摘要
以东海岛屿嵊山岛约2.75m厚的风尘黄土剖面为研究对象,基于光释光测年建立的时间标尺,通过沉积粒度和环境磁学等分析,与黄土高原典型黄土以及东部下蜀黄土进行对比,探讨该地区晚更新世古气候特征.光释光测年结果显示,嵊山岛黄土沉积始于约51 ka,对应于末次冰期.黄土沉积粒度参数和磁学参数分析结果显示,与西北黄土相比,嵊山岛黄土的频率分布曲线呈“三峰分布”,磁化率值偏大,波动幅度也较大.进一步运用粒级-标准偏差法提取环境敏感粒级组分,即细颗粒组分（＜23μm）和粗颗粒组分（＞23 μm）,分别代表该地区两种主要的粉尘搬运与沉积风力系统,可用于指示黄土沉积的阶段性特征.黄土粗细粒级环境敏感组分及环境磁学的变化揭示约49～ 35 ka期间研究区逐渐干旱化的气候历史,记录了末次冰期以来该地区古气候环境的演变过程.
The loess-paleosol sequence in the Shengshan Island（SSI） in East China Sea is an important aeolian archive,which can provide the information on aeolian activity,palaeoclimatic change and sea level change in the eastern coast of China during the Latest Quaternary.The 275 loess samples were cellected from the about 2.75 m-thick and not a bottom Shengshan Island section （SSIS） （URS：30°44′N,122°49′E;elevation 150 m above sea level） with the vertical interval of 1 cm from the northeast slope of the Chenqian Hill which is the highest peak of the Shengshan Island in the northern part of Zhoushan Islands.The section was divided into three layers.The first layer is the modern tillage layer（0～30 cm）,the layer is black and gray,the loose structure,the developed plant roots and no bedding structure.The second is loess（30～ 265 cm）,the layer is claybank,the fine grain,porous,loose soil,with lots of white calcium nodules,block with a small amount of palm red iron manganese film and the less plant roots;the third layer is the weathered layer of granite bedrock（below 265 cm）,the layer was not integrated with the overlying loess and it was obvious that granite weathering particles are mixed.Here we discuss the history of paleoclimate since the last glacial recorded in a representative loess section in the SSI in East China Sea,based on optically stimulated luminescence （OSL）dating as well as the detailed sedimentological and environmental magnetic investigations.Our results show that：（1） The OSL dating ages of the samples at the depth of 0.1 m,1.0 m,1.5 m,and 2.5 m are 0.4±0.1 ka,35±3 ka,42±4 ka,and 51±4 ka,repectively,which constrain the time-span of the SSIS loess sedimentation from ca.0.4 ka to 51 ka.This chronology implies that the onset of the SSI loess sedimentation is approximately synchronous with the Last Glacial.（2）Analyses of sediment grain size and rock magnetic parameters indicate that,sediment grain-size composition controls magnetic properties of the SSI loess,indicative of the wind intensity model,distinct from the pedogenic model interpreting the variations in magnetic properties of the loess in the Chinese Loess Plateau.The further analysis by extrcting grain-size class vs.Standard deviation values method,environment-sensitive size fractions of this section indicates,the fine grain fraction （〈23 μm） and coarse grain fraction （〉23 μm）.The two main kinds of fractions respectively represented dust removal and sedimentation wind systems in the area.Finally,the variations in sediment grain size and magnetic properties throughout the SSI loess indicate that the study area was dominated by a climate of strenghtened wind associated with gradually intensified aridity during the Latest Pleistocene.
作者
任少芳
郑祥民
周立旻
吕红华
艾东升
玄晓娜
曹宏伟
吴超
赵庆
Ren Shaofang;Zheng Xiangmin;Zhou Limin;Lu Honghua;Ai Dongsheng;Xuan Xiaona;Cao Hongwei;Wu Chao;Zhao Qing(Key Laboratory of Geographic Information Science of Ministry of Education, School of Geographic Science, East China Normal University Shanghai 200241;Academic Affairs Office, East China Normal University, Shanghai 200241;University Office of ECNU,East China Normal University, Shanghai 200241)
出处
《第四纪研究》
CAS
CSCD
北大核心
2018年第3期646-658,共13页
Quaternary Sciences
基金
国家自然科学基金项目（批准号：41371032）和国家基础科学人才培养基金项目（批准号：J1310028）共同资助
关键词
光释光测年
嵊山岛
风尘黄土
环境敏感粒度组分
optically stimulated luminescence dating
Shengshan Island
aeolian loess
environmentallysensitive component
