Paleobiological and paleoenvironmental control on the origin and diversification of Late Ordovician and early silurian epicontinental brachiopod faunas of North America

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A major concern about the 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. During the past 530 million years (myr) of the Phanerozoic Earth history, one of the two grandest episodes of global warming and sea-level rise occurred in Late Ordovician-Early Silurian time (460-430 myr ago), when the North American paleocontinent was flooded by epicontinental seas, in which marine life thrived, with brachiopods being the dominant benthic shelly organisms. In this proposal, the rich brachiopod fossil records of North America will be studied to address several key questions regarding the epicontinental marine shelly faunas: 1) How did the epicontinental brachiopod faunas originate, disperse, and diversify during the global warming and marine transgression? 2) Why did the epicontinental brachiopod faunas become isolated during the Late Ordovician marine transgression but not during the Early Silurian episode? and 3) What environmental and biological factors controlled the differentiation of contemporaneous brachiopod faunas and the temporal fluctuations in biodiversity during the Late Ordovician-Early Silurian? The approach to these questions is to compare the brachiopod faunas between continental-margin seas (e.g. Anticosti Basin, Mackenzie Mountains, Arctic Canada) and inland basins (Hudson Bay, Michigan, and Williston basins), and by tracing the morphological changes in several brachiopod lineages and their paleoecological settings, using cladistic and multivariate analyses. Results from the proposed research can help us better understand modern global change from the perspective of million year-scale global warming and biodiversity change that occurred in ancient Earth history.