233-2 Temperature and Continental Weathering Across the Mid-Pleistocene Transition From the North Atlantic Ocean

Abstract:

The Mid-Pleistocene Transition (MPT; ~1.2-0.7 Ma) marks the fundamental reorganization of Earth's climate system from predominantly ~41-ka to ~100-ka glacial-interglacial cycles. Although changes in ice-sheet dynamics and ocean circulation have been widely invoked to explain this transition, the roles of ocean temperature change and continental weathering remain incompletely constrained. Here, we investigate these processes using oxygen, carbon, clumped (δ¹⁸O, δ¹³C, Δ₄₇), and osmium (¹⁸⁷Os/¹⁸⁸Os) isotope records from IODP Expedition 397 Site U1587 (Iberian Margin, eastern North Atlantic), spanning Marine Isotope Stage (MIS) 36-16 (1.2-0.62 Ma).

Paired Δ₄₇ and benthic foraminiferal δ¹⁸O measurements reconstruct bottom-water temperature and seawater δ¹⁸O, allowing the separation of temperature and global ice-volume effects. Benthic δ¹³C records constrain deep-water ventilation, water-mass structure, and carbon storage. Seawater ¹⁸⁷Os/¹⁸⁸Os records track changes in the balance between radiogenic continental weathering and  unradiogenic mantle-derived sources.

Integration of these records will resolve the timing and phasing of ocean temperature, ice-volume, carbon-cycle, and weathering changes across this transition. This multiproxy framework will test whether continental weathering primarily responded to MPT climate reorganization or participated in feedback that facilitated the emergence of longer, higher-amplitude ~100-kyr glacial cycles.

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