THE TECTONIC FRAMEWORK IN THE NORTHERN PIEDMONT AREA OF THE DABIE MOUNTAINS

Tectonically the northern foot of the Dabie Mountains is also called the North Huaiyang tec-tonic belt. It is separated from the Dabie orogenic belt to its south by the Tongbai- Moztan fault. The tectono-stratigraphic units exposed in the area include the Shangcheng Group（Pz₁）,WinyangGroup（D） ,Carboniferous and Jurassic, Study indicates that the tectonics in the northern piedmontarea of the Dabie Mountains is represented by a thrust nappe system composed of the Xinyang-Shucheng overthrust fauit（as a sole fault）and a series of secondary thrusts and slices. The stratainvovedin the hanging wall and footwall of the overthrust underwent three phases of folding dur-ing the Late Carboniferous and Late Jurassic（the foiding of the first and second phases resultedfrom compression , while that of the third from shear）. The thrusting was north-vergent with avergence of about NE 20-30℃。 The thrusts developed toward the foreland in the form of a trailingimbricate fan. The formation time was Middle to Late Jurassic. The formation mechanisrn wasbackthrusting and closely related to the southward ductile shear decoupling motion of the bulkpart of the Dabie orogenic belt.