Sedimentary archives along the Ross Sea margin provide key insights into the interactions among Antarctic ice dynamics, bottom water formation, and depositional processes near the marine-based ice sheet. Here, we integrate sedimentological, geochemical, and magnetic records from a continental rise sediment core to reveal the late Pleistocene redox evolution and develop a refined age framework. A distinct redox transition is identified across the mid- to late Brunhes period, from reducing conditions—indicated by debilitated paleomagnetic signals, magnetite dissolution, and manganese depletion—to a more oxic interval enriched in maghemite and manganese-bearing phases. Sedimentary features straddling this boundary capture a shift from an ice-proximal deposition with reworked shelf materials to an ice-distal regime characterized by enhanced marine organic matter degradation and improved bottom water oxygenation. Combined relative paleointensity and lithostratigraphic alignments provide feasible chronological constraints for the last 400 kyr, although the iron reducing interval warrants careful consideration. The resulting chronology places the major stratigraphic and redox reorganization at ~250 ka, coincident with the extensive Ross Sea ice retreat. These multi-proxy observations demonstrate that reductive magnetite loss during ice sheet expansions can substantially modify magnetic records near the Antarctic ice margin. Nevertheless, integrated sedimentary magnetic proxies remain effective tools for both developing age models and for reconstructing past redox and cryosphere–ocean variability. • Redox diagenesis modulated sedimentary magnetic records in the Ross Sea margin. • Magnetite and Mn loss with shelf input indicate ice-proximal suboxic conditions. • Enhanced bottom waters during mid-Brunhes ice retreat oxygenated the sediments. • RPI tuning integrated with lithostratigraphy constrains the redox shift at ~250 ka.
Shin et al. (Sat,) studied this question.