EXPLORATIONS ACROSS Til K i IKK AT BASIN OF UTAH. 



SECTION III. 



THE DISTRICT OF THE ROCKY MOUNTAINS. 



i. i:\KKAI. < OM[.,ri;ATI«»\ AM) (;KoL(m;U.'AL FORMATIONS- IGNEOUS ROCKS, ORANITKs, GRKKX- 

 ST< INKS-PERIOD OF THEIR KIJUI'TIoN - MKTAMoKCHK ' SCHISTS-STRATIFIED ROCKS OF THE 

 PALEOZOIC AGE-SILURIAN, DEVONIAN, CARBONIFEROUS, AND PERMIAN FORMATIONS-STRATA 

 OF DOUBTFUL ALL TKIASSIC AND JURASSIC FORMATIONS JURASSIC STRATA IN THE BLACK 

 HILLS AND ON PLATTE RIVER NEAR THE RED BUTTES-SEC I TON OF THE STRATA-THEIR 

 RELATION TO THE CRETACEOUS FORMATION NEAR LA BONTfl CREEK- SECTION OF THE TRI- 

 ASSIC ROOKS-TMKIR RELATION To THE JFRASSIC AND CARBONIFEROUS STRATA - EVII >EW| 

 OF THEIR TRIASSIC AGE-CRETACEOUS FORMATION-LIGNITE FORMATION-ITS LITHOLOGICAL 

 < HARACIER- IIS ACE — SAME FORMATION FARTHER SOUTH — TERTIARY FORMATIONS OF DIF- 

 FEREXT AGE -ECONOMICAL GEOLOGY -AGRICULTURE- BUILDING-MATERIALS -COAL, IRON, 



This .section comprises the country from the eastern foot of the Rocky Mountains 

 to the divide between the waters of the Atlantic and Pacific Oceans, from Fort Lara- 

 mie to the ►South Pass. The Pocky Mountains in this latitude do not form those com- 

 pact mountain masses, rising abruptly to a great altitude from a narrow base, and pre- 

 senting nearly insurmountable barriers, as they do farther south at the Parks; but they 

 have divided into various branches, trending mostly in a western or northwestern direc- 

 tion, and thus they have decreased in altitude and' flattened out. There are some con- 

 siderable elevations, such as the system of the Laramie Peak and the Wind River 

 Mountains, but most of the ranges, although generally presenting bare and rugged 

 dechvit.es, iorm only quite narrow spurs, which at numerous points fall off entirely, 

 and at others lose their rugged character, and only appear as gentle upheavals of the 

 stratified rocks, with broad, flattened crests. Between these ranges the country is 

 eomparatively level, and partly covered with nearly horizontal deposits, and even 

 \\ here it is rough and broken it can scarcely be called mountainous, and presents a sur- 

 face conjuration very different from what it is generally supposed to he in the region 



The mountains are partly covered with a thin growth of pine, but near the road 

 most of them are entirely bare of timber, or nearly so, and frequently they exhibit 

 lu — ,l r w j' lls iA - ra, | iro ,,r otl ^ 1 ' ,,,,( - ks - with scarcely a particle of soil or detritus upon 

 them. The Hat portion oi the country is an extensive sage-barren, but there is grass 

 11 ,m .- tho creeks, and more of it is scattered on the uplands between the sage. The 

 after grass is of a highly nutritious kind, which the animals like very much, even 

 when it is dry. 



Although the main emigrant-route to California and Oregon passes through this 

 section of country, little has hitherto been known of its highly interesting geological 

 features. Besides igneous rocks of different age and metamorphie strata, there" are 

 Mlunan and probably Devonian, Carboniferous, Cretaceous, and Tertiary formations- 

 and we have, moreover, found decidedly Jurassic strata, which seem to be developed 

 here over a considerable area. A short time ago the first indications of Jurassic for- 

 mations have been observed on an expedition under Lieutenant Warren, Topographical 

 Engineers, in the spur of the Black Hills north-northeast of Fort Laramie by Mi- 

 Meek and Dr. Hay den; and farther west, near the junction of the Wahsatch and Uintah 



