摘要
可靠的14C测年材料是建立高精度年代序列的前提。在陆生植物残体缺乏的沉积类型中或某一沉积层位,利用其他14C测年材料可能会影响测年结果的精度。而陆生植物孢粉广泛存在于各类地质载体中,利用其浓缩物定年是解决这一问题的途径之一。文章综述了不同沉积类型孢粉浓缩物的提取方法及其测年结果的验证;成功提取了秦岭太白山高山湖泊大爷海表层沉积物中的孢粉浓缩物,其AMS14C定年结果与全有机质年代对比表明高山封闭湖泊孢粉浓缩物能够提供较为可靠的年代估计且在一定程度上能避免碳库效应的影响;但仍需对湖泊岩芯多个层位开展多种测年材料(如陆生植物残体、炭屑、有机质)的对比定年研究以做进一步验证。基于前人及本研究提取经验,归纳总结出适用于湖泊沉积、泥炭沉积、黄土-古土壤序列以及冰楔冰中孢粉浓缩物的提取流程,主要分为前期的孢粉富集(酸碱法)和后期的纯化处理(化学法、镜下挑选与重液浮选),并梳理了目前孢粉浓缩物在定年应用中需要注意的问题。探索沉积物孢粉浓缩物提取的新方法、改进并简化其现有提取流程、提高孢粉浓缩物提取效率(短时间内获取足量的、高含量的陆生植物孢粉),将极大地促进孢粉浓缩物定年方法在晚第四纪年代研究中的应用。
Chronology is the basis of the paleoenvironmental and paleoclimatic studies,while radiocarbon dating is one of the most widely-used methods in Late Quaternary studies to build up independent chronologies.Reliable ^(14)C dating materials are the prerequisite for obtaining the high-precise ages.However,the lack of sufficient terrestrial plant macrofossils in some sedimentary types or at a certain layer restricts the precision dating.Pollen grains are widely preserved in various sediments which provides alternative materials for measuring the robust dates.This paper reviewed the former studies on exploring the extraction methods of pollen concentrates from various sediments and the validations of their dating results.Furthermore,here we also present a case study on enriching pollen concentrates from a closed alpine lake sediment for AMS ^(14)C dating.Two different dating materials were used for the dating validation,i.e.bulk samples and pollen concentrates,taken from surface sediments of the Daye Lake in Taibai Mountain of the Qinling Mountain ranges.The case study shows that pollen concentrates from enclosed lakes in mountains can provide the reliable age estimates,and avoid the impact of reservoir carbon to a certain extent.However,further validations on dating precision of pollen concentrates are needed to be applied at multi-deposition levels with multi-dating materials(e.g.terrestrial plant remains,charcoals,organics)for the Daye Lake.Based on former studies and this work,we summarized the standard process for extracting pollen concentrates from lake sediments,peat deposits,loess-paleosol sequences and ice wedges.The preparation of pollen concentrates mainly comprise pretreatment(acid-base method)and purification treatment(chemical treatments,pollen selection under microscope and heavy liquid flotation).Exploring new methods for extracting pollen concentrates from sediments,improving and simplifying extraction process and increasing the extraction efficiency(obtaining sufficient and high-content terrestrial plant pollen in a short time)will greatly promote the application of pollen concentrates dating in Late Quaternary chronology.
作者
张姚
崔巧玉
周爱锋
ZHANG Yao;CUI Qiaoyu;ZHOU Aifeng(Key Laboratory of Land Surface Pattern and Simulation,Institute of Geographical Sciences and Natural Resources Research,Chinese Academy of Sciences,Beijing 100101;Key Laboratory of Western China's Environmental Systems,Ministry of Education,College of Earth and Environmental Sciences,Lanzhou University,Lanzhou 730000,Gansu)
出处
《第四纪研究》
CAS
CSCD
北大核心
2021年第1期136-145,共10页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:41771208和41790421)资助。
关键词
碳十四测年
孢粉浓缩物
提取方法
^(14)C dating
pollen concentrates
extraction methods
