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Bighorn Dolomite, Gallatin Group, Gros Ventre Formation, Snowy Range Formation, Pilgrim Limestone, Park Shale, Meagher Limestone, Wolsey Shale, Flathead Sandstone, Whitewood Dolomite, and Winnipeg and Deadwood Formations (WYOCA;0)

Geologic Formation in WY, ID, MT

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Lithology

Siltstone

Sandstone

Other (2,228 mi²)

Geologic Age

Middle Cambrian – Late Ordovician (521 Ma – 445.3 Ma ago)

Geologic Unit Label

OCA

Bighorn Dolomite (Thrust Belt and North Wyoming) - Gray massive cliff-forming siliceous dolomite and locally dolomitic limestone. Bighorn Dolomite (Northern Yellowstone area) - Light-gray massive siliceous dolomite. Gallatin Limestone or Group (Thrust Belt) - Gray and tan limestone. Gallatin Limestone or Group (North Wyoming) - Blue-gray and yellow mottled hard dense limestone. Gallatin Group-Snowy Range Formation (Northern Yellowstone area) - Medium-gray limestone and underlying greenish-gray shale. Gallatin Group-Pilgrim Limestone (Northern Yellowstone area) - Blue-gray and yellow mottled hard limestone. Gros Ventre Formation (Thrust Belt) - Greenish-gray micaceous shale. Gros Ventre Formation (North Wyoming) - Soft green micaceous shale (Upper and Middle Cambrian Park Shale Member), underlain by blue-gray and yellow mottled hard dense limestone (Middle Cambrian Death Canyon Limestone Member), and soft green micaceous shale (Middle Cambrian Wolsey Shale Member). Park Shale (Northern Yellowstone area) - Green micaceous soft shale. Upper part may be Late Cambrian. Meagher Limestone (Northern Yellowstone area) - Blue-gray and yellow mottled hard limestone. Wolsey Shale (Northern Yellowstone area) - Green micaceous soft shale. Flathead Sandstone (Northern Yellowstone area and North Wyoming) - Dull-red quartzitic sandstone. Whitewood Dolomite (Northeast Wyoming) - Buff massive fossiliferous dolomite. Winnipeg Formation (Northeast Wyoming) - Pink to yellow siltstone and shale. Deadwood Formation (Northeast Wyoming) - Red and brown quartzitic sandstone.

— USGS

Taxonomy

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Geologic Formation