27. PLIOCENE STABLE-ISOTOPE RECORD OF DEEP SEA DRILLING PROJECT SITE 606: SEQUENTIAL EVENTS OF 18O ENRICHMENT BEGINNING AT 3.1 MA1

• Main Authors: L. D. Keigwin, Woods Hole
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Shackleton; North Atlantic Deep Water; North Atlantic; Northeast Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.473.7525; http://www.deepseadrilling.org/94/volume/dsdp94pt2_27.pdf

Stable-isotope analysis of two species of benthic foraminifers (Planulina wuellerstorfi and Globocassidulina subglo-bosá) and one planktonic species (Globigerina bulloides) from DSDP Site 606 reveals the evolution of late Pliocene cli-mate change. No "stepwise " increase is evident in the δ 1 8 θ record at 3.2 Ma, but events of 18O-enrichment of increasing magnitude occurred at 3.1, 2.7, 2.6, and 2.4 Ma. The two youngest events are correlated with events indicating glacia-tion at northeast Atlantic DSDP Hole 552A (Shackleton et al., 1984). The oldest δ 1 8 θ spike, centered within the Mam-moth Paleomagnetic Event, is the most prominent feature of results for the interval between 3 and 4 Ma. This isotope event is interpreted as evidence of 2°C bottom-water cooling combined with minor glaciation. Carbon-isotope results for P. wuellerstorfi indicate that Site 606 has been under the influence of North Atlantic Deep Water for most of the interval from 2 to 4 Ma. A significant change in "vital effect " on G. subglobosa at 2.4 Ma is evident in the δ 1 3C record. Specimens dating from that time become smaller and less abundant than older specimens, and have δ 1 3C values lowered by as much as l‰. This effect could introduce a significant artifact into data sets where various species are "corrected " to P. wuellerstorfi.