Proterozoic Vindhyan Basin Research Articles

GIS based integration of multi-spectral remote sensing and morphostructural analysis for delineating potential areas of hydrocarbon exploration in Western Vindhyan Basin, India

The Chambal Valley forms the western part of the Proterozoic Vindhyan Basin that has been less studied and poorly explored from the hydrocarbon perspective than its eastern counterpart—the Son Valley Vindhyans. In the present manuscript, attempts have been made to use remote sensing and GIS (geographic information system) based analysis to focus on the northern part of Chambal Valley to decipher its tectonics and structural configuration, its tectonic relation with the Son Valley Vindhyans, Bundelkhand Massif and Ganga Basin. This study also assumes significance as it attempts to delineate potential lead areas for hydrocarbon exploration in Chambal Valley. As part of the study, a detailed spectral analysis based on image data sets is carried out to identify areas of microseeps as proxies of potential hydrocarbon accumulations. Also, a neotectonics-based geomorphic analysis is carried out to delineate a fault network and geomorphic highs that act as aliases to subsurface faults and structural highs. The results are subsequently validated by available geophysical data and extensive fieldwork, and suggest four structural trends in the Chambal Valley as striking NE-SW, E-W, NW-SE and N–S, of which the NW-SE trend is the oldest, followed by the NE-SW, E-W and N–S trends. A GIS-based analysis of the E-W trends indicates that these are probably manifestations of the westward continuity of E-W-trending shear zones developed in Bundelkhand massif within the basement of the Chambal Valley. Further remote sensing studies of the shear zone network exposed in the Bundelkhand massif indicate the pattern to be replicated on a larger scale in the morphostructural fault layout in the adjacent Ganga Basin, implying these shear zones may be continuing in the basement of Ganga Basin and controlling structures developed later, and consequently the different petroleum system elements in the basin. A dip data based structural analysis of the Chambal Valley describes a regional synform attributed with an almost vertical NW-SE-trending axial trace. This axial trace may be in continuity with the NE-SW-trending synformal axis of the Son Valley with its trajectory sympathetic to the southern boundary of the Bundelkhand massif and the Central Indian Tectonic Zone (CITZ) – Aravalli Delhi Fold Belt (ADFB) geometry. Finally, based on the integration of the results of spectral and morphostructural analysis, a number of potential areas of hydrocarbon exploration are demarcated in the study area.

A combined geochemical, Nd, and stable Ca isotopic investigation of provenance, paleo-depositional setting and sub-basin connectivity of the Proterozoic Vindhyan Basin, India

Geochemical and isotopic investigation of Proterozoic clastic and chemical sedimentary rocks provide insights into surface conditions of the early Earth. The mid-Proterozoic Vindhyan Basin of central India, comprising ~5 km thick, mostly undeformed and unmetamorphosed clastic and chemical sediments, is one such archive which is exposed in two sub-basins, the Son Valley Vindhyan sub-basin in the east (SVV) and Chambal Valley Vindhyan sub-basin in the west (CVV). Geochemical and Nd isotopic compositions of siliciclastic sedimentary rocks from the CVV sub-basin are reported in order to understand the provenance of the Vindhyan sediments in this sub-basin and the results are compared with the provenance of the sediments exposed in the SVV sub-basin to evaluate whether the two sub-basins had shared a common provenance. Elemental ratios, such as Th/Co, La/Sc suggest that the clastic sedimentary rocks from the CVV have dominantly upper crustal silicic/felsic provenances and are broadly similar to those of equivalent stratigraphic horizons from the SVV. Initial Nd isotopic composition (εNd(t)) of the siliciclastic rocks from the Lower Vindhyans of the CVV, calculated at their respective times of deposition, suggest sediment derivation from the Banded Gneissic Complex, Berach Granitoids, 1.82 Ga continental arc granitoids of the Aravalli Range and the Hindoli Volcanics. In contrast, the εNd(t) values of the Upper Vindhyan siliciclastics suggest that the Delhi Belt granitoids were the primary source of detritus during the deposition of these sediments. Paleo-depositional environment and connectivity between the SVV and CVV sub-basins are evaluated using geochemical, radiogenic Nd, and stable Ca isotopic compositions of carbonates from both sub-basins. Non-redox sensitive REY anomalies and Y/Ho ratios of carbonates from the two sub-basins suggest deposition in an epeiric sea with limited connection to the open ocean. Neodymium isotopic compositions of the carbonate units suggest that the two sub-basins were connected during the deposition of both Lower and Upper Vindhyan sediments. Carbonates from both sub-basins record a significant shift towards more radiogenic Nd isotopic compositions around 1.6 Ga, possibly as a result of an Andean-type arc magmatism in near vicinity of the Son Valley sub-basin. The δ44/40Ca compositions of the SVV carbonates are typically lower than the CVV carbonates. This difference is likely due to greater freshwater input in the SVV sub-basin which is consistent with the existence of paleo-gradients in the Vindhyan Basin.

