Long duration of benthic ecological recovery from the early Toarcian (Early Jurassic) mass extinction event in the Cleveland Basin, UK

Abstract

The Cleveland Basin of Yorkshire, UK hosts one of the most iconic Lower Jurassic rock successions for studying the Toarcian oceanic anoxic event and the associated mass extinction, yet our understanding of the subsequent ecological recovery is limited. This study documents for the first time the full extent and nature of benthic macrofaunal recovery from the early Toarcian mass extinction event within the Cleveland Basin. Benthic oxygen levels remained low following the extinction event, allowing specialist communities that were tolerant to low oxygen levels to dominate. Recovery began properly once the seafloor ventilation had begun to improve and was first expressed by an expanded ecological tiering structure. Recovery progressed slowly thereafter with the possible return to oxygen-restricted environments. As sea-levels fell and sand-dominated deposition again occurred within the basin, the recovery accelerated, with ecological and species richness being reattained and even exceeding pre-extinction levels. Full recovery occurred, at the latest, c. 7 myr after the extinction event; this duration is on par with estimates of recovery rates from the largest mass extinction event of the Phanerozoic (the end-Permian mass extinction event). Recovery within the Cleveland Basin was likely to have been strongly influenced by local sea-levels and the continuation of challenging environmental conditions after the extinction event. Supplementary material: Benthic fossil occurrence data are available at https://doi.org/10.6084/m9.figshare.c.6332986