Upper Cretaceous planktonic foraminiferal biostratigraphy from the Rio Grande Rise: Site 516 of Leg 72, Deep Sea Drilling Project.

Abstract

Cretaceous sediments were recovered only at Hole 516F (Rio Grande Rise). Late Cretaceous planktonic foraminifers were found between 964 and 1235 m sub-bottom; they are assigned to the late Coniacian to the latest Maestrichtian. Frequency and preservation of planktonic foraminifers are moderate in the Upper Maestrichtian and deteriorate from there to the base. Only the upper Maestrichtian Abathomphalus mayaroensis Zone can be clearly delimited. Some of the more important zonal and stage boundary markers were not found. The Cretaceous/Tertiary boundary is well documented without any major hiatus, and in spite of the poorly recognized zonal boundaries, the Upper Cretaceous sequence is apparently continuous. -from Author