21 Frontiers in Geochronology: Advances and Applications in the Geosciences

This session highlights cutting-edge geochronologic advances and applications that illuminate Earth’s dynamic history. We welcome contributions spanning new analytical techniques, integrative studies, and innovative case examples demonstrating the essential role of time in geosciences.

Tuesday, 10 March 2026
10:00 AM - 12:00 PM
RCC, 104

When Mountains Fail: Detrital Zircons Reveal the Final 500 kyr Preceding One of Earth’s Largest Landslides

Paper number: 21-3
Program: Technical Sessions
Time: 10:45 AM – 11:00 AM

Authors

Abstract

Understanding the timing and speed of sedimentation relative to a major mass-wasting event allows us to understand the tectonic, volcanic, and surficial processes that preceded and led to this event. The Bear Valley Formation, a >2,500 km², up-to-300-m-thick succession of tuffaceous sandstone, tuff, conglomerate, and volcanic mudflow breccia in southwestern Utah, provides a unique record of late Oligocene sedimentation immediately preceding the Markagunt gravity slide, one of Earth’s largest known terrestrial landslides. We conducted U-Pb detrital zircon geochronology (LA-ICPMS; N = 3; n = 346) on autochthonous and allochthonous Bear Valley Formation samples to constrain sediment sources, depositional timing, and the preconditions leading to collapse. All samples exhibit dominant locally-sourced Oligocene zircon populations with maximum depositional ages of 24.0-23.6 Ma. A secondary peak at 29.4 Ma in one locality indicates incorporation of zircons from older regional ignimbrite sources. These data suggest that the uppermost Bear Valley Formation accumulated within a narrow ~400 kyr interval prior to catastrophic gravity slide emplacement at ~23 Ma. We interpret this brief depositional window to reflect rapid uplift and surface instability associated with local Marysvale volcanic field magmatism. This study highlights how high-density detrital zircon datasets can resolve short-lived sedimentary and tectonic events and offers a case study in linking geochronologic signals to large-scale structural failure in continental volcanic provinces.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411530

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