial and deep burial, but the boundary is clearly defined.

The shallow burial zone includes the first few meters to tens of meters of burial. Shallow burial near-surface diagenesis is influenced by changing pore water chemistry in the mixing zone, temperature, and pressure processes.

Various conditions control diagenetic processes in the deep burial zone. Pore water composition in deep burial environments differs substantially from that of shallow diagenetic environments, where cementation usually occurs in dilute meteoric waters that are oxic or only slightly reducing.

Processes in deeper burial environments include:

• Physical compaction due to sediment overburden: Reduces thickness of sediments, porosity, and permeability, leads to breakage and distortion of grains (readily seen in grainstones) and produces compressed fabric.

• Chemical compaction: It starts at various depths of overburden (commonly several hundred and thousands of meters but at an overburden of 100 or 200 m) leads to a reduction in the thickness of sediments, porosity, and permeability, Produces stylolites and other pressure-solution structures. Pressure solution provides carbonate for burial cementation.

• Cementation: Produces coarse calcite spar cement. The cements are enriched in iron and manganese, poor in strontium. Fluid inclusions are typical. Coarse or poikilotopic calcite, drusy, and other calcite mosaics, saddle dolomite.

• Minor solution porosity: Caused by the dissolution of carbonate and calcium sulfate minerals.

• Burial dolomitization: Anhedral crystalline fabric; generally coarse crystals.

5.6.2: Compaction

Compaction and pressure solution (stylolitization) (PLATE 5.6) refer to mechanical and chemical processes, triggered by the increasing overburden of sediments during burial and increasing temperature and pressure conditions. One of the most important processes occurring in subsurface carbonates is compaction and diagenesis resulting from pressure solution. The pressure solution is the result of a chemical reaction in a non-hydrostatic stress field. Since the early work of Thomson (1862) and Sorby (1863), pressure solution phenomena have been extensively studied by carbonate petrologists. Numerous experiments have been conducted to determine mechanisms, and increasingly elaborate theories have evolved to model the process. It is an essential process in carbonate diagenesis and has major significance in the related fields of structural geology and geophysics.

Compaction here involved the formation of many solution seams (brownish, irregular streaks) in areas not strongly cemented during early diagenesis. Solution seams are more planar than stylolites, involve less dissolution along any single surface, but occur in such numbers that, in aggregate, they can accomplish extensive alteration; the swarms of surfaces are sometimes called "horsetail seams."

5.6.3. Replacement

Replacement (Figure 5.6c) diagenesis involves the wholesale substitution of the original and diagenetic calcium carbonate by another mineral. In some instances, although the original shell/skeletal geochemistry is lost, valuable macro- and microstructural information may be

retained in the replacement mineral mimicking the original features. This morphological replacement of biogenic carbonates by authigenic minerals requires that the transformation is controlled by a process that is invariably linked to the crystallites' growth. Furthermore, because of the highly stable nature of some of these authigenic minerals, biogenic information may be preserved that otherwise would have been obliterated by the ravenous actions of diagenetic fluids.

Two major processes dominated the replacement of original carbonate phases in the present samples, including dolomitization and silicification.

5.6.3.1. Dolomitization

Most of the dolomites in the modern depositional environment and a vast volume of those in ancient rocks were formed by chemical alteration and recrystallization of calcite (i.e., of limestone). This process is called dolomitization. It is carried out by Mg-rich fluid moving through pores in sediments and sedimentary rocks (Mclane, 1995). Dolomites can be formed by precipitation of CaMg (CO3)2 from solution (primary dolomite), by dolomite cementation in pore spaces of sediment, and by replacement (dolomitization) of precursor carbonate sediment (CaCO3) with CaMg (CO3)2. Primary precipitation and dolomite cementation account for only a minor amount of dolomite; replacement apparently generated most of the dolomite in the geologic record. Dolomites can form penecontemporaneously, while the host sediments are still in their original depositional setting, or post depositionally after the host carbonate sediments have been removed from the zone of active sedimentation. Most dolomite is post depositional.

The significant diagenetic changes observed are dissolution, replacement, and recrystallization. The dissolution has formed numerous caves forming karst topography. Recrystallization has increased in the grain size of the mineral grains. The replacement is mainly of calcite by dolomite that is dolomitization (Figure 5.6 d). Further, the rock has also undergone silicification (Figure 5.6e).

5.6.3.2. Silicification

Silicification or certification (Figure 5.6 e) is another diagenetic replacement process typical in carbonate allochems of all ages (Maliva and Siever, 1988; Hesse, 1990) and sometimes in conjunction with pyritization (e.g., Loope and Watkins, 1989). Replacement by silica is

highly allochem selective while generally leaving the host rock material unaffected. This process probably proceeds before or after carbonate-controlled diagenetic processes and is highly dependent on the replacement of the microenvironment's chemical-crystal growth conditions.

Figure 5.1 Textural classification of carbonate sediments on the basis of relative abundance of lime mud matrix and sparry calcite cement and on the abundance and sorting of carbonate grains (allochems). After Folk, R. L., 1961,

