Abstract

Glacial drift in four mountain ranges and on the southern coastal plain of the Seward Peninsula records eight glacial episodes ranging in age from late Pliocene to Holocene. Of these episodes, three (the Nome River glaciation and the Sinuk and Skull Creek glacial intervals) antedate an 800,000-year-old basaltic lava flow that overran deeply oxidized and highly eroded drift of Nome River age. Relative-age criteria suggest that far more time separated the Nome River glaciation and the younger glacial advances than is represented by any other nonglacial interval. The enormous extent of older drift also seems to indicate a greatly lowered snowline during the Nome River and older ice advances. Occurring far inside the limit of Nome River deposits is drift of the newly recognized Stewart River glacial interval, the outermost of a closely spaced, three-drift sequence. Stewart River drift deposits are distinguished on the basis of relative-age criteria including moraine morphology, boulder characteristics, and soil development. We correlate the Stewart River glacial interval with the Sagavanirktok River glaciation of the Brooks Range which predates the last interglaciation. Glaciers of the succeeding two glaciations (Salmon Lake and Mount Osborn) were largely restricted to mountain valleys, but in a few places they spread out beyond the front of the Kigluaik Mountains where they left moraines that have retained their morphological freshness. The Salmon Lake glaciation is older than the time range of conventional radiocarbon dating; the Mount Osborn glaciation is believed to be of late Wisconsin age. These two advances are correlated, respectively, with the Itkillik I and II glacial phases of the Brooks Range, which are thought to span Wisconsin time. Two still-younger advances are poorly documented. They include a minor advance which left distinctive, well-preserved moraines just beyond the highest cirque headwalls, as well as limited deposits flanking the few surviving glaciers of the Kigluaik Mountains.