Calculation of the number of planktonic foraminifers per gram (dry weight) of sediment reveals dramatic changes in abundance within Eocene to Miocene sediments at Site 904. The largest scale changes (264 samples analyzed) parallel regional trends in paleoclimate and terrigenous sediment input. Abundance changes of shorter duration, some equivalent in scale to long term fluctuations, reflect the complex interaction of global sea-level change, diagenesis, paleoproductivity, and sediment accumulation rate. Data presented here are intended to support subsequent studies that may unravel some of this complexity. My purpose is to help identify the dominant processes associated with abundance changes of the planktonic foraminifers.

Date of initial receipt: 28 February 1995
Date of acceptance: 26 July 1995

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