OF-04-09 Geologic Map of the Vallecito Reservoir Quadrangle, La Plata County, Colorado


Describes the geologic setting and mineral resource potential of this 7.5 minute quadrangle in southwest Colorado. 1:24,000, includes oblique view, booklet, correlation of map units, cross sections, geologic map and shapefiles w/ metadata. (1:24,000). Digital ZIP/PDF download. OF-04-09D

From the Author’s Notes:

The Vallecito Reservoir 7.5-minute quadrangle includes about 60 square miles of chiefly mountainous terrain within the northeastern part of La Plata County in southwestern Colorado. The west and east boundaries of the quadrangle lie at longitudes of 107° 37’ 30” W and 107° 30’ 00” W, respectively. The south margin of the map is at latitude 37° 22’ 30” N and the north margin is at latitude 37° 30’ 00” N. The southern margin of the quadrangle lies about 25 miles northeast of the town of Durango, and about 12 miles north of Bayfield. The quadrangle lies near the transition of the east-central part of the Colorado Plateau physiographic province and western edge of the Southern Rocky Mountains. The terrain in the mapping area varies from an elevation of about 7,500 ft above sea level along the shores of Vallecito Reservoir to the rugged surrounding mountainous terrain, where the elevation is more than 11,600 ft above sea level. Vallecito Creek drains much of the southeastern Needle Mountains, and flows across the quadrangle along a north and south line into Vallecito Reservoir. Nearly 5,000 ft of rock record that spans about 2 billion years of geologic time is exposed in the quadrangle.