Structure, stratigraphy and petroleum potenetial of the El Vado area, Rio Arriba County, New Mexico
— William C. Beck and R. Bruce Hallett

The El Vado area is located in eastern Rio Arriba County, New Mexico, on the eastern margin of the San Juan Basin. Observed structures and interpretation of existing well logs within and in close proximity to the study area indicate that the area underwent structural deformation during ancestral Rocky Mountain, Laramide, and Rio Grande rift deformational events. Well log interpretation indicates that surface exposures of Cretaceous rocks are underlain by Mesozoic (Jurassic and Triassic) and late Paleozoic (Permian and Pennsylvanian) strata. Abrupt thickening of both Permian and Pennsylvanian strata from east to west indicates that this area overlies a significant late Paleozoic structural boundary that either marks or was proximal to the late Paleozoic Uncompahgre uplift. Observed structures in the study area include an anticlinal/synclinal fold pair and normal faults, thrust faults, and strike-slip faults. North-northweststrikin  thrust faults and strike-slip faults of varied strike direction are comparatively small-scale structures that are interpreted to have originated during Laramide deformation. In contrast, north-striking normal faults are comparatively large-scale, mappable structures that strike parallel to both the axial trend of the anticlinal/synclinal fold pair and the mid-Tertiary Dulce dike swarm. Accordingly, the normal faults and the fold pair are interpreted as structures that developed during Rio Grande rift tectonism. The development of anticlinal and synclinal flexures in an otherwise extensional setting, combined with subsurface stratigraphic data from well logs, indicates that the flexures overlie and mimic an underlying horst/graben topography of late Paleozoic origin. Historic oil and gas production in the area has occurred from shallow, fractured Cretaceous reservoirs; other potential may exist in Pennsylvanian and Jurassic reservoirs.