USGS Open-File Report 94-588
Middle-Pliocene planktonic foraminifer assemblage from ODP site 704: Paleoceanographic implications
- Harry J. Dowsett
- U.S. Geological Survey, Reston, VA
Abundant and well-preserved assemblages of planktonic foraminifers have
been recovered from middle Pliocene (3.15 - 2.85 Ma) sediments at Ocean
Drilling Program Hole 704A. Cyclic changes in the composition of
foraminifer faunas indicate high frequency variability in oceanographic
conditions. Temperature estimates based upon quantitative analysis of the
planktonic faunas have a range of ~12.5°C with average glacial
(interglacial) winter temperatures of 3.2° C (9.5° C) and summer
temperatures of 6.4° C (13.5° C). Comparison of the SST time series to
the published d18O record from Globigerina bulloides indicates d18O is
primarily a temperature record prior to 2.85 Ma, dampened by fluctuations
in Antarctic ice volume. Increases in ice volume are linked to increases
in SST through net transport of moisture toward the pole. After 2.85 Ma,
an opposite relationship exists between SST and d18O so that increases in
temperature are correlated with d18O enrichment.
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