Mining districts of northeastern New Mexico
— James M. Robertson

Northeastern New Mexico of this report comprises Colfax, Union, Mora, Harding, San Miguel, Quay and Guadalupe Counties (Fig. 1), and falls approximately between 34°30' and 36°00' N latitude and 103°00' and 105°45' W longitude.

The region includes parts of two major physiographic provinces: the Southern Rocky Mountains along its western border and the Great Plains. The Great Plains province in northeastern New Mexico can be further subdivided into the Raton section along the northern edge of the region, consisting of a deeply eroded peneplain surmounted by lava-capped plateaus and buttes, and the High Plains section in the central and south-eastern parts of the region, characterized by extensive, gently rolling, slightly dissected, high-level fluviatile plains.

 

The Sangre de Cristo Mountains are a continuation of the Front Range. They extend southward from the Colorado-New Mexico border approximately 90 miles, terminating in foothills just north of the Glorieta-Rowe Mesa. In the northern half of New Mexico, the Sangre de Cristos are subdivided into two parallel ranges, the Taos Range on the west and the Cimarron Range on the east, separated by the north-south trending Moreno Valley. The western border of Colfax County is roughly coincident with the western margin of Moreno Valley. The main body of the mountains swings to the southwest along the western border of Mora County and is called the Santa Fe Range. A lesser ridge continues southward through western Mora and San Miguel Counties and is called the East or Las Vegas Range. The area between these two ranges forms the drainage basin for the upper Pecos River.