ISWC OpenIR  > 水保所知识产出(1956---)
黄土剖面粘粒矿物的组成特征及其环境意义
黄传琴
Subtype博士
Thesis Advisor谭文峰, 邵明安
2011-11
Degree Grantor中国科学院研究生院
Place of Conferral北京
Keyword土壤 黄土-古土壤 矿物风化 成壤环境 土壤发育
Abstract

黄土高原完整的黄土-古土壤序列作为第四纪古环境三大支柱记录之一,储存了
2.5 Ma B.P.以来丰厚的地学-生物学信息,它记录了黄土高原乃至整个欧亚大陆第四
纪多旋回的生物气候环境变迁,为研究古气候和古环境变化提供了很好的研究材料。
粘粒矿物作为土壤的重要组成成分,它的形成与转化受温度、湿度等环境条件的影响。
因此,矿物组成特征可指示土壤演化过程与成壤环境。本研究以武功、洛川、安塞全
新世黄土-古土壤以及武功第五层古土壤为研究对象,采用X-射线衍射(X-ray
diffraction)、X-射线荧光光谱法(X-ray fluorescence)、选择性溶提等技术研究了不同
土壤层次的矿物学特征,结合14C 加速器质谱法测年、粒度组成、CaCO3 以及磁化率
分析,探讨全新世黄土-古土壤和第五层古土壤中的矿物风化与成壤过程,揭示地质
时期古气候与成壤环境的时空特征,取得的主要结果有:
1.武功全新世黄土剖面的土层(上覆黄土层/L0,0-50 cm;均一古土壤层/S0,50-150
cm;古土壤与马兰黄土层之间的过渡黄土层/ LT,,150-200 cm)明显可辨。根据14C
测年结果进行插值计算,L0、S0、LT 土层的更迭说明了黄土高原南缘全新世0-3,100 yr
B.P.、3,100-8,500yr B.P.、8,500-11,500 yr B.P.期间气候干冷-暖湿-干冷变化的“三阶
段”模式。武功全新世黄土-古土壤剖面的CaCO3 含量、粒度组成、磁化率均与成壤
作用呈相应的周期变化。相对下伏马兰黄土层(L1,200 cm 以下)及上覆黄土层(L0),
全新世古土壤(S0)CaCO3 的强烈淋溶、粘粒的富集、磁化率的增强,说明该层土
壤的成壤发育作用增强。根据武功全新世古土壤层CaCO3 的淋溶量、迁移深度及磁
化率推算,全新世中期S0 发育时的年均降水量高达800 mm 以上。该区全新世中期气
候类型相当于现今亚热带北缘(秦岭南坡)土壤发育的气候条件。
2.黄土高原南缘武功全新世黄土粘土矿物的组成特征分析结果表明,全剖面粘土
矿物组成相似,以伊利石为主,绿泥石、蛭石次之,含有少量高岭石与蒙脱石等。古
土壤S0 中存在少量的层间羟基物矿物(hydroxy-interlayered minerals,HIM),这意味
着全新世中期黄土高原南缘以森林为主的古土壤环境。柠檬酸钠溶液80ºC 连续处理
结果HIM 主要由层间羟基物蒙脱石(hydroxy-interlayered smectite,HIS)和层间羟基物蛭石(hydroxy-interlayered vermiculite,HIV)组成,并提出了古土壤中硅酸盐矿物
的形成与转化过程及HIM 形成的可能途径。
3.黄土高原南缘武功全新世古土壤层(S0)中的伊利石结构特征指数相对较高,
但全剖面(L0、S0、L1)伊利石的半高宽(half height width,HHW)、积分宽度(integral
breadth,IB)、化学指数(illite chemistry index, ICI)分别在0.25-0.30 º Δ2θ、0.4-0.6 º Δ2θ、
0.25-0.40 之间变化,表明土壤形成于物理风化较强的环境中,矿物化学风化较弱。富
含CaCO3 的风尘物质的连续沉积抑制了矿物的风化演化,减弱了古土壤的成壤发育
强度,主要的矿物风化过程是伊利石的脱钾作用和绿泥石的风化。因此,黄土高原地
质时期的古气候及成壤环境条件,比黄土-古土壤层中的矿物风化及成壤特征所反映
的气候更为暖湿。
4.黄土高原自北向南的安塞、洛川和武功全新世黄土-古土壤(14C 测年:23860
± 90-0 yr B.P./晚更新世晚期至今)剖面中的层状硅酸盐矿物以伊利石为主,绿泥石、
