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1.
根据砾石风化圈厚度估算地貌年龄* 总被引：8，自引：0，他引：8
对砾石风化与时间关系的定量研究表明,二者关系是非线性的。实事上,由于风化残余物对风化过程的抑制作用,大部分砾石的风化速率随时间减小,有的与时间呈指数关系,这样,便可以根据砾石风化圈厚度估算地貌年龄。该方法自六十年代开始兴起,经过几十年的实践,已日趋成熟。近来我们在我国西部河西走廊中段进行了这方面研究。本文系统介绍了该方法的研究状况。 相似文献
2.
关中平原420-350 ka BP的古土壤与环境 总被引：3，自引：0，他引：3
通过对关中平原双竹村剖面、寇家坡剖面以及蓝田田家坡剖面、三官庙剖面、长安四府村剖面和宝鸡马家塬剖面黄土沉积中第4层古土壤的分析，发现西安、长安、蓝田和宝鸡中更新世中期发育的第4层古土壤已转变成为风化壳，厚度变化在3．5～3．7m之间。它由4层组成，最上部的第1层是发育好的红棕色粘化层(Bts)，第2层是具有铁质胶膜的风化淋滤黄土层(Cs)，第3层是不含铁质胶膜的风化淋滤黄土层(Cl)，第4层是CaCO3结核层(Ck)。对风化剖面中CaCO3含量、pH值、黏土含量，元素Sr、Fe2O3和Al2O3分析，表明该风化剖面受到了较强烈的风化淋溶和黏土化作用，并指示当时的风化淋滤深度明显超出了土壤粘化层的厚度。粘化层中黏土胶膜具亚热带土壤胶膜特征，具超微晶粒结构，由新生的蒙脱石、高岭石和伊利石微晶粒构成，明显定向排列，这是其具有光性的原因。风化壳型古土壤的发育表明，在距今42．35万年前后，黄土高原东南部盛行亚热带气候。这一古土壤剖面构型为Bts-Cs-Cl-Ck-C，它发育时的年平均温度和降水量分别约为16℃和1000mm，比现代关中平原高约30℃和400mm。 相似文献
3.
南岭最高夷平面上发育了深厚的红色风化壳,研究这些风化壳对于认识夷平面具有重要意义。以粤北大布镇夷平面上的风化壳为例,通过化学成分的研究,认为大布镇的风化壳厚度为60～70 m,风化壳顶层的母岩当量厚度可达到24 m/m。据此,恢复得到已风化母岩(奥陶系砂岩)厚度达790 m,其中的淋失量为724 m,再根据珠江流域50 a平均溶蚀速率估算,该风化壳的年龄约为19.6 Ma,即中新世早期,大致可认为是南岭夷平面发育终结和新一轮地貌循环——"南岭运动"开始的时间。 相似文献
4.
在热带条件下，不同种类岩石受到强烈的化学风化作用，并导致某些环境问题，香港在这方面提供了十分典型的例子。在香港，岩石风化厚度可达８０ｍｉｎ，普通成岩矿物长石和云母被转化为粘土矿物埃洛石和高岭石，风化岩密度一般降低４０％￣８０％，埃洛石密度看来是亚稳定的，随年龄的增加而降低。在老于晚侏罗纪或早白垩纪的岩石中，还未临别出埃洛石。埃洛石、高岭石及其风化产物少含植物所需营养元素，且阳离子交换能力低，因而所 相似文献
5.
选择湟水河流域湟源至乐都段为研究点,采集并分析了湟水河及支流北川河、南川河河道不同地点25个河床泥沙样品的常量元素地球化学特征。通过化学风化强度指标(CIA)分析,发现从湟源—湟中(多巴)—西宁—平安—乐都段,化学风化强度呈现出高—低—稍高的趋势。通过化学风化强度与影响因素(温度、降水、海拔高度、植被覆盖和人口因素)的对比分析,发现湟水河流域引起化学风化强度明显变化的主要因素是降水量的变差系数。 相似文献
6.
