Black Hills Stratigraphy

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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Era	Formation			Picture	Notes
Tertiary	Medicine Root Gravels		0-2 m
	Sharps		30 m		Forms the tips of the highest Badlands pinnacles
	Rockyford Ash		2-4 m		A thin ledge-forming unit just below the tops of the pinnacles.
	Brule		100 m		Makes up most of the Badlands cliffs. Often banded white and pink.
	Chadron		15-20 m		From top to bottom: gray Chadron Formation, red Interior Paleosol, yellow Yellow Mounds Paleosol, and yellow-gray Fox Hills Formation. The paleosols are not really a formation, but truncate a number of formations.
	Interior Paleosol		1-2 m
	Chamberlain Pass		0-4 m
	Yellow Mounds Paleosol		2-5 m
Upper Cretaceous	Fox Hills		6-60 m
	Pierre Shale		200 m +		God must have been in a gray mood when he made this stuff and covered half of South Dakota with it.
Upper Cretaceous	Niobrara Formation		80 m
Upper Cretaceous	Carlile Shale		150 m
Upper Cretaceous	Greenhorn Formation	Upper Limestone	20 m
		Lower Shale	60-80 m
Upper Cretaceous	Belle Fourche Shale		100 m
Lower Cretaceous	Mowry Shale		40 m
Lower Cretaceous	Newcastle Sandstone		10 m
Lower Cretaceous	Skull Creek Shale		60-80 m		Dull gray shale with gypsum. Not the white nodular masses of the Spearfish but transparent blades, best seen by sun glint.
Lower Cretaceous	Fall River Formation		40 m
Lower Cretaceous	Lakota Formation		70-110 m
Upper Jurassic	Morrison Formation		0-30 m		The Western Interior Jurassic formation.
Upper Jurassic	Unkpapa Sandstone		15-40 m		Not typical Unkpapa but striking. This purple and yellow striped facies is found in a small area not publicly accessible.
Upper Jurassic	Sundance Formation		25 m		Consists of a variety of sandstone and limestone members.
	Unconformity
Permian	Spearfish Formation				The Spearfish and Opeche Formations are all but indistinguishable, except that the Spearfish has abundant gypsum.
Permian	Minnekahta Limestone				Pink, fine-bedded
Permian	Opeche Formation				The Opeche can be told from the very similar Spearfish Formation by its lack of gypsum.
Pennsylvanian-Permian	Minnelusa Formation				Gray but stained orange by the overlying formations.
	Unconformity
Lower Mississippian	Pahasapa Limestone				This is the cave-forming unit in the Black Hills. Called Madison Limestone elsewhere and in older literature.
Upper Devonian - Lower Mississippian	Englewood Limestone				This photo nicely shows the two-toned nature of the Englewood: pink below, buff above.
	Unconformity
Cambrian	Deadwood Formation
	Unconformity				Here 500 m.y. Deadwood Sandstone rests on 1.7 b.y. old schist. One quarter of the age of the earth is missing here.

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Created 7 April 2003, Last Update 10 January 2006

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