Project

biotic recovery; U-Pb dating; zircon; volcanic ash beds; interlaboratory calibration; mass spectrometry; Geochronology; Permian/Triassic boundary; Triassic/Jurassic boundary; Peru; China; time-scale

Lead
Lay summary
This project proposal suggests to use a high-precision and high-accuray U-Pb dating of volcanic zircon in ash beds to date two major events in the evolution of life on our planet: (1)Investigating the mass extinction event at the Permian/Triassic boundary and the following period of post-extinction recovery, working on a complete section in the Lower Triassic (Dienerian, Griesbachian, Spathian, Smithian substages) of South China. (2)Investigating the mass extinction event at the Triassic/Jurassic boundary and the subsequent biotic recovery, studying a complete, ammonoid- and conodont-rich and well-documented section in northern Peru, covering the T/J boundary and the Lower Jurassic. We date zircon from several ash beds that are intercalated with carbonates and shales, and are precisely correlated by ammonoid and/or conodont biochronology. We want to determine precise duration of substages, enable quantitative modelling of recovery mechanisms, and correlate biostratigraphic evidence for globally disturbed ecosystems to the well-dated volcanic eruptions of the Siberian Traps and the Central Atlantic Magmatic Province, respectively. The ages are obtained by state-of-the-art U-Pb dating techniques using zircon from volcanic ash beds. The results will have to be cross-calibrated with other U-Pb laboratories working at the same level of precision, in order to assure the accuracy of the results, i.e. to avoid systematic interlaboratory biases. This effort will allow for the first time direct comparison of U-Pb ages from different laboratories at the permil uncertainty levels, and correlation of different timescales established in different laboratories. Through this research effort we hope to contribute to better understanding of the evolution of life on our planet and its quantification: higher resolution of evolutionary stages by overcoming systematic biases between techniques and laboratories may used to relate important diversity changes in the biochronological record to events affecting our ecosystems such as volcanism or Milankovic tuning. The proposed research is therefore part of a much broader interest in a transdisciplinary effort, including paleoclimatology, biochronology, cyclo- and magnetostratigraphy.

Direct link to Lay Summary

Last update: 21.02.2013

Number	Title	Start	Funding scheme

This project proposal suggests to use a high-precision and high-accuray U-Pb dating of volcanic zircon in ash beds to date two major events in the evolution of life on our planet: (1) Investigating the mass extinction event at the Permian/Triassic boundary and the following period of post-extinction recovery (South China). (2) Investigating the mass extinction event at the Triassic/Jurassic boundary and the subsequent biotic recovery (northern Peru).
The project intends to date zircon from several ash beds that are intercalated with carbonates and shales, and are precisely correlated by ammonoid and/or conodont biochronology. We want to determine precise duration of substages, enable quantitative modelling of recovery mechanisms, and correlate biostratigraphic evidence for globally disturbed ecosystems to the well-dated volcanic eruptions of the Siberian Traps and the Central Atlantic Magmatic Province, respectively. We will contribute to the understanding of the systematic age differences between U-Pb laboratories as well as systematic biases between U-Pb and Ar-Ar dating systems, the latter being most likely due to a poorly known 40K decay constant. Presently accepted too young data for P/T and T/J boundaries are largely falsifying the estimates of tempo and duration of post-extinction recovery.
The ages will be obtained by state-of-the-art U-Pb dating techniques developed recently on our laboratory, using zircon from volcanic ash beds. We rely on new measurement procedures developed on our new TRITON mass spectrometer. We intend to achieve permil precision and accuracy by thorough cross-calibration with other leading U-Pb laboratories.
Through this research effort we hope to contribute to better understanding of the evolution of life on our planet and its quantification: higher resolution of evolutionary stages by overcoming systematic biases between techniques and laboratories may used to relate important diversity changes in the biochronological record to events affecting our ecosystems such as volcanism or Milankovic tuning. The proposed research is therefore part of a much broader interest in a transdisciplinary effort, including paleoclimatology, biochronology, cyclo- and magnetostratigraphy.