郯庐断裂两盘走滑错移构造复位的地层新依据

The new stratigraphic evidence for structural reconstruction of strike-slip shifting of two sides of Tanlu fault

郯庐断裂被认为是大型左行走滑断裂带以来,经多年研究已成为研究程度相当高的构造带。因其两盘构造复位依据粗略,长期存在争议。对断裂两盘构造复位所提出的地层新依据,来自怀远运动推进方向的独特性,现已查明,它是一次由南向北逐次推进的翘板式差异性抬升,三山子组南北向巨型白云质地层穿时体,实为该运动推进全程的完整沉积记录。三山子组底界南部从张夏组顶面→中部从寒武系顶面→北部从亮甲山组顶面依次有序升高,从而在张夏组与下马家沟组之间的不同时期地层,出现了毗邻不同岩相带南北相间,同一岩相带东西延伸的现象。经地层与岩相特征的对比分析,郯庐断裂两盘间,大连与莒县—新泰、白山—本溪与唐山原分别为东西一线2个时期不同深水槽盆的中心带。这2个构造复位的地层标志层层位准确,厚度不大且特征鲜明。据其复位断层两盘经向(南北)错距,南部(大别山-苏鲁超高压变质带)500km,据地层依据的错距中部440km,北部210~310km,表明断层东盘盘内有南小北大的推覆缩距。

Tanlu fault zone have been studied for several years and have become high research level tectonic belt since it was believed to be a large sinistral strike-slip fault.This paper provides a new stratigraphic evidence on structural reconstruction of two sides of the fault,which seems to have resulted from peculiar marching direction of Huaiyuan movement.According to identification,San-shanzi Formation as a large-scale dolomitic diachronous stratum distributed from south to north resulted from the diverse uplift with warped plate style from south to north by Huanyuan movement,and completely recorded the whole pushing process.The lower boundary of Sanshanzi Formation orderly started to rise,and successively overlay the top surface of Zhangxia Formation(Mid-dle Cambrian),Fengshang Formation(Upper Cambrian)and Liangjiashan Formation(Lower Ordovician)from southern part to cen-tral part,then to northern part,which caused different adjacent lithofacies in south-north direction and the same lithofacies extend-ed ineast-westdirection between Zhangxia Formation and Xiamajiagou Formation.Two sides of the Tanlu fault(Dalian and Juxian,Xintai;Baixian,Benxi and Tangshan)were central zones of two deep-water trough basins,as shown by contrastive analysis of strati-graphic and lithofacies characteristics.The two key beds with small thickness have accurate horizon and obvious characteristics for structural reconstruction.The staggered distance of two sides of the reset fault is 500km in the southern part(Dabie Mountain-Sulu ultrapressure metamorphic belt),the staggered distance of the central partis 440km,and that of the northern part is 210-310km,which indicates that the overthrust shortening distance is small in the southern part and is large in the northern part on the eastern wall of the fault.