杨立辉
, 叶玮, 郑祥民
YANG Li-hui, YE Wei, ZHENG Xiang-min
中图分类号: P318
文献标识码: A
文章编号: 1000-0690（2015）11-1475-07
通讯作者:
收稿日期: 2014-08-10
修回日期: 2014-11-9
网络出版日期: 2015-11-20
版权声明: 2015 《地理科学》编辑部 本文是开放获取期刊文献，在以下情况下可以自由使用：学术研究、学术交流、科研教学等，但不允许用于商业目的.
基金资助:
作者简介:
作者简介：杨立辉（1980-）,男,安徽寿县人,博士研究生,实验师,主要从事长江中下游第四纪环境变化研究。E-mail:lihuipost@gmail.com
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摘要
对浙江新昌玄武岩、花岗岩风化壳红土和江西南昌第四纪沉积型红土剖面的磁学特征进行了分析,结果表明,同一气候区内风化壳红土的磁学特征受母质特征影响较大。随着风化强度的增加,强磁性的玄武岩风化壳磁化率先减小后增加,磁性矿物颗粒先变粗后变细,弱磁性的花岗岩风化壳磁化率逐渐增加,磁性矿物颗粒逐渐变细。第四纪沉积型红土剖面中,均质红土磁化率远大于网纹红土,磁性矿物颗粒亦较网纹红土层细。这些差别说明了第四纪沉积型红土剖面中均质红土与网纹红土不完全相同的物质来源。
关键词：
Abstract
Kind of red, loose or semi-cemented sediment was widely distributed in tropical and subtropical regions of China, called Quaternary Red Clay (QRC). The causes and definitions of QRC were argued intensely. Depends on matrix, the QRC can be broadly divided into two types, Sedimentary Red Clay (SRC) and Laterite Weathering Crust (LWC). The SRC, development on all kinds of Quaternary sediments, always got similar profile configuration. The layer of SRC profile, from top to bottom, was Homogeneous Red Clay (HRC) or Yellow-Brown Earth (YBE), Vermicular Red Clay (VRC) and weathered gravel or bedrock; LWC was a kind of residual soil, formed by different types of bedrock weathering and widely distributed in tropical and subtropical regions. Representative LWC profile was generally contained weathered red soil, semi-weathered layer and bedrock. In this article, magnetic characteristics of basalt and granite weathering crust in Xinchang, Zhejiang Province, Quaternary SRC in Nanchang, Jiangxi Province were analyzed. The main characteristics of LWC are that, magnetic characteristics distinction of two kinds of weathering crust in the same climate zone was relatively large and the magnetic characteristics were determined by the matrix; Magnetisability of basalt weathering crust increased after a small decrease with the increasing weathering intensity; Magnetisability of granite weathering crust increased with increasing weathering intensity. Intense weathering made mineral particles tapering and antiferromagnetic minerals reduce in these two kinds of weathering crust. The main characteristics of sedimentary red clay were that, magnetisability of HRC was greater than VRC at least one order of magnitude. The content of antiferromagnetic mineral in VRC was much greater than the HRC. The content of Pseudo-Single Domain and Multidomain grain in VRC was much greater than the HRC. The magnetic characteristics change rule in SRC did not meet with the weathering rule prove that maybe HRC and VRC got different provenance in Quaternary sedimentary red clay profile.
Keywords：
环境磁学已被广泛应用于提取风成[1~11]及水成[12~15]沉积物上的环境变化信息。黄土高原黄土-古土壤序列的磁化率与古气候变化显著相关,其变化特征与深海氧同位素也有很好的对应关系,因此可以利用黄土的磁化率来了解第四纪气候变化过程[8,16,17]。目前,中国北方黄土磁化率已被视为东亚夏季风强度的替代指标[16,18,19],广泛用于海陆对比,定量古气候（古降水）重建,以及古降雨量的分布再现[20]。虽然在中国黄土-古土壤磁化率形成的机理上存在许多争议[21,22],但被广泛接受的观点认为土壤发育过程中产生了大量的超顺磁颗粒,从而造成古土壤磁化率较黄土高。
