Abstract
A continuous composite oxygen isotope (δ18O) stratigraphy from benthic foraminifera in the Bering Sea was reconstructed in order to provide insight into understanding sea-ice evolution in response to Northern Hemisphere Glaciation. Oxygen isotope records from multiple species of benthic foraminifera at Integrated Ocean Drilling Program (IODP) Expedition 323 Site U1343 (54°33.4′N, 176°49.0′E, water depth 1950m) yield a highly refined orbital-scale age model spanning the last 1.2Ma, and a refined age model between 1.2 and 2.4Ma. An inter-species calibration was used to define species offsets and to successfully obtain a continuous composite benthic δ18O record, correlated with the global composite benthic δ18O stack curve LR04 to construct an orbital-scale age model. The consistency of the benthic δ18O stratigraphy with biostratigraphy and magnetostratigraphy confirms the reliability of both methods for constraining age. The time difference between cyclic changes in sedimentary physical properties and glacial–interglacial cycles since 0.8Ma is notable, and suggests that physical properties alone cannot be used to construct an orbital-scale age model. Amplitude changes in physical properties and a significant drop in the linear sedimentation rate during glacials after 0.9Ma indicate that the glacial sea-ice edge extended beyond the Bering Sea Slope (Site U1343) at this time.
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