Purple soils are a type of azonal soils with weak background magnetic properties,which make it useful for studying the relationship between soil magnetic minerals and soil-forming factors in the initial stage of pedogenesis.However,so far there are few environmental magnetic studies of purple soils in China.We studied a purple soil profile （27°44’24″N,118°00’36″E;altitude 216.3 m） in Wuyishan City,Fujian Province,China,termed the WYS section.The profile is developed on Cretaceous purplish red silty mudstone and is 0.9-m thick;it has a typical humus-rich A horizon,overlying the parent material C horizon.We collected seven samples from the A horizon（0～30 cm） at 5-cm intervals,and six samples from the underlying C horizon,at 10-cm intervals.Magnetic parameters,chromaticity index,diffuse reflectance spectroscopy（DRS） and major element contents were measured on all the samples,with the aim of determining the pedogenic significance of the magnetic properties.The principal results are as follows:（1） The most abundant magnetic mineral throughout the profile was the imperfect antiferromagnetic mineral hematite.There were minor differences in the magnetic properties of the A and C horizons.The content of the ferrimagnetic mineral magnetite was slightly higher in the A horizon,and a small quantity of the iron oxyhydroxide goethite was also present.Additionally,the content of superparamagnetic （SP） particles was higher in the A horizon.（2） The parent material of the WYS section,purplish red silty mudstone,is susceptible to physical weathering,but the degree of chemical weathering is relatively weak,which is consistent with the short duration of pedogenesis.Therefore,the degree of magnetic mineral transformation of the parent rock was limited,despite the humid and warm climate.The parent material and the duration of pedogenesis are the dominant factors affecting the magnetic properties of the purple soil.（3） During pedogenesis,a small quantity of hematite in the weathered crust of the purple silty mudstone is reduced under the combined influences of organic matter,moisture,and other factors,forming fine-grained magnetite,including SP particles.Additionally,a magnetite rim may develop around a core of hematite,which contributes to the observed slight enhancement of the magnetic properties of the A horizon.The magnetic properties of this purplish soil are only slightly altered by the weak pedogenic environment,which indicates that its magnetic properties are a sensitive indictor of pedogenic intensity.

东欧黄土的磁性变化模式与中国黄土最为相似,均以成壤模式为主,因而对其进行系统的岩石磁学研究不仅有利于更好地理解东欧黄土自身所记录的古环境信息,而且有助于对以成壤模式为主的黄土磁性变化机理的认知.本研究对塞尔维亚北部Titel黄土高原中更新世晚期以来的70个黄土/古土壤样品进行了详细的岩石磁学分析,所得结果带给我们一些新的认识:(1)Titel高原古土壤层的磁化率普遍低于100×10-8m3 kg-1,远低于相似气候条件下中国黄土高原的古土壤层,但用于表征其磁性矿物粒径分布的相关参数却与中国黄土相差不大,亚铁磁性矿物含量的差别是导致两地古土壤层磁化率差异的主要因素,但形成该差别的具体原因还有待探究;(2)基于对热磁曲线加热前后磁化强度的变化量分析发现,热不稳定磁赤铁矿相对含量的变化在过去四次冰期-间冰期呈逐渐增大的趋势,与近年来的研究所认为的自中更新世以来潘诺尼亚盆地内大陆性气候逐渐增强的趋势相一致,这一发现不仅为该区域古环境演化的长期趋势提供了独立的环境磁学证据,而且表明黄土中磁赤铁矿含量的变化可能对于环境更为敏感.

选择了关注较少,第四纪红土分布最西界——四川成都平原中的一个第四纪红土剖面作为研究对象,通过系统的环境磁学分析,结合色度和常量地球化学元素指标,探讨磁学参数的环境指示意义,探寻适用的气候代用指标.结果表明:(1)成都地区第四纪红土剖面经历了细粒亚铁磁性矿物转化分解、剖面整体呈低磁性、磁性矿物主要为反铁磁性矿物、磁性颗粒以假单畴(PSD)和多畴(MD)的粗颗粒为主.(2)剖面弱网纹层成土强度较弱、亚铁磁性矿物含量较高、磁性较强、磁性矿物粒径较细;典型网纹层成土强度较高、磁性较弱、磁性颗粒较粗.(3)剖面土壤发育序列的CIA、磁学特征的变化指示了当地气候趋于冷干,且不及同时期的长江中下游地区暖湿.(4)反映剖面反铁磁性矿物的赤铁矿、针铁矿信息的色度参数与CIA对应良好,可以作为南方地区古气候变化研究的代用指标.

