基于磁性地层和沉积地层特征对北京市南口—孙河断裂活动性评估

张晓亮; 张磊; 王志辉; 白凌燕; 蔡向民; 张敬江; 刘振华; 张悦泽; 倪敬波

doi:10.12029/gc20200322

基于磁性地层和沉积地层特征对北京市南口—孙河断裂活动性评估

Evaluation of the Nankou-Sunhe fault activity in Beijing based on the characteristics of magnetic strata and sedimentary strata

摘要

摘要: 南口—孙河断裂是北京平原区一条重要的活动断裂，也是渤海—张家口断裂带的组成部分。本文通过开展钻探和样品测试（古地磁和¹⁴C测年）分析工作，利用沉积相分析和磁性地层学技术方法建立钻孔沉积地层的磁极性年代序列，并对南口—孙河断裂北段进行第四纪以来活动性进行分析和研究。结果表明：南口—孙河断裂北段第四纪以来的活动性变化特征表现为早更新世早期（2.58~0.99 Ma）活动性由强转弱，在早更新世末期（0.99~0.78 Ma）再次转强；中更新世（0.78~0.126 Ma）活动性转弱；晚更新世至全新世（0.126 Ma至今）活动性再次加强。这一规律与北京西山隆升基本特征吻合，活动性总体表现“强-弱-加强”的特点。

Abstract: Nankou-Sunhe fault is one of most importance active faults in Beijing plain and one part of Bohai Bay-Zhangjiakou fault belts. This paper builds magnetic polarity chronology of borehole sedimentary strata based on magnetic stratigraphy and sedimentology with drilling and paleomagnetism and ¹⁴C samples testing, analyses and discusses the active features of NankouSunhe fault in the north segment since Quaternary period. The research indicates that:the fault activity changed from high to low intensity in the early stage of early Pleistocene(2.58-0.99 Ma)and turned into high intensity in the late stage of early Pleistocene (0.99-0.78 Ma), from strong to low intensity again in the Middle Pleistocene (0.78-0.126Ma), and then from low to high again intensity (0.126 Ma-present). This active feature is consistent with west mountain of Beijing uplift which shows the characteristics of high-low-high intensity.

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