Silicic ash-flow tuff (ORTat;0)

Silicic ash-flow tuff

Ash-flow tuff and associated pumiceous air-fall tuff mostly of rhyolitic and rhyodacitic composition; includes minor tuffaceous sedimentary rocks. Grades laterally through less-densely welded tuff to nonwelded ash-flow tuff and interlayered tuffaceous sediments of unit Ts. Potassium-argon ages (Greene and others, 1972; Parker and Armstrong, 1972; Walker, 1979; McKee and others, 1976) on several different ash-flow tuffs included in unit range from about 4 to 10 Ma; although most ages are in the range of 6 to 9 Ma. Includes the Devine Canyon, Prater Creek, and Rattlesnake Ash-flow Tuffs (Walker, 1979), originally considered a part of the (now obsolete) Danforth Formation of Piper and others (1939), and the Rattlesnake Formation and the volcanic and fluvial deposits (undivided) and marginal facies of the Columbia River Group (undivided) of Brown and Thayer (1966). Also includes the welded soda--rhyolite tuff breccia of Dickinson and Vigrass (1965) in the Suplee-Izee area, the upper Miocene or lower Pliocene welded tuff of Prostka (1962; 1967) in the Baker area. "Welded ash-flow tuff" of Swanson (1969a) and the Pliocene Peyerl Tuff (Hampton, 1964) west of Fort Rock Valley, dated at about 4.5 Ma (McKee and others, 1976)

