Sedimentary evolution of borehole PZK14 in western Tangshan area during Late Cenozoic

In order to find out the sedimentary evolution characteristics of loose deposits in the western plain of Tangshan since the Late Cenozoic, the authors in this paper studied the color, particle size, apparent resistivity logging and natural gamma logging of the borehole PZK14 in western Tangshan and divided the sedimentary facies with the calculation of deposition rate of each period , based on the 1∶50,000 regional geological survey in Yahongqiao area. The results show that lacustrine facies, delta facies and fluvial facies are mainly developed in this area during the Late Cenozoic. The delta facies was developed at the beginning of the Early Pleistocene, while the delta facies was transformed into fluvial facies with the retrogradation of alluvial fan in the ancient Luanhe River when the climate began to become warming. Three lake-delta sedimentary cycles developed during middle to late Early Pleistocene. A lake-delta sedimentary cycle developed in the Middle Pleistocene. At the beginning of Late Pleistocene, a thick lacustrine layer was deposited. As the climate became cold, the transgression along the coast of Bohai Bay ended and the lacustrine basin began to shrink and transformed into fluvial facies. The Holocene was dominated by interfluvial depression. According to the sedimentation rate-age curve, tectonic control of the sedimentation in this area has been weak since the Quaternary, and the climate is the main factor affecting the development of sedimentary facies. The sedimentation rate of the Quaternary was relatively fast, and the Olduvai polarity subchron (1.95~1.77 Ma) had the highest sedimentation rate of 194.0 m/Ma. The deposition rate of 2.52~1.95 Ma is the smallest, which is about 111.2 m/Ma. This achievement is of great significance to the restoration of paleogeographic evolution and the geological exploration of hydraulic environment in this region.