Basalt and basaltic andesite

Thin flows of aphyric and porphyritic basalt and basaltic andesite, and open-textured (dikytaxitic), generally nonporphyritic, subophitic olivine basalt that commonly is highly feldspathic. Also includes some dissected intracanyon flows of porphyritic basalt and related vent complexes. Pressure ridges and tumuli on upper surfaces well preserved. Occurs principally along crest of Cascade Range; also in areas near and east of Newberry volcano, along southeast margin of Harney Basin, and in Rome Basin. Older than Mazama ash deposits (Qma, Qmp; approximately 6,800 yr old; 14C)
State Oregon
Name Basalt and basaltic andesite
Geologic age Pleistocene to Holocene
Lithologic constituents
Major
Igneous > Volcanic > Mafic-volcanic > Basaltic-andesite (Flow)
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow)
Comments Similar flows along the Owyhee River south of Rome (OR147) are included in map unit Tb.
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

Greene, R.C., Walker, G.W., and Corcoran, R.E., 1972, Geologic map of the Burns quadrangle, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-680, scale 1:250,000.

https://pubs.er.usgs.gov/publication/i680

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., 1992, Preliminary geologic map of the Mustang Butte quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-92-11, scale 1:24,000.

Ferns, M.L., 1992, Preliminary geologic map of the Sacramento Butte quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-92-13, scale 1;24,000.

Ferns, M.L., 1992, Preliminary geologic map of the Saddle Butte quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-92-14, scale 1:24,000.

Ferns, M.L., 1992, Preliminary geologic map of the Wrangle Butte quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-92-15, scale 1:24,000.

Ferns, M.L. and Evans, J.G., 1993c, Preliminary geologic map of the Rinehart Canyon quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-93-5, scale 1: 24,000.

Camp, V.E., Ross, M.E., and Hanson, W.E., 2003, Genesis of flood basalts and Basin and Range volcanic rocks from Steens Mountain to the Malheur River Gorge, Oregon: Geological Society of America Bulletin, v. 115, no. 1, p. 105-128.

Vander Meulen, B.B., Rytuba, J.J., Grubensky, M.J., Vercoutere, T.L., and Minor, S.A., 1987, Geologic map of the Pelican Point quadrangle, Malheur County, Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-1904, scale 1:24,000.

https://pubs.er.usgs.gov/publication/mf1904

Vander Meulen, D.B., Rytuba, J.J., Vercoutere, T.L., and Minor, S.A., 1987, Geologic map of the Rooster Comb 7.5' quadrangle, Malheur County, Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-1902C, scale 1:24,000.

https://pubs.er.usgs.gov/publication/mf1902

NGMDB product
Counties Crook - Deschutes - Douglas - Harney - Jefferson - Klamath - Lake - Malheur - Wheeler