12 Tectonics, Volcanism, and Sediment Dispersal Within and Proximal to the Rio Grande Rift and Southern Rocky Mountains

This session integrates research on coupled tectonics, volcanism, and sediment dispersal in the Rio Grande Rift and southern Rockies. We examine how extensional faulting controls volcanic processes and reshapes sediment routing from Colorado through Texas.

Monday, 18 May 2026
1:30 PM - 4:30 PM
Alvarado A

Resetting of Thermochronometers by High-temperature Fluid Flow in the Fra Cristobal Range, New Mexico

Paper number: 12-2
Program: Technical Sessions
Time: 1:55 PM – 2:15 PM

Authors

Abstract

Thermochronometric methods are commonly applied to study upper-crustal processes and have been very successful in dating tectonically driven exhumation over the past half-century. However, near-surface temperature fluxes, such as magmatic intrusion or high-temperature fluid flow, can partially or fully reset thermochronometers and may complicate interpretations of tectonic-related exhumation. Dates measured by thermochronometers often reflect a complex thermal record that does not correspond to a single thermal event. Therefore, distinguishing between tectonic exhumation and post-exhumation thermal fluxes recorded by thermochronometers is crucial for accurately reconstructing a region's tectonic history. Extensional settings provide an opportunity to decipher more complex thermal records since regional thinning and magmatism can perturb a more static thermal system. In this study, we use geologic mapping, cross-sectional analysis, structural measurements, and stratigraphic thickness plots in combination with previously published thermochronologic datasets to build a more robust thermal and tectonic history of the Fra Cristobal Range (FCR).

            In the FCR of south-central New Mexico, legacy maps and datasets laid the foundation for testing whether post-exhumation resetting of thermochronometers obscures the tectonic record. Previous thermochronology published in the region by Gavel et al. (2021) shows cooling at ~9-17 Ma in the FCR, which is temporally consistent with Rio Grande rift extension and magmatism. New and compiled geologic mapping at 1:10k further defined a known fossilized geothermal system, newly co-locating it with published thermochronology. We constructed a series of balanced and restored cross-sections that better resolve the kinematic history of the FCR. Published stratigraphic descriptions were used to construct a stratigraphic thickness plot, which helped determine a likely burial (i.e., thermal) history. HeFTy forward modeling, geologically constrained by collected and synthesized data, predicts a Laramide exhumation age (~35-75 Ma) for the FCR, which conflicts with the published thermochronology (~9-17 Ma). If a rapid high-temperature fluid pulse during the upper Miocene is included in our HeFTy models, the thermochronology dates are reconcilable with our proposed geologic history. We propose that focused geologic mapping and outcrop observations in thermally complex regions can help evaluate potential thermal records, constrain the thermo-kinematic history, and allow a more nuanced dissection of the integrated thermal history recorded by thermochronology. An updated geologic history of the FCR must include a high-temperature fluid flux event that partially reset the thermochronometers.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4

doi: 10.1130/abs/2026RM-410685

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