1.000

0.961

0.969

0.360

0.840

0.861

0.874

0.850

0.978

0.019

0.829

0.899

0.771

0.009

0.154

0.794

0.664

0.453

0.888

0.713

0.953

0.356

0.294

0.666

0.000

0.081

0.189

0.288

0.321

-0.138

-0.272

-0.216

-0.098

-0.163

-0.051

HREE

0.961

1.000

0.999

0.451

0.902

0.906

0.913

0.902

0.924

0.890

0.942

0.814

0.106

0.193

0.889

0.496

0.502

0.920

0.719

0.949

0.321

0.391

0.793

0.012

0.137

0.258

0.370

0.426

-0.108

-0.225

-0.211

-0.019

-0.017

-0.177

-0.114

LREE

0.969

0.999

1.000

0.442

0.898

0.904

0.912

0.899

0.934

0.886

0.941

0.812

0.095

0.189

0.882

0.518

0.498

0.920

0.722

0.953

0.326

0.381

0.781

0.011

0.131

0.251

0.362

0.415

-0.112

-0.231

-0.212

-0.028

-0.013

-0.176

-0.107

SREE

0.360

0.451

0.442

1.000

0.541

0.281

0.259

0.542

0.174

0.156

0.512

0.550

0.296

0.110

0.619

0.519

0.606

0.184

0.457

0.301

0.540

0.337

0.501

0.174

0.538

0.574

0.056

0.394

0.456

0.497

0.493

-0.257

-0.065

-0.425

-0.019

0.840

0.902

0.898

0.541

1.000

0.994

0.992

0.993

0.749

0.993

0.987

0.800

0.085

0.879

0.416

0.498

0.939

0.505

0.906

0.258

0.542

0.906

0.099

0.194

0.254

0.396

0.520

0.574

-0.062

-0.092

-0.067

-0.126

-0.253

-0.046

-0.489

0.281

1.000

0.879

0.873

0.128

0.363

0.234

0.053

0.168

0.004

0.108

0.078

-0.138

-0.108

-0.112

-0.062

-0.098

-0.234

-0.061

-0.113

-0.231

-0.200

-0.035

-0.049

-0.111

-0.056

-0.282

-0.052

-0.191

-0.120

-0.058

-0.011

-0.117

-0.116

-0.109

0.259

0.879

1.000

0.947

0.141

0.121

0.007

0.023

0.302

0.063

-0.272

-0.225

-0.231

-0.092

-0.120

-0.088

-0.102

-0.131

-0.409

-0.184

-0.077

-0.099

-0.065

-0.064

-0.077

-0.505

-0.139

-0.246

-0.086

-0.098

-0.232

-0.091

-0.101

-0.111

-0.033

0.861

0.906

0.904

0.542

0.994

1.000

0.993

0.999

0.775

0.987

0.986

0.795

0.034

0.854

0.454

0.452

0.943

0.533

0.915

0.325

0.577

0.894

0.104

0.217

0.308

0.443

0.558

0.587

-0.098

-0.120

-0.092

-0.133

-0.218

-0.055

-0.513

0.174

0.873

0.947

1.000

0.053

0.117

0.101

0.183

0.140

0.006

-0.216

-0.211

-0.212

-0.067

-0.092

-0.116

-0.071

-0.109

-0.359

-0.133

-0.056

-0.069

-0.082

-0.103

-0.049

-0.060

-0.429

-0.100

-0.121

-0.101

-0.064

-0.148

-0.099

-0.096

0.156

1.000

0.772

0.088

0.067

0.381

-0.098

-0.019

-0.028

-0.126

-0.234

-0.088

-0.133

-0.116

-0.146

-0.135

-0.088

-0.086

-0.139

-0.244

-0.109

-0.052

-0.176

-0.257

-0.059

-0.074

-0.126

-0.131

-0.090

-0.310

-0.366

-0.104

-0.124

-0.115

-0.140

0.874

0.913

0.912

0.512

0.992

0.993

1.000

0.989

0.786

0.984

0.992

0.823

0.101

0.880

0.514

0.508

0.953

0.515

0.921

0.268

0.503

0.867

0.121

0.176

0.230

0.367

0.488

0.547

-0.061

-0.102

-0.071

-0.146

-0.230

-0.058

-0.487

0.850

0.902

0.899

0.550

0.993

0.999

0.989

1.000

0.766

0.985

0.983

0.796

0.031

0.851

0.430

0.450

0.942

0.532

0.910

0.340

0.601

0.897

0.104

0.215

0.332

0.466

0.578

0.599

-0.113

-0.131

-0.109

-0.135

-0.226

-0.037

-0.524

0.978

0.924

0.934

0.296

0.749

0.775

0.786

0.766

1.000

0.056

0.742

0.816

0.718

0.038

0.148

0.700

0.628

0.414

0.805

0.747

0.907

0.358

0.226

0.578

0.039

0.136

0.223

0.239

-0.231

-0.409

-0.359

-0.088

-0.041

-0.120

-0.062

0.019

0.110

0.772

0.056

1.000

0.404

0.214

0.476

0.030

-0.017

-0.013

-0.253

-0.200

-0.184

-0.218

-0.133

-0.230

-0.226

-0.214

-0.197

-0.141

-0.084

-0.037

-0.251

-0.049

-0.215

-0.094

-0.095

-0.087

-0.128

-0.456

-0.337

-0.033

-0.068

-0.116

0.829

0.890

0.886

0.619

0.993

0.987

0.984

0.985

0.742

1.000

0.977

0.815

0.112

0.859

0.389

0.515

0.934

0.508

0.904

0.241

0.545

0.907

0.095

0.166

0.258

0.400

0.522

0.579

-0.035

-0.077

-0.056

-0.086

-0.214

-0.111

-0.488

0.899

0.942

0.941

0.519

0.987

0.986

0.992

0.983

0.816

0.977

1.000

0.842

0.028

0.136

0.909

0.502

0.517

0.973

0.563

0.953

0.306

0.487

0.854

0.087

0.104

0.208

0.345

0.464

0.514

-0.049

-0.099

-0.069

-0.139

-0.197

-0.431

0.771

0.814

0.812

0.606

0.800

0.128

0.795

0.823

0.796

0.718

0.815

0.842

1.000

0.524

0.853

0.424

0.711

0.869

0.585

0.824

0.297

0.453

0.637

0.260

0.359

0.445

0.550

-0.065

-0.082

-0.244

-0.141

-0.006

-0.371

-0.003

-0.042

0.009

0.106

0.095

0.038

0.028

1.000

0.183

0.065

0.159

0.075

0.310

0.257

-0.257

-0.046

-0.111

-0.064

-0.055

-0.103

-0.109

-0.058

-0.037

-0.084

-0.111

-0.006

-0.086

-0.128

-0.175

-0.057

-0.069

-0.137

-0.320

-0.094

-0.093

-0.101

-0.183

0.154

0.193

0.189

0.184

0.085

0.363

0.141

0.034

0.053

0.101

0.031

0.148

0.112

0.136

0.524

1.000

0.371

0.099

0.859

0.232

0.042

0.183

0.093

0.006

-0.052

-0.037

-0.086

-0.267

-0.153

-0.065

-0.043

-0.437

-0.213

-0.199

-0.171

0.794

0.889

0.882

0.457

0.879

0.234

0.121

0.854

0.117

0.880

0.851

0.700

0.859

0.909

0.853

0.183

0.371

1.000

0.420

0.627

0.887

0.487

0.854

0.211

0.390