青海湖区是研究亚洲季风和西风环流强度变化和相互作用的良好区域。与青海湖湖泊钻孔沉积物一样,青海湖岸边广泛堆积的陆相风成沉积独立地记录了青海湖区晚第四纪以来的环境演变。过去对青海湖风成沉积的元素地球化学特征虽有过一些研究,但对于这套风成沉积的化学风化研究相当薄弱。通过对青海湖东岸种羊场剖面晚第四纪风成沉积的常量元素组成及主要的化学风化指标进行研究,结果表明:1)化学风化指标CIA(化学蚀变指数)、CIW(化学风化指数)、K2O/Na2O和Fe2O3/Mg O比值均反映了种羊场风成沉积经历了早期化学风化强度弱、中期强和晚期再度变弱的变化特征;2)在距今~5 ka时,风化指标显示化学风化作用最强,可能记录了青海湖区暖湿的气候特征;3)种羊场风成沉积的Fe2O3/Mg O比值与!fd%(频率磁化率的百分比)呈显著线性正相关(相关系数R2为0.939),指示在化学风化过程中Fe元素的富集对于磁化率增强具有重要贡献。 相似文献
7.
放射性水化学晕圈对于铀矿选定靶区和寻找深部盲矿体具有重要的意义。通过前人在下庄矿田发现的放射性水化学异常点,圈定放射性水化学异常晕圈,总结了放射性水化学异常晕圈的分布特征及其与岩性(相)、构造体系、矿床(点)之间的关系,为今后在本地区开展放射性水化学寻找铀矿体,提供了重要地借鉴意义。 相似文献
8.
中晚全新世以来玛曲高原的化学风化过程演变 总被引：2，自引：1，他引：1
在对玛曲高原东南部具有代表性的黄土-古土壤-风成砂沉积剖面进行常量、微量元素及地球化学风化参数分析的基础上,结合14C测年结果,探讨了中晚全新世以来玛曲高原的化学风化过程。结果表明:(1)不同地化学元素在剖面中的化学活性表现出明显的差异性,常量元素Ca、Si、Na以强烈迁移淋失为主,Fe、Mg则表现为明显富集;元素活动性及迁移顺序为Ca >Si >Na >Al >K >Fe >Mg;常量元素的迁移特征表明玛曲高原处于脱Ca、Na的初期化学风化阶段;微量元素除Sr迁移淋失显著外,Cu、Mn、Zn均呈现出强富集特征。(2)根据典型地化学元素记录的冷干-凉润-凉干-温湿的气候变化过程,结合化学风化指标将玛曲高原中晚全新世以来的化学风化过程划分为3.8 ka BP以前的风化较弱期、3.8~3.5 ka BP风化较强期、3.5~1.6 ka BP风化减弱期和1.6 ka BP以来的风化增强期4个阶段。 相似文献
9.
萨拉乌苏河流域末次间冰期 古土壤化学风化与古气候 总被引：7，自引：0，他引：7
内蒙萨拉乌苏河流域米浪沟湾剖面末次间冰期发育5 层古土壤。对这5 层古土壤的形 态特征、粒度、扫描电镜及化学风化等分析结果表明: (1) 这些古土壤具有与华北现代褐土相 似的形态特征; (2) 粘化率中部高和石英颗粒表面硅质溶蚀-沉淀现象表明古土壤层中发生过 风化成壤作用; (3) 用K2O/Na2O、Al2O3/Na2O、MnO/Al2O3、CIA 及A-CN-K 图解与华北现代 褐土作对比分析, 发现它们的化学风化特征极为相似; (4) 用气温及降水量与CIA 值的回归 关系方程, 得出5 层古土壤发育时期的水热状况确与华北现代的暖温带半湿润季风性气候大 致相同或更显暖湿。形态特征、粒度、石英颗粒表面特征和化学风化特征等多个方面具备了 与现代华北褐土类似的化学风化成壤特征, 证明这些古土壤是在与华北相似的暖温带半湿润 季风性气候条件下形成的。 相似文献
10.
