Quaternary glacial, lacustrine, and fluvial interactions in the western Noatak basin, Northwest Alaska

The 130 km long Noatak basin is surrounded by mountains of the western Broo ks Range. Middle and late Pleistocene glaciers flowing southeast into the b asin dammed a succession of proglacial lakes defined by shorelines, outlet channels, and upper limits of wave erosion. More than 60 bluffs along the N oatak River and its principal tributaries expose glacial and glaciolacustri ne sediments that exhibit cut-and-fill relationships with interglacial and interstadial river-channel and floodplain deposits. This report focuses on the western Noatak basin, where high bluffs created by deep postglacial ero sion record four major glacial advances. During the Cutler advance, a float ing ice tongue terminated in a large proglacial lake that filled the Noatak basin. The retreating glacier abandoned a trough along the valley center t hat subsequently filled with about 40 m of sediment during several younger glaciations and probably two major interglacial episodes. Alluvium that for med near the beginning of the younger interglaciation contains the 140,000 yr old Old Crow tephra. The subsequent closely spaced Okak and Makpik advan ces are clearly younger than the maximum of the last interglaciation, but t hey preceded a middle Wisconsin (36-30 ka) nonglacial interval in the Noata k basin. The Okak advance terminated in an extensive lake, whereas glaciers of the Makpik and the subsequent Anisak advances flowed into much narrower lakes that filed only the basin center. The Anisak advance, bracketed by r adiocarbon ages of about 35 and 13.6 ka, represents the Last Glacial Maximu m (LGM) in the western Noatak basin. Correlations with the oldest and youngest glacial deposits of the central B rooks Range are clear, but relationships to events of intermediate age are more tenuous. Early Pleistocene and older glacial advances from the central Brooks Range must have filled the Noatak basin and overflowed northward th rough Howard Pass. A younger glacial advance, of inferred middle Pleistocen e (Sagavanirktok River) age, extended down the Noatak valley into the basin center, but its deposits are deeply buried beneath the basin floor and mus t be older than the Cutler moraine. The Cutler advance may have been synchr onous with the older of two advances of Itkillik I age in the Atongarak Cre ek area, but other evidence indicates that the Okak-Makpik moraine successi on more likely was synchronous with the two Atongarak Creek moraines. Radio carbon ages, surface morphology, soil and weathering profiles, and lake-lev el history all support correlation of the last (Anisak) major glacial advan ce in the western basin with the Douglas Creek moraine farther east and wit h Itkillik II (late Wisconsin) glaciation of the central Brooks Range. (C) 2000 Elsevier Science Ltd. All rights reserved.