CAVE DEVELOPMENT AND ENVIRONMENTAL BACKGROUND FOR HOMININ OCCUPATION AT HUALONGDONG CAVE, DONGZHI, ANHUI PROVINCE

The Hualongdong cave, located in Pangwang villege, Yaodu town, Dongzhi County of Anhui Province at latitude 30°06′34.1"N and longitude 116°56′54.2"E, and 40 m above sea level, was discovered in 2006, where unearthed Homo erectus skulls, stone artifacts, and large number of animal fossils. The cave bears great significance on the study of human evolution, lithic technology, and adaptive behaviors of human in South China and has therefore raised great attentions from the public and scholars. Preliminary U- series dating and study of mammalian fauna assemblages indicate that early hominin colonized the site most probably in Middle Pleistocene. This paper devotes our work on regional geology, cave development and mammalian fanua, and analyzing data of clay minerals and oxides from sediments. The cave, as part of the Yangtze stratigraphic region, is geologically situated in the transitional zone between the stratigraphic subzones of the Lower Yangtze and the South of Yangtze. The cave is developed in the stripped micrite limestone of the Tushan Formnation, Middle Cambrian. The site and its adjacent area are dominated by low mountains, gentle hills and lake plains. The cave is formed by the movement and dissolution of fracture water along the verticle fissures in the early stage, and then by horizontal water movement later on for further karst development. The entrance of the cave opens to the southwest with few deposits in the cave, while a karst depression was developed outside the cave. Due to the collapse of the stone outside the current entrance of the cave, abundant sediments including breccia and red clay are deposited within the depression, with a total thickness of more than 4 m. Gravity is the predominate agent of deposition. Human fossils, stone artifacts, and animal remains are recovered from the layers 3 and 4 at the lower part of the section, with a total thickness more than 2 m. In order to reconstruct the environmental background and the impact of human activities, systematic analysis of the mammalian fauna, clay minerals as well as oxides from sediments have been carried out by the authors. It is inferred that the climate and environment were warm and humid then to some extent, and favorable for human survive, as a typical climate background on the north margin of the north subtropical zone. It should be noted that human fossils, stone artifacts, and mammalian fossils are mainly distributed in the layer 3 and 4 of breccia or the lower part of the section, of which the environment was relatively cooler and drier than the environment of the upper part of the section. The climate and environment were optimal to flourish of grass, bamboo grove, and forest, as well as animals, which might lead to the intensified occupation of early hominins during the period while the layers 3 and 4 was formed in Middle Pleistocene. In brief, for study of human occupation of the region during Middle Pleistocene, the Hualongdong cave may provide significant information.