EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Synchronizing Rock Clocks in the Late Cambrian

Zhengfu Zhao1, Nicolas Thibault1, Tais W. Dahl2, Niels H. Schovsbo3, Aske L. Sørensen2, Christian M.Ø. Rasmussen2, and Arne T. Nielsen1
Zhengfu Zhao et al.
  • 1Department of Geoscience and Natural Resource Management, University of Copenhagen, Denmark
  • 2GLOBE institute, University of Copenhagen, Denmark
  • 3Geological Survey of Denmark and Greenland (GEUS), Denmark

The Cambrian is the most poorly dated period of the past 541 million years of Earth history. This hampers analysis of profound environmental and biological changes that took place during this period. Astronomically forced climate cycle recognized in sediments and anchored to radioisotopic ages provides a powerful geochronometer that has fundamentally refined Mesozoic–Cenozoic time scales but not yet the Palaeozoic. Here we report a continuous astronomical signal detected as geochemical variations (1 mm resolution) in the late Cambrian Alum Shale Formation that is used to establish a 16 Myr-long astronomical time scale, anchored by radioisotopic dates. The resulting time scale is biostratigraphically well-constrained, allowing correlation of the late Cambrian global stage boundaries with a 405-kyr astrochronological framework. This enables a first assessment, in numerical time, of the evolution of major biotic and abiotic changes, including the end-Marjuman extinction and the Steptoean Positive Carbon Isotope Excursion, that characterized the late Cambrian Earth.

How to cite: Zhao, Z., Thibault, N., W. Dahl, T., H. Schovsbo, N., L. Sørensen, A., M.Ø. Rasmussen, C., and T. Nielsen, A.: Synchronizing Rock Clocks in the Late Cambrian, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3197,, 2022.


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