Region
Colorado
21
United States
13
Wyoming
12
Fruitland Formation (Colo. and N.M.)
6
Powder River Basin (Wyo. and Mont.)
6
Alaska
5
San Juan Basin (N.M. and Colo.)
5
Rocky Mountains
4
Carbon County
3
Pennsylvania
3
Archuleta County
2
Campbell County Region
2
Haskell County
2
Hungary
2
India
2
Le Flore County
2
Louisiana
2
Oklahoma
2
Sand Wash Basin (Colo. and Wyo.)
2
Utah
2
Wainwright
2
West Virginia
2
Alabama
1
Alaska, Southcentral
1
Appalachian Region
1
Appalachian Region, Southern
1
Black Warrior Basin (Ala. and Miss.)
1
Botswana
1
Caldwell Parish
1
Campbell County
1
China
1
Claiborne Group
1
Cook Inlet
1
Forest City Basin
1
Fort Worth Basin
1
Galena
1
Huerfano County
1
La Plata County
1
Las Animas County
1
Lesotho
1
Mancos Shale
1
Mesaverde Group
1
Midland Basin (Tex. and N.M.)
1
Montana
1
North Dakota
1
North Slope
1
Oak Grove Region
1
Pakistan
1
Philippines
1
Powder River Watershed (Wyo. and Mont.)
1
more ...