Chapter 1

Introduction Introduction 1.1 PROEM The key to effective basin analysis of any Proterozoic basin, lies in the assimilation of Proterozoic geohistory. Several sedimentary basins, which formed worldwide during the Proterozoic Eon, are the repositories of secular changes in the crustal, atmospheric, and oceanic processes as compared to the Archaean. The crustal evolution in Proterozoic was marked by stabilisation of crust, (during Late Archaean to Early Proterozoic) and formation of continental crust (by the accretion of Archaean cratonic nuclei). These continents were larger 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. Paleomagnetic and chronological data suggests that by Middle Proterozoic (around 1300 to 1000 Ma), all the continents coalesced to form a supercontinent called Rodinia surrounded by the Panthalassic ocean. All these evidences indicate that modern plate tectonic activity was operative even during the Proterozoic. Abundance of eukaryotes and other micro-organisms, in the ocean waters by ~ 2000 Ma, increased the free oxygen levels in the atmosphere and decreased the acidity of the oceans by the process of photosynthesis. As a result red beds and carbonates were deposited widely during Proterozoic. Around 1700 Ma stromatolites were also abundant, while Ediacaran fauna (multicellular soft bodied fauna) first appeared by ~ 900 Ma. In , all these Proterozoic events are preserved in seven independent sedimentary basins collectively known as "Purana Basins" of Peninsular India. Radhakrishna (1987) proposed to retain the name "Purana" (originally designated by Holland, 1907) to all those sediments in India, within the age range of Middle and Upper Proterozoic (1600-600 Million years). These basins host sediments deposited on the continental crustal segments composed of Archaean to Palaeoproterozoic rocks, after a profound hiatus, known as the "Great Eparchean Unconformity". These Purana basins, fringing the Archaean Cratonic Nuclei of the Indian Peninsular Shield (Fig. 1.1) are mostly epicratonic and pericratonic basins (Kale & Phansalkar, 1991). The sediments of these basins were deposited in shallow marine settings. Though contemporary in nature, these are individual and apparently independent basins with comparable growth histories. Except for the and Bhima Basins, all the other basins have close association with the Middle Proterozoic Mobile Belt (MPMB), which in a way may throw light on their evolutionary history (Kale, 1995 and 1998). Strong signatures of an intrinsic alliance between global flooding events and regional tectonism during the Proterozoic Eon is manifested in these basins. Although containing thick succession of sediments, they rarely display strong deformation. Recurrence of quartzite-argillite-carbonate suites, absence of widespread metamorphism, little associated igneous activity and structural simplicity are some of the salient features of these basins. It has been observed that wherever deformation is present in these basins, it is-«rtfltTrw«astnrtfiH to thp Introduction

IjCratonicnucleii; a) BM = Bundelkhand Massif; b) SC = Sighbhum Craton; c) BC = Bhandara Craton; d) WDC = Western Dharwar Craton. 2]Reworked Cratons; a) BBS=Bastar-Bhandara Sector; b) EDC=Eastern Dharwar Craton; c) ADB = Aravalli-Delhi Belt; d) CH = Chotanagpur Sector; e) EGB = Eastern Ghat Belt, f) SGT = Southern Granulite Terrain; 3]Proterozoic (Purana) Basins: a) VB = Vindhyanchal Basin; b) CB =Chattisgarh Basin; c) BB - Bastar Basins; d) PGB =Pranhita Godavari Basins e) CP =Cuddapah Basin; f) KB = Kaladgi Basin; g) BH = Bhima Basin. PC = Phanerozoic cover over the Precambrian terrains.

