一个从两端向中间生长的背斜:台湾西部麓山带八卦山背斜

One Anticline Developing from Two Ends to the Center:Baguashan Anticline in the Western Foothill of Taiwan Orogen

八卦山背斜位于台湾西部的逆冲褶皱带,总体生长是从北向南发展的。由于该地区滑脱面锦水页岩的倾角在走向上有很明显的变化,南北两端小,中部倾角大;因此随之卷入褶皱的地层在走向上也发生明显的变化,造成该背斜形成两端向西突出以及中部窄而两端宽的平面形态。由于在该背斜两端均受到边界构造的控制(可能是侧断坡),因此背斜的生长受到限制,早期主要从北向南,晚期主要从南向北,这样的发育过程可以很好的解释背斜的平面特征、轴面分布特征以及不同部分的形成机制,八卦山背斜内部的发育有其自身独特的方式。

The Baguashan anticline is located in the western thrust-and-fold zone of Taiwan orogen. As a whole, the growth of this anticline is from the north to the south. However, because the dips of the detachment fault along the Jinshui shale vary along the strike, which are smaller at two ends of anticline and larger in the central part, the strata deformed in the fold also vary along the strike obviously. All these result in the plan shape of Baguashan anti- cline whose two ends convex to the west and are wider than the central narrow part. Furthermore because of the controls of structural belts （ maybe lateral lamps） along two ends of anticline, the growth of the anticline is limited. In the early time, the anticline grew from the north to the south, and in the later time it grew from the south to the north. This process of growth can well interpret the plan shape, the characteristics of fold axis, and the mechanics of different parts of Baguashan anticline, so the development of the Baguashan anticline has its own special character.