STABLE ORGANIC-CARBON ISOTOPES IN SEDIMENTS OF THE NORTH BERING SOUTHCHUKCHI SEAS, ALASKAN SOVIET ARCTIC SHELF

The deltaC-13 and OC/N in carbonate-free sediments show an east to wes t cross-shelf trend within the north Bering-south Chukchi seas. Genera lly, the deltaC-13 increases from the river deltas (< -25 parts per th ousand) in the east through the sound areas (-23 to -22 parts per thou sand) to open shelf in the west (-21 to -20 parts per thousand). The s ediment OC/N ratios also show an east-west cross-shelf trend with a pr ogressive westward decrease from river deltas (>10) through the adjace nt sound (8-10) to the open shelf (<7). Sediment trap samples from sou theast Chukchi Sea show complementary cross shelf changes in deltaC-13 and OC/N. These distributional patterns are similar to those generall y observed in temperate shelves despite the peculiar environmental set tings of the subarctic-arctic. The patterns of lateral changes in delt aC-13 and OC/N in our study area are explained in the context of two-e nd member sources of organic carbon, terrigenous and marine. No signif icant correlations exist between sediment deltaC-13 and OC/N and benth ic biomass in the south Chukchi Sea. These suggest that the nature of organic carbon, as indicated by the deltaC-13 and OC/N, is not the sol e factor controlling benthic biomass in the above area. It is further suggested that the observed lateral changes in deltaC-13 have a potent ial use as a proxy signal in the elucidation of the Quaternary transgr essive-regressive history of Beringia.