Neogene trends in planktonic foraminifer δ18O from Site 807: implications for global ice volume and western equatorial Pacific sea-surface temperatures

Abstract

A preliminary record for shallow-dwelling planktonic foraminifer δ18O at Site 807 was produced for the late Pleistocene, early Pliocene, and early Miocene. Site 807 δ18O values between 4 and 5 Ma average 0.75‰ more than Holocene values and show an average variation of 0.5‰. For the early Pliocene, peak maximum δ18O at Site 807 attain values equivalent with the last glacial maximum whereas peak minimum δ18O were never less than Holocene δ18O. Shallow-dwelling planktonic δ18O at Site 807 between 16 and 24 Ma average more than 1.0‰ more positive than Holocene δ18O and exhibit 0.5‰ average amplitude. Assuming that the global ice budget for the early Pliocene and early Miocene was restricted to Antarctica, it is difficult to attribute the very positive Site 807 δ18O for these intervals to ice on Antarctica. Site 807 δ18O for these intervals more likely reflect sea-surface temperatures cooler than at present, sea-surface salinity greater than at present, increased dissolution, or some combination of these changes. -Authors