Geologic Unit: Mesa Falls

Usage:

Mesa Falls Tuff of Yellowstone Group (ID*,MT*)
Mesa Falls ash (informal) (NE*,WY*)
Mesa Falls ash is downwind equivalent of Mesa Falls Tuff (previously called Pearlette type S ash bed).

For informal usage, the rank or lithologic term should not be capitalized.

Geologic age:

Quaternary (Pleistocene)*

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

Named from Upper Mesa Falls on Henrys Fork of Snake River, Island Park area [in W/2 SW/4 sec. 13, T. 10 N., R. 43 E., approx. Lat. 40 deg. 11 min. 24 sec. N., Long. 111 deg. 19 min. 48 sec. W., Snake River Butte 7.5-min quadrangle, Targhee National Forest, Fremont Co., eastern ID] (Christiansen and Blank, 1972).
Type section: roadcut on U.S. Highway 20, about 6.8 km north of Ashton, [Lookout Butte 7.5-min quadrangle], Fremont Co., eastern ID (Christiansen and Blank, 1972).
Principal reference section: cliffs along gorge of Henrys Fork at Upper Mesa (Christiansen and Blank, 1972).

AAPG geologic province:

Central Western Overthrust*
Green River basin*
Idaho Mountains province*
Montana folded belt*
Paradox basin*
Salina basin*
Snake River basin*
Yellowstone province*