Volcanic and metavolcanic rocks

Green to gray spilite and keratophyre flows and flow breccia; and subordinate amounts of coarse volcaniclastic sandstone, tuff, sandstone, siltstone, chert, conglomerate, and limestone. Marine fauna from interlayered sedimentary rocks indicates unit is mostly of Karnian (Late Triassic) age. Includes Late Triassic "andesitic and basaltic rocks" of Nolf and Taubeneck (1963), and the basaltic to rhyolitic metavolcanic rocks and interbedded sedimentary rocks of the Huntington Formation of Brooks (1979). Equivalent, in part, to unit TrPv
State Oregon
Name Volcanic and metavolcanic rocks
Geologic age Late Triassic
Lithologic constituents
Major
Igneous > Volcanic (Flow)Keratophyre
Metamorphic > Hydrothermally-altered > Spilite
Minor
Sedimentary > Chemical > Chert (Bed)
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Carbonate > Limestone (Bed)
Sedimentary > Clastic > Conglomerate (Bed)
Sedimentary > Clastic > Sandstone (Bed, Tuffaceous)coarse volcaniclastic sandstone, tuff, sandstone
Metamorphic > Metaigneous > MetavolcanicIncludes Late Triassic "andesitic and basaltic rocks" of Nolf and Taubeneck (1963), and the basaltic to rhyolitic metavolcanic rocks
Comments Huntington Formation (OR073) is predominantly agglomerate, tuff, and flows intercalated with coarse volcaniclastic breccia and conglomerate. Also contains volcanic graywacke, volcanic arenite, water-laid tuff, volcanic siltstone, and minor limestone. Volcanic rocks range from basalt to rhyolite; andesite is the most common lithology. Fine-grained sedimentary rocks typically form bedded sequences ranging from a few meters to a few hundred meters thick. Includes dikes, sills, and irregular shallow intrusive bodies that are difficult to distinguish from extrusive rocks. The rocks have been metamorphosed to the zeolite and greenschist facies of regional metamorphism. Fossil ammonites and Halobia indicate marine depositioon and late Carnian to late middle Norian (late Triassic) age (OR073). A Lead-uranium age of 235 Ma for an intrusive tonalite in the Huntington Formation indicates that part of the unit is Middle Triassic or older (OR190). The unit is interpreted as a product of a Triassic volcanic arc that makes up the Olds Ferry terrane (OR089)..
Stratigraphic units Huntington Formation (OR073)
References

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

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.

https://pubs.er.usgs.gov/publication/i1116

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

Brooks, H.C., 1979, Geologic map of the Huntington and part of the Olds Ferry quadrangles, Baker and Mlheur Counties, Oregon: Oregon Department of Geology and Mineral Industries Geologic Map Series, GMS-13, scale 1:62,500.

Nolf, Bruce and Taubeneck, W.H., 1963, Permo-Triassic stratigraphic revisions, Wallowa Mountains, northeastern Oregon [abs.]: Geological Society of America Special Paper 73, p. 92-93.

Swisher, C.C., Ach, J.A., and Hart, W.K., 1990, Laser fusion 40Ar/39Ar dating of the type Steens Mountain Basalt, southeastern Oregon, and the age of the Steens aeromagnetic polarity transition [abs.]: EOS, Transactions of American Geophysical Union, v. 17, no. 43, p. 1,296.

Beeson, J.H., Geology of the southern half of the Huntington quadrangle, Oregon: Eugene, University of Oregon, master's thesis, 77 p.

Berry, N.J., 1956, Geology of the northeast quarter of the Huntington quadrangle, Oregon: Eugene, University of Oregon, master's thesis, 78 p.

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.

https://pubs.er.usgs.gov/publication/b1385E

NGMDB product
Counties Baker - Grant - Malheur - Union - Wallowa