Black Hills Stratigraphy

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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EraFormation  PictureNotes
TertiaryMedicine Root Gravels0-2 m   
Sharps30 m Forms the tips of the highest Badlands pinnacles
Rockyford Ash2-4 mA thin ledge-forming unit just below the tops of the pinnacles.
Brule100 mMakes up most of the Badlands cliffs. Often banded white and pink.
Chadron15-20 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 Paleosol1-2 m
Chamberlain Pass0-4 m
Yellow Mounds Paleosol2-5 m
Upper CretaceousFox Hills 6-60 m
Pierre Shale200 m + God must have been in a gray mood when he made this stuff and covered half of South Dakota with it.
Upper CretaceousNiobrara Formation 80 m  
Upper CretaceousCarlile Shale 150 m  
Upper Cretaceous Greenhorn FormationUpper Limestone20 m   
Lower Shale60-80 m
Upper CretaceousBelle Fourche Shale 100 m  
Lower CretaceousMowry Shale 40 m  
Lower CretaceousNewcastle Sandstone 10 m  
Lower CretaceousSkull 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 CretaceousFall River Formation 40 m That's lignite at the bottom.
Lower CretaceousLakota Formation 70-110 m  
Upper JurassicMorrison Formation 0-30 m The Western Interior Jurassic formation.
Upper JurassicUnkpapa 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 JurassicSundance Formation 25 m Consists of a variety of sandstone and limestone members.
PermianSpearfish Formation  The Spearfish and Opeche Formations are all but indistinguishable, except that the Spearfish has abundant gypsum.
PermianMinnekahta Limestone  Pink, fine-bedded
PermianOpeche Formation  The Opeche can be told from the very similar Spearfish Formation by its lack of gypsum.
Pennsylvanian-PermianMinnelusa Formation  Gray but stained orange by the overlying formations.
Lower MississippianPahasapa 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.
CambrianDeadwood Formation  Various shades of red but has glauconitic members near the base in places.
 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 24 July 2012

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