菜州湾南岸地貌及第四系发育对区域构造响应

摘要

莱州湾南岸地貌第四系发育受控于气候、基准面及区域构造,沂沭断裂带的新近活动是该区域地貌第四纪发育的影响因素之一.本文通过地形分析、流域水文分析、历史地貌分析、第四系厚度与历史构造分析等方法,对该区域地貌第四系发育与断裂带关系进行了研究.研究表明:(1)研究区地势西高、东低,河流下切深度自西向东依次减小;典型河流河间地比率自西向东增大;分水岭向东迁移.(2)第四系西薄东厚,区域第四系厚度分布受断裂带控制.(3)沂沭断裂带控制了潍北组的区域分布,控制了区域第四纪沉降中心,影响了全新世中期最大海侵范围.第四纪沉降主轴与断裂带之间的几何关系表明沂沭断裂带在第四纪具有右行走滑性质,区域地貌第四纪特征为沂沭断裂带新构造活动提供了地貌第四纪方面的证据.%The Yishu fault zone located in Shandong province is a section of the Tanlu Fault in the eastern China,which consists of 4 faults,and two faults among them along south coast area of the Laizhou Bay were active in Quaternary.Geomorphology and Quaternary of the area were controlled by climate,base level,regional tectonics,and the activity of Yishu fault in particular.Based on data of SRTM3-DEM,1/250000 geological map of Weifang City,and 1/50000 topographic map,this paper studies regional geomorphic and Quaternary characteristics by analyzing topography,drainage,geomorphic evolution,Quaternary depositional thickness and tectonic evolution,and then discusses their relation to the Yishu fault zone.The results show that:(1) The DEM elevation is lowering and the river incision is deepening eastwardly in the region;(2) The interfluves ratio of the interfluve area to the drainage area,a proxy for erosion degree of drainage,is increasing eastward from the Mihe drainage in the west,to the Bailanghe drainage in the middle,and the Weihe drainage in the east,especially under the river net of flowacc ≥ 500;(3) The drainage boundaries migrate from west to east;(4) The thickness of the Quaternary deposit increases eastwardly,and the depocenter is located inside of the east part of the Yishu fault zone.The Yishu fault zone controlled the regional distribution of the Weibei marine and terrestrial interbed Formation,shore line of the largest transgression during the mid-Holocene,and the migration of the depocenter.The geomorphic incline in the area is related to the tectonic tilting created by the Yishu fault zone.Dextral strike-slip of the fault zone is indicated by angle between the main axis of the descendant zone and the Yishu fault zone.We suggest that the tectonic tilting of the area was likely related to the dextral slipping of the Yishu fault.