Chemical weathering in a drainage basin underlain by old red sandstone     

M. J. Waylen 《地球表面变化过程与地形》1979,4(2):167-178

A hydrochemical budget is used to quantify the rate of chemical weathering and solutional denudation on Old Red Sandstone in East Twin drainage basin (0.2 km²) on the Mendip Hills for the 1972–73 Water Year. Net nutrient uptake by the biomass and precipitation inputs are subtracted from stream solute outputs to give an estimate of the solutes released to the system by weathering. The mineralogies of the sandstone and the soil are compared to predict possible weathering reactions for the primary and secondary minerals. Tentative estimates of primary mineral alteration and secondary mineral formation are then made by substituting the hydrochemical balances into the formulated weathering reactions. Finally the rate of solutional denudation (0.8 tonnes/a or 1.6 mm/100 a) is compared with other estimates of solutional and mechanical denudation at East Twin and with similarly derived results for other lithologies.  相似文献   

Enhanced boulder weathering under late-lying snowpatches     

Colin K. Ballantyne  Nicola M. Black  Donna P. Finlay 《地球表面变化过程与地形》1989,14(8):745-750

A Schmidt test hammer was employed to assess the aggregate surface hardness of samples of boulders dug out from under late-lying snowpatches at sites in Switzerland, Scotland and Norway. The results were compared with an equivalent set of readings made on boulders at nearby snow-free control sites. The results in every case reveal that the aggregate surface hardness of boulders buried by late-lying snow is significantly less (at the 0·001 level) than that of boulders at the corresponding control sites. This result indicates that late-lying snow significantly enhances rock weathering, probably because boulder and rock surfaces are exposed to prolonged wetting by percolating meltwater under late-lying snowbeds.  相似文献   

河南不同成因类型铝土矿的矿石特征   总被引：4，自引：0，他引：4  

陈廷臻  张天乐 《矿物学报》1989,9(1):89-94

本文在对铝土矿石物质组成研究的基础上,运用电子显微镜(EM)对河南两类不同类型铝土矿床的矿石结构进行了观察研究。根据EM观察到的铝土矿石显微结构的不同形貌特征,划分出三种矿石结构类型:致密-隐晶结构、粒状镶嵌结构和粒屑结构。由此归结为两个成因类型:古风化壳异地堆积亚型和古风化壳原地堆积亚型的铝土矿床。  相似文献   

水工混凝土构筑物防冻蚀措施     

朱清华 《冰川冻土》1992,14(3):270-276

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Structural integrity of cracks in the head of Washington on Mount Rushmore     

Zbigniew Hladysz 《Geotechnical and Geological Engineering》1989,7(4):315-322

Summary Preliminary studies of the stability of Mt Rushmore shows a tendency for permanent crack deformation resulting from seasonal opening and closing of cracks in the structure.  相似文献   

南方红土的剖面风化特征   总被引：11，自引：2，他引：9  

熊尚发  刘东生  丁仲礼 《山地学报》2000,18(1)

对地处九江的南方红土所作的观察和元素地球化学分析表明 ,南方红土在剖面上存在风化强度的系统变化特征。剖面下部对应网纹红土的层位风化强度大大高于剖面上部对应褐黄色土的层位 ,其中氧化铁游离度从下部 90 %降至上部 4 5 %左右 ,相当于从砖红壤环境转变为红壤环境。这种风化强度的系统变化在北方黄土地层中没有相似表现 ,但可能与黄土记录的中更新世晚期以来粉尘通量逐步加大、干旱化程度逐步加深有着某种关联 ,暗示中更新世晚期以来可能存在较为普遍的气候恶化趋势。  相似文献   

丹棱-思濛扇积物中的漫洪相粘土层   总被引：1，自引：0，他引：1  

张倬元  陈叙伦  刘世青  夏克勤 《山地学报》2000,18(Z1):1-7

在简述丹棱-思氵蒙冲积扇上覆粘土层的分布与特征之后,应用粒度分析方法和孢粉组合来论述其沉积环境,并尝试应用粘土矿物与土体中易累积的稳定化合物含量与淋溶系数(ba)等所代表的粘土风化程度来论证该粘土层的相对年代。  相似文献   

Provenance of Middle Jurassic clastic rocks from the Bogda area of Eastern Tianshan