0.773

0.067

0.122

0.247

0.366

0.501

-0.176

-0.251

-0.279

-0.042

0.664

0.496

0.518

0.416

0.053

0.007

0.454

0.101

0.514

0.430

0.628

0.389

0.502

0.424

0.099

0.420

1.000

0.297

0.538

0.172

0.579

0.161

0.105

0.292

-0.065

-0.257

-0.049

-0.128

-0.121

-0.198

-0.037

-0.176

-0.133

-0.092

-0.057

0.453

0.502

0.498

0.301

0.498

0.168

0.023

0.452

0.508

0.450

0.414

0.515

0.517

0.711

0.859

0.627

0.297

1.000

0.583

0.092

0.516

0.083

0.306

0.122

0.050

0.194

-0.049

-0.059

-0.215

-0.175

-0.190

-0.199

-0.306

-0.103

-0.027

0.888

0.920

0.540

0.939

0.943

0.953

0.942

0.805

0.934

0.973

0.869

0.065

0.232

0.887

0.538

0.583

1.000

0.547

0.960

0.353

0.467

0.762

0.135

0.205

0.329

0.433

0.449

-0.056

-0.077

-0.060

-0.074

-0.094

-0.438

-0.064

0.713

0.719

0.722

0.337

0.505

0.533

0.088

0.515

0.532

0.747

0.404

0.508

0.563

0.585

0.159

0.042

0.487

0.172

0.092

0.547

1.000

0.609

0.537

0.365

0.541

0.180

0.040

0.283

0.335

0.390

0.421

-0.282

-0.505

-0.429

-0.532

0.953

0.949

0.953

0.501

0.906

0.915

0.921

0.910

0.907

0.904

0.953

0.824

0.075

0.183

0.854

0.579

0.516

0.960

0.609

1.000

0.371

0.719

0.066

0.113

0.238

0.342

0.348

-0.052

-0.139

-0.100

-0.126

-0.095

-0.295

-0.078

0.356

0.321

0.326

0.174

0.258

0.325

0.268

0.340

0.358

0.214

0.241

0.306

0.297

0.310

0.211

0.161

0.353

0.537

0.371

1.000

0.655

0.286

0.198

0.701

0.702

0.677

0.516

-0.191

-0.246

-0.121

-0.131

-0.267

-0.190

-0.119

-0.362

P2O5

0.294

0.391

0.381

0.538

0.542

0.577

0.503

0.601

0.226

0.545

0.487

0.453

0.390

0.083

0.467

0.365

0.371

0.655

1.000

0.670

0.513

0.938

0.978

0.991

0.894

K2O

-0.120

-0.086

-0.101

-0.090

-0.087

-0.057

-0.153

-0.121

-0.585

-0.150

0.666

0.793

0.781

0.574

0.906

0.894

0.067

0.867

0.897

0.578

0.907

0.854

0.637

0.773

0.105

0.306

0.762

0.541

0.719

0.286

0.670

1.000

0.386

0.409

0.539

0.661

0.739

-0.058

-0.098

-0.064

-0.128

-0.069

-0.065

-0.354

-0.187

Na2O

0.381

0.476

0.257

0.093

0.180

1.000

CaO

-0.163

-0.177

-0.176

-0.425

-0.489

-0.011

-0.232

-0.513

-0.148

-0.487

-0.524

-0.041

-0.488

-0.431

-0.371

-0.279

-0.198

-0.199

-0.438

-0.295

-0.119

-0.585

-0.354

-0.684

-0.334

-0.500

-0.543

-0.549

-0.445

0.056

0.099

0.004

0.302

0.104

0.183

0.121

0.104

0.095

0.087

0.292

0.122

0.135

0.066

1.000

MgO

-0.051

-0.114

-0.107

-0.310

-0.120

-0.456

-0.003

-0.137

-0.043

-0.042

-0.532

-0.362

-0.150

-0.187

-0.684

-0.175

-0.210

-0.198

-0.214

-0.340

0.000

0.012

0.011

0.194

0.108

0.063

0.217

0.140

0.176

0.215

0.166

0.104

0.067

0.040

0.198

0.513

0.386

1.000

0.555

0.567

0.580

0.652

MnO

-0.019

-0.366

-0.062

-0.337

-0.042

-0.320

-0.437

-0.037

-0.306

-0.064

-0.078

-0.334

-0.175

0.081

0.137

0.131

0.394

0.254

0.308

0.230

0.332

0.039

0.030

0.258

0.208

0.260

0.122

0.205

0.283

0.113

0.701

0.938

0.409

0.555

1.000

0.987

0.951

0.828

-0.117

-0.091

-0.099

-0.104

-0.094

-0.213

-0.176

-0.103

-0.500

-0.210

Fe2O3

0.189

0.258

0.251

0.456

0.396

0.443

0.367

0.466

0.136

0.400

0.345

0.359

0.247

0.329

0.335

0.238

0.702

0.978

0.539

0.567

0.987

1.000

0.987

0.883

TiO2

-0.116

-0.101

-0.099

-0.124

-0.033

-0.093

-0.199

-0.133

-0.027

-0.543

-0.198

0.288

0.370

0.362

0.497

0.520

0.558

0.488

0.578

0.223

0.522

0.464

0.445

0.366

0.050

0.433

0.390

0.342

0.677

0.991

0.661

0.580

0.951

0.987

1.000

0.929

Table 5.3: Corelation coefficient matrix coefficient Corelation 5.3: Table

-0.109

-0.111

-0.096

-0.115

-0.068

-0.101

-0.171

-0.092

-0.549

-0.214

Al2O3

0.321

0.426

0.415

0.493

0.574

0.078

0.587

0.006

0.547

0.599

0.239

0.579

0.514

0.550

0.006

0.501

0.194

0.449

0.421

0.348

0.516

0.894

0.739

0.652

0.828

0.883

0.929

1.000

SiO2

-0.033

-0.140

-0.116

-0.183

-0.057 -0.445 -0.340 83

HREE

LREE

SREE

P2O5

K2O

Na2O

CaO

MgO

MnO

Fe2O3

TiO2

Al2O3 SiO2 Table-5.1 Coorelation Coefficient Matrix Table-5.1Coefficient Coorelation

Field photographs - Stromatolites

Figure 5.1 a: Typical concentric to cylindrical shaped stromatolites exposed at ground level near Lokapur

Figure 5.1 b: Outcrops of Dolomitic limestone showing folded structure exposed in fields around Lokapur

Figure – 5.2 Field photographs -Stromatolite types

a. Algal Stromatolite bedding of dolomitic b. Pseudo Columnar* Stromatolites showing limestone exposed on the Lokapur to Petlur both upward convex and concave lamination Road (Lokapur)

c. Deformed stromatolite mat seen in d. Stromatolite possibly of Conophyton Dolomitic limestone Cylindricus

Figure 5.2 e. Four common microbial (stromatolitic) structures: domal, columnar and planar stromatolites, and oncolites. (Source: Tucker 1982)

*Columnar stromatolites are discrete structures, usually forming in higher-energy locations, so that intraclasts and grains commonly occur between the columns.

