New Progress in the study of Quaternary geology in Beijing Plain

Beijing plain, located in the piedmont alluvial fan area, has lots of lakes and rivers in its administrative area. Because of the variability of sedimentary environment, the three-dimensional structure is very complex. Due to the complexity of the threedimensional structure of the Quaternary strata, the Quaternary stratigraphic division is relatively difficult to some extent. Some researcher have established the lithostratigraphic units such as Nihewan Group, Zhoukoudian Group and Malan Group based on some geological data from different sources. These stratigraphic units are mainly based on fossil pollen, foraminifera, and Ostracoda in sedimentary sag drill holes, and a small amount of paleomagnetic data, and are actually the chronostratigraphic units. Because the units are not uniform and the identification mark is not clear, it is difficult to get a broad consensus. In the past 10 years, the increase of the accumulation of data, the understanding of the three-dimensional structure of the Quaternary, and especially the popularity of the ancient magnetic prospecting technology have laid the foundation for the division of the Quaternary strata in Beijing plain. Based on paleomagnetic data from more than 40 drill holes, the authors initially established the bottom boundaries of lower, middle and upper Pleistocene series. According to the engineering geological prospecting, hydrogeological drilling, archaeological excavations and peat investigation materials, the authors compiled a Holocene isopach map for Beijing Plain.