Neogene sandstone and conglomerate cropping out along the eastern end of Beaver Bay at Cape Aliaksin have been assigned to the Unga Conglomerate Member of the Bear Lake Formation. New data suggest that this correlation may be incorrect.

The rocks at Cape Aliaksin consist of more than 250 m of interbedded sandstone and subordinate conglomerate overlain by volcanics. Sandstones are dominately cross-stratified tabular and sigmoidal beds. Paleocurrents are bimodal with a dominant north to south transport direction. Marine fossils are dispersed through the sandstones. Conglomerates are thin beds of cobble to boulder clasts. Some show southward imbrication; others are inversely graded. Fossils are rare in the conglomerates. The sandstones are interpreted as tidal sand waves and tidal bundles; conglomerates are interpreted as storm lag and debris flow deposits.

The fossil assemblage includes gastropods, pelecypods, barnacles, and echinoids indicative of a shallow marine, cold-water biofacies. Taxa indicate

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a strong similarity to the fossil assemblage of the Tachilni Formation and the upper Bear Lake Formation, both assigned to the late Miocene Graysian Molluscan stage, approximately 12 Ma to 3 Ma.

Teeth of the desmostylian (sea cow) Desmostylus sp. cf. D. hesperus have been collected from the Cape Aliaksin beds. D. hesperus is known from North Pacific rocks assigned to the late early to early late Miocene, approximately 18 Ma to 10 Ma.

The Unga Conglomerate is in part typified by the middle Miocene pelecypod Mytilus gratacapi and an associated fauna unlike that of the Cape Aliaksin beds. It is suggested that the Cape Aliaksin beds are younger than the Unga Conglomerate, and are correlative to the upper Bear Lake Formation and Tachilni Formation rocks of early late Miocene age.

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