138-13 Geochronological Calibration of Astrochronology or Astrochronological Calibration of Geochronology? A Revised Chicxulub Impact Age

Session: The Cretaceous-Paleogene (K-Pg) Boundary Interval: From Large-Scale Geological Events to Mass Extinction Mechanisms

Presenting Author:

Author:

Abstract:

Development of an astronomically calibrated time scale based on astronomical solutions (calculated planetary orbital parameters) has transformed the dating of geologic archives and today represents the backbone of cyclostratigraphy and astrochronology. Our recent astronomical solutions provide highly accurate chronologies and astronomical ages, often on par with, or preferred over, geochronological ages based on radiometric dating. Importantly, our objectives in this area reach beyond mere archiving and cataloging of Earth's history. Accurate absolute ages of, e.g., past climate-carbon cycle events relative to the timing of forcings such as volcanism, impacts, orbital forcing, etc. are critical to understand drivers and triggers of environmental changes and catastrophes. Here, I exemplify our methods using the Paleocene-Eocene boundary as a case study and present new insight into the end-Cretaceous Chicxulub impact age (often dubbed KTB age). In 2022, we provided new astronomical KTB ages based on five orbital solutions (labeled ZB18a and ZB20a-d). However, our recent work on an astronomically calibrated time scale for the Maastrichtian suggests that the solutions ZB20b-d are less favorable for older ages. The preferred solutions ZB18a and ZB20a then yield revised KTB ages of 65.92 to 65.96 Ma. These astronomical KTB ages are significantly younger than recent/widely cited 40Ar/39Ar ages of 66.043 +- 0.011/0.043 and 66.052 +- 0.008/0.043 (reported analytical/systematic uncertainty). To resolve the discrepancy, one may propose (A) a geochronological calibration of astrochronology or (B) an astrochronological calibration of geochronology. I will discuss the feasibility and merit of both proposals.

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

doi: 10.1130/abs/2025AM-8518

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