中国南方地区广泛分布的第四纪红土,是中国南方古环境演化和气候变迁的重要信息载体[23~25]。近年来,许多学者也试图在中国南方找到能表征热带-亚热带地区古环境变迁的磁学参数[26,27],从而对南方第四纪红土记录的环境变化信息进行探讨。目前,对中国南方红土磁化率与气候关系的认识仍存在许多争议。一些学者在研究安徽宣城红土时[26]认为：宣城红土磁化率曲线与黄土磁化率曲线和深海氧同位素曲线具有很好的可比性[9]。另外一些学者[28~32]对安徽、浙江、湖南、江西和广西等地红土剖面进行磁测发现,上覆黄棕色土与风化红土χ值接近,而风化程度相对较强的网纹红土层的χ、SIRM（饱和等温剩余磁化强度,文中量符号为SSIRM）及ARM（非磁滞剩磁,文中量符号为AARM）比风化红土层约低一个数量级,这与风化强度指标呈极显著负相关,这点与“黄土-古土壤”序列中χ随风化成土作用增强而增加的规律有根本区别[33]。这被解释为由于高温多雨,红土母质中所含的强磁性矿物转化为弱磁性矿物[34]。然而,对于高温多雨的环境是否能够使第四纪红土中强磁性矿物转化为弱磁性矿物以及如何转化,尚未有深入研究。
风化壳红土属残积红土。中国南方广泛分布的红色风化壳系漫长的第四纪以来的脱硅富铁铝风化产物,它们形成于高温高湿条件下。年均温16~25℃,年降雨量在1 500 mm以上,其风化体呈均质红色[35]。残积型风化剖面从地表向下到母岩,风化程度逐渐变弱[36]。因此,将相同气候区内完整风化壳红土剖面与第四纪红土剖面的磁学特征进行系统对比,可以深入认识磁学特征与成壤作用强度变化的关系,探讨第四纪红土磁性特征的形成机理及环境意义。
坑西和儒岙剖面均位于浙江省新昌县,属亚热带气候,地处中、北亚热带过渡区,常年日照约1 900 h,年平均气温16.6℃,年降水量1 500 mm,无霜期240 d。坑西剖面地理坐标为29°28′29.04″N、120°59′46.86″E,为玄武岩风化壳。剖面厚度为650 cm。0~70 cm,为现代土壤层;70~500 cm为风化红土层;500~650 cm为半风化玄武岩。以20 cm为间隔;儒岙剖面地理坐标为29°20′41.22″N、120°57′25.80″E,厚400 cm,为花岗岩风化壳。0~220 cm为风化红土层,220~400 cm为半风化花岗岩层。20 cm等间隔采样。南昌剖面地理坐标为28°38′7.44″N,115°48′49.32″E,属于亚热带湿润季风气候,年平均气温17℃,年降雨量约1 600 mm,年日照时间约1 800 h,年无霜期约260 d。剖面高约300 cm。0~150 cm为均质红土层,150~300 cm为网纹红土层。10 cm等间隔采样。
高频磁化率（4.7 kHz）和低频磁化率（0.47 kHz）采用英国Bartington MS2磁化率仪测定,非磁滞剩磁（ARM）采用D2000交变退磁仪和Mnispin旋转磁力仪测定,1 T,-20 mT,-100 mT和-300 mT磁场下的等温剩磁（IRM,文中量符号为IIRM）采用Molspin脉冲磁化仪测定。实验在华东师范大学河口海岸学国家重点实验室完成。
坑西剖面30个样品的磁学特征见图1。磁化率χ变化于（187.36~726.81）×10-8m3/kg之间,平均值为345.52×10-8m3/kg,表明剖面土体中含有较多的磁性矿物。半风化基岩磁化率最高,达到726.81×10-8m3/kg,随着风化强度的增加,磁化率迅速降低。在风化红土层中部达到最小值187.361×10-8m3/kg后又缓慢上升。
Thompson等认为[37],SIRM与χ的相关关系可以指示样品中各类磁性矿物比例关系。当SIRM与χ为高度相关时,指示样品中只有某一种磁性矿物或某种磁性矿物含量占绝对优势,而不论样品中磁性矿物粒径大小;否则,则指示样品中多种类型的磁性矿物并存;SIRM/χ则可以估算样品中磁性矿物晶粒的大小。剖面中SIRM与χ的相关系数半风化基岩层中为0.7,风化红土中为0.82,均为高度相关。表明坑西玄武岩风化壳中有一种磁性矿物类型占优势,且随着风化强度增加,在风化红土层中该矿物类型的优势度进一步增强了。为了进一步明确磁性矿物的类型,文章计算了S-Ratio（文中量符号为SS-Ratio）（-IIRM-300 mT/SSIRM）值硬剩磁,该值主要反映样品中反铁磁性矿物与亚铁磁性矿物的比例[38],当S-Ratio接近1时,表明样品亚磁铁矿含量占绝对优势;若S-Ratio值<0.8,样品含有一定量的反铁磁性矿物[39]。坑西剖面的S-Ratio均值为0.98。全剖面S-Ratio接近1的事实表明,坑西剖面磁性矿物类型以亚铁磁性矿物占主导,且主要为磁铁矿。前人的研究也证明[40],浙江玄武岩发育土壤的χ主要由原生和次生的磁铁矿和磁赤铁矿所贡献。S-300 mT可以作为不完整反铁磁性矿物和亚铁磁性矿物相对含量的指标[41]。高值表明样品中亚铁磁性矿物居多,坑西剖面的S-300 mT均达到了95%以上,也同样证明了剖面中以亚铁磁性矿物为主。
图1 新昌坑西剖面磁性垂向变化
Fig.1 Vertical magnetic parameter variations of Kengxi profile in Zhejiang Province
HHIRM=[(IIRM300+SSIRM)/2]值反映的是不完整反铁磁性物的含量（文中HIRM的量符号为HHIRM）。总体上来看,硬剩磁含量随着风化强度的增加（深度的减小）表现出现增加后减小的趋势,转折点在风化红土层与半风化基岩的交界处。说明了在玄武岩石风化的前期的破碎与半风化阶段,反铁磁性矿物含量随着风化的增加而增加,但是当风化强度达到一定程度,破碎的岩石逐渐转变为风化红土后,其不完整反铁磁性矿物的含量随着风化的加强而减小。
超顺磁（SP）颗粒（粒径<0.03 mm）含量通常可以用频率磁化率（χfd含量）来表征[2,42]。一般认为,若χfd含量大于5%~6%,则样品中存在SP颗粒。从图1中可以看出,剖面中χfd含量几乎全小于5%。说明尽管玄武岩发生了风化,但基本没有新的SP颗粒生成,高磁化率是由岩石本身所含的铁矿物决定的。从反映稳定单畴（SSD）颗粒的χARM值看,与磁化率χ的相关系数为0.95,高度正相关揭示磁性颗粒以SSD为主。χARM/SSIRM是一个对亚铁磁性矿物颗粒大小极为敏感的参数[43]。通常情况下,若χARM/SIRM值较低,则反映样品中存在大颗粒的假单畴与多畴。坑西剖面由下至上表现为先减小后增大,转折点在风化红土与半风化层的界面处,说明磁性矿物的粒径随着风化强度的增加先变粗后又变细。
儒岙花岗岩风化壳20个样品的磁学特征见图2。磁化率χ变化于（4.18~23.21）×10-8m3/kg,全剖面平均值仅为10.93×10-8m3/kg,表明剖面样品中含有的磁性矿物相对玄武岩较少。从χ随深度变化中（图2）可以看出,χ数值在240~400 cm段较低且变化小,但在240 cm以上陡然增加且波动较大,说明花岗岩风华壳磁化率随着风化程度的增加而增大。
