| The rhythmic Touchet Beds in the Walla Walla and lower Yakima valleys resulted from many separate backfloodings by hydraulically ponded glacial Lake Missoula water. At least once this episodic lake briefly contained half the 2,130 cubic kilometers of water that catastrophically drained the largest glacial Lakes Missoula. Evidence that the Touchet Beds rhythmites originated from brief backfloodings includes upvalley thinning and fining of locally derived bedload, upvalley paleocurrents, and upvalley transport of erratics derived from Cordilleran ice. -- Waitt, 1980 |