Environmental issues in karst terrain: an example from Central India

In this paper, an attempt has been made to highlight the nature of karst in central India and evaluate possible effects of environmental degradation of groundwater due to indiscriminate disposal of various types of wastes into karst terrains without subjecting them to any treatment before disposal. Karst features associated with carbonate rocks of the Proterozoic Vindhyan basin in central India and environmental issues related to the same area’s groundwater resources are briefly given. Based on the process of formation, karst may be categorized as True karst (holo-karst) and (ii) Fluvial karst. On the other hand, based on the types of cover, karsts are classified into three types: (i) Covered karst, (ii) Soddy karst, and (iii) Buried karst. Three types of karst landforms identified in carbonates rocks of the Vindhyans are (i) Superficial landforms (Karren), produced mainly by solution action on the rock surfaces, (ii) Landforms due to fluvial erosion, and (iii) Underground landforms, i.e., Caves. In a particular hydrogeologic setting, the groundwater system consists of minor secondary porosity modified by solution activities. Accordingly, two types of groundwater flow systems (diffuse and conduit) occur in carbonate rocks. Due to karstification, limestones constitute the most productive aquifer in the area. It is noted that untreated municipal and industrial wastes are disposed of directly in surface water bodies and streams and associated sinkhole depressions in limestone terrain. Secondary openings being interconnected with each other gradually carry these pollutants to groundwater reservoirs in karst aquifers. The continued influx of pollutants to groundwater reservoirs through interconnected secondary voids would cause severe groundwater pollution in the long run and degrade the groundwater quality in karst aquifers for various usages.

Chapter 6 Proterozoic Vindhyan Basin: configuration and evolution

Abstract This chapter attempts an understanding of the Proterozoic Vindhyan Basin history in the broad framework of central India. Although the entire Vindhyan Supergroup is within the scope of this work, particular attention is paid to the little-known northwestern fringe exposures. Distinctive facies assemblages and diverse palaeocurrents in these exposures of the Lower Vindhyan play a pivotal role in the interpretation. Analysis of outcrop and subsurface data that extend under the Gangetic alluvium to the north of the Vindhyan outcrops further supports the hypothesis that an east–west-elongated basement ridge initially separated the master Vindhyan Basin from smaller contemporary basins to the north. Deposition took place in isolated lacustrine and fluvial basins north of the divide and largely in a marine realm south. Dextral shear accompanying rifting generated ridges that criss-crossed the Lower Vindhyan seafloor to the south. The uniform character of the Upper Vindhyan throughout, nevertheless, testifies to later drowning of the divide and unification of all of the basins as a consequence of regional tilt northward. However, the extended Vindhyan Sea was restricted by a second east–west-elongated ridge from merger with the contemporary Proterozoic sea further north, disparate sediments of which have been encountered in a few drill cores only.

Geo-microbiological studies in conjunction with different geo-scientific studies for the evaluation of hydrocarbon prospects in Proterozoic Vindhyan Basin, India

Abstract The Proterozoic Vindhyan Basin is considered to be prospective for hydrocarbons and is grouped under category III sedimentary basins of India. The major part of the study area is covered by the Deccan Traps, hindering the exploration of Mesozoic hydrocarbon targets, surface geochemical prospecting based on microseepage of hydrocarbons from subsurface accumulations, which could be advantageous in such areas. Geo-microbiological study was carried out in conjunction with different geo-scientific studies to characterize the seeping natural gases and to evaluate the hydrocarbon prospects of the study area. Total 70 soil samples were collected in reconnaissance pattern, and the study revealed the presence of high bacterial counts for methane (3.7×10 5 cfu/g), ethane (3.2×10 5 cfu/g), propane (3.0×10 5 cfu/g) and butane oxidizing bacteria (2.3×10 5 cfu/g), which signify the seepage of hydrocarbons from the subsurface. The compositional characteristics of the hydrocarbon gases desorbed from soil samples of study area indicate the presence of light gaseous hydrocarbons methane through butane, thus suggesting that hydrocarbon generation has taken place in the basin probably of thermogenic origin. The trend followed by the hydrocarbons C 1 >C 2 >C 3 > i C 4 > n C 4 further confirms the petroliferous nature of the gases. The stable carbon isotope values of light hydrocarbons desorbed form the soil samples indicate a clear signature of thermogenic gas. The concentrations of TOC and TIC in the soil samples of Sagar vary from 0.09% to 0.93% and 0.003% to 0.82% respectively. The TOC and TIC correlates poorly with the adsorbed soil gases ( r =0.3, r =0.2), representing a lack of association of adsorbed soil gases with the surfacial organic matter thus indicate seepage related surface anomalies. The study revealed the presence of high concentrations of hydrocarbon oxidizing bacteria and adsorbed soil gases near Sagar area of Vindhyan Basin. The integrated geo-scientific studies showed excellent correlation and suggests that the Sagar area is considered to be potential for hydrocarbon generation and entrapment.