对我国亚热带地区发育于花岗岩之上的一个黄红壤剖面进行了系统的环境磁学测量,对土壤样品的磁化率、等温剩磁、磁滞回线等常温磁学参数进行测量,对代表性样品进行热磁分析,并结合色度、常量地球化学元素和漫反射光谱参数,探讨亚热带黄红壤的磁性特征,以及在相对湿冷的气候条件下,黄红壤中的磁性矿物具有怎样的转化规律.结果表明:亚热带黄红壤中强磁性矿物为亚铁磁性的磁铁矿、磁赤铁矿,弱磁性矿物为反铁磁性的赤铁矿、针铁矿.随着成土作用/风化作用增强,磁性矿物颗粒变细.母质和气候条件是影响区域磁性差异的重要因素,次生磁性矿物(特别是赤铁矿与针铁矿)的含量主要受气候条件控制.在相对湿冷的气候条件下,磁性矿物的转化以强磁性的磁铁矿与磁赤铁矿转化为弱磁性的赤铁矿与针铁矿为主.气温(而非降水)是湿润亚热带地区花岗岩风化壳上发育土壤中针铁矿和赤铁矿含量以及相对比例的主导影响因素.

对天山北麓黄土分布特点与形成年代的研究,以及以此为载体应用各代用指标的古气候重建已经取得了不少进展.在前人工作的基础上,选取黄土—古土壤序列分明,底部S3古土壤发育的鹿角湾剖面为主要研究对象,结合天山北麓的其他多个典型黄土剖面,运用色度、粒度、常量地球化学元素含量和环境磁学参数等指标,探讨大约30万年以来的古气候演变.鹿角湾黄土实验结果显示,各古气候代用指标随剖面深度变化与黄土—古土壤更替大概一致,剖面上部(L2及其以上)与下部区别明显.粒度分布揭示黄土物源输入主要受控于两股不同风系,随黄土古土壤的更替两者的主次地位发生变化.环境磁学实验结果显示,剖面下部磁性弱,频率磁化率低,但古土壤层稳定单畴含量较高,反映湿润成壤环境下超顺磁亚铁磁性矿物溶解或转化为弱磁性矿物;剖面上部比剖面下部的磁性要强,磁性矿物粒度更粗;S0为磁性成壤增强模式,与其他黄土古土壤层不同.再结合其他典型剖面的记录,可以推断研究区30万年以来有干旱化的趋势,但S2发育阶段总体上可能比S3发育阶段略为湿润,这一阶段之后气候明显变干,S1发育阶段明显比S2与S3发育阶段干旱,干旱化趋势一直保持至全新世开始之前.

福建南部漳浦零星分布有砖红壤,是中国砖红壤分布的北界.该地区属南亚热带,纬度地带性土壤为赤红壤,而砖红壤是热带地区的纬度地带性土壤.漳浦砖红壤形成时期气候条件如何?是否可以反映气候带的变迁?这是值得深入研究的问题.基于此,通过系统的环境磁学分析,结合漫反射光谱、色度和常量地球化学元素指标,类比漳浦砖红壤和热带地区的广东徐闻现代砖红壤磁学特征的异同,探讨其环境指示意义.结果表明:(1)漳浦砖红壤中的磁性矿物以磁赤铁矿和赤铁矿为主,赤铁矿含量高于磁赤铁矿,磁赤铁矿主导剖面的磁学性质.磁性矿物颗粒以细粒的超顺磁(SP)和单畴(SD)为主;(2)与徐闻现代砖红壤相比,漳浦砖红壤中的磁性矿物具有更高Fe3+?/?Fe2+比例、赤铁矿相对含量更高、磁性矿物颗粒更粗的特点,表明漳浦砖红壤形成时期气温更高;(3)漳浦砖红壤是古土壤,其形成时期的年均气温较现今高2.5℃以上;当时华南地区热带面积范围扩大,纬度北移4°以上.本研究为全球气候变化提供了土壤学的实证.