蛭石次之,含有少量高岭石与蒙脱石等,其矿物及元素组成相似,并且各剖面之间
的矿物与元素组成也相似。沿气候梯度,自北(安塞剖面)向南(武功剖面),古土
壤层中蛭石含量逐渐增加、高岭石和蒙脱石略有减少,同时伴有粘粒的富集、碳酸
盐强烈的淋溶以及磁化率的增强。安塞全新世剖面的层状硅酸盐粘土矿物组成一致
且含量稳定,与剖面中高砂粒含量、稳定的CaCO3 含量以及极低的磁化率一致,风
尘沉积后经历的矿物风化、成壤作用弱,这说明黄土高原北部11,500 yr B.P.以来气
候及成壤环境稳定,全新世中期并没有受到东南亚暖湿季风气候的影响。黄土高原
黄土-古土壤中的矿物学组成特征确切地记录了地质时期成壤环境的时空变化。黄土
高原全新世期间的气候变化存在地区差异,典型的全新世气候变化的“三阶段”模
式在区域上并不具有普适性。
5.黄土高原南缘武功第五层复合古土壤(S5)每一层古土壤层(S5-1、S5-2、S5-3)
的CaCO3 在成壤前期完全淋失,在古土壤底部形成了30-50 cm 厚的CaCO3 结核层。
S5-1 土层中的粘粒含量和磁化率均明显高于S5-2 和S5-3 土层,说明S5-1 土层经历了更为
强烈的物理、生物化学风化,其成土作用较S5-2 和S5-3 土层的强烈。S5 的粘粒/粉粒比
值较高,小于0.002 mm 的粘粒含量高出下伏黄土层(L6)约60-100 %。粒度结果表
明,S5 的粘化作用较全新世古土壤(S0)的强。各古土壤层中部磁化率在120-310 SI
(10-8 m3 kg-1)范围内波动,远比S0 的磁化率(190-220 SI/10-8 m3 kg-1)高。可以推
断S5 古土壤代表了比全新世中期更为暖湿的气候条件。武功S5 复合古土壤成壤过程
中CaCO3 完全淋失、粘化作用强烈、磁化率增强,都说明S5 在暖湿的气候条件下经历了强烈的成壤作用。
但是,粘土矿物的分析表明,S5 的粘粒矿物组成相似,S5-1、S5-2 和S5-3 的粘土矿
物均以伊利石为主,并含有不同数量的绿泥石、蛭石、高岭石与蒙脱石等。S5 并没有
表现出比其上覆黄土层(L5)和下伏黄土层(L6)更为强烈的矿物风化,这与粒度组
成、CaCO3 及磁化率的分析结果矛盾。这可能是因为每层复合古土壤层底部坚硬、致
密的CaCO3 淀积层和粘化层对下渗水的滞留作用,阻碍了上伏土层中碱土金属元素和
硅的淋移,抑制了矿物的风化转化。
关键词:土壤;黄土-古土壤;矿物风化;成壤环境;土壤发育

Other Abstract

The complete set of “loess-paleosol” sequences on the Loess Plateau, China, as one of
the three records for paleoenvirenment during the Quaternary period, record the biologic,
climatic and environmental changes of the Loess Plateau, even of the Eurasian since 2.5
Ma B.P.. Soils derived from the Loess Plateau of China are regionally important and
expression of the soil properties along the soil profile may be directly related to climate
changes. Clay minerals are derived from weathering of parent material and/or precipitated
from the soil solution. They reflect successive stages of mineralogical evolution depending
on the various environmental conditions that have prevailed during soil formation.
