Abstract

Six glacial episodes have been identified in the Yukon-Tanana Upland of east-central Alaska. From oldest to youngest they are termed the Charley River, Mount Harper, Eagle, Salcha, and Ramshorn glacial episodes. An older drift, which underlies till of Charley River age, has a clayey matrix in contrast to the sandy matrix of all other glacial deposits of the area; it may be of Tertiary age.

The Charley River glacial episode, of which only traces remain, covered more than 20 percent of the upland and may be of early Pleistocene age. The succeeding Mount Harper glacial episode left many deposits, now highly weathered, and may be of middle Pleistocene age. The Eagle and Salcha glacial episodes may be of early and late Wisconsin age, respectively. Their deposits are the most readily seen in the upland. Two minor events, the Ramshorn I and D phases, are represented by fresh-appearing moraines in the highest cirques.

The oldest drift is described from a locality on the Goodpaster River; the type areas of the remaining episodes are established on Ramshorn creek and on an adjoining segment of the Charley River.