Precession-driven climate cycles and time scale prior to the Hirnantian glacial maximum

Paleozoic astrochronologies are limited by uncertainties in past astronomical configurations and the availability of complete stratigraphic sections with precise, independent age control. We show it is possible to reconstruct a robust Paleozoic similar to 10(4) -yr-resolution astrochronology in the well-preserved and thick Upper Ordovician reference record of Anticosti Island (Canada). The clear imprint of astronomical cycles, including similar to 18 k.y. precession, potential obliquity, and short and long eccentricity, constrains the entire Vaureal Formation (similar to 1 km thick) to only similar to 3 m.y. in total, representing similar to 10 times higher accumulation rates than previously suggested. This similar to 10(4) yr resolution represents an order of magnitude increase in the current standard temporal resolution for the Katian and even allows for the detection of sub-Milankovitch climate-scale variability. The loss of a clear precession signal in the uppermost Vaureal Formation might be related to contemporaneous global cooling prior to the Hirnantian glacial maximum as indicated by the delta O-18 record. Complementary to the study of cyclostratigraphy of longer and often simplified records, it is important to recognize stratigraphic hiatuses and complexities on the similar to 10(4) yr scale to achieve robust sub-eccentricity-scale Paleozoic astrochronologies.

Automated summary

In this study, a high-resolution astrochronology for the Paleozoic was successfully reconstructed in the Upper Ordovician reference record of Anticosti Island, Canada. This study revealed clear astronomical cycles and highlighted the importance of recognizing complex stratigraphic hiatuses and significantly increased accumulation rates.