Figure – 5.3 Photomicrographs-Carbonates

a. Finely crystalline micritic limestone. b. Fine to medium grained micritic limestone (Petlur Limestone Member) XN displaying unidentified organic particle (Bamanbudni Dolomite Member) XN

c. Medium grained algal laminated limestone d. Typical xenotopic mosaic of anhedral to (Chiksellikeri Limestone Member). XN subhedral replacement dolomite XN

e. Subhedral Dolomitic limestone f. Micro crystalline Dolomite displaying (dolomicrite) displaying replaced organic generation of secondary porosity remain (Chitrabhanukot Dolomite Member) (Chitrabhanukot Dolomite Member) XN XN

Figure – 5.4 Photomicrographs – XRD

A. L15 B. L8 (Chitrabhanukot Dolomite).

C. L20 D. L-19

E. L12 F. L22

Figure – 5.5 Photomicrographs – XRD

1. L23 2. L24.

3. L26 4. L-27

6. L18 5. L30

Figure – 5.6 Photomicrographs – Diagenesis

a. Compaction effects shown be tight b. Noemorphism fine to sparry calcite and packing of finely crystalline dolomite replacement of dolomite (Chitrabhanukot leading to facture development Dolomite). (Chitrabhanukot Dolomite).

c. Replacement showing former fabric d. Dissloution and replacement textures (Petlur Limestone) (Chiksellikeri Limestone)

e. Xenotopic Dolomite replacement and f. Pressure solution effect leading to stylolite silification (Nagnur Dolomite) XN formation (Nagnur Dolomite) XN

Figure 5.7 Distribution of Trace elements

a. Line plot of Bamanbudni Dolomite b. Line plot of Petlur Limestone

c. Line plot of Nagnur Dolomite d. Line plot of Chikshellikeri Limestone

e. Line plot of Chitrabhanukot Dolomite

Figure 5.8

REE distribution

Figure 5.8: Chondride normalized REE distribution pattern of different units different carbonate REE of distribution Chondride 5.8: normalized pattern Figure

REE/Chondride normalised

CHAPTER 6:

PROVENANCE

AND DEPOSITIONAL

HISTORY

6.1.: Introduction

Provenance studies of sandstone are generally founded on the notion that different tectonic environments have distinct or unique characteristic rock types. Many works have been done on sandstone's composition and its implications on the tectonic setting of a depositional basin. Important amongst these are the works of Crook (1974), Young (1976), Dickinson and Suczek (1979), Mack (1984), Dickinson (1985,1988), Trop and Ridgway (1997). The critical relationship between provenance and basins is governed by plate tectonics, which ultimately controls the distribution of different types of sandstones, Dickinson and Suczek (1979).

Provenance studies in the present work is based on the (i) mineralogy and chemical composition of the detrital components in the rocks, from which source-rock lithology and tectonic setting has been understood and (ii) presence of sedimentary structures from which depositional environments has been interpreted. Various researchers have used Q-F-Lt ternary diagrams and attributed the detrital composition of sedimentary rocks to different provenance types, including stable cratons, basement uplifts, magmatic arcs, and recycled orogens. The petrographic study reveals that Saundatti Quartzite Member's studied rocks are characterized by a higher proportion of monocrystalline quartz followed by polycrystalline quartz, a considerable number of lithic fragments, and subordinate feldspar.

6.2.: Interpretations The mineralogy of the detrital particles in siliciclastic sedimentary rocks provides the primary evidence for the lithology of the parent rocks in the source area. Mineralogy also provides most useful evidence for interpreting tectonic setting because source-rock lithology is linked fundamentally to tectonic setting. Samples belonging to Saundatti Quartzite member show a high percentage of Quartz (90.43) and textural features such as medium to fine grains, good sorting and subangular to a rounded shape and lesser number of Lithic fragments (8.31) and very poor content of Feldspars (1.25). (Table- 4.1) indicating transportation from distant/remote sources or extensive reworking of the sediments and points towards a cratonic or a recycled orogen source.

Since quartz is the most abundant constituent in most of the sandstones, and essentially the only constituent of some sandstones, geologists have been intrigued by the potential

provenance significance of quartz since the early years of petrographic study (e.g. Sorby, 1863; Mackie, 1896). Undulatory extinction and the polycrystalline nature of some quartz grains from the study area (plate) is suggestive of igneous and metamorphic parent rocks. Highly Undulose quartz (Undulose extinction > ~ 5 degrees) is diagnostic of metamorphic rocks and non undulose quartz is diagnostic of igneous rocks.

A granitic source can be identified for these sediments, as most of these samples are dominant in Monocrystalline quartz grains (Basu et al. 1975). Dabbagh and Rogers (1983) also suggested that such grains may result from the disaggregation of original polycrystalline quartz during high energy or long-distance transport from the metamorphic source. Polycrystalline quarts, though second in abundance in studied samples points towards metamorphic source for these sediments.

Lithic fragments follow in abundance after Quartz in the studied samples. Presence of lithic fragments provide the most unequivocal evidence of source-rock lithology. Lithic fragments here are particles of gneissic grains. Though less in abundance, they point at a defenite metamorphic source for these rocks.

A low percentage of lithic fragments and feldspars, which are almost absent in some of the samples from the studied horizon, favors a cratonic source, mature transport regime, and long moderate chemical weathering in a warm, dry climate (Amireh, 1991). Feldspar fragments appear hazy and due to dissolution effects and alteration to clays. Overgrowths developed on Quartz grains, and rock fragments indicate several phases of recycling from Older sources.

Among clay minerals, Kaolinite is a common detrital clay mineral observed in the clastic sediments from study area. Presence of it in these sediments indicate that they are derived from granitic and gneissose sources. It is formed from feldspars both by hydrothermal alteration and by superficial weathering. Kaolinite can also be formed as a result of incongruent dissolution of K-feldspar. Formation of Kaolinite is also noted under strongly leaching conditions like abundant rainfall, good drainage, acid waters, in marine basin tends to be concentrated nearshore.

