GM-74—Geology of Caballo and Apache Gap quadrangles, Sierra County, New Mexico

By W. R. Seager and G. H. Mack, 2005, scale 1:24,000.

The Caballo and Apache Gap quadrangles span an area from the Jornada del Muerto and eastern piedmont slopes of the central Caballo Mountains westward across the Caballo Reservoir and I–25 into basin-fill alluvium and piedmont-slope deposits of the Palomas Formation (distal parts of Black Range alluvial fans west of the Rio Grande and ancestral Rio Grande fluvial deposits). Fifty-nine map units range in age from Proterozoic metamorphic and plutonic rocks to Holocene alluvial and fluvial deposits.

The Caballo Mountains contain the most complete stratigraphic sequence in southern New Mexico. Except for the Triassic and Jurassic, every period of the Phanerozoic is represented. Major Laramide compressional and late Tertiary extensional structures are well exposed.

This map is part of a larger study of the Caballo Mountains that includes providing complete map coverage at a scale of 1:24,000; six maps have been published. As a supplement to the quadrangle maps, Memoir 49, Geology of the Caballo Mountains, New Mexico, was released in 2003.

Available on CD-ROM only. $15.00