中亚塔吉克斯坦南部黄土剖面上下部地层磁化率明显差异原因浅析
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摘要
中亚塔吉克斯坦南部的黄土序列与中国黄土高原相似,呈现黄土-古土壤交替的特征,前人研究发现塔吉克斯坦黄土序列中以PC3为界的下部黄土与古土壤单元磁化率明显低于上部地层,目前对这一现象尚无合理的古气候解释。本文对中亚塔吉克斯坦南部Darai Kalon黄土剖面的典型样品进行系统的矿物磁学研究以及漫反射光谱测量,结果表明,从黄土序列的下部到上部,亚铁磁性矿物的总量以及超顺磁与单畴磁性颗粒的含量均呈增长的趋势,与此同时,硬磁性组份(如赤铁矿或针铁矿)的含量逐渐减少,这可能指示成壤作用强度随时间增强。赤铁矿的适宜生长条件为高温干燥环境,因此黄土序列下部的较高赤铁矿含量可能支持气候逐渐变湿的推论,即下部地层沉积时期气候偏干,成壤作用较弱,古土壤中含较少的亚铁磁性矿物,超顺磁与单畴磁性矿物颗粒较少,故下部地层的磁化率较低。然而,光谱测量数据显示,下部地层针铁矿含量高于上部地层,由于针铁矿的适宜生长条件为湿润环境,其含量向上逐渐降低的趋势当指示气候逐渐变干。因此,PC3以下地层的较低磁化率也可能是过于湿润的环境溶解超顺磁和单畴磁性矿物颗粒造成的。尽管高场(达2T)等温剩磁结果显示上部地层中以赤铁矿为主的硬磁性矿物含量较少,但上部地层红度(a*)与赤铁矿含量之间较弱的相关性指示基体效应可能对光谱测量结果产生强烈的影响,导致对赤铁矿光谱数据的解释存在很大的不确定性。针铁矿含量与磁化率的良好负相关性的确指示从下至上气候变干的趋势,这一趋势与该地区前人的孢粉学和地球化学研究结果一致。以上研究结果表明,对于中亚塔吉克斯坦南部黄土-古土壤序列的磁化率乃至矿物磁学数据的古气候解释非常复杂,在中亚黄土研究中应用基于中国黄土磁学研究的模式需要谨慎,有必要结合多指标进行综合分析。
Loess sequences in southern Tajikistan, central Asia are characterized by the occurrence of alternating loess and pedocomplexes, a feature which is similar to that in the Loess Plateau of north-central China. Previous studies of Tajik loess revealed that below the third pedocomplex(PC3), the loess units and pedocomplexes have distinctly lower magnetic susceptibility than the upper part. No conclusive consensus has been reached on the paleoclimatic interpretation of such a pattern. Here, results of a systematic mineral magnetic study in combination with spectrophotometric measurements on selected samples from Darai Kalon loess section in the southern Tajikistan, central Asia are presented. The mineral magnetic properties suggest increasing concentrations of the ferromagnetic minerals as well as the superparamagnetic and single domain magnetic grains, together with the decreasing hard magnetic components(i.e. contents of hematite or goethite), from the lower part to the upper part of the sequence, which would point to enhanced pedogenesis through time. Such paleoclimate inference is supported by the higher content of hematite in the lower part of the sequence on the assumption that higher temperature and lower precipitation favor the formation of hematite. In this case, the dry climate in the lower part leads to weak pedogenesis. Therefore, there are less superparamagnetic and single domain magnetic grains, which are responsible for the reduced magnetic susceptibility in the lower part. However, the upwards decreasing goethite content revealed by the measurements of diffuse reflectance spectrophotometric data suggests a change towards a drying climate, as formation of goethite requires wet conditions. In this case, the lower magnetic susceptibility below the PC3 may be manifestation of dissolution of superparamagnetic and single domain magnetic grains due to a prevailing humid environment. While the high field(up to 2 Tesla) isothermal remanence shows that the upper part has a lower content of hematite-dominated hard magnetic components, the poor correlation between redness(a*) and the content of hematite in the upper part indicates the strong influence of the matrix effect in the diffuse reflectance spectrophotometric data. Hence, there exists a major uncertainty in the interpretation of the spectrophotometric result of hematite. The overall good negative correlation between the content of goethite and magnetic susceptibility may be interpreted as indicating a trend of drying climate from the lower part to the upper part of the sequence. Such an interpretation is compatible with previous palynological and geochemical studies in the region. This study highlights the complication in the paleoclimate interpretation of the magnetic susceptibility and even mineral magnetic data for loess-pedocomplex sequence in southern Tajikistan. It calls for caution in the application of the models based on the magnetic investigations of Chinese loess and indicates the need of the use of the multiple proxies.
