Kaladgi Basin Research Articles

Geochemical and Isotopic Investigation of Carbonate Deposits in the Central Kaladgi Basin, North Karnataka

Abstract Characteristic argillaceous-carbonate sediments covering parts of Belgaum, Bijapur and Bagalkot districts in north Karnataka have extensive deposits of high-grade limestone and have been commercially exploited since 1836. Despite their massive occurrence and commercial importance, the carbonate deposits in the Kaladgi basin have yet to receive enough attention. This study attempts to decipher the genetic aspects of the carbonate deposits occurring in the Neerubudihal region within the central part of the Kaladgi basin. The whole-rock carbon and oxygen isotopic compositions and the major and trace elemental compositions of the studied carbonates indicate that the rocks suffered a weak postdiagenetic alteration and retained the characteristics specific to the original diagenetic environment. The paleosalinity and palaeotemperature estimations reveal the carbonate precipitation in a stable marine environment in the study area with high salinity (av. 125) conditions at an average temperature of ~59 °C. The major and trace elemental studies classify the carbonates as dolomitic limestones and point to the dominance of the sedimentary process in their genesis. The carbon and oxygen isotopic studies suggest that the upper parts of the Bagalkot Group in the Kaladgi Basin had relatively lower organic content and diagenetic alteration than in the contemporary Bhima basin.

Inferring Paleocurrents using Imbrications in the Kaladgi Basin

Inferring Paleocurrents using Imbrications in the Kaladgi Basin

The elusive crustal resistive boundary beneath the Deccan Volcanic Province and the western Dharwar craton, India

The electrical properties of the boundary beneath the Deccan Volcanic Province and the western Dharwar craton are imaged by using the magnetotelluric method. The magnetotelluric study was carried out along a 150km long WNW-ESE profile from Belgaum (in the Deccan Volcanic Province) to Haveri (in the western Dharwar craton).Data from 19 magnetotelluric stations spaced 10-15km apart were used. The dominant regional geo-electric strike direction obtained is N20ºE. Two-dimensional (2-D) inversion is done by using the non-linear conjugate gradient scheme for both apparent resistivity and phase. The 2-D resistivity model shows a high electrical resistivity character (>10,000ohm-m) in the western Dharwar craton. Two conductive anomalies are mapped in the crustal region. In the WNW side of the profile, a conductive feature (~200ohm-m) is imaged in the mid-lower crust and, in the central part of the profile another conductive feature is mapped in the lower crust. The conductive features robustness is tested using linear and non-linear sensitivity analyses. The conductor mapped in the WNW part of the profile is considered as a deep seated fault representing a boundary or a rift related feature beneath the Deccan Volcanic Province and the western Dharwar craton. A zone of enhanced conductivity (<50ohm-m) at an approximate depth of 10-30km may represent the presence of the rift in the region. This conducting feature on the Western side of the E-W trending Kaladgi Basin can be interpreted as the extension of the Kaladgi Basin further west. A well-correlated geological cross-section is also derived to interpret the resistive features mapped in this study. The electrical resistivity nature of the crust is compared with other regions of the world.

Project-scale prospectivity analysis for unconformity-related uranium deposits in the Badami Group of the western Kaladgi basin, India

Developing successful exploration strategies for finding new ore deposits is a major challenge for exploration geologists, particularly, for concealed deposits in terranes with thick sediment cover. Proterozoic unconformity-related uranium deposits occur at, below, or above, unconformable contacts between Archean and Paleoproterozoic crystalline basement and siliciclastic sediments of middle or later Proterozoic age, often at locations where fault systems cut across either one or both of the geologic units that lie above and below the unconformity. The present study implements project-scale prospectivity analyses to identify drilling targets in the Badami Group of the western Kaladgi basin, India. Topographic profiles; field observations of breccia and lineaments; surface and sub-surface sampling; petrography and geochemistry; drill-core lithologs; and interpreted aeromagnetic anomalies were used to build a generalized local geological model of unconformity-related uranium deposits in the study area. Based on the geological model and a generalised mineral systems model, hydrothermal alteration, proximity to lineaments, proximity to unconformity surface, and anomalous uranium content on the surface and in the groundwater were identified as key project-scale targeting criteria. Seven high-priority drilling targets were mapped based on expert driven prospectivity analysis constrained by a GIS-based fuzzy prospectivity modelling. Out of these, four target areas coincide with the targets identified by the Atomic Minerals Directorate (AMD) of India based on their independent investigation. The three new targets from this study are recommended as targets for detailed exploration and drilling. In addition to this, about eight additional low priority targets were identified for follow-up exploration activities. This paper demonstrates that the prospectivity mapping methods can be applied at the project scale. The strategy demonstrated in this study can be used for exploration targeting in similar basins like the western Kaladgi basin that are structurally less disturbed.

