SGER: Triassic-Jurassic Mass Extinction Caused by Volcanism? Bio- and Magnetostratigraphic Tests in Eastern North America and Morocco

Columbia University, New York NY

Investigators

Abstract

SGER: TRIASSIC-JURASSIC MASS EXTINCTION CAUSED BY VOLCANISM? BIO-, AND MAGNETOSTRATIGRAPHIC TESTS IN EASTERN NORTH AMERICA AND MOROCCO Paul Olsen, Dennis Kent EAR-0753496, Columbia University ABSTRACT Marking one of the most severe Phanerozoic mass extinctions, that at the Triassic-Jurassic (Tr-J) boundary is comparable in magnitude to that of the K-T. While appar-ently 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 P-Tr mass extinctions, the Tr-J mass extinction is temporally linked to igneous event, in this case, the Central Atlantic Magmatic Province (CAMP) - the most areally extensive flood ba-salt known on Earth. 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 significant (albeit modest) Ir anomaly, a "fern spike," a stomatal (CO2) anomaly, and one or more nega-tive 13C excursions. While consistent with an extraterrestrial impact, much if not all of this evidence could also be explained as an effect of the CAMP. Data from eastern North America suggest that all CAMP flows post-date the extinction level by tens of thousands of years. Nonetheless, some evidence from flows of the Moroccan CAMP, including the presence of at least one zone of reverse polarity, has been interpreted as indicating that the lavas predate or were synchronous with the Tr-J boundary, making causation possible. We will use a three-pronged approach to explore the hypothesis that CAMP erup-tions could be synchronous with the mass extinction. First, we will core a 125 m section in the Jacksonwald syncline, spudding in the lowest CAMP flow and obtaining an ex-panded section of the extinction interval and surrounding 400 ky of latest Triassic and Early Jurassic strata. This core will be the basis of a uniquely detailed characterization of the sequence of events in the continental realm. Second, we will produce a magnetic stratigraphy (based on available core) for the North Mountain Basalt of the Fundy ba-sin, which is where the palynological extinction event, 13C and Ir anomalies have al-ready been recognized in the immediately underlying sediments, which because it has many more flows than other eastern North American CAMP formations and has a chemistry matching that of the oldest Moroccan flows, may better capture the brief re-verse interval seen in Morocco. Third, working with our Moroccan colleagues we will look in strata below the CAMP flows of Morocco for the reverse polarity zone in the Newark basin just below the Tr-J boundary. This approach should allow insight into our knowledge of the relationship between one of the largest mass extinctions and one of the largest eruptive events in Earth history. This award is co-funded by the Division of Earth Sciences and Office of International Science and Engineering.