State	Oregon
Name	Silicic ash-flow tuff
Geologic age	Late Miocene to Early Pliocene
Lithologic constituents	Major Igneous > Volcanic > Felsic-volcanic > Rhyolite (Pyroclastic-air fall, Pyroclastic-ash flow)Also contains rhyodacitic pyroclastic rocks Igneous > Volcanic > Felsic-volcanic > Dacite (Pyroclastic-ash flow) Minor Sedimentary > Clastic > Mixed-clastic > Sandstone-mudstone (Bed)
Comments	Includes the Wildcat Creek Welded Ash-Flow Tuff (est. 13-14 Ma; OR156; OR157).
Stratigraphic units	Devine CanyonAsh-Flow Tuff (OR026), Prater Creek Ash-Flow Tuff (OR026), Rattlesnake Ash-Flow Tuff (OR026), Danforth Formation (obsolete) (OR018), Columbia River Group (OR008), Peyerl Tuff (OR032), Wildcat Creek Welded Ash-Flow Tuff (OR156; OR157)
References	Walker, G.W. and MacLeod, N.S., 1991, Geologic map of Oregon: U.S. Geological Survey, scale 1:500,000. 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. Ferns, M.L., Brooks, H.C., Evans, J.G., and Cummings, M.L., 1993b, Geologic map of the Vale 30 x 60 minute quadrangle, Malheur County Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-77, scale 1:100,000. Brown, C.E. and Thayer, T.P., 1966, Geologic map of the Canyon City quadrangle, northeastern Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-447, scale 1:250,000. https://pubs.er.usgs.gov/publication/i447 Piper, A.M., Robinson, T.W., and Park, C.F., Jr., 1939, Geology and ground-water resources of the Harney Basin, Oregon: U.S. Geological Survey Water-Supply Paper 842, 189 p. https://pubs.er.usgs.gov/publication/wsp842 Parker, Donald and Armstrong, R.L., 1972, K-Ar dates and Sr isotope initial ratios for volcanic rocks in the Harney Basin, Oregon: Isochron/West, no. 5, p. 7-12. Walker, G.W., 1979, Revisions to the stratigraphy of Harney Basin, southeastern Oregon: U.S. Geological Survey Bulletin 1475, 35 p. https://pubs.er.usgs.gov/publication/b1475 McKee, E.H., MacLeod, N.S., and Walker, G.W., 1976, Potassium-argon ages of late Cenozoic silicic volcanic rocks, southeast Oregon: Isochron/West, no. 15, p. 37-41. Dickinson, W.R. and Vigrass, L.W., 1965, Geology of the Suplee-Izee area, Crook, Grant, and Harney Counties, Oregon: Oregon Department of Geology and Mineral Industries Bulletin 58, 109 p. 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. Prostka, H.J., 1967, Preliminary geologic map of the Durkee quadrangle, Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-3, scale 1, 62,500. Swanson, D.A., 1969a, Reconnaissance geologic map of the east half of the Bend quadrangle, Crook, Wheeler, Jefferson, Wasco, , and Deschutes Counties, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-568, scale 1:250,000. https://pubs.er.usgs.gov/publication/i568 Hampton, E.R., 1964, Geologic factors that control the occurrence and availability of groundwater in the Fort Rock Basin, Lake County, Oregon: U.S. Geological Survey Professional Paper 383-B, p. B1-B29. https://pubs.er.usgs.gov/publication/pp383B 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., 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 Walker, G.W., Peterson, N.V., and Greene, R.C., 1967, Reconnaissance geologic map of the east half of the Crescent quadrangle, Lake, Deschutes, and Crook Counties, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-493, scale 1:250,000. https://pubs.er.usgs.gov/publication/i493 MacLeod, N.S. and Sherrod, D.R., 1992, Reconnaisance geologic map of the west half of the Crescent quadrangle, central Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-2215, scale 1:250,000. https://pubs.er.usgs.gov/publication/i2215 Wolff, E.N., 1965, The geology of the northern half of the Caviness quadrangle, Oregon: Eugene, University of Oregon, Ph.D. dissertation, 214 p. Evans, J.G., Geologic map of the Dooley Mountain quadrangle, Baker County, Oregon: U.S. Geological Survey Geological Quadrangle GQ-1694, scale 1: 24,000. https://pubs.er.usgs.gov/publication/gq1694 Ferns, M.L., 1989, Geology and mineral resources map of the Graveyard Point quadrangle, Malheur Count Oregon, and Owyhee County, Idaho: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-54, scale 1:24,000. Rytuba, J.J. and Vander Meulen, D.B., 1991, Hot-spring precious-metal systems in the Lake Owyhee Volcanic Field, Oregon-Idaho, in Raines, G., Lisle, R.E., Schafer, R.W., and Wilkinson, W.H., eds., Geology and ore deposits of the Great Basin, Symposium Proceedings: Geological Society of Nevada, v. 2, p. 1,085-1,096. Evans, J.G. and Binger, Geologic map of the Shumway Reservoir Quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 98-138, scale 1:24,000. https://pubs.er.usgs.gov/publication/ofr98138 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. https://pubs.er.usgs.gov/publication/gq1654 Evans, J.G. and Binger, G.B., 1998, Geologic map of the Little Black Canyon quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 98-493, scale 1:24,000. https://pubs.er.usgs.gov/publication/ofr98493 Evans, J.G. and Binger, G.B., 1998, Geologic map of the Alder Creek quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 98-484, scale 1:24,000. https://pubs.er.usgs.gov/publication/ofr98484 Evans, J.G. and Binger, G.B., 1999, Preliminary geologic map of the Skull Springs quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 99-381, scale 1:24,000. https://pubs.er.usgs.gov/publication/ofr99381 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. Evans, J.G. and Binger, G.B., 1998, Geologic map of the Shumway Reservoir quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 98-138, scale 1:24,000. https://pubs.er.usgs.gov/publication/ofr98138 Evans, J.G., 1996, Geologic map of the Monument Peak quadrangle, Malheur County, Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-2317, scale 1:24,000. https://pubs.er.usgs.gov/publication/mf2317 Evans, J.G. and Keith, W.J., 1996, Geologic map of the Tims Peak quadrangle, Malheur County, Oregon: U. S. Geological Survey Miscellaneous Field Studies Map MF-2316, scale 1:24,000. Sherrod, D.R. and Johnson, J.A., 1994, Geologic map of the Irish Lake quadrangle, Harney County, south-central Oregon: U.S. Geological Survey Miscellaneous Field studies Map MF-2256, scale 1:24,000. https://pubs.er.usgs.gov/publication/mf2256 Minor, S.A., Rytuba, J.J., Grubensky, M.J., Vander Meulen, D.B., Goeldner, C.A., and Tegtmeyer, K.J., 1987, Geologic map of the High Steens and Little Blitzen Gorge Wilderness Study Areas, Harney County, Oregon: U.S. Geological Surevy Miscellaneous Field Studies Map MF-1876, scale 1:24,000. Evans, J.G., 1993, Geologic map of the Brannan Gulch quadrangle, Baker County, Oregon: U.S. Geological Survey Geological Quadrangle GQ-1744, scale 1:24,000. https://pubs.er.usgs.gov/publication/gq1744 Prostka, H.J., 1968, Geologic map of the Ironside 15' quad, Oregon: Oregon Department of Geology and Mineral Industries, scale 1:62,500. Evans, J.G., Rytuba, J.J., Binger, G.B., and Hooper, P.R., 1999, Preliminary geologic map of the Star Creek Reservoir quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 99-583, scale 1:24,000. https://pubs.er.usgs.gov/publication/ofr99583 Ferns, M.L. and Williams, C.P., 1993, Preliminary geologic map of the Burnt Flat quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-93-2, scale 1:24,000. Ferns, M.L. and Williams, C.P., 1993, Preliminary geologic map of the Crowley quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-93-04, 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. Johnson, J.A., 1994, Geologic map of the Krumbo Reservoir quadrangle, Harney County, southeastern Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-2267, scale 1:24,000 https://pubs.er.usgs.gov/publication/mf2267 Johnson, J.A., 1996, Geologic map of the Page Spring quadrangle, Harney County, southeastern Oregon: U.S. Geological Survey Open-File Report 96-675, scale 1:24,000. https://pubs.er.usgs.gov/publication/ofr96675 Johnson, J.A., 1995, Geologic evolution of the Duck Butte eruptive center, High Lava Plains, southeastern Oregon: Corvallis, Oregon State University, master's thesis, 151 p. Johnson, J.A. and Grunder, A.l., 2000, The making of intermediate compositional magma in a bimodal suite: Duck Butte eruptive center, Oregon, USA: Journal of Volcanology and Geothermal Research, v. 95, p. 175-195. Johnson, J.A., Hooper, P.R., Hawkesworth, C.J., and Binger, G.B., 1998b, Geologic map of the Stemmler Ridge quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 98-105, scale 1:24,000. https://pubs.er.usgs.gov/publication/ofr98105 Whitsun, N.W., 1988, Geochemical stratigraphy of the Dooley Rhyolite Breccia and Tertiary basalts in the Dooley Mountain quadrangle, Oregon: Portland, Oregon, Portland State University, master's thesis, 122 p. Wood, J.D., 1976, The geology of the Castle Rock area, Grant, Harney, and Malheur Counties, Oregon: Portland, Oregon, Portland State University, master's thesis, 89 p.
NGMDB product	NGMDB product page for 16259
Counties	Baker - Crook - Deschutes - Grant - Harney - Jackson - Klamath - Lake - Malheur

