ROCKS FROM THE EAST: THE TONIAN SYSTEM ON EASTERN MARGIN OF THE NORTH CHINA CRATON (Invited Presentation)

The Tonian Period represents a pivotal interval to understand the evolutionary transition from the Mesoproterozoic “boring billion” to the Cryogenian snowball Earth. Some of the most transformative events in the Earth-life history, such as the rise of major eukaryotic groups and the breakup of Rodinia, happened during this period. Meso- to Neoproterozoic sedimentary rocks are widely distributed along the eastern margin of the North China Craton. However, their exact depositional age and internal correlation have long been debated. Recently published geochemical, paleontological, and chronological data from the Meso- to Neoproterozoic sequences in North China Craton provide important stratigraphic constrains on these sequences. Here we review these sequences based on new and published lithostratigraphic, biostratigraphic, chemostratigraphic, and chronostratigraphic data. We conclude that, in the eastern margin of North China Craton: (1) the majority of the Neoproterozoic sequences are early to middle Tonian (1,000 to 800 Ma) in age, with limited deposits of possible Ediacaran age; (2) the majority of the early Tonian sequences are onlapped by Cambrian strata without intervening Cryogenian or Ediacaran deposits, suggesting the existence of the “Great Unconformity” in North China with a missing sedimentary record of 200–300 myr; (3) the contact between the Meso- and Neoproterozoic is mostly conformable with no apparent depositional unconformity; (4) the Meso- to Neoproterozoic sequences are rich in paleontological records, providing crucial insights into the early evolution of eukaryotes and the regional and global correlation of the Tonian System.