PLEISTOCENE GLACIAL-LAKE DEPOSITS OF THE SANPOIL RIVER VALLEY, NORTHEASTERN WASHINGTON.

Late Wisconsin (last-glacial) lacustrine deposits near Manila Creek, in Washington's Sanpoil River valley, alternate rhythmically between sets of varves (varved intervals) and at least 89 graded beds each attributable to a flood from glacial Lake Missoula, Montana (flood beds). Detrital wood in a varved interval in the middle of the section yields a **1**4C age of 14,490 plus or minus 290 yr B. P. Therefore, it is likely that Lake Columbia's Grand Coulee outlet approached its present depth before the last glaciation.