Cyclostratigraphy, stratigraphic gaps and the duration of the Hettangian Stage (Jurassic): insights from the Blue Lias Formation of southern Britain

Research on the Blue Lias Formation along the Dorset and East Devon Coast reveals that the Hettangian Stage of the Jurassic period lasted at least 4.1 million years, nearly double previous estimates. This finding was derived from cyclostratigraphic analysis using magnetic susceptibility logs as a proxy for carbonate content, combined with Bayesian probability spectra to confirm cyclicity consistent with astronomical climate forcing. The study identified 62 ammonite biohorizons with minimum durations ranging from 0.7 to 276 thousand years, with most being less than 41 thousand years. By integrating local stratigraphic gaps and constructing a composite time scale, the researchers improved the duration estimate for the Hettangian Stage, providing new insights into the temporal framework of this geological period.

Weedon, G. P., Page, K. N., & Jenkyns, H. C. (2018). Cyclostratigraphy, stratigraphic gaps and the duration of the Hettangian Stage (Jurassic): insights from the Blue Lias Formation of southern Britain. Geological Magazine, 156(9), 1469–1509. https://doi.org/10.1017/s0016756818000808