Morphological analyses of glacial valleys and estimates of sediment thickness on the valley floor: Victoria Valley system, Antarctica

Abstract

The morphology of glacial valleys in the Victoria Valley system, Antarctica, was quantitatively analyzed employing the model Z=aX^b. In this model, the X and Z coordinate values are the distances from and the heights above the valley center as determined by photogrammetric techniques from 1 : 60000 high-altitude aerial photography obtained in 1970. The coefficients "a" and exponents "b" were determined by the method of least squares. Values for the exponents ranged from approximately 0.6 to 5,indicating that the glacial valley cross-sections could be approximated by profiles varying from shallow V's to quintic parabolas. These values differ from those obtained for glacial valleys in Europe and North America, where parabolas with exponents from 1.5 to 2.0 have been found to approximate valley cross-sections. Consequently, it appears that there are distinctive morphological differences among groups of glacial valleys. Two possible explanations for these morphological differences are presented : 1) different modes of glacial erosion; and 2) slopes at different stages of evolution by salt weathering. In addition to morphological factors, estimates of the depth of sediments in the valleys were also attempted by extrapolating the modelgenerated curve beneath the surface deposits to the valley floors. The difference between the photogrammetrically measured surface elevations and the estimated bedrock elevations yielded the depth estimates. Examination of the results indicates that these estimates are reasonably correct when appropriate segments of the valley wall are chosen for the curve fitting.