Meteorite impact crater in central alaska.

Study of Landsat imagery prompted Cannon (1) to suggest that Sithylemenkat Lake in central Alaska occupies a meteorite impact crater. In support of his thesis, he cites physiographic, structural, geochemical, and aeromagnetic evidence from various published sources. We believe, on the basis of our previous work in the area (2-4), that Cannon has largely misinterpreted these published data, which, when viewed in the context of the regional geology, provide little or no support for his thesis. We continue to favor a glacial origin for Sithylemenkat Lake, as first suggested by Herreid (5), and believe that Cannon has completely overlooked the evidence for glaciation in the area. In his argument, Cannon rules out a glacial origin for Sithylemenkat Lake because there are "no glacial features of any sort" in the Sithylemenkat Lake area. This is a surprising statement in view of Herreid's report of glacial drift on the east side of Sithylemenkat Lake and earlier reports and maps by Eakin (6), Karlstrom (7), and Coulter et al. (8) of drift and other glacial features in and around the margin of the Kanuti Flats. Part of Cannon's confusion about the glacial history of this area may stem from his apparent misconception that Sithylemenkat Lake is situated in the Ray Mountains, when, in fact, it lies 35 to 50 km north of the Ray Mountains in the Kokrines-Hodzana Highlands at the margin of the Kanuti Flats [see for example, Wahrhaftig (9) and Orth (10)]. In the Ray Mountains, Pleistocene glaciation was confined to small valley glaciers that terminated more than 30 km south of the Sithylemenkat Lake area (11). The Kanuti Flats and adjoining parts of the Kokrines-Hodzana Highlands, on the other hand, were covered by a vast piedmont glacier fed from collection areas far to the north in the Brooks Range. Evidence for this piedmont glacier was cited first by Eakin (6). Later Karlstrom (7) and Coulter et al. (8) identified and mapped remnants of drift around the margin of the Kanuti Flats. Our investigations indicate that drift from this piedmont glacier extends as far south as the Kanuti River-Melozitna River drainage divide, or about 20 km south of the latitude of Sithylemenkat Lake. We found gravels of probable glacial origin in the Kokrines-Hodzana Highlands at an elevation of 700 m, or nearly 500 m above the present level of Sithylemenkat Lake. The surficial geology of the Sithylemenkat Lake area has not been system-