Depositional history of the Upper Vindhyan succession, central India: Time constraints from Pb–Pb isochron ages of its carbonate components

Age of the upper sedimentary units (Rewa and Bhander Groups) of the largest Proterozoic Vindhyan Basin in central India has so far been considered to be close to 650Ma (late Neoproterozoic) based on collective proxy dates in the absence of direct isotopic dates. A drastic upward revision of this age by more than 300Ma has very recently been proposed from the similarity of the paleomagnetic directions in these units with those of the 1070Ma old Majhgawan kimberlite intrusion into their basal parts, and the presence of detrital zircons not younger than 1020Ma. We report now Pb–Pb isochron ages of 908±72Ma, 866±180Ma and 1073±210Ma for the three distinct carbonate horizons, Bhander-, Balwan- and Lakheri Limestones, respectively as independent and direct evidence on the age of the Upper Vindhyan succession. The consistency of the three ages close to 900Ma provides a strong support for the proposed shift on the timing and duration of sedimentation in the Upper Vindhyan sequence.

Crustal structure beneath the Archean–Proterozoic terrain of north India from receiver function modeling

The shear velocity structure of the north Indian crust comprising of the Archean cratons (Aravalli–Bundelkhand) and Proterozoic Vindhyan basin is modeled and compared with the eastern Dharwar craton as well the global models for Archean and Proterozoic terrains. The velocity structure is deduced from joint inversion of teleseismic receiver function time series and surface wave group velocity measurements. The north Indian Archean crust is a simple two layered: an average Vs∼3.3±0.1km/s in the upper 10km increasing to 3.7±0.1km/s in the 26–28km thick lower crust. This upper crustal velocity is significantly less compared to those of either eastern Dharwar craton (3.5–3.6km/s) or the global average. These results suggest presence of a highly silica rich upper crust and an intermediate composition of the lower crust. The Moho is modeled at a depth of 36–38km with thin transition (∼2km) similar to those in eastern Dharwar craton. In contrast, the Proterozoic Vindhyan basin has significantly deeper Moho (44–46km) with a 4–10km thick underplated layer (Vs⩾4.0km/s) at the base of the crust. The sedimentary layer thickness is ∼2–4km. The results support the view that Proterozoic crust is thicker and underlain by a mafic layer at its base in contrast to a thin Archean crust with near absence of the basal layer as observed globally.

Maximum Likelihood Deconvolution for sequence analysis and improved structural resolution in the Vindhyan Basin, India

Exploration in the Proterozoic Vindhyan Basin in the north-central part of India has received much attention because a number of basins coeval to it (Amadeus and McArthur basins, Australia and Lena–Tunguska petroleum province, Siberia) are known hydrocarbon producers. The assemblage of interbedded clastics and carbonates in the thick Vindhyan sedimentary column is considered to be favourable for a petroleum system. This is supported by discovery of oil and gas in Vindhyan sediments. Wavelet processing and application of Maximum Likelihood Deconvolution (MLD) to post-stack seismic data have enhanced resolution significantly to facilitate identification of various stratigraphic features, including reflection pattern termination in the Jabera–Damoh area in the southeastern part of the basin. Sixteen seismic sequences correlatable with well data have been identified from the wavelet-processed data. MLD has also improved structural resolution and made identification of faults easier. This paper shows that MLD is a powerful tool for seismic sequence stratigraphy.

