Age of newly discovered Paleolithic assemblages at Liuwan site Luonan Basin, central China

摘要

The Luonan Basin contains thousands of stone artifact scatters located in the upper drainage of South Luo River, central China. Despite many years of survey, the age of these Paleolithic artifacts remained uncertain. In 2007, our team established for the first time a chronological framework for the natural loess deposit at locality 1, at the site of Liuwan. Here we report on two in situ artifact assemblages buried in loess deposit which were excavated at Liuwan localities 2 and 3 in 2009. The characteristics of these two Paleolithic assemblages are similar: the stone artifacts are small, and include stone hammers, cores, flakes, chunks, debris, and a small number of retouched tools, represented primarily by scrapers and points. We dated the loess-paleosol sequences at the two new localities, established chronology on the basis of stratigraphic analysis and comparison of magnetic susceptibility profiles between localities 1, 2, and 3, and the typical loess-paleosol time series. Our results suggest that the artifact bearing layer 2 at locality 3 is in the S5 SS2 paleosol unit, dated to between 575 and 568 ka; the artifact bearing layer 1 at localities 2 and 3 is in the soil unit S5 SS3 dated to between 625 and 581 ka. This result suggests that hominin occupation of the Luonan Basin occurred between 625-581 ka and 575-568 ka, there is a probable change in raw materials exploitation from vein quartz in the artifact layer 1 to a mixed vein quartz and quartzite in the artifact layer 2. The Liuwan site is chronologically similar to the Qiaojiayao site in the middle of South Luo River, and indicates that the hominins ranged widely in the Qinling Mountains during the Middle Pleistocene.