Relationship between surface-water temperature and ice-sheet expansion during the middle Miocene

摘要

A three-fold expansion of the Antarctic ice sheet at 13.60, 12.82, and 11.60 Ma has been inferred from δ~(18)O maxima analyzed in planktonic and benthic foraminiferal tests, although accompanying changes in sea surface temperature have not been detailed. We present estimated changes in middle Miocene surface-water temperatures based on analysis of δ~(18)O 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 δ~(18)O 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.