GSA Today
Volume 31, Issue 3-4
The Pennsylvanian–Permian Minnelusa Formation (Minnelusa means “rapid water” in the Sioux
language) crops out in an area known to Rocky Mountain geologists as “The Amphitheater” near Beulah, Wyoming, USA,
and is one of the classic mapping areas for the Black Hills Natural Sciences Field Station. Situated between the
Williston, DJ, and Powder River basins, this >200-m-thick succession of interbedded sandstone, mudstone, lime-stone,
dolostone, and evaporite deposits is a key petroleum reservoir for the Rockies and is interpreted to represent an
ancient sabkha environment, similar to the modern sedimentary environments of coastal Abu Dhabi. Image courtesy of
H.F. Filkorn.
© The Geological Society of America, Inc.