Silicic ash-flow tuff

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

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.

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.

Ferns, M.L., Brooks, H.C., Evans, J.G., and Cummings, M.L., 1993b, Geologic map of the Vale 30 x 60 minute quadrangle, Malheur County Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-77, scale 1:100,000.

Brown, C.E. and Thayer, T.P., 1966, Geologic map of the Canyon City quadrangle, northeastern Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-447, scale 1:250,000.

Piper, A.M., Robinson, T.W., and Park, C.F., Jr., 1939, Geology and ground-water resources of the Harney Basin, Oregon: U.S. Geological Survey Water-Supply Paper 842, 189 p.

Parker, Donald and Armstrong, R.L., 1972, K-Ar dates and Sr isotope initial ratios for volcanic rocks in the Harney Basin, Oregon: Isochron/West, no. 5, p. 7-12.

Walker, G.W., 1979, Revisions to the stratigraphy of Harney Basin, southeastern Oregon: U.S. Geological Survey Bulletin 1475, 35 p.

McKee, E.H., MacLeod, N.S., and Walker, G.W., 1976, Potassium-argon ages of late Cenozoic silicic volcanic rocks, southeast Oregon: Isochron/West, no. 15, p. 37-41.

Dickinson, W.R. and Vigrass, L.W., 1965, Geology of the Suplee-Izee area, Crook, Grant, and Harney Counties, Oregon: Oregon Department of Geology and Mineral Industries Bulletin 58, 109 p.

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.

Prostka, H.J., 1967, Preliminary geologic map of the Durkee quadrangle, Oregon: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-3, scale 1, 62,500.

Swanson, D.A., 1969a, Reconnaissance geologic map of the east half of the Bend quadrangle, Crook, Wheeler, Jefferson, Wasco, , and Deschutes Counties, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-568, scale 1:250,000.

Hampton, E.R., 1964, Geologic factors that control the occurrence and availability of groundwater in the Fort Rock Basin, Lake County, Oregon: U.S. Geological Survey Professional Paper 383-B, p. B1-B29.

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

Walker, G.W., Peterson, N.V., and Greene, R.C., 1967, Reconnaissance geologic map of the east half of the Crescent quadrangle, Lake, Deschutes, and Crook Counties, Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-493, scale 1:250,000.

MacLeod, N.S. and Sherrod, D.R., 1992, Reconnaisance geologic map of the west half of the Crescent quadrangle, central Oregon: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-2215, scale 1:250,000.

Wolff, E.N., 1965, The geology of the northern half of the Caviness quadrangle, Oregon: Eugene, University of Oregon, Ph.D. dissertation, 214 p.

