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MAP

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WEATHER

Middle Tertiary sediment or sedimentary rock (MTTsm;0)

Geologic Formation in MT

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Lithology

Bentonite

Sandstone

Limestone

Other (1,630 mi²)

Geologic Age

Ypresian – Burdigalian (56 Ma – 15.97 Ma ago)

Geologic Unit Label

Tsm

Tuffaceous siltstone, sandstone, bentonitic mudstone, conglomerate, limestone, and equivalent sediment and ash beds. Local volcanic flows in southwestern Montana. Includes Renova Formation. Dominantly fluvial, floodplain, palustrine, lacustrine, debris flow, and eolian. Composite thickness for Tsu and Tsm exceeds 4,880 m (16,010 ft). Includes Anaconda Formation: Light gray, reddish tan, or brownish red, coarse breccia that laterally grades to conglomerate, sandstone, and siltstone. Locally intertongues with Lowland Creek Volcanics. Derived from overlying unmetamorphosed plate of metamorphic core complex. Thickness as much as much as 200 m (656 ft).

— USGS

Taxonomy

Classified As

Geologic Formation