Magnitude and Duration of a Co 2 Super Greenhouse at the Triassic-jurassic Boundary

Stratigraphic transitions from the Triassic to the Jurassic (Tr-J) around 200 Ma record an abrupt extensive global collapse and slow recovery of biodiversity, the cause of which has been tied to a massive abrupt, extrinsically caused climate change (Ward et al., 2001; Hesselbo et al., 2002). The main thrust of the proposed research will be to reconstruct Tr-J paleo-atmospheric CO2, suggested to have risen dramatically at this time, using stomatal density of the thermophilic dipteraceous fern Clathropteris meniscoides and cheirolepidaceous conifers from outcrop and cores of lacustrine deposits from three coeval Early Mesozoic rift valleys preserved in eastern North America. These sections have already been shown to record a mass extinction in fauna and flora and preserve a modest Ir anomaly, a fern spike, and a negative dC change of –5‰ at the boundary (Figure 1), in remarkable parallelism to the Cretaceous-Tertiary boundary (Olsen et al., 2002). The paleomagnetic reversal stratigraphy and cyclostratigraphy of the Newark Supergroup provides a framework for rigorous temporal and geographic control between separate but tectonically similar basins. The results of this proposed research will help differentiate between the possible mechanisms proposed for the origins of the CO2 anomaly: an extraterrestrial impact (Olsen et al., 2002) and massive continental flood basalt eruptions (Hesselbo et al., 2002). It will also provide greater spatial and temporal resolution of recovery from such perturbations in the face of the current perilous anthropogenic rise in the Earth’s atmospheric CO2 concentration.