Molalla High-Alumina Clay Occurrence, Clackamas Co., Oregon, USA

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: Columbia River Basalt Group

Description: Yakima Basalt Subgroup Of The Columbia River Basalt Group; 300m thick; basalt

Lithology: Major:: {basaltic andesite flows, gray, dark gray}; Major:: {basalt flows, gray, dark gray}

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: Miocene (5.333 - 23.03 Ma)

Stratigraphic Name: Saddle Mountains Basal; Wanapum Basalt; Grande Ronde Basalt; Picture Gorge Basalt; Imnaha Basalt

Description: Subaerial basalt and minor andesite lava flows and flow breccia; submarine palagonitic tuff and pillow complexes of the Columbia River Basalt Group (Swanson and others, 1979); locally includes invasive basalt flows. Flows locally grade laterally into subaqueous pillow-palagonite complexes and bedded palagonitic tuff and breccia. In places includes tuffaceous sedimentary interbeds. Joints commonly coated with nontronite and other clayey alteration products. Occurs principally in the Willamette Valley from Salem north to the Columbia River, and in the northern Coast Range. Unit includes correlative Cape Foulweather and Depoe Bay Basalts in the Coast Range (Snavely and others, 1973, 1976a, 1976b; Swanson and others, 1979; Wells and others, 1983). In Eastern Oregon, occurs principally in Deschutes-Umatilla Plateau and in the Blue Mountains. K-Ar ages range from about 6 to about 16.5 Ma (McKee and others, 1977; Swanson and others, 1979; Sutter, 1978; Lux, 1982). Locally separated into Tcs, Tcw, Tcg, Tcp, and Tci

Lithology: Major:{basalt}, Minor:{andesite,sandstone mudstone}

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]