儒岙剖面SIRM变化于（144.01~4 254.93）×10-5（A·m2）/kg之间,均值为942.36×10-5（A·m2）/kg进一步说明了整个剖面的磁性矿物,特别是亚铁磁性矿物的含量不高。SIRM与χ的相关系数半风化基岩层中为0.2,低度相关,风化红土中为0.67,中度相关。表明花岗岩风化壳中磁性矿物含量低但类型较多。风化红土层中S-Ratio除最顶部一个样外,其他均大于0.8。而半风化层的底部则小于0.8,表明风化红土层中以亚铁磁性矿物为主,而半风化层中存在一定比例的不完整反铁磁性矿物。前人对中国亚热带花岗岩风化壳的磁学特征研究也表明[43,44],亚热带花岗岩风化壳红土的主要强磁性矿物为磁铁矿和磁赤铁矿,含有少量赤铁矿和针铁矿;S-300 mT与硬剩磁HIRM表现为除了最顶部一个样品含量异常外,其他样品总体表现为随着深度的增加而减小,但剖面内的变化趋势不明显。考虑到顶部人为干扰的可能,整个剖面的不完整反铁磁性矿物含量都相对较低,风化红土层与半风化层未表现出明显差别。
图2 儒岙剖面磁学特征垂向变化
Fig.2 Vertical variations of magnetic parameters at Ruao profile in Zhejiang Province
从频率磁化率变化曲线看出,儒岙剖面底部的花岗岩半风化层波动较大,但多数小于5%,因此判断半风化层可能含有少量超顺磁颗粒,而风化红土层则全部大于6%,表明风化红土层含有较多的SP颗粒。χARM与χ的相关系数在风化红土层与半风化层分别为0.83和0.79,都是高度相关性,可见稳定单畴亚铁磁性矿物对风化红土层χ有较大贡献。亚铁磁性矿物粒径敏感的敏感参数χARM/SSIRM在剖面中依然波动比较大,但总体表现为风化红土层大于半风化层,表明了半风化层较风化红土层中存在较粗的磁性颗粒。前人的研究也表明[44],花岗岩母质中的亚铁磁性矿物的磁畴以多畴占主导地位,随着风化强度的增强,逐渐形成较细粒的超顺磁与单畴磁性矿物。
南昌剖面磁学特征见图3,χ变化于（16.97~260.40）×10-8m3/kg之间,平均值103.25×10-8m3/kg,表明剖面磁性矿物含量较多。剖面SIRM值变化于（1 548.81~8 306.4）×10-5（A·m2）/kg之间,均值为3 907.43×10-5（A·m2）/kg。SIRM与χ的相关系数均质红土层为0.99,网纹红土层为0.34,据此推测南昌第四纪红土剖面均质红土中某种磁性矿物含量占绝对优势,而网纹红土层磁性矿物类型较为复杂。均质红土层S-Ratio均大于0.8,平均值为0.92。而网纹红土层大多小于0.8,特别是网纹红土下段最低仅为0.04,因此可以判断均质红土层中以亚铁磁性矿物为主,而磁滞回线和热磁曲线的特征则指示亚铁磁性矿物主要为磁铁矿[45]。而网纹红土中随着深度的加深反铁磁性矿物含量大幅上升,并导致SIRM值相应增加[32]。S-300 mT由顶部至底部逐渐减小以及HIRM含量在网纹红土层迅速增加的变化趋势也应证了反铁磁性矿物含量网纹红土层大于均质红土层。
图3 南昌剖面磁学特征垂向变化
Fig.3 Vertical variations of magnetic parameters at Nanchang profile in Jiangxi Province
南昌剖面χfd全部大于6%,顶部均质红土层甚至达到12%~15%区间。表明均质红土层含有较多的SP颗粒,而网纹红土层虽然含有SP颗粒,但含量已较均质红土层大为减少。χARM与χ的相关系数在风化红土层与半风化层分别为1.0和0.88,都是高度相关性,可见稳定单畴亚铁磁性矿物对均质红土层χ有较大贡献。整个剖面的χARM垂向逐渐减小,虽然有局部的起伏波动,但总体趋势不变。这说明均质红土层的稳定单畴亚铁磁性矿物含量比较网纹红土层高。剖面的χARM/SSIRM值也表现为网纹红土层远远小于均质红土层的趋势,因此推测,网纹红土层磁性矿物的粒度大于均质红土层,这与前人的研究也是吻合的[32]。热磁曲线研究表明,长江中下游红土剖面中黄棕色土层与均质土层中以亚铁磁性矿物磁铁矿、磁赤铁矿为主,网纹红土则以不完整反铁磁性矿物赤铁矿为主[32] 。
分析浙江新昌玄武岩和花岗岩风化壳的磁学可以看出该地区风化壳红土的共同特点。第一,即使在相同的气候区,风化壳的磁学特征依然受母质影响较大。如花岗岩风化壳与玄武岩风化壳,母质本身所含磁性矿物特征直接决定风化壳的磁学特征;第二,弱磁性的花岗岩母质经过强烈的风化作用可以导致风化壳磁化率不断增强。而强磁性的玄武岩母质,其磁化率表现为随着风化强度的增加先减小后增加的趋势。这是由于玄武岩本身具有强磁性,在风化过程中一部分磁铁矿转变为弱磁性的针铁矿和褐铁矿等[46],使得风化壳磁化率减弱,但是随着成土过程中氧化还原反应和有机质作用的加强使得土壤中磁赤铁矿、磁铁矿和赤铁矿含量呈现增加趋势,风化壳的磁化率则又表现出增加的趋势[46,13],这在中国南方现代红壤有大量实证[47];第三,强烈的风化作用也使得磁性矿物颗粒逐渐变细。虽然玄武岩风化壳的磁学特征显示,在风化初期磁性矿物颗粒有增加的趋势,但随着风化的持续,磁性矿物颗粒也逐渐变细了。
对于沉积型红土,其磁学特征表现出与风化壳型红土完全不同的特征。首先,南昌剖面均质红土的磁化率大于网纹红土层至少一个数量级;其次,网纹红土层反铁磁性矿物含量远远大于均质红土层;第三,网纹红土层大磁畴含量远远大于均质红土层。而前人的研究结果却表明,长江中下游地区的第四纪沉积型红土,其网纹红土层风化强度大于上覆均质红土层及黄棕色土层[33]。
关于网纹红土低的磁化率有着多种解释,一些学者认为是风化过程中各种原因引起的铁流失造成网纹红土磁化率低,风化强度并不是控制红土磁化率的唯一因素[33]。而赵其国等[48]在研究安徽宣城均质红土与网纹红土中的全铁含量时发现,均质红土与网纹红土中铁含量差别不大,因此网纹红土中低的磁化率值与铁迁移可能性不大。因此,赵其国等认为网纹红土磁化率低是在湿热条件下强磁性的亚铁磁性矿物被还原成弱磁性的不完整反铁磁性矿物所致。事实上,与沉积型红土在同一个气候区内的坑西玄武岩和儒岙花岗岩两种母质的风化壳型红土均未发现强风化层中反铁磁性矿物含量增加的现象。即使在风化强度更剧烈的海南岛,其玄武岩风化壳的低频磁化率在风化红土层中亦随风化强度的增强而逐渐增强[49]。前人研究也指出,母质自身的矿物和磁性特征是造成土壤磁性特称差别的一个非常重要的原因[24,33,50]。母质不同,即使发育于相同气候区的风化壳,磁性特征可以表现出截然不同的特点。因此推断长江中下游地区的第四纪沉积型红土其网纹红土层与其上的均质红土层和黄棕色土层具有不完全相同的物质来源,其物源磁性特征的本底值差异是造成均质红土层与网纹红土层磁性特征差异的根本原因。
对比相同气候区内不同母质红土的磁学特征发现,不同母质的风化壳红土磁学特征差异比较大,同时也存在一些规律。母质矿物及磁学特征对发育于其上的风化壳有着强烈的影响。
