Lithofacies of transgressive–regressive sequence on a carbonate ramp in Vindhyan basin (Proterozoic): a case of tidal-flat origin from central India

Abstract

Palaeoenvironment of late Proterozoic carbonate deposits of Vindhyan basin of central India has been studied using lithofacies analysis, petrographical character and sediment dispersal patterns. Based on field parameters, 12 lithofacies were identified from five sections. For environmental interpretation, these lithofacies have been grouped into two major lithofacies associations namely a lower association A comprising reefal lithofacies, algal lithofacies, oolitic-intraclastic lithofacies, stromatolitic limestone lithofacies and an upper lithofacies association B, which includes nodular limestone lithofacies, large-scale planar cross-bedded lithofacies, parallel and ripple cross-laminated lithofacies, lenticular and flaser bedded lithofacies, shaly limestone lithofacies, synaeresis cracked lithofacies, deformed limestone lithofacies and finally, channelized and sandy limestone lithofacies. Reefal lithofacies and oolitic-intraclastic lithofacies were deposited under subtidal conditions. Synaeresis cracked lithofacies, lenticular and flaser bedded lithofacies, channelized and sandy limestone lithofacies were deposited under intertidal conditions whereas stromatolitic limestone lithofacies deposition ranged between subtidal to intertidal domains. Lithofacies character of the rock succession as well as the microfacies associations recognized petrographically indicate that the depositional environment belongs to platform interior with restricted circulation to marginal sand shoals in a carbonate ramp setting. Due to calcium-carbonate-saturated water, the diagenesis took place in stagnant marine phreatic environment where little compaction occurred, with abundant micrite as primary groundmass, and rapid cementation by calcite took place. With palaeocurrent current direction towards south and azimuthal dispersion of 270°, a pattern akin to a marine system is corroborated.