Named for Santa Rita, Grant Co, NM. Area of report is the Lake Valley district, Sierra Co, NM in Orogrande basin. No type locality designated. Is a dark, compact lime-rock about 10 ft thick that is exposed in shafts. Immediately overlies Ordovician El Pasan limestones (new); is overlain unconformably by Devonian Silver shales (new). The crevices, cracks, and uneven places in the surface are filled with a fine, bright red clay appearing at first glance like a peculiar reddish lime-rock. Is doubtless very much thicker elsewhere in the neighborhood; it is also absent entirely in other places, owing to the marked unconformity, due to erosion which exists between it and the later terranes. Is probably a remnant of the Silurian formations exposed a few mi to west and to southeast of Lake Valley, Sierra Co, in Orogrande basin. In vicinity of Santa Rita and Silver City, 30 mi west of Lake Valley, abundant fossils found in apparently the same terrane suggest typical Silurian forms. Still farther west, in eastern AZ, Reagan (1903) has discovered a similar lime-rock, 70 ft thick. Is of Silurian age. Cross sections, geologic section.

Source: GNU records (USGS DDS-6; Denver GNULEX).