24 Tectonics, Volcanism, and Sediment Dispersal Within and Proximal to the Rio Grande Rift and Southern Rocky Mountains (Posters)

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.

Tuesday, 19 May 2026
8:00 AM - 5:30 PM
Alvarado D/E

Renewed Mapping of the San Ysidro Geologic Nexus

Paper number: 24-5
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Under a newly funded EDMAP Data Synthesis Project, we are working to produce a 1:24,000-scale digital geologic map of the San Ysidro Quadrangle in north-central New Mexico. This quadrangle is at the geologic nexusbetween the Colorado Plateau, Southern Rocky Mountains, and Rio Grande rift. This area was the focus of the New Mexico Geological Society 2024 Fall Field Conference, which highlighted the need for a new geologic map that incorporates new findings from various mapping efforts over the last five decades. Through this project, we are synthesizing 1930-1980s legacy mapping with new mapping, neotectonics, geochronology, and tectonic geomorphology studies. This mapping project is complementary with ongoing mapping of the New Mexico STATEMAP program and the USGS Earthquake Hazards Program. Results from this work will yield the first integrated surficial and bedrock geologic map at this scale for the iconic San Ysidro area since the 1976 Woodward and Reutschilling map. 

This mapping effort aims to answer questions about the extent and magnitude of Quaternary fault reactivation of Laramide and rift structures, leading to a new understanding of fault segmentation on the margins of the Colorado Plateau and Rio Grande rift. We employ studies of river incision rates across proposed faults, as recorded by terrace flights with timing constrained by new detrital sanidine and luminescence (IRSL) geochronology to estimate differential rates across major structures. The mapping uses recently updated stratigraphic nomenclature for Paleozoic and Mesozoic strata and advances in Proterozoic geochronology to update bedrock geology of the quad. 1m lidar and aerial digital mapping enhance map accuracy and rectify multiple generations of mapping within the area. Outreach involves renewed UNM/NMBGMR interaction with the Pueblos of Jemez and Zia whose ancestral lands are within this and adjoining quadrangles. Geo-cultural engagement is guided by the understanding of this area as an interwoven cultural and geologic nexus and complimentary with place-based education efforts at UNM. This map synthesis fills a timely gap at the nexusof the margins of the San Juan basin, Rio Grande rift, and Southern Rocky Mountains amid a new generation of research to understand the margins of the Colorado Plateau and rift. 

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

doi: 10.1130/abs/2026RM-410597

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