26Al/10Be Burial Dating of the Middle Pleistocene Yiyuan Hominin Fossil Site, Shandong Province, Northern China

Abstract

The Yiyuan hominin fossil site is one of the few localities in China where a partial skullcap and several loose teeth of Homo erectus have been discovered. Yiyuan was previously assigned broadly to the Middle Pleistocene by biostratigraphical correlation and ESR/U-series dating. Here, we report the first application of a radio-isotopic dating method to the site. ²⁶Al/¹⁰Be burial dating results derived from two sand samples from the fossiliferous deposits show that the hominin fossils can be confidently dated to 0.64 ± 0.08 Ma (million years ago). The reliability of this age is supported by the zero age of modern fluvial sediment near the cave. Our result is consistent with the age estimation based on biostratigraphic correlation and supports the argument that the Yiyuan and Zhoukoudian Locality 1 H. erectus fossils are contemporaneous. The results presented here, along with other recent chronological studies on Chinese Middle Pleistocene hominin sites, indicate that the time span from 600-400 ka (thousand years ago) is a critical period for human evolution in East Asia. Importantly, this time bracket includes several major climatic changes that would have influenced hominins, both morphologically and behaviorally.

Figure 1

Geographical location of the Yiyuan hominin site. (a) Location of Yiyuan and some other contemptuous Mid-Pleistocene Homo (circles) and H. erectus (squares) sites in China, the sites are: 1. Xujiayao; 2. Zhoukoudian locality 4; 3. Jinniushan; 4. Miaohoushan; 5. Dali; 6. Lingjing; 7. Chaoxian; 8. Panxian Dadong; 9. Maba; 10. Panlong Cave; 11. Zhoukoudian locality 1; 12. Chenjiawo (Lantian); 13. Bailong Cave; 14. Hexian; 15. Tangshan. (b) Topographic map of the adjacent region of Yiyuan site, the white solid line marks the boundary of the drainage area of Ciyu River, the dashed line indicates a boundary between different base rock outcrop zone in the drainage area, the northern part is Paleoproterozoic granite while the southern part is Ordovician limestone. (c) Image showing the location of two human fossil-bearing localities of Yiyuan site, and the sampling position of YYB-0. Maps in a and b were generated using Global Mapper (www.bluemarblegeo.com) based on free ASTER GDEM v2 worldwide elevation data (http://glcf.umd.edu/data/aster/), image in c was from Google Earth & Digital Globe.

Figure 2

Stratigraphy and sampling information of Yiyuan Locality 1. (a) Sketch cross-section depicting the shielding condition of the dating samples. As shown, the samples were ~2.5 m deep from the current cave entrance and were vertically shielded by >21 m of limestone (distance measured by portable laser range finder). (b) A photograph taken in front of the cave entrance by one of the authors (H.T.). (c) Stratigraphy and sampling spots of Yiyuan Locality 1 (modified after ref.).