Geology of Northeastern New Mexico, union and Colfax Counties, New Mexico: A Geologic Summary
— Kate E. Zeigler, Frank C. Ramos, and Matthew J. Zimmerer

The geology of northeastern New Mexico is largely characterized by Triassic to Pliocene sedimentary strata that are commonly intruded and/or covered by upper Oligocene to Pleistocene volcanic rocks. The area is within the tectonically stable Great Plains province, a region characterized by thick crust and mantle lithosphere. The Raton-Clayton volcanic field of northeastern New Mexico is the northeastern-most expression of the Jemez lineament, a series of volcanic fields that extends from Springerville, Arizona to northeastern New Mexico. Overall, a southwest to northeast structural fabric characterizes the upper crust in northeastern New Mexico with many volcanic vents aligned along faults related to these features. Thick sedimentary stratigraphic sequences underlie most of the region with continuous exposures present in the valley of the Dry Cimarron River along the New Mexico/Colorado border and along mesa fronts in Colfax County. These thick sequences unconformably overlie Precambrian granitic and metamorphic rocks at depth. The land surface in this area is dominated by high mesas and low gently sloping valleys that are interrupted by smaller and lower elevation basalt-capped mesas, small intermediate to mafic volcanic cones, and the much larger edifice of the ~2-3 Ma Sierra Grande composite volcano. Human activities that impact the geomorphology and hydrology in the area include the many wagon ruts of the Santa Fe Trail (including the Cimarron Cut-off), the railroad system, open-range cattle ranching and some center-pivot irrigation farming.