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福州盆地钻孔沉积物磁学性质及其对全新世环境变迁的响应

发表时间:2018-06-29  浏览量:811  下载量:129
全部作者: 车柏林,马明明
作者单位: 福建师范大学地理科学学院,湿润亚热带山地生态国家重点实验室 培育基地
摘 要: 对福州盆地梁厝(LC)钻孔沉积物进行详细的环境磁学参数及烧失量(loss on ignition,LOI)的测量,结果表明,钻孔沉积物的主导磁性矿物为亚铁磁性矿物(磁铁矿或磁赤铁矿),同时也含有少量的硬磁性矿物(赤铁矿或菱铁矿),磁性的强弱主要受到多畴(multi-domain,MD)磁性矿物颗粒浓度的影响。根据LC钻孔磁化率曲线及烧失量曲线与其临近钻孔(FZ4)的孢粉资料,可将钻孔沉积相划分为三层:1)在海侵前(> 9 000 cal yr BP),磁化率值及磁性矿物浓度值最低,烧失量也处于最低值,此时发生氧化作用,磁性矿物低温氧化成磁赤铁矿并进一步氧化成赤铁矿,物源区陆源碎屑物质磁化率降低是由于降水少,径流量也较小,地表径流所携带的陆源碎屑物质也较少;2)在海侵期间(9 000~2 000 cal yr BP)磁化率值相对较高,总体上该段磁化率从底部到顶部处于一个不断降低的过程,也响应了全新世适宜期气候的波动变化,气候由温暖湿润逐步向温凉干燥过渡;3)海退后(~2 000 cal yr BP),磁化率迅速增高,此时人类活动增加,大量植被被人类破坏导致地表裸露,侵蚀增加,提供了大量的碎屑物质,导致磁性矿物浓度增加。研究表明,福州盆地钻孔沉积物的磁学性质变化能够很好地响应全新世福州盆地所经历的海侵海退旋回、环境变迁过程以及人类活动历史。
关 键 词: 地理学;福州盆地;全新世;环境磁学;钻孔沉积物;海侵海退
Title: Magnetic properties of borehole sediments in Fuzhou basin and their responses to Holocene environmental changes
Author: CHE Bolin, MA Mingming
Organization: State Key Laboratory of Subtropical Mountain Ecology (Funded by Ministry of Science and Technology and Fujian Province), College of Geographical Sciences, Fujian Normal University
Abstract: The detailed environmental magnetic parameters and the measurement of the loss on ignition (LOI) of the borehole sediments have been studied in Liangcuo (LC), Fuzhou basin. The results show that the dominant magnetic minerals in the borehole sediments are ferromagnetic minerals (magnetite or magnetic hematite), and a small amount of hard magnetic minerals (hematite or siderite). The strength of the magnetic minerals is mainly influenced by the particles concentration of the multi-domain (MD) magnetic mineral. According to magnetic susceptibility curve and LOI curve of LC borehole and its adjacent drill (FZ4) sporopollen data, the drilled sedimentary facies can be divided into three layers. 1) Before transgression (>9 000 cal yr BP), the magnetic susceptibility and the magnetic mineral concentration are the lowest, and the LOI is also at the lowest value. The oxidation action of magnetic minerals occurs at this time. It is oxidized to magnetic hematite under low temperature and further oxidized to hematite. The decrease of magnetic susceptibility in the source area is due to the less precipitation, smaller runoff and less terrestrial debris carried by surface runoff. 2) During the period of transgression (9 000-2 000 cal yr BP), the magnetic susceptibility value is relatively high, and in general, the magnetic susceptibility of this section is continuously reducing from bottom to top, which also responds to the fluctuation of the climate in the Holocene suitable period, and the climate gradual transition from warm and moist to cool and dry. 3) After the sea retreat (2 000 cal yr BP), the magnetic susceptibility is rapidly increasing as human activity increases, and a large number of vegetation is exposed by human destruction. The increase in corrosion provides a large amount of detrital matter, resulting in the increasing concentration of magnetic minerals. The study shows that the magnetic properties of the borehole sediments in the Fuzhou basin have a well response to the transgressive regression cycle, environmental changes and the history of human activities in the Holocene Fuzhou basin.
Key words: geography; Fuzhou basin; Holocene; environmental magnetism; borehole sediments; transgressive regression
发表期数: 2018年6月第12期
引用格式: 车柏林,马明明. 福州盆地钻孔沉积物磁学性质及其对全新世环境变迁的响应[J]. 中国科技论文在线精品论文,2018,11(12):1255-1270.
 
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