Geologic Map of the Sedan Quadrangle, Gallatin And
U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY GEOLOGIC INVESTIGATIONS SERIES I–2634 Version 2.1 A 25 20 35 35 80 rocks generally fall in the range of 3.2–2.7 Ga. (James and Hedge, 1980; Mueller and others, 1985; Mogk and Henry, Pierce, K.L., and Morgan, L.A., 1992, The track of the Yellowstone hot spot—Volcanism, faulting, and uplift, in Link, 30 5 25 CORRELATION OF MAP UNITS 10 30 Kbc Billman Creek Formation—Grayish-red, grayish-green and gray, volcaniclastic mudstone and siltstone ၤ Phosphoria and Quadrant Formations; Amsden, Snowcrest Range and Madison Groups; and Three Overturned 45 20 10 30 20 P r 1988; Wooden and others, 1988; Mogk and others, 1992), although zircons have been dated as old as 3.96 Ga from P.K., Kuntz, M.A., and Platt, L.B., eds., Regional geology of eastern Idaho and western Wyoming: Geological 40 Ksms 45 Kh interbedded with minor volcanic sandstone and conglomerate and vitric tuff. Unit is chiefly 30 30 25 45 45 Forks Formation, Jefferson Dolomite, Maywood Formation, Snowy Range Formation, Pilgrim Ksl 5 15 50 SURFICIAL DEPOSITS quartzites in the Beartooth Mountains (Mueller and others, 1992). The metamorphic fabric of these basement rocks has Society of America Memoir 179, p. 1–53. 15 20 15 Kbc volcaniclastic mudstone and siltstone that are gray and green in lower 213 m and grayish red above; Estimated 40 Qc 5 15 Qoa Limestone, Park Shale, Meagher Limestone, Wolsey Shale, and Flathead Sandstone, undivided in some cases exerted a strong control on the geometry of subsequent Proterozoic and Phanerozoic structures, Piombino, Joseph, 1979, Depositional environments and petrology of the Fort Union Formation near Livingston, 15 25 Ksa 50 calcareous, containing common carbonaceous material and common yellowish-brown-weathering 60 40 20 15 15 (Permian, Pennsylvanian, Mississippian, Devonian, Ordovician, and Cambrian)—Limestone, Ksa 20 10 10 45 particularly Laramide folds (Miller and Lageson, 1993).
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