National Geologic Map Database

Geologic Unit: Flathead


Flathead Sandstone (ID*,MT*,WY*)
Flathead Quartzite (ID*,MT*,WY*)

Geologic age:

Middle Cambrian*

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

Named from exposures in Flathead Pass, northeastern corner Threeforks [Three Forks] quadrangle, MT (Peale, 1893).
Type section (emended): on Belt Creek, Little Belt Mountains, Cascade Co., MT. Incomplete section of Flathead measured from Archean contact, 40 to 50 ft above railroad track on spur 0.5 mi north of mouth of Hoover Creek and 5.25 mi S. 35 deg. E. of Monarch, in Belt Creek Valley, in NE/4 sec. 14, SW/4 sec. 13, N/2 sec. 24, and SE/4 sec. 25, T. 15 N., R. 7 E., near north edge of Little Belt Mountains. Weed gave locality of his Monarch (Belt Creek) section as "Section of beds exposed north of Belt Creek, 8 mi south of Monarch." Only Archean rocks, as indicated correctly on Weed's geological map, are present from 5.5 to 8 mi south of Monarch along Belt Creek (Deiss, 1936; see also Weed, 1900).

AAPG geologic province:

Bighorn basin
Central Montana uplift
Green River basin*
Montana folded belt*
Powder River basin*
Snake River basin*
Sweetgrass arch*
Wind River basin*
Yellowstone province*

For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name does not conform with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005). This may be explained within brackets ([ ]).