Loess sequences in southern Tajikistan, central Asia are characterized by the occurrence of alternating loess and pedocomplexes, a feature which is similar to that in the Loess Plateau of north-central China. Previous studies of Tajik loess revealed that below the third pedocomplex(PC3), the loess units and pedocomplexes have distinctly lower magnetic susceptibility than the upper part. No conclusive consensus has been reached on the paleoclimatic interpretation of such a pattern. Here, results of a systematic mineral magnetic study in combination with spectrophotometric measurements on selected samples from Darai Kalon loess section in the southern Tajikistan, central Asia are presented. The mineral magnetic properties suggest increasing concentrations of the ferromagnetic minerals as well as the superparamagnetic and single domain magnetic grains, together with the decreasing hard magnetic components(i.e. contents of hematite or goethite), from the lower part to the upper part of the sequence, which would point to enhanced pedogenesis through time. Such paleoclimate inference is supported by the higher content of hematite in the lower part of the sequence on the assumption that higher temperature and lower precipitation favor the formation of hematite. In this case, the dry climate in the lower part leads to weak pedogenesis. Therefore, there are less superparamagnetic and single domain magnetic grains, which are responsible for the reduced magnetic susceptibility in the lower part. However, the upwards decreasing goethite content revealed by the measurements of diffuse reflectance spectrophotometric data suggests a change towards a drying climate, as formation of goethite requires wet conditions. In this case, the lower magnetic susceptibility below the PC3 may be manifestation of dissolution of superparamagnetic and single domain magnetic grains due to a prevailing humid environment. While the high field(up to 2 Tesla) isothermal remanence shows that the upper part has a lower content of hematite-dominated hard magnetic components, the poor correlation between redness(a*) and the content of hematite in the upper part indicates the strong influence of the matrix effect in the diffuse reflectance spectrophotometric data. Hence, there exists a major uncertainty in the interpretation of the spectrophotometric result of hematite. The overall good negative correlation between the content of goethite and magnetic susceptibility may be interpreted as indicating a trend of drying climate from the lower part to the upper part of the sequence. Such an interpretation is compatible with previous palynological and geochemical studies in the region. This study highlights the complication in the paleoclimate interpretation of the magnetic susceptibility and even mineral magnetic data for loess-pedocomplex sequence in southern Tajikistan. It calls for caution in the application of the models based on the magnetic investigations of Chinese loess and indicates the need of the use of the multiple proxies.
引文
[1]刘东生.中国的黄土堆积:中国黄土分布图说明书.北京:科学出版社,1965
[2]刘东生.黄土与环境.北京:科学出版社,1985
[3]Dodonov A E,Baiguzina L L.Loess stratigraphy of Central Asia:palaeoclimatic and palaeoenvironmental aspects.Quaternary Science Reviews,1995,14(7/8):707?720
[4]Kukla G,An Z S.Loess stratigraphy in Central China.Palaeogeography Palaeoclimatology Palaeoecology,1989,72(89):203?225
[5]Ding Z L,Ranov V,Yang S L,et al.The loess record in southern Tajikistan and correlation with Chinese loess.Earth&Planetary Science Letters,2002,200(3):387?400
[6]Dodonov A E,Gorshkov A I,Verkhovtseva N V,et al.New data on the composition of magnetic minerals from paleosols of Southern Tajikistan.Lithology&Mineral Resources,2002,37(2):186?193
