In the Rio Grande rift of southern New Mexico, the intrabasinal East Robledo fault in the Mesilla basin and the Jornada fault in the Jornada del Muerto basin experienced hundreds of meters to kilometers of offset during late Miocene to early Pliocene time and tens of meters of offset since middle Pleistocene. Late Pliocene and early Pleistocene activity on the faults is assessed by comparing sedimentological characteristics of the Camp Rice Formation, which is correlated by reversal magnetostratigraphy, on either side of the faults. The Jornada fault is interpreted to have been inactive from approximately 3.4 to 2.5 Ma, because Gauss-age fluvial strata at Rincon Arroyo, located on the hanging wall, have similar sediment accumulation rates, degree of development of calcic paleosols, and relative abundance of fluvial channel lithofacies as coeval footwall strata at Cedar Hill and Lucero Arroyo. In contrast, syndepositional movement on the Jornada fault along the northern flank of the Dona Ana Mountains from 2.5 to 0.7 Ma is suggested by a condensed Matuyama interval characterized by mature stage III and IV calcic paleosols at Lucero Arroyo. The northern segment of the East Robledo fault was active during Gauss time, based on an abundance of relatively thick (59 m), fluvial-channel deposits in the hanging-wall section at Northeast Robledo. The southern segment of the East Robledo fault, however, was probably not active during most of Gauss time, because of the presence on the footwall of a thick (50 m) section of fluvial strata of Gauss age at Picacho Mountain. Major movement on the East Robledo fault near the end of Gauss time terminated sedimentation at Picacho Mountain and in the Corralitos basin, abandoning the upper La Mesa geomorphic surface.

Tascotal Mesa fault is the principal component of Tascotal Mesa transfer zone within the Rio Grande rift of Texas (USA) and Chihuahua (Mexico). Strata and structures along the zone attest to ~290 m.y. of tectonic and magmatic activity, from at least late Paleozoic time onward. The transfer zone comprises the Tascotal Mesa and newly documented Christmas Mountains–Grapevine Hills faults, as well as the Terlingua Creek pull-apart complex at the right step between those two dextral zones. Strike-slip (to ~1 km) and dip-slip (to ~735 m) displacements have occurred in the zone during the past 30–27 m.y.; young faults of the transfer zone displace mid-Pleistocene caliches. Stable isotope and palynologic data from travertines in the transfer zone indicate ascent of warm waters (25°–35 °C) along faults as recently as mid- to late Pleistocene time. Older, basement-rooted structural anisotropies are present in the Tascotal Mesa transfer zone but not all have been reactivated during Cenozoic rifting. Geophysically constrained physical models integrated with field data demonstrate that the Terlingua Creek pull-apart basin likely formed in cover strata that were detached from basement, as the orientations of surficial and buried basement structures differ markedly. Dip-slip displacement predominates on pull-apart faults, with significant dextral slip. Analysis of the role of the Tascotal Mesa transfer zone in Rio Grande rifting revealed that it and the flanking grabens (Presidio to the northwest; Redford to the southeast) are all parts of the Border Corridor transform zone. This transform zone interconnects rift segments from Mesilla graben to the Sunken Block and includes both transfer zones and grabens. Right-transtensional deformation, as manifested in historic earthquakes, accounts for differing orientations of transform (northwest) versus rift (north) grabens. Petrographic and geochronologic data indicate ascent of lavas of rift geochemical character in both the Tascotal Mesa transfer zone and the Border Corridor transform zone from ca. 30 Ma onward. K-Ar ages were determined for basalt (24.73 ± 1.96 Ma) and trachyte (25.42 ± 0.64 Ma) emplaced within the Tascotal Mesa transfer zone. Magmatism is bimodal; olivine basalt and/or hawaiite predominates. Basalts at the junctions of rift grabens and the Border Corridor transform zone entrain mantle and lower-crustal xenoliths.