The Wiseman quadrangle contains a rich stratigraphic record of alluvial, glacial, and periglacial events of the late Quaternary in the south-central Brooks Range. The numerous bluffs along the Koyukuk River and its tributaries expose drift sheets of the late Pleistocene Itkillik I glacial phase (table 1), and outwash and other proglacial deposits of the succeeding Itkillik II phase. During Itkillik I time, glaciers flowed south through virtually all of the valleys of the south-central Brooks Range to terminate in piedmont lobes within the Koyukuk lowland (Hamilton, 1978, 1979a). Outwash covered the Koyukuk Valley floor beyond the ice limits. Glaciers of Itkillik II age were more restricted; the largest reached positions near the south margin of the range, but many mountain valleys of the Wiseman quadrangle remained unglaciated. Lower alluvial terraces of Holocene age record alternating episodes of aggradation and soil development. Some of these events were controlled locally by mass movements and perhaps by faulting, but others may be related to regional climatic reversals and to fluctuations of cirque glaciers at valley heads.
