Structural And Thermal Profile of the Southern Sangre De Cristo Arch Between Sante Fe and Las Vegas, New Mexico, Tests the Style of Late Cretaceous-Paleogene Laramide Faulting in The Southern Rocky Mountains
— Jacob O. Thacker

The style of strain accommodation on Late Cretaceous–Paleogene (Laramide) structures across the Colorado Plateau and
Rocky Mountains is a longstanding debate. Evidence for strike-slip faulting has led some to suggest region-scale dextral strain in/from
the Colorado Plateau, whereas others have found evidence for pervasive WSW–ENE horizontal shortening. In north-central New Mexico,
these provinces merge across the San Juan Basin (Colorado Plateau) to the Nacimiento and Sangre de Cristo arches (Rocky Mountains).
The Picuris-Pecos fault in the southern Sangre de Cristo arch exhibits evidence for strike-slip tectonism, but the timing of that tectonism
may precede Late Cretaceous horizontal shortening. This study examines the arch system between Santa Fe and Las Vegas, New Mexico,
to assess these opposing models. Two range-scale cross sections are presented to assess fault geometries and compiled apatite (U-Th)/He
and fission-track thermochronology from across the range allow for a critique of arch kinematics. An imbricate fan geometry is proposed,
whereby faults transition from steep reverse faults at the range crest to shallow thrusts at the range front. The resolution of thermochronology
data is limited but appears to support an east-stepping progression of exhumation. These interpretations are consistent with horizontal
shortening accommodated on an imbricate fan system that stepped eastward through time (in sequence). Thrusts are interpreted to root into
a mid- to upper-crustal detachment that is postulated to connect with the Nacimiento arch as a backthrust to this system.