C-Sr-Pb isotope systematics of the carbonate sequences of Kaladgi Supergroup, India: Implications for basin evolution and correlation with Proterozoic global events

The Kaladgi Basin is one of the several Proterozoic sedimentary basins of India. This basin has a binary evolutionary history with an angular unconformity separating the older deformed and younger undeformed rock sequences of the Kaladgi Supergroup, named the Bagalkot and Badami Groups, respectively. The Bagalkot Group is known to be of late Paleoproterozoic-Mesoproterozoic age. However, the timings of deposition of the Badami Group sediments and the closure of the basin have been speculative. We carried out C-O-Sr isotope studies of the marine carbonate successions of this basin namely Chitrabhanukot, Chikshellikeri, Lakshanhatti (Bagalkot Group), and Konkankoppa (Badami Group). Our results indicate that δ13C of all the carbonate formations have preserved the primary marine signature. Restricted variation of δ13C in the carbonates of the Bagalkot Group (0 ± 2 ‰) suggests a steady state organic carbon burial; whereas, much wider range of variation of δ13C in the Konkankoppa Limestone of Badami Group (-2.2 to + 3.5 ‰) hints at a dynamic organic carbon burial scenario. These signatures are consistent with the C-isotope stratigraphy of the Meso-Neoproterozoic times. The 206Pb-207Pb dating of the youngest unit of the Kaladgi Supergroup, the Konkankoppa Limestone yielded a depositional age of 604 ± 25 Ma. This age, considered together with the primary 87Sr/86Sr ratio of 0.70781, extends the active sedimentation of the Badami Group well into the Ediacaran Period. These data confirm the existence of a long duration depositional hiatus, of >500 million years, between the Bagalkot and the Badami Groups. Results of this study also refutes the claim that the sedimentation in most of the Proterozoic basins of peninsular India ended by 1000 Ma.

Clay mineralogy and provenance modeling of the Paleoproterozoic Kaladgi shales, Dharwar Craton, Southern India: Implications on paleoweathering and source rock compositions

Proterozoic clastic sediments reveal vast information regarding provenance, depositional conditions, and environmental evolutions. Peninsular India comprising Archean cratons, also have numerous intracratonic Proterozoic sedimentary basins along their margins. The Archean Dharwar craton in southern India has many Proterozoic successions, namely Cuddapah, Kurnool towards the East, and Kaladgi, Badami, and Bhima towards the northern margin. The Paleoproterozoic Kaladgi Basin (∼1.85 Ga) consists of siliciclastic sedimentary rocks with stromatolitic carbonate formations. XRD analysis of shale layers of the Lower Lokapur and Upper Simikere Subgroups have been carried out to understand the primary clay mineral assemblages, weathering history, and provenance. The Lower and Upper shale layers of Lokapur and Simikere Subgroups show a dominance of montmorillonite and kaolinite, respectively. The geochemical affinities and the clay mineral assemblages indicate a more mafic source to the lower shales (Manoli and Hebbal Formations) and increased felsic contribution to the upper shales (Govindakoppa and Daddanhatti Formations). Illite is ubiquitous in all the shales of the Kaladgi Supergroup possibly representing the diagenetic transformation of montmorillonite and kaolinite to illite. Geochemical modeling of provenance has been carried out using (Eu/Eu*)N, (La/Yb)N, (Gd/Yb)N, and (La/Sm)N of all the plausible source rocks and the average compositions of lower and upper shales. The modeling results suggest that the lower shales are derived from a source of mafic rocks – 45 %, K-rich granite – 35 %, and TTG – 20 %. While the upper shales are derived from source characterized by K-rich granites – 61 % and intermediate volcanic rocks – 39 %. These results signify the classical unroofing of TTG-greenstone belts exposing K-rich granites with the progression of sedimentation. Further, a good correlation between K-enrichment (a measure of % difference between CIA and pre-metasomatic CIA) and ƩLREE is attributed to the abundance of kaolinites that fractionate more LREE.

