江西九江泰和第四纪红土成因的比较研究

通过对江西九江和泰和第四纪红土的形成环境、粒度组成、稀土元素地球化学特性和石英微形态特征的研究，探讨两地第四纪红土的成因。结果表明：地处红黄土交接带的九江地区的第四纪红土，具有与下蜀黄土相似的风成特性，系风积成因；而位于吉泰古盆地的泰和地区的第四纪红土，具明显的冲积相特征，应为河流冲积成因。     

安徽郎溪黄棕色土—红土二元结构土壤剖面的成因与长江流域第四纪晚期古气候演变

安徽宣郎广一带,黄棕色土-红土二元结构地貌十分常见。本文在郎溪选择了一个典型的黄棕色土-红土剖面,进行粒度组成和元素地球化学性状的研究,结果表明:(1)研究剖面上部黄棕色土的粒度组成和元素地球化学特征,与宣城、九江黄棕色土和镇江下蜀黄土十分一致,说明研究区域的黄棕色土确实与长江流域广泛分布的下蜀黄土同源。郎溪剖面粒度和元素地球化学特征的变化较均匀,尤其黄棕色土→埋藏红土(包括均质红土和网纹红土)间呈连续过渡,无沉积间断,表明埋藏红土的物源与黄棕色土和下蜀黄土相似,具典型的风积成因特性。(2)与黄棕色土相比,埋藏红土粒径偏细,风化成土作用显著增强。从埋藏红土逐渐过渡到黄棕色土,反映的可能是长江流域晚更新世初期,末次间冰期结束、末次冰期开始时的一次重大的古气候演变事件,但仍需确凿的年代学证据。     

昆山绰墩古土壤粒度特征及母质判别

自第四纪晚期以来,来自黄土高原的粉尘在风力作用下不断向东南扩张,在长江中下游地区形成了下蜀黄土。太湖流域的部分水稻土就是在下蜀黄土之上发育的。本文对绰墩古土壤的粒度组成特征进行了系统的研究。结果表明,绰墩古土壤<5μm粘粒、5~10μm细粉砂和10~50μm粗粉砂组分平均含量分别为22.89%、22.96%和63.52%,其中10~50μm粗粉砂组分为众数粒组。>50μm砂粒平均含量仅为5.10%。绰墩古土壤粒度组成与镇江下蜀黄土粒度组成具高度相关性(r=0.97)。根据粒度分析,我们初步认定绰墩古土壤母质为下蜀黄土。     

下蜀黄土中记录的氧同位素3阶段(MIS3)特殊暖湿现象

下蜀黄土在第四纪古气候研究上具有独有的区位特征,对南京李家岗下蜀黄土剖面上部的近20m进行野外观察和室内研究,划分出5层黄土和5层古土壤,按5cm间距采集了Rb/Sr、色度、磁化率和粒度样品,并在剖面和可追索的相邻剖面上采集了12个光释光测年样品。通过气候代用指标与深海氧同位素及古里雅冰芯、马兰黄土等的对比,结合光释光测年,对南京李家岗下蜀黄土进行气候地层划分,对比结果将下蜀黄土划分出分别相当于MIS2～MIS5的4个气候旋回。气候意义的分析表明,各代用指标具有良好的可对比性,显示了氧同位素3阶段明显的特殊暖湿特征,并且其所反映的气候变化过程和强度与青藏高原及西部黄土具有明显的差异。     

亚热带加积型红土稀土元素特征及物质来源

亚热带红土沉积物物源并不像北方黄土研究那么深入,其成因、来源等一直存在争论,不同类型的沉积物有着不同的物源说。通过分析对亚热带沉积物的稀土元素含量、特征值、配分模式分析,得出:亚热带不同区域的加积型红土,其物质来源不同;加积红土层有明显的分异,同一剖面中的不同沉积层,其沉积环境可能发生了变化;均质红土部分上与北方黄土特征相似,网纹红土在某种程度上也与黄土接近,推测可能均与北方黄土存在一定的物质联系,是北方风尘、地区河湖沉积以及风化壳的高度混合体,其混合程度不同;黄棕色土与下蜀黄土表现出较一致的特征,相对于北方黄土,他们更加接近长江河漫滩沉积物,长江漫滩堆积物可能主导了其物质来源,而黄土对其的影响相对较小。长江河漫滩沉积可能对位于长江河谷附近的第四纪加积红土有较为重要的影响,而随着距离河谷距离的增加,北方风尘和区域各类沉积对物源的贡献增大。     