Evans, J.G., Geologic map of the Dooley Mountain quadrangle, Baker County, Oregon: U.S. Geological Survey Geological Quadrangle GQ-1694, scale 1: 24,000.

Ferns, M.L., 1989, Geology and mineral resources map of the Graveyard Point quadrangle, Malheur Count Oregon, and Owyhee County, Idaho: Oregon Department of Geology and Mineral Industries Geological Map Series GMS-54, scale 1:24,000.

Evans, J.G. and Binger, Geologic map of the Shumway Reservoir Quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 98-138, scale 1:24,000.

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.

Evans, J.G. and Binger, G.B., 1998, Geologic map of the Little Black Canyon quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 98-493, scale 1:24,000.

Evans, J.G. and Binger, G.B., 1998, Geologic map of the Alder Creek quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 98-484, scale 1:24,000.

Evans, J.G. and Binger, G.B., 1999, Preliminary geologic map of the Skull Springs quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 99-381, scale 1:24,000.

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.

Evans, J.G. and Binger, G.B., 1998, Geologic map of the Shumway Reservoir quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 98-138, scale 1:24,000.

Evans, J.G., 1996, Geologic map of the Monument Peak quadrangle, Malheur County, Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-2317, scale 1:24,000.

Evans, J.G. and Keith, W.J., 1996, Geologic map of the Tims Peak quadrangle, Malheur County, Oregon: U. S. Geological Survey Miscellaneous Field Studies Map MF-2316, scale 1:24,000.

Sherrod, D.R. and Johnson, J.A., 1994, Geologic map of the Irish Lake quadrangle, Harney County, south-central Oregon: U.S. Geological Survey Miscellaneous Field studies Map MF-2256, scale 1:24,000.

Minor, S.A., Rytuba, J.J., Grubensky, M.J., Vander Meulen, D.B., Goeldner, C.A., and Tegtmeyer, K.J., 1987, Geologic map of the High Steens and Little Blitzen Gorge Wilderness Study Areas, Harney County, Oregon: U.S. Geological Surevy Miscellaneous Field Studies Map MF-1876, scale 1:24,000.

Evans, J.G., 1993, Geologic map of the Brannan Gulch quadrangle, Baker County, Oregon: U.S. Geological Survey Geological Quadrangle GQ-1744, scale 1:24,000.

Prostka, H.J., 1968, Geologic map of the Ironside 15' quad, Oregon: Oregon Department of Geology and Mineral Industries, scale 1:62,500.

Evans, J.G., Rytuba, J.J., Binger, G.B., and Hooper, P.R., 1999, Preliminary geologic map of the Star Creek Reservoir quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 99-583, scale 1:24,000.

Ferns, M.L. and Williams, C.P., 1993, Preliminary geologic map of the Burnt Flat quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-93-2, scale 1:24,000.

Ferns, M.L. and Williams, C.P., 1993, Preliminary geologic map of the Crowley quadrangle, Malheur County, Oregon: Oregon Department of Geology and Mineral Industries Open-File Map O-93-04, 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.

Johnson, J.A., 1994, Geologic map of the Krumbo Reservoir quadrangle, Harney County, southeastern Oregon: U.S. Geological Survey Miscellaneous Field Studies Map MF-2267, scale 1:24,000

Johnson, J.A., 1996, Geologic map of the Page Spring quadrangle, Harney County, southeastern Oregon: U.S. Geological Survey Open-File Report 96-675, scale 1:24,000.

Johnson, J.A., 1995, Geologic evolution of the Duck Butte eruptive center, High Lava Plains, southeastern Oregon: Corvallis, Oregon State University, master's thesis, 151 p.

Johnson, J.A. and Grunder, A.l., 2000, The making of intermediate compositional magma in a bimodal suite: Duck Butte eruptive center, Oregon, USA: Journal of Volcanology and Geothermal Research, v. 95, p. 175-195.

Johnson, J.A., Hooper, P.R., Hawkesworth, C.J., and Binger, G.B., 1998b, Geologic map of the Stemmler Ridge quadrangle, Malheur County, Oregon: U.S. Geological Survey Open-File Report 98-105, scale 1:24,000.

Whitsun, N.W., 1988, Geochemical stratigraphy of the Dooley Rhyolite Breccia and Tertiary basalts in the Dooley Mountain quadrangle, Oregon: Portland, Oregon, Portland State University, master's thesis, 122 p.

Wood, J.D., 1976, The geology of the Castle Rock area, Grant, Harney, and Malheur Counties, Oregon: Portland, Oregon, Portland State University, master's thesis, 89 p.