New Mexico Geological Society
Fall Field Conference Guidebook – 75
Geology of the Eastern San Juan Basin

Kevin M. Hobbs, Allyson Mathis, Brittney Van Der Werff [editors]
2025, 283 pages.

Conference Organizers' message

Welcome to the 75^th Annual New Mexico Geological Society (NMGS) Fall Field Conference! This diamond anniversary marks a true homecoming for the Society—returning to the Cuba area and the eastern San Juan Basin, where the very first conference began back in 1950. That inaugural guidebook famously advised drivers to refuel at one of Cuba's eight (!) filling stations before venturing north toward Pagosa Springs, Colorado. Seventy-five years later, the landscape remains familiar, though the science of geology has evolved beyond what those early pioneers could have imagined.

Today, we explore the same mesas, cliffs, and canyons that inspired generations of New Mexican geologists. But this time, we do so equipped with the tools and insights born from decades of progress—from plate tectonics and radiometric dating to digital mapping and subsurface modeling. The journey from those early days of fieldwork to our modern understanding of geologic time is a story worth celebrating. The San Juan Basin's world-class stratigraphic section invites us to read deep into Earth's history, tracing changes in life, climate, and tectonics across hundreds of millions of years.

This year's conference builds directly upon the momentum of the 2024 Bernalillo FFC, which explored the "Nacimiento nexus"—where the Colorado Plateau, Rio Grande rift, and Rocky Mountains meet. Now, our focus shifts northwest to the basin's eastern margin near Cuba, where those same provinces continue to interact through space and time. The Rio Grande rift still beckons from the eastern horizon, reminding us that New Mexico's geology is never static. The 2025 FFC thus serves as both a continuation and a bridge: linking last year's discoveries with next year's Albuquerque-centered exploration of the Rio Grande rift.

Conference Chair Kevin M. Hobbs brings a deep connection to this region and a deep appreciation for its scientific legacy. The San Juan Basin has hosted numerous past FFCs—1950, 1951, 1977, 1992, 1997, and 2010—each producing guidebooks rich with insight and discovery. The 75^th guidebook continues that proud tradition, offering new perspectives built upon the solid foundation of those who came before. As Kevin reminds us, "If this year's guidebook can provide even a fraction of the utility of those preceding it, then it will be a success."

As we commemorate 75 years of exploration and education, let us honor the scientists whose curiosity shaped our understanding, and celebrate the next generation who will carry that legacy forward. The questions may change, but the spirit remains the same: to see the rocks, to ask why, and to learn what they reveal about our planet's story.

Here's to 75 years of New Mexico geology—and to many more discoveries ahead. For full access to this year's guidebook and past publications, visit https://nmgs.nmt.edu/publications/guidebooks/75.

Table of Contents:

Note —Downloads of the papers below are free. Road logs, mini-papers, and some other sections of recent guidebooks are only available in print.

Front Matter: (includes Dedication, President's Message, & Conference Organizer's Message)

Download (210.56 MB PDF)

Roadlogs: (each includes listed mini-papers)

Roadlog References:

Download (1.82 MB PDF)

Papers:

Back Matter: (usually includes a stratigraphic column and/or correlation chart)

Download (56.91 MB PDF)

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Recommended Guidebook Citation:

1. Hobbs, Kevin M.; Mathis, Allyson; Van Der Werff, Brittney;, 2025, Geology of the Eastern San Juan Basin -  Fall Field Conference 2025, New Mexico Geological Society, Guidebook, 75th Annual Field Conference, 227 pp. ISBN: 1-58546-121-0 https://doi.org/10.56577/FFC-75