《亚热带资源与环境学报》2016,(2)
运用野外形态观察、元素地球化学和磁学相结合的方法对新近发现的甘肃东部地区晚泥盆世古土壤剖面进行了辨识和分析,从而得出:1)该套地层中残留有原土壤发生过程的痕迹,如根迹、浅褐色晕圈状根迹,原生石膏层,红色古土壤层内富含成壤钙结核及结核层。同时,可见圆顶柱状结构、次棱角块状结构等古土壤特有的结构类型,这些特征表明该套地层为古土壤。2)古土壤发生层次明显。可识别出红色淀积层(B层)和灰绿色母质层(C层)。B层磁化率向上增强,常量及微量元素Al_2O_3、Fe_2O_3、K_2O、Sr含量及Al_2O_3/SiO_2比值向下减少,Zr、Ti向下富集,以及风化指数CIA向下增加。磁化率及元素含量和比值特征反映了B层古土壤的风化成壤程度向下增强。3)依据发生学特征初步判断古土壤的类型主要为始成土、旱成土和变性土,反映了当时较干旱的气候条件。晚泥盆世沉积地层中古土壤层的发现对指示重大地质事件和研究环境变化方面有着重要的地学意义。 相似文献
11.
In situ quantification of localized weathering processes on basalt flows in New Mexico and Hawaii demonstrates that small‐area factors can be more important than other more readily observable factors. Further, it demonstrates that the factorial concept of the Pope Boundary‐Layer weathering model is partially solvable, that organic weathering can accentuate glass weathering (with implications for climate models and storage of nuclear waste), and that silica coatings are not a simple solution for the preservation of stone monuments. Enhancement of glass weathering by lichens on the McCartys flow, El Malpais National Monument, New Mexico, remains restricted to a half‐millimeter directly underneath the lichen‐covered surface. In contrast, although the inorganic rock coating of silica glaze reduces weathering directly underneath the coating by up to nine times rates found in uncoated locales, silica glaze can almost double variability in weathering along its margins. 相似文献
12.
开展广泛的磁化率特征研究是目前中国南方红色风化壳环境磁学研究的一个重要内容。通过对昆明西山4个峨眉山玄武岩风化壳剖面进行系统的磁化率测定发现,所有剖面磁化率值都呈现自剖面底部向顶部增高的趋势,这一现象与以往流行的玄武岩风化壳磁化率值随风化成土过程的加深而减小的模式有较大出入。磁化率与频率磁化率的对比分析结果进一步表明风化过程中形成的超顺磁颗粒可能是本区玄武岩风化壳(至少顶部60 cm区域)磁化率增强的主要贡献者。 相似文献
13.
Norikazu Matsuoka 《Geomorphology》1995,12(4)
Field observations of weathering processes and the related landforms, combined with laboratory analyses of weathering products, permit a synthetic evaluation of Late Cenozoic weathering environments in the Sør Rondane Mountains, Antarctica, an arid upland characterized by low temperatures and strong winds. Rates and character of weathering depend mainly on moisture availability and the bedrock geology. Under the humid weathering regime that occurs only locally around the margin of the present sheet, frequent diurnal freeze-thaw cycles in summer cause relatively rapid rock fragmentation. Most of the mountains are situated in the arid weathering regime, under which rock breakdown is very slow unless the rock contains plenty of salts. Salt weathering becomes more intensive and extensive with exposure age, as a result of salt accumulation in rock, eventually producing soils as small as fine-silt size. Lack of clay mineralization even in weathered rocks having been exposed above the ice sheet prior to 4 Ma ago indicates that hydrolysis or carbonation of rock minerals has been insignificant during the past 4 Ma. The final products of weathering are due mainly to salt action and reflect the parent lithology. Resistant fine-grained granite forms strongly oxidized tors carved with tafoni, or fields of mushroom-like boulders overlying the fractured bedrock. Less resistant rocks, like biotite gneiss and amphibolite, produce stone pavements underlain by saline, silty soils up to 30–40 cm thick, the thickness of which corresponds to the maximum thaw depth. 相似文献
14.
《极地研究》1992,3(2):8-27
The chief aim of this study is to investigate the chemical weathering process of the weathering crust in Great Wall Station region of China (in Fildes Peninsula), Antarctica by the method of sedimentology. CW,SW,GW,TW,WE weathering crusts developed on volcanic clastic rock, gray aptitic basalt with tuff or basaltic bedrock. On change of minerals, geochemical behaviors of elements, migration and enrichment regularities of elements, Correlation between element geochemical behaviors, change of weathering potential of rocks in chemical weathering process are studied by us. We can see that the sequence fo weathering strengths of the abovementioned sections, from high to low, should reflected in TW, GW, CWand SWF and basical correspond with that calculated from the enrichment and differentiation indexes. 相似文献
15.
