Region
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Mississippi
27
Maine
26
Minnesota
26
Europe
24
Jefferson County
23
Mexico, Gulf of
23
Ohio
23
Australia
22
China
22
Great Britain
22
Rocky Mountains
22
West Virginia
22
Brazil
21
Phosphoria Formation
21
Appalachian Mountains
20
Illinois
20
Sierra Nevada (Calif. and Nev.)
20
Appalachian Region
19
Colorado Plateau
19
Green River Formation
19
Vermont
19
Yellowstone National Park
18
California, Southern
17
Connecticut
17
Grand Canyon
17
Middle West
17
New Hampshire
17
San Juan County
17
Black Hills (S.D. and Wyo.)
15
Grant County
15
Iron County
15
Powder River Basin (Wyo. and Mont.)
15
South America
15
Atlantic Ocean
14
Louisiana
14
Minas Gerais
14
Northwest, Pacific
14
Pakistan
14
Rhode Island
14
San Juan Basin (N.M. and Colo.)
14
Antarctique
13
Arctic regions
13
England
13
Great Plains
13
North Dakota
13
North Slope
13
San Bernardino County
13
Uinta Basin (Utah and Colo.)
13
Appalachian Basin
12
Atlantic Coast
12
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