SGER: Triassic-Jurassic Mass Extinction Caused By Volcanism? Carbon Isotopic Tests In Eastern North America And Morocco

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SGER: TRIASSIC-JURASSIC MASS EXTINCTION CAUSED BY VOLCANISM? CARBON ISOTOPIC TESTS IN EASTERN NORTH AMERICA AND MOROCCOJessica WhitesideEAR-0801138, Brown UniversityABSTRACTThe Triassic-Jurassic (Tr-J) boundary, 200 million years ago, marks one of the Earth's most severe mass extinctions, comparable in magnitude to that of the famous Cretaceous-Tertiary (K-T) boundary. While apparently decimating at least half of then-extant terrestrial diversity, it set the ecological stage for the ascent of dinosaur-dominated ecosystems. As with the K-T and Permo-Triassic mass extinctions, the Tr-J mass extinction is temporally linked to the Earth's largest flood basalt event, the Central Atlantic Magmatic Province (CAMP). Previous work on the Tr-J boundary in the Newark and Fundy rift basins of eastern North America and work by others in marine and continental deposits demonstrate additional parallels to the K-T boundary including a modest Ir anomaly, a "fern spike," a stomatal (CO2) anomaly, and a pair of negative 13C excursions. While these observations as condign with an extraterrestrial impact, much if not all of this evidence is also consonant with the giant flood basalts of the CAMP. However, data from eastern North America suggest that all CAMP flows post-date the extinction level by tens of thousands of years, making causation unlikely. However, there is some suggestion that some Moroccan CAMP lavas do predate or were synchronous with the Tr-J boundary, making it pos-sible that the CAMP was the cause of the extinctions. PI will use a two-pronged approach to test this possibility. First, working with Moroccan colleagues and a graduatate student, she proposes to establish the organic 13C chemostratigraphy (including bulk and compound-specific n-alkanes from leaf cuticular waxes) of strata directly surrounding and interbedded with the Mo-roccan CAMP basalts. Second, to better characterize the pre-boundary variations in organic 13C in the Newark basin, thus far poorly known, she will recover the organic 13C stratigraphy in a core penetrating 125 m (~400 ky) below the boundary in the Jacksonwald Syncline to be recov-ered as part of a SGER project led by P.E. Olsen and D.V. Kent. These two approaches will al-low a definitive test of whether any known basalt eruptions could have cause the Tr-J mass ex-tinction. The project will also result in an much better understanding of the carbon iso-topic signatures of ecological disruption accompanying a mass-extinction, which in turn, will provide deeper insight into the long-term implications and possible unex-pected or highly non-linear consequences of human-induced changes and other mas-sive volcanic eruptions.This award is co-funded by the Division of Earth Sciences and Office of International Science and Engineering.