Trace element and Nd-isotopic evidence for sediment sources in the mid-Proterozoic Vindhyan Basin, central India

Ancient sediments reflect the compositions of old eroded continental crustal material and preserve geochemical signatures of paleo-tectonic and volcanic events. Geochemical study of such sediments provides insight into tectonic events that shaped the face of the Earth. Nd isotopes are best suited for such studies because rare earth elements (REE), specifically Sm and Nd are not fractionated during post-depositional processes such as erosion, transportation and diagenesis of organic-poor sediments and hence reflect the source composition of these sediments. Sedimentation in the Proterozoic Vindhyan Basin of central India with a ∼4 km thick succession of unmetamorphosed and mostly undeformed sediments lasted over 1000 Ma from ∼1630 Ma up to the Precambrian–Cambrian boundary. These sediments provide an ideal opportunity to study the evolution of ancient continental crust as well as the tectonic evolution of Peninsular India. The occurrence of porcellanites in the lower part of the basin indicates active volcanism during deposition of the Vindhyan sediments. These tuffs show large ion lithophile element (LILE) enrichment as well as depletions in Nb and Ta in primitive mantle-normalized plots, characteristic of an arc volcanic source. In combined trace element ratio plots, these volcanic rocks indicate mixing between mantle-derived melts and the continental crust and overlap with the composition of global arcs. Their initial ɛ Nd at 1630 Ma, ranging from −5.7 to −0.9, is similar to those observed in ‘Andean-type’ continental margin arcs. Trace element concentration patterns as well as Nd isotopic compositions of the clastic and non-clastic sediments of the Vindhyan Basin, from one of the type-localities of the Vindhyan stratigraphy in the Son valley, are vastly different from those of the Bundelkhand granite, which is the basement for these sediments, indicating that these granitic rocks were not a major source of sediments for the Vindhyan Basin. Our Nd isotopic study clearly indicates that sedimentation in the Vindhyan Basin, which lasted over ∼1 Ga, was not continuous. The boundaries between the Semri and Kaimur Groups as well as the Rewa and Bhander Groups are characterized by abrupt changes in the Nd isotopic compositions indicating changes in provenance, with sediments in the Kaimur and Bhander Groups being derived from more juvenile sources compared to the Semri and Rewa Groups, respectively. This inference is also supported by changes in T DM and f Sm/Nd for the sediments across these boundaries. The strikingly different trace element patterns of the Rewa Group sediments compared to the underlying Kaimur sediments indicates that sediment sources also changed across the Kaimur–Rewa boundary. Multiple changes in provenance in the Vindhyan sediments indicate that this basin was tectonically active during the entire span of sedimentation. While there is some uncertainty in determining the exact sources of sediments for the Vindhyan Basin, we argue on the basis of our geochemical, in particular Nd-isotopic ratios data, and available paleocurrent data that majority of the sediments were derived from a now-extinct Andean-type arc source in the south that resulted from a southerly dipping subduction prior to the collision of the Bhandara and Bundelkhand cratons. According to this reconstruction, the Vindhyan Basin was initiated as a foreland Basin after the collision of these two cratons.

Deep seismic reflection study over the Vindhyans of Rajasthan: Implications for geophysical setting of the basin

This paper presents results of high-resolution deep seismic reflection profiling of the Proterozoic Vindhyan basin of the Rajasthan area along the Chandli-Bundi-Kota-Kunjer profile. Seismic images have been used to estimate the thickness of Vindhyan strata as well as to understand the tectonic framework of the basin. The results are constrained by gravity, magnetic and magnetotelluric data. The study reveals gentle SE-dipping reflection bands representing the Vindhyan strata. The seismic sections depict gradual thickening of the Vindhyan succession towards southeast from Bundi. The velocities of the upper and lower Vindhyans are identified as 4.6-4.8 km/s and 5.1-5.3 km/s. The NW limit of the Vindhyan basin is demarcated by the Great Boundary Fault (GBF) that manifests as a 30 km wide NW dipping thrust fault extending to a depth of 30 km.

Outcrop signatures of relative sea level fall on a siliciclastic shelf: Examples from the Rewa Group of Proterozoic Vindhyan basin

The Rewa Group of the Vindhyan Supergroup in the Son valley begins with a thick (∼200m) dominantly shaly, shelfal succession, occurring between the Dhandraul Formation of the Kaimur Group (fluvial sandstone) below and Drammondganj Formation of the Rewa Group (marginal marine sandstone) above. Such a stratigraphic disposition indicates a sharp rise in relative sea level at the onset of Rewa sedimentation, inducing a shelfal depth to the Vindhyan basin. However, a number of wedge-shaped, sandstone/conglomerate bodies (maximum thickness 23.5 m) occur at multiple stratigraphic levels within the aforesaid deeper water shale succession, which appear to be of much shallow water origin representing regressive deposits. Though these bodies do not define a single physically continuous unit, either vertically or laterally, they are still designated by a single term ‘Asan Sandstone’ in the literature. On the other hand, the encasing shelfal shales are termed as Panna and Jhiri Shales, in accordance with their occurrence below or above the so-called ‘Asan Sandstone’. The present study reveals that in different sections spread over the Son valley, there are several discrete regressive wedges occurring vertically, and their depositional environment is also variable, ranging between braided fluvial, shoreface fan and braid delta. The features common to most of the regressive coarser clastic bodies are: •invariable presence of deeper water, shelfal shale below (Panna or Jhiri); •the underlying shale at places shows signatures of emergence at the top; •laterally impersistent, wedge-like geometry; and •presence of granular transgressive lags at the top. These coarser clastic wedges record several episodes of regressive deposition during short-term falling stage or lowstand of relative sea level at the early phase of Rewa sedimentation. Each individual phase of regressive deposition was, however, followed by flooding and resumption of shelf mud deposition.

