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National Geologic Map Database

Geologic Unit: Aycross

Usage:

Aycross Formation of Thorofare Group of Absaroka Volcanic Supergroup (WY*-notably Absaroka Range)
Aycross Formation (WY*-notably Teton Range)


Geologic age:

early Tertiary (Eocene)*


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

Type area: north side of North Mesa [now Upper Table], about 1 mi southeast of A Cross Ranch, in secs. 7, 8, 17, and 18, T. 7 N., R. 5 W., Fremont Co., southern Absaroka Range, Wind River Indian Reservation, northwestern WY. Named from A Cross Ranch on East Fork River at Duncan (Love, 1939).


AAPG geologic province:

Bighorn basin*
Wind River basin*


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 ([ ]).