58 
The American Geologist. 
January, 1897 
Pierre <! 
Cretaceous -tj 
Niobrara -{ 
clear, concise, and complete. Its aim is to place in possession of the 
citizens of the region such knowledge of the geological formations and 
their relations to certain economic interests as will enable them to make 
them most available. 
The region is the larger portion of the twelve or thirteen southeast- 
ern counties of the state of Colorado. It briefly describes the various 
geological formations giving the physical appearances and characteristic 
fossils of each. The latter are illustrated so that well diggers and oth- 
ers may make use of them in identifying the strata which they find. A 
synopsis of the formations is given in the following table: 
Rock- Strata of Southeastern Colorado. 
I Fox Hills, sandstone and sandy shale 450 feet. 
Upper barren zone, shales 250-.300 " 
Teepee zone, shales 1,000 " 
Lucina occidentalis. Sea- 
phites vodosvN, Bacu- 
lites, Heteroceran, etc. 
Belemite zone, shales 100-150 " 
Belemnites, Bacidites,etc. 
Rusty zone, shales (JOO " 
Iron concretions. 
Lower barren zone, shales 450-500 " 
Much seleuite. 
Apishapa shales 500 •' 
Fish scales and bones. 
Timpas, limestone 175 " 
Inoceramus deforinia, Os- 
trea coiigesta. 
Carlile shales 
Prionocyclus u-yoniing- 
ensis. 
Greenhorn limestone 
Inoce ra in us la b iatus . 
Graneros shales 
I Dakota sandstones and shales 
Jura-Trias, sandstones and shales of i-ed color 
The dip of these formations, especially of the older, is to the north- 
northeast from the foot of the mountains. 
Besides these older formations of the Cretaceous there are recognized 
the Upland Sands and Gravels, which the author ascribes to the action 
of streams, lakes and winds, at a time when the drainage of the region 
was much more sluggish than at present; the Terrace Sands and Grav- 
els, which cap the higher terraces along the main streams, and the 
Dune Sands, which had accumulated at various epochs. 
Perhaps the most important economic feature of the paper is that 
treating of artesian wells. Water is a desideratum in that region and 
is obtained from two general sources: one, the deeper or artesian sup- 
ply, the other, the waters permeating the loose deposits near the sur- 
face. The artesian supply is here, as further north, mainly from the 
Dakota formation, which is described as being made up of different 
layers of a yellow or brown sand more or less separated by impervious 
layers of shale. The Jura-Trias is considered to be quite impervious to 
I 
Benton -<J 
175-200 
25-40 
200-210 
200-500 
2,000 
