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.