Improved stratigraphic framework for the Quaternary western Arctic Ocean and its paleoenvironmental implications

Constrains on the temporal occurrence and spatial extend of Amerasian ice sheets are prerequisite for understanding the boundary conditions necessary for the ice sheet build up in the western Arctic. Although an especially extensive western Arctic marine ice sheet complex has been proposed for Marine isotope stage (MIS) 6, stratigraphic constrains from the Chukchi Borderland are rare, and even missing from the East Siberian continental margin, as most glaciogenic features have not been reliably dated by sediment core data and stratigraphic correlation yet. Thus the timing of (repeated) glaciations and/or ice advances in the Beringian region is still a matter of debate. Readily visible (dark) brown layers are a widespread feature in Late Quaternary sediments of the Central Arctic Ocean, and have been considered potentially useful stratigraphic marker beds for core correlation. Their formation, however, is still a matter of debate but it has been recently suggested that warmer interglacial/interstadial conditions with a more active hydrological cycle led to formation of these Mn-rich dark brown layers. Here we present new data from a suite of high-quality sediment cores that are aligned in two transects across the Chukchi Plateau (East – West) and Mendeleev Ridge (South – North), respectively. Using continuous high-resolution XRF scanning, colour reflectance, and physical properties data allows characterizing the dark brown layers in more detail and to improve their application for stratigraphic correlations. The proposed a supra-regional stratigraphic correlation scheme is integrating both the western Arctic basins and ridges, and will ultimately help to establish a reliable chronology for glacial activities in the Amerasian basin