[7]Frechen M,Dodonov A E.Loess chronology of the Middle and Upper Pleistocene in Tadjikistan.Geologische Rundschau,1998,87(1):2?20
[8]Dodonov A E,Sadchikova T A,Sedov S N,et al.Multidisciplinary approach for paleoenvironmental reconstruction in loess-paleosol studies of the Darai Kalon section,Southern Tajikistan.Quaternary International,2006,152/153(3):48?58
[9]周力平,Shackleton N J,Dodonov A E.欧亚黄土中古地磁极性界线的地层学解释.第四纪研究,2000,20(2):196?202
[10]Yang S,Ding F,Ding Z.Pleistocene chemical weathering history of Asian arid and semi-arid regions recorded in loess deposits of China and Tajikistan.Geochimica et Cosmochimica Acta,2006,70(7):1695?1709
[11]An Z S,Kukla G J,Porter S C,et al.Magnetic susceptibility evidence of monsoon variation on the loess plateau of central China during the last 130,000years.Quaternary Research,1991,36(1):29?36
[12]Zhou L P,Oldfield F,Wintle A G,et al.Partly pedogenic origin of magnetic variations in Chinese loess.Nature,1990,346:737?739
[13]Maher B A,Thompson R.Mineral magnetic record of Chinese loess and paleosols.Geology,1991,19:3?6
[14]吕厚远,韩家懋.中国现代土壤磁化率分析及其古气候意义.中国科学:B辑,1994(12):1290?1297
[15]LüH Y,Wu N Q,Liu T S,et al.Seasonal climatic variation recorded by phytolith assemblages from the Baoji loess sequence in central China over the last150 000 a.Science in China:Ser D,1996,39(6):629?639
[16]Porter S C,Hallet B,Wu X,et al.Dependence of near-surface magnetic susceptibility on dust accumulation rate and precipitation on the Chinese Loess Plateau.Quaternary Research,2001,55(3):271?283
[17]Hao Q Z,Guo Z T.Spatial variations of magnetic susceptibility of Chinese loess for the last 600 kyr:implications for monsoon evolution.Journal of Geophysical Research Solid Earth,2005,110(B12101):1?10
[18]Kukla G,Heller F,Liu X M,et al.Pleistocene climates in China dated by magnetic susceptibility.Geology,1988,16(9):811?814
[19]Evans M E,Heller F.Magnetic enhancement and palaeoclimate:study of a loess/palaeosol couplet across the Loess Plateau of China.Geophysical Journal International,1994,117(1):257?264
[20]Hunt C P,Banerjee S K,Han J M,et al.Rockmagnetic proxies of climate change in the loesspalaeosol sequences of the western Loess Plateau of China.Geophysical Journal of the Royal Astronomical Society,1995,123(1):232?244
[21]Liu Q S,Jackson M J,Banerjee S K,et al.Mechanism of the magnetic susceptibility enhancements of the Chinese loess.Journal of Geophysical Research Solid Earth,2004,109(B12):1?16
[22]Liu Q S,Torrent J,Maher B A,et al.Quantifying grain size distribution of pedogenic magnetic particles in Chinese loess and its significance for pedogenesis.Journal of Geophysical Research Solid Earth,2005,110(B11):1?7
[23]Ding Z L,Yu Z W,Liu T S.Progress in loess research(Part 3):time scale.Quaternary Sciences,1991,4:336?348
[24]刘秀铭,夏敦胜,刘东生,等.中国黄土和阿拉斯加黄土磁化率气候记录的两种模式探讨.第四纪研究,2007,27(2):210?220
[25]夏敦胜,陈发虎,马剑英,等.新疆伊犁地区典型黄土磁学特征及其环境意义初探.第四纪研究,2010,30(5):902?910
[26]Liu Z F,Liu Q S,Torrent J,et al.Testing the magnetic proxy XFD/HIRM for quantifying paleoprecipitation in modern soil profiles from Shaanxi Province,China.Global and Planetary Change,2013,110:368-378
[27]刘秀铭,吕镔,毛学刚,等.风积地层中铁矿物随环境变化及其启示.第四纪研究,2014,34(3):443?457
[28]刘秀铭,刘东生,Heller F,et al.中国黄土磁颗粒分析及其古气候意义.中国科学:B辑,1991(6):639?644
[29]Deng C,Zhu R,Verosub K L,et al.Mineral magnetic properties of loess/paleosol couplets of the central loess plateau of China over the last 1.2 Myr.Journal of Geophysical Research Solid Earth,2004,109(B1):1?13
[30]Deng C L,Vidic N J,Verosub K L,et al.Mineral magnetic variation of the Jiaodao Chinese loess/paleosol sequence and its bearing on long-term climatic variability.Journal of Geophysical Research Solid Earth,2005,110(B03):1?17