1） 弱磁性的花岗岩母质,其风化壳磁化率总体亦较低,且随着风化作用的加强,磁化率增加了;风化红土层的磁性矿物以亚铁磁性的磁铁矿为主,反铁磁性矿物含量总体较少,且随风化强度变化的趋势不是很明显;半风化层中的亚铁磁性矿物的磁畴以多畴占主导地位,随着风化强度的增强,逐渐形成较细粒的超顺磁与单畴磁性矿物。
2） 强磁性特征的玄武岩母质,其风化壳磁化率亦较高,且磁化率表现为随着风化强度的增加先减小后增加的变化趋势,拐点在风化层与半风化层交界处;硬剩磁含量随着风化强度的增加表现出现增加后减小的趋势;χ的主要载体为稳定单畴的磁铁矿,磁性矿物的粒径随着风化强度的增加先变粗后又变细,转折点在红土层与半风化层。
3） 第四纪沉积型红土与风化壳型红土具有完全不同的磁学特征。第四纪红土剖面均质红土层的磁化率大于强风化的网纹红土层至少1个数量级;网纹红土层反铁磁性矿物含量远远大于均质红土层;网纹红土层的大磁畴含量远远大于均质红土层。
风化壳红土与第四纪沉积型红土完全不同的磁学特征可能指示了第四纪沉积型红土剖面中均质红土（或者黄棕色土）与下伏网纹红土具有不完全相同的物质来源。
The authors have declared that no competing interests exist.
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ABSTRACT
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根据实测数据，对磁化率与粒 度、矿物之间的关系进行了探讨。结果表明，沉积物粒度与磁化率的关系，与物源及沉积动力密切相关。因此，在一定条件下，可利用两者关系来反映物源或沉积动 力。碎屑沉积物的磁化率主要取决于磁铁矿的含量，并由此建立了磁化率（Ｓ，１０（－７）ｍ３ｋｇ（－１））与磁铁矿的百分含量（Ｐｍ）之间的回归方程 Ｓ＝４９．１８Ｐｍ＋４９．５。由于磁铁矿为重矿物，在沉积物中常常与钛铁矿、磷钇矿、独居石、锆石、金红石、锐钛矿、板钛矿等其它重矿物伴生，故在一定 条件下可利用磁化率来定量估算沉积型砂矿的品位。
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通过固城湖沉积物中高分辨率的岩石磁学取样及其实验研究，取得了环境磁学参娄航各种磁参数的 比值随深度的变化曲线，结合其他气候指标和同位素年龄结果，表明湖泊沉积中磁参数及其比值的变化能与末次晚冰期以来的古气候变化很好的相对应，尤其是在 ４．００ｍ和１２．０３ｍ的气候转折点上，沉积物中环境磁参数及其比值同样出现明显的变化，有力地说明沉积物中磁参数及其比值能很好地记录湖泊沉积物沉积 时的古气候变化，并且可用于认
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****
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The rock magnetic properties of the Chinese loess and paleosols constitute a unique and sensitive record of East Asian paleoclimate through the Quaternary Period. Systematic variations in the concentration and grain size of the magnetic minerals in these sediments have produced systematic variations in the magnetic susceptibility signal, which can be easily and rapidly measured at many sites across the Loess Plateau. Variations in many other rock magnetic properties can be used to identify the key shifts in ferrimagnetic grain size, but magnetic susceptibility alone is sufficiently sensitive to record stadial and interstadial climate stages, as well as glaciations and interglaciations. Past changes in rainfall and monsoon activity for this region are reconstructed from the susceptibility variations. The susceptibility record is calibrated using the modern relationship between rainfall and pedogenic susceptibility on the Loess Plateau. Our rainfall reconstructions identify enhanced summer monsoonal activity in the Chinese Loess Plateau region in the early Holocene and the last interglaciation. In the presently semiarid western area of the plateau, annual precipitation in interglacial times was up to 80% higher than at present; in the more humid southern and eastern areas, values were up to 20% higher than today's levels. During the last glaciation, precipitation decreased across the entire plateau, typically by 鈭25%. The relationship between pedogenic susceptibility, climate, and weathering age was examined over the Northern Hemisphere temperate zone and the observed positive correlation between rainfall and susceptibility indicates that climate, rather than soil age, is the predominant factor that controls pedogenic susceptibility enhancement in loess soils.
