Anisotropy of magnetic susceptibility of the Neogene Guonigou section in the Linxia Basin and its paleoenvironmental significance

doi:10.6038/cjg2018M0245

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	Anisotropy of magnetic susceptibility of the Neogene Guonigou section in the Linxia Basin and its paleoenvironmental significance
	Kong YanFen 1,2,3; Sun Lu 1,2,3; Shen ZhongShan 1,2,3; Ge JunYi 4; Deng ChengLong 1,2,3
	2018-11-01
发表期刊	CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION
ISSN	0001-5733
卷号	61 期号:11 页码:4518-4529
摘要	The Linxia Basin is located at the northeastern edge of the Tibetan Plateau. It is filled with late Paleogene to Quaternary fluvio-lacustrine and eolian deposits rich in mammalian fossils, which provide invaluable information about a series of major geologic and environmental events, such as Tibetan uplift, Asian aridification development and Asian monsoon evolution. In this study, we present the results of anisotropy of magnetic susceptibility (AMS) measurements of the Guonigou section in the eastern Linxia Basin, and try to probe into sedimentary processes of the Linxia Basin during early Miocene to early Pliocene. The Guonigou section with a thickness of 183. 8 m consists of, from oldest to youngest, the Shangzhuang Formation of lower Miocene, the Dongxiang and Hujialiang Formations of middle Miocene, the Liushu Formation of upper Miocene, and the Hewangjia Formation of lower Pliocene. Mineral magnetic analyses, including temperature-dependent magnetic susceptibilities (chi-T curves), thermal demagnetization of three axis isothermal remanent magnetization (IRM), hysteresis loops, IRM acquisition and demagnetization curves, and component analysis of coercivity distributions, suggest that a mixture of magnetic minerals, such as magnetite, maghemite, hematite and goethite, are present in the Guonigou sedimentary sequence. However, magnetite and hematite serve as the dominant carriers of remanence of the sediments. The component analysis of coercivity distributions reveals an up-section decreasing trend in the concentration of hematite. There are two main rivers in Linxia Basin, including the north-south directed Daxiahe River and the east-west directed Taohe River. AMS measurements have been conducted on samples from the Guonigou section to determine the paleocurrent directions and to reconstruct sedimentary processes in the Linxia Basin during early Miocene to early Pliocene. The early Miocene Shangzhuang Formation, which is composed of reddish-brown silty clays, was deposited in a stable lacustrine sedimentary environment with little subsequent disturbances. The paleocurrent direction was NNW during the early Miocene, consistent with the Daxiahe River flows. The early Middle Miocene Dongxiang Formation, which is composed of the alternations of low susceptibility sediments (coarse-grained silts, sands and/or marly silts and clays) and high susceptibility sediments (brownish-red silty clays and silts), was deposited in alternating wet and dry conditions. The paleocurrent direction was mainly NNW (Daxiahe River dominated) with a small W component (Taohe River dominated) during the early Middle Miocene. The lake was closed in late Middle Miocene, when the basin was filled with fluvial gravels comprising the Hujialiang Formation. During the late Miocene Daxiahe River and Taohe River together transported sediments to the Guonigou section, comprising the Liushu Formation. The mutual effect of these two nearly perpendicular rivers produced a weak magnetic fabric in the Liushu Formation of lacustrine origin. The dominant paleocurrent directions were N-S and E-W. The sedimentary facies and paleocurrent direction changed in early Pliocene possibly due to the Tibetan uplift. The lower part of the Hewangjia Formation is mainly composed of fluvial conglomerates; and the upper part, mainly of floodplain clays with a north paleocurrent direction, which is dominated by Daxiahe River.
关键词	Linxia Basin Guonigou section Neogene Anisotropy of magnetic susceptibility
DOI	10.6038/cjg2018M0245
关键词[WOS]	NE TIBETAN PLATEAU ; SEDIMENTS ; SEQUENCE ; UPLIFT ; CHINA ; MAGNETOSTRATIGRAPHY ; VARIABILITY ; EVOLUTION ; FABRICS ; ROCKS
收录类别	SCI
语种	英语
WOS研究方向	Geochemistry & Geophysics
WOS类目	Geochemistry & Geophysics
WOS记录号	WOS:000450699100017
出版者	SCIENCE PRESS
引用统计
文献类型	期刊论文
条目标识符	http://119.78.100.205/handle/311034/9078
专题	中国科学院古脊椎动物与古人类研究所
通讯作者	Deng ChengLong
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China 2.Chinese Acad Sci, Inst Earth Sci, Beijing 100029, Peoples R China 3.Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Beijing 100049, Peoples R China 4.Chinese Acad Sci, Inst Vertebrate Paleontol & Paleoanthropol, Key Lab Vertebrate Evolut & Human Origins, Beijing 100044, Peoples R China
推荐引用方式 GB/T 7714	Kong YanFen,Sun Lu,Shen ZhongShan,et al. Anisotropy of magnetic susceptibility of the Neogene Guonigou section in the Linxia Basin and its paleoenvironmental significance[J]. CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION,2018,61(11):4518-4529.
APA	Kong YanFen,Sun Lu,Shen ZhongShan,Ge JunYi,&Deng ChengLong.(2018).Anisotropy of magnetic susceptibility of the Neogene Guonigou section in the Linxia Basin and its paleoenvironmental significance.CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION,61(11),4518-4529.
MLA	Kong YanFen,et al."Anisotropy of magnetic susceptibility of the Neogene Guonigou section in the Linxia Basin and its paleoenvironmental significance".CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION 61.11(2018):4518-4529.

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