Page 20 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

GENERAL FEATURES 19
cello ; Rio Cuchillo, which heads in the Black Range north and west of Chloride and Fairview ; Palomas River and Arroyo Seco originating near Hermosa ; Animas Creek, Rio Percha, and Tierra Blanca Creek, which drain the area north and south of Kingston and Hillsboro ; and Berenda Creek, heading • west of Lake Valley. Most of the streams are fed by permanent springs along their upper courses on the slopes of the Black Range. These waters flow at the surface for varying distances but eventually sink into the sand and gravel. The underground flow can usually be tapped at a moderate depth below surface as the streams approach the Rio Grande. During times of heavy pre- cipitation vigorous sheet and stream erosion occurs.
MOUNTAINS
The general trend of the mountain ranges is north and south. East of the Rio Grande, the Fra Cristobal and Caballos ranges, 20 and 27 miles long respectively, make a practically continuous range of mountains from the north bcundary of the county to its southern boundary. Just west of Hot Springs are the Mud Springs Mountains, about 6 miles in length. The San
although mainly in Socorro County, have their
Mateo Mountains
southern termination about 10 miles within the northern boun- dary of Sierra County. In the western part of the county a series of block-faulted ranges begins near the north boundary northeast of Fairview and extends southward to Hillsboro and beyond to Lake Valley. In this series are included the Sierra Cuchillo, Animas Hills, and Lake Valley Hills. Still farther west, on a due north-south line through Chloride, Hermosa and King- ston, is the eastern escarpment of the Black Range. These moun- tains form a part of the Continental Divide. They extend be- yond the county to the north and south and have a total length of nearly 100 miles. Among the highest peaks are Lookout Mountain and Hagen's Peak near Chloride, Diamond and Reed's peaks near Hermosa, and Hillsboro and Sawyer's peaks near Kingston. The elevatiohs of these peaks range from 9,000 to 10,100 feet. The south end of the range and also the entire range have been called the Mimbres Range in a number of official pub- lications, but these mountains are called the Black Range throughout this report.
In general, three types of mountain structure are repre- sented in the region, and according to Gordon3 they may be classed as :
(1) The tilted mountain whose primary feature is due to the displace- ment of a crustal block; (2) that due to the upthrust of a granitic core; and (3) that resulting from the accumulation of volcanic material. The first two are usually modified by igneous activity resulting in extensive accumulations of volcanic products and by intrusions. The modifications
3Lindgren, Waldemar, Graton, L. C. and Gordon, C. H., The ore deposits of New Mexico: U. S. Geol. Survey Prof. Paper 65, p. 220. 1910.
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