International scientists probe unsolved puzzles of the Earth and beyond at "Earth System Proc...( bursts. What remains unknown is why ma...)

bursts. What remains unknown is why marine clathrates, which are common today, would suddenly destabilize 55 mya. Zachos presents geochemical evidence from deep sea sediments that indicates the event was preceded by slow warming of the ocean, which served as a trigger for destabilizing the clathrates.

A poster presentation by Jzsef Plfy, Institut fr Palontologie at the Museum fr Naturkunde in Hungary, was recently announced in a New York Times online article, "Clues to a Meteor That Aided Dinosaurs." Among the five largest extinctions documented in the fossil record, only the end-Triassic (200 million years ago) has not been previously linked to changes within the global carbon cycle. Study of rocks of that age in Hungary suggests that this extinction is also associated with environmental perturbations that are reflected in anomalous carbon isotope ratios. One scenario consistent with these results is that short-term, intensive volcanism of the Central Atlantic Magmatic Province triggered environmental changes and led to a biological crisis. Effects of volcanism at a magnitude only rarely experienced in Earth history may be similar to the current, man-made global change which also seems to drive scores of species to extinction.

Lawrence H. Tanner, Geography and Geosciences at Bloomsburg University, takes a look at scientists' ability to test various hypotheses for the cause of large-scale extinction events of the past. The Triassic-Jurassic boundary extinction event is one of the "big five" mass extinctions of the Phanerozoic Eon. The current favorite theory to explain this event is that eruptions of flood basalts that constituted the Central Atlantic Magmatic Province released CO2 or SO2 aerosols. This, in turn, caused intense global warming (from the former) or cooling (the latter). New data on the isotopic composition of fossil soils of Late Triassic and Early Jurassic age fails to find evidence of any change in the CO2 composition of the atmosphere
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Contact: Ann Cairns
acairns@geosociety.org
303-447-2020 x 1156
Geological Society of America
24-May-2001

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