57-2 Intercalibrating Geochronometers Into the Future

Session: Advances and Applications in Geochronology for Interpreting Stratigraphic and Basin Records, Part II

Presenting Author:

Noah McLean

Authors:

Morgan, Leah¹, Carter, Jack², Fuentes, Anthony J³, Hasler, Caroline⁴, Jicha, Brian R.⁵, Keller, Brenhin⁶, McLean, Noah⁷, Renne, Paul R.⁸, Schmitz, Mark D.⁹, Schoene, Blair¹⁰, Sprain, Courtney Jean¹¹, Tholt, Andrew¹²

(1) USGS, Denver, CO, USA, (2) Berkeley Geochronology Center, Berkeley, CA, USA, (3) Earth & Planetary Science, UC Berkeley, Berkeley, CA, USA, (4) UC Berkeley, Berkeley, CA, USA, (5) University of Wisconsin-Madison, Middleton, WI, USA, (6) Dartmouth College, Hanover, NH, USA, (7) University of Kansas, Geology, Lawrence, KS, USA, (8) Berkeley Geochronology Center, Berkeley, CA, USA, (9) Boise State University, Boise, ID, USA, (10) Princeton University, Princeton, NJ, USA, (11) University of Florida, Gainesville, FL, USA, (12) UC Berkeley, Berkeley, CA, USA,

Abstract:

The intercalibration of geochronologic systems is vital for advancing geochronology in stratigraphic research. The ⁴⁰Ar/³⁹Ar and U-Pb dating methods are commonly employed, either in tandem or independently, to determine eruption and depositional ages. When utilizing multiple chronometers, as well as in contexts where absolute ages are crucial (e.g. geologic timescale calibration) the accurate calibration and intercalibration of these systems becomes especially paramount.

 

Recent work by Carter et al. (2025) used a Bayesian approach to calibrate the ⁴⁰K decay scheme and the ⁴⁰Ar*/⁴⁰K composition of Fish Canyon sanidine (FCs); the model relies on priors including decay constants for ⁴⁰K, ²³⁸U, and ²³⁵U, as well as a series of complementary ⁴⁰Ar/³⁹Ar and U-Pb datasets from geological samples (including offset parameters to account for various age-perturbing phenomena). This approach has been effective in enhancing the accuracy of the ⁴⁰Ar/³⁹Ar system and may similarly be employed to benefit the U-Pb system.

 

As we look to the future, this group of co-authors includes an advisory committee to explore further enhancements to the Bayesian model and to identify effective strategies for the ongoing refinement of geochronometer intercalibration. In upcoming iterations of the model, we plan to incorporate additional geological samples (young and old samples are particularly useful). We also aim to accommodate variable ²³⁸U/²³⁵U ratios and initial U-series disequilibrium in zircon U-Pb analyses. Furthermore, we are working on integrating a Bayesian approach to recognize and obviate pre-eruptive residence times of zircons and sanidines (Keller 2023). We are also considering the incorporation of other geochronometers (e.g. U-series and radiocarbon). We acknowledge the community's need for stability in parameter values while also emphasizing the importance of continually refining their accuracy, precision and intercalibration. We elicit suggestions from the geochronology community as we move forward with future updates to the Bayesian model.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7446

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.