宁夏中南部古生代弧型构造

PALEOZOIC ARCUATE THRUST BELT IN CENTRAL AND SOUTHERN NINGXIA

宁夏中南部地区在中奥陶世至泥盆纪是作为北祁连造山带北侧的弧后前陆盆地靠大陆一侧而存在的;由于在早古生代晚期该前陆盆地的关闭,该地区下古生界变形,发育明显的逆冲推覆构造,形成一个大型的弧形构造,该弧形构造主要由弧形逆冲断层以及相关褶皱所组成,该构造弧顶指向北东,西翼宽、东翼窄,是加里东运动的组成部分,动力方向来自于南南西,即北祁连造山带。而卫宁北山地区的东西向构造仅仅是该弧形构造的一翼。新生代弧形构造是在古弧形构造的基础上形成的,并一定程度上改造了古构造。

In the period from Middle Ordovician to Devonian, the central and so uthern Ningxia area is the back-arc foreland basin in the north continental sid e of North Qilianshan orogen. In the late period of the Early Paleozoic, with th e closure of the back-arc foreland basin, a large arcuate thrust zone, broad in the west but narrow in the east, was produced in the study area, with the compr essive force originating from the southwest, namely, the North Qilian Orogen, wh ile the east-west trending structures in Weiningbeishan area are only parts of this salient. The Cenozoic arcuate structure was formed on the basis of the earl y one, but has changed the early one to certain extent.