Therefore, this study focused on the mineralogy in the Holocene loess-paleosol in the
Wugong, Luochuan and Ansai sections and the fifth paleosol (S5) in the Wugong section,
together with the specific properties (e.g. grain size, carbonate content and magnetic
susceptibility)、14C dating by the accelerator mass spectrometry method (AMS) and field
observations to access the clay mineral transformation, in relation to the pedogenesis and
the regional climate changes. The main results are as follows:
1) The main stratigraphic subdivisions of the Holocene loess-paleosol in the Wugong
section clearly identified in the field were confirmed by analytical data with single-welded
paleosol S0 (8,500-3,100 year B.P.) and a cover loess L0 (3,100–0 year B.P.) and a
transitional loess (LT) (11,500–8,500 year B.P.). They presented a pretty classic picture as
a complete episode of the Holocene climate change, corresponding to a glacial-interglacial
climatic fluctuation on the southernmost Loess Plateau. The intensive decalcification,
enrichment of clay content and increasing of magnetic susceptibility in the paleosol (S0,
50-150 cm) signified the strong pedogenesis with respect to the Malan loess. The
calculated from the magnetic susceptibility and the depth and the total amount of carbonate
leaching suggested that the average annual precipitation during the mid-Holocene was up  to 800 mm. And the climate type in this period was analogous with the modern climate
conditions in the northern subtropical zone (the southern slope of Qingling Mountains) for
the formation of Udic Luvisols (Brown Soil).
2) Mineralogy of the Holocene loess-paleosol in the Wugong section on the
southernmost Loess Plateau suggested that clay mineralogical compositions were similar in
the stratums with the illite in the majority throughout the profile. The changes of the
phyllosilicate minerals were consistent with the soil genetic horizons and with the
variations in CaCO3 content, particle size distribution, and magnetic susceptibility. A
relatively high vermiculite content and the presence of hydroxyl-interlayered mineral (HIM)
occurred in the most weathered palaeosol (S0). According to the XRD analysis before and
after sodium citrate extraction, the HIM in the paleosol was mainly composed of the
hydroxy-interlayered smectite (HIS) and the hydroxy-interlayered vermiculite (HIV). The
hydroxyl-interlayers common present in Alfisol of southern China, occurred in the paleosol
signified the dominant forest landscape palaeoecology and the acidic paleosol environment
during the mid-Holocene. The contradiction between the type clay minerals present and the
measured alkaline soil pH values in the palaeosol could be understood by the
recalcification caused by the post-pedogenic leaching from the overlying loess. A most
likely explanation for the occurrence of HIM and transformation of phyllosilicate minerals
in the paleosol stratum derived from loess was suggested.
3) The relatively high values of half height width (HHW) and integral breath (IB) and
the relatively low values of chemical index of illite (ICI) represent relatively low illite
crystallinity and intensive weathering and pedogenesis in the Holocene paleosol (S0) with
respect to the overlying and underlying loess. However, the values of HHW, IB and ICI
showed no significant variations throughout the profile ranging from 0.25 to 0.30 (ºΔ2θ),
0.4 to 0.6 (ºΔ2θ) and 0.25 to 0.40 (º Δ2θ) throughout the profile, respectively, which
implied a weak chemical weathering. The successive adding of eolian sediments with
abundant CaCO3 restrained the intensity of mineral weathering and pedogennesis.
Generally, the depotassication of illite and the degradation of chlorite were the major
mineral transformation processes that occurred with soil-formation of the Holocene
palaeosol on the southernmost Loess Plateau and the pedogenic strength did not reached
the level of Udic Luvisols (Brown Soil). Due to the special pedogenesis pattern, the  palaeoclimate would be warmer and wetter than the climate that was derived from the
mineral weathering and soil evolution characteristics in paleosol.
