• 责任者：Chang Qiufang (State Key Laboratory of Loess and Quaternary Geology ; Institute of Earth Environment ; Chinese Academy of Sciences ; Xi’an 710075 ; China) ; Chang Hong
• 刊名：Quaternary Sciences
• 出版年：2013
• 卷期：33(5)
• 关键词：湖泊沉积物 ; lake sediments ; 环境磁学 ; environmental magnetism ; 罗布泊 ; Lop Nor
• 页码：p.876-888
• 图表：9 illus., 1 table, 73 refs.
• 分类号：1200
• issnNo：ISSN1001-7410
• isbnNo：CN11-2708/P

     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.