MULTISTAGE SUPERIMPOSED DEFORMATION AND THE EVOLUTION OF THE NORTHEASTERN MARGIN OF YANGTZE BLOCK

摘要

Multistage superimposed deformation has been discussed systematically based on the progress of the stratigraphic sequences of the northeastern margin of Yangtze Block.The new-discovered first stage deformation of those sequences occurred from the middle Triassic to the end of early Jurassic together with development of regional folding, which was resulted from the deep detachment shearing tending toward NW-WNW. The folds dip to east and fall down toward west, and were superimposed by the main stage folding.Thereafter, a series of folds were developed with axes trending toward northeast.Consequently normal folds occurred on the normal limbs while overturned fold on the overturned limbs during the first stage folding. The detachment or thrust was formed from late Jurassic to early Cretaceous. Due to the uplifting of Dabie and the Wannan Mountains in the north and south sides, the bi-directional thrusting belt was formed by gravity flowing from the Mountains toward the center of the basin along the north side of Xuancheng and south side of Guichi. The deformation geodynamics was discussed simply based on the newly recognized information about the tectonic evolution.