渝南—黔北奥陶系五峰组的同生变形构造及其地质意义

Contemporaneous Deformed Structures in Ordovician Wufeng Formation in Southern Chongqing and Northern Guizhou,and Its Geological Significances

重庆綦江奥陶系五峰组中—下部的黑色页岩中发育有一系列主要由阶梯状断层和其间的小型褶皱构成的同生变形构造(contemporaneous deformed structures),并可大致分为3个构造层段。沉积后—固结成岩前所形成的同生变形构造层之上为正常沉积的黑色页岩层。另外,在贵州桐梓五峰组距底部2.3m左右的黑色页岩中也发育有与綦江地区相似的、以小型褶皱为主的同生变形构造层,且此同生变形构造层上下为斑脱岩层。同生变形构造的发现,表明渝南—黔北地区奥陶纪晚期(五峰期)的沉积盆地为非平坦的古地貌,且曾发生过多期可能与火山运动相关的构造运动。

The contemporaneous deformed structures,which were formed between post-deposition and pre-diagenesis,are found in the black shales in the Wufeng Formation of the Ordovician at Qijiang,southern Chongqing and Tongzi,northern Guizhou. The contemporaneous deformed structures in the lower—middle Wufeng Formation from Qijiang is composed of graded-faults and small-sized folds and is overlaid and underlain the normal sedimentary black shales; and it can be re-divided into three structural layers. In addition,a contemporaneous deformed structure on and under the normal black shales is mainly composed of small-sized folds in lower Wufeng Formation （at 2.3m from the bottom of the Wufeng Formation） at Tongzi. And a bentonite layer is separately on and under the deformed structures and between deformed structures and black shales. The contemporaneous deformed structures in the Wufeng Formation indicated that the basin might be an uneven paleogeography during the Late Ordovician in the Chongqing—Guizhou area,and happened multistage tectogenesis that possibly associate with volcanic activities.