High-resolution late Quaternary Indo-Pacific Warm Pool benthic δ18O stratigraphy for evaluating the precession timing of the marine Asian monsoons

Abstract

The timing of Quaternary precession-scale (23 kyr) monsoon variations across the Asia-Australia and the Indo-Pacific regions remains highly debated. The Asian monsoon phase differences of approximately 5 ka reported between a suite of marine sedimentary and speleothem proxy records remain unreconciled despite careful examination of chronological uncertainties, proxy sensitivities, and interpretations. To address these unresolved issues, this study evaluates marine monsoon phase relationships by establishing a new ∼∼800-ka benthic foraminiferal oxygen-isotope (δ 18 O) stratigraphy from core MD012380 from the central Indo-Pacific Warm Pool (IPWP) and quantifying chronological uncertainties within the 0–400 ka interval. In examining the new benthic isotope stratigraphy, we identified approximately 2.1 kyr of age-model uncertainty within the precession band in the 0-400 kyr interval, arising from hand-picked age control points and tuning to marine isotope stacks. Additionally, uncertainty stems from persistent phase offsets between benthic and planktic δ 18 O stacks, cautioning against the assumption of internal consistency when constructing marine isotope chronologies. In summary, our results demonstrate that precession-band phases of the marine Asian monsoon are robustly constrained, yet display significant discrepancies relative to speleothem monsoon records.