Sheaville, Malheur Co., Oregon, USA

Age: Pleistocene (0 - 2.588 Ma)

Description: Alluvium; unconsolidated rocks; mixed grained sediments; fluvial

Lithology: Major:: {mixed fluvial sediment} Minor:: {mixed alluvial fan sediment}; Minor:: {colluvium}; Minor:: {mixed playa sediment}

Reference: R.L. Smith, W.P. Roe (compilers). Oregon Geologic Data Compilation, release 6. State of Oregon Department of Geology and Mineral Industries. [20]

Age: Neogene (2.588 - 23.03 Ma)

Stratigraphic Name: Columbia River Basalt

Comments: Columbia Plateau

Lithology: Flood basalt(s); mafic volcanic rocks; basalt

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Age: Miocene (5.333 - 23.03 Ma)

Stratigraphic Name: Mascall Formation; Succor Creek Formation; Drip Spring Formation; Trout Creek Formation; Picture Gorge Basalt

Description: Moderately well indurated lacustrine and fluvial (flood-plain) deposits of tuff, pumicite, palagonite tuff, and lesser siltstone, arkosic sandstone, and pebble and cobble conglomerate. Locally contains some lignite beds. Former glass in silicic vitroclastic debris commonly crystallized and altered to secondary silica minerals, alkali feldspar, zeolites, and clay minerals. Contains some welded and nonwelded ash-flow tuffs, and minor rhyolite flows. Widespread and abundant vertebrate fossils and minor plant fossils indicate that most of unit is of middle Miocene (Barstovian) age; parts of unit between Goose Lake and Warner Valley may include rocks of early Miocene age. Locally interlayered with and locally overlies basalt and andesite flows of unit Tmb. Overlies and locally interfingers with Picture Gorge Basalt (Thayer and Brown, 1966) and with Miocene basalt south of Prineville. Includes Mascall Formation of Merriam (1901), Sucker (Succor) Creek Formation of Corcoran and others (1962) and Kittleman and others (1967), Drip Spring Formation of Kittleman and others (1965, 1967), Trout Creek Formation of Smith (1926), and "rocks of Miocene age" of Malde and Powers (1962) in the southern Owyhee Upland province. In southeast Oregon, some of these rocks represent caldera and moat-fill deposits

Lithology: Major:{rhyolite}, Minor:{siltstone,arkose,conglomerate,lignite}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]