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[1] We examine spatial variations in magnetic susceptibility (MS) over the Loess Plateau in China based on 50 sections in order to identify spatial changes in monsoon climate at key glacial, interglacial, and interstadial intervals for the last 600 kyr. The results indicate strong coherence between MS variations during the interglacial periods and present-day precipitation and temperature patterns. This suggests that the strength of the summer monsoon had a dominant influence on the MS signals in soils, through modulating pedogenic intensity. The distribution of MS during glacial periods is characterized by weak S-N gradients and rough W-E zonal patterns, indicating a negligible effect of the summer monsoon. Interstadial patterns are intermediate between the glacial and interglacial ones. Interglacial patterns for the last 600 kyr are essentially similar, suggesting that the climate regime during these periods has not undergone significant changes and that the east Asian summer monsoon has remained the main moisture carrier. Our estimates of the relative amplitudes of climate oscillations during these time slices are consistent with earlier paleoclimate studies. These data, associated with the available susceptibility-based climofunctions, may be used to estimate spatial changes of paleorainfall and paleotemperature for these key periods and hence to test climate models.
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The low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate. The accumulation rate of the magnetite was fairly constant throughout the last 1.2 million years and can serve as a measure of time. Susceptibility records from localities near Xifeng and Luochuan, located 160 km apart are compared and used to define informal lithostratigraphic units in the Loess Plateau of China.
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网纹红土的成因及其环境意义 [J]. |
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中亚热带网纹红土的稀土元素特征与成因分析 [J].https://doi.org/10.3969/j.issn.1000-0690.2008.01.008 URL Magsci [本文引用: 1] 摘要
130块样品的稀土元素含量、稀土分布模式、稀土特征值分析以及 物源指数的计算表明,中亚热带网纹红土与北方黄土具有相似的稀土特征.网纹红土稀土元素平均含量(179.57μg/g)与地壳平均值(178μg /g)、北京郊区1998年12月大气粉尘稀土总量(177.97μg/g)以及两块中国黄土标样平均值(178.22μg/g)非常接近,稀土分布模式 与风成沉积及UCC类同,轻稀土强烈富集,重稀土淋失,轻重稀土比值9.86～15.18,Ce元素正异常,物源指数<0.5.稀土元素特征指示, 所研究的网纹红土的母质与黄土具有风尘相似性,而且风尘沉积后经历了较北方黄土更为强列的风化作用,其形成环境与古土壤和上新世红粘土接近.
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红土系列剖面的磁化率特征与古环境气候冷暖变换 [J].
中国科学院机构知识库(中国科学院机构知识库网格（CAS IR GRID）)以发展机构知识能力和知识管理能力为目标，快速实现对本机构知识资产的收集、长期保存、合理传播利用，积极建设对知识内容进行捕获、转化、传播、利用和审计的能力，逐步建设包括知识内容分析、关系分析和能力审计在内的知识服务能力，开展综合知识管理。
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Hao Q Z et al.Loess-soil sequences in southern Anhui Province:Magnetostratigraphy and paleoclimatic significance [J].https://doi.org/10.1360/03wd0183 URL Magsci [本文引用: 1] 摘要
姝Two parallel loess-soil sequences from Xuancheng and Fanchang in southern Anhui Province are dated using geomagnetic and luminescence methods.The Brunhes/Matuyama(B/M) reversal boundary is recognized within the lower part of the so-called Vermiculated Red Soil (VRS) in the Xuancheng section while the entire Fanchang sequence is of Brunhes age.This indicates that the most recent VRS in southern China,a stratigraphic marker and an indication of extremely warm-humid conditions,was formed during the middle Pleistocene,chronologically correlative with the S4 and S5 soil units in northern China.Microscopic and sedimentologic investigations reveal that eolian deposition started in this region at about 0.85 MaBP,roughly synchronous with the well-known Mid-Pleistocene climate change of global significance.The strengthening of both summer and winter monsoon circulations and the consequent river hydrological changes at that time would have provided favorable conditions for sustained eolian deposition in the middle-lower reaches of the Yangtze River since 0.85 MaBP.
