The causes and dynamics of the Permian-Triassic boundary (PTB) mass extinction, the largest in Earth history, remain uncertain. Gradual deterioration of marine and terrestrial environments during the Late Permian and persistence of inhospitable conditions through the Early Triassic suggest that intrinsic factors were important, but an extinction rate peak, abrupt lithofacies changes, and geochemical anomalies associated with the end-Permian event horizon are evidence of a catastrophic event (e.g., massive volcanic eruption, bolide impact, and/or large-scale oceanic overturn). Despite long study of the PTB, there are remarkably few integrated, high-resolution chemostratigraphic studies of marine boundary sections that can address critical questions related to the extent and intensity of Permo-Triassic deep-ocean anoxia, patterns of upwelling of toxic deep-ocean waters onto shallow-marine shelves and platforms, the relationship of such events to contemporaneous changes in seawater carbonate saturation and to the delayed recovery of marine biotas, controls on the post-extinction global negative C-isotope shift, and the relative timing and causal relationship of PTB crises in the marine and terrestrial realms. In this project, we propose to generate geochemical proxy datasets consisting of magnetic susceptibility, elemental concentrations, TOC-TIC, ?Ô13Ccarb-?Ô13Corg, S-Fe speciation, ?Ô34Ssulfide-?Ô34Ssulfate, REEs, and biomarkers for a total of 19 sections in eight study areas, including 8 sections in four areas of the former Panthalassic Ocean (the Cache Creek terrane, Western Sedimentary Basin, and Sverdrup Basin of Canada, and the Maitai-Waipapa terranes of New Zealand) and 11 sections in four areas of the former Tethys Ocean (Vietnam-China, India, Iran, and Italy). Conodont biostratigraphy combined with C-isotope and MS event stratigraphy will facilitate correlations within and between study areas. Paleoceanographic modeling will be used to investigate the effects of potential forcings on Permo-Triassic ocean chemistry and sedimentary fluxes, and comparisons with globally integrated chemostratigraphic datasets will allow refinement of model simulations. This project has the potential to yield important new findings regarding events at the Permian-Triassic boundary and key insights regarding proximate and ultimate controls on contemporaneous chemical oceanographic perturbations. Investigation of catastrophic climate and environmental change associated with the largest mass extinction in Earth history should be of considerable interest to both the Earth-science community and the scientifically literate public. The broader impacts of the project are varied and include public outreach and dissemination of project results, mentoring of undergraduate and graduate students, development of research synergies among a diverse group of geoscience professionals, and the potential for results of broad scientific significance. The PIs are committed to training the next generation of scientists (they have collectively supervised ~60 graduate students, and all are actively engaged in advising and training undergraduate students), to advancing science education in the public schools, and to achieving greater ethnic and gender diversity among these future scholars (Algeo and Ellwood are both involved in programs to recruit minority students). Project datasets funded through NSF will be made available to the larger scientific community through CHRONOS and PaleoStrat.
Major Goals of the Project: The Permian–Triassic boundary interval in Earth history is very important because most organisms on Earth went to extinction at that time, making it the largest extinction event ever. We have been working on several Permian–Triassic boundary sections (~252 million years old) to better understand why this happened and to understand how long it took. Six localities were chosen for study during this project, two in remote areas of northern Vietnam, one in central Turkey and three in Slovenia. The purpose/goal of this work was to identify the boundary position with precision at these localities, to identify the extinction event levels and the position of these levels in the successions studied, to identify anomalous layers including ash beds, to develop high-resolution time-series data sets to allow us to better understand timing of events, and to better resolve the cause of this extinction event. Significant Results: The work in Vietnam proved to be the most productive, but required several trips to collect large amounts of material from the section and eventually narrow down the areas of interest within the section. Using the samples collected during these trips we were able, for the first time, to extract a number of conodonts from the section. Conodonts are distinctive microfossils, now extinct, that are used for correlation and defining the position of the Permian–Triassic boundary. Once we had the conodonts, we were able to compare these fossils from Vietnam to the unique, reference locality in China. Finding the conodonts was important because no other studies from this locality in Vietnam have reported conodonts from the section, and without them, it is not possible to identify, with high precision, the Permian–Triassic boundary or the critical extinction levels in the section. These data have allowed us to identify the specific position of the boundary and after several trips to the area, additional samples collected allowed us to work out the complexities of the section. Time-series work on ~400 samples using geophysical data from the section has provided excellent timing for the extinctions and the unusual geochemical variations that we see in the section. These data have been analyzed and we are now working on three papers, one has been submitted to Science, a second will be submitted within weeks, also to Science, and a third paper will be submitted to Geology; it is almost finished. In these papers we conclude that the Permian–Triassic extinction event was the result of two factors. First, products ejected from a near-Earth stellar explosion destabilized the biota on Earth, and second, in conjunction with extensive volcanism, this early destabilization lead to the large magnitude, global extinction event observed at that time. In the Science paper we discuss timing of these events, concluding that they lasted for tens of thousands of years. In a second paper we present data supporting the previous finding of fly-ash in the oceans, generated by global fires started by volcanic eruptions. The work in Slovenia and Turkey was somewhat disappointing, primarily because the biostratigraphic information recovered so far is poor. In Turkey, there appears to be an erosional unconformity at the Permian–Triassic boundary in the section we sampled. Therefore resolution of the boundary there is not possible. In Slovenia we took an additional trip to resample one of the promising sections we had previously examined, where there was some known, but poor biostratigraphic information. This second trip extended the geochemical and geophysical data sets we have for section. Because there are not many fossils that have been recovered from the section, the impact of this work will not be great, but with the additional sampling we hope to be able to at least correlate, with good precision, the Slovenian samples to the reference locality in China. This work should help us better understand the dispersal of conodonts throughout the World’s oceans at that time, and will be the subject of a paper on which we are working.
