NOAA/WDS Paleoclimatology - Northwest Pacific ODP1208 Plio-Pleistocene Stable Isotope Data

STUDY NOTES: Foraminiferal stable isotope (d18O and d13C) were measured via mass spectrometry at orbital-scale resolution (10-cm spacing, or ~2.5 kyr timestep) for the Pliocene-Pleistocene (1.760-3.700 Ma) section in tests of the epifaunal benthic foraminifer Planulina wuellerstorfi. Sample averages only are presented here. The age model is derived by tuning the d18O record to the global stack of Lisiecki and Raymo (2005).
ABSTRACT SUPPLIED BY ORIGINATOR: From Ocean Drilling Program (ODP) Site 1208 on Shatsky Rise below the Kuroshio Current Extension, we present the North Pacific's first orbital-scale benthic foraminiferal d18O and d13C time series to span the Pliocene-Pleistocene climate transition. Excellent agreement between the Site 1208 d18O record and the global d18O stack of Lisiecki and Raymo (2005) provides orbital-scale age control and confirms continuous stratigraphy from 3.7 to 1.8 Ma at the single-hole site. Cross-spectral analysis of the d18O and d13C time series reveals that these are coherent to 80% confidence at the 41-kyr obliquity band prior to 3.3 Ma (glacial isotope stage M2) and increase to the 95% level thereafter. Throughout, d18O cycles consistently lead d13 C cycles by ~ 3 kyr. This suggests that global-ocean d13C variations, as produced by terrestrial-marine 12C transfers, were responsive to obliquity-induced climate changes before the Northern Hemisphere glaciations (NHG) reached mid latitudes at 2.7 Ma. In contrast, 41-kyr carbonate sedimentation (as derived from sediment reflectance) cycles, maxima tightly coupled to (>95% confidence) and in phase with minima in the d18O record, do not emerge until 2.7 Ma. Foraminiferal fragmentation counts indicate that carbonate preservation is not the primary process behind enhanced carbonate deposition during interglacials. Thus, we surmise that hydrography-related changes in biogenic opal and carbonate production in surface water best explain glacial-interglacial carbonate cycles beginning with significant NHG. Firm establishment of orbital-scale age control on the stratigraphically complete Site 1208 section now provides a platform for high-resolution paleoceanographic reconstruction of the relatively understudied North Pacific.