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.

Warford Ranch is a small “drive-in” shield volcano covering an area of ~2 by 3 km west of Phoenix, and it is accessible from Interstate Highway 8 near Gila Bend, Arizona. The basaltic shield is superposed on silicic lavas, granodiorites, and alluvial deposits and is part of the Sentinel-Arlington volcanic field. Dated at 3.19 Ma, the shield volcano is sufficiently young to preserve the original morphology, but it also shows the effects of moderate weathering, development of desert varnish, and the formation of caliche deposits. Imaged in both color near-infrared (IR) and in thermal infrared multispectral scanner (TIMS) data, these various units afford the opportunity to conduct simple remote-sensing mapping, which can then be field tested. In addition to the lava flows comprising the shield, pyroclastic deposits and dikes are also present. The compact size of the volcano enables the entire feature to be examined in the field in one day. With short introductory discussion, participants of nearly any background can be introduced to the fundamentals of remote sensing, igneous rocks, field methods, and evaluation of the volcanic history of a small volcano.

Coals in the post-Wapiabi strata of the Rocky Mountain Foothills are found in the upper Campanian (uppermost Belly River and lowermost St. Mary River formations), lower Maastrichtian (upper Brazeau Formation) and lower Paleocene (upper Coalspur Formation) stratigraphic sequences. Large-scale facies relationships within these sequences, combined with sedimentologic data for the coal-bearing strata and their correlatives, indicate that the coal-forming swamps originated in marginal marine, marginal lacustrine, and flood-plain enviornments. The coal-forming swamps developed only when there was a combination of appropriate diastrophic and favorable climatic conditions. This happened twice in the depositional history of the Rocky Mountain Foothills during phases of relative tectonic quiescence (early Maastrichtian and early Paleocene) in the northern, humid part of the basin. At those times the semiarid conditions in the southern part of the basin precluded the formation of coal-forming swamps. The semiarid conditions in this part of the basin were overridden in the late Campanian by the influence of the Bearpaw Sea, which led to the formation of thin coals in the marginal marine environment.