Cretaceous anomalous subsidence and its response to dynamic topography in the Songliao Basin, Northeast China

Abstract

To understand the formation mechanisms and evolution of the Songliao Basin, we applied backstripping and strain rate inversion methods to 20 wells and reinterpret two seismic sections in the Songliao Basin. The obtained data were used to reconstruct the tectonic subsidence history and further assess the potential subsidence mechanisms of this area. The predicted post-rift subsidence based on the uniform stretching model that followed earlier lithospheric thinning events was much lower than the subsidence provided by backstripping. The anomalous subsidence during the post-rift stage was between 200m and 800m in the Songliao Basin, and the depocenter of anomalous subsidence moved eastward between ca. 110 and 80Ma before returning to the west between ca. 80 and 65Ma. Regional variations in the subsidence rates suggest a possible deficit in the negative buoyancy (mantle loading) that is induced by the sinking slab beneath the Songliao Basin. In addition, the anomalous post-rift subsidence was primarily driven by downward drag pressure from the subducting western Izanagi slab and asthenospheric mantle flow beneath the Songliao Basin. The basement rifting in the Songliao Basin during the early Cretaceous and the normal faulting that occurred during the post-rift stage resulted in a secondary contribution to the anomalous post-rift subsidence. Unlike the Songliao Basin, several early Cretaceous rift basins south of the Yanshan Belt were only filled during the syn-rift subsidence, and the anomalous post-rift uplift of the Yanshan belt was driven by deep mantle flow.