两广云开大山—十万大山地区盆山耦合构造演化——兼论华南若干区域构造问题

云开大山自泛华夏造山作用以来就成为褶皱带和相对隆起区,现今的十万大山及其前身则同时成为前缘凹陷或前陆盆地,它们共同组成了一个盆山耦合系统.整个盆山耦合系统的构造演化可划分为如下阶段:早古生代造山事件第一幕(郁南运动)形成云开复式背斜带,古博白前缘凹陷形成于其东南侧.第二幕(北流运动)使云开复式背斜向西北推进,前陆盆地亦向西北侧迁移.第三幕(广西运动)使云开大山继续褶皱隆起,早印支运动(东吴运动)使钦防海槽褶皱成山,并在其北西侧形成前陆盆地.晚印支运动,广西大容山地区褶皱隆起,此时的前陆盆地已迁移至现今十万大山的东南边缘,奠定了十万大山盆地现今构造轮廓的基础.进入燕山期,随着桂东南逆冲推覆构造前缘不断地向NW方向扩展,侏罗纪-白垩纪时期的前陆盆地也不断地向NW方向迁移.进入新生代喜马拉雅期,本区的构造格局发生了重大变革,即由原来的NW-SE向挤压构造应力场变为NE-SW挤压构造应力场.

Evolution of basin-range coupling in the Yunkai Dashan-Shiwan Dashan area, Guangdong and Guangxi:with a discussion of several tectonic problems of South China

The Yunkai Dashan (Dashan means Great Mountains in Chinese) area has become a fold belt or a relative uplift since the pan-Cathaysian orogeny, and meanwhte the present Shiwan Dashan area and its predecessor have become a front depression or a foreland basin. They combine to form a basin-range coupling system. The tectonic evolution of the whole basin-range system may fall into the following stages: the first phase (Yunan movement) of the Early Paleozoic orogenic event gave rise to the Yunkai anticlinorium, with the paleo-Bobai front depression formed at its southeast side; the second phase (Beiliu movement) resulted in northwestward advance of the Yunkai anticlinorium and the foreland basin also migrated toward the northwest side; and the third phase (Guangxi movement) caused the Yunkai Dashan area to continue folding and uplift and the early Indosinian movement (Dongwu movement) led the Qinfang sea trough to be folded into a mountain, with a foreland formed at its northwest side. In the late Indosinian movement the Darongshan area was folded and uplifted and then the foreland had migrated to the southeast margin of the present Shiwan Dashan area, thus laying a foundation of the present tectonic framework of the Shiwan Dashan basin. In the Yanshanian period, with continuous NW-directed propagation of the front of the southeastern Guangxi thrust nappe structure, the Jurassic-Cretaceous foreland basin also migrated continuously in a NW direction. In the Cenozoic Himalayan period, great changes took place in the tectonic framework in the study area, i.e. the original NW-SE compressional stress field changed into a NE-SW one.