Calibration of the geological time scale by U-Pb dating of zircon in volcanic ash beds

We are working on the quantification of the Geological Time Scale from the latest Permian to the Jurassic/Cretaceous boundary via a series of different research projects using highest-precision U-Pb geochronology of zircon in volcanic ash beds. State-of-the-art procedures include chemical abrasion of zircon, double-isotope tracer for both Pb and U isotope analysis, allowing us to correct for isotope fractionation online, lowest procedural Pb blanks of 100-200 femtograms, leading to an age resolution of ± 150'000 years for a single analyses, and ± 40'000 years for a cluster of 4 points. Such techniques have been applied to the Permo-Triassic boundary (Baresel et al., 2017 a, b and c), to the lower and middle Triassic (Ovtcharova et al., 2006; 2015; Widmann et al., 2020), to the latest Triassic (Wotzlaw et al., 2014a), the Triassic-Jurassic boundary (Schaltegger et al., 2008; Schoene et al., 2010; Guex et al., 2012), the earliest Jurassic (Sell et al., 2014; Lena et al., 2019) and the Jurassic-Cretaceous boundary (Lena et al. 2017). Research continues to characterize environmental change in the lower to middle Triassic, to establish rates of environmental change, climate change, and biotic feedback to changing environmental conditions (collaborative projects with University of Zürich, Switzerland).

Ash bed in lower Triassic strata of the Nanpanjiang basin, S. China

Baresel B., D'Abzac F.-X., Bucher H. & Schaltegger U. (2017a) High-precision time-space correlation through coupled apatite and zircon tephrochronology: an examples from the Permo-Triassic boundary in S. China. Geology, doi:10.1130/G38181.1

Baresel B., Bucher H., Bagherpour B., Brosse M., Guodun K., Schaltegger U. (2017b) Timing of global regression and microbial bloom marking the Permo-Triassic mass extinction. Nature Sci. Rep., 7:43630, doi:10.1038/srep43630

Baresel B., Bucher H., Brosse M., Cordey F., Guodun K. & Schaltegger U. (2017c) High-precision U-Pb dating of the Permian-Triassic boundary in marine paleoenvironments in South China. Solid Earth, 8, 361-378; doi:10.5194/se-2016-145

Guex J., Schoene B., Bartolini A., Spangenberg J., Schaltegger U., O’Dogherty L., Atudorei V., Taylor D. & Bucher H. (2012) Post-extinction recovery of the ammonoids and carbon isotope cycle during the Early Jurassic: Geochronological constraints. Paleogeogr. Paleoclim. Paleoecol. 346-347, 1-11

Lena L.O.F., Ramos V.A., López-Martínez R., Vennari V., Lescano M., Naipauer M., Pimentel M.M., Aguirre-Urreta B., Samankassou E. & Schaltegger U. (2019) High-precision U-Pb ages in the Late Tithonian to Early Berriasian and implications for the numerical age of the Jurassic/Cretaceous boundary. Solid Earth, 10, 1-14, 10.5194/se-10-1-2019

Lena L., Taylor D., Guex J., Bartolini A., Adatte Th., Van Acken D., Spangenberg J., Samankassou E., Vennemann T. & Schaltegger U. (2019) The driving mechanisms of the carbon cycle perturbations in the Late Pliensbachian (Early Jurassic). Sci. Rep. 9:18430; doi.org/10.1038/s41598-019-54593-1

Ovtcharova M., Bucher H., Schaltegger U. Galfetti T., Brayard A. & Guex J. (2006) New Early to Middle Triassic U-Pb ages from South China: calibration with the ammonoid biochronology and implications for the tempo of the Triassic biotic recovery. Earth Planet. Sci. Lett. 243, 463-475

Ovtcharova M., Goudemand N., Hammer O., Guodun K., Cordey F., Galfetti T., Schaltegger U. & Bucher H. (2015) Developing a strategy for accurate definition of a geological boundary through radio-isotopic and biochronological dating: the Early-Middle Triassic boundary (South China). Earth Sci. Rev. 146, 65-76

Schaltegger U., Guex J., Bartolini A., Schoene B. & Ovtcharova M. (2008) Precise U-Pb age constraints for end-Triassic mass extinction, its correlation to volcanism and Hettangian post-extinction recovery. Earth Planet. Sci Lett., 267, 266-275

Schoene B., Guex J., Bartolini A., Schaltegger U. & Blackburn T.J. (2010) Correlating the end-Triassic mass extinction and flood basalt volcanism at the 100,000-year level. Geology 38, 387-390

Sell B., Ovtcharova M., Guex J., Jourdan F., Schaltegger U. (2014) Evaluating the link between the Karoo LIP and climatic-biologic events of the Toarcian Stage with high-precision U-Pb geochronology. Earth Planet. Sci. Lett. 408, 48-56.

Widmann P., Bucher H., Leu M., Vennemann T., Bagherpour B., Schneebeli-Herrmann E., Goudemand N. & Schaltegger U. (2020) Dynamics of the largest carbon isotope excursion during the Early Triassic biotic recovery. Frontiers in Earth Science, https://doi.org/10.3389/feart.2020.00196

Wotzlaw J.F., Bartolini A., Guex J., Gallet Y., Krystyn L., McRoberts C., Taylor D., Schoene B., Schaltegger U. (2014a) Towards absolute numerical calibration of the Late Triassic: High-precision U-Pb geochronology constraints on the maximum duration of the Rhaetian. Geology 42, 571–574.

Wotzlaw J.F., Hüsing S.K., Hilgen F.J. & Schaltegger U. (2014b) High-precision U-Pb geochronology of astronomically dated volcanic ash beds from the Mediterranean Miocene. Earth Planet. Sci. Lett. 407, 19-34.