Fig. 1.1: Major Precambrian terrains of the Peninsular Indian Shield. (adapted from Kale, 1995 and 1998). Introduction flanks (Kale and Phansalkar, 1991). The only basin, which perhaps stands out as an exception is the Kaladgi Basin, situated on the northwestern fringes of Dharwar craton (see: Fig. 1.1) and which has been chosen for the geological investigations in this study. It is an E-W trending ovate basin, displaying strong structural deformation in its central sector with relatively undeformed flanks. The flanks have unconformable contacts with the adjoining crystalline basement of Archaean- Palaeoproterozoic age. This structural discordance, is highlighted in the multispectral satellite imageries (see: Title Photo), in which the tonal patterns manifesting lithological differences and the large folds and lineaments give an overall picture of the challenges hidden in the study of this basin. Today, although large parts of the basin are concealed under basaltic flows of Cretaceous-Tertiary Deccan Traps, the exposed parts give concrete clues of an amazing interplay between basement dynamics and sea-level fluctuations responsible for the development of this basin. It is this unique feature of this basin, in terms of its settings, thick sedimentary pile and structural configuration that has attracted the attention of several geologists working in the Precambrians of India. The past 150 years, have thus been dedicated to the research, focusing on the various aspects (sedimentological, structural and partly evolutionary history) of this basin. The first remarkable study of this basin, was that by Robert Bruce Foote way back in 1876. The work of Foote (1987), was the first compilation on the Kaladgi sediments carried out with such an accuracy and depth of perception for the time when it was conducted. After Foote, this complex basin was studied in details by Viswanathiah and his group (1964,1966,1968, 1970,1976,1979 and 1983) from the Mysore University, the Geological Survey of India (compiled in Jayaprakash et al., 1987) and by the researchers of Pune University (Peshwa, Kale and others from 1978 till 1999). All these studies have contributed in the assimilation of this complex basin. However, the application of modern techniques in basin analysis and sequence stratigraphy (which has made tremendous impact on studies of sedimentary basins in the last two decades) have not yet been attempted in this basin.

1.2 PURPOSE OF STUDY While carrying out the literature survey, it was realised that several questions regarding basin evolution, complexities in sedimentation and structural patterns have remained unanswered so far, due to lack of elaborate justifications in the previous studies. Tremendous amount of data has been generated over the years from these studies. However very few of these studies (Kale and Phansalkar, 1991, Kale etal., 1996) have attempted to decipher the basin dynamics in light of modern perspectives of basin analysis. The compilation of this data and its analysis using these modern techniques for deciphering the overall evolutionary history of this basin has thus provided the main objective for conducting the present study. Introduction

The work compiled in this thesis was thus undertaken in order to document: • Sedimentation patterns • Deformational patterns • Evaluation of the factors governing the evolution of this basin. In doing so, the data from the previous studies (duly acknowledged) was compiled along with the data generated during this study. On this background, the documentation of the contents of Kaladgi Basin and application of modern techniques has been attempted in this study, with the aim of unravelling the yet unknown aspects of this Proterozoic basin. However, it may be mentioned here, that this study is based purely on surface (outcrop) data. Hence the inferences drawn from this study may present a gross perspective of this basin. In absence of other data sources such as log data, seismic data, precise geochronological data and geophysical data (not available as yet for this basin), some of the inferences, which are of speculative nature may require further investigations in future studies.

1.3 CHOICE OF THE AREA To achieve these targets, it was realised that the area, which displays maximum amount of intricacies in terms of sedimentology and structure, would be an ideal candidate to conduct the desired investigations. It was hence decided to focus on the -Simikeri area, for the following reasons: 1. Previous workers have described "type" stratigraphic sections of this basin from this area. 2. This area displays significantly more deformation of the sediments than any other part of the basin and in doing so manifests the intricate relationships between hthologies and deformational structures. 3. Mappable contacts, conformable and unconformable, are well exposed in this area. The area of investigation has been designated as the "Bagalkot-Simikeri area" in conformity to the norms of Ph.D. registration by the University of Pune. In reality, the area covered in this study spans the entire eastern half of the contiguous exposures of this basin (Fig. 1.2).

1.4 AREA OF STUDY

1.4.1 GEOGRAPHICAL LocAnoN: The Kaladgi Basin spreads in the northern and northwestern parts of State. More than 70% of the basin is present in the Belgaum, , and Bagalkot, districts. Isolated outcrops of the Kaladgi rocks occurring as outliers, are present in the southern and southwestern regions of Maharashtra State (see: Fig. 1.2). The area under investigation, is bounded by: • Latitudes: 15°50' N and 16°25' N • Longitudes: 75°15' E and 75°45'E Introduction

