Late Ordovician brachiopod faunal endemism and mass extinction during drastic climate change, ocean anoxia and sea-level fluctuations

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Our concern about global warming today is its effect on sea level rise and biodiversity change. The study of modern global change in climate and biodiversity is confined to the scale of decade to millennium. Paleontologists investigate environmental and biodiversity changes in Earth history at a million-year scale based on fossil record preserved in sedimentary rocks and thus provide unique and valuable data and interpretations to complement studies on modern and recent global change. During the past 530 million years (myr) of the Phanerozoic Earth history, one of the two grandest episodes of global sea-level rises occurred in the Late Ordovician (460-443 myr ago), when much of North America was flooded by epicontinental seas, in which marine life thrived, with brachiopods being the dominant benthic shelly organisms. This was followed by a terminal Ordovician glaciation and mass extinction event. In this proposal, the rich brachiopod fossil record of North America will be studied to determine the responses of Late Ordovician marine benthic shelly faunas to drastic sea level changes. In particular, the following questions will be addressed: 1) How did the continental-margin brachiopod faunas give rise to, and was subsequently replaced by, the epicontinental-sea faunas during the Late Ordovician sea level highstand? 2) Why did the epicontinental brachiopod faunas become highly endemic during the Late Ordovician marine transgression but not during some other similarly high sea-level? and 3) Why did the terminal Ordovician glaciation cause a mass extinction, whereas other major glaciations did not? The approach to these questions is to trace the brachiopod evolution at the species, genus, community, and faunal levels from both continental-margin (e.g. Anticosti Basin, Cincinnati Arch, Mackenzie Mountains) to inland-basin (Hudson Bay, Michigan, and Williston basins) depositional environments through the Late Ordovician sea-level fluctuations, using cladistics, multivariate and other numerical analyses. Results from the proposed research can help us better understand modern global change from the perspective of million year-scale global climate-biodiversity changes in Earth history.