EMERGENT MARINE RECORD AND PALEOCLIMATE OF THE LAST INTERGLACIATION ALONG THE NORTHWEST ALASKAN COAST

The last interglacial high sea-level stand, the Pelukian transgression of isotope substage 5e, is recorded along the western and northern co asts of Alaska by discontinuous but clearly traceable marine terraces and coastal landforms up to about 10 m altitude. The stratigraphy indi cates that sea level reached this altitude only once during the last i nterglacial cycle. From the type area at Nome, to St. Lawrence Island in the Bering Sea, to the eastern limit of the Beaufort Sea, Pelukian deposits contain extralimital faunas indicating that coastal waters we re warmer than present. Amino acid ratios in molluscs from these depos its decrease to the north toward Barrow, consistent with the modern re gional temperature gradient. Fossil assemblages at Nome and St. Lawren ce Island suggest that the winter sea-ice limit was north of Bering St rait, at least 800 km north of its present position, and the Bering Se a was perennially ice-free. Microfauna in Pelukian sediments recovered from boreholes indicate that Atlantic water may have been present on the shallow Beaufort Shelf, suggesting that the Arctic Ocean was not s tratified and the Arctic sea-ice cover was not perennial for some peri od. In coastal regions of western Alaska, spruce woodlands extended we stward beyond their modern range and in northern Alaska, on the Arctic Coastal Plain, spruce groves may have entered the upper Colville Rive r basin. The Flaxman Member of the Gubik Formation on the Alaskan Arct ic Coastal Plain was deposited during marine isotope substage 5a and r ecords the breakup of an intra-stage 5 ice sheet over northwestern Kee watin. (C) 1995 University of Washington.