Ediacara fossil assemblage in the upper Vindhyans of Central India and its significance

A fossil assemblage of soft-bodied megascopic metazoans possessing faunistic, ecological and taphonomic affinities to known classical Ediacaran assemblages has been discovered from the Proterozoic Vindhyan Basin of India. The assemblage is represented by nine coelenterate genera ( Tribachidium, Eoporita, Kaisalia, Cyclomedusa, Ediacaria, Nimbia, Paliella, Medusinites and Hiemalora), one arthropod genus Spriggina and a few unnamed possible new forms belonging to sponge and coelenterate. These fossils show facies-controlled temporal distribution forming two fossil zones: F 1 and F 2 located, respectively, in the Lakheri and Sirbu Formations (Bhander Group). A majority of them is common to the Ediacara assemblages of several continents, thereby suggesting their global biogeographic distribution. F 1 and F 2 in the local stratigraphy are separated by a thick stromatolitic carbonate facies devoid of metazoan remains. The Vindhyan Ediacara and host rock sequences reveal energetic (wave-tide-storm induced), shallow marine and near-shore environments of deposition of siliciclastic terrigenous facies. The carbonate facies parting suggests interruption of typical Ediacara environments by a broad spell of lime-rich quieter water settings favoring selective growth of metaphytes. The Vindhyan fossils show both Nemiana (higher relief forms without finer features in sandstones, e.g. Cyclomedusa and Ediacaria) and Beltanelliformis (lower relief forms with finer features in shales, e.g. Kaisalia and Hiemalora) types of preservation. Wide biogeography and ecological uniformity qualify the Vindhyan fossils as biostratigraphically significant group that fixes the age of the Lakheri–Sirbu segment at latest Neoproterozoic, helps in intercontinental correlation of the Bhander Group and focuses supra-Sirbu sequence as potential bearer of early Cambrian organic signatures. Predominance of forms representing Cycloza, an archaic group having monaxonic heteropolar symmetry of infinitely high order (e.g. Cyclomedusa) in F 1 and Inordoza having high order radial symmetry (e.g. Hiemalora) and Trilobozoa, an advanced group with fixed order radial symmetry (e.g. Tribachidium) in F 2 is consistent with the early evolutionary trend of coelenterates. Association of bilateral arthropod Spriggina, commonly thought to be ancestral to Arthropoda and Annelida now separated by huge phylogenic gulf, with possible discoid sponge of high-level organization and coelenterates suggests phyletic diversity of the Vindhyan Ediacara.

Sorption behavior of heavy metal pollutants onto shales and correlation with shale geochemistry

The sorption of lead (II) and cadmium (II) on seven shales belonging to the Proterozoic Vindhyan basin, central India, and a black cotton soil, Mumbai, India, was studied and compared with sorbent geochemistry. The sorption equilibrium studies were conducted under completely mixed conditions in batch reactors (pH=5.0 and ionic strength= 0.01 M) at room temperature. The Freundlich model provided better fits to the experimental data compared to Langmuir model. High cadmium and lead sorption was observed for the calcareous shales with greater than 5% CaCO3. The Freundlich isotherm parameter relating to sorption capacity, i.e., KF, yielded a strong correlation with the calcium carbonate and calcium oxide content across the various geosorbents studied. The observed sorption pattern may be attributed to complex formation of CaCO3 with Pb2+ and Cd2+ leading to surface precipitation. Moreover, the Ca2+ present in the sorbents may also involve in ion exchange reaction with lead and cadmium.

An Ediacaran fossil Spriggina (?) from the Semri Group and its implication on the age of the Proterozoic Vindhyan Basin, Central India

An Ediacaran fossil Spriggina (?) from the Semri Group and its implication on the age of the Proterozoic Vindhyan Basin, Central India