An outline of the pre-Jurassic tectonic framework in east Asia

Abstract

A great transformation of intense tectonism, including extension, compressive shortening, shear deformation and displacement, especially the large scale horizontal strike-slip fault dislocation has occurred in east Asia since the Jurassic. These processes deeply reformed the tectonic framework of the pre-Jurassic. Tectonic evolution of the east Asian Jurassic can be divided into three stages: sinistral shear disintegration caused by faulting from the late Triassic to the early Cretaceous, oblique subduction and extensional departure from the late Cretaceous to the Eocene, and development of marginal arc structures from the Eocene to the present. Transcurrent faulting played a most important role in reformation of the pre-Jurassic tectonic framework. There are three major transcurrent fault systems: the Tancheng-Lujiang (Tan-Ju) fault system, the Median Tectonic Line fault system and the Red River fault system. From the late Jurassic to early Crettaceous, an N.E.-trending shear margin emerged and was closely related to motion of the oceanic plate. Evolution of the northwest margin of the Pacific occurred as follows: passive margin (T 3-J?)→shear margin (J 3-K 1)→oblique subduction margin (K 2-E 2)→subduction margin (E 2-present). There are four plates: the Siberian Plate, the Sino-Korean Plate, the Yangtze Plate and the Indochina-South China Sea Plate, which trended roughly east-west in the pre-Jurassic from north to south. The Japanese Islands might consist of a pieced-together tectonic unit, which was sliced by transcurrent faults and brouht from the marginal zones of the above plates to its present-day position.