STRATIGRAPHY. 17 
of the Casper formation in this vicinity. About 1§ miles north of 
east of the Willow Creek crossing a similar limestone caps the hill 
and is likewise underlain by coarse arkose containing concretionary 
limestone. This is the lowest limestone of the Casper formation in 
this vicinity, the interval to the granite below, 40 to 50 feet, being 
occupied by coarse arkose. 
A few sections near Colores, Wyo., are given below. 
Section of Casper formation in railway cut in SE. corner sec. /. '/'. 13 N., R. IS W., 
2\ miles south of Colores, Wyo. 
Feet. 
Fine-grained salmon-red cross-bedded sandstone 10 
Coarse arkose and conglomerate; limestone fragments at base 4 
Purplish sandy limestone 2 
Shales and sands below. 
Section of Casper formation 600 yards northwest of preceding section. 
Feet. 
Conglomerate 4 
Terra-cotta clay; pinches out in local unconformit y 1 
Arkose 4 
Cross-bedded red fine-grained sandstone 5 
Arkose, conglomeratic 5 
Sands and particolored clays 6 
Section of Casper formation at high hill 1 mile northwest of Colons. Wyo. 
Feel . 
Limestone. 5 
Fine-grained buff to salmon monumental sandstone 97 
Limestone (lumpy limestone of Gilmore Canyon forms bench here). . 13 
Terra-cotta sandstone, massive, coarse grained in places 45 
Reddish sandy shale and shaly sandstone 40 
In the ridges near the head of Sybille Creek the Casper formation 
varies considerably in thickness. In T. 19 N. the limestone is 250 
feet thick and is separated from the granite by 20 feet of pink sand- 
stone. Near the north side of the township a good section is shown 
in Plumbago Canyon. The Casper lies against the schists, which here 
constitute a band about 1,200 feet in width between the sediment a rv 
rocks and a broad area of coarse granite of a type similar to that 
occurring near Sherman station on the Union Pacific Railroad. The 
schists, mostly dark hornblendic rocks, strike N. 15° E. and dip 
nearly vertically to the west. Interlaminated are five beds of 
marble, three of which are 10 feet each in thickness and the other 
two 15 feet each. They are all highly crystalline and the eastern- 
most bed is very coarse grained. In the Casper the lowest bed of 
limestone dips parallel to the lamination of the schists, the second 
bed dips 55° W., the third 20° W., and the fourth and all above, 
10° W. It seems likely from the shattered character of the lowest 
58050 Bull. 364—09 2 
