北京后沙峪凹陷的第四纪地层划分与构造演化

通过对北京平原北部昌平、顺义、朝阳等区域的多个深孔资料、尤其后沙峪地区G3钻孔资料的深入分析,并开展磁性地层学及孢粉测试成果研究,建立了钻孔的磁性地层序列,结合南口—孙河断裂、顺义断裂以及黄庄—高丽营断裂的活动性研究成果,确定了后沙峪凹陷的第四纪地层格架,分析了凹陷的构造演化过程。结果表明,后沙峪凹陷上G3孔下更新统底界为511.7 m,中更新统底界为175.5 m,上更新统底界为31.6 m。在燕山期晚期,黄庄—高丽营断裂形成,控制了北京凹陷的西部边界,在北东向顺义断裂和北西向南口—孙河断裂共同作用下形成后沙峪凹陷。进入第四纪后,G3钻孔地层在早、中、晚更新世的沉积速率分别为0.198 mm/a、0.255 mm/a和0.243 mm/a;各条断裂活动速率的差异性客观反映出各块体之间的升降特点。由于后沙峪凹陷处于黄庄—高丽营断裂的上盘,同时也是顺义断裂的下盘,因此,断裂间的相互运动在第四纪沉积作用下形成了后沙峪凹陷。

The division of Quaternary strata and tectonic evolution in Houshayu Sag of Beijing

In this paper, a magnetostratigraphic sequence of drill hole was established on the basis of analyzing the deep drill hole data from the northern districts of Beijing plain, such as Changpin, Shunyi and Chaoyang, especially on analyzing magnetostratigraphy and pollen in Houshayu region. In combination with the research onthe activity of Nankou-Sunhe fault, Shunyi fault and Huangzhuang-Gaoliying fault, the authors determined Quaternary stratigraphic framework of Houshayu sag. The results shows that the bottom boundaries of lower Pleistocene, middle Pleistocene and upper Pleistocene of G3 drill hole are 511.7 m, 175.5 m, and 31.6 m respectively in Houshayu sag. In the late Yanshanian period, Houshayu sag was formed by the combined action of NE-trending Sunhe fault, NW-trending Nankou-sunhe fault and Huangzhuang-Gaoliying fault which controlled the western boundary of Beijing sag.In the Quaternary, the variability of the rate objectively reflects the characteristics of rise or fall of the blocks. Housahyu sag located in the hanging wall of the Huangzhuang-Gaoliying fault and the footwall of Shunyi fault were formed by the mutual movement between fracturesduring the Quaternary sedimentation, with the deposition rate of the sag in the early, middle and late Pleistocene being respectively 0.198mm/a, 0.255mm/a, and 0.243mm/a.