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Chemical weathering in South Cascade Glacier Basin, Comparison of subglacial and extra-glacial weathering


Ellen V. Axtmann and Robert F. Stallard

U.S. Geological Survey, 3215 Marine Street, Boulder, CO 80303-1066, USA


Abstract

The cationic denudation for South Cascade Lake drainage basin was calculated to be 676 mEq m2/y, somewhat less than previous estimates. The denudation rate was estimated for both the subglacial and extra-glacial waters that comprise the total basin runoff. Subglacial waters have a significantly higher yield than extra-glacial waters (between approximately 800 and 2380 mEq m2/y for subglacial waters, and 580 mEq m2/y for extra-glacial waters). All yields for the basin are higher than the reported world average of 190 mEq m2/y for chemical erosion (Meybeck, 1979). Although total cation yields are similar for South Cascade Glacier Basin and a tropical watershed with similar area, runoff, and geology, the proportions of dissolved constituents are markedly different. Subglacial waters have unusually high K/Na and Ca/Na ratios, and very low dissolved Si. This appears to be typical of waters draining warm-based glaciers.


Axtmann, E.V. and Stallard, R.F., 1995. Chemical weathering in South Cascade Glacier Basin, Comparison of subglacial and extra-glacial weathering. In: Biogeochemistry of Seasonally Snow-Covered Catchments (ed. by K. Tonnessenn, M.W. Williams, and M. Tranter) (Proc. Boulder Symp., July 1995). IAHS Publ. no 228, p. 431-439.

 
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