Tectonic-sedimentary evolution of a continental rift basin: A case study of the Early Cretaceous Changling and Lishu fault depressions, southern Songliao Basin, China

Abstract

The Songliao Basin is a large continental basin in Northeast China; the southeastern part contains many deep grabens and half-grabens that constitute the Changling and Lishu fault depressions. Due to the complex structural-sedimentary characteristics of these deep fault depressions, oil and gas exploration is difficult. Based on abundant seismic, well log and drill core data, this paper describes and analyses the structural morphology and sedimentary fill characteristics of the Changling and Lishu fault depressions in the southern Songliao Basin, revealed their vertical evolution and lateral migration patterns, and finally combines this features with the geotectonic background to clarify the main factors controlling of basin tectonic-sedimentary development in the rift period of the Songliao Basin. The results show that Early Cretaceous mantle activity in Northeast Asia was the source of basin extensional stress and volcanic rock development, which together with short-term regional uplift of the basin controlled the generation, merging and extinction of the fault depressions. Strike-slip activity clearly occurred in the study area, which not only controlled the arrangement of Valanginian to Hauterivian fault depressions but also affected the development of several large Albian faults. Tectonic activity was the most important factor controlling the type of sedimentary fill, which gradually evolved from fan delta-lacustrine facies to braided river facies in the basin. This study provides not only basic geological support for deep oil and gas exploration in the southern part of the Songliao Basin but also a reference for deep structural and sedimentary studies in other continental rift basins.