Chronology of a section of Quaternary speleothems in the Shihua cave, Beijing

Abstract：The Shihua cave is located at the northeastern end of the synformal belt at the edge of the Fangshan granite intrusion in Beijing and faces the Peking Man (Homo erectus pekinensis) site. The strata are composed of limestone of the Middle Ordovician Majiagou Formation formed 460 Ma ago. The basic form of the cave began to form in the Pliocene at 25 Ma BP and the speleothems in the cave began to form in the middle Pleistocene at 0.37 Ma BP. Among Chinese karst caves, the Shihua cave has the largest number of layers and a complete range of speleothems in the caves. There are many large cave stone shields deposited by fissure infiltration water, the superimposed relationship of stalagmites deposited by dripping water is evident, moonmilk deposited by pool water is well developed, and the micro-layering of Holocene stalagmites is clear. The basic form of the cave reflects the history of the neotectonic movement in the Western Hills, Beijing, which may be correlated with the physiographic stage of North China and terraces of the Yongding River; the speleothems in the cave recorded the paleoenvironmental change in the Western Hills, Beijing, since the middle Pleistocene, which may be used to set up a Quaternary section for a correlation with the section of clastic sediments in the Zhoukoudian caves. The calcareous plate has U-series ages of 334.99-366.74 ka, thus named the Gaiban Formation. The wide stalagmites have U-series ages of 169-235 ka and ESR ages of 130-518 ka, which are middle Pleistocene deposits and may be named the Yunshuidong Formation. The rod-shaped stalagmites have U-series ages of 14.9±2.1-100.3±11.1 ka, which are upper Pleistocene deposits, named the Shihuadong Formation. In Holocene stalagmites, there is usually a ~1 μm thick, dark streak between two micro-layers, which serves as a mark for determining the number of micro-layers. Stalagmites with micro-layering have 14C ages of 0.58-2.50 ka and AMS 14C ages of 130±100-670±130 a, named the Shoubeizhidong Formation.