Magnetostratigraphy and Sedimentology of Deccan Intertrappean Succession from Sagar, Central India: Insights into Palaeoenvironment and End-Cretaceous Palaeogeography

Abstract

ABSTRACT The study of Deccan volcano-sedimentary successions is significant for understanding the palaeomagnetic correlation, eruption history and palaeoenvironmental conditions of the Central India during the Cretaceous-Paleogene (K-Pg) transition. In this study, we applied an integrated magnetostratigraphic and sedimentological approach to the Deccan Intertrappean Succession exposed at the Mothi Hill (Malwa Subprovince), Sagar, to provide palaeomagnetic age constraints for the lava flows, depositional environment and end-Cretaceous palaeogeography. Palaeo-magnetic data suggest that the lower and upper Trap lava flows associated with the Mothi Intertrappean deposits are not coeval, and they correspond to C29r and C29n magnetochrons, respectively, which points to the age duration of 66.3–65.1 Ma (late Maastrichtian-early Danian). The palaeomagnetic data also marks the presence of upper magnetic polarity transition (C29r/C29n) in the eastern part of the Malwa Subprovince, which indicates the occurrence of C30n-C29r-C29n magnetostratigraphic sequence for the Subprovince. The Malwa, eastern Mandla and Western Ghats Subprovinces can be palaeomagnetically correlated and are partly synchronous with each other. The Mothi Intertrappean deposition occurred in a low energy shallow water lacustrine setup with swampy to brackish depositional condition similar to shallow coastal lake type environment. The occurrence of such coastal type depositional environment at Sagar in the central part of India, points to the influence of temporary marine incursion and existence of marine pathway up to Central India, possibly through the western corridor of Narmada-Tapti rift zone during the late Maastrichtian-early Danian period. Moderate to intense chertification within the argillaceous limestone suggests post-depositional diagenetic modification and secondary silica generation due to interaction with silica enriched meteoric water diagenesis.