The longest delay: the slow recovery from the Hangenberg mass extinction

This project will examine the Hangenberg mass extinction and the subsequent failure to recover during the Early Carboniferous (Tournaisian) by combining a study of select fossil groups, especially the foraminifers and brachiopods, with palaeoenvironmental study, especially of seafloor oxygen levels. Field studies will take place in the type sections of this interval in Belgium, plus sections in southern Ireland, and South Wales and will examine both carbonate and clastic marine strata that record a broad range of palaeoenvironments from shallow-to-deep settings. Details of diversity trends (origination and extinction rates) in marine communities will be established. The student will be trained in a range of both palaeontological and sedimentological disciplines. Foraminifer identification in carbonates will primarily rely on petrographic analysis and it is intended that a detailed evolutionary history of this group will be produced based on taxonomic analysis of samples, supplemented with published records in the palaeontological literature. The records of other common groups (e.g. crinoids, brachiopods and rugose corals) will also allow comparisons to be drawn to see if recovery was initiated in specific environmental settings. Environmental context for Tournaisian biodiversity will come from sedimentary logging, microfacies of carbonates and pyrite petrography using scanning electron microscope analysis of polished blocks to help constrain redox levels. The coverage of diversity trends in distant regions will allow potential regional scale variations to be examined.

This project addresses a large-scale question: what controls global biodiversity? Following a mass extinction, vacated ecospace offers the opportunity for radiation and innovation amongst the surviving groups which is (eventually) seen in the Early Carboniferous. Factors such as temperature, provincialism and habitat area (itself controlled by factors such as sea-level and oxygen levels) are all possible determinants of diversity levels which can be studied during this interval.