Foraminiferal biostratigraphy and paleobathymetric trends across the Cretaceous-Tertiary boundary in Neyveli area, Cauvery Basin, India

Abstract

Five planktic foraminiferal biozones, namely, Abathomphalus mayaroensis zone, Pseudotextularia deformis zone, Parvularugoglobigerina eugubina zone, Globoconusa daubjergensis zone and Praemurica inconstans-Subbotina triloculinoides zone, are identified in the subsurface lithosection NY-KT, Cauvery Basin. The succession of planktic zones P. deformis of the terminal Maastrichtian (zones CF1–CF2) and P. eugubina (zone Pα of (Caron, 1985) = P1a of (Keller, 1993)) of early Danian denotes that the Cretaceous-Tertiary transition is relatively discontinuous with no major hiatus. The occurrence of ecological index benthic foraminifera Nuttallides truempyi and Bulimina trinitatensis in part of the A. mayaroensis (=CF2) and M. inconstans-S. triloculinoides (=P2) zones suggests that the paleodepth was >500 m while their absence reveals that sea level dropped below 500 m through biozones CF1, Pα, and P1. This observation is in conformity with the regional paleobathymetric trends across the KTB in the Cauvery Basin.