Geologic structure of the Velarde Graben and the southern Embudo fault system, north-central New Mexico
D. J. Koning, J. F. Ferguson, P. Jackson Paul, and W. S. Baldridge
The northeast-trending Embudo fault has a significant component of left-lateral slip and acts as a transfer fault in relaying extensional strain between the San Luis and Española Basins. In the northern Española Basin, the Embudo fault system links with the La Mesita and Dixon-Velarde faults of the northern Velarde graben, a 6-10 km-wide intra-rift graben. There is no evidence that a single scissors fault connects the down-to-the-northwest Embudo fault with the major down-to-the-east faults that bound the western side of the deepest parts of the central Española Basin (e.g., the Pajarito fault system). Rather, late Cenozoic slip associated with the Embudo fault appears to be partitioned amongst several major faults in the Velarde graben. In the southern Velarde graben, a lateral transfer of slip likely occurs between these faults and a major down-to-the-east fault called the Santa Clara fault. This transfer zone likely corresponds to an important fault segment boundary and is marked by transverse folds that may follow a transverse basement structure. Stratigraphic and seismic data indicate that substantial throw occurred along at least two major Velarde graben faults prior to the deposition of upper Miocene strata. This interpretation is consistent with a steepening of seismic reflectors with depth along the eastern margin of the Velarde graben. We speculate that the gravity high extending northwestward from the Picuris Mountains may correspond to a structural high related to the early development of the rift transfer zone between the Española and San Luis Basins. Subsequently, fault propagation and linkage may have formed a through-going Embudo fault system.
- Koning, D. J.; Ferguson, J. F.; Paul, P. Jackson; Baldridge, W. S., 2004, Geologic structure of the Velarde Graben and the southern Embudo fault system, north-central New Mexico, in: Geology of the Taos Region, Brister, Brian S.; Bauer, Paul W.; Read, AdamS.; Lueth, Virgil W., New Mexico Geological Society, Guidebook, 55th Field Conference, pp. 158-171.