GM-71—Geology of Trampas quadrangle, Picuris Mountains, Taos and Rio Arriba Counties, New Mexico

By P. W. Bauer and M. A. Helper, 1994, lat 36°07'30" to 36°15', long 105°45' to 105°52'30", 2 sheets with text, scale 1:24,000.

The Harding pegmatite mine and Precambrian metasedimentary rocks of the Copper Hill mining district are two of the more interesting geologic features of the Trampas 7½-min quadrangle. The map area is located at the western-most point of the wedge-shaped, Precambrian-cored Picuris uplift, an isolated range that projects westward from the southern Sangre de Cristo Mountains 12.4 mi southwest of Taos. Two state highways traverse the map area. NM-68, the road from Española to Taos, crosses the northwest corner of the quadrangle parallel to the Rio Grande and Embudo fault zone. NM-75 runs east-west across the central part of the quadrangle. Early Proterozoic metamorphic rocks are exposed across most of the northern half of the quadrangle. To the west these rocks are blanketed by Neogene Santa Fe Group (Tesuque Formation) sedimentary rocks. Except for scattered outcrops of Proterozoic rock, the southern half of the quadrangle is covered by Tesuque Formation and Pliocene-Pleistocene surficial deposits. Precambrian and Cenozoic geology are broken down into 54 map units, each described in detail. Two cross sections illustrate local structural features.