Maastrichtian to Eocene subsurface stratigraphy of the Cauvery basin and correlation with Madagascar

Abstract

Late Maastrichtian through middle Eocene planktic foraminiferal biostratigraphy and erosion patterns from three Cauvery basin wells are compared with the Krishna-Godavari basin, Madagascar and South Atlantic Site 525A. Maastrichtian sedimentation appears continuous at DSDP site 525A and substantially complete in the Cauvery basin and Madagascar for the interval from ~70.3 to 66.8 Ma (zones CF6-CF3). But the latest Maastrichtian through early Paleocene record is fragmented, except for some Krishna-Godavari and Cauvery basin wells protected from erosion by Deccan traps or graben deposition, respectively. Hiatuses are observed correlative with sea level falls at 66.8, 66.25, 66.10, 65.7, 63.8 and 61.2 Ma with erosion amplified by local tectonic activity including doming and uplift due to Deccan volcanism. Throughout this region the Cretaceous-Paleogene transition (magnetochron C29r-C29n, 66.25-65.50 Ma) is preserved only in deep wells of the Krishna-Godavari basin where Deccan Traps protected intertrappean sediments from erosion. The late Paleocene to middle Eocene marine record was recovered from two Cauvery basin wells with hiatuses correlative with low sea levels at ~49.0-56.5 Ma (zones P4c-E6) and ~53.0-55.3 Ma (zones E1-E4) at the ridge well KALI-H. A nearly complete record was recovered from well AGA, including the PETM event (zones E1-E2), which marks this an excellent reference section for India. Similarity in erosion and sedimentation patterns of the late Maastrichtian to middle Paleocene from India to Madagascar and South Atlantic is mainly attributed to climate changes and sea level falls, regional tectonic activity from the Bay of Bengal to Madagascar, and uplift and doming in the Cauvery and K-G basins as a result of Deccan volcanism. Directly correlative with Deccan volcanism are high stress environments for marine calcifiers, as observed by species dwarfing, reduced diversity and blooms of the disaster opportunist Guembelitria cretacea in magnetochron C30n (zones CF4-CF3) correlative with Deccan phase-1 and Ninetyeast Ridge volcanism, in C29r (zones CF2-CF1) correlative with Deccan phase-2 and in C29n (zone P1b) correlative with Deccan phase-3 marking volcanism as the most important stress factor in the end-Cretaceous mass extinction and delayed evolution of planktic foraminifera.