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Board) directed staff to convene a team of independent scientific experts to provide input regarding sediment impairment in the Freshwater, Bear, Jordan, Stitz, and Elk River watersheds. The panel was convened in August of 2002, and, produced the above-noted document o

Revisions to the Cenozoic stratigraphy of Harney Basin, southeastern Oregon

ABSTRACT Harney Basin in southeastern Oregon has persisted as a site of deposition during essentially all of late Cenozoic time; the basin is filled with a sequence of continental volcanic, volcaniclastic, and tuffaceous sedimentary rocks derived from voluminous and widespread basaltic and rhyolitic volcanism. Many rock units are confined to small areas of Harney Basin, whereas others extend beyond the limits of the basin. Included among the latter are a few thick prisms of basalt and related palagonite tuffs, and several late Miocene ash-flow tuffs that cover tens of thousands of square kilometers in eastern Oregon. The ash-flow tuffs, which represent unique time-stratigraphic marker horizons, occur in lithologic sequences within a number of neighboring depositional basins, where they have been given various formal and informal formational names. In order to clarify the stratigraphic nomenclature of Harney Basin and adjacent regions, three of the ash-flow tuffs the Devine Canyon Ash-flow Tuff, the Prater Creek Ash-flow Tuff, and the Rattlesnake Ash-flow Tuff are redefined as formations. In this report their distribution and relations to other stratigraphic units are described, and the terminology of other formational units of which they formerly were a part is revised