Late Pleistocene glaciation of the southwestern Ahklun Mountains, Alaska

Glacial deposits in the southwestern Ahklun Mountains, southwestern Alaska, record two major glacier advances during the late Pleistocene. The Arolik Lake and Klak Creek glaciations took place during the early and late Wiscon sin, respectively. During the Arolik Lake glaciation, outlet glaciers emana ted from an ice cap centered over the central portion of the Ahklun Mountai ns and expanded beyond the present coast. During the Klak Creek glaciation, ice-cap outlet glaciers terminated similar to 60 km upvalley from Arolik L ake moraines, The area also supported numerous alpine glaciers that expande d from small massifs. During both episodes of glaciation, these alpine glac iers apparently reached their maximum positions sometime after the retreat of the ice-cap outlet glaciers. Equilibrium-line altitudes for reconstructe d alpine glaciers of the Klak Creek glaciation average similar to 390 +/- 1 00 m elevation in the western Ahklun Mountains, which is at most 500 m, and possibly only 200 m, below the estimated modern equilibrium-line altitude. The maximum late Pleistocene advance in the southwestern Ahklun Mountains occurred during the early Wisconsin, similar to advances elsewhere in weste rn Alaska, but in contrast to the isotopic signal in the deep-sea record of global ice volume, The restricted extent of Klak Creek glaciers might refl ect the increased distance to the Bering Sea resulting from eustatic sea-le vel regression and decreased evaporation resulting from lower sea-surface t emperatures and increased sea-ice extent. (C) 2000 University of Washington .