Abstract

The rugged Aleutian Range along the Pacific side of the Alaska Peninsula has numerous mountains rising 1,800-2,500 meters above sea level. These served as barriers to moisture-laden air from the Pacific Ocean and were centers of ice cap formation during Quaternary time. Ice caps also formed on the continental shelf in the Shumagin Islands area and possibly in Cook Inlet, at least during the Wisconsin glaciation. The snowline throughout the Quaternary, as at present, rose steeply westward across the peninsula toward Bristol Bay.

Pre-Wisconsin drift is preserved locally along the Bristol Bay coast, but most glacial deposits on the peninsula date from Wisconsin time. Two glacial advances of late Wisconsin age covered most of the Alaska Peninsula. Morainal ridges are fresh and little altered by mass wasting. Lakes Iliamna, Naknek, Becharof, and Ugashik are present-day remnants of larger glacial lakes that were dammed by moraines of these advances. A warming trend started about 10,000 years B.P. Maximum deglaciation, probably occurring before 8,000-8,500 years B.P., is marked by high terraces along the glacial lakes. Glacial readvances during the Holocene were by small alpine valley glaciers that generally did not reach the mountain front. Early man established campsites on the shore of Ugashik Lakes by about 9,000 years B.P.