Abstract:

There are little systematic researches on the kinematics of the foldthrust zones in the western Yangtze Area. In this paper, based on preview papers, field surveys, geological explanation of seismic reflection profile and tectonic dating, the kinematics of the foldthrust zones in the western Yangtze Area has been studied elaborately. The results show that there are at least three different regional stressfields in the western Yangtze Area since the Indosinian Epoch, i.e. compressions with the NWSE direction, the SN direction and the NESW direction. Among them, the compression with NWSE direction occurred several times at the Late Indosinian stage, at the Early Yanshan stage and at the Late YanshanHimalaya stage; the compression with SN direction mainly happened at the Late Yanshan stage; and the compression with NESW direction, leading to intensive deformation within interior basin, mainly occurred at the Late Himalaya stage. Moreover, the kinematics models from orogenic belt to foreland foldthrust zone have been analyzed in four structural provinces in the western Yangtze Area. The Longmenshan orogenic belt holds the typical characteristic of a complex thrustnappe system consisting of a rootbelt, a middlebelt, a frontbelt and an outsidebelt. The Michangshan and Dabashan orogenic belts lack the middlebelts; and the Xuefengshan intracontinental foreland basin system has the deformation characteristics that the frontfaults have propagated for a long distance in the direction of dip and affected for a large scale in the direction of strike. The characteristics of the kinematics of the foldthrust zones determined the petroleums movingdirections and gathering places in the western Yangtze Area.

Key words: regional stressfield, deformation stage, kinematics configuration model, foldthrust zone, western Yangtze Area