Aeolian loess is one of the most widespread deposits on the land and records many kinds of information of paleoclimate changes. Currently, the studies of loess in Pakistan are rare, and the studies on the mechanism of magnetic susceptibility variation are still unavailable. In this study, the the rock magnetic parameters of the newly discovered loess-paleosol section (29 degrees 19'56 '' N, 71 degrees 42'65 '' E) in the Bahawalpur area of the Indus Plain of Pakistan were systematiclly measured. Combined with the grain size characteristics and the diffuse reflectance spectrum (DRS) , the mechanism of magnetic susceptibility variation was discussed. The results show that the main magnetic minerals in loess are magnetite, coupled with goethite and maghemite. And the magnetic domain particles in the magnetic minerals are Pseudo-single domain (PSD) and multi-domain (MD). Compared with the loess, the main magnetic minerals in paleosol are goethite, coupled with magnetite and paramagnetic minerals. This changing mechanism of the susceptibility is different from that of Chinese Loess Plateau (CLP). There is a possible threshold of magnetic susceptibility 12. 8 x 10(8) m(3) . kg(-1) in the study area, above which the main magnetic minerals are strongly magnetic minerals (magnetite and maghemite) ; below this value, the main magnetic minerals are weakly magnetic minerals (such as goethite). This transition of magnetic minerals may lead to a decrease in magnetic susceptibility. This study provides a new clue for further paleoclimatic research in Pakistan based on magnetic susceptibility in the future.

川西高原堆积的黄土—古土壤序列是青藏高原东部地区良好的古气候记录载体,记录了不同时间尺度的古环境变化,对揭示印度季风和高原季风的演化历史及其驱动机制,理解青藏高原隆升效应与周边大气环流之间的关系具有重要意义.相比黄土高原,川西高原黄土环境磁学研究相对薄弱,亟需厘清黄土的磁学性质、磁化率增强机制、成壤过程中磁性矿物的生成、转化机制及其与环境因子之间的响应关系,明确磁学参数的环境意义.本文全面评述了川西黄土环境磁学进展,回顾和总结川西高原黄土的磁性矿物的类型、浓度、粒径等磁学特征及其影响因素和磁学参数的古环境意义,并对存在的问题进行讨论,以期推动青藏高原东部黄土的环境磁学研究及其在古环境和古气候中的应用.

土壤中赤铁矿(α-Fe2O3)和针铁矿(α-FeOOH)的含量和比例对气候变化具有明确的指示意义,对其半定量和定量是古气候研究的重要科学问题.通过选取黄土–古土壤样品以及红壤样品进行加热试验,对比加热前后的漫反射光谱(DRS)峰高,红光段,色度指标红度a、黄度b、b/a参数,分析红壤与黄土中针铁矿和赤铁矿的组成和差异,探讨土壤中针铁矿和赤铁矿的半定量重建,结果表明:黄土样品的DRS一阶导数形态与红壤存在差异;红壤样品的a整体上高于黄土,b差异不明显,a与b具有协同变化的特点;红壤和黄土样品的DRS赤铁矿特征峰峰值与色度指标a密切相关.加热过程中针铁矿特征峰下降,并显示出黏土矿物峰和赤铁矿特征峰整体上升的特征,表明针铁矿脱水并生成赤铁矿.在有氧参与情况下,除针铁矿向赤铁矿转化外,细小颗粒的磁铁矿(Fe3O4)和不稳定磁赤铁矿(γ-Fe2O3)可能是有氧加热后产生赤铁矿的重要贡献者之一.

风成黄土是研究古气候变化的良好载体,在全球陆地分布广泛,而不同区域地理环境差异显著,其记录气候变化的机制亦有所不同.以色列南部黄土区地处亚热带沙漠边缘,为探究该区域黄土磁性特征及其对区域环境的响应机制,对内盖夫沙漠边缘黄土区进行野外考察并测试系统环境磁学及粒度参数.结果表明,Har Keren(HK)剖面中磁性矿物主要为碎屑磁铁矿和磁赤铁矿,磁性矿物含量较少,磁性颗粒主要为粗单畴(SD)和多畴(MD),磁性特征与中国西北干旱区黄土较为相似.HK剖面常温磁学参数整体变化范围较小,仅在剖面亚表层有所升高,可能是受现代成土作用影响.HK剖面中值粒径自底部至顶部呈减小趋势,但粒度整体偏粗,其频率分布曲线显示为正偏态,分选较差,反映出多种搬运方式的混合特征,与典型风成黄土有所差异.