Mineralogy and Chemistry of Lakshanhatti Dolomite of Proterozoic Kaladgi Basin, Karnataka, India

Abstract The dolomites of Lakshanhatti Dolomite Member of Simikeri Subgroup of the Proterozoic Kaladgi Basin of Karnataka are medium to fine grained, compact and massive crystalline rocks, and are characterized by stromatolitic and cherty laminations. They are composed mainly of dolomite mineral with traces of calcite and quartz. The MgO content of these dolomites is almost uniform, and varies between 19.57 and 21.35%, while their CaO content varies widely from 30.24 to 38.39%. They are characterized by low SiO2 (av. 0.47%) and Al2O3 contents, indicating negligible amount of detrital quartz and clay fractions in dolomites. The higher contents of Fe (av. 5225 ppm) and Mn (av. 179 ppm) suggest for their substitution in Mg/Ca cations during dolomitization. The values of MgO (av. 20.47%), CaO (av. 35.07%) and insolubles like SiO2, Al2O3 and Fe2O3 (av. 1.31%) categorize these dolomites as refractory grade. It is inferred that the dolomites with stromatolitic structures were formed as primary precipitates due to microbial activity and minor evaporation in a tidal flat shallow marine environment, while the secondary dolomites were formed by the replacement of limestone during burial and diagenesis.

Mahakut Chert Breccia in Kaladgi basin, India: Unsolved Issues

Mahakut Chert Breccia in Kaladgi basin, India: Unsolved Issues

Study of structural, deformation temperature, and strain analysis of the quartzarenites of south-central Kaladgi basin, exposed at and around Mullur ghat and Kallur village of Belgaum district, Karnataka, India

Kaladgi rocks are magnificently exposed in Belgaum district of Karnataka state, with adjacent to Maharashtra, the Kaladgi Basin, evolved as a consequence of crustal extension which are resting on the basement of the Archaean Gneisses and are also overlaid by Deccan Traps. The outcrops in the present study area have very well-exposed quartzarenites of south-central part of Kaladgi Basin. New meso- and microscale structural analyses indicate that Kaladgi rocks suffered at least two episodes of deformation preserved in ductile and ductile-brittle structures. Finite strain analyses of the XZ and YZ sections on the collected samples from the Kaladgi basin show pure flattening strain pattern on Hsu and Flinn diagram. This simple flattening strain is attributed due to the sedimentation or lithological loading in the basin. This study area traversed by 3 transverse faults, namely F1, F2, and F3 through K-1, K-5, and M-4 locations, respectively. Finite strain analyses show high strain value in XZ section along the faults as F1 show 1.32 to 1.44, F2 has 2.3 to 1.45, and F3 reflect 1.57 Rs values. Deformation temperature based on the microstructures has high value along the faults as 400 to 500°C; however, rest of the area show low temperature deformation <300°C. This study brings new insights on deformation structures in field and under a microscope.

Discriminatory Analysis for Determining the Environment of Deposition of South-central Part of Kaladgi Basin, Belagavi District, Karnataka, India

Kaladgi rocks are very well exposed in Belgaum district of Karnatak state, with adjacent to Maharashtra state. The rocks exposed in the study area comprises mainly of quartzarenites which are sedimentary in origin. This study mainly focuses on determining the environment of deposition of the south-central part of Kaladgi basin. The rock samples collected (25) from the study area were subjected to the thin section studies and the dimensions of the grains were measured. Further, kurtosis, skewness, sorting, and mean size were obtained by using respective formulae. Thus, stating that these Kaladgi quartzarenites were formed under the beach environment in a shallow depth of water. The sediments deposited were mainly transported by rivers flowing from southernly located source rocks through traction and saltation.

Provenance, tectonics and palaeo environment of Mesoproterozoic Saundatti Quartzite Member of Kaladgi Basin, India: A petrographic view.

