Page 24 - Geologic Investigations in the Lake Valley Area, Sierra County, New Mexico

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EXPLANATION (A)
Lake Valley fault zone, synthetic fractures Slickenline, synthetic fractures
Antithetic fault
Slickenline, antithetic fault
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North end of Quartzite Ridge
South end of Quartzite Ridge
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EXPLANATION (B and C) Synthetic fracture
Slickenline
Figure 8. Lower hemisphere stereograms showing orientation of fractures and slickenlines in A, Lake Valley fault system (from Berrenda Mountain southeast) and parallel antithetic fault; B, southern splay of Berrenda fault zone; C, an east-trending fault at Quartzite Ridge.
The south splay of the Berrenda fault drops volcanic rocks down on the west about 300 m against Ordovician and Devonian rocks of Quartzite Ridge and ends where it abuts the southern segment of the Lake Valley fault system. It consists of several segments that range in trend from north to northeast and, where exposed, dip steeply west. Slickenlines (fig. 8B) reveal largely dip-slip motion.
East-Trending Faults North of Lake Valley Townsite
A system of closely spaced normal faults cuts Paleozoic rocks at and north of Lake Valley townsite. The closely spaced faults localize silver-manganese deposits at Lake Valley. Strati- graphic separation is small, and both down-to-the-north and -south separation is observed on individual faults. Although the
Geology of the Lake Valley Area 15