Planktonic foraminiferal abundances and stable isotope ratios in middle Miocene sediments of the North Atlantic and the southwestern Pacific

We present estimated changes in middle Miocene surface-water temperatures based on analysis of delta18O in planktonic foraminifera collected at mid-latitude Deep Sea Drilling Project sites in the North Atlantic and South Pacific oceans.

We also identify periods of ice-sheet growth based on comparisons of benthic and planktonic foraminiferal delta18O values. Our results indicate: (1) a distinct cooling of the sea surface from 13.6 to 13.5 Ma immediately following a peak in ice volume at 13.6 Ma, (2) a cooling of the sea surface during a period of increasing ice volume from 13.2 to 13.0 Ma, and (3) a development of the Antarctic ice sheet during a period of cooling of the sea surface centered at 11.6 Ma.