中国中亚热带网纹红土的地球化学特征与沉积环境

130个样品的粒度、黏土矿物组成、地球化学特征以及Sr、Nd同位素分析表明,广泛分布在中亚热带地区并且具有一定厚度的第四纪网纹红土为加积型沉积。该类沉积粒度组成与北方风尘沉积类似,粉砂含量占优势,>50μm含量小于5%,5~50μm组分41.2%~61.5%,<5μm黏粒26.9%~55.8%;黏土矿物组成中含有较多的石英、云母和高岭石;全土体的平均硅铝率为7.96,硅铁铝率6.11;稀土元素丰度179.6 mg kg-1,与地壳平均值(178 mg kg-1)、北京郊区1998年12月大气粉尘稀土总量(178.0 mg kg-1)以及两块中国黄土标样(178.2mg kg-1)非常接近,并且表现为轻稀土强烈富集,重稀土淋失,Ce元素正异常;网纹红土全岩样品的87Sr/86Sr值界于0.725 657~0.727 714之间,Nd同位素0.511 989~0.512 098,与佳县上新世红黏土和黄土的酸不溶相性物质接近。理化特征指示,第四纪加积型网纹红土与北方黄土中的古土壤以及上新世红黏土的形成环境类似,并且具有稳定的物质来源。     

皖南第四纪红土锆石形态特征及物源指示意义

对皖南铜陵、宣城两地典型第四纪红土剖面锆石的形态特征分析结果发现,铜陵、宣城两地:剖面自下而上,由以近距离搬运为代表的棱角、次棱角状锆石为主,向远距离搬运的次圆状、圆状锆石占比不断提高的近远源混合物源组成模式转变;锆石长宽值随深度发生变化,不同深度的锆石长宽比值离散程度差异较大,说明了红土物源发生了改变;不同深度,锆石的晶体形态组成也存在差异。结合前人研究成果,可以认为长江及其支流的河漫滩沉积物是红土的重要物质来源。随着全球气候变冷和冬季风加强,远源粉尘堆积对该区域的影响逐渐加大。红土剖面上部的锆石形态显示出远距离搬运特征,而剖面下部则具有近距离搬运特征。基于两剖面不同深度锆石形态特征的定量化分析结果,锆石形态特征对第四纪红土物源具有一定的指示意义。     

环洞庭湖区两种典型红土理化特性比较研究

通过环洞庭湖区两种典型成因红土的野外勘察与取样、室内磁化率、粒度、微量元素(Li、Rb、Sr、Ba)分析,进行两种不同成因的红土理化性质的比较。研究结果表明,风成成因的红土粒度比基岩风化成因红土明显较细,风成成因红土以粉砂为主,基岩风化型红土为砂和粉砂为主;两种成因红土受到长江中游地区高温高湿的气候条件影响,磁化率均显示为低值,明显低于黄土高原黄土和长江下游下蜀黄土;微量元素Li/Ba、Rb/Sr比值显示为高值,显著高于黄土高原黄土和长江中下游地区下蜀黄土,表明两种红土均经历了强烈的风化淋溶过程,但基岩风化型红土的风化成壤强于风成成因红土,可能基岩风化型红土经历了更长的风化成壤过程。     

第四纪黄土剖面多元古土壤形成发育信息的揭示

以时间尺度 2 0万年以来的洛川黄土剖面为研究对象。采用间隔 30～ 5 0cm的密集采样 ,通过土样的物理、化学、矿物组成和孢粉分析及土壤微形态镜鉴的综合研究 ,对第四纪生物气候环境演变提出了新的见解。对原以代表干冷环境沉积为主的黄土地层 (L) ,揭示了内伏半干旱环境的演化及相应的土壤发育过程 ;对原以代表暖湿环境的红褐色古土壤层 ,揭示了内伏干旱、半干旱环境的演化及干旱与湿润型孢粉共存的矛盾实质。研究证示 :深厚的黄土剖面是在第四纪生物—气候环境演变过程中 ,通过黄土沉积、成壤强弱交替演化 ,形成发育的由不同土壤类型组成的特殊的多元古土壤剖面体系。     

周原全新世复合古土壤和成壤环境的微形态学研究

通过对陕西周原黄土剖面的微形态研究 ,结合微量元素、粒度及磁化率分析 ,探讨了黄土风化成壤的特征 ;揭示出该剖面的全新世古土壤S0 是温暖湿润的环境下形成的具有强烈粘化特征的复合土壤 ,是 60 0 0～ 5 0 0 0aB .P .出现的区域性干旱气候事件造成风尘加速堆积的结果。关中盆地在 85 0 0～60 0 0aB .P .风化成壤最为强烈 ,气候最为暖湿。在 5 0 0 0～ 3 1 0 0aB .P .又出现了一个比较强烈的成壤时期。而最近 3 1 0 0年以来是一个风尘堆积较强的相对干旱期。     

