Region
Alaska
5
Colorado
4
Appalachian Basin
3
California
3
Louisiana
3
New Mexico
3
North Slope
3
Russia (Federation)
3
United States
3
Wyoming
3
Appalachian Mountains
2
Cuba
2
Gulf Coast (U.S.)
2
Montana
2
Piceance Creek Watershed
2
Powder River Basin (Wyo. and Mont.)
2
Siberia, Western
2
Afghanistan
1
Alaska Peninsula
1
Albuquerque Basin
1
Antarctica
1
Appalachian Region, Southern
1
Arkansas
1
Bangladesh
1
Barents Sea
1
Bears Paw Mountains Region
1
Belarus
1
Black Warrior Basin (Ala. and Miss.)
1
Book Cliffs (Utah and Colo.)
1
Caldwell Parish
1
Carbon County
1
Cotton Valley Region
1
Crazy Mountains Region
1
Dnieper-Donets Basin Province (Ukraine and Russia)
1
Eel River Watershed
1
Emery County
1
Florida
1
Great Basin
1
Green River Watershed (Wyo.-Utah)
1
Hanna Basin
1
Kansas
1
Maroon Formation (Colo.)
1
Mediterranean Sea
1
Mesaverde Group
1
Mexico
1
Middle West
1
National Petroleum Reserve
1
National Petroleum Reserve (Alaska)
1
Nebraska
1
Pripyat Basin
1
more ...