干旱区生态环境知识资源中心(Arid): 罗布泊Ls2孔近7.1Ma以来沉积物的环境磁学研究

Arid

	罗布泊Ls2孔近7.1Ma以来沉积物的环境磁学研究
其他题名	THE ENVIRONMENTAL MAGNETISM STUDY OF CORE Ls2 IN LOP NUR,TARIM SINCE 7.1Ma
	常秋芳; 常宏
来源期刊	第四纪研究
ISSN	1001-7410
出版年	2013
卷号	33 期号:5 页码:876-888
中文摘要	塔里木盆地的高分辨率环境记录对于理解西部干旱乃至全球变化至关重要。湖泊沉积物的磁学参数能够记录沉积环境和古气候信息。罗布泊地区是受西风影响的典型区域。本文选取罗布泊Ls2孔7.1Ma以来长度达1050.6m的沉积物进行详细的岩石磁学与环境磁学研究。结果表明,磁铁矿和赤铁矿是沉积物中主要载磁矿物。钻孔底部和上部的沉积物磁铁矿含量相对较高,中部强磁性矿物浓度降低导致赤铁矿占主导。磁性矿物以PSD(pseudo-single-domain)颗粒为主,并含有极少量的SP(super-paramagnetic)颗粒。罗布泊Ls2孔的S_(-ratio)比值表明,7.1~5.6Ma气候为相对较干旱和相对较湿润交替出现,5.6~3.6Ma干旱化加剧,3.60~0.74Ma有所缓和,0.74~0Ma干旱化最为强烈,其中5.1Ma和3.6Ma是两个明显的转折点。多磁学参数表明,晚中、上新世以来罗布泊地区的磁性矿物含量的变化,可以反映罗布泊地区气候渐进式的干旱化过程。
英文摘要	Late Cenozoic fluvio-lacustrine sediments of the Tarim basin are good archives of the paleoclimatic changes in Asian interior.The analysis and interpretation of changes in mineral magnetic signatures from a long Ls2 core(1050.6m in long;39° 46’N,88°23’18.2"E) recovered from Lop Nur in the northeast Tarim basin in 2004 spanning a timescale of approximately the last 7.1Ma years is reported by Chang et al.~([19]).A suite of mass specific susceptibility and magnetic remanence measurements were made at regular intervals of 100cm on 1056 samples.Rock magnetic measurements revealed that magnetite and hematite are the dominant magnetic minerals.Magnetite of PSD-size was identified as the main magnetic carrier minerals by temperature-dependent measurements of saturation magnetization and determination of hysteresis parameters. Based on detailed rock magnetic measurements like magnetic susceptibility versus high/low temperature curves,thermal demagnetization curve,hysteresis loops and FORC diagrams,we have investigated the magnetic properties of Lop Nur Ls2 core sediments.The abrupt decrease at about 580℃ in X-T curves revealed that magnetite could be the dominant magnetic mineral in the sediment.What is more,some samples showing decrease after 685℃ revealed hematite signal.FORC diagram displayed a PSD characteristic.Hysteresis loop showed a subtle wasp waist characters which is due to admixture of different coercivity minerals.This could be magnetite and hematite. HIRM and S_(-ratio) records indicate four intervals of hematite variations.Hematite concentration in the Lop Nur fluvio-lacustrine sediments is closely linked to the oxidation of magnetite.From 7.1Ma to 5.6Ma,hematite concentration is relatively low,consistent with a high lake level with weak oxidation of magnetite under a relatively humid climate.Hematite concentration increases from 5.6Ma to 3.6Ma,showing enhanced oxidation of magnetite.This implies strengthened aridification and deceased lake level.From 3.60Ma to 0.74Ma,slight decrease in hematite concentration indicates that the regional aridification is not further intensified,although the global climate becomes more arid and cooler after 3.6Ma.After ca.0.74Ma,the hematite concentration increases significantly,which is consistent with enhanced aridification after this time.Such climatic changes are important archives in reconstructing paleoclimate of the Asian interior.
中文关键词	罗布泊 ; 沉积物 ; 晚中新世 ; 岩石磁学 ; 干旱化
英文关键词	Lop Nur sediment Late Miocene rock magnetism aridification
语种	中文
国家	中国
收录类别	CSCD
WOS类目	GEOSCIENCES MULTIDISCIPLINARY
WOS研究方向	Geology
CSCD记录号	CSCD:4944959
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/229429
作者单位	中国科学院地球环境研究所, 黄土与第四纪地质国家重点实验室, 西安, 陕西 710075, 中国
推荐引用方式 GB/T 7714	常秋芳,常宏. 罗布泊Ls2孔近7.1Ma以来沉积物的环境磁学研究[J],2013,33(5):876-888.
APA	常秋芳,&常宏.(2013).罗布泊Ls2孔近7.1Ma以来沉积物的环境磁学研究.第四纪研究,33(5),876-888.
MLA	常秋芳,et al."罗布泊Ls2孔近7.1Ma以来沉积物的环境磁学研究".第四纪研究 33.5(2013):876-888.