Eastern Sequence 
The Lakota outcrop along the eastern side of 
the Black Hills is poorly exposed. Much of the se- 
quence is of soft beds and these are generally covered. 
The best exposures are of local massive sandstone 
lenses scattered throughout the Lakota, and of the 
upper beds of the Lakota underlying the Fall River 
contact, 
♦ 
In the Sturgis area the Lakota as a whole appears 
to consist of five fairly distinct subunits listed below 
in a highly generalized section. 
Fall River formation Approximate thickness 
in feet, 
dis conformity 
Lakota formation 
5. Clay stone and silty clay stone, color - 
banded to variegated, some thin sand- 
stone lenses, and at least one local thick 
lens of massive sandstone occupying most 
of the interval, Siderite spherulites 
common in upper 5 to 12 feet, 40 - 75 
4. Siltstone, massive, clayey at top be- 
coming sandy downward and grading into 
a silty, commonly structureless, friable 
sandstone, white with purplish stain 
common. 
60 - 80 
