OF THE UPPER MISSOURI. 27 
base of the Black hills represents some local changes that occur in the Carboniferous, 
Dip of strata 20° south of east. 
Deep yellow limestone with fossils. 60 feet. 
Yellow argillaceous shale. 18 inches. 
Compact yellowish cherty rock. 4 feet. 
Light yellow argillaceous shale. 6 to 12 feet. 
Very compact limestone with cherty nodules. 8 feet. 
Alternate seams of yellow and drab arenaceous shale, tinged with red. 4 feet. 
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Carboniferous System. 
Reddish caleareous sandstone. 12 inches. 
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. Very tough argillaceous limestone passing down into soft friable sandstone or Potsdam sandstone. 2 feet. 
At another locality near the point where the last section was taken an upheaval shows 
the following beds: 
1. Alternate layers of yellow and dark brown arenaceous shale and sandstone with fossil wood. 50 to 60 feet. 
2. Whitish rather fine-grained sandstone. 15 feet. 
3. Reddish gritty marl passing down into a yellow shaly arenaceous marl. 50 feet. 
4. Yellow and yellowish gray sand and sandstone. 30 feet. 
5. Red grit with layers of concretionary sandstone. 30 feet. 
6. Layers of yellow arenaceous material, alternating with sandstone and shale. 40 feet. 
7. Red orit with layers of reddish sandstone, but comparatively little gypsum. 50 to 80 feet. 
Bed 1 belongs to Lower Cretaceous formation No. 1 of our general section; the others 
are undoubtedly Jurassic strata. 
Leaving our camp near the central ridge of upheaval of the Black hills, and taking a 
southeasterly course toward the Shyenne river, we pass over; first, metamorphic rocks ; 
second, Potsdam sandstone; third, a belt of Carboniferous rocks, about three miles in 
width ; fourth, a belt of Jurassic strata, about eight miles in width ; fifth, a complete series 
of the cretaceous formations ten to fifteen miles in width; and in the distance beyond the 
Shyenne the white clays and marls of the White river Tertiary basin could be seen. 
Passed over metamorphic rocks and Potsdam sandstone for the most part. The latter 
assumes an unusual conglomerate character, and the exceedingly comminuted condition of 
the organic remains, together with the irregularity of the lamina, indicates that this rock 
was deposited in shallow and turbulent water. 
Our route to-day led us over Jurassic beds chiefly. At one locality a yellowish blue 
arenaceous shale, below bed B of vertical section, contained layers of rock six to eighteen 
inches in thickness, composed of an aggregation of shells of the genera Ostrea, Belemnites, 
Avicula, and many undetermined species, the whole very much broken up. The entire 
thickness of this bed is eighty or ninety feet, with the greatest abundance of ‘organic 
remains distributed through it. 
