Structure of the Sangre de Cristo Mountains between Taos and Mora based on an integrated geophysical analysis

Abstract

A BSTRACT .- The southern Sangre de Cristo Mountains in New Mexico record much of the geological history of southwestern North America. Here we use a combination of geophysical data with geological ground truth to define the subsurface structure of part of this region. Our analysis indicates that a Proterozoic ductile fold and thrust belt exposed in the northern Rincon Range extends in the subsurface at least 25 km to the southwest of its surface expression. This fold and thrust belt likely links to similar fold and thrust structures exposed to the south and west in the Rio Mora, Truchas, Picuris and Tusas Mountains. Cross-cutting these structures, and offsetting the Great Unconformity, is a series of gently west dipping normal faults. These faults likely developed during Rio Grande rifting, although their gentle dips may be inherited from Laramide compressional structures. No structures related to Ancestral Rocky Mountains deformation were imaged in the subsurface. However, the distributions of Paleozoic rocks require that the Rainsville and Taos Troughs were major basins formed during Ancestral Rocky Mountain deformation. No evidence for the reactivation of Proterozoic structures was observed on the seismic data. Thus the structure of the southeastern Sangre de Cristo Mountains is the result of superposed deformation events that occurred in the Proterozoic, Late Paleozoic and the Cenozoic.