STRATIGRAPHY. 
11 
A portion of the precipitation is snow, which falls in varying 
amounts but seldom lies long on the ground except on the higher 
mountain slopes. Hail falls occasionally and every few years does 
more or less damage to crops. 
GEOLOGY. 
STRATIGRAPHY. 
GENERAL RELATIONS. 
The Laramie Basin is a syncline lying between the uplifts of the 
Laramie Mountains on the east and the Medicine Bow Mountains and 
minor ranges on the west. Its depth is such that it contains about 
7,000 feet of Paleozoic and Mesozoic sedimentary rocks, from Car- 
boniferous to late Cretaceous in age, as well as extensive Tertiary 
and Quaternary deposits. In Plate VIII are given cross sections 
showing the general structural relations of the rocks. It will be seen 
that the sedimentary formations consist mainly of a series of thick 
sheets of sandstone, limestone, and shale, all essentially conformable in 
attitude, though lacking some systems of the geologic succession. 
At the base are pre-Cambrian granites, schists, and other rocks. - The 
stratigraphy presents much similarity to the general succession in 
the Rocky Mountains of Colorado and Wyoming, but it has numerous 
distinctive local features. The following is a list of the Mesozoic 
and older formations exhibited in the basin, with a general statement 
as to thickness, characteristics, and age: 
Generalized section of Mesozoic and older rocks in Laramie Basin, Wyoming. 
Formation. 
Character. 
A verage 
thickness. 
Age. 
Upper part: Sandstones and carbo- 
naceous shales with local coal de- 
posits. 
Lower part: Dark shales represent- 
ing the greater portion of the Pierre 
shale. 
Impure chalk rock and calcareous 
shale weathering to light-buff color. 
Gray shales, with hard shales and 
fine sandstone (Mo wry shale) near 
middle and buff sandstone near 
top. 
Coarse,Tnas3ive, buff sandstones sep- 
arated by gray to purple shales. 
Massive shales, greenish gray, buff, 
and maroon, with thin limestone 
layers. 
Soft sandstones overlain by greenish- 
gray shales. 
Red shales and soft sandstone, with 
gypsum deposits at and near base. 
Feet. 
1,280+ 
3, 000 
180 
560-1,300 
150 
115-200 
0-120 
1,200 
1-20 
0-240 
500-1, nn? I 
Upper Cretaceous. 
Do. 
Do. 
Niobrara 
Do. 
CI tv'crly 
Morrison 
Sundance 
Chug water 
Forelle 
rjpper(?) and Lower Creta- 
ceous. 
Lower Cretaceous (?). 
Late Jurassic. 
Triassic (?) and Carbonifer- 
ous (Permian). 
Carboniferous (Pennsylva- 
nian). 
Do. 
Satanka 
Red shale, with local gypsum 
White to purple limestones and dolo- 
mites and gray and white sand- 
stones, which to the south and 
west give place mostly to red and 
white, coarse sandstones. 
Crystalline rocks of various kinds 
penetrated by diabase and other 
dikes. 
Carboniferous ( IVimsyha- 
nlan-Mississippiar 1. 
Archean or Algonkian or 
both. 
< tranite, schists, etc. . . . 
