河北省平泉—下店子断层的多次活动

THE REPEATED MOVEMENTS OF THE PINGQUAN-XIADIAN FAULT

对于断层多次活动的鉴别,只能通过现存在断层附近残留下来的构造形迹来进行。特别是早生成的构造形迹,在断层后来的活动中往往经受改造,这就对断层活动性质的鉴别造成困难。在野外工作中经常遇到的问题是:如何利用这些现存的构造形迹来说明哪一次的断层活动呢?若断层的某一部分显示一种断层活动性质,而另一部分又显示另外一种活动性质,则这些矛盾的地质现象,经常把人们弄得迷惑不解,甚至把复杂的地质现象简单化,乃至得出错误的结论。 本文试图以河北省平泉——下店子断层的多次活动,对断层多次活动的鉴别提出一点不成熟的看法。

This Paper attempts to discriminate the stages o movements 01 the Xiadian fault. The E-W extending Pingquan--xiadian fault that cuts through the strata of Preambrian-Jurassic period had been involved into many times of moveme in the geological past.The fault has the following important features.1. The syn-depositional faulting in luliang period: the fault was moving in the whole period when the Sinian sub-group and Palaeozoic group were deposited.2. Reverse faulting in Hercynian movement: The fault makes a very small angle with the traction fold occurring in the Sinian sub-group with the acuteengle pointing to the east. The fault shows some expresssion of sinistral tortion.3. The shear faulting in mid Jurassic period shows dextral shearing movement as testified the infiltration of rock bodies along the near by secondavy tension faults.4. The normal faulting in late Jurassic period: It Shows the property of a normal fault as that the strat of upper Jurassic sliding down along the fault plane and developing into many small normal faults.