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Grande Ronde Basalt (middle and lower Miocene)

Flows of dark-gray to black, aphyric tholeiitic basalt, including both high- and low-Mg chemical types (Swanson and others, 1979). Potassium-argon ages mostly in the range of 15 to 17 Ma (Lux, 1982; Watkins and Baksi, 1974; Fiebelkorn and others, 1983)
State Oregon
Name Grande Ronde Basalt (middle and lower Miocene)
Geologic age Early to Middle Miocene
Comments In La Grange 30' x 60' quadrangle (OR291), unit is divided into: N2 magnetostratigraphic unit (msu; middle Miocene), pyroclastic vent deposits (middle Miocene), Ferroandesite of Fiddlers Hell (middle Miocene), R2 msu (middle Miocene), N1 msu (middle Miocene), and R1 msu (lower and middle Miocene). Radiometric ages range from about 15.5 to 17 Ma. In Umatilla River Basin (OR292), unit includes Fiddlers Hell Member, N2 magnetostratigraphic unit (msu) , Sentinel Bluffs unit, Winter Water unit, R2 msu, and N1 msu. Radiometric ages range from about 15.5 to 16.1
Primary rock type basalt
Secondary rock type
Other rock types
Lithologic constituents
Major
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow)
Map references
Walker, G.W. and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000.
Unit references
Walker, G.W. and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000.
Fiebelkorn, R.B., Walker, G.W., Macleod, N.S., McKee, E.H., and Smith, J.G., 1983, Index to K-Ar determinations for the State of Oregon: Isochron/West, no. 37, p. 3-60.
Prostka, H.J., 1962, Geology of the Sparta quadrangle, Oregon: Oregon Department of Geology and Mineral Industries Geologic Map Series GMS-1, scale 1:62,500.
Swanson, D.A., Wright, T.L., Hooper, P.R., and Bentley, R.D., 1979, Revisions in stratigraphic nomenclatire of the Columbia River Basalt Group: U.S. Geological Survey Bulletin1457-G, p. G1-G59.
Brooks, H.C., McIntyre, J.R., and Walker, G.W., 1976, Geology of the Oregon part of the Baker 1o by 2o quadrangle: Oregon Department of Geology and Mineral Industries Geologic Map Series GMS-7, scale 1:250,000.
Walker, G.W., 1979, Reconnaissance geologic map of the Oregon part of the Grangeville quadrangle, Baker, Union, Umatilla, and Wallowa Counties, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-1116, scale 1;250,000
Walker, G.W., 1973, Reconnaissance geologic map of the Pendleton quadrangle, Oregon and Washington: U.S. Geological Survey Miscellaneus Geologic Investigations Map I-727, scale 1:250,000.
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.
Lux, D.R., 1982, K-Ar and 40Ar/39Ar ages of mid-Tertiary volcanic rocks from the Western Cascade Range, Oregon: Isochron/West, no. 33, p. 27-32.
Watkins, N.D. and Baksi, A.K., 1974, Magnetostratigraphy and oroclinal folding of the Columbia River, Steens, and Owyhee Basalts in Oregon, Washington, and Idaho: American Journal of Science, v. 274, no. 2, p. 148-149.
Brooks, H.C., 1979, Geologic map of the Oregon part of the Mineral quadrangle: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-12, scale 1:62,500.
Evans, J.G., 1989, Geologic map of the Desolation Butte quadrangle, Grant and Umatilla Counties, Oregon: U.S. Geological Survey Geologic Quadrangle GQ-1654, scale 1:62,500.
Barrash, Warren, Bond, J.G., Kauffmann, J.D., and Venkatakrishnan, Ramesh, 1980, Geology of the La Grande area, Oregon: Oregon Department of Geology and Mineral Industries Special Paper 6, 67 p., 4 maps, scale 1:24,000.
Ferns, M.L., Madin, I.P., and Taubeneck, W.H., 2001, Reconnaissance geologic map of the La Grande 30' x 60' quadrangle, Baker, Grant, Umatilla, and Union Counties, Oregon: Oregon Department of Geology and Mineral Industries Reconnaissance Map Series RMS-1, 52 p., scale 1:100,000.
Ferns, M.L., McConnell, V.S., and Madin, I.P., in prep., Geology of the Umatilla River Basin, Morrow, Umatilla, and Union Counties, Oregon: Oregon Department of Geology and Mineral Industries Open-File Report, 66 p., scale 1:100,000.
Ferns, M.L., 1999, Geologic map of the Fly Valley quadrangle, Union County, Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-113, scale 1:24,000.
Madin, I.P., 1998, Geologic map of the Tucker Flat quadrangle, Union and Baker Counties, Oregon: Oregon Department of Geology and Mineral Industries Geological map Series GMS-110, scale 1;24,000.
Brown, D.E., Black, G.L., and McLean, G.D., 1980, Preliminary geology and geothermal resource potential of the Craig Mountain-Cove area, , Oregon: Oregon Department of Geology and Mineral Industries Open-File Report O-80-04, 68 p., 1 map.
Ferns, M.L. and Madin, I.P., 1999, Geologic map of the Summerville quadrangle, Union County, Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-111, scale 1:24,000.
Ferns, M.L., McConnell, V.S., Madin, I.p., and Van Tassell, 2002, Geology of the Imbler quadrangle, Union County, Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-114, scale 1:24,000.
Madin, I.P. and Taubeneck, W.H., 2003, Geologic map of the Amnthony Buttes quadrangle, Union and Baker Counties, Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-107, scale 1:24,000.
Weiss, P.L., Gualtieri,, J.L., Cannon, W.F., Tucher, E.T., McMahan, A.B., and Federspiel, F.E., 1976, Mineral resources of the Eagle Cap Wilderness and adjacent areas, Oregon: U.S. Geological Survey Bulletin 1385-E, 100 p.
Ferns, M.L. and Taubeneck, W.H., 1994, Geology and mineral resources of the Limber Jim Creek quadrangle, Union County, Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-82, scale 1:24,000.
Waters, A.C., 1968, Reconnaissance geologic map of the Madras quadrangle, Jeffereson and Wasco Counties, Oregon" U.S. Geological Survey Miscellaneous Geological Investigations Map I-555, scale 1;125,000.
Counties Baker - Clackamas - Clatsop - Gilliam - Grant - Hood River - Jefferson - Marion - Morrow - Multnomah - Polk - Sherman - Umatilla - Union - Wallowa - Wasco - Wheeler - Yamhill