The Geological Record of Continental Seasonality

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The distribution of warm-climate flora and fauna to high paleolatitudes during times of global warming (Cretaceous through Eocene) is a prime criterion arguing for a decreased range in seasonal temperature variation for the interiors of large continents. Such interpretations, however, are in conflict with predictions based on Energy Balance and General Circulation Climate Models. According to modeling studies, in contrast to warm and equable oceanic and coastal environments during periods of high latitude warming of the ocean, continental interiors should retain a wide range of seasonal temperature variation. As a test of this hypothesis, this study will provide quantitative measures of minimum seasonal temperature variation present within the continental interior of North America utilizing del 18O variation in fossil marine and non-marine bivalves. Advances in sampling techniques now permit microanalysis of the accretionary growth structure present in bivalves, with a time resolution of weekly to submonthly intervals. Evaluation of these data from sequential stratigraphic levels will constrain temporal changes in seasonality and mean annual temperature in the interior of North America from late Cretaceous to late Eocene times.