| Summary: | Glacigenic bedforms such as multiple glacial lineations and moraines on the Chukchi and East Siberian margins reveal recurrent waxing and waning by voluminous ice masses. Despite their paleoclimatic significance, the timing, geographic distribution, and mechanisms of these glaciations remain inadequately understood. To enhance our understanding of the Quaternary Arctic glacial history, we study high-resolution swath bathymetry and subbottom profiling data with lithostratigraphy and provenance of four sediment cores. These data characterize deposits of the last two glaciations at the Chukchi margin and adjacent basins. In all cores, multiple peaks of plagioclase are prominent in both glacial intervals, probably reflecting predominant glacigenic input from the East Siberian Ice Sheet (ESIS). Peaks of dolomite and quartz for tracing the Laurentide Ice Sheet sources occur around the last glacial/deglacial interval and in sediment preceding the penultimate glaciation. By integrating seismostratigraphy with sediment cores, we constrain the formation of mid-slope moraines on the western side of the Chukchi Rise to the penultimate glaciation (estimated age range MIS 4 to 6). Considering the coeval glacial erosion off the East Siberian margin, our results confirm that the ESIS at that time extended to water depths of ~650/950 m on the Chukchi Rise/East Siberian margin. In comparison, the last ESIS (MIS 2 to possibly 4) was smaller, with the identified seafloor imprint limited to water depths of ~450 m on the Chukchi Borderland, while its extent on the East Siberian margin remains to be determined.
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