A PRELIMINARY SURVEY ON LOESS DEPOSIT IN EASTERN QINLING MOUNTAINS (CENTRAL CHINA) AND ITS IMPLICATION FOR ESTIMATING AGE OF THE PLEISTOCENE LITHIC ARTIFACTS
东秦岭南洛河上游黄土地层年代的初步研究 及其在旧石器考古中的意义*

A large number of lithic artifacts of Pleistocene age have been collected from the Luonan Basin, located in the Eastern Qinling Mountains (Central China) over the past ten years. This area is regarded as one of the most important places for understanding hominid behavior in the recent geological time. However, the lack of suitable dating material and sedimentary records has restricted our investigation of human evolution, behavior, and environmental changes. The Luonan Basin and the South Luohe River catchment contain typical loess sequences, in which lithic artifacts are buried. These deposits can be well dated and used as a proxy record of past environmental change. The loess sequence provides a secure time-scale for dating the associated artifacts, and they also provide a basis for climatic and environmental reconstruction as a background to past human settlement. In this study two loess sections, one located in Shangbaichuan with a thickness of 24.8 meters, and the other in Liuwan with a thickness of 13 meters, have been investigated by an interdisciplinary research team. Our results show that these loess deposits are aeolian in origin with strong weathering process. The loess-paleosol alternations are related with the glacial-interglacial changes of the Northern Hemisphere environment during the Pleistocene. Analyses of the stratigraphy and depositional processes, plus optically stimulated luminescence dating, palaeomagnetic stratigraphic analyses, as well as magnetic susceptibility measurements show that the loess deposit in this region started accumulating at least 1.10 million years ago. There are clear warm/cold and humid/arid alternating phases indicated by loess and paleosol sequences in the Eastern Qinling Mountains during this time. The discovery of lithic artifacts in the lower parts of the loess indicate that early hominids were living in this region at least 0.8 million years ago. The hand-axes and cleavers found in this region indicate that Mode 2 Acheulian tools were distributed beyond the "Movius line" in Eastern Asia. However, more survey and systematic excavation is needed to further understand human evolution, technological behaviors, and environmental changes in this important geographic transition zone in Central China.