Diagenetic xenotime age constraints on the Sanjiaotang Formation, Luoyu Group, southern margin of the North China Craton: Implications for regional stratigraphic correlation and early evolution of eukaryotes

Abstract

Eukaryote fossil-bearing Ruyang and Luoyu groups are extensively exposed along the southern margin of the North China Craton, but their age has long been a matter of controversy due to the absence of reliable radiometric dates. By dating detrital zircons and diagenetic xenotimes from the Sanjiaotang Formation of the Luoyu Group, this paper confirms that the Ruyang and Luoyu groups were deposited during the period of 1750–1400Ma. The new age constraints suggest that the Sanjiaotang Formation is coeval with the Xiamaling Formation of the Jixian Group on the northern margin of the North China Craton. Correlation of the Luoyu Group with the Jixian Group is thus indicated. The Ruyang and Luoyu groups contain abundant fossils of eukaryotic organisms such as acritarch and macroalgae. Accordingly, eukaryotic proliferation extends back to the Mesoproterozoic, consistent with results of molecular phylogenetic analysis that a rapid morphological diversification of eukaryotic organisms occurred prior to 1400Ma.