March GEOLOGY and GSA TODAY media ...(olybdenum isotope evidence for global oc...)

Anthony Cohen et al., Department of Earth and Environmental Sciences, The Open University, Milton Keynes MK7 6AA, UK. Pages 231-234.

What happens to the Earth during and after abrupt global warming, over time scales of hundreds or thousands of years? One way of addressing this question is to use computer models to try to predict the course of future climate and environmental conditions. However, the uncertainty of longer-term predictions may be substantial because of our relatively poor understanding of the great complexity of the Earths behavior. Adopting a complementary approach in their study, Pearce et al. examine and de-code the geological record of extreme, but infrequent, events that occurred in the distant past. These records have the potential to provide quantifiable information about precisely how Earth has actually responded to severe environmental change in the longer term. Pearce et al. show that there was widespread reduction in the oxygen content of the oceans during an abrupt period of global warming 183 million years ago in the Early Jurassic period, and that these conditions persisted for approximately 200,000 years. The authors also demonstrate that the changes in seawater oxygenation at that time were periodic and were coupled with regular, large-scale fluctuations in the global carbon cycle. The precise relationships between the various expressions of this environmental crisis in the Early Jurassic, which also involved a significant mass extinction of marine and terrestrial species, may be able to provide valuable constraints that could help to validate our predictions about environmental change in the future.

The nature of shallow-water carbonate lithofacies thickness distributions

Peter Burgess, Shell International E&P, EPT-RXF, PO Box 60, Rijswijk, Rijswijk
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