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 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 sub-group rocks that are exposed in and around Savadatti Town, Belagavi District of Karnataka. These rocks are mainly composed of Arenite sequences of varying grain size. The clastic succession comprises lithologies Sandstones with minor conglomeratic facies at the lower regimes. An attempt is made to identify the detailed petrographic character of the sandstones to understand the provenance and depositional environments based on the detailed petrographic observation. The study suggests that the coarse clastic conglomerates are essentially polymictic types and the sandstones are sub-mature to mature (mineralogically), medium to coarse grained and can be categorized mainly into lithic/feldspathic and quartz arenites. Minor occurance of feldspars as the framework constituent also suggests that the rock have undergone considerable transport. However with their variable degree of alteration (from fresh to partially alter to completely altered grains) associated with textural maturity and nature of Quartz point towards the possibility of derivation of these sediments from two different sources. Palaeocurrent data that indicate a NW palaeoslope suggest the derivation of sediments from a variety of granitic and gnesssic 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 preservation of much amount of feldspar in these sandstones is indicates a remote source and relatively dry-arid climate of the source area.

Petrography and Provenance Study of South-Central Part of Kaladgi Basin, Belgaum, Karnataka, India

The area under investigation covers the south-central part of Kaladgi series comprising of sedimentary rocks, mainly quartzarenites. From the geological point of view the study area comprises southcentral part of Kaladgi basin covering around 54 km2 which encompasses rocky hills of moderate height, showing three types of facies i.e., argillaceous, arenaceous and rudaceous. Among these three, arenaceous facies is more prominent in the area. These sedimentary rocks rest unconformably over gneisses. Detailed study of the rocks exposed are done by studying the petrological aspects of the rock samples which were subjected to microscopic studies, bifurcating different minerals and counting each parameter of the minerals which is plotted in the QFR ternary diagram and further illustrating the tectonic provenance of the area. Present work mainly focuses on the studies related to petrological, diagenesis and provenance of the study area where the rocks exposed in the vicinity are quartz arenites indicating that these sediments were deposited in a riverine condition.

Petrography and Provenance Study of South-Central Part of Kaladgi Basin, Belgaum, Karnataka, India

The area under investigation covers the south-central part of Kaladgi series comprising of sedimentary rocks, mainly quartzarenites. From the geological point of view the study area comprises southcentral part of Kaladgi basin covering around 54 km2 which encompasses rocky hills of moderate height, showing three types of facies i.e., argillaceous, arenaceous and rudaceous. Among these three, arenaceous facies is more prominent in the area. These sedimentary rocks rest unconformably over gneisses. Detailed study of the rocks exposed are done by studying the petrological aspects of the rock samples which were subjected to microscopic studies, bifurcating different minerals and counting each parameter of the minerals which is plotted in the QFR ternary diagram and further illustrating the tectonic provenance of the area. Present work mainly focuses on the studies related to petrological, diagenesis and provenance of the study area where the rocks exposed in the vicinity are quartz arenites indicating that these sediments were deposited in a riverine condition.

Petrological Study of Uranium-bearing Polymetallic Mineralisation in the Sediments of Badami Group of the Proterozoic Kaladgi Basin, Belgaum District, Karnataka.

Petrological Study of Uranium-bearing Polymetallic Mineralisation in the Sediments of Badami Group of the Proterozoic Kaladgi Basin, Belgaum District, Karnataka.

Correction to: Illite crystallinity index from the Mesoproterozoic sedimentary cover of the Kaladgi basin, southwestern India: Implications on crustal depths of subsidence and deformation