Chlorite is another clay mineral which forms constituent of these rocks. It is primarily derived from Metamorphic source rocks or may be formed particularly during burial diagenesis. It also occurs as cementing material in interstitial grain spaces.

Heavy minerals such as Zircon and tourmaline are particularly resistant to both chemical decomposition and mechanical abrasion and these minerals can survive multiple recycling. Thus, the presence of rounded zircon and tourmaline in a sandstone that contains few if any other heavy minerals is suggestive of sediment recycling or of an episode of intensive chemical leaching or mechanical abrasion. Association of Zircon with rounded grains of tourmaline as observed is suggestive of Reworked sedimentary source.

Presence of Ripple marks at some horizons indicate that deposition of sands occurred under gentle traction currents or in fluvial environments. These structures are produced by unidirectional traction currents as, for example, in a river channel. Signatures like occurrence of cross stratification complements the conclusion that these rocks were formed under fluvial environments of deposition.

Granulometric data derived from samples collected from the study area were plotted over standard classification diagrams to derive their provenance. Classification of sandstone provenance is according to the Dickinson (1985) scheme, and detrital modes were recalculated to 100% as the sum of Qt, Qm, F, L, and Lt. The Qt–F–L triangular plot emphasizes maturity, whereas the Qm–Fm–Lt plot emphasizes primary deposition from source rocks. Dickinson and Suczek (1979), Dickinson et al. (1983), and Dickinson (1985) schemes suggest the sediments of the Saundatti Quartzite member were derived from a craton interior and Quartzose recycled source (Figure 6.1). This is further supported by high quartz percentage and altered feldspar, indicating erosion and deposition during the uplift of the Dharwarian Basement with subordinate contribution from areas with moderate uplift and from recycled orogens shedding quartzose debris of continental affinity into the basin. It can also be suggested that the mechanical weathering has contributed much to the rounding of quartz and feldspar grains in the Proterozoic sediments of Saundatti quartzite Member.

6.3: Depositional Environments: Bivariate plots between different textural parameters throw light on information regarding the depositional environments of sedimentation and demarcate fields overlapping the closely related depositional environments (Van Andel and Poole, 1960; Davadarini et al., 1977; Armstrong Altrin Sam and Ramasamy, 1999). As understood from petrographical observations, most of the samples are dominant in Quartz however, the presence of Lithic Fragments and subordinate feldspar classifies these rocks into Sublith arenites.

The scatter diagrams plots the statistical parameters of the distribution of grain size.The scatter plots among different size parameters have geological significances and an in the present study an attempt has been made to bring out the mode and environment of deposition. Various scatter plots proposed by different workers have been used to recognize different environments of deposition for these ancient sedimentary rocks. The combined environmental boundaries of Friedman (1979), Moiola and Weiser (1968) perhaps a reliable tool to identify the different environments of sedimentation.

The representative samples of the sandstones belonging to Saundatti Quartzite Member were plotted on bivariant diagrams based on five different combinations of grain-size statistical parameters. Mean size plotted against standard deviation (sorting) is generally considered to be a useful discriminator between the recent river, dune, and beach sands by Friedman (1961), Moiola and Weiser (1968). The plot indicates that most sandstone samples come from a coastal environment. (Plate-6.3)

Skewness versus mean size has been used to differentiate between the river, wave and slack water processes (Stewart, 1958), between beach and dune sands (Friedman, 1961, 1967; Moiola and Weiser, 1968) and between inland and coastal dune sands (Moiola and Weiser, 1968). Accordingly, when the data was plotted over this bivariate plot, most samples cluster in the zone of river processes while few showed to be deposited under wave processes. (Figure- 6.3.b).

Mason and Folk (1958) and Moiola and Weiser (1968) have proposed a plot of kurtosis versus skewness to distinguish between beach, dune, and Aeolian flat sands and between inland dune and beach sands. In the present case, most samples were seen to be plotted within the beach environment, and few were plotted in inland dune fields discriminated by Mason and Folk (1958). (Figure-6.3c).

Friedman (1961) proposed that dune, beach, and river sands could be differentiated by movement parameters that he interpreted to reflect differences in sediment transport mode and energy. He concluded that the movement parameters are more sensitive to differences in grain-size distributions than those corresponding to graphical parameters. However, plots of graphical parameters, median versus standard deviation (σ1) (Figure-6.3.d) and standard deviation (σ1) versus skewness (SKI) (Figure- 6.2.e) are confined to the field of the beach and river sands. Beach sands are more prominent, according to Friedman and Moiola, and

Weiser (Figure 6.3.A). However, when the data are plotted in the diagram of Friedman and Sanders (1978), most of the samples cluster in the river sand zone (Figure 6.2.e).

The standard deviation against the mean size plot is considered to be an effective discriminator between river, dune, and beach sediments (Friedman, 1961; Moiola and Weiser, 1968) (Figure 6.3.b). Friedman (1961) classified the boundary based on the movement calculation, but it is probably less accurate when we used the graphic data in this plot. Moreover, Friedman's (1961) superimposed plot, Moiola, and Weiser (1968) shows the majority of samples belong to the river-dominated fields and little influence of wave processes on these sediments. The distribution of samples in the riverine environment field of the bivariant plot is due to the influence of littoral drift. The sediments are probably derived by the nearby rivers and are deposited in the study area.

The Saundatti Quartzite Member forms the lowermost unit of the Kaladgi Supergroup, and it preserves various primary sedimentary depositional features (Figure 2.3, 2.12). These Sandstone units can be compared to those ones deposited under a shallow environment of deposit. Various facies identified from field observation include massive bedded facies, hummocky cross-bedded facies, and ripple laminated facies. Along with these structures, grain size characteristics, and sediment dispersal pattern it can be understood that alteration of alternation of low-energy and high-energy conditions, which reflect the fair weather and storm periods, could be prevalent during deposition of these rocks.

The massive bedded facies are characterized by parallel lamination. At places with bimodality in grain size resembles a shoreface sediments and shows repeated alteration of physical processes that operated during its deposition (Howard, 1971; Howard and Reineck, 1972; Kumar and Sanders, 1976). The hummocky crossbedding is considered to be diagnostic of shallow marine sedimentation (Swift et al., 1983). The hummocks and troughs were interpreted as forms produced by the oscillatory motion of storm waves affecting the bottom (Harms et al., 1975; Hamblin and Walker, 1979). Another evidence of Shallower environment for these sediments is the presence of ripple marks (Figure 2.3). These are Symmetrical ripples with bifurcating crests which are indicative of an environment with weak currents where water motion is dominated by wave oscillations.

