New latitude-based nannofossil zonations for the Campanian–Maastrichtian of the South Atlantic Ocean and their paleoceanographic implications

Abstract

The global evolution of calcareous nannofossils during the Campanian–Maastrichtian interval is not fully understood, and nannofossil zonations for the central and South Atlantic Ocean are yet to be constructed. Here, we test the applicability of previous calcareous nannofossil zonations developed for other ocean basins, for biostratigraphy in the South Atlantic Ocean, and refine Campanian–Maastrichtian biostratigraphy in the region. We document calcareous nannofossil distributions at Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) sites from the high, mid and low latitudes in the South Atlantic Ocean (DSDP Sites 354, 356, 511, 525A, and 530A, and ODP Sites 690C; 700B; 661A, and 1258A). Combining nannofossil occurrences with magnetostratigraphic schemes previously constructed for some of the sites, we propose three new zonations tied to the global magnetostratigraphic chrons, with distinct bio-horizons selected at different latitudinal regions. In this study we present detailed definitions of new South Atlantic Ocean Low-latitude (SAL), South Atlantic Mid-latitude (SAM) and South Atlantic High-latitude (SAH) zonations. We identified significant diachronism of some species between latitudes throughout the Campanian and Maastrichtian. These species diachronism, mainly between zonal markers from low and mid latitudes during the late Maastrichtian, was probably related to migration patterns due to fundamental paleoceanographic changes.