MAJOR DEGLACIATION OF EAST ANTARCTICA DURING THE EARLY-LATE PLIOCENE - NOT LIKELY FROM A MARINE PERSPECTIVE

We have conducted an integrated study of ice-rafted debris (IRD) and o xygen isotopes (measured on Cibicides, Globigerina balloides, and Neog loboquadrina pachyderma, using identical samples). We used samples fro m the early Late Pliocene Gauss Chron from ODP Site 114-704 on the Met eor Rise in the subantarctic South Atlantic. During the early Gauss Ch ron, the oxygen isotopic ratios are generally up to 0.5 parts per thou sand-0.6 parts per thousand less than their respective Holocene values . The lowest values in this record can accommodate a warming of about 2.5 degrees C OR a sea-level rise of about 50 m, but not both, and pro bably result from some warming and a small reduction in global ice vol ume. Starting with isotope stage MG2 [3.23 Ma on the Berggren et al. ( 1985) time scale; 3.38 on the Shackleton et al. (1995b) time scale] ox ygen-isotopic values generally increase (and oscillate about a Holocen e mean). The first significant IRD appears at the same time. There is a subsequent increase in IRD amounts upsection. In order to reach the site, this material must have been transported by large, tabular icebe rgs derived from Antarctic ice shelves or ice tongues, similar to occa sional, large modem icebergs. This combined record suggests strongly t hat the Antarctic ice sheet was essentially intact; some warming at th e drill site is indicated, but not a major reduction in ice-volume on Antarctica.