Abstract
Abstract. Ice sheets extending over parts of the East Siberian continental shelf have been proposed for the last glacial period and during the larger Pleistocene glaciations. The sparse data available over this sector of the Arctic Ocean have left the timing, extent and even existence of these ice sheets largely unresolved. Here we present new geophysical mapping and sediment coring data from the East Siberian shelf and slope collected during the 2014 SWERUS-C3 expedition (SWERUS-C3: Swedish – Russian – US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions). The multibeam bathymetry and chirp sub-bottom profiles reveal a set of glacial landforms that include grounding zone formations along the outer continental shelf, seaward of which lies a > 65 m thick sequence of glacio-genic debris flows. The glacial landforms are interpreted to lie at the seaward end of a glacial trough – the first to be reported on the East Siberian margin, here referred to as the De Long Trough because of its location due north of the De Long Islands. Stratigraphy and dating of sediment cores show that a drape of acoustically laminated sediments covering the glacial deposits is older than ∼ 50 cal kyr BP. This provides direct evidence for extensive glacial activity on the Siberian shelf that predates the Last Glacial Maximum and most likely occurred during the Saalian (Marine Isotope Stage (MIS) 6).
Highlights
The glacial history of the Siberian continental shelf of the East Siberian Sea is poorly known and marine geological and geophysical data from this region are scarce
Most of the area is shallower than 120 m, implying that it was exposed during the sea level low stand of the Last Glacial Maximum (LGM) and the larger glaciations following the mid-Pleistocene transition (Lambeck et al, 2014; Rohling et al, 2014), even considering glacial isostatic adjustments (Klemann et al, 2015) (Fig. 1)
The geophysical data collected from the outer shelf and slope of the East Siberian Sea, north of the De Long Islands, are sparse but contain evidence for many elements commonly associated with a cross-shelf troughs (CSTs)
Summary
The glacial history of the Siberian continental shelf of the East Siberian Sea is poorly known and marine geological and geophysical data from this region are scarce. Most of the area is shallower than 120 m, implying that it was exposed during the sea level low stand of the Last Glacial Maximum (LGM) and the larger glaciations following the mid-Pleistocene transition (Lambeck et al, 2014; Rohling et al, 2014), even considering glacial isostatic adjustments (Klemann et al, 2015) (Fig. 1). One consequence of the shallowness of the East Siberian shelf is that submarine glacial landforms, signifying the presence of an ice sheet (Dowdeswell et al, 2016), may have been eroded during regressive and transgressive cycles. On formerly glaciated margins, areas of fast-streaming glacial ice are recognized by the presence of glacially excavated cross-shelf troughs (CSTs) (Batchelor and Dowdeswell, 2014). O’Regan et al.: De Long Trough: a newly discovered glacial trough on the East Siberian continental margin
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