The grade of metamorphism and thermal maturity of the Mesoproterozoic Bagalkot Group in the Kaladgi basin of southwestern India has been determined using the illite crystallinity (IC) index. IC index was determined from the argillite samples of four stratigraphic levels viz., Ramdurg Formation (basal unit), Yargatti Formation (intermediate lower unit), Yadahalli Formation (intermediate upper unit) and Hoskatti formation (upper unit). IC index (Kubler equivalent) values range between $$0.54{^{\circ }}\Delta 2\theta $$ and $$0.24{^{\circ }}\Delta 2\theta $$ (in a set of 37 samples) and indicate a deep diagenetic to high anchizone metamorphic grade within a temperature range of $$\sim $$ 180 to 300 $${^{\circ }}\hbox {C}$$ . The Mesoproterozoic sedimentary cover of the Kaladgi basin is deformed due to southerly directed gravity gliding of the cover over the basement. The general variation of the IC index along and across the basin as indicated by the distribution of IC index values and isocryst contour patterns is due to the combined effect of deformation and variable subsidence of the Mesoproterozoic cover of the basin. Considering an average Mesoproterozoic geothermal gradient of $$35{^{\circ }}\hbox {C/km}$$ , the crustal depth of deformation and/or subsidence of the Mesoproterozoic cover up to the sample point is estimated to vary between 5.14 and 8.57 km.

Illite crystallinity index from the Mesoproterozoic sedimentary cover of the Kaladgi basin, southwestern India: Implications on crustal depths of subsidence and deformation

The grade of metamorphism and thermal maturity of the Mesoproterozoic Bagalkot Group in the Kaladgi basin of southwestern India has been determined using the illite crystallinity (IC) index. IC index was determined from the argillite samples of four stratigraphic levels viz., Ramdurg Formation (basal unit), Yargatti Formation (intermediate lower unit), Yadahalli Formation (intermediate upper unit) and Hoskatti formation (upper unit). IC index (Kubler equivalent) values range between \(0.54{^{\circ }}\Delta 2\theta \) and \(0.24{^{\circ }}\Delta 2\theta \) (in a set of 37 samples) and indicate a deep diagenetic to high anchizone metamorphic grade within a temperature range of \(\sim \)180 to 300\({^{\circ }}\hbox {C}\). The Mesoproterozoic sedimentary cover of the Kaladgi basin is deformed due to southerly directed gravity gliding of the cover over the basement. The general variation of the IC index along and across the basin as indicated by the distribution of IC index values and isocryst contour patterns is due to the combined effect of deformation and variable subsidence of the Mesoproterozoic cover of the basin. Considering an average Mesoproterozoic geothermal gradient of \(35{^{\circ }}\hbox {C/km}\), the crustal depth of deformation and/or subsidence of the Mesoproterozoic cover up to the sample point is estimated to vary between 5.14 and 8.57 km.

Timing of Cleavage Development in Relation to Folding and its Implications: An Example from the Deformed Mesoproterozoic Sedimentary Cover of Kaladgi Basin, Southwestern India

ABSTRACT Detailed analysis of cleavage-fold relationships in the Mesoproterozoic cover sediments of Kaladgi basin, south western India, revealed three types of timing relationships between cleavage and folds: (1) cleavage developed earlier than folds. (2) Cleavage developed later at some stage of folding and (3) non-development of cleavages in folds. In the first case cleavage developed earlier than the folding. Evidences that support such an interpretation include high cleavage-bedding angle throughout the fold, asymmetric fanning of cleavage in the folds with large fan angles and rotation of cleavage more in the steep and short limbs of asymmetric fold. In the second case, cleavage initiated later at some stage during folding which is evident from low cleavage fan angles, relatively low cleavage–bedding angles in the limbs of folds and the offset of bedding trace against cleavage trace due to pressure solution. Even though pressure solution is ubiquitous throughout the fold the effects of offset are more pronounced in the limbs compared to that in the hinge due to changing angular relationship of bedding and cleavage throughout the fold. In the third case, cleavage is absent in the folds resulting in its sporadic occurrences and reflects its diachronous nature. The final geometry of cleavage in relation to folds at any location is a combined effect of relative timing of cleavage development and mechanism of folding involving layer parallel shortening, flexural slip, tangential longitudinal strain, syn- to postfold flattening and hinge migration.