• tii-H >, CO 00 0\ m r~l bo "^ -d a 03

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This 70 km x 57 km (~ 4000 km^) area is covered in six Survey of India Toposheets on a scale of 1; 50,000. Table 1.1, lists the important localities in each of the toposheet. Fig. 1.3, gives the map of the key localities in the study area. Table 1.1: List of toposheets and key-locations from the study area. Toposheet No Key Locations 47P/7 Galgalj, Mudhol, Halagali 47P/8 , Lakshanhatti, Jalikatti, Chitrabhanukot, Petlur 47P/11 Bilgi, Arakeri, Kadapatti, Bennur 47 P/12 Bagalkot, Simikeri, Muchkundi, Chikshellikeri, Kaladgi 47M/5 Ramdurg, Tergal Tanda, Mullur, Kolchi, Halgatti 47M/9 Badami, Kendur, Mahakut, Cholachagud Timmapur

1.4.2 ACCESS: Good lodging and boarding facilities are available at Bagalkot and Badami. Bagalkot is a well-developed town and an important commercial centre, as several cement quarries and factories are located in the vicinity of this town. The presence of archaeological sites, fabulous and huge Cave-temples and forts of the Chalukyan Dynasty built in the reddish brown sandstone, has converted Badami town, into a tourist destination. The other parts of Kaladgi Basin are not very far from these towns and are well connected by road. Mode of access to these locations is by public transport buses of Karnataka State Road Transport Corporation (KSRTC) and private minibuses called as "maxicabs" which access the remote villages. The distance from Pune to Bagalkot is approximately 432 km and it takes an overnight journey to reach Bagalkot from Pune. Lodging and boarding facilities in private and governmental setups are available at Ramdurg, Lokapur, Kaladgi, Mudhol, Bilgi and Tulasigeri. The Bijapur-Hubli Railway line passes along the eastern parts of the area and Bagalkot and Badami are two stations on this line.

1.4.3 CUMATE: Summers are extremely hot and dry, hottest months being April and May, with temperatures rising beyond 40° C. Pre-Monsoon showers occur around the end of May and early June providing temporary relief from the heat. In the months of July, August and September, the southwest Monsoon winds strike this region, with continuous showers causing flooding along the main rivers. The average annual rainfall in this region is around 50 cm. The relative humidity is maximum (~ 70%) in the months of July and August and minimum (<25%) in the peak summer months. October and mid-November experience increasing heat and humidity, with occasional thunderstorms. Winter season is between November and February. December is the coldest month, with temperatures falling to 13°-15°C. The months of March, April and May, are recommended for field traverses, as the lithological outcrops are best exposed due to lack of thick vegetation and dry streams; notwithstanding the dry and extremely hot climate. Introduction

INDEX h-—1 Roads 1*1 Towns h~— Railway line h^ Rivers • Villages

Fig. 1.3: Location and access map of the study area. Introduction

1.4.4 GEOMORPHIC FEATURES: Three conspicuous features (Fig. 1.4) are present in the study area: a) Long linear ridges. b) Low lying plains with gentle undulations c) Isolated mesas, and rolling flat-topped hills.

a) Ridges: The linear E-W trending hill ranges, rise to a height of upto 150 m above the gently undulating, low lying plains. Some of these hill ranges are long and broad as seen along the northern boundary of the basin. These expose moderate to steeply dipping quartzites and are clearly seen in the aerial photographs and satellite imageries. These ridges are the limbs of major folds.

b) Gently undulating low lying plains: Intensive weathering and erosion of the finer sediments like argillites and carbonates have contributed to the development of the vast, gently, undulating plains, which are also the flood plains of the Malprabha and Ghatprabha Rivers. In the northwestern, and central parts of this area, the basaltic lava flows of the Deccan TYaps cover the sediments and form a part of these vast plains. These lithologies contribute to the formation of black cotton soil, and hence agricultural activities are carried out extensively in these plains.

c) Isolated mesas, and rolling flat-topped hills: A flat topped plateau like terrain formed by the rolling hills of coarse gritty sandstone divide the Ghatprabha and Malprabha valleys. It is best exemplified by the Badami hill. Isolated "Mesas", of these sandstone are shown in Fig. 1.4.

