Palaeogeography and provenance transition of Precambrian–Cambrian unconformity at the southern margin of the North China Craton

Abstract

The Precambrian–Cambrian unconformity boundary is ubiquitous and globally documented, which is of great significance to studying major global scientific issues such as environmental transition, positions of the supercontinent, Cambrian explosion, and global geochemical cycle. However, few studies have been on the palaeogeographic features and provenance changes of the Precambrian–Cambrian unconformity boundary at the southern margin of North China Craton (NCC). This uncertainty hampers us from further understanding the early climate change and plate evolutionary history of the NCC. To improve the knowledge of the palaeogeographic features and provenance changes of the Precambrian–Cambrian unconformity boundary on the southern margin of the NCC, the Luoquan and Xinji formations at the southern margin of the NCC were selected as the research object integrated with sedimentary petrology, trace elements, and detrital zircon geochronology investigation. The results suggest a depositional gap between the Luoquan and Xinji formations. The former is glacial to deglaciation deposits, while the latter is shallow to coastal sediments. Compared with the sedimentary stratum of the South China Craton, the Luoquan Formation lacks at least one transgression and regression cycle. The Xinji Formation has detrital zircon age peaks of 1200, 1100, and 950 Ma, unavailable in the Luoquan Formation. The provenance areas of the Luoquan and Xinji formations have changed, indicating that the provenances of the Luoquan Formation belong to the NCC and part of the provenances of the Xinji Formation belong to the North Qinling Terrane (NQT). The trace element data indicate that the tectonic setting of the Luoquan and Xinji formations has changed from a continental island arc to a passive continental margin. It is suggested that the NCC be involved in the evolution of Rodinia supercontinent, which leads to the change of the provenance and tectonic setting. This research provides an explanation for the Precambrian–Cambrian tectonic history, basin development, stratigraphic correlation, and palaeogeographic reconstruction of NCC.