江苏溧水神仙洞动物化石的铀系年代

Uranium-series Dating on Animal Bones Discovered in Lishui,Jiangsu Province

神仙洞是江苏境内最早发现人类化石的地点。报道该地点动物化石的铀系测年结果,4个样品230Th/234U年龄范围为7～109ka,测定了其中2个样品的227Th/230Th年龄,结果与230Th/234U法的一致,支持年代数据的可信度。暂将神仙洞含化石堆积的年代定为7～109ka,跨度至少100ka,应比原认为的整体距今～10ka合理得多。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,含化石堆积底界因此更可能属中更新世晚期。人颞骨化石被认为出土于第I钙板层之上,应为晚更新世末期或全新世早期。用Gamma能谱铀系或AMS14C测年,应可进一步确定人化石的年代。

Shenxian cave, located at ca. 21 km southeast to the town of Lishui county, is the first anthropologic site discovered in Jiangsu Province, eastern China. We present ^230Th/^234U dates, ranging from 7 to 109 ks, on four mammalian fossil bones from museum collections of the site. Independent ^227Th/^230Th determinations on two Of them give results consistent within errors with those from ^230Th/ ^234U, which is in support of the reliability of the obtained results. It is thus more reasonable to attribute the fossiliferous deposits to the above range, indicating a time span of at least 100 ks, than the previous estimate at -10 ks. However, in a cave setting compared with pure and dense speleothem calcites, fossil materials generally give younger U-series dates, So we tend to consider that the lowermost boundary of the cave＇s fossiliferous deposits should be late Middle Pleistocene in time, while the uppermost strata where the hominid fossil is believed to come from should be formed at the end of Late Pleistocene or in early Holoeene. The application of non- destructive gamma spectrometric U - series or direct AMS ^14C dating may further constrain the age of the hominid fossil.