[31]Deng C L,Shaw J,Liu Q S,et al.Mineral magnetic variation of the Jingbian loess/paleosol sequence in the northern Loess Plateau of China:implications for Quaternary development of Asian aridification and cooling.Earth&Planetary Science Letters,2006,241(1/2):248?259
[32]Wu Y,Zhu Z Y,Rao Z G,et al.Mid-Late Quaternary loess-paleosol sequence in Lantian’s Yushan,China:an environmental magnetism approach and its paleoclimatic significance.Chinese Science Bulletin,2010,55(26):2989?3000
[33]李兴文,林杉,敖红,等.河南三门峡水沟?会兴沟旧石器遗址的黄土地层研究.地层学杂志,2017,41(2):166?172
[34]Song Y,Hao Q,Ge J,et al.Quantitative relationships between magnetic enhancement of modern soils and climatic variables over the Chinese Loess Plateau.Quaternary International,2014,334/335(1):119?131
[35]Gao X B,Hao Q Z,Wang L,et al.The different climatic response of pedogenic hematite and ferrimagnetic minerals:evidence from particle-sized modern soils over the Chinese Loess Plateau.Quaternary Science Reviews,2018,179:69?86
[36]Barranco Jr F T,Balsam W L,Deaton B C.Quantitative reassessment of brick red lutites:evidence from reflectance spectrophotometry.Marine Geology,1989,89(3):299?314
[37]Deaton B C,Balsam W L.Visible spectroscopy-a rapid method for determining hematite and goethite concentration in geological materials.J sediment petrol,1991,61(4):628?632
[38]Ji J F,William B,Chen J.Mineralogic and climatic interpretations of the Luochuan Loess Section(China)based on diffuse reflectance spectrophotometry.Quaternary Research,2001,56(1):23?30
[39]Ji J F,Balsam W,Chen J,et al.Rapid and quantitative measurement of hematite and goethite in the chinese loess-paleosol sequence by diffuse reflectance spectroscopy.Clays&Clay Minerals,2002,50(2):208?216
[40]Ji J F,Chen J,Balsam W,et al.High resolution hematite/goethite records from Chinese loess sequences for the last glacial-interglacial cycle:rapid climatic response of the East Asian Monsoon to the tropical Pacific.Geophysical Research Letters,2004,31:347?348
[41]季峻峰,陈骏,Balsam W,等.黄土剖面中赤铁矿和针铁矿的定量分析与气候干湿变化研究.第四纪研究,2007,27(2):221?229
[42]Balsam W,Ji J F,Chen J.Climatic interpretation of the Luochuan and Lingtai loess sections,China,based on changing iron oxide mineralogy and magnetic susceptibility.Earth&Planetary Science Letters,2004,223(3):335?348
[43]Heller F,Liu T.Magnetostratigraphical dating of loess deposits in China.Nature,1982,300:431?433
[44]Robertson D J,France D E.Discrimination of remanence-carrying minerals in mixtures,using isothermal remanent magnetisation acquisition curves.Physics of the Earth&Planetary Interiors,1994,82(3):223?234
[45]Kruiver P P,Dekkers M J,Heslop D.Quantification of magnetic coercivity components by the analysis of acquisition curves of isothermal remanent magnetisation.Earth&Planetary Science Letters,2001,189(3/4):269?276
[46]Heslop D,Dekkers M J,Kruiver P P,et al.Analysis of isothermal remanent magnetization acquisition curves using the expectation-maximization algorithm.Geophysical Journal of the Royal Astronomical Society,2002,148(1):58?64
[47]Torrent J,Barron V,Liu Q S.Magnetic enhancement is linked to and precedes hematite formation in aerobic soil.Geophysical Research Letters,2006,33(2):140?165
[48]Guo X L,Liu X M,Li P Y,et al.The magnetic mechanism of paleosol S5 in the Baoji section of the southern Chinese Loess Plateau.Quaternary International,2013,306:129?136
[49]夏敦胜,马剑英,王冠,等.环境磁学及其在西北干旱区环境研究中的问题.地学前缘,2006,13(3):168?179
[2]刘东生.黄土与环境.北京:科学出版社,1985
[3]Dodonov A E,Baiguzina L L.Loess stratigraphy of Central Asia:palaeoclimatic and palaeoenvironmental aspects.Quaternary Science Reviews,1995,14(7/8):707?720
