宁夏南部弧形推覆构造带特征及演化

宁夏南部弧形构造带主要由四大弧形推覆构造带组成，总体走向ＮＷ，凸向ＮＥ呈弧形展布，延伸１５０ｋｍ～３００ｋｍ，每带又分为多个逆冲岩席和后缘断陷盆地，构成较典型的盆－山格局，它的形成是由燕山期以来，地幔深部物质的运移或对流，引起上部壳内物质的侧向运动，沿能干性弱的层面滑脱，造成前缘的逆冲推覆和后缘的伸展滑覆，拉伸断陷，地壳随之增厚或减薄，形成盆－山构造体系。

THE FEATURE AND FORMATION MECHANISM OF ARCIFORM THRUST-NAPPE STRUCTURE ZONE OF THE SOUTHERN NINGXIA

The southern Ningxia''s arciform structure zone, extending 150~300km, consists of four great arcuate thrust-nappe structural belts with a convex toward the northeast.Every belt is composed of many thrust sheets and back margin fault basin.They formed typical basin-range structures.Since Yanshanian movement because of movenent and convection of upper mantle substance took place intracrust substance lateral movement, detachment along the layer surface of incompetent, forming thrust-nappe on the front margin while extensional gliding and tensional fault depression on the back margin, accompanied with that the crust was thicker or thinner, at the end the basin-range structure were formed.