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.
The West Blind Fiord sedimentary section crops out on Ellesmere Island (Canadian Arctic). This important geologic section includes sedimentary units that span the late Permian into the early Triassic, a time period noted for a global events that included a pervasive and profound mass extiction of organisms. The sedimentary geochemistry, as determined using a suite of major and minor elemental chemistry, isotopes and biomarkers, at the West Blind Fiord site documents a stepwise environmental deterioration in the marine Sverdrup Basin as a result of volcanic disturbances to surrounding landmasses. Younger sediments show increased detrital sediments, more marine productivity, and loss of siliceous sponges. Well-documented mass extinction horizons inTethyan shallow-marine sections are ~100 k.y. younger than those found at this Arctic location. This off-set in timing probably reflects global terrestrial detrital sediment fluxes increased well before the onset of main-stage Siberian Traps flood basalt volcanism and suggests the deleterious effects of volcanic eruptions affected the Boreal region but not marine ecosystems in the peri-equatorial Tethyan region. Data produced by this research effort included a wide array of geochemical analyses, isotopic analyses and molecular fossil, or biomarker, results. Work at Penn State concentrated on organic nitrogen isotopic signatures, complementing organic geochemical analyses conducted at the Massachusetts Institute of Technology (MIT).