皖南网纹红土的剖面风化特征及其古气候意义

气候变化下土壤物质过程的响应特征是全球变化研究的重要主题。选取安徽宣城剖面,通过元素分析,对其风化强度特征进行了研究。结合与黄土高原第四纪黄土、古土壤、江苏镇江下蜀土以及江西九江红土等典型风成堆积剖面的对比分析,得出以下结论:(1)宣城红土剖面经历了高强度的化学风化作用,长石损失殆尽,进一步的风化作用已导致其含K矿物(黑云母、伊利石和钾长石)的分解,次生粘土矿物以高岭石为主。此外,宣城红土与其他剖面相比,显著强于镇江下蜀土,远强于洛川黄土与古土壤,而与九江红土的风化程度较为相近。(2)在地形、母岩等条件相似的情况下,气候(特别是温度和降水量)是控制化学风化程度的主要因素,并且与温度相比降水因素可能起着更为重要的制约作用。(3)在地质历史时期,宣城→镇江→洛川,随着地域的北移,气候环境向干冷方向发展。(4)BA,Na/K和硅铁铝率的剖面变化特征揭示,中更新世早、中期,气候相对温暖潮湿,之后气候总体恶化,向干冷方向发展。但在此过程中,伴随着大姑-庐山间冰期和末次间冰期的到来气候又出现过两次短暂的回暖过程,并且在晚更新世早期呈现兼有干湿交替的特征。     

Yellow‐brown earth on Quaternary red clay in Langxi County,Anhui Province in subtropical China: Evidence for paleoclimatic change in late Quaternary period

In order to investigate the paleoclimatic changes in S China during the late Quaternary and their influence on pedogenesis and soil classification, a yellow‐brown earth (YBE)–red clay (RC) profile in Langxi County, Anhui Province was studied. The grain‐size distribution and the major‐ and trace‐element compositions of the profile indicate that the YBE of the profile shares the same origin with the YBE in Jiujiang and Xuancheng and the Xiashu loess in Zhenjiang, and the underlying RC also has aeolian characteristics and shares the same origin with the Xiashu loess. Grain‐size characteristics, molecular ratios of SiO₂/Al₂O₃, SiO₂/(Al₂O₃+Fe₂O₃), and BA ([CaO+MgO+K₂O+Na₂O]/Al₂O₃) and other weathering indices (CaO/TiO₂, MgO/TiO₂, K₂O/TiO₂, Na₂O/TiO₂, and Rb/Sr) of the profile indicate that the RC is more strongly weathered than the YBE. Magnetic susceptibility (χ_lf) of the uniform red clay (URC) of the profile is significantly enhanced. However, that of the underlying reticulate red clay (RRC) is significantly decreased because of the paleogroundwater movement and cannot indicate its strong weathering properties. The YBE‐RC profile in Langxi County recorded a great climatic change during late Quaternary: At that time, the pedogenic development of the RC was terminated and widespread dust deposition occurred. The parent material of the RC may be aeolian deposits which were accumulated before the last interglacial and were strongly weathered and rubified under the subsequent interglacial climate. It is observed that red soils, derived from the RC, and yellow‐brown soils, derived from the YBE, coexist in the study area, which is contradictive to the theory of the zonal distribution of soils. Therefore, it is necessary to take into account the history of Quaternary climatic changes when studying pedogenesis.     

江西九江地区第四纪红粘土上的“黄帽子”

A thin layer of yellow-brown-colored earth was generally found on Quaternary red clay in Jiujiang, Jiangxi Province. A typical profile was established. Both particle size distribution and REE (rare earth elements) characteristics of the yellow-brown-colored earth of the profile fully suggested its aeolian origin and close similarity to Nanjing Xiashu loess. The study also implied aeolian origin of the underlying Quaternary red clay. Compared with the red clay, the yellow-brown-colored earth was less weathered because of its lower content of free iron and higher mole ratios of SiO₂/Al₂O₃ and SiO₂/(Fe₂O₃+Al₂O₃) as well as its less developed chemical microtextures of quartz grains. In order to study the ages of the two deposits comparatively, the thermoluminescent dating method was used. As a result, the bottom of the yellow-brown-colored earth was dated to 60±5 ka B. P. and the upper part of the red clay 388±54 ka B. P. It was suggested that the yellow-brown-colored earth was formed in the Late Pleistocene and was probably the aeolian deposit of the Last Glacial, which corresponded with the Malan loess in the Loess Plateau of the northwestern part of China; while the underlying red clay was formed in the Middle Pleistocene. A "yellow cap" on Quaternary red clay in Jiujiang implied a great climatic and environmental variation in the beginning of the Late Pleistocene in the southern part of China, especially in the middle and lower reaches of the Yangtze River. The event not only halted the rubification, once dominating the region, but also produced a widespread covering of aeolian deposit, as only occurred in the cold and dry environment.     

