Region
California
13
Arizona
6
Salinas River Valley
4
Wyoming
4
North Carolina
3
Yellowstone National Park
3
Almería (Province)
2
Black Canyon (Ariz. and Nev.)
2
Chesapeake Group
2
Coso Range
2
Idaho
2
Middle Atlantic States
2
Mohave County
2
New Mexico
2
Santa Maria Basin
2
Santa Maria Basin (Calif.)
2
Sisquoc Formation (Calif.)
2
Spain
2
Virginia
2
Washington (State)
2
West (U.S.)
2
Alaska
1
Baja California (Peninsula)
1
Big Sandy Formation
1
Big Sandy Formation (Ariz.)
1
Chowan River Watershed
1
Colorado
1
Colorado Plateau
1
Glenns Ferry Formation (Idaho)
1
Great Plains
1
Hawaii
1
Kittitas County
1
Kittitas Valley
1
Lake County
1
Mexico
1
Mississippi
1
Norton Sound
1
San Bernardino County
1
San Diego
1
Teton County
1
United States
1
Ventura County
1
Yorktown Formation
1