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

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 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. Following the extinction event benthic oxygen levels remained low, allowing for specialist low-oxygen tolerant communities to dominate. Recovery properly commences once sea floor ventilation began 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 occurred again within the basin, the recovery accelerated with ecological and species richness reattaining, and furthermore exceeding, pre-extinction levels. Full recovery occurred, at the latest, ca. 7 myr after the extinction, this duration is on par with estimates of recovery rates from the largest mass extinction 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 continuation of challenging environmental conditions after the extinction event.