The origin of the Wenyu River in Beijing

Abstract: The Wenyu River is an important river in northern Beijing plain. The geological background on both sides of the Wenyu River is complex and characterized by serious geological disasters. Geological survey shows that the formation and evolution of Wenyu River were closely related to the Nankou - Sun River fault and strictly controlled by the fault. Drilling shows that the earliest Cenozoic sediments along the Nankou-Baishan section of the Wenyu River were formed in the early Pleistocene, suggesting that the Wenyu River was formed at the early stage of early Pleistocene. The Wenyu River continuously migrated in the Wenyu River Valley, but was confined on the downthrow side of the Nankou-Sun River fault due to the migration of the fracture-controlled bed. The hanging side from Nankou to Machikou formed a depression several hundred meters deep due to subsidence of the hanging wall of the Nankou - Sun River fault, and thick loose sediments were deposited. The Wenyu River is the drainage channel of the long-existent lake in the depression. In the vast area of Cold Spring, Xinzhuang, Gaolizhang and Xinlitun in Changping District, there exists a peat layer containing snail shells a few meters below the surface, which exhibits stratoid and multilayer forms and stably extends for several meters. Analytical results show that the peat layer at the bottom of the 14C is 9930 ± 150 years old whereas the top peat layer 14C is about 3 ka. These data suggest that the lake was shallow and suitable for the growth of aquatic plants ten thousand years ago, and then the lake water gradually diminished. The lake disappeared only a few thousand years ago, which suggests that, although the Wenyu River was formed very long ago, its appearance remains young due to the continuous changes of the river course.