对不同气候条件下发育的土壤/古土壤进行色度分析,探讨其色度参数的空间变化规律及其作为气候变化代用指标的可靠性.结果表明:(1)较小的空间尺度上,土壤色度参数变化复杂,与气候相关关系不显著.土壤色度参数在大空间尺度中均表现出一定的纬向变化,红度(a*)随纬度的增加而降低,黄度(b*)与纬度的拟合曲线趋近于开口向上的抛物线,黄度与红度的比值(b*/a*)随着纬度的增加近似呈线性增加.(2)土壤剖面色度参数均与气候因子(年均降水和年均温)具有一定的相关关系,b*/a*与年均温相关系数最大.色度参数a*与年均降水相关系数稍高于b*/a*,但a*易受其他因素影响;而土壤色度参数b*/a*对土壤颜色的空间变化敏感,是指示气候变化的适用指标.

The formation and transformation of magnetic minerals in soil indicate environmental change. The response mechanism of soil magnetism to environmental factors currently needs to be analyzed quantitatively. In present study, based on related research and field investigations, vertical zonal soil profiles with same parent material from Daiyun Mountain (subtropical area in south of Fujian province) were collected for environmental magnetism and diffuse reflectance spectrum (DRS) analysis. The results showed that magnetite and maghemite dominated the magnetic variation in the soil profiles. Lepidocrocite of secondary origin appeared in the soil at altitude of 1320 m. Given the influence of terrain was excluded, magnetic parameters indicated that SP magnetic domain dominated in the low-altitude soils, while the coarser SD magnetic domain dominated in the high-altitude soils. The results of diffuse reflection spectrum showed that hematite and goethite were sensitive to climate gradient changes in the study area. Hematite proportion decreased with the increase of altitude until completely disappeared at altitude of 1320 m, above which goethite and lepidocrocite became predominate. Semi-quantitative analysis of DRS characteristic peaks of goethite and hematite before and after heating suggested that the threshold of mean annual precipitation and mean annual temperature for hematite in subtropical mountains was likely 1900 mm and 13 degrees C , respectively, while meanwhile goethite and lepidocrocite increased with altitude. This study demonstrated that hematite, goethite and lepidocrocite were sensitive to climatic gradient and thus could be potentially used as important paleoenvironmental proxies in low-latitude regions.

中亚热带的武夷山脉山地土壤具有典型的垂直地带性,对该地的研究有助于弥补当前亚热带地区以及垂直地带性土壤磁学研究的不足.本文以武夷山脉北段为研究区,在不同海拔采集三个土壤剖面样品,进行系统的环境磁学测量,并结合色度指标,探讨武夷山脉不同海拔山地土壤磁学特征差异和环境意义.研究结果表明:(1)三个剖面所含磁性种类大体相同,主要为强磁性的磁铁矿和磁赤铁矿、弱磁性的赤铁矿和针铁矿及顺磁性矿物.不同剖面、同一剖面的不同层位,磁性矿物含量比例不同.(2)随着海拔升高,剖面磁颗粒变粗,这是由于不同气候条件下磁性矿物转化途径不同.(3)降水和气温的配置控制赤铁矿和针铁矿的含量及相对比例,湿冷条件下,针铁矿相对比例更高而使土体呈黄色.(4)亚铁磁性矿物对气候的响应比反铁磁性矿物更为复杂,局部小环境对磁性矿物也产生了较大的影响.色度指标b*/a*(黄度/红度)是具有明确意义的气候代用指标.

通过对川西地区表土样品进行系统的岩石磁学分析,并且结合气候要素探讨表土磁学性质与环境要素之间的关系.结果表明:(1)川西表土在成土过程中生成的细粒超顺磁(SP)和单畴(SD)的亚铁磁性矿物是磁化率增强的主导因素.该地区表土磁性增强机制与黄土高原类似.(2)在空间上,川西高原西部和南部地区的磁性矿物含量要高于东部和北部地区,而成都平原西部地区成土作用最强,磁颗粒细且含有较多高矫顽力磁性矿物.(3)川西表土的磁学参数和气候要素的研究发现年平均降水量(MAP)在600～1000 mm之间磁化率、频率磁化率与MAP呈正相关关系,而磁学参数组合χfd％/HIRM、ARM/HIRM、χARM/SIRM与MAP在这一降雨区间也呈正相关关系,然而这些磁学参数与MAP的相关系数不如黄土高原,可能与研究区复杂的地形、相对湿润的成土条件有关.

