Molalla Clay Products, Clackamas Co., Oregon, USA

Age: Pleistocene (0 - 2.588 Ma)

Description: Sand and gravel that predates Missoula Floods; <100m thick; coarse grained sediments

Lithology: Major:: {lahar, gray; subrounded pumice, angular lithic fragments, light gray angular glassy rhyodacite, angular black obsidian fragments; lithology: pumiceous; pumice grains grains}; Major:: {sand, cementation: clay, calcite, and iron oxides}; Major:: {silt, pumice grains grains}; Major:: {gravel}; Major:: {paleosol}; Major:: {gravel, pumice grains grains}; Major:: {sand, pumice grains grains}; Major:: {sandy silt, ; pumice grains grains; oxidation: translocated clay and iron oxides; zones: zones of clay; weathering: weathering profiles of about 3m, argillic horizons}

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: Pleistocene (0.0117 - 2.588 Ma)

Stratigraphic Name: Willamette Silt; Gresham Formation; Estacada Formation

Description: Unconsolidated to semiconsolidated lacustrine clay, silt, sand, and gravel; in places includes mudflow and fluvial deposits and discontinuous layers of peat. Includes older alluvium and related deposits of Piper (1942), Willamette Silt (Allison, 1953; Wells and Peck, 1961), alluvial silt, sand, and gravel that form terrace deposits of Wells and others (1983), and Gresham and Estacada Formations of Trimble (1963). Includes deltaic gravel and sand and gravel bars, in pluvial lake basins in southeastern part of map area. In Rome Basin, includes discontinuous layers of poorly consolidated conglomerate characterized by well-rounded, commonly polished pebbles of chert and pebbles and cobbles of quartzite. In places contains mollusks or vertebrate fossils indicating Pleistocene age; mostly deposits of late Pleistocene age, but locally includes some deposits of early Holocene age. Includes Touchet Beds of Flint (1938), deposits of valley terraces of Newcomb (1965), and, in southeast Oregon, basin-filling deposits that incorporate Mazama ash deposits (Qma, Qmp) in the youngest layers

Lithology: Major:{clay,silt,sand}, Minor:{gravel}, Incidental:{peat}

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]

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]