Recent field evidence from the northern Koryak Mountains, Chukotka, Far Eastern Russia confirms the hypothesis that the extent of ice in western Beringia was limited during the last glacial maximum (LGM). Numerical and relative age dating techniques are used to support this hypothesis and reconcile the differences between the late glacial history of western and eastern Beringia. Previous work on the glacial geology of the Koryak Mountains/Lake Mainitz region is contained in unpublished Russian reports; however, these reports are mainly based on mapping by air photo interpretation. In the summer of 1996, the glacial geology of the Nygchekveem and Nahodka River valleys was investigated, as well as the adjacent Lake Mainitz and Lake Rocamaha areas. Terminal, lateral and medial moraines as well as meltwater channels, dead ice topography, kettles and outwash plains mark the extent of ice. Common to all valleys is the presence of a 13.8 m arl glaciofluvial terrace, most likely recording deglaciation of the area during the LGM. Field evidence suggests that the glaciers of the northern Koryak Mountain reached no more than 20 km beyond their present limits during the LGM. Erratics on moraines and terraces were sampled for cosmogenic isotope analysis and will provide a reliable estimate on a minimum age of deglaciation. Degree of soil development on the crest and mid slope of moraines is being used as an indicator of relative age. Amino acid ratios (AIle/Ile) of 0.017 (n = 16) on Astarte from marine sediment along the shoreline to the northeast of the Koryak Mountains, support the hypothesis that alpine glaciers did not reach the Anadyr River or the Gulf of Anadyr coastline. However, glaciers emanating from the southern and eastern Koryak Mountains may have extended toward the Bering Sea at lower elevations. Elevations of present cirque floors are 380-400 m, and it is not unlikely that during the last glacial maximum ELAs were depressed nearly to sea level. This research serves to test the dependence of the Bering Sea moisture source availability on the extent of north and south facing glaciers in the Koryak Mountians.