[4]Kukla G,An Z S.Loess stratigraphy in Central China.Palaeogeography Palaeoclimatology Palaeoecology,1989,72(89):203?225
[5]Ding Z L,Ranov V,Yang S L,et al.The loess record in southern Tajikistan and correlation with Chinese loess.Earth&Planetary Science Letters,2002,200(3):387?400
[6]Dodonov A E,Gorshkov A I,Verkhovtseva N V,et al.New data on the composition of magnetic minerals from paleosols of Southern Tajikistan.Lithology&Mineral Resources,2002,37(2):186?193
[7]Frechen M,Dodonov A E.Loess chronology of the Middle and Upper Pleistocene in Tadjikistan.Geologische Rundschau,1998,87(1):2?20
[8]Dodonov A E,Sadchikova T A,Sedov S N,et al.Multidisciplinary approach for paleoenvironmental reconstruction in loess-paleosol studies of the Darai Kalon section,Southern Tajikistan.Quaternary International,2006,152/153(3):48?58
[9]周力平,Shackleton N J,Dodonov A E.欧亚黄土中古地磁极性界线的地层学解释.第四纪研究,2000,20(2):196?202
[10]Yang S,Ding F,Ding Z.Pleistocene chemical weathering history of Asian arid and semi-arid regions recorded in loess deposits of China and Tajikistan.Geochimica et Cosmochimica Acta,2006,70(7):1695?1709
[11]An Z S,Kukla G J,Porter S C,et al.Magnetic susceptibility evidence of monsoon variation on the loess plateau of central China during the last 130,000years.Quaternary Research,1991,36(1):29?36
[12]Zhou L P,Oldfield F,Wintle A G,et al.Partly pedogenic origin of magnetic variations in Chinese loess.Nature,1990,346:737?739
[13]Maher B A,Thompson R.Mineral magnetic record of Chinese loess and paleosols.Geology,1991,19:3?6
[14]吕厚远,韩家懋.中国现代土壤磁化率分析及其古气候意义.中国科学:B辑,1994(12):1290?1297
[15]LüH Y,Wu N Q,Liu T S,et al.Seasonal climatic variation recorded by phytolith assemblages from the Baoji loess sequence in central China over the last150 000 a.Science in China:Ser D,1996,39(6):629?639
[16]Porter S C,Hallet B,Wu X,et al.Dependence of near-surface magnetic susceptibility on dust accumulation rate and precipitation on the Chinese Loess Plateau.Quaternary Research,2001,55(3):271?283
[17]Hao Q Z,Guo Z T.Spatial variations of magnetic susceptibility of Chinese loess for the last 600 kyr:implications for monsoon evolution.Journal of Geophysical Research Solid Earth,2005,110(B12101):1?10
[18]Kukla G,Heller F,Liu X M,et al.Pleistocene climates in China dated by magnetic susceptibility.Geology,1988,16(9):811?814
[19]Evans M E,Heller F.Magnetic enhancement and palaeoclimate:study of a loess/palaeosol couplet across the Loess Plateau of China.Geophysical Journal International,1994,117(1):257?264
[20]Hunt C P,Banerjee S K,Han J M,et al.Rockmagnetic proxies of climate change in the loesspalaeosol sequences of the western Loess Plateau of China.Geophysical Journal of the Royal Astronomical Society,1995,123(1):232?244
[21]Liu Q S,Jackson M J,Banerjee S K,et al.Mechanism of the magnetic susceptibility enhancements of the Chinese loess.Journal of Geophysical Research Solid Earth,2004,109(B12):1?16
[22]Liu Q S,Torrent J,Maher B A,et al.Quantifying grain size distribution of pedogenic magnetic particles in Chinese loess and its significance for pedogenesis.Journal of Geophysical Research Solid Earth,2005,110(B11):1?7
[23]Ding Z L,Yu Z W,Liu T S.Progress in loess research(Part 3):time scale.Quaternary Sciences,1991,4:336?348
[24]刘秀铭,夏敦胜,刘东生,等.中国黄土和阿拉斯加黄土磁化率气候记录的两种模式探讨.第四纪研究,2007,27(2):210?220
[25]夏敦胜,陈发虎,马剑英,等.新疆伊犁地区典型黄土磁学特征及其环境意义初探.第四纪研究,2010,30(5):902?910
[26]Liu Z F,Liu Q S,Torrent J,et al.Testing the magnetic proxy XFD/HIRM for quantifying paleoprecipitation in modern soil profiles from Shaanxi Province,China.Global and Planetary Change,2013,110:368-378
[27]刘秀铭,吕镔,毛学刚,等.风积地层中铁矿物随环境变化及其启示.第四纪研究,2014,34(3):443?457
[28]刘秀铭,刘东生,Heller F,et al.中国黄土磁颗粒分析及其古气候意义.中国科学:B辑,1991(6):639?644