安徽省南部第四纪红色粘土的成因

The particle-size distribution,heavy mineral constituents and rare earth elements(REE) characteristics of the Quaternary red clay of southern Anhui Province were studied to explore the origin of the clay.The results showed that the clay had some properties of areolian deposits,which could be compared with,those of the loess in North China ;and its chondrite-normalized curves of REE were similar to those of the Xiashu loess implying tha they shared the same orighin.It was concluded in combination with the results rported by other researchers that the Quaternary red clay of southern Anhui Province originated from aolian deposts, and this could reveal the cycles of warm and cold climates in the area during the Quaternary period.     

中国南方金衢盆地红土多元成因的粒度证据

Six typical red clay profiles were sampled from Tangxi (TX),Langyaz (LYZ),South Shangshanwen (SSW),Xianqiao (XQ),Qijian (QJ) and Huhaitang (HHT) of Jinhua-Quzhou Basin,Zhejiang Province of China to evaluate the characteristics of grain size composition,distribution and parameters of red clays and to reveal the origin of red clays and interpret possible implications for paleoclimate in subtropical China.The results showed that red clays in TX,LYZ and SSW were fine and uniform,with no>2mm gravels and little>63μm fraction.They had a high content of 10–50μm fraction,so-called"basic dust fraction",and showed unimodal distributions,which were very comparable to those of the Xiashu Loess in southeastern China and the loess in North China.All these features reflected marked aeolian characteristics of the red clays in these areas.Red clays in XQ and QJ were much coarser than those in TX,LYZ and SSW,with high contents of >63μm fraction and even containing>2 mm gravels in some layers.The grain size distribution patterns showed significantly progressive trends from the lower profile to the upmost layer and could not be compared with those of the loess in North China or the Xiashu Loess,implying they might be derived from underlying parent rocks and had some inherited properties from bedrock.Red clays in HHT had high contents of>63μm fraction and contain many >2mm gravels in each layer.The grain size frequency curves showed multiple-peaks and some abrupt variations were also observed on the profile,revealing its alluvial or diluvial origin in HHT.The multiple origins of red clays reflected the diversity and complexity of the Quaternary environment in South China.It can be concluded that grain size is an efective proxy indicator for the origin of most deposits.     

母质对新形成腐殖质的影响

本文研究了在旱地和水田条件下,母质对新形成腐殖质的影响.供试物料为紫云英、绿萍、稻草和水葫芦.结果表明:1.除绿萍外,各物料腐解三年后均已分解较完全.腐解产物的C/有机N值和腐殖质组成均随原始物料而异.2.当植物物料和母质相同时,与水田条件下的相比,旱地条件下的腐解产物的C/有机N值大多较窄,中性糖量较高,六碳糖/五碳糖值较宽,腐殖酸的提取率较高.3.当水分条件和植物物料相同时,与第四纪红色粘土中的相比,下蜀黄土中腐解产物的胡敏酸的C/N值大多较窄,六碳糖/五碳糖值和胡敏酸/富里酸值大多较宽.作者认为,二者中腐殖质组成的差别在一定程度上系由于粘土矿物的组成不同所致.     

安徽宣州黄棕色土和第四纪红土的比较研究及其古气候意义

通过地貌和型面的考察和研究,发现安徽宣州地黄棕色土的层序位于第四纪红土层之上。用ＥＳＲ测年法测得黄棕色土年龄约为８０ｋａＢ．Ｐ．,红土年龄 ２４０ｋａＢ．Ｐ．,。对这两种成土母质的各项理化性状和磁化率指标进行比较研究,发现黄棕色土受风化作用的程度不如第四纪红土。     

南方典型红壤区旱地与水田土壤酸度的剖面差异性

为探明红壤区不同耕地利用类型下土壤酸度的剖面变化特征及其主要影响因素,选取江西省余江县和湖南省祁阳县的典型水田、旱地两种耕地利用类型下、第四纪红色黏土母质发育的红壤,分5层(0～20、20～40、40～60、60～80和80～100 cm)测定土壤pH、交换性铝、交换态盐基阳离子及有机质含量等指标,分析剖面酸度特征及其相互关系。结果表明：土壤pH均随土层深度的增加呈增加趋势,不同耕地利用类型下以水田剖面p H较高,范围为5.80～6.43,旱地剖面p H较低,范围为4.68～5.41。土壤交换性铝含量以水田含量较低,范围为0.16～1.56 cmol/kg,旱地的含量较高,范围为4.22～7.02 cmol/kg,水田的交换性铝含量随土层深度的增加呈降低趋势,旱地则呈现相反的变化趋势。0～20 cm土层的交换性铝与有机质含量呈显著负相关,40～100 cm土层的交换性铝与交换态盐基阳离子含量呈显著负相关。耕地利用类型是影响土壤酸度的主要因素之一,旱地土壤酸度强于水田。增加耕层土壤有机质含量可能是减缓酸化、降低交换性铝含量的策略之一。