Glaciation of Chagvan Bay Area, Southwestern Alaska

  • Stephen C. Porter
Keywords: Glaciation


Morphologic and stratigraphic evidence in this area indicates that a four-fold succession of glaciers originating in the Ahklun Mountains, spread over the coastal lowlands as broad piedmont lobes. The Kemuk and Clara Creek glaciations are considered Pre-Wisconsin, the Chagvan and Unaluk glaciations Wisconsin in age. Radiocarbon dates for the Unavuk and Chagvan drifts are 8910 ± 110 yr and >45,000 yr respectively. A broad bedrock channel buried beneath unconsolidated preglacial and glacial sediments was cut when relative sea level was 200 ft below its present level. Relationships of sedimentary fills to this and to a younger buried channel point to late Tertiary submergence of the Bering Shelf followed by eustatic changes related to fluctuations of Pleistocene glaciers.