云南西畴仙人洞动物化石铀系年代

本文报道晚期智人地点云南西畴仙人洞动物牙化石的铀系测年结果。4个样品的230Th234U年龄范围为47—105ka，测定了其中2个样品的227Th/230Th年龄，结果与230Th/234U法的一致。在没有进一步的地层和年代证据的情况下，将西畴人牙化石的年代暂定为47—105ka或许是合理的。但洞穴地点骨化石铀系年代总体偏年轻，上述年代范围很可能被低估。本文结果与我们已有研究的广西通天岩、前洞等地点一致，是晚期智人在我国出现比原认为的早得多的又一例证。

U-SERIES DATING ON FOSSIL TEETH FROM XIANREN CAVE IN XICHOU,YUNNAN PROVINCE

Xianren Cave, located ca. 300 m southeast to the town of Xichou County, Yunnan Province, is one of the numerous modern Homo sapiens cave sites in southern China. From the deposits inside the cavern, 5 hominid teeth together with an abundance of mammalian fossils representing 32 species have been recovered. We have tried to date the flowstone layers covering the fossiliferous deposits, but failed to obtain meaningful results because of their mediocre quality and low uranium contents. Then 4 fossil teeth were selected from the museum collection. Judging by the adhered matrix deposits, 3 of them (XRD-1, 2, 3) should come from the Middle Layer, from which the hominid teeth were be-lieved to come, while another one (XRD-4) may come from the Upper Layer. 230 Th/ 234U dating was carried out on all the 4 samples, yielding resultsin the range of 47 Ka and 105 ka. Independent 227Th/230Th determinations on XRD-2 and 4 gave results consistent within errors with those from 230Th /234U. It seems thus plausible to attribute the hominid teeth in a range of 47 —105 ka. However, compared with the well established U-series dating of speleothem calcites, the U-series dates on fossil materials tend to be much younger. So it is highly possible for the above dates to be underestimated. In any case, the present results are in line with those from other modern Homo sapiens sites we have previously studied, indicating that the appearance of modern humans in southern China may be an event as early as in West Asia and South Africa.