38 IRON ORES OF IRON SPRINGS DISTRICT, UTAH. 
gravels. On the southwest end of. The Three Peaks laccolith the 
Pinto sandstone is in contact with the andesite in several places, 
but farther east it again appears in its normal place outside of the 
Homestake limestone, and continues until covered by the later clays. 
The formation borders the north* east, and south sides of the Home- 
stake limestone and the andesite of Granite Mountain, and a tongue 
extends northward into the desert. South and west of the Desert 
Mound there are also considerable exposures. Patches are exposed 
south and about three-fourths of a mile northwest of Iron Springs. 
In the southwest quarter of the district a belt of Pinto sandstone 
extends around the Iron Mountain laccolith, widening out to the west 
and southwest. A small area is found southwest of the Homestake 
mine, within the area of the Iron Mountain laccolith. North of Iron 
Mountain there are several small areas of sandstone exposed outside 
of the Claron limestone surrounding the Antelope Range lavas. A 
belt surrounds the Stoddard Mountain intrusive, which is just on the 
southern edge of the area mapped. 
CHARACTER. 
The Pinto formation is composed mainly of brown, yellow, gray, 
maroon, and spotted sandstone, both coarse and fine grained. Inter- 
stratified with these in the lower part of the formation are maroon, 
purple, and green shales, a few beds of conglomerate, and a few of 
gray, sandy, brecciated limestone. None of these interstratified beds 
are continuous throughout the area. In the Granite Mountain and 
Three Peaks areas the lower part of the Pinto formation has a char- 
acteristic succession, only a few members of which are present in the 
area about Iron Mountain. A generalized section for the first two 
areas is as follows: 
Generalized section of Pinto formation in Granite Mountain and Three Peaks areas. 
Feet. 
7. Yellowish brown and gray sandstone 1, 000+ 
6. Conglomerate with interbedded sandstone 20^40 
5. Variegated sandstone and shale 40-75 
4. Conglomerate 8 
3. Cherty limestone breccia 10-20 
2. Maroon and spotted sandstone 40-60 
1. Purple and green shale 30-50 
The shales (1) at the bottom, in contact with the Homestake lime- 
stone, are fairly continuous, being found throughout the northeast 
quarter of the district, and at one locality east of Iron Mountain, 
though here only the green shale is present. They are soft, sandy, and 
much fractured. 
The maroon and spotted sandstones (2) are abundantly exposed in 
the northeast quarter of the area, but appear locally at other points, 