The objective of this study is to ascertain the relative importance of lithological controls and geomorphological processes in the development of Drakensberg basalt terraces. Various hypotheses for terrace formation are considered, including geological controls, macroscale geomorphology, and climatic–geomorphological controls. The variations in strength and relative age differences for scarp surface exposures on two slopes of varying aspect are determined, so that a comparison can be made between various scarp outcrops and relative rates of weathering. Scarp outcrops were measured for their rock mass strength, rock surface roughness, and percentage lichen cover. The ethylene glycol test was performed on prepared rock samples to determine susceptibility to tensional breakup. A satellite image depicting the distribution of late-lying contemporary snow was used to assist in the construction of topo-climatic linkages with scarp terrace localities. Findings show that terraces are most common on southeast-facing aspects, and coincide with the major joint strike direction. Lithological factors are thus considered the primary control to such terrace development. It is suggested that a different set of geomorphological processes operates on various slope-altitudinal and slope-orientational positions at any given time. 相似文献
16.
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。 相似文献
17.
Norikazu Matsuoka Cline E. Thomachot Chiaki T. Oguchi Tamao Hatta Masahiro Abe Hiroyuki Matsuzaki 《Geomorphology》2006,81(3-4):408-420
Rates and processes of rock weathering, soil formation, and mountain erosion during the Quaternary were evaluated in an inland Antarctic cold desert. The fieldwork involved investigations of weathering features and soil profiles for different stages after deglaciation. Laboratory analyses addressed chemistry of rock coatings and soils, as well as 10Be and 26Al exposure ages of the bedrock. Less resistant gneiss bedrock exposed over 1 Ma shows stone pavements underlain by in situ produced silty soils thinner than 40 cm and rich in sulfates, which reflect the active layer thickness, the absence of cryoturbation, and the predominance of salt weathering. During the same exposure period, more resistant granite bedrock has undergone long-lasting cavernous weathering that produces rootless mushroom-like boulders with a strongly Fe-oxidized coating. The red coating protects the upper surface from weathering while very slow microcracking progresses by the growth of sulfates. Geomorphological evidence and cosmogenic exposure ages combine to provide contrasting average erosion rates. No erosion during the Quaternary is suggested by a striated roche moutonnée exposed more than 2 Ma ago. Differential erosion between granite and gneiss suggests a significant lowering rate of desert pavements in excess of 10 m Ma− 1. The landscape has been (on the whole) stable, but the erosion rate varies spatially according to microclimate, geology, and surface composition. 相似文献
18.
STEFAN GRAB 《Geografiska Annaler: Series A, Physical Geography》2007,89(3):185-193
Rock temperature data are presented for a variety of topographic localities at a high Drakensberg site. The objective is to investigate the spatiotemporal variations of surface rock temperatures in high Drakensberg basalt. The temperature results are then used to discuss possible implications for thermal stress fatigue and frost‐induced weathering. Tinytalk? data loggers and probes were used for rock‐surface temperature recording. Long‐term measurements were recorded over 12 months from May 2002 to April 2003, at a 1‐hour logging interval and rock depth of 1 cm for a highaltitude (3300 m a.s.l.) interfluve and fracture site. Whilst the north‐facing rock surface experiences negligible hours below ?3°C, the south‐facing rock surface and interfluve sites are subjected to considerable periods below ?3°C, which falls within the ‘frost cracking window’. It is concluded that the substantial contrasts of recorded rock thermal parameters over small spatial scales between various topographic settings, highlight that site‐specific measurements across the broader scale are required for an adequate evaluation of regional weathering and its associated landform development. 相似文献
19.
中国花岗岩地貌的类型特征与演化 总被引：7，自引：1，他引：6
在中国南方亚热带季风气候条件下, 自中、上新世以来的夷平面及其深厚的花岗岩风化壳在后期不同程度构造抬升-下切过程中, 造成许多中国特有的花岗岩地貌类型, 如黄山和三清山等处的花岗岩峰林、石林、造型石、风动石等。本文讨论了中国花岗岩风化壳和地貌的时空演化规律, 提出地貌发育年代与中、上新世广布的夷平面的密切关系, 以及在不同抬升背景下, 花岗岩地貌与风化壳的关系。并可据此推算不同山地的抬升幅度, 沿海仅抬升约200m, 向内地逐渐增大, 到南岭或大别山、伏牛山则达到约1600~2000 m。 相似文献