南沙群岛海区NS97-13柱样沉积物磁化率各向异性研究
The anisotropy of magnetic susceptibility of Core NS97-13 sediments from the Nansha Islands sea area in the southern South China Sea
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摘要: 通过南海南沙群岛海区NS97-13柱样磁化率各向异性系统测试、统计计算和测年等分析,给出了沉积物的磁化率椭球几何形态,重建了研究海区的古水流方向、沉积物的沉积形式。研究结果表明:(1)压扁型椭球(E>1)的择优方向位于磁性线理-磁性叶理直线的上方,夹角β的范围为0°<β≤33.14°,拉长型椭球(E<1)的择优方向位于磁性线理-磁性叶理直线的下方,夹角α的范围为33.14°<α<56.86°,指示磁性颗粒沉降时受动力作用的大小及其受力方向不同;(2)由磁化率各向异性参数(磁性线理-各向异性度,磁性叶理-各向异性度)确定的沉积物有改造沉积、再沉积和稳定沉积三种形式,前两种形式掺杂在稳定沉积层中的不同部位,构成部分混合沉积;(3)最大磁化率和中间磁化率的轴向分布表征研究海区距今近62 ka以来古水流方向主要为南北和北东-南西向,总磁化率记录了Heinrich层中的冷事件H1—H6。Abstract: The anisotropy of magnetic susceptibility (AMS) of Core NS97-13 sediments from the Nansha Islands sea area in the southern South China Sea was analyzed combining with 14C dating, which afforded the magnetic susceptibility ellipsoid of geometry shapes, and paleocurrent directions and depositional forms of sediments were rebuilded in the study area. Results show that (1) the predominant direction of staved ellipsoid (E>1)is always located above the L-F straight line, whose nip angle (β) is 0°<β≤33.14°, whilst the predominant direction of elongated ellipsoid (E<1) is located below the L-F straight line, whose nip angle (a) is 33.14° <α<56.86°. These denote that the direction of hydrodynamic action is different when the magnetic granules deposit in the process of sedimentation. (2) The AMS parameter, (L-P, F-P) are demonstrated that the core sediments experience of reworked, redeposited and undisturbed three forms,and the former two are adulterated in the undisturbed sediment layers, resulting in the intermingled layers. (3) The axial distributions of the maximum susceptibility and the middle susceptibility are mainly NS and NE-SW, explaining that the paleocurrent direction has been mostly NS and NE-SW since about 62ka BP. The total magnetic susceptibility recorded six cold events, namely, the Heinrich layers (H1-H6),showing that there are six cold events in the Nansha Islands sea area.
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贺绍英,孙世伟,杨辟元,等.岩石磁化率各向异性[M].北京:地震出版社,1986:1-95. KENT D V.LOWRIE W.On the magnetic susceptibility anisotropy of deep-sea sediment[J].Earth Planetary Science Letters,1975,28:1-12. 侯红明,王保贵,汤贤赞.南极普里兹湾NP93-2柱样磁组构特征及其古气候意义[J].地球物理学报,1996,39(6):747-752. FOLAMI S L.Magnetic fabric of some IPOD sediment cores from the southwestern sector of Africa[J].J Sedimentary Petrology,1988,58:512-518. REES A J,WOODALL W A.The magnetic fabric of some laboratory deposited sediments[J].Earth Planetary Science Letters,1975,28:121-130. CHEN M H,LI Q Y,ZHENG F,et al.Variations of the last glacial warm pool:sea surface temperature contrasts between the open western Pacific and South China Sea[J].Paleoceanography,2005,20:1-12. 刘保柱,李从先,业治铮,等.沉积磁组构在长江三角洲晚第四纪古土壤研究中的应用[J].海洋地质与第四纪地质,1994,14(2):55-62. LIU J,ZHU R X,LI T G.Sediment-magnetic signature of the mid-Holocene paleoenvironmental change in the central Okinawa Trough[J].Marine Geology,2007,239:19-31. ELLWOOD B.B,BAISAM W L,ROBERTS H H.Gulf of Mexico sediment sources and sediment transport trends from magnetic susceptibility measurements of surface samples[J].Marine Geology,2006,230:237-248. 汤贤赞,陈忠,颜文,等.西太平洋暖池温区中心沉积物磁化率记录的YD和Heinrich冷事件[J].科学通报,2003,48(5),491-495. 张卫国,俞立中,陆敏.长江口潮滩沉积物氧化铁与磁性特征的关系[J].地球物理学报,2003,46(1):79-85. LARRASOANA J C,ROBERTS P,ROHLING E J.Magnetic susceptibility of eastern Mediterranean marine sediments as a proxy for Saharan dust supply[J].Marine Geology,2008,254:224-229. FOLAMI S L.Magnetic fabric results from DSDP Holes 380A and 524 sediment cores; a case study for comparison between low and high field torque magnetometer measurements[J].Marine Geophys Res,1991,13:239-253. 朱日祥,KAZANSKY A.MATASOVA G.等.西伯利亚南部黄土沉积物的磁学性质[J].科学通报,2000,45(11):1200-1205. ELLWOOD B B.Bioturbation minimal effects on the magnetic fabric of some natural and experimental sediments[J].Earth Planetary Science Letters,1984,67:367-376. BRADAK B.Application of magnetic susceptibility(AMS) for the determination of paleo-wind directions and paleo-environment during the accumulation period of Bag Tephra,Hungary[J].Quaternary International,2009,198:77-84. 方文东,郭忠信,黄羽庭.南海南部环流的观测研究[J].科学通报,1997,42(21):2264-2271. 郭忠信,方文东,陈福培,等.南沙群岛海域的环流及主要海流——1993~1994年南沙综合科学考察的一个结果[G] ∥南海海洋科学集刊VB,13集.北京:科学出版社,2000:1-24. GROUSSET F E,CORTIJOJO E,HUON S,et al.Zooming in on Heinrich layers[J].Paleoceanography,2001,16(3),240-259. LLNSLEY B K.Oxygeri-isotope record of sea level and climate variations in the Sulu Sea over the past 150 000 years[J].Nature,1996,380,234-237. SCHULZ H,ROD U V,ERIENKEUSER H.Correlation between Arabian Sea and Greenland climate oscillations of the past 110 000years[J].Nature,1998,393:54-57.
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