泥河湾陆相沉积物光释光年代学研究及其对古湖泊演化的指示意义  

OPTICALLY STIMULATED LUMINESCENCE DATING OF TERRESTRIAL SEDIMENTS IN THE NIHEWAN BASIN AND ITS IMPLICATION FOR THE EVOLUTION OF ANCIENT NIHEWAN LAKE

作　　者：年小美[1,2] 周力平[1] 袁宝印[3] 

机构地区：[1]北京大学地理系,地表过程分析与模拟教育部重点实验室,北京100871 [2]中国科学院古脊椎动物与古人类研究所,北京100044 [3]中国科学院地质与地球物理研究所,北京100029

出　　处：《第四纪研究》2013年第3期403-414,共12页Quaternary Sciences

基　　金：科技部科技基础性工作专项项目(批准号:2007FY110200)资助

摘　　要：对泥河湾盆地郝家台、后沟、红崖和虎头梁4个地点湖相及其上覆沉积物样品进行了光释光年代学研究。由于中粒石英的单片再生剂量法所测光释光信号已经达到了饱和，故采用中粒混合矿物的红外激发后高温红外激发方法，并对其异常衰退进行校正，这种方法利用长石的释光信号，饱和剂量较高，且异常衰退较小，为测量老样品提供了可能性。根据红外激发后高温红外激发光释光测年结果，郝家台、后沟和红崖地区现存泥河湾湖相顶部沉积物年龄为360～420ka，虎头梁湖相顶层沉积物年龄为约270ka，而郝家台和后沟湖相沉积物上覆黄土一古土壤年龄分别为约130ka和180ka。这些测年结果表明在泥河湾地区湖相沉积物顶层及其上覆沉积物之间广泛存在一个沉积间断，且不同地点湖相沉积物侵蚀的程度不同。因此，推测现在泥河湾地区出露的湖相沉积物顶层并不是当时古湖泊消失时的沉积，即至少部分古湖泊沉积的顶部已被侵蚀。Nihewan Basin,located in Hebei Province of Northern China, possesses thick Quaternary sedimentary records, abundant fossils and artifacts land represents a place of the earliest human presence in north East Asia. However, there have been limited absolute dating methods applied on ancient Nihewan lacustrine sediments. In this study, optically stimulated luminescence（OSL）dating technique was employed to date eight samples which were collected from the uppermost parts of the lacustrine sedimentary sequences and overlying loess-paleosol deposit at Haojiatai （ 40°13＇01.75＂N, 114°38＇00.8＂E）, Hougou （ 40°13＇26.4＂N, 114°40＇48.6＂E）, Hongya （ 40°08＇03.2＂N, 114°39＇08.7＂E） , from the upper lacustrine sediment and the lower part of Hutouliang section （ 40°09＇55.5＂N, 114°40＇53.6＂E）. The geomorphological evolution of Nihewan Basin was discussed. Medium-grained（45 -63μm）quartz and polymineral fraction were extracted and used for equivalent dose estimation. Quartz OSL signals of the samples encountered the problem of saturation using single-aliquot regenerative-dose （SAR） protocol. Recent studies have identified that infrared stimulation of feldspar at elevated temperature can reduce the laboratory fading rates in the blue region of the spectrum, so the post-IR IRSL SAR protocol with higher saturation dose and less fading（ Buylaert et al. [633 ,2009）was applied for age determination. The samples were preheated to 250℃, IR stimulated at 50℃ and post-IR IRSL stimulated at 225℃ for the natural/regenerative dose and test dose. Anomalous fading of the post-IR IRSL signal was corrected using Huntley and Lamothe fading correction model. The results showed that anomalous fading-corrected ages of the uppermost lacustrine sediments at Haojiatai and Hougou were 418±25ka and 363±14ka, and corresponding overlying units were 131±5ka and 180±5ka, respectively. The corrected age of the sample was 401±26ka at Hongya＇s top layer of lacustrine sediment. For

关 键 词：泥河湾 湖相沉积物 红外激发后高温红外激发方法 长石信号 古湖泊演化 

分 类 号：P534.63[天文地球—第四纪地质学] P597.3[天文地球—古生物学与地层学]