The mean size distribution pattern indicates fluctuations in the depositional environment with coarse grained to medium-grained sands deposited in alternating high energy and low energy environment. The Moderate to moderately well sorted grain is indicative of longer

sediment transport and earth processes which were responsible in segregating the sediments in size fractions. The skewness character of the sands is not conclusive as it varies in the entire spectrum from Coarse skewed samples to fine skewed samples. Most of the kurtosis values are platykurtic to very platykurtic, indicating that the grain size distribution was scattered and have thinner tails. Large populations of rounded and subrounded grains indicate long-distance transportation of sediments (Pettijohn, 1984). The overall texture of the sandstones can be considered mature. (table 4.3 and table 4.4)

Bivariant plots of various parameters indicate that mean size versus sorting has a negative relationship between size and sorting, indicating an increase in grain size with decreased sorting, reflecting fluctuating hydrodynamic conditions during deposition (Figure 2.11). Mean size versus skewness also shows an inverse relationship, and the samples are coarse skewed in a narrow range of mean size, indicating fluctuation in energy condition of depositional medium (Figure 6.2.b). Mean size versus roundness has a moderate inverse relationship indicating increase in roundness with decreasing grain-size (Figure 6.2.c). Roundness versus sorting has shown slightly inverse relationship giving indication of an increase in roundness with a decrease in sorting. (Figure 6.2.d)

The scatter plot of Moiola and Weiser (Figure 6.3e) reveals that the sediment samples fall within the field of the river and river processes. It may be possibly concluded that these sediments probably must have deposited in an environment where fluvial processes have dominance over marine processes. However, Friedman's scatter plot (Figure 6.3b) indicates a fluvial environment of deposition as the majority of the scatter plots were concentrated in the river field and few got plotted in the wave process field. Bivariant scatter plot proposed by Moiola and Weiser (Figure 6.3b) between the two size parameters, graphic mean size and inclusive graphic skewness show that majority of the samples fall within the river field. Contrary to above observations, Friedman's scatter plot (Figure 6.2e) suggests a shallow marine environment since the entire sample was plotted within the beach field.

From the scatter plot proposed by Friedman between the size parameters of inclusive graphic skewness and graphic kurtosis, beach influence is suggested with minor indications of inland dune deposits. The scatter plot of Moiola and Weiser (Figure 6.3d) also suggest a coastal dune environment of deposition as except one, almost all the samples fall in the dune field.

6.4.: Paleoclimate Climate has a definite influence over the variation in compositional maturity of the sandstone. Climate is considered to be the critical factor affecting the maturity (Suttner and Dutta, 1986) of sediments. Dott (1978) opined that climate is not a factor to be considered in understanding sandstone genesis. Darnell 1974, Young 1976, Potter 1978, Suttner et al., 1981, Franzinelli and Potter 1983 have studied Holocene sand composition in contrasting climates and provided some basis for interpreting the role of climate in compositional maturity of Sandstone. Results of the Holocene studies thus can be used to interpret the climatic history of ancient sediments.

Paleoclimate studies facilitate the understanding of weathering processes in the source area and the climatic condition of deposition. Climatic signatures are preserved in sands during deposition, provided they do not suffer sedimentary differentiation followed by long- distance transport and deposition in rough water littoral environments. Sandstone compositions are affected by tectonics, transportation history, and sedimentary processes within the depositional basin and paleoclimate (Suttner and Dutta, 1986).

The effect of climate on sand composition gets imprinted through its influence on pedogenic processes, which converts a small population of large rock fragments into detritus made up of several populations of smaller rock fragments monomineralic grains, including polycrystalline quartz. Young et al. (1975), have demonstrated that if the same parent rock is weathered in contrasting wet and dry climates, under comparable conditions of relief, the detritus produced will have a framework composition unique to the climate in which it is produced. They have shown that ratios of feldspar plus lithic fragments to polycrystalline quartz or total quartz are sensitive indicators of Sand's Climatic background.

Results on the study, support that the optimum conditions for the production and preservation of a distinctive climatic signature on sand composition are met in extensional plate tectonic setting. This setting can be best understood from triangular plot of quartz, feldspar and rock fragments data as suggested by Dickinson and Suczek (1979).

Burial diagenesis converts sand to sandstone and can destroy framework grains in various proportions. Only with exceptionally deep burial diagenesis is the climatic control on framework composition of nonmarine sediments altered beyond recognition because of pervasive dissolution of silicate minerals and rock fragments (Suttner and Dutta, 1986).

Plotting of framework compositional data on QFR diagram helps in visualization of Provenance climate.

The average Q:F:R content of the Saundatti Quartzite Member is found to be 90: 1: 8. The average value of the Qm+Qp/ F + R and Qp/ F + R ratios for the Saundatti Quartzite is calculated to be 3.2 and 1, respectively. Simultaneously, the average value of the Qm +Qp / F + R and Qp / F*R ratios for the same samples is found to be 9.09 and 0.77, respectively.

Plotting of framework compositional data in the log/log bivariant plot of polycrystalline quartz / Feldspar plus rock fragments to plus rock fragments show that the points plots in the environmental field alloted under humid and semi-humid climate (Figure 6.4) for the samples under study.

Plotting of framework compositional data of QFR diagram show that points representing clusters around Humid environmental field (Figure 6.4)

From the bivariate log/log plots of framework composition of the sandstones belonging to Saundatti Quartzite Member, the paleoclimate has been inferred to be as humid. The QFR triangular plots also indicate a humid climate during the time of deposition of these sandstones. Sandstones under study understood to be are mature to sub-mature. This is evident from the moderate values of the ratios between total quartz to feldspar plus rock fragments and polycrystalline quartz to feldspar plus rock fragments. Relatively greater content of rock fragments few sandstone samples indicates perhaps a combination of shorter transport and steeper slope gradients of the depositional sites under the influence of sub- humid to humid tropical climatic conditions (Suttner and Dutta, 1986).

Therefore, from the above observation and interpretation it may be concluded that Sandstones belonging to Saundatti Quartzite Member are the product of a tropical or subtropical type of climate, which is a combination of high temperature and high humidity in areas of low relief. Sediments of the sandstones came from distant source areas and transported for a long time produces texturally mature Sandstones.

