Geodynamics of East Asia marginal sea basins: Stress field modelling

Abstract

The East Asian marginal sea basins (EAMSB) are located at the junction between East Asia and the western Pacific plates, displaying a typical NE-trending en echelon pattern. Their formation is closely related to intense marginal extensional deformation since the Cenozoic. Owing to their intricate geological architecture and varied mechanisms of formation, these basins have emerged as a research hotspot in Earth science. However, due to limitations in geological observations and uncertainties in traditional tectonic models, the formation mechanisms of marginal sea basins remain highly controversial. This study integrates multi-source observational data and 3D spherical shell finite element method to systematically investigate the formation and evolution of the EAMSB, particularly focusing on their NE-trending en echelon pattern. The results indicate that the basin development in this region is primarily controlled by the far-field compressional stress generated by the India–Eurasia plate collision zone, as well as the extensional and radially downward shear stress imposed by the subduction of the Pacific and Philippine Sea plates. In addition, the episodic changes in regional tectonic stress play a key role in the formation of the EAMSB. The model delineates three principal evolutionary stages of the EAMSB: 1. In the early Eocene, the subduction of the Izanagi-Pacific ridge induced surface extension rather than compression along the eastern Asian margin due to shell bending. Meanwhile, under the combined influence of the India-Eurasia collision, rifting occurred along the East Asian margin. 2. In the late Eocene, the transition to subduction toward the Pacific Plate and the arrival of the Philippine Sea plate intensified boundary loads, triggering tectonic reversal and localised stress concentration. Simultaneously, as the India-Eurasia convergence zone entered the “hard collision” period, rifting was further facilitated. 3. From the Oligocene to early Miocene, the subducting plate became older and colder, with a steepening subduction angle, while the India–Eurasia collision continued. The rollback of the subducting plate induced eastward extension, which favored the development of eastward extensional deformation and led to the formation of a NE-trending en echelon pattern of the EAMSB.