Stratigraphy and palaeoenvironment of the Cretaceous deposits of Narmada Valley, central India

This review presents a brief appraisal of the present understanding regarding the stratigraphy, depositional conditions, and paleogeography of the marine and fluvial sedimentation in the Narmada Valley in peninsular India in the background of global tectono-eustatic events and relative sea-level changes during the Cretaceous. The prevalent transgressive sequence in the epeiric basin signifies the effect of sea level rise under the Late Cretaceous greenhouse condition in the Narmada Valley in central India, resulting in initial fluvial–estuarine transition, followed by the development of a carbonate depositing tidal flat—lagoon—restricted shelf environment. The transgressive Bagh Group is overlain by a continental fluvio-lacustrine Lameta Group, often overlain and/or truncated by the Deccan Traps basalts. The characteristic biostratigraphy of the Bagh Group, the Lameta Group, and other intertrappean lithounits from the Narmada Valley, formed by invertebrate and dinosaur body fossils, dinosaur eggs and nests, and varied trace fossils, corroborates the depositional conditions. Stable isotopic analysis, accompanied by the sedimentological, biostratigraphic, and sequence stratigraphic models, portrays significant changes in the paleogeography in terms of ocean anoxic events, rising sea levels and marine encroachments in the tectonically active riftogenic Narmada Valley during the Cretaceous.