Depositional history and provenance of cratonic “Purana” basins in southern India: A multipronged geochronology approach to the Proterozoic Kaladgi and Bhima basins

Peninsular India is a collage of Archaean cratonic domains separated by Proterozoic mobile belts. A number of cratonic basins, known as “Purana basins” in the Indian literature, formed in different parts of the Indian Peninsula during extensional tectonic events, from Paleoproterozoic through Neoproterozoic times. In this contribution, we present a diversity of new geochronological data for different units within the Kaladgi and the Bhima basins, which overlie the western and eastern Dharwar cratons, respectively. The new geochronology data are discussed in terms of depositional history and provenance of these poorly understood Proterozoic intracratonic basins. For the Kaladgi Group, a U–Pb baddeleyite age of 1,861 ± 4 Ma obtained for a dolerite dyke intruding the Yendigere Formation is used to constrain the minimum age of deposition of the lower Kaladgi Group. This result demonstrates that this part of the succession is comparable in age to the Papaghni Group of the Cuddapah Basin, heralding onset of Purana sedimentation at ~1,900 Ma. The detrital zircon populations from the clastic rocks of the Kaladgi and Bhima basins show unique and distinct age patterns indicating different source of sediments for these two basins. Palaeocurrent analysis indicates a change in provenance from south or southeast to west or northwest between the Kaladgi and Bhima clastic sedimentation. New U–Th–Pb and Rb–Sr radiometric dates of limestones and glauconite‐bearing sandstones of the Bhima Group (Bhima Basin) and the Badami Group (Kaladgi Basin) indicate deposition at around 800–900 Ma, suggesting contemporaneity for the two successions. Thus, the unconformity between the Kaladgi Group and the overlying Badami Group represents a time gap of up to 1,000 Myr. These new results demonstrate the complex multistage burial and unroofing history of the Archaean Dharwar Craton throughout the Proterozoic, with important implications for exploration of metal deposits and diamonds in Peninsular India.

Implications of new $$^{40}\hbox {Ar}/^{39}\hbox {Ar}$$ 40 Ar / 39 Ar age of Mallapur Intrusives on the chronology and evolution of the Kaladgi Basin, Dharwar Craton, India

The Kaladgi Basin on the northern edge of the Dharwar craton has characters diverse from the other epicratonic Purana basins of Peninsular India. Sedimentological studies in the basin have established the presence of three cycles of flooding separated by an event of intra-basinal deformation accompanied by low grade incipient metamorphism. The overall structural configuration of the basin indicates its development by supracrustal extension accompanied by shearing in a trans-tensional regime during the Mesoproterozoic. This was followed by sagging that yielded Neoproterozoic sedimentation in a successor nested basin. \(^{40}\)Ar/\(^{39}\)Ar dating of an intrusive mafic dyke along the axial plane of a fold has yielded a plateau age of \(1154{\pm }4\,\hbox {Ma}\). This helps constraint the age of the various events during the evolution of this basin.

Analyses of Aeromagnetic Data to Delineate Basement Structures and Reveal Buried Igneous Bodies in Kaladgi Basin, Karnataka

ABSTRACT Aeromagnetic data overcome constrain of inadequate exposures and provide signatures of bodies beneath sediment cover. Present work on analysis of aeromagnetic data over western part of Kaladgi basin provided insight into the basement structures and their role in basin evolution. In the study area, the NW-SE and NE-SW are the major trends of magnetic lineament followed by E-W and N-S trends. Archean to Paleoproterozoic basement is manifested by two structural zones, NW-SE trends related to major lineaments within the basement and the NE-SW trends presumed intra-basinal fault systems which controlled the local depressions. The basin configuration deduced from depth to basement show that the Kaladgi basin is an open deep basin and divided into several sub-basins, separated by fault-controlled NE-SW and NW-SE oriented basement ridges. An intriguing find in the western part are the numerous scattered smaller-scale, circular or semicircular, distinct magnetic anomalies of moderate to strong magnetic signal with strong remenance. Analyses coupled with 3D inversions in combination with sub-surface probing reveal in-homogeneities within basement gneisses and supracrustal rocks of the Kaladgi basin, Dharwar craton. 3D inversions of these circular bodies, suggest that they are apophyses of the intrusions or alternatively as younger intrusive stocks. Sub-surface probing by boreholes over circular bodies revealed leucocratic granite with porphyritic texture emplaced as intrusive within the Chitradurga metasediments. This implies that these intrusives are post-Chitradurga schist and pre Badami sediments as they have not affected the latter. However, they can be presumed to be coeval to potassic granites, which intrude the eastern part of the western Dharwar craton in southern India, until geochronological data are available.