作　　者： ; ; (吉学平）; (程海）;

机构地区： 南京师范大学地理科学学院

出　　处： 《中国岩溶》 2007年第4期321-325,共5页

摘　　要： 测定了人类化石地点云南呈贡龙潭山l号洞5个次生碳酸盐样的质谱法铀系年代。其中位于含人牙化石的II堆积层下界面不远处的LTSY-3石笋样质谱^230Th／^234U年龄为（305士15）ka；而其余4个样品经现场地层复核，它们与堆积均缺乏明确的叠压关系，因此认为它们很可能源自洞顶或洞壁石幔。此外，还测定了该地点5个动物化石样的^230Th／^234U年龄，其结果为60～80ka，平行测定了其中3个样品的^227Th／^230Th年龄，二种铀系年龄均在士1．5σ范围内一致，从而支持了该地点骨化石样铀系年代的可信度。在没有进一步的地层和年代证据之前，暂将60～80ka作为含人牙化石的第II层堆积的年代应是合理的。但值得指出的是，由于骨化石中铀循环模式的不确定性，与有明确层位意义的钙板相比，洞穴地点的这类材料年代结果往往偏于年轻，因此上述年代测定结果很可能也存在偏低问题。 Longtanshan cave 1 is located 11 km to the south of Chenggong county, Yunnan province. Two hominid teeth attributed to late Homo sapiens and 12 species of mammalian fossils are recovered from the deposit. Based on classical ^14C dating results and palaeobiostratigraphic correlation, this site was once assigned to the last period of the Late Pleistocene. According to the published reports, there are two intercalated flowstone layers. However, the extant profile shows only scattered speleothem formations, from which five calcite samples have been collected for mass spectrometric U-series dating. The obtained results are too old to be compatible with the palaeobiostratigraphy. Based on the high reliability of the U-series dates on pure and dense speleothem samples, the previous stratigraphy was called into question, which was later proved by our field investigations. So, it is considered that four out of the five samples should be formed from the calcite drapery on cave ceiling or walls, which devoid of stratigraphic context. Only the ^230Th/^234U age on LTSY-3 （305±15） ka, collected from a small stalagmite just below the interface between Layers II and I, can be cited as the maximum age of Layer II and the minimum age of Layer I. To circumvent the above difficulty,^230Th/^234U age determinations are carried out on five fossil bones, yielding dates in the range of 60 and 80ka. Three of them are analyzed in parallel with ^227Th/^230Th method, yielding results consistent within ±1.5σ with those from ^230Th/^234U, which is in support of the limited reliability of fossil samples as temporal markers. For the lack of more robust chronological control, it is reasonable to assign 60-80ka as the time of Layer II from where the human teeth are recovered. However, it should be noted that because of the un-quantification of the post-depositional uranium movement, dates from cave settings tend to be younger than those from speleothem calcites with quantified correlation meaning. So it is very possible that the above time

关 键 词： 龙潭山 号洞 铀系年代 次生碳酸盐 晚期智人

领　　域： [历史地理] [历史地理] [天文地球] [天文地球]