Stable-isotope stratigraphy of the Pliocene-Pleistocene climate transition in the northwestern subtropical Pacific

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• 作者：Nicholas L. Venti ; ^{nventi@udel.edu} ; Katharina Billups
• 关键词：Stable isotope ; Pliocene&ndash ; Pleistocene ; North Pacific ; Northern Hemisphere glaciation
• 刊名：Palaeogeography ; Palaeoclimatology ; Palaeoecology
• 出版年：2012
• 期刊代码：68_00310182
• 类别：ear
• 出版时间：1 April, 2012
• 卷：326-328
• 期：Complete
• 页码：54-65
• 文件大小：1674 K

摘要

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 未¹⁸O and 未¹³C time series to span the Pliocene-Pleistocene climate transition. Excellent agreement between the Site 1208 未¹⁸O record and the global 未¹⁸O 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 未¹⁸O and 未¹³C 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, 未¹⁸O cycles consistently lead 未¹³C cycles by ~ 3 kyr. This suggests that global-ocean 未¹³C 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 未¹⁸O 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.