Back-arc tectonic tempos: Records from Jurassic–Cretaceous basins in the eastern North China Craton

Abstract

Magmatic and structural tempos have been recognized in continental magmatic arcs, such as Cordilleran and Andean arcs. However, it remains unclear whether similar tempos or episodicity occur in back-arc settings, knowledge of which would be crucial for understanding back-arc geodynamics. The western Liaoning (WL) region in eastern China contains well-preserved basins of Jurassic–Cretaceous age and provides an opportunity to investigate back-arc tectonic processes. We present stratigraphic, structural, and geochronological data from the WL region to constrain tectonic evolution during the Jurassic–Cretaceous. The results show four stages of rifting or extension during 190–168, 167–137, 136–97, and 96–70 Ma, indicating a duration of 20–40 Myr for each extensional stage. Aside from a magmatic lull at 96–70 Ma, volcanism was associated with each of the three earlier extensional stages. Each main period of volcanism had a duration of 10–20 Myr, with the main eruption events occurring on an average cycle of ~25 Myr. The Jurassic–Cretaceous extension and rifting were interrupted by three compressional events at 168–167, 137–136, and 97–96 Ma, as evidenced by angular unconformities, basin inversion, and structural shortening. Each episode of compression lasted for ~1 Myr, on a 30–40 Myr cycle. The results indicate tempos in both back-arc stress state and magmatism. The back-arc tectonic evolution was characterized by frequent alternation of long-lived extensional and short-lived compressional events, and the back-arc magmatism in all cases occurred in an extensional setting. The back-arc tectonic tempos can be explained by a slab-driven model involving control by alternating phases of slab rollback and retreat on back-arc stress states and magmatism.