末次间冰期-冰期旋回黄土环境敏感粒度组分的提取及意义

采用粒级-标准偏差方法对黄土高原西部、河西走廊及河南西部等6个剖面末次间冰期-冰期旋回的黄土-古土壤粒度进行了系统分析，提取了对环境变化敏感的粒度组分。各剖面的环境敏感粒度组分主要分为粗细两个组分，并显示出一定的区域性差异和不同的沉积学意义。敏感组分主要受物源和沉积后成壤作用的影响：冰沟和罗家湾剖面可能受源区的影响更大而使敏感组分偏粗，暖和湾和扣马剖面可能由于后期风化的影响较大而使敏感组分偏细。对扣马剖面末次冰期旋回堆积的L1和S1的粒级一标准偏差分析表明，L1的敏感组分与全剖面相似；而S1的敏感组分与全剖面存在较大差异，可能与成壤作用有关。

ANALYSIS OF GRAIN-SIZE POPULATIONS WITH ENVIRONMENTALLY SENSITIVE COMPONENTS OF LOESS DURING THE LAST INTERGLACIAL-GLACIAL CYCLE AND THEIR IMPLICATIONS

Partitioning of subpopulations in bulk grain-size distribution and identification of their sedimentary implications has become a fundamental task for further studies on quantitative reconstruction of the sedimentary environment.The subpopulations were identified through calculating standard deviation of each grain-size class of the six profiles of the loess-paleosal formed during the last interglacial-glacial cycle in the west of the Loess Plateau,Hexi Corridor and the west of Henan Province,China.The peak values of standard deviation corresponded to the modal grain-sizes of each environmentally sensitive grain-size population.Findings of the study indicate that the two major grain-size populations(coarse and fine) varied from profile to profile,suggesting different sedimental implications.Distance of material resources and post-sedimental pedogenesis are the two major affecting factors on environmentally sensitive grain-size populations.The sensitive grain-size populations of Binggou and Luojiawan profiles were coarser because they were more influenced by the distance of material resources;whereas the sensitive grain-size populations of Nuanhuowan and Kouma profile were finer as they were more influenced by the pedogenesis.The results showed similar populations and subpopulations.The analysis of the standard deviation of each grain-size class of Koma profile demonstrated comparability between the population and L_1,which deposited during the last glacial period,and that big difference between the population and S_1,which deposited during the last interglacial period,suggesting close relationship with pedogenesis.