GLACIAL AND ENVIRONMENTAL HISTORY OF SEVERNAYA ZEMLYA, SIBERIAN HIGH ARCTIC, DURING THE LAST >130,000 YEARS

With a position on the north-eastern flank of any Kara Sea-based ice sheet, stratigraphic data from the Severnaya Zemlya islands (ZS) is crucial for any ice-sheet reconstruction. The area was, however, excluded during QUEEN field investigations. In order to resolve this, a new field research programme has been launched, with its first field season on SZ in 2002 at two key locations on October Revolution Island.

Our main effort was put into the stratigraphy along the Ozernaya River. Here we mapped three marine sequences, divided by glacial tills. The lowermost sequence is shallow-marine stratified sand (M-1) with in situ mollusc shells. It is tectonized by a glacier which advanced southwards from inland SZ towards the Kara Sea, depositing the lowermost till (T-1). Clayey-to-sandy marine sediments (M-2) in turn overlie this till, containing numerous in situ fossil mollusc shells, as well as driftwood and whalebones. Clast fabrics from the above-lying till (T-2) and glaciotectonics in the underlying M-2 show that also this glacier advance was southwards into the Kara Sea. The uppermost marine unit (M- 3) is a sandy sublittoral deposit and beach gravels. The beach gravels, in turn, are covered by a thin, cryoturbated diamicton, probably of a glacial origin (T-3).

The data indicate three Late Quaternary major glaciations on October Revolution Island, where local ice caps grew and expanded and probably coalesced with ice from Taymyr and Novaya Zemlya to form a Kara Sea Ice Sheet. The significant isostatic depression, causing subsequent deposition of marine sediments and formation of raised beaches at altitudes up to 100-130 m a.s.l. suggest that the glaciation was regional, not only expansion of local glaciers, and that SZ was an ice-sheet nucleation area. The age of the glaciation events is still uncertain: Our best candidate for Eemian deposits is marine unit 2, with its rich fossil record. If that will be substantiated by our pending age determinations, the stratigraphy records a pre-Eemian marine event (M-1), followed by a major Saalian (>130 ka) glaciation (T-1). There follows an Eemian interglacial marine event (M-2), which is in turn followed by a major glaciation (T-2). Later, following an ice retreat, marine unit 3 and subsequently the capping glacial drift sheet were deposited.