Integrating structural, stratigraphic, and thermochronologic datasets to test exhumation models for the Fra Cristobal Range in south-central New Mexico

Veronica Prush, New Mexico Institute of Mining and Technology
Kyle Gallant, New Mexico Bureau of Geology and Mineral Resources
Shari Kelley, New Mexico Bureau of Geology and Mineral Resources
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Abstract

South-central New Mexico has experienced multiple episodes of tectonic deformation during the Phanerozoic Eon, including Ouachita-Marathon (~320-260 Ma) and Laramide (~90-50 Ma) orogenesis and Rio Grande rift extension (~35 Ma – modern). Few studies have attempted to deconvolve the structural fabrics of each of these tectonic episodes. Here we present the first balanced and restored cross-sections in central New Mexico and demonstrate that Laramide tectonism drove much of the deformation currently observed in the Fra Cristobal Range. The thick-skinned deformation style that dominates in this range defies a straightforward cross-section model fit (e.g. fault-bend or fault-propagation folding), highlighting a need for cross-section model development in thick-skinned terranes.

Stratigraphic and structural datasets suggest that regional Miocene thermochronological dates are inconsistent with exhumation-related cooling hypotheses for the range's geologic evolution. We instead propose that regional hydrothermal activity reset low-temperature thermochronometers, likely during rapid Miocene Rio Grande rift extension. This study reaffirms the necessity of combining structural, stratigraphic, and thermochronologic datasets to test tectonic evolution hypotheses in terranes that have experienced multiple deformation episodes, such as southwestern North America.

Session

Deformation in the upper crust