1.4.5 DRAINAGE NETWORK: The River Krishna and its two main tributaries, Ghatprabha and Malprabha, represent main drainage lines in the area (Fig. 1.2 and 1.4). a) River Krishna: A large and major river flowing from west to east. It originates at Mahabaleshwar, in the Sahyadri hill ranges in the state of Maharashtra, flows through the states of Kamataka and Andhra Pradesh and ends its journey in the Bay of Bengal. The Ghatprabha and the Malprabha, two of its main tributaries, drain the Kaladgi Basin. Recently a huge dam has been constructed on River Krishna at Almatti, where the river cuts across the ridge forming the northeastern boundary of the Kaladgi basin. (Fig. 1.4).

b) River Ghatprabha: Originates in Western Ghats at a place called Ramgad in Kolhapur district of Maharashtra (Pappu and Deo, 1994). Rivers like Markendaya, Hiranyakeshi and Tamraparni also originating in the Western Ghats, are its main tributaries. This river and its local tributaries drain the northern and central sectors of the Kaladgi Basin. Introduction

75°15'E 75'45'E

16°25'N

75-45'E

Fig. 1.4: Geomorphology and drainage map of the study area. LR = Linear ridges; Cu = Cuesta; Bu = Buttes; Ms = Mesa; RH = Rolling hills; D = Domal structure; M = Seasonally water-logged marshy lands; PL = Lowlying undulating plains. Introduction

c) River Malprabha: This river, flowing through the southern parts of the Kaladgi Basin, enters the basin, cutting through its southern margin, at Navaltirth gorge near Saundatti, flows in an E-W direction for a short distances and exits the basin near Kolchi (east of Ramdurg). After running parallel to the southern quartzite ridge of the basin, it again enters the basin at Cholachagud, flowing in northeast direction, and finally joins River Krishna. The small but main tributaries of this river are Jaul Halla, Hire Halla, Benni Halla, Chella Halla, Godchi Halla and Sasve Halla to name a few. Most of these streams are restricted to the southern margin of the basin. Discovery of Palaeolithic tools, archaeological sites showing evidences of human settlements and presence of potholes in sandstones, in the southern parts of the basin, not very far from the present river's course, indicates that this river has changed its course in the recent past. However, this observation is not relevant to the present study, but coiild be a subject for future investigations. These rivers flowing through the area of investigation, have reached the mature stage, and flow with sinuous, well developed meandering and braided patterns. Lithology and structure of the bed rock, control the drainage patterns of these rivers and their tributaries. The prominent drainage pattern observed is dendritic, especially where the lithology is the basaltic flows of Deccan Traps that conceal the Kaladgi sediments. Many of the large streams inside the basin follow major shear zones. The high grounds on the otherwise flat plains exhibit annular drainage pattern, while trellis pattern is common on the highly fractured and jointed quartzite ridges.

1.4.6 LANDUSE PATTERNS: Most of the land in the basin, especially the plains, is under agriculture, except for the barren quartzite ridges abutting against the plains. On these rubble topped hill slopes, pulses like Bengal gram, Tur, Urad etc. are grown in post- monsoon seasons. In summer, fruit bearing plants like chikoo, pomegranates, oranges etc. are cultivated on the rugged slopes. The plains underlain by argillites, carbonate and basaltic rocks, yield crops, throughout the year, as they are adequately drained by the major rivers and their tributaries. In this peneplained land, with thick black cotton soil and ample water supply, crops like sunflower, maize, sugarcane and leguminous plants like groundnuts are cultivated on a very large scale. Watermelons are also grown in the southern part of the basin during the summer season. Trees like mango and tamarind are common. However, trees and shrubs of acacia are widely present along the roadside and along the hill- slopes. Due to their enormous and expeditious growth during rainy and winter seasons, their entangled thorny branches make the access to outcrops very difficult. Hence it is advisable to carry out field investigations during the summer season (in spite of the extremely hot climate), when the area is barren and outcrops are well exposed. Apart from agriculture, the band of bluish grey Chikshellikeri Limestone exposed near Bagalkot, Kaladgi, Chikshellikeri, Kerkalmatti, Lokapur, Jalikatti,

10 Introduction

Petlur etc. is exploited on a commercial scale for cement and for flagstones. As a result, a number of small cement factories dot the landscape.

1.5 METHOD OF STUDY The present investigation was carried out in the following phases: 1.5.1 REVIEW AND COMPILATION OF UTERATURE AND EXISTING DATA: Considerable literature survey through publications, including books, special volumes and research papers has been carried out during this study. This helped gain an insight into the current status of knowledge and the existing problems. Apart from this, the pre-field studies included the documentation and interpretation of remote sensing data. For this purpose two multispectral satellite imageries and panchromatic aerial photographs (1: 60, 000 scale) were utilised. The two satellite imageries were false colour composites of IRS-IA on 1:250,000 and 1:125,000 scales. The mapping methodology has been discussed in detail in the second chapter.

