Geology of the Nacimiento Mountains and Rio Puerco Valley

About this guidebook

Conference Organizers’ message

The 2024 New Mexico Geological Society (NMGS) Fall Field Conference will be centered in Bernalillo, New Mexico. The history of this community, like much of New Mexico, is that of a nexus involving very long interactions among Indigenous, Hispano, Anglo, and other cultures. Our geoheritage gains strength from this unique cultural richness as well as our unique geology. We thank the Pueblos of Santa Ana, Zia, and Jemez, as this field conference studies geology across their present and traditional homelands. We recognize and honor them as original caretakers with deep connections to the land. Geology (study of the Earth) is also part of their Indigenous knowledge systems. Rivers are another theme of this field conference; the Rio Grande, Rio Jemez, and Rio Puerco have shaped our landscapes and host many of our stops and discussions.

We are trying new things for the 74th NMGS Fall Field Conference. The traditional minipapers are peer reviewed and folded in with the technical papers this year rather than included with the road log section. All the papers and road logs are open access and freely available on the NMGS website in PDF format during and after the meeting (https://nmgs.nmt.edu/publications/guidebooks/74). To save costs and paper, we are printing fewer hard copies of the full guidebook, mainly just for participants and libraries. Hold onto yours; it may be worth a fortune some day!

The geologic theme is the Nacimiento nexus. You know you are at a nexus when you find yourself in the middle of something. In this case, the Nacimiento nexus is where three major physiographic provinces meet: the Colorado Plateau, the Rocky Mountains, and the Rio Grande rift. Also converging at this crossroads are the northeast-trending Jemez lineament and the Jemez Mountains containing the Valles Caldera supervolcano. To examine the Nacimiento nexus requires a synthesis of the things that make the adjoining provinces similar and different (Karlstrom et al., 2024). The details can be complex but the summary is simple: the Rocky Mountains, Colorado Plateau, and Rio Grande rift share many aspects of a common geologic history of Proterozoic crust formation, regional Paleozoic and Mesozoic depositional systems that record the biological evolution of life on Earth, and a multistage Cenozoic uplift and denudation history that has shaped our landscapes. The spectacular region near San Ysidro lays bare aspects of each of these shared chapters of New Mexico's geology.

This scientific theme may carry momentum into future NMGS field conferences. Next year, the 2025 fall field conference – NMGS's 75th – will be centered in Cuba and will examine the Colorado Plateau edge and the San Juan Basin. The following year, the 2026 fall field conference (the 76th) will be centered in the Albuquerque area and will focus on the Rio Grande rift and rocks exposed in its rift-flanks.