Note: This paper is dedicated to Aaron and Elizabeth Waters on the occasion of Dr. Waters' retirement.

Several new chemical analyses of flows confined to a structural downwarp in northeastern Oregon indicate the first reported occurrence of Late-Yakima–type basalt in the region and the close stratigraphic association of Yakima–type and Late-Yakima–type flows, as well as andesite. The andesite is the most silicic flow rock yet found on the Columbia Plateau.

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