Late Wisconsin Glacier Surface Elevations and Flow Directions from the Beartooth Plateau to the Clarks Fork Valley, Wyoming

Abstract

During the Pinedale glaciation of the Late Wisconsin, an ice cap covered most of the land comprising the Beartooth Plateau and the highlands to the south, stretching to the Clarks Fork Valley in northwestern Wyoming. The upper limits or this icemass and flow directions during full glacial conditions were determined from field observation of nunataks, highest glaciated uplands, glacial striations, and streamlined bedrock forms. On the southern portion of the Beartooth Plateau, ice possibly reached as far as 11,100 ft (3,383 m), with its surface elevation gradually falling to 8,800 ft (2,682 m) upon reaching the Clark's Fork outlet glacier. Ice flow from the Beartooth Plateau followed a radial pattern heading southwest in the western portion of the field area, south in the central portion, and southeast in the eastern portion. Some glacial striations indicated valley glacier flow constrained by topography in contrast to ice cap flow during full-glacial conditions. Basal shear stress calculations support the constructed model, demonstrating it as physically possible. Averaging 0. 7 bars, the values for most of the icemass fell within basal shear stress limits of modem glaciers.