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BASEMAPS
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WEATHER
Niobrara Formation (SDKn;0)
Geologic Formation
in
SD
,
WY
,
NE
,
ND
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Lithology
Chalk
Shale
Sand
Other
(4,876 mi²)
Geologic Age
Late Cretaceous (100.5 Ma – 66 Ma ago)
Geologic Unit Label
Kn
White to dark-gray argillaceous chalk, marl, and shale. Weathers yellow to orange. Contains thin, laterally continuous bentonite beds, chalky carbonaceous shale, minor sand, and small concretions. Thickness up to 150 ft (46 m).
—
USGS
Taxonomy
Classified As
Geologic Formation
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