Calcareous nannofossil biostratigraphy, Deep Sea Drilling Project Leg 85, eastern equatorial Pacific.

Abstract

Pelagic sediments recovered during Leg 85 span the uppermost Eocene to Pleistocene interval in a series of fairly continuous sections. The calcareous nannofossils are normally not very well preserved in the cores from this leg; coccoliths, discoasters, and other morphologic types have been corroded and overgrown by secondary calcite. Poor preservation in some cases precludes a sharp and precise biostratigraphy at the subzonal level, although remarkably, most zones can be clearly identified. Middle Miocene markers are the most consistently troublesome, and it is suggested that Coronocyclus nitescens be introduced as an additional useful marker in this interval.-Authors