Quaternary Stratigraphic Division And Contradistinction Study Of Langfang City

The study area is located in the north China plain with second-order tectonicsubsidence area---north of Jizhong depression basin. In the study of active faults, theQuaternary stratigraphic framework and evolution of the basin is one of importantresearch topics in the project. The Quaternary stratum in study area belongs to lacustrinestrata with integrated stratum and clearly sequence. The paper explored the preciselocation and characteristics of tectonic activity in the Tongbai fault (F1) and Hexiwufault (F2), base on the analysis and comparison of Quaternary stratigraphic division andthe Quaternary stratigraphic framework.According to the analysis of lithological characters, sedimentary cycles, andsedimentary facies of the borehole, with the comprehensive previous research results,this paper determined the division of lithostratigraphy and sedimentary cycle in studyarea, and proposed division of lithostratigraphy and correlation of the program. Thelithological strata are clear to be classified as middle Pleistocene Yangliuqing group(Qp~2Y), the upper Pleistocene Ouzhuang group (Qp~3O) and Holocene Tianjin group(QhT). Among them, the bottom of Qp~2Y in the dike camp site is not obtained, whichaverage drilling to259.07m， the average depth of Qp~3O is167.85m and the averagedepth of QhT is24.39m; the bottom of Qp~2Y in the smelter venue is not obtained either,which average drilling to242.61m, the average depth of Qp~3O is170.77m and theaverage depth of QhT is27.66m。On the basis of the borehole lithological characters, the data of Thermoluminescent(TL) dating, pollen assemblage analysis, this paper determined the standard of thedivision chronostratigraphic and the division of chronostratigraphic and correlationprogram in study area. According to the data of controlled drilling in the smelter, it isindicated that the bottom of Holocene series is located in26.3m of the controlleddrilling, between the pollen assemblage IV and V; the bottom of the upper Pleistocene islocated in171.4m of the drilling. The time stratigraphic data show that the age of100-105ka is above the interface, and the age of115-120ka is under the interface.Meanwhile the interface is located between the pollen assemblage I and II; on top theinterface, there are two warm periods which roughly corresponds to the Baiyangdiantransgressive and Cangzhou transgressive events. The bottom of middle Pleistocene hasnot been found and the TL dating data and pollen assemblages’ data indicate the presentposition which is still located in the upper of middle Pleistocene. The following conclusions are obtained by comparing strata between some areas ofNorth China (Beijing, Ningjin parked, Handan, Tangshan, Bohai Bay, etc.) andLangfang.The depth and thickness of the Langfang area and the Bohai Bay is closerthan others in the same geological horizon, However，compared with other regions,Langfang shows a large trend in the depth and thickness of Stratigraphic units. Forexample, the depth of QhT and Qp~3O are respectively about in5m and60m inTangshan.In the light of the analysis of the fault-crossing misering of the Quaternary faultacross the DiShang camp drilling site (Tongbai fault) and smelter drilling sites (Hexiwufault), combined with the program by artificial seismic exploration and the petroleumgeology, structural geology, seismic geology and so on, this paper exploded thebreakpoint location at the Tongbai fault (F1) and Hexiwu fault (F2) and thecharacteristics of tectonic activity since the Quaternary achievements. There are severaldisplacement interfaces in the position of middle Pleistocene at Tongbai fault (F1)DiShang camp and Hexiwu fault (F2) smelter drilling site, and showing a graduallyincreasing trend, the difference is mainly caused by the Paleogeomorphology ups anddowns and fault activities.