100

Figure – 6.1 Triangular Diagrams

a. Tectonic setting discrimination diagram based on Qt-F-L after Dickinson and Suczek 1979

b. Qm-F-Lt ternary diagram after Dickinson et. al. 1983

101

Figure – 6.2 Depositional Environment Bivariante plot for Saundatti Quartzite Member

a. mean size versus standard deviation b. mean size versus skewness

c. mean size versus mean roundness d. mean roundness versus sorting

e. Bivariant plot of skewness versus inclusive graphic standard deviation, after Friedman (1967).

102

Figure – 6.3 Depositional Environment Bivariant plot for Saundatti Quartzite Member

a. Bivariant plot of inclusive graphic b. Bivariant plot of skewness versus standard deviation versus mean mean size, after Stewart (1958), diameter, after Stewart Friedman (1961) and Moiola and (1958) and Moiola and Weiser (1968) Weiser (1968).

c. Bivariant plot of kurtosis vs. skewness, d. Bivariant plot of mean size versus after Mason and Folk (1958) and inclusive graphic standard Moiola and Weiser (1968). deviation, after Friedman (1961) and Moiola and Weiser (1968)

103

Figure – 6.4 Palaeoclimate

a. .The effect of source rock on the composition after Suttner et. al. 1981

b. Climatic discrimination diagram of Suttner and Dutta (1986).

104

CHAPTER 7: SUMMARY AND CONCLUSIONS

105

7.1: Summary: Proterozoic has been an exciting era in the Indian Stratigraphy that has led to the development of extensive sedimentary sequences of clastic and non-clastic rocks in various sedimentary basins referred to as ‘Purana Basins’ in Indian Geology. The sequence of Orthoquartzite, shale, dolomite/limestone, and some cases with volcanic rocks are widely distributed in several distinct basins on Peninsular India. The crustal evolution in Proterozoic was marked by stabilization of crust (during Late Archaean to Early Proterozoic) and formation of continental crust (by the accretion of Archaean cratonic nuclei). These continents were more extensive and more stable than the Archaean micro-continents and had broad and relatively flat shelves and basins. Around Early to Middle Proterozoic, deposition in intracratonic and marginal basins of continental-sized cratons had commenced.

The Kaladgi Basin, one of the important Purana basins of Peninsular India, exposes a thick sequence of Proterozoic succession composed of various lithologies with a predominance of arenaceous rocks. These are a sequence of unmetamorphosed and least deformed sedimentary rocks exposed in the parts of Belagavi, Vijayapura, Dharwad, and Gadag districts of Karnataka overlying the late Archaean schistose rocks and granitic gneisses. The basin is also bestowed with excellent outcrops of carbonate rocks consisting of limestone and dolomitic limestone. The thesis has broadly covered the Sedimentological aspects of the lower units of the Proterozoic Kaladgi Basin of the Northern region of Karnataka, India. It mainly focused on the field parameters, textural attributes, and mineralogical composition of these sediments to draw depositional history, tectonic set-up, and provenance of these ancient sediments.

Among the clastic units of Lokapur Subgroup, Saundatti Quartzite Member is dealt with in great detail. Wherever the basal conglomerate is insignificant, this quartzite horizon constitutes the lowermost unit of the Kaladgi Supergroup. It is the marker horizon and demarcates the basin boundary of the Bagalkot Group. Present work attempts to identify the detailed petrographic character of the sandstones to understand the provenance and depositional environments of these Proterozoic sediments based on careful petrographic observation and mineralogical studies. The primary depositional structures like Current bedding, graded bedding, ripple marks are preserved in these clastic rocks.

The study suggests that the coarse clastic conglomerates are essentially polymictic types. The sandstones are sub-mature to mature (mineralogically), medium to coarse-grained, and

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categorized mainly into lithic/feldspathic and quartz arenites. The presence of primary sedimentary structures indicates that these were formed under a shallower environment of deposition. Palaeocurrent data indicate an NW palaeoslope. To decipher provenance and climatic history, sandstone compositional data obtained were plotted on standard triangular and bivariate plots. Framework constituent is dominated by Quartz grains. Monocrystalline, as well as polycrystalline grains, are present. The monocrystalline variety was seen dominating the framework. The presence of a lithic fragments in the framework components of these sandstones suggests the cratonic source for these sediments. Few feldspathic grains were also seen in these rocks; however, their variable degree of alteration (from fresh to partially altered to completely altered grains) indicates a humid to the semi-humid environment. Following the standard classification scheme, these rocks were classified as Arenites or Sublith arenites. The rocks associated with textural maturity and nature of Quartz point towards the larger degree of transport and multiple cycle of sedimentation, which is complemented by rounded to subrounded clasts of framework constituents. Standard ternary diagrams were used to deduce tectonic history for these Proterozoic rocks. Upon that, most of the samples were plotted in the craton interior field. This is also supported by the composition of framework clasts, which suggest the derivation of sediments from a variety of granitic and gneissic crystalline complexes occurring along the basin margin. The maturity of the sandstones (Quartz Arenites) is attributed to the recycling and re-working of the older sediments. Analysis of Textural parameters of these rocks pointed towards deposition under beach environments, for Paleoclimatic studies indicated that these sediments were probably deposited under humid to sub-humid environments in craton interior regions.

Carbonate rocks (limestone and dolomite) provide reliable insights, both into the physical and chemical conditions that prevailed during deposition and into the geochemical settings that developed long after sedimentation. Extensive carbonate rocks occur and are well exposed in various parts of the Kaladgi Basin. For the present study, five litho units representing the limestone and dolomite were chosen from the Lokapur Subgroup of the clastic dominated Kaladgi Supergroup. All limestones are generally hard and compact and often bedded in character and display a significant color variation. These units are white, grey, and show variegated nature. The dolomites/dolomitic limestone are generally thin- bedded/nodular and buff, pale grey to dark grey, and often traversed by Quartz veins. Various types of stromatolitic structures are observed in these dolomitic rock units.

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The total concentration of REE (SREE) varies from 5.24 to 87.68 with a mean content of 28.63 for Kaladgi and is much less than to the crustal average of 151.10. The Chondrite normalized REE patterns of these rock samples are very similar to each other (except that of Simikeri Subgroup), being enriched in the LREE relative to the HREE - show a greater degree of rare earth element fractionation when compared to source rock, as indicated in their (La/Yb) N ratio of 14.83, fractionated LREE and flat HREE and more pronounced negative Eu anomaly. The difference in the relative degrees of fractionation among LREE and HREE is reflected in their high LaN/SmN ratios (mean - 4.15) but relatively lower GdN/YbN mean ratios (mean – 1.72). This kind of fractionation is characteristic of post- Archean sediments.

