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Glacial drift

Glacial drift: morainal and outwash plain deposits of mountain glaciers; mainly ill-sorted and poorly rounded boulders, cobbles, pebbles, and sand; may include alluvium in places
State Montana
Name Glacial drift
Geologic age Phanerozoic | Cenozoic | Quaternary
Primary rock type glacial drift
Secondary rock type alluvium
Other rock types
Lithologic constituents
Unconsolidated > Coarse-detrital (Glacial)Boulders, cobbles, and pebbles in mainly the morainal deposits
Unconsolidated > Fine-detrital (Glacial)Sand and silt mainly in outwash plain deposits
Unconsolidated (Alluvial)
Map references
Ross, P.R., Andrews, D.A., and Witkind, I.J., 1955, Geologic map of Montana: U.S. Geological Survey, 2 sheets, scale 1:500,000.
Unit references
Colton, R.B., 1962, Geology of the Otter Creek quadrangle, Montana, in Contributions to general geology, 1959: U.S. Geological Survey Bulletin 1111-G, p. G237-G288.
Counties Beaverhead - Deer Lodge - Flathead - Gallatin - Glacier - Granite - Jefferson - Lake - Lewis and Clark - Lincoln - Madison - Meagher - Mineral - Missoula - Park - Pondera - Powell - Ravalli - Sanders - Silver Bow - Sweet Grass - Teton - Wheatland