zircon; U-Pb dating; Triassic; Permian; mass spectrometry; Geochronology; Jurassic; conodonts; volcanic ash beds; ammonoids; time-scale
Widmann Philipp, Bucher Hugo, Leu Marc, Vennemann Torsten, Bagherpour Borhan, Schneebeli-Hermann Elke, Goudemand Nicolas, Schaltegger Urs (2020), Dynamics of the Largest Carbon Isotope Excursion During the Early Triassic Biotic Recovery, in Frontiers in Earth Science
, 8, 126.
Widmann P., Davies J.H.F.L., Schaltegger U. (2019), Calibrating chemical abrasion: Its effects on zircon crystal structure, chemical composition and U Pb age, in Chemical Geology
, 511, 1-10.
Baresel B., D'Abzac F.-X., Bucher H., Schaltegger U. (2017), High-precision time-space correlation through coupled apatite and zircon tephrochronology: An example from the Permian-Triassic boundary in South China, in Geology
, 45, 83-86.
Baresel B., Bucher H., Brosse M., Cordey F., Guodun K., Schaltegger U. (2017), Precise age for the Permian–Triassic boundary in South China from high-precision U-Pb geochronology and Bayesian age–depth modeling, in Solid Earth
, 8, 361-378.
Baresel B., Bucher H., Bagherpour B., Brosse M., Guodun K., Schaltegger U. (2017), Timing of global regression and microbial bloom linked with the Permian-Triassic boundary mass extinction: implications for driving mechanisms, in Scientific Reports
, 7, 43630.
Ovtcharova Maria, Goudemand Nicolas, Hammer Oyvind, Guodun Kuang, Cordey Fabrice, Galfetti Thomas, Schaltegger Urs, Bucher Hugo (2015), Developing a strategy for accurate definition of a geological boundary through radio-isotopic and biochronological dating: The Early–Middle Triassic boundary (South China), in Earth Science Reviews
, 146, 65-76.
This proposal is seeking for a continuation of funding to work on the temporal quantification of the latest Permian, the Triassic and the Early to Middle Jurassic time-scale with high-precision U-Pb geochronology using state or the art procedures and achieving age resolution of better than ± 100'000 years. The principal object is the precise intercalibration of the bio- and chemostratigraphic record in order to understand the processes of environmental change in the geological past, and to quantify rates of biotic and abiotic responses. The project is subdivided into 4 parts:A.Reassessment of the Permo-Triassic boundary in deep-water and outer platform facies in the Nanpanjiang Basin (S. China). Among the main objectives are: (i) definition of the PTB in shallow water environment (outer platform facies) relative to a conspicuous microbial limestone at the PTB, relative to conodont associations instead of the first appearances of a single index species and relative to C isotopes; (ii) definition of the PTB in deeper water sections, relative to the lithological change from mixed carbonate-siliciclastic sediments to shales and relative to C isotopes; (iii) development of tephrachronological tools using zircon and apatite trace element compositions, and (iv) detecting changes in the type of regional volcanism to understand its influence on seawater carbon isotope composition in South China.B.We further intend to calibrate not only important boundaries in the History of Earth and Life but also protracted time intervals during which global cycles of biotic and abiotic changes closely followed each other in time. The point here is to quantify rates of change of variables such as biotic diversity and turnover, the C-cycle, sea surface temperature and seawater acidification linked to atmospheric CO2 in order to address the following general questions: (1) Does the speed of change of such global abiotic parameters impact on the biotic responses of organisms during cycles of extinction and recoveries or do absolute values matter above all? (2) Are any response times between these parameters detectable within these cycles by means high- precision of radio-isotopic dates? The rates of biotic and abiotic feedback to global environmental change can be studied in deep time when process rates are slow, and by using our high-precision geochronological tools. These objectives will be attained through high-precision U-Pb dating, detailed biochronology and C, O (possibly Ca) isotope time series in the Early Triassic of South China. C.After our previous studies in the topmost Rhaetian, at the Triassic/Jurassic boundary, in the Hettangian and the Toarcian, we plan to explore new sections in Nevada and Oregon (USA) and in Central Peru, in order to complete the Triassic-Jurassic time-scale by adding temporal tie-points in the Sinemurian, Pliensbachian, Aalenian and Bajocian that are well-defined by ammonoid biochronology and radio-isotopic dating. The geochronological database for the Middle Jurassic is particularly poor when compared to the rest of the Mesozoic; the main GSSP's of the Aalenian, Bajocian and Bathonian have not been dated with radio-isotopic methods. A special effort is planned to fill these gaps using well documented sections in Oregon (USA).D.U-Pb age determinations at the forefront of precision and accuracy needs a constant effort of system calibration through synthetic solutions and natural reference materials in order to document short and long-term reproducibility, and inter-laboratory cross-calibration exercises to document the potential of the international EARTHTIME community to maintain our unprecedented precisions.This project intends to continue our significant contribution to the Mesozoic timescale by cross-calibration of bio- and chemo-stratigraphic records by high-precision radio-isotopic dating. It will try to temporally resolve abiotic and biotic responses to global change and to quantify rates of these changes. These very ambitious objectives are tackled with a very challenging sampling strategy for a variety of age-diagnostic fossils, ash beds and carbonates, in combination with forefront analytical techniques in radio-isotopic dating, trace element mineral analysis, and stable and radiogenic isotope analysis.