The discontinuous, thin shale partings in the Dolomites are indicative supratidal sedimentation, and associated stromatolites indicate CO2 rich environment with high pH. The presence of stromatolites, algal mats suggest tidal environment with relatively high hydrodynamic energy. The similarities in distribution patterns of REE suggest similar depositional conditions.

The present study of the petrographic and chemical characters of all the five carbonate units corresponds to dolomitic limestones instead of some carbonate stratigraphic units that can be called dolomites.

Provenance studies were conducted on Arenite samples of Saundatti Quartzite Member in which petrographic characters of these rock units along with granulometric data and field observations were taken into consideration to arrive at an internally consistent interpretation. Detrital composition of these rocks when plotted on standard QFL diagrams pointed that they were derived from stable continental craton interior. This is also complemented by low percentage of lithic fragments and feldspar grains making up the framework constituents. Their petrographical features imply a source area dominated by granites and granitoid gneisses, metamorphic rocks and humid to sub humid climatic conditions. Dominance of Subrounded grains indicate that the sediments have undergone considerable transport pre deposition. Loss of feldspar during erosion process and recycling of sediments could be attributed to enrichment of Quartz in the studied rock unit.

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7.2 Conclusions

Based on the present work, following conclusions can be drawn for the Proterozoic Sedimentary rocks of Saundatti quartzite Member of Lower Kaladgi sequence:

1. Presence of Primary sedimentary structures like asymmetrical ripple marks and cross-bedding in the Saundatti Quartzite member indicates that it was dominantly formed under the influence of continental processes. Which may be fluvial or shallow marine tidal environment. Thus, the overall environment of deposition for these sediments can be attributed to a fluvial, i.e., a continental setup.

2. The Sandstones of Saundatti quartzite member are medium to coarse-grained, moderately sorted to moderately well sorted. The Sand grains show roundness values ranging from 0.7 to 0.8, making them Subrounded to Subangular in nature. The framework constituents of the studied samples are mainly composed of various types of Quartz, followed by lithic fragments and fewer amount Feldspars. Heavy minerals are seen to be occurring as minor constituents. Based on this, the rocks are classified as Quartz arenites or Sublith arenites.

3. The petrography of these rocks clearly indicates that sediments for these sandstones were derived from a metamorphic and igneous source. This could be concluded from plotting on tectonic domain discrimination based on standard Qt-F-L & Qm-F-Lt plots. This also suggestive of sediment supply from the recycled orogen and basement granites exhumed in the craton interior.

4. The cementing material in these sandstones is silica and iron oxide. Silicious cementation is the result of the dissolution and precipitation of silica-rich fluids along with the pore spaces. Pressure solution was important in the development of secondary quartz in the Saundatti quartzite Member. Ferruginous cement results from the late diagenetic process of aging oxidation and dehydration of brown amorphous ferric oxide.

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5. Mechanical compaction was the dominant diagenetic process during the early stage of diagenesis. During mechanical compaction, rearrangement of grains took place, and long, Sutured, and concave-convex contacts developed. Well-developed concavo-convex grain contacts and sutured contacts suggest Silica may have precipitated from migrating pore water and oversaturated fluids resulting from local pressure solution.

6. In the light of the information obtained from the graphical, statistical parameters and bivariant plots, in combination with sedimentary structures and sediment dispersal patterns, it can be concluded that the rocks belonging to Saundatti quartzite Member have been deposited dominantly in fluvial processes and some were deposited in a range of nearshore environments where marine processes dominated over the fluvial processes.

7. The carbonate rocks which forms part of the present study include limestone, dolomitic limestone, cherty dolomitic limestones and comprises of calcite & dolomite as common carbonate minerals with scattered grains detrital Quartz, Felspar, Micas etc.

8. In all six petrographic types of Carbonates have been identified based the crystal shape, size and overall fabric viz. Micritic Dolomite, Biomicrites, Fine-coarse euhedral floating dolomite, Fine-coarse euhedral dolomite, Fine-coarse anhedral dolomite and Cement Dolomite.

9. The major Oxide, Trace and Rare Earth Element data of studied Carbonate horizons in general suggest a shallow or marginal marine setting for deposition of the carbonates supporting the presence of stromatolites.

10. Compaction, recrystallization, replacement (dolomite and silca) and pressure solutions are the main diagenetic process that has modified the carbonate rocks of Kaladgi to give rise to the present nature of the rocks.

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11. The climate plots concentrate mainly in the humid to sub-humid zone. However, the composition got further modified during transportation and subsequent sedimentation.

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Papers presented at national conferences

Following is the list of papers presented at various National conferences during the research tenure:

Verlekar P. and Mahender K. (2019); An analysis of Land Use Land cover using remote sensing and GIS, A study In and around Lokapur, Bagalkote District, Karnataka., Xth International Congress of Environmental Research, Kalady, Kerala

Verlekar P. and Mahender K. (2019); Sedimentology and Petrography of lower Kaladgi clastic sequence, Sedimentary researches: Last Five decades of advancement and Prospects in Future at the 35th Convention of Indian Association of Sedimentologists, Saugar, Madhya Pradesh.

Verlekar P. and Mahender K. (2017); Lateral lithofacies variation within Lokapur Subgroup, Kaladgi basin., National conference on Basin Dynamics, Facies architecture and Paleoclimate at the 34th Convention of the Indian Association of Sedimentologists, Amaravati, Maharashtra.

Verlekar P. and Mahender K. (2015); A brief review of Proterozoic Carbonate successions of Peninsular India with special reference to Kaladgi basin, National Seminar on “Recent Advances in Research on Precambrian Terrains of India” at XIV convention of Mineralogical Society of India, Mysore.

Nageshwar S., Verlekar P., Mahender K. (2014); Mineralogical and Petrographic studies of Proterozoic Carbonate rocks of Kaladgi Basin, National conference on Sedimentation and Stratigraphy, S. P. Pune University, Pune, India.

Research Paper Published

Verlekar P. and Mahender K. (2020): Provenance, tectonics and palaeoenvironment of Mesoproterozoic Saundatti Quartzite Member of Kaladgi Basin, India: A petrographic view, Journal of Indian Association of Sedimentologists. Vol 37(2), 91-102.

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