华北平原北部大厂凹陷第四纪沉积物特征及沉积演化过程OACHSSCD

To reveal the Quaternary sedimentary evolution of the Dachang Depression in the northern North China Plain,and provide basic data for regional Quaternary stratigraphic division,correlation and sedimentary environment research.This article selects the S4 borehole as the research object.By comparing S4 borehole with Quaternary standard borehole S9,the Quaternary stratigraphic framework of the S4 borehole was established,and the sedimentary characteristics was analyzed.Based on the existing research results of boreholes in the Dachang Depression,the sedimentary evolution process of the Dachang Depression along the S4 borehole was preliminarily discussed.The result indicates that the sediments of S4 borehole can be divided into two lithological sections.The 47.1～101.0 m sediments are mainly composed of clay,and the overall particle size is relatively fine,belonging to alluvial lake deposit.The 0～47.1 m sediments can be classified into 4 sets of meandering river sedimentary sequences.The Qp1/Qp2,Qp2/Qp3 and Qp3/Qh boundaries are identified at depth of>101.0 m,47.1 m and 22.9 m,respectively.Before the Early Pleistocene,the study area was dominated by alluvial fan deposits.The Early Pleistocene,the alluvial fan retreated to the area around the S9 borehole.During the Middle Pleistocene,the alluvial events still occurred near the S12 and S9 boreholes,while fluvial deposits developed south of the S9 borehole.The Late Pleistocene,the area was dominated by fluvial deposits.During the Holocene,fluvial deposits developed south of the S4 borehole,while no deposition occurred in the northern region of the S4 borehole.