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第四纪红土的磁性与氧化铁矿物学特征及其古环境意义 [J].https://doi.org/10.3321/j.issn:0564-3929.2000.02.005 URL [本文引用: 1] 摘要
应用矿物磁测、X-衍射和电镜 技术对浙江省第四纪红土的磁性与氧化铁矿物学特征进行了研究。结果表明，均质层和网纹层的磁化率（x）、频率磁化率（xfd）、软剩磁 （SoftIRM）、非滞后剩磁（ARM）、他和等温剩磁（SIRM）和剩磁矫顽力（（BO）CK）等磁性参数存在明显差异，均质层的磁化率和饱和等温剩 磁分别是网纹层的6倍和4倍；第四纪红土的磁化率主要由风化成土作用产生的超顺磁性颗粒（SP）和稳定单畴颗粒（SSD）贡献，它们的磁化率值与频率磁化 率和非滞后剩磁是显著正相关；均质层中DCB处理后的磁化率和xfd损失量明显高于网纹层，其DCB处理损失的磁性主要是次生的SP和SSD颗粒，DCB 处理后损失的磁化率与频率磁化率呈指数正相关；根据均质层的IRM获得曲线、剩磁矫顽力、X－衍射和透射电镜观察证明红土中的氧化铁矿物组成主要是圆片状 的赤铁矿、鱼鳞状的磁赤铁矿和针状的针铁矿。对红土磁性成因的物理机制进行了讨论，初步认为第四纪红土中磁性矿物的数量、粒度、类型等特征的变异指示了红 土化作用的变异，可作为研究第四纪环境变化的手段之一。
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中国东部红土的磁性及其环境意义 [J].https://doi.org/10.3321/j.issn:0001-5733.1999.06.006 URL Magsci 摘要
通过中国东部红土剖面的环境磁学参数（磁化率、频率磁化率、非磁滞磁、饱和等温剩磁等）测 量，获得了红土剖面磁性矿物浓度、粒度和类型等特性随深度的变化曲线以上红土经连二亚硫酸钠－柠檬酸钠－重碳酸钠溶液（ＤＣＢ）处理后的磁性参数变化，根 据红土剖面环境磁学参数及其磁参数幽会的变化可将红土分为３个层段，各层段的磁性矿物特征存在明显的差异，证帝了红土剖面中的磁性载体主要是磁赤铁矿，赤 铁矿和针铁矿，并分离出了球粒
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皖南网纹红土的粒度分布特征及古环境意义 [J].https://doi.org/10.3321/j.issn:1001-7410.2004.02.005 URL Magsci 摘要
安徽宣城向阳剖面高分辨率粒度分析结果表明 :1)网纹红土含有较高的胶结性很强的次生氧化铁 ,样品前处理时单颗粒的分散效果将会显著地影响粒度测试结果。向阳剖面不含 >2mm的砾石 ,砂粒 ( >6 3μm)的含量也很低 ,粘粒 ( <2 μm)和粗粉砂 ( 10～ 5 0 μm)明显富集 ;2 )除底部外 ,向阳剖面粒度组成特征反映了明显的风成特性 ,但不能因此忽视其强风化特征的存在 ,尤其是剖面中、下部的网纹红土。应肯定向阳网纹红土的风成特性 ,但不能简单地称其为风积成因 ;3)向阳剖面磁化率值与粘粒和细颗粒含量无显著正相关性 ,说明磁化率值不能指示网纹红土的风化强度 ;4 )向阳剖面粒度分布特征无法提供该剖面存在多个“沉积—成土”过程旋回的证据。向阳网纹红土更多地体现了其具有原始风成沉积和后期强烈风化的双重特性。
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中国南方红土环境磁学 [J].https://doi.org/10.3321/j.issn:1001-7410.2007.06.017 URL Magsci 摘要
第四纪红土是中国南方古环境演化与气候变迁的最佳载体之一,记录了南方的古地理、古气候环境变迁信息。典型红土剖面由现代红壤层、均质层、网纹层、砾石层或基岩层组成,均质红土磁化率值多在80×10-8~250×10-8m3/kg,网纹红土磁化率约低一个数量级。红土的磁化率-温度（-T）曲线、等温剩磁获得曲线、XRD和TEM分析认为,成土过程产生的细粒磁性矿物（包括磁铁矿、磁赤铁矿和赤铁矿）是红土磁性的主要载体。对红土的岩石磁学和矿物学综合分析认为,红土磁性矿物的含量、粒度、类型等可能指示其形成时期的某种环境变化,红土磁性是南方第四纪环境变迁研究的重要手段,但由于红土的物源以及受后期化学风化改造的复杂性,红土的环境磁学研究需要新的思路和方法。
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中国亚热带风尘沉积物磁学特征对比研究 [J].https://doi.org/10.3969/j.issn.1001-7410.2013.05.09 URL Magsci [本文引用: 4] 摘要
中国亚热带地区的风尘沉积包括均质红土、黄棕色土、网纹红土和下 蜀土等不同类型沉积层.本文选择江西九江(JL)、浙江浦江(PJ)和江苏新港(XG-3)3个剖面,进行了多种磁学参数测量.研究结果表明:1)黄棕色 土与网纹红土在剖面上叠加组成加积型红土剖面构型,两者的磁性矿物含量、类型和磁畴的差异,导致磁化率的不同.黄棕色土磁化率高,磁性矿物含量高,磁性颗 粒以细小的亚铁磁性矿物磁铁矿和磁赤铁矿为主.根据半定量估算,黄棕色土样品中SP颗粒含量大多介于50％ ～ 75％之间,其中的古土壤样品SP颗粒含量多数大于75％.网纹红土磁化率低,磁性矿物含量低,磁性颗粒粒径较黄棕色土粗,矿物类型以不完整反铁磁性矿物 赤铁矿为主.2)下蜀黄土具有较高的x,xfd,SIRM和xARM；x和xfd呈正相关关系(r2 =0.87),黄土层的xARM/SIRM与xARM/x远低于古土壤,反映除较细的粒度组分外,还有较粗的PSD/MD颗粒存在.细颗粒亚铁磁性矿物对 磁化率贡献较大.3)据磁学参数辅以其他理化指标推测,黄棕色土与下蜀黄土形成环境与现在亚热带环境类似,但黄棕色土以较低的粉砂与粘土比值反映其化学风 化作用较下蜀黄土强,显示了一定的纬度效应.4)广泛分布于亚热带地区的网纹红土磁学特征类同,粒度组成和地球化学指标也相似,反映形成时期区域内的自然 要素的地带性分异不及今日明显.另一方面,网纹红土中较高的HIRM、矫顽力和居里温度指示其含有较多的赤铁矿,而且磁性矿物颗粒较其上的黄棕色土粗,全 铁含量略高于黄棕色土,87Sr/86Sr比值也较黄棕色土高,所有这些都佐证网纹红土与黄棕色土可能具有不完全相同的物质来源.
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南方网纹红土内是否可能存在多个“沉积-成土”过程的旋回? [J].https://doi.org/10.3321/j.issn:0023-074X.2003.09.019 URL [本文引用: 4] 摘要
通过对安徽宣城向阳剖面 Munsell指标、风化强度、磁学参数、稳定碳同位素等的研究,提出几点与前期研究者的不同看法:(1)向阳剖面色调曲线与游离态铁(Fed)、铁游离 度(Fed/Fet)、风化淋溶系数(BA)曲线表明,顶部黄棕色土的风化程度偏低,中、下部的风化程度普遍高于上部.除了顶部黄棕色土层,其余各层红色 调深浅的变化,与风化强度无必然的联系.色调的变化可能是次生氧化铁矿物赤铁矿和针铁矿相对含量变化的结果.因而仅以剖面内部不同层次间颜色的变化来判定 存在“沉积-成土”序列,是不充分的.(2)向阳剖面无网纹或网纹发育较弱的层次磁化率(x)较高;而在网纹发育的层次,由于大量超顺磁颗粒(SP)和稳 定
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中国现代土壤磁化率分析及其古气候意义 [J].