Environmental magnetism has been successfully used in the study of paleoenvironment and paleoclimate change. The red soil is widely distributing in Southern China. In this study, we conducted a systematic analysis by environmental magnetism and the color to study magnetic differences and possible causes of subtropical red soil derived from different parent rock weathering crust. Two red soil sections which respectively derived from granite and metamorphic weathering crust locate in Nanping City, Fujian Province. Two sections are about 15 kilometers far away from each other, and have the similar climatic conditions. The results show that: (1) The parent material of the Nanping North Station red soil (NPN) section is a relatively strongly magnetic granite. Due to dissolution of more coarse multi-domain (MD) magnetite to stable single domain (SSD) particles and a small amount of Pseudo-single domain (PSD) magnetite particles during pedogenesis, there is a decrease trend of magnetic susceptibility from bottom to top of the section. In contrast, the Nanfang red soil (NF) section is derived from weakly magnetic metasandstone, with the base of hematite at the transition layer and parent material layer, the magnetic enhancement in the upper part of the section is due to the formation of finer superparamagnetic (SP) magnetic particles during pedogenesis. It indicates that the different parent material is the main reason for the difference in magnetic properties of red soils in subtropical regions. (2) The climatic conditions of the two sections of NPN and NF are basically the same, and the magnetic parameters differences are more obvious than the color indexes. Because of the different parent material of profiles, the relationship between magnetic properties and climate is ambiguous. The ratio of yellowness to redness (b*/a*) is far less than the magnetic differences, suggesting that the ratio of goethite to hematite can more accurately reflect the average climatic conditions in the study area, that is, the secondary magnetic minerals are more suitable climatic indicators of red soil in the subtropical zone.

广泛分布于中国南方的白垩系巨厚地层被认为是河湖相沉积,蕴含着丰富的古气候古环境变化的信息.白垩纪是典型的温室时期,其气候特征可以为当代和未来温室气候研究提供重要借鉴.对位于中国东南的福建省三明市沙县和永安地区的白垩系沙县组典型地层进行了系统的环境磁学参数测量,结合漫反射光谱(DRS)和色度指标,探讨了该地层磁学特征及其环境指示意义和红色的成因.结果表明:1)红色调和黄色调地层的主要磁性矿物分别为赤铁矿和针铁矿,均含有顺磁性矿物和极少量的亚铁磁性矿物;2)相对于粗粒的砂岩,细粒的粉砂岩赤铁矿含量较高;3)红色赤铁矿与黄色针铁矿均形成于成岩阶段之前,具体形成阶段与形成原因需要具体分析;4)红色调地层的赤铁矿指示高温的气候环境;黄色调地层的针铁矿指示局部的湿润环境.磁学参数变化的具体环境指示意义需要进一步研究.

川西高原河谷阶地和断陷盆地广泛分布厚层风成黄土-古土壤序列,目前对其磁学性质变化机制及古气候意义研究还很薄弱.文章对该区理县黄土-古土壤剖面进行了系统的岩石磁学研究,确定了其磁性矿物种类、含量和颗粒大小的特征及其变化规律.通过结合粒度、色度与地球化学参数,进一步探讨了理县黄土-古土壤磁性的主控因素.结果 表明:1)理县剖面同时含有强磁性矿物(为磁铁矿和磁赤铁矿)以及弱磁性矿物(为赤铁矿和针铁矿);2)相对黄土层,古土壤层含有更高比例的亚铁磁性矿物;3)成土过程中生成的大量细小强磁性矿物颗粒,是古土壤层S1磁化率增加的主导因素,该模式与黄土高原相似;4)结合色度以及磁学性质,可以较为明确地区分成壤强度;(5)理县黄土剖面物源复杂,磁学特征受到沉积物来源、后期流水和气候的共同作用,利用单一磁学性质(比如磁化率)进行古气候研究会造成多解性.

南方第四纪红土是记录南方古环境信息的良好载体和第四纪古气候环境研究的重要内容.本文对采自福建北部闽江流域大横第四纪红土剖面的样品进行磁化率、等温剩磁、饱和等温剩磁和代表样品的κ-T曲线等多磁学参数的详细测量和分析,研究结果表明:大横剖面的磁化率范围为8.87～35×10-8m3·kg-1,饱和等温剩磁范围为51.77×10-5 ～294.51×10-5Am2·kg-1,总体偏低,说明大横剖面的磁性矿物含量较低,可能是福建北部化学风化作用强烈且温暖湿润的环境导致的;频率磁化率、非磁滞磁化率及XARM/SIRM比值说明剖面自上而下,磁性矿物颗粒大小总体上呈现变粗趋势,由SP+ SD颗粒到SD+ MD颗粒的转变,剖面磁性矿物以磁铁矿为主,并含有磁赤铁矿、赤铁矿和纤铁矿等.本文探讨了红土剖面的不同沉积层磁学特征变化及对环境的指示意义,对认识该地区第四纪红土的风化特征及发育环境有一定借鉴意义.

