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.

Biostratigraphic Summary for Leg 138

“…Much of the information for Pacific sediments was summarized by Barron et al (1985a) in a review that was largely based on the successes of Deep Sea Drilling Project (DSDP) Leg 85 (Pisias et al, 1985;Barron et al, 1985b).…”

Miocene Planktonic Foraminifers at DSDP Site 289: Depth Stratification Using Isotopic Differences

“…The chronology follows the time scale of Berggren et al (1985) whereby paleomagnetic Anomaly 5 is correlated with paleomagnetic Chron 11. The foraminiferal datums are compiled from Shipboard Scientific Party (1975) and Srinivasan andKennett (1981a, 1981b), ages from Keller (1980), Berggren et al (1985), and Barron et al (1985), and magnetostratigraphic calibrations from Shipboard Scientific Party (1975), Keigwin(1982), Ryan etal. (1974), Miller etal.…”

“…(1985, Poore et al (1983), Berggren et al (1983), and Barron et al (1985). The calcareous nannofossil datums are compiled from Bukry (1975) and Shafik (1975), ages from Berggren et al (1985) and Barron et al (1985), and magnetostratigraphic calibrations from Haq et al (1980) and Miller etal. (1985).…”

Early to Middle Miocene Radiolarian Stratigraphy of the Kerguelen Plateau, Leg 120

“…Assuming that this FO represents the FAD of C. tetrapera and that the FAD of C. tetrapera is synchronous between the low-latitude Pacific and the Southern Ocean area studied, the interval from 118.5 to 117 mbsf can be placed in a time interval correlated with the interval from 22. 2 to 22.6 Ma, according to the stratigraphic age determination of the FAD of C. tetrapera by Barron et al (1985) and Berggren et al (1985), respectively.…”