Youngest basalt and basaltic andesite

Little-modified flows and associated breccia of basaltic andesite and some basalt in both central part of Cascade Range and on slopes of Newberry Volcano. Relations to Mazama pumice deposits indicate most of these rocks are less than 6,800 yr old (14C); isotopic ages on flows range from about 1,000 to 6,000 yr B.P. (14C)
State Oregon
Name Youngest basalt and basaltic andesite
Geologic age Holocene
Lithologic constituents
Major
Igneous > Volcanic > Mafic-volcanic > Basaltic-andesite (Flow)
Minor
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow)
Incidental
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Pyroclastic-air fall)Mazama ash
Comments Unit also occurs in eastern Oregon.
References

Walker, G.W. and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000.

Walker, G.W. and Repenning, C.A., 1966, Geologic map of the west half of the Jordan Valley quadrangle, Malheur County, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-457, scale 1:250,000.

https://pubs.er.usgs.gov/publication/i457

Ferns, M.L., Evans, J.G., and Cummings, M.L., 1993a, Geologic map of the Mahogany Mountain 30 x 60 minute quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-78, scale 1:100,000.

Walker, G.W., 1977, Geologic map of Oregon east of the 121st meridian: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-902, scale 1:500,000.

https://pubs.er.usgs.gov/publication/i902

Hart, W.K. and Mertzman, S.A., 1983, Late Cenozoic volcanic stratigraphy of the Jordan Valley area, southeastern Oregon: Oregon Geology, v. 45, no. 1, p. 15-19.

Ferns, M.L., 1992, Preliminary geologic map of the Bogus Bench quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-92-02, scale 1:24,000.

Ferns, M.L. and Macleod, N.S., 1992, Preliminary geologic map of the Cow Lakes quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-92-06, scale 1:24,000.

Ferns, M.L.1992, Preliminary geologic map of the Downey Canyon quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-92-07, scale 1:24,000.

NGMDB product
Counties Clackamas - Crook - Deschutes - Douglas - Hood River - Jefferson - Klamath - Lake - Lane - Linn - Malheur - Wasco