澳大利亚维多利亚州南部海岸坎贝尔港(Port Campbell)附近的十二门徒(The Twelve Apostles)地层主要为石灰质地层,偶见海相生物贝壳,一直被认为是浅海大陆架石灰岩(limestone)沉积.野外考察发现,该地层不仅存在海相生物碎片,同时也存在根化石、钙结核层等地表古土壤特征.为了更好地分析其沉积环境,本文对十二门徒剖面样品的粒度、石英颗粒表面形态以及稀土元素进行了系统分析,并将其结果与第四纪西峰黄土古土壤和现代海滩砂进行比较.结果表明,整个剖面序列以细粉砂为主,与典型风积黄土古土壤具有相似的粒度分布与粒度象特征,Sahu判别分析结果表明绝大部分样品值都小于-2.7411,显示了剖面整体以风积成因为主.样品的石英颗粒呈现出不规则的棱角状、次棱角状,显示风成特征;此外,十二门徒剖面样品具有与黄土古土壤以及上地壳(UCC)相似的稀土元素分配模式.因此,我们认为该地层并非海相石灰岩沉积,而是一套在半干旱气候条件下发育的具有多层钙结核的风积序列地层.该地层记录了澳洲东南海岸16.0～5.3Ma以来的风积历史与气候变化,表明澳大利亚的干旱化至少是在16Ma前就开始了.由于这套风积地层靠近海岸,易受地质时期海平面变化的影响,以致在地层中的局部层位出现海相生物碎屑,但地层的物质来源可能来源于澳大利亚的艾尔湖(Lake Eyre)盆地.

印度中西部德干高原是由白垩纪末期65Ma以前多次喷发的玄武岩形成的高原.喷发间歇期间玄武岩遭受风化,形成了多层玄武岩风化红层.德干高原就是由这样一层层的溢流喷发玄武岩和风化红层相间而成,厚度达千米以上.在德干高原和南方各地的顶部普遍发育着砖红壤,该砖红壤在德干高原发育约25m厚,被认为是从玄武岩母质基础上原地风化形成,但是实地观察发现,砖红壤与玄武岩风化红土在结构、构造以及物质组成等方面均存在明显差别.常见的玄武岩喷发间歇发育的风化层厚2～ 3m,存在从上到下风化程度由强到弱,最后过渡到玄武岩母岩的明显层次与颜色的变化.但是德干高原玄武岩之上的25m厚砖红壤缺乏这种渐变特征,而且平坦的砖红壤顶部洼地中还发现了风积黄土层.对德干高原砖红壤、玄武岩以及玄武岩风化红土层分别采样,测量其全样粒度和磁化率、饱和磁化强度、饱和等温剩磁、非磁滞剩磁等常温磁学参数,挑选代表性样品进行磁滞回线和热磁分析.实验结果表明:1)砖红壤样品主要的磁性矿物是赤铁矿,有些同时还含微量磁赤铁矿,粒径相对较粗的玄武岩风化红土层的主要磁性矿物是磁铁矿和磁赤铁矿;2)玄武岩只含磁铁矿,并无磁赤铁矿或者赤铁矿.因此,不论是玄武岩风化红土,还是砖红壤,它们所含的磁赤铁矿以及赤铁矿都是在风化成土过程中形成的.砖红壤以赤铁矿为主和少量针铁矿,偶有样品含微量磁赤铁矿,说明该磁赤铁矿可能是母岩中的磁铁矿风化为赤铁矿的中间产物;3)玄武岩风化红土层与砖红壤不仅在磁性矿物特征方面存在差别,而且在全样粒度组成方面也存在明显差别,前者以＞ 100μm为主,而后者以＜100μm为主.此外,25m厚层状砖红壤除了缺乏由上而下风化程度由强变弱的差异与层次的特征之外,也缺乏砖红壤中残留的玄武岩碎屑,难以支持巨厚砖红壤由顶层玄武岩就地风化形成的说法.砖红壤厚层均匀特征似乎需要自下而上形成过程,即不断加入物质不断地风化成土才能够形成均匀厚层砖红壤.目前刚刚发现了德干高原黄土堆积,其西北方向分布着印度沙漠,每年都有沙尘暴发生,向德干高原提供着物质来源.因此,砖红壤由风积物加积形成或许是要考虑的重要可能性之一.