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A glacier peak and Mount Saint Helens J volcanic ash couplet and the timing of deglaciation in the Colville Valley area, Washington

January 1, 1992

A Late Pleistocene volcanic ash couplet consisting of a glacier Peak ash layer and an underlying Mount Saint Helens J ash layer has been identified at three sites in the Colville Valley area of northeastern Washington. This ash couplet has been reported as far east as northwestern Montana and therefore appears to have widespread distribution south of the International Boundary. Because areas covered by the Cordilleran Ice Sheet, as well as by local mountain glaciers and icefields, were undergoing extensive deglaciation when these ash layers were deposited, about 11 200 BP, the ash couplet is an important time-stratigraphic marker, and its identification at a site provides information about the extent of deglaciation at that time. The presence of the Glacier Peak and Mount Saint Helens J ash couplet in the Colville Valley, about 50km north (upglacier) from the Late Wisconsin terminal moraine near the town of Springdale, indicates that the active margin of the Colville sublobe of the Cordilleran Ice Sheet had retreated at least that distance by 11 200 BP. -from Authors

Citation Information

Publication Year 1992
Title A glacier peak and Mount Saint Helens J volcanic ash couplet and the timing of deglaciation in the Colville Valley area, Washington
DOI
Authors P. E. Carrara, D.A. Trimble
Publication Type Article
Publication Subtype Journal Article
Series Title Canadian Journal of Earth Sciences
Series Number
Index ID 70016832
Record Source USGS Publications Warehouse
USGS Organization