22 ON THE GEOLOGY AND NATURAL HISTORY 
In order that my remarks in regard to the Black hills may be more clearly understood, 
the following general vertical section of the different beds is given, showing their order of 
succession and approximate thickness. A more detailed survey would doubtless reveal facts 
which would modify it to some extent, but I believe that it will show the order of super- 
position of the different strata with sufficient accuracy and detail for our present purpose. 
General Section of the Geological Formations seen in and near the Black Hills (descending). 
1. Miocene beds consisting of whitish clays and sandstones of various thickness. 
No. 5. Of the Nebraska general section, with its usual characters and fossils. 150 feet. 
Presenting its usual characters and containing its characteristic fossils. 150 feet. 
Usual fossils and composition. 150 to 200 feet. 
Usual lithological characters and fossils with some new forms. 200 to 250 feet. 
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. Upper part yellowish and reddish sandstone, sometimes in heavy beds, passing down into alternations 
of yellowish, gray, bluish, and reddish laminated shale, with seams and layers of dark carbonaceous 
matter, or impure lignite ; beneath which there is a heavy bed of compact yellowish and reddish sand- 
stone, with indistinct vegetable remains, and much fossil wood. Above beds variable at different 
places. 300 to 400 feet. 
A. Then come alternations of light gray argillaceous grit and soft sandstone, containing Ammonites Henryi, 
Cretaceous System 
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and a small oyster; also in bluish gray compact argillo-caleareous masses, Unio nucalis, and a small 
| Planorbis, with other small univalyes like Paludina. Layers of argillo-calcareous, somewhat gritty 
mass, containing Belemnites densus, Ammonites cordiformis, Avicula (Monotis) tenuicostata, Arca 
(Cucullea) inornata, passing down into a 6 or 8 foot bed light gray or yellowish sandstone, with 
8 ripple-marks and trails of marine worms. 50 to 80 feet. 
a B. Licht red argillo-calcareous bed, with greenish seams and nodules (sometimes wanting). 380 to 40 feet. 
ae 4 (©. Soft gray and dark brownish sandstone passing down into about 8 feet of laminated shale of various 
g | colors, below which there is a 6 foot bed of sandstone similar to that above, containing Av/cula tenwi- 
2 costata and trails of marine worms. Then comes 30 to 40 feet of bluish or ash-colored argillaceous 
| shale, with great numbers of Linyula brevirostra and Serpula. Next we have a light gray calcareous 
| erit, containing columns of Pentacrinus asteriscus, Avicula tenuicostata, Serpula, &ec., the more com- 
pact and calcareous portions often perforated by Pholas? the latter bed passes down into a light, yel- 
| lowish gray sandstone, splitting into thin layers, and containing imperfect casts of Mytilus (Modivola), 
KL Pecten, Trigonia, and other bivalves in considerable numbers. Whole 60 to 100 feet. 
a D. Brick-red, incoherent, argillo-caleareous, very fine, slightly gritty material containing great quantities of 
ras | gypsum in the form of seams, layers, and irregular beds. 100 to 150 feet. 
g E. Bluish and reddish gray, very hard, gritty limestone, in which were found a smooth spirifer like S. 
S 4 linecatus, two or three species of small Pleurotomaria, two species of Mucrocheilus, and one or two 
5 | species of Bellerophon. This bed is variable in thickness. 10 to 50 feet. 
a F. Brick-red material, very similar to the bed D, excepting that it contains much less gypsum ; passing 
se | down into a very hard compact coneretionary sandstone. 250 to 300 feet. 
( G. Hard, more or less gritty, yellowish and whitish limestone, containing Productus, Spirifer, Huomphalus, 
e | &c., &e., passing down into a light yellow calcareous grit. Altogether 50 feet. . 
‘2 4 Hi. Very hard reddish gray limestone, containing Syringopora, Productus, Terebratula, &c. In the middle 
= | of this bed there is an 8 foot layer of very hard compact bluish limestone filled with comminuted 
oO | crinoidal remains. 50 fect. 
