关中盆地杨官寨遗址古洪水事件释光测年

通过对泾河下游的野外考察, 在高陵县杨官寨仰韶文化遗址东南部发现夹有典型的古洪水滞流沉积层的全新世黄土-古土壤剖面。利用单片再生剂量法(SAR)测定了40～63μm粒径石英的光释光(OSL)年龄。从剖面获得的样品年龄数值处在2.27±0.06ka到14.26±0.58ka之间, 且与地层深度表现出良好的对应关系。通过样品OSL年龄与其埋深的关系, 结合粒度和磁化率数据地层对比, 以及文化层考古年龄, 确定了该全新世剖面的基本年代框架。研究结果表明, 在4.20～4.00ka泾河流域发生了第一期多次古洪水事件, 在3.20～2.80ka发生了第二期特大古洪水事件。这些古洪水事件与全球性气候突变事件同时发生, 是泾河流域气候水文系统对于全球变化的响应。

OSL dating study on the palaeoflood events recorded in the Yangguanzhai Neolithic ruins in the Guanzhong Basin

On the basis of field investigations along the Jinghe River valley,a typical Holocene loess-soil profile with interbedded palaeoflood slackwater deposits was found at the Neolithic Yangshao Culture site near Yangguanzhai village,Gaoling county.OSL ages for the quarts grains at a size of 40-63 μm were measured by using the single aliquot regenerative-dose(SAR) protocol.The optical ages of these samples ranged from 2.27±0.06 ka BP to 14.26±0.58 ka BP,showing a good relation with the depth in the YGZ profile.According to the age-depth function,the archaeological ages,grain-size distribution and the magnetic susceptibility in the YGZ profile,a Holocene chronological framework is established.The first episode of palaeoflood events is therefore dated to 4.20-4.00 ka BP,and the second episode is dated to 3.20-2.80 ka BP on the Jinghe River.These extraordinary floods occurred during the global abrupt climatic events.They represent a regional response of river system to global change.