Basalt and silt; Late Pleistocene basalt flows and interlayered lacustrine silt beds of subunit 1b; Snake River Plain (IDQpu1b;0)

State	Idaho
Name	Basalt and silt; Late Pleistocene basalt flows and interlayered lacustrine silt beds of subunit 1b; Snake River Plain
Geologic age	Late Pleistocene
Original map label	Qpu1b
Comments	Formational names are mostly from measured sections of intra-canyon flows. Of larger areal distribution are coalescent unnamed low shields, tube flows, ponded flows, fissure flows, and small cinder cones.
Primary rock type	tholeiite
Secondary rock type	lava flow
Other rock types	silt
Lithologic constituents	Major Igneous > Volcanic > Mafic-volcanic > Basalt (Flow)tholeiitic pahoehoe flows, columnar jointing common Minor Unconsolidated > Fine-detrital > Silt (Bed)American Falls Lake beds
Map references	Bond, J.G., Kauffman, J.D., Miller, D.A., and Venkatakrishnan, Ramesh, 1978, Geologic map of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, with contributions from U.S. Geological Survey, scale 1:500,000.
Unit references	Bond, J.G., Kauffman, J.D., Miller, D.A., and Venkatakrishnan, Ramesh, 1978, Geologic map of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, with contributions from U.S. Geological Survey, scale 1:500,000. Malde, H.E. and Powers, H.A., 1962, Upper Cenozoic stratigraphy of western Snake River Plain, Idaho: Geological Society of America Bulletin, v. 73, no. 10, p. 1197-1220. Malde, H.E., 1982, The Yahoo Clay, a lacustrine unit impounded by the McKinney basalt in the Sanke River Canyon near Bliss, Idaho: in Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic Geology of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology Bulletin 26, p. 617-628. Rember, W.C., and Bennett, E.H., 1979, Geologic map of the Twin Falls quadrangle, Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, Geologic Map Series, Twin Falls 2o quadrangle, scale 1:250,000. Rember, W.C. and Bennett, Earl H., 1979, Geologic map of the Hailey quadrangle, Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, Geologic Map Series, Hailey 2o quadrangle, scale 1:250,000. Malde, H.E., 1971, History of the Snake River Canyon indicated by revised stratigraphy of Snake River Group near Hagerman and King Hill, Idaho: in Shorter Contributions to General Geology, 1969: U.S. Geological Survey Professional Paper 644-F, F1-F21. [http://pubs.er.usgs.gov/publication/pp644F] Scott, W.E., Pierce, K.L., Bradbury, J.P., and Forrester, R.M., 1982, Revised Quaternary stratigraphy and chronology in the American Falls area, southeastern Idaho: in Bonnachsen, Bill and Breckenridge, R.M., eds., Cenozoic Geology of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology Bulletin, no. 26, p. 581-595. Kuntz, M.A., Covington, H.R., and Schorr, L.J., 1992, An overview of basaltic volcanism of the eastern Snake River Plain, Idaho: in Link, P.K., Kuntz, M.A., and Platt, L.B., eds., Regional Geology of Eastern Idaho and Western Wyoming: Geological Society of America Memoir 179, p. 227-267. Armstrong, R.L., Leeman, W.P., and Malde, H.E., 1975, K-Ar dating, Quaternary and Neogene volcanic rocks of the Snake River Plain, Idaho: American Journal of Science, v. 275, p. 225-251. Mitchell, V.E., and Bennett, E.H., 1979, Geologic map of the Boise quadrangle, Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, Geologic Map Series, Boise 2o Quadrangle, scale 1:250,000. Greeley, Ronald, 1982, The style of basaltic volcanism in the eastern Snake River Plain, Idaho: in Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic Geology of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology Bulletin 26, p. 407-421 Leeman, W.P., 1982, Olivine tholeiitic basalts of the Snake River Plain, Idaho: in Bonnichsen, Bill, and Breckenridge, R.M., eds., Cenozoic Geology of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology Bulletin 26, p. 181-191.
Geographic coverage	Ada - Elmore - Gooding - Jerome - Lincoln - Twin Falls