通过对全国166个现代表层土 壤样品的磁化率分析,发现黄土高原及周边地区的土壤磁化率是随年均温、年均降水量的增高而增高的。而我国长江以南广大地区的土壤磁化率是随年均温、年均降 水量的增高而降低的(其临界范围大致在年均温15℃左右、年均降水量1100 mm左右)。新疆及周边地区表层土壤磁化率与温度、降水量的关系比较复杂。文中还建立了4次多项式回归方程,并对洛川坡头黄土剖面S_1—S_0的120 个样品的磁化率值进行了古温度、古降水量的估算。
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论华南红色风化壳 [J].https://doi.org/10.5539/esr.v1n2p163 URL [本文引用: 1] |
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Б Б(苏).风化壳及其地球化学 [M]. |
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Environmental Magnetism [M]. |
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Channell J E T.Sedimentary magnetism,environmental magnestism and magnestostratigraphy [J].
Not Available
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Mineralmagnetic characteristics of podzolic soils developed on sand dunes in the Lake Gosciaz catchment, central Poland [J].https://doi.org/10.1016/0031-9201(90)90270-8 URL [本文引用: 1] 摘要
A number of samples from the A 0 , A 2 , B and C horizons have been collected from podzolic soils in the Lake Gosciaz catchment in central Poland. The catchment is very uniform consisting of 2鈥6-m-high sand dunes with sparse stands of pine and a grass undervegetation. Radiocarbon dates of fossil soils covered by dune sand, within the same type of environment as the Lake Gosciaz catchment, indicate that the main dune-forming phase is of Older Dryas age. Magnetic measurements have been carried out on bulk samples and on particle size fractions from the different soil horizons. With respect to our mineral magnetic study it can be concluded that the soils are very uniform over the entire catchment. Relatively high concentrations of magnetic grains are found in the humus layer, particularly in the <4 渭m size fraction, as indicated by the highest X , X fd , SIRM and HIRM values. The most likely mechanism for the magnetic enhancement in these podzolic top soils is continued burning processes. Low magnetic concentrations in the A 2 horizon are due to eluviation and chelation. Local conditions can lead to a range of magnetic minerals precipitating in the B horizon.
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玄武岩发育土壤的磁化率及其机理解析 [J].https://doi.org/10.3321/j.issn:0564-3929.1999.04.015 URL [本文引用: 1] 摘要
应用矿物磁测技术和X－射线衍 射分析对浙江和云南玄武岩发育土壤的磁化率（x）机理进行了研究。浙江玄武岩发育土壤的x为100×10-8～500×10－8m3／kg，云南玄武岩发 育土壤的x500×10-8～2000×10－8m3／kg，合成针铁矿的x为31．99×10-8m3／kg，赤铁矿x为 84．5×10－8m3／kg，且合成氧化铁的x随氧化铁的铝替代量增大而增加。土壤的磁性参数和X－射线衍射分析证明，云南玄武岩发育土壤的x主要由超 顺磁性态（SP）磁赤铁矿和磁铁矿贡献，浙江玄武岩发育土壤的x由原生和次生的磁铁矿和磁赤铁矿贡献，且赤铁矿对土壤x也起到一定的作用。
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Banerjee S K et al.Mechanism of the magnetic susceptibility enhancements of Chinese loess [J].https://doi.org/10.1029/2004JB003249 URL [本文引用: 1] 摘要
Chinese loess/paleosol sequences have been regarded as excellent continental archives for encoding continuous paleoclimatic variations over the past 2.5 Myr. However, the mechanism for magnetic enhancements (especially the low-field mass-specific magnetic susceptibility, 蠂) of Chinese paleosols is still not completely resolved. This study quantifies contributions of aeolian and pedogenic magnetic particles to the bulk magnetic properties of the Chinese loess/paleosols by using a magnetic extraction technique. Magnetic properties of magnetic separates (extractable) and the corresponding residues (nonextractable) for five characteristic samples covering both loesses and paleosols were comprehensively investigated by hysteresis loops, frequency and low-temperature dependence of magnetic susceptibility, and interparametric ratios. Results show that (1) with moderate degrees of pedogenesis (蠂 (10-12) 脳 10mkg, contributions of pedogenically related fine-grained pseudosingle-domain (PSD, 藴100 nm to several microns) particles become significant; (2) pedogenic particles have a narrow grain size distribution concentrated above the SP/SD threshold; and (3) anhysteretic remanent magnetization (ARM) is carried dominantly by SD grains. Moreover, we propose that only the nonextractable fraction of 蠂, saturation magnetization (M) and remanent magnetization (M) show a strong relationship with the degree of pedogenesis. This new interpretation of magnetic enhancements helps us to retrieve more accurate and quantitative paleoclimatic signals recorded by the Chinese loess/paleosol sequences.
