New chronological and paleontological evidence for Paleoproterozoic eukaryote distribution and stratigraphic correlation between the Yanliao and Xiong’er basins, North China Craton

Abstract

North China Craton is one of the old cratons preserved continues recording of the early evolution of eukaryotes. Organic wall microfossils (OWMs) of eukaryotic affinity have been found in the late Paleoproterozoic sediments from the Yanliao and Xiong’er basins that located in the northern and southern margins of the North China Craton. However, accurate Paleoproterozoic stratigraphic correlation of these two basins still lacks precise chronological and convincing paleontological evidence. Here, we report a SIMS zircon U-Pb age (1647.8 ± 4.3 Ma) from a tuffite layer at the bottom of the Cuizhuang Formation of the Xiong’er Basin, which provides direct chronological evidence for its isochronous deposition with the Chuanlinggou Formation in the Yanliao Basin. Besides, abundant OWMs were recovered from red shales of the Chuanlinggou Formation from the present Taihang Mountains, which is located in the southern branch of the Yanliao Basin and close to the Xiong’er Basin. They are primarily spheroidal microfossils and contain at least one unambiguous unicellular eukaryotic taxa (Valeria lophostriata) and three probable eukaryotic taxa (Schizofusa sinica, Dongyesphaera tenuispina?, large Leiosphaeridia spp.). Our finding further confirms the appearance of unicellular eukaryotes in the Paleoproterozoic ocean and the expanding of their living scopes from the cratonic marginal basin to the intracratonic basin. However, the absence of eukaryotic OWMs in black shales and green shales with more hypoxic depositional waters than those of red shales, indicates that the oxygenated water is probably a key factor to the survival of eukaryotes and even their preservation as OWMs.