Cretaceous-Tertiary boundary marine extinctions: The Russian platform record

Abstract

Floral, faunal and stable isotope evidence in a continuous sequence of latest Cretaceous and earliest Tertiary shallow water marine deposits in the Mangyshlak Peninsula, USSR suggest sudden and severe cooling possibly accompanied by increased salinities of the surface water al the Maastrichtian/Danian (M/D) boundary, immediately followed by marked warming and decreased salinities. Geologic evidence indicates that the temperature decline was coeval with widespread and intense volcanic activity which reached a peak at the close of the Mesozoic Era. Volatile emissions led to acid rain which depressed the pH of surface water. lncreased acidity temporarily prohibited calcite nucleation of the surface dwelling warm-water plankton. Superimposed upon decreased alkalinity, severe and rapid climatic changes caused the extinction of calcareous phyto and zooplankton.

These results provide the most complete nanno, micro and macrofossil data as well as geochemical and clay mineralogical record from a single region across the paleomagnetically dated Cretaceous/Tertiary (K/T) boundary to date.