HORIZONTAL DISPLACEMENT AND EVOLUTION OF THE TANCHENG-LUJIANG FRACTURE

This paper discusses the horizontal displacement of the Tancheng-Lujiang fracture from the view-point of geological and geophysical fields.The displacement amplitude of this major fracture is estimated at 400—550 km.This estimate is based on the reconstruction of the basement tectonics and stratigraphy,late Proterozoic sedimentary basin,facies zones and biotas,and volcanic zones and metamorphosed zones of Precambrian metamorphic belts on both sides of the fracture.The displacement amplitudes of the geological bodies vary with their different physical properties and tectonic positions. The result of the geological inference of the displacement amplitude of the Tancheng-Lujiang fracture is supported by the geophysical field. The Tancheng-Lujiang fracture is a wrench fracture that began to orm in early Yanshanian time.It went through a complex evolution process: Jurassic compresso-shear horizontal displacement→Cretaceous extensional downfaulting→Cenozoic compresso-shear thrusting.Its extent increased with geologic time.Therefore,in studying the formation and evolution of the fracture, it is necessary to deal with the fracture in terms of different ages.It is not advisable to see only its horizontal displacement in Jurassic time,while failng to see its dominantly tensile rift nature in Cretaceotus time,or to admit only the tensile rift nature in Cretaceous time,while negating large-scale horizontal displacement in Jurassic time or failing to study the Jurassic horizontal displacement of the Tancheng-Lujiang fracture.