NATURAL SCIENCES OF PHILADELPHIA. 
43 
times far up on the higher points of the mountain, resting unconforraably upon 
the upturned edges of what appears to be a series of very ancient, highl}" meta- 
morphosed sedimentary strata, standing vertical. Beyond and beneath the lat- 
ter, the main body of the mountains seems to be made up of a coai se feldspathic 
granite, composed of large crystals of feldspar, with very small proportions of 
quartz and mica. This granite, and portions of the adjacent strata, were often 
seen traversed by various veins, dikes, and larger outbursts of basaltic and 
other eruptive rocks. 
In order that our remarks may be more clearly understood, we give below 
a general vertical section of the rocks seen in the Black Hills and around 
their base, showing their order of succession, and approximate thickness. It 
is not, of course pretended that all these formations were seen lying in con- 
tact at any one locality; but they were often met with, under such circum- 
stances, and holding such relations, as to leave little room to doubt that this is 
their true order of superposition. 
General Section of the Geological Formations seen in and near the Black Hills 
{descending). 
1st. Miocene beds consisting of whitish clays and sandstones of various thick- 
ness. 
f No. 5. Of the Nebraska general section, with its usual characters and fos- 
sils— 150ft. 
! No. 4. Presenting its usual characters and containing its characteristic 
fossils, — 150 feet. 
No. 3. Usual fossils and composition, — 150 to 200 ft. 
No. 2. Usual lithological characters and fossils, with some new forms, — 200 
to 250 ft. 
No. 1. 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 car- 
bonaceous matter, or impure lignite; beneath which there is a 
heavy bed of compact yellowish and reddish sandstone, with in- 
distinct vegetable remains, and ranch fossil wood, — above beds va- 
riable at different places, — 300 to 400 ft. 
Then come alternations of light gra,j argillaceous grit, and rather 
soft sandstone, containing Ammonites Henryi^ n. s. p., and a sjnall 
oyster ; also in bluish gray compact argillo-calcareous masses 
Unio nncalis n. s. p , and a small Planorbis, with other small 
L univalves like Paludina. 
f A. — Layers of argillo-calcareous, somewhat gritty mass, containing 
Belemnites densus, n. s. p., Ammonites cor diformis, n. s. p., Avicula 
{Monotis) tenuicostata^ n. s. p., Area {Cvcullcea) inornata, n. s. p. ; 
passing down into a G or 8 foot bed light gray, or yellowish sand- 
stone, with ripple marks and trails of marine worms, 50 to 80 ft. 
B. — Light red argillo-calcareous gritty bed, with greenish seams, and 
nodules (sometimes wanting,) — 30 to 40 ft. 
C. — Soft gray and dark brownish sandstone, passing down into about 
8 feet of laminated shale of various colors, below which there is a 
6 foot bed of sandstone similar to that above, containing Avicula 
tenuicostata^ and trails of marine worms. Then comes 30 to 40 
feet of bluish, or ash-colored argillaceous shale, with great num- 
bers of Lingula brevirostra^ n. s. p., and Serpula. Next we have 
a light-gray calcareous grit, containing columns of Pentacrinus 
asteriscus, n. s. p., Avicula tenuicostata, Serpula, kc, the more com 
pact and calcareous portions often perforated by Pholas ? The 
latter bed passes down into a light-yellowish gray sandstone, 
splitting into thin layers, and containing imperfect casts of 
Mytilus (Modiola), Pecten^ Trigonia, and other bivalves, in consider- 
able numbers. Whole 60 to 100 ft. 
1858.] 
