摘要
论述了ESR测年的原理和方法 ,并利用ESR测年方法对祁连山的冷龙岭和走廊南山的摆浪河流域第四纪冰碛物进行了年代测定 .结果表明 ,冰碛物样品的ESR年龄与野外地层对比推测的年龄和和14 C、TL测定的年龄基本一致 ,且同一冰碛物不同位置采集的样品年龄也一致 ,说明本次测定的冰碛物年龄是可信及可靠的 .
It is very difficult to dateglacial deposits. TL, U-series and 14 C dating methods, which are currently usingin Quaternary research, cannotbe used in paleo- moraine dating. Thus there is a great problem for glaciation research. There is a great deal of quartz grain in moraine, which is one of ESR dating materials. After it was buried, theradiation environment of moraine is mainly invariable, and freed from any thermodynamic and dynamical influence of tectonic activity. The study regions belong to continental glacier area, where glaciers flow slowly. The moraine had been exposed under solar radiation for a long time before it was buried. It is reported that signals of Ge center will disappear if a quartz sample is under solar radiation for an hour. Therefore moraine can be dated by means of ESR method. All samples were taken from Mount Lenglongling and Bailang River Basin in the Qilian Mountains, the northeast edge of the TibetanPlateau. The sampling sites are heavyrainfallareasof the Qilian Mountains, where a lot of Quaternary moraines exist. Ge center( g =1.9977) was selectedas calculating center, and the room temperature, X band wave, microwave power of 2mW, 0.1 modulation amplitude, and magnetic field of about 348±5mT were recorded. Linear correlationmethod was applied.Concentrationsof U, Th, K 2 O weredetermined by laser fluorescence, colorimetric spectrophotometerand atomic absorption technique, respectively. AD values were calculated following the method of Bell et al . and calibrated by water content. From the ESR dating and contrasted with TL、 14 Cage, it can be seenthat most of the determined agescoincide with the agesestimated fromstratigraphy geomorphology, except for Samples BL 1, BL 2 and LN 1, which are estimated younger than 5 000 a BP.The agesof the samples collected at different positions of a section are about the same, for example, the Samples LS 9 and LS 10. The age of Sample LS 5 coincides with the 14 Cageof black blue mud material in the same moraine. The age of SampleBL 4 coincideswith the TLageof the loess on the corresponding terrace. These show thatthe determined ages are reliable and credible. But the ESR method seemsnot available for samples younger than 5 000 a BP.
出处
《冰川冻土》
CSCD
北大核心
2000年第4期353-357,共5页
Journal of Glaciology and Geocryology
基金
国家重点自然科学基金!(497310 10 )
教育部基金"祁连山冷龙岭地区第四纪冰川遗迹"资助
