Astronomical calibration of the Jurassic Hettangian Stage

The first stage of the Early Jurassic, the Hettangian, records the aftermath and recovery immediately following the end-Triassic mass extinction. To fully understand the post-extinction Earth processes, an accurate timescale is required. Although several studies have attempted astronomical calibration, results are controversial and differ by a factor of more than two. Here we propose a new age model based on multiple time series datasets (X-ray fluorescence, core gamma ray, magnetic susceptibility, organic carbon isotopes) from the Prees 2C borehole, Cheshire Basin, UK, which provides a more complete Hettangian succession than the classic composite section in the Bristol Channel area. The resulting minimum duration of the Hettangian is 2.18 Myr based on a 405 kyr tuned age model, and we find no compelling evidence for the much longer duration of up to 4 Myr recently proposed, indicating a relatively brief post-extinction recovery time. By anchoring through existing U-Pb dates for the Triassic-Jurassic boundary and incorporating the uncertainties of dating and stratigraphic gaps, the Hettangian is suggested to range from 201.36 ± 0.18 Ma to 199.18 ± 0.18 Ma. The Hettangian timescale established in this study provides an important reference value for improving the international geological time scale (GTS) of the Jurassic Period.