Depositional sequence and detrital zircon age spectra from Ediacaran to Early Cambrian at the northwestern Yangtze craton: Implication for the basin dynamics

Abstract

The northwestern (NW) Yangtze craton during the Ediacaran–Cambrian period has been considered a passive continental margin; however, there remains contention regarding the timing and mechanisms of the initiation and evolution of the Mianyang–Changning cratonic rift (MCCR) within the NW Yangtze craton. In this study, we present the depositional sequences and detrital zircon geochronology from seven representative sections of the Ediacaran and Early Cambrian strata in the NW Yangtze craton to determine the onset time and evolution processes of this cratonic rift, along with its tectonic and sedimentary responses. Results indicate that multiple tectonic–sedimentary transitions occurred during the Ediacaran–Cambrian, accompanied by fluctuations in sea level and episodic uplift and erosion of carbonate platforms. Furthermore, the provenance of detrital zircon from the Ediacaran and lower Cambrian reveals substantial regional diversity in the Ediacaran, similarity and poly-cyclicity in the Early Cambrian, and temporal variability between the Ediacaran and Early Cambrian. Meanwhile, the summary plot of the detrital zircons from the Ediacaran and Early Cambrian strata indicates that their native basin is characterized neither by an extensional setting nor by a convergent setting, but rather by a collision background. Based on these depositional sequences and detrital zircon age spectra, and combined with previous studies, we conclude that the onset, expansion, filling, and uplift of the MCCR in the NW Yangtze craton during the Ediacaran to Early Cambrian be resulted from peripheral accretionary orogeny associated with the assembly of Gondwana, rather than a continuation of the breakup of Rodinia.