USGS Open-FIle Report 94-588: Prentice

Review of the deep-sea oxygen isotope record regarding early Pliocene Antarctic deglaciation

Michael Prentice: University of New Hampshire

I will review the early Pliocene deep-sea oxygen isotope record as it pertains to Antarctic (polar) deglaciation. The tropical shallow-dwelling planktonic foraminiferal d18O and deep-water benthic d18O records will be emphasized. A significant recent refinement in the tropical planktonic d18O record is the divergence of western tropical Pacific planktonic d18O (ODP 806, 807) and comparable d18O records from the eastern tropical Pacific (DSDP 572) and tropical Atlantic (DSDP 502, ODP 625). Recent high- resolution benthic d18O records (ODP 704 and 846) confirm the significant benthic d18O depletion patterns previously noted for the early Pliocene.

Three of the more prominent interpretations of the early Pliocene d18O record will be evaluated. The extreme deglaciation hypothesis encounters the greatest obstacles especially as regards physical explanation of deglaciation and lower-than-present tropical SST. The stabilist view invoking minimal Antarctic warming and deglaciation encounters fewer obstacles including counter-intuitive behavior of the Antarctic climate and ice-sheet system. The snow-gun hypothesis has been refined and requires smaller Antarctic glaciations than previously. The refinements reflect improved interpretation of the late Pleistocene western tropical Pacific planktonic d18O record. The chief obstacle for the snow-gun hypothesis is explaining deepwater significantly warmer than present. Independent data from terrestrial and shallow-marine polar sequences are required to constrain interpretation of the deep-sea oxygen isotopic record.

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