4) Analysis of the Holocene loess-paleosol at Ansai, Luochuan and Wugong in a
north-south transect and in geological age from the late Epipleistocene (0-23860 ± 90 year
B.P.) suggested that the mineralogy were similar over the Loess Plateau, China. However,
in detail, there were significant temporal and spatial variations in analytical results of
pedogenesis and mineralogy of the profiles in the three sections along the climate gradient.
Mineral weathering and pedogenesis resulted in a vital increase of vermiculite in paleosol
of Wugong section with more clayey, intensive decalcification and increasing of magnetic
susceptibility. The subtle decrease of kaolinite and smectite in paleosol southward resulted
from the resilication by strong plant/clay interaction and leaching of soil base ions with
lush vegetation and increasing precipitation during the mid-Holocene. The pedogenetic
cyclicity and mineral weathering were progressively weakened with the trending
south-north across the Loess Plateau signified the weaker climate fluctuation since 11,500
years and the decreased influence of summer monsoon on pedogenesis and mineral
weathering intensity northward. In general Holocene loess in Ansai section preserved in
thick eolian deposits was found to be relatively homogeneous as far as grain size and clay
mineralogy. There was no significantly variation in phyllosilicate composition with depth
which coincided with more coarse grains and constant CaCO3 content signified the least
weathering and pedogenesis under stable and dry climate and pedogenic environment over
the last 11,500 years. The mineralogical composition in loess-paleosol across the CLP
records precise temporal and spatial variability of the palaeoenvironment. The traditional
scheme of the Holocene climatic change is not a unique phenomenon across the Loess
Plateau.
5) The fifth paleosol (S5) is a complex paleosol essentially composed of three
well-developed reddish soil pedons (S5-1, S5-2, S5-3). The carbonate of each paleosol pedons
was absolutely leached from the paleosol during the early stage of soil formation under
intensive eluviation condition, and deposited beneath the pedons of 30-50 cm in thickness
which can easily be recognized as stratigraphic markers between each pedons. The clay
content and magnetic susceptibility in the S5-1 pedon were absolutely higher than those in
the S5-2 and S5-3 pedons which signified more intensive physical and biochemical  weathering and pedogenesis in the S5-1 with respect to the S5-2 and S5-3 pedons. The clay/silt
ratio was higher in the S5 than those in the overlying and underlying loess (L5 and L6) and
clay content in the S5 was 60-100 % higher than those in the L5 and L6. Particle size
distribution illustrated that the intensified clayification in situ after deposition in the S5
than that in the Holocene paleosol (S0). It was possible that the S5 with clay content higher
than that in yellow-brown earth is belong to the soil type formed in the subtropical zone.
Magnetic susceptibility in the S5 varied from 120 to 310 SI(10-8 m3 kg-1)was well above
the turnout of the S0, signified intensive pedogenesis under much warmer and wetter
climatic condition than that during the mid-Holocene.
Nevertheless, the results of mineralogy analysis showed the similar composition of
phyllosilicate minerals throughout the complex paleosol (S5-1, S5-2, S5-3). Mineral
weathering processes in the S5 were depotassication and hydration of primary minerals and
degradation of chlorite. The S5 did not shown more intensive mineral weathering than the
L5 and L6 which was incompatible with the results of CaCO3 content, particle size
distribution and magnetic susceptibility. One of the possible reasons was that the trapping
affection of harder and denser of CaCO3 illuvial horizon and argillic horizon in each
paleosol pedons on the water percolation which listened for the loss of alkali and alkaline
earth elements and restrained the transformation of soil mineral.
Key Words : Soil; Loess-paleosol; Mineral weathering; Pedogenic environment;
Development of soils;

Language中文
Document Type学位论文
Identifierhttp://ir.iswc.ac.cn/handle/361005/8935
Collection水保所知识产出(1956---)
Recommended Citation
GB/T 7714
黄传琴. 黄土剖面粘粒矿物的组成特征及其环境意义[D]. 北京. 中国科学院研究生院,2011.
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