28 Aug 2023
 | 28 Aug 2023
Status: this preprint is currently under review for the journal GChron.

Bayesian Integration of Astrochronology and Radioisotope Geochronology

Robin B. Trayler, Stephen R. Meyers, Bradley B. Sageman, and Mark D. Schmitz

Abstract. Relating stratigraphic position to numerical time using age-depth models plays an important role in determining the rate and timing of geologic and environmental change throughout Earth history. Astrochronology uses the geologic record of astronomically derived oscillations in the rock record to measure the passage of time and has proven a valuable technique for developing age-depth models with high spatial-temporal resolution. However, in the absence of anchoring dates, many astrochronologies float in numerical time. Anchoring these chronologies relies on radioisotope geochronology (e.g., U-Pb, 40Ar/39Ar), which produce high-precision, randomly distributed point estimates of age.

In this study, we present a new R package, astroBayes for a Bayesian inversion of astrochronology and radioisotopic geochronology into age-depth models. Integrating both data types allows reduction in uncertainties related to interpolation between dated horizons, and the resolution of subtle changes in sedimentation rate, especially when compared to existing Bayesian models that use a stochastic random walk to approximate sedimentation variability. The astroBayes inversion also incorporates prior information about sedimentation rate, superposition, and the presence/ absence of major hiatuses. The resulting age-depth models preserve both the spatial resolution of floating astrochronologies, and the accuracy and precision of modern radioisotopic geochronology.

We test the astroBayes method using two synthetic data sets designed to mimic real-world stratigraphic sections. Model uncertainties are relatively constant with depth, and predominantly controlled by the precision of the radioisotopic dates and are significantly reduced relative to “dates-only” random walk models. Since the resulting age-depth models leverage both astrochronology and radioisotopic geochronology in a single statistical framework they can resolve ambiguities between the two chronometers. Finally, we present a case study of the Bridge Creek Limestone Member of the Greenhorn Formation where we refine the age of the Cenomanian-Turonian Boundary.

Robin B. Trayler et al.

Status: open (until 25 Oct 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gchron-2023-22', Maarten Blaauw, 27 Sep 2023 reply

Robin B. Trayler et al.

Robin B. Trayler et al.


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Short summary
Developing models that relate stratigraphic position to time are important because they allow the rock record to be understood in terms of absolute time, allowing global comparisons. In this study we developed a novel method for developing these models (called age-depth models) that uses two different types of chronologic information, dated rocks, and records of variations in earths orbit (astrochronology). The resulting models are very precise which can improve understanding of past climates.