[29]Deng C,Zhu R,Verosub K L,et al.Mineral magnetic properties of loess/paleosol couplets of the central loess plateau of China over the last 1.2 Myr.Journal of Geophysical Research Solid Earth,2004,109(B1):1?13
[30]Deng C L,Vidic N J,Verosub K L,et al.Mineral magnetic variation of the Jiaodao Chinese loess/paleosol sequence and its bearing on long-term climatic variability.Journal of Geophysical Research Solid Earth,2005,110(B03):1?17
[31]Deng C L,Shaw J,Liu Q S,et al.Mineral magnetic variation of the Jingbian loess/paleosol sequence in the northern Loess Plateau of China:implications for Quaternary development of Asian aridification and cooling.Earth&Planetary Science Letters,2006,241(1/2):248?259
[32]Wu Y,Zhu Z Y,Rao Z G,et al.Mid-Late Quaternary loess-paleosol sequence in Lantian’s Yushan,China:an environmental magnetism approach and its paleoclimatic significance.Chinese Science Bulletin,2010,55(26):2989?3000
[33]李兴文,林杉,敖红,等.河南三门峡水沟?会兴沟旧石器遗址的黄土地层研究.地层学杂志,2017,41(2):166?172
[34]Song Y,Hao Q,Ge J,et al.Quantitative relationships between magnetic enhancement of modern soils and climatic variables over the Chinese Loess Plateau.Quaternary International,2014,334/335(1):119?131
[35]Gao X B,Hao Q Z,Wang L,et al.The different climatic response of pedogenic hematite and ferrimagnetic minerals:evidence from particle-sized modern soils over the Chinese Loess Plateau.Quaternary Science Reviews,2018,179:69?86
[36]Barranco Jr F T,Balsam W L,Deaton B C.Quantitative reassessment of brick red lutites:evidence from reflectance spectrophotometry.Marine Geology,1989,89(3):299?314
[37]Deaton B C,Balsam W L.Visible spectroscopy-a rapid method for determining hematite and goethite concentration in geological materials.J sediment petrol,1991,61(4):628?632
[38]Ji J F,William B,Chen J.Mineralogic and climatic interpretations of the Luochuan Loess Section(China)based on diffuse reflectance spectrophotometry.Quaternary Research,2001,56(1):23?30
[39]Ji J F,Balsam W,Chen J,et al.Rapid and quantitative measurement of hematite and goethite in the chinese loess-paleosol sequence by diffuse reflectance spectroscopy.Clays&Clay Minerals,2002,50(2):208?216
[40]Ji J F,Chen J,Balsam W,et al.High resolution hematite/goethite records from Chinese loess sequences for the last glacial-interglacial cycle:rapid climatic response of the East Asian Monsoon to the tropical Pacific.Geophysical Research Letters,2004,31:347?348
[41]季峻峰,陈骏,Balsam W,等.黄土剖面中赤铁矿和针铁矿的定量分析与气候干湿变化研究.第四纪研究,2007,27(2):221?229
[42]Balsam W,Ji J F,Chen J.Climatic interpretation of the Luochuan and Lingtai loess sections,China,based on changing iron oxide mineralogy and magnetic susceptibility.Earth&Planetary Science Letters,2004,223(3):335?348
[43]Heller F,Liu T.Magnetostratigraphical dating of loess deposits in China.Nature,1982,300:431?433
[44]Robertson D J,France D E.Discrimination of remanence-carrying minerals in mixtures,using isothermal remanent magnetisation acquisition curves.Physics of the Earth&Planetary Interiors,1994,82(3):223?234
[45]Kruiver P P,Dekkers M J,Heslop D.Quantification of magnetic coercivity components by the analysis of acquisition curves of isothermal remanent magnetisation.Earth&Planetary Science Letters,2001,189(3/4):269?276
[46]Heslop D,Dekkers M J,Kruiver P P,et al.Analysis of isothermal remanent magnetization acquisition curves using the expectation-maximization algorithm.Geophysical Journal of the Royal Astronomical Society,2002,148(1):58?64
[47]Torrent J,Barron V,Liu Q S.Magnetic enhancement is linked to and precedes hematite formation in aerobic soil.Geophysical Research Letters,2006,33(2):140?165
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