UNDERGROUND WATERS. 67 
granite have been sunk on diabase dikes which cut that rock and 
some of which show considerable copper stain. Prospects in the 
arkose of the Casper formation likewise show much green stain, 
notably at one place on the King Solomon claim, in the NE. J sec. 15, 
T. 12 N., R. 73 W., near the contact of the Casper and the granite. 
A small amount of native copper also occurs here scattered through 
the arkose, but no lead of promising value has been struck. One of 
the large chunks of native copper was found near this place. Many 
pits have been sunk along the fault south of Tie Siding, but without 
encouraging results. 
UNDERGROUND WATERS. 
GENERAL CONDITIONS. 
The succession and structure of the rocks in the Laramie Basin are 
favorable for the occurrence of large supplies of underground waters 
obtainable by wells of various depths. There are water-bearing 
sandstones in the Casper, Cloverly, Benton, and Montana forma- 
tions; and water also occurs in the Chugwater red beds, Tertiary 
deposits, alluvium, and older terrace gravels. As shown in the sec- 
tions (PI. VIII), most of the sandstones are widely extended sheets 
of considerable thickness, interbedded with relatively impervious 
shales, a condition especially favorable for underground water stor- 
age. The sandstones mostly outcrop at high levels, and are carried 
by their dip toward the center of the basin under shales in areas of 
lower altitude so that the contained water has considerable head or 
pressure. Some of the sandstones, notably those of the Casper for- 
mation, lie very deep toward the center of the basin, but in this por- 
tion of the area water-bearing sandstones of higher horizons are within 
reach of borings of reasonable depth. The underground waters have 
not been extensively developed except in the vicinity of Laramie, 
where numerous flowing wells obtain supplies, mainly from sand- 
stones in the upper portions of the Casper formation. Most other 
portions of the region are supplied by surface waters or shallow wells 
obtaining water from the alluvium. The sandstone of the Cloverly 
formation, which is a most useful source of supply in other regions, 
has not been drawn upon to any great extent in the Laramie Basin, 
but a boring for oil near Hutton Lakes has shown that the forma- 
tion contains water which rises nearly to the surface. The sand- 
stone near the top of the Benton formation, although nol very 
thick, is porous and persistent, so that it may be confident lv expected 
to furnish water. The sandstones of the upper part of the Montana 
contain large amounts of water, which in some places in the lower 
lands is no doubt under sufficient pressure t<> afford Hows. These 
sandstones are the source of water in the artesian well at the Judson 
ranch on Dutton Creek and in others west of Laramie. 