1.5.2 FIELD WORK: Field studies were carried out with the objective of detailed mapping, field checks and sampling along various traverses within the basin for better understanding of field relationships between various lithologies and deciphering their structural features. For this purpose several field visits were made to the study area. The results are given in Chapter-II.

1.5.3 LABORATORY STUDIES: Laboratory studies included: a) Preparation of Geological Maps: • Toposheets were scanned and digitised. • Pre-field interpreted maps were scanned and digitised. • Field information was plotted in the soft-copies of these maps. • Litho-boundaries were plotted using available data. From this base geological map, other thematic maps were derived. This process was performed using Corel Draw 8. The positional accuracies of the plotted data were verified during field studies.

b) Petrographic studies: The samples collected, were used for petrographic studies. About 150 thin sections were examined under optical microscope. Modal analysis was carried out, with the intention of generating data for the Provenance Discrimination Plots of Dickinson and Suckzec, 1979, and Dickinson, 1988). The results of these plots are discussed in detail in Chapter II, while the petrological characters are given in Annexure 2. The statistical analysis of the data was carried out using Lotus 123R5.

11 Introduction

X-ray diffraction of the argillites, was done to identify the submicroscopic minerals present. Powdered samples, without separating the clay fraction, (whole rock analysis) were used for preparing the X-ray diffractograms. Most of the argillites being ferruginous, an iron target was used as suggested by Hardy and Tucker, (1988) in order to avoid iron-fluorescent radiation. The diffractograms were analysed by comparing with the JCPDS database (1972,1974 and 1984). The samples of carbonates were first "acid etched" and then "stained" by the two stains Alizarin red Sand Potassium Ferricyanide as proposed by Dickson (1965 and 1966) to differentiate between calcite and dolomite in them. The staining of carbonate rocks by this method reveals the following colour differentiation of the minerals: Calcite Pink to red Ferroan calcite Mauve to purple to royal blue Dolomite Remains colourless Ferroan dolomite Pale to deep turquoise

c) Construction of lithologs and Fence diagram: The data collected during selected traverses was used for the construction of vertical lithologs (Annexure 1) and fence diagrams displaying distribution patterns of various lithologies across the study area.

d) Reconstruction of Geological Cross-sections: Geological cross-sections were constructed using the field traverses in order to highlight the interrelationship between the lithologies and structures like folds and faults. These cross sections were used to interpret and appreciate the three- dimensional distribution of various lithologies in the study area.

e) Construction of relative subsidence curves: The lithological data (thickness and their probable depths of deposition with respect to mean sea-level) was used to construct the sediment accumulation curves in order to show the subsidence patterns in various sectors of the basin. The data and results are given in Appendix 7.

1.6 OUTLINE OF THE THESIS

CHAPTER I: INTRODUCTION This introductory Chapter presents the aims and objectives of this study and states the techniques used. It defines the choice of the area and its attributes in terms of access climate and vegetation.

CHAPTER II: SEDIMENTOLOGY AND STRAHGRAPHY This chapter starts with a review of the previous work on this basin. A general regional geological-set up of this basin is explained next in great details. Facies analysis for intra-basinal correlation is one of the important sections of this chapter. Based on this exercise, the lacunae in the erstwhile classifications are pointed out

12 Introduction and a revised lithostratigraphic classification is proposed. The formal details of the revised classification are enumerated.

CHAPTER III: STRUCTURAL CoNPiGURAnoN This chapter documents and discusses the inherent as well as superimposed deformation structures observed in the basin and their controls on sedimentation patterns.

CHAPTER IV: SEQUENCE STRATIGRAPHY AND BASIN EVOLUTION This chapter contains the crux of the present geological investigations. A basic sequence stratigraphic scheme for the sediments of this basin is proposed here. The other half of the chapter has been dedicated in explaining the factors that governed the evolution of this basin.

CHAPTER V: SUMMARY AND CONCLUSIONS This chapter summarises the achievements and contributions of the present study. It enumerates the significant conclusions drawn from this study. A detailed discussion, integrating all the observations, measurements and computations undertaken during this investigation has been presented.

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