Facies architecture and sequence development in a Neoproterozoic carbonate ramp: Lakheri Limestone Member, Vindhyan Supergroup, Central India

Outcrop-based study of high-resolution sequence stratigraphy (intra- and interfacies sedimentologic clues) in Neoproterozoic Lakheri Limestone, Central India, reveals definite signals for relative sea level variations and paleogeographic shifts between shallow beach-shoreface and distal-shelf. Depositional cycles in this carbonate formation are bound by unconformities or disconformities of ravinement origin. On outcrop scale the unconformities are sharp and irregular and marked by definite depletion in δ13C values of limestones. In the study area the entire Lakheri Limestone succession is divided into four depositional ‘sequences’ bound by type I unconformities. Different variants of system tracts (transgressive, highstand and lowstand), resulting from differences in paleogeographic locations, basin floor physiography and variable rates of relative sea level change, constitute the sequences developed on Lakheri carbonate ramp. A possible forcing of intrabasinal tectonics (both extension and compression) on meter to tens of meter thick Lakheri ‘sequences’ is inferred. impersistence (both along and across depositional strike) of Lakheri Limestone is an additional complexity in depositional architecture of carbonate ramp sequence. This possibly resulted from formation of depositional slope breaks through tectonic or depositional factors. Three-dimensional reconstruction of lowstand wedge brings out the control of rugged physiography of the basin floor (imparted through patchy biohermal growth) on facies distribution in this Neoproterozoic ramp succession.