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黄土频率磁化率与古气候冷暖变换 [J].https://doi.org/10.1007/s00376-999-0032-1 URL [本文引用: 1] 摘要
本文详细研究和对比了几个区域 的黄土剖面,证明中国黄土地层发育的一致性;根据第5阶段以来黄土磁化率和深海氧同位素曲线特征的比较,证明中国黄土地层的连续性和全球气候变化的一致 性。黄土地层的古气候信息强度与分辨率成反比,是全球信号和区域信号的叠加。黄土高原各地厚度或沉积速率的差别主要是1.7 Ma以来形成的。黄土地层频率磁化率数值随黄土和古土壤层的出现,分别呈波谷和波峰对应,说明在温湿条件下有许多细小(0.03 μm)的铁磁性矿物形成,它可能是导致古土壤磁化率增高的最主要原因。这些磁颗粒的含量反映古气候温湿程度的强弱和持续时间的长短。黄土频率磁化率对古气 候的突变或渐变研究可能具有十分重要的意义。
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花岗岩上发育的亚热带红土岩石磁学特征 [J].https://doi.org/10.3969/j.issn.1001-7410.2014.03.05 URL Magsci [本文引用: 2] 摘要
本文对发育于花岗岩上的两个亚 热带红土剖面进行了系统的岩石磁学研究,测试了磁化率、频率磁化率、等温剩磁、非磁滞剩磁、磁滞回线等常温磁学参数,选取代表性样品进行了高低温岩石磁学 分析,拟探讨亚热带红土磁性矿物的特征及湿热环境下土壤中磁性矿物的转化规律。实验结果表明:亚热带红土的强磁性矿物为磁铁矿、磁赤铁矿;弱磁性矿物为赤 铁矿和针铁矿,滞水土层中含有纤铁矿。花岗岩具有较强的磁性,在其上发育的红土也因此具有较强的磁性。花岗岩中的亚铁磁性矿物的磁畴以多畴占主导地位,随 着风化强度的增强,逐渐形成较细粒的超顺磁与单畴磁性矿物。亚热带红土中的磁赤铁矿与位于半干旱区黄土高原成土作用形成的磁赤铁矿存在着磁学性质上的差 异,表现为具有更高的居里点(约600℃和640℃),可能说明亚热带红土中的磁赤铁矿粒径更粗。两个剖面在磁学性质上存在着明显的差异,泉州剖面磁性矿 物以磁铁矿为主,磁化率最高可达1823×10~(-8)m~3/kg,平均值为1033.1×10~(-8)m~3/kg,具有较低的剩磁矫顽力;福州 剖面磁性矿物以磁铁矿和部分热稳定磁赤铁矿为主,磁化率最高为385.73×10~(-8)m~3/kg,平均值为91.5×10~(-8)m~3 /kg。基于磁学参数分析,认为母质与后期成土作用共同造成了两个剖面的磁学性质差异,但后者起主导作用。磁化率在两个剖面中,均随着深度减小而减小,与 温带地区表层土磁化率增强有很大区别。湿热环境条件下,强磁性矿物溶解或转化为弱磁性矿物的程度主导剖面磁化率变化。
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南方第四纪红土是研究古环境变化的重要载体.本文对采自江西九江 的九庐公路红土剖面进行了详细的环境磁学研究,拟探讨多项磁参数在提取南方红土古环境信息方面的价值.结果显示,红土剖面上段的弱风化层,磁化率随着成土 作用的增强而增大,反映了成土过程中产生的细颗粒亚铁磁性矿物导致的磁化率增加;而在剖面下段强风化的网纹红土层,表现为磁化率和退磁参数S比值下降但硬 剩磁显著增加,反映强风化成土作用下不完整反铁磁性矿物的富集.与单一磁化率指标相比,多项磁学参数的综合运用可以在南方红土古气候重建领域发挥重要作 用.
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亚热带和热带土壤的磁化率 [J].
亚热带和热带土壤的磁化率X变 化大,高的达2000—6000单位(昆明玄武岩红壤),低的只几个单位(沼泽土、强还原性水稻土、磷质石灰土)。大体上是:自型土潮土水稻土沼泽土。在 自型土中,砖红壤、红壤的X值大于石灰岩土和紫色土。红壤的磁性受母岩和发育度的影响大。各地的玄武岩红壤的X值为3×10~2—6×10~3单位,其他 红壤多为100—40单位(中性和酸性岩浆岩,多数沉积岩),或40—10单位(一部分石灰岩、凝灰岩)。灼烧土壤而得到的X-t曲线和“转化率”E,可 粗略地反映磁赤铁矿生成的相对程度,进而估计红壤化的程度,似可在红壤的诊断、鉴定中试用。
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中国南方红土与第四纪环境变迁的初步研究 [J].
本文简述了我国南方红土的形成时期，讨论了安徽省宣城剖面的特征及其成因，并对此剖面进行了ESR年代学的研究，建立了此剖面的时间坐标。作者在此基础上，根据土壤地层学、磁化率、全氧化铁含量及有机质的含量分析和碳同位素测定等手段，将中更新世以来的沉积物──红土（古土壤）划分为8个沉积旋回，代表了8个大的气候旋回，并与我国北方黄土-古土壤系列具有明显的可比性。
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海南玄武岩风化壳剖面磁化率变化特征 [J].https://doi.org/10.3969/j.issn.1001-5221.2010.05.004 URL [本文引用: 1] 摘要
我国华南地区分布较广的玄武岩风化壳剖面由于代表了自基岩开始向 上逐步风化成壤作用加强的过程,具有深入研究土壤磁学参数与成壤强度之间关系的潜力.对来自海南文昌南阳的新生代玄武岩风化壳剖面的磁化率测量和分析表 明:该剖面低频质量磁化率(xlf)和高频质量磁化率(xhf)具有相同的变化趋势,总体而言,随着成壤强度的增加先缓慢降低而后迅速增加;与此同时,百 分频率磁化率(xf1%)则从玄武岩基岩到风化壳顶部呈明显的升高趋势;低频质量磁化率与高频质量磁化率的差值(xfd)则随着成壤强度的增加先缓慢升高 而后迅速升高.这些数据暗示,各种磁学参数与成壤强度之间的关系较为复杂,相对而言,百分频率磁化率(xfd%)在一个较广的成壤强度范同内可能是一个较 好的成壤强度指示器.初步研究结果表明,对该类型剖面更为深人的环境磁学和岩石磁学研究,有可能更详细地了解风化成壤过程中磁学参数变化的机理.
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华南地区发育于不同母岩之上的表土磁化率特征及其意义 [J].https://doi.org/10.3321/j.issn:1001-7410.2007.04.022 URL Magsci [本文引用: 1] 摘要
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