Synthesis of biostratigraphy, central equatorial Pacific, Deep Sea Drilling Project Leg 85: refinement of Oligocene to Quaternary biochronology.

Abstract

Biostratigraphic studies using planktonic and benthic foraminifers, calcareous nannofossils, radiolarians, diatoms, and silicoflagellates are summarized for the four main sequences (sites 572 to 575) collected during DSDP Leg 85 in the central equatorial Pacific. Upper Eocene through Quaternary reference sections were recovered at Sites 573 and 574, and middle Miocene through Quaternary and lower Miocene through Quaternary reference sections were cored at Sites 572 and 575, respectively. Detailed graphic correlation plots suggest that Site 573 may contain as many as nine short hiatuses. Site 572 in the fertile eastern equatorial Pacific is apparently free of hiatuses, and Sites 574 and 575 have hiatuses (two each) only in the compressed upper sections. Few inconsistencies exist in the various microfossil stratigraphies. Diachronous species occurrences are identified, and age estimates for 66 late Eocene through Quaternary microfossil datums have been extrapolated from age-vs.-depth plots constructed from 63 datums with direct and/or indirect ties to paleomagnetic stratigraphy. An addendum presents an alternative biostratigraphic time scale for the middle and late Miocene based on a correlation of paleomagnetic Anomaly 5 with paleomagnetic Chron 11. -Authors