郯庐断裂带莱州湾段新生代活动演变及其沉积-改造效应

The activity and post-reformation of Cenozoic Tan-Lu Fault in Laizhou Bay area

本文根据对覆盖区地震、钻井等资料的精细解释和深入剖析,揭示在渤海莱州湾地区郯庐断裂带由东、西两条分支断裂带构成,二者又分别由两条主断层及多条次生断层和其间的断块组成。分支断裂带的两条主断层的间距因地而异,一般在5km左右;其结构构造和空间展布特征有别,西支表现为"两断夹一凸"的不对称地垒式,东支主要呈"花状"构造结构。通过古地质构造恢复和分期动态构造演化分析等综合研究,厘定了在新生代不同时期两条分支断裂带在该区不同单元的活动特点和构造-改造效应,进而总结了郯庐断裂带新生代主要阶段的构造属性及其演变。认为在古近纪早中期,研究区处于区域伸展沉降环境,郯庐断裂带对该区的沉积展布无明显控制作用;断裂带活动的明显控制沉积效应始于古近纪晚期,总体具伸展兼右行走滑属性,主要表现为切割和改造了研究区原近东西向展布的优势构造-沉积格局,同时控制了前期沉积地层的剥蚀强度及其分布范围和同期沉积。新近纪以来,郯庐断裂带两条分支断裂带的活动表现出差异显著的东强西弱;于第四纪,在东支断裂带出现正花状反转构造,可能与幕式走滑兼挤压活动有关。

Based on the latest seismic data,drilling cores and other geological data,this paper reveals the fact that Tan-Lu Fault in Laizhou Bay area are composed by eastern and western branch faults,both of which contain two main faults and other sub fault with faults block between the faults. The gap between the two major faults of the branch fault zones varies from place to place,with average distance of 5km; differences also exist in the structures and spatial distribution features of the major faults,with the western branch showing the asymmetric＂two fault basin with a bulge in between＂,the eastern branch showing＂flower structure＂. After the integrated research of the palaeo-geologic tectonic recovery and the staging dynamic tectonic evolution analysis,we identified the activity features and affection of reformation in different units of the research area by two branch faults during Cenozoic,summarizes the Tan-Lu Fault＇s structure properties and evolution in Cenozoic. The result shows that： the research area turned into a huge extensional structure during the early and middle Paleocene and the Tan-Lu Fault did not control the sedimentation distribution of the area obviously; the fault activity became stronger since Late Paleocene,showing the characteristics of extensional and dextral strike-slip,reformed the original nearly east-west tectonic structure distribution of the research region,controlled the distribution range,synchronous deposit and denudation strength of the sedimentary. Neogene to the present,the two branch faults＇ activity of Tan-Lu Fault showing the obvious weakness from east to west; during Quaternary period,the positive flower inversion tectonics appeared in the eastern branch fault zone,which might be related to the episode movement of strike-slip and extrusion.