AGE OF LAST GLACIAL MEGAFLOODS IN MOSES COULEE AND GRAND COULEE (Invited Presentation)

It is unclear how and when Missoula Floods entered Moses Coulee, one of the great canyons of the Channeled Scabland.

Here we present new geochronology that helps to tie Moses Coulee into the regional flood history.

Four ice-rafted boulders in Moses Coulee have exposure ages that are older than flood-transported boulders below Grand Coulee. These ages are consistent with a flood-routing history in which Moses Coulee flooded before Grand Coulee during the last glaciation, a sequence previously inferred from megaflood deposits at the mouth of Moses Coulee.