CGRG Bibliography of Canadian Geomorphology
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Author : Downes, H.
Date : 1985
Title : Evidence for magma heterogeneity in the White River Ash (Yukon Territory).
Publication : Canadian Journal of Earth Sciences
Issue : 22(6):
Page(s) : 929-934.
Abstract
Two Recent Plinian eruptions in the Wrangell Mountains (southeast Alaska) gave rise to two distinct ash-fall deposits that are collectively known as the White River Ash and cover as much of the Yukon Territory, northwest Canada. Analysis of the pumiceous glass indicates that the magma chamber was compositionally inhomogenous prior to each eruption. No compositional stratigraphy has been detected in the deposits, indicating either thorough mixing in the eruption cloud or thorough reworking after deposition. Thus each individual sample of ash represents a large part of the magma chamber, whereas large pumice fragments are more homogenous. Variation in temperature, 950-990 and 995-1030 degrees C, respectively, for the older and younger eruptions, and -log fo2 values, 9.3-8.3 and 8.3-7.7, derived from the Fe-Ti oxides, support the conclusion that the magma chamber was inhomogeneous.
Bibliography of Canadian Geomorphology