Geologic Unit: Frontier

Usage:

Frontier Formation (CO,ID*,MT*,UT*,WY*)
Frontier Sandstone (UT*,WY*)
Frontier Formation of Mancos Group (CO*,UT*)
Frontier Formation of Colorado Group (MT*,WY)

Subunits:

(alphabetical): Allen Hollow Shale Member (UT,WY), Belle Fourche Member (WY*) or Belle Fourche Shale Member (MT), Big Elk Sandstone Member (MT), Boulder River Sandstone Member (MT*), Chalk Creek Member (UT,WY), Coalville Member (UT,WY), /Dry Hollow Member (UT,WY), Emigrant Gap Member (WY), Grass Creek Member (UT), /Grass Valley Shale Member (UT), Judd Shale Member (UT), Longwall Sandstone Member (UT), /Meadow Creek Sandstone Member (UT), Oyster Ridge Sandstone Member (UT*,WY*), Peay Sandstone Member (MT*,WY*), Skunk Point Sandstone Member (UT), Soap Creek Bentonite Bed (MT*,WY*), /Spring Canyon Member (UT), Torchlight Sandstone Member (MT*,WY*), Tununk Shale Member (CO*,UT*), Upton Sandstone Member (UT), Wall Creek Sandstone Member (WY*).

Geologic age:

Late Cretaceous (Cenomanian to Turonian)*; locally late Early Cretaceous (Albian)*

Type section, locality, area and/or origin of name:

Type area: in northern half secs. 31 and 32, T. 19 N., R. 116 W., Lincoln Co., WY (Cobban and Reeside, 1952).
Reference section: on north side of Canyon Mountain, [just southwest of Livingston], in secs. 26 and 27, T. 2 S., R. 9 E., [in vicinity of Lat. 45 deg. 37 min. 37 sec. N., Long. 110 deg. 35 min. 30 sec. W., Livingston 7.5-min quadrangle], Park Co., MT (Roberts, 1972).
Named from exposures near Frontier, 2 mi north of Kemmerer, Lincoln Co., WY. Characteristically exposed at Cumberland Gap, 15 mi south of Frontier.

AAPG geologic province:

Bighorn basin*
Central Montana uplift*
Central Western Overthrust*
Green River basin*
Montana folded belt*
Piceance basin*
Powder River basin*
Snake River basin*
Uinta basin*
Wasatch uplift*
Wind River basin*
Yellowstone province*