Abstract

Southeast Alaska bears impressive evidence of widespread glacial erosion, but its glacial history is poorly known. A middle Wisconsin interstadial, during which climate may have been only slightly cooler than the present, ended after 27,000 years B. P. Glaciers overran the Alexander Archipelago during the late Wisconsin, reaching their maximum extent before 14,000 years B.P. and perhaps before 16,000 years B.P. Late Wisconsin ice flowed onto the continental shelf but may have reached the outer shelf only near major fjord mouths. Ice was restricted to the inner shelf and near Neoglacial moraines between Cross Sound and Cape Fairweather because local geography blocked ice flowing from the interior and limited catchment areas near the coast. A widespread marine transgression reaching more than 200 meters above present sea level in the inner fjords of southeast Alaska accompanied deglaciation that occurred shortly before 13,000-14,000 years B.P. A late glacial advance probably occurred after 13,000 and before 9,000 years B.P. in this region. During the Holocene in the Lituya district, glaciers advanced at about 6,000 years B.P. and during at least two later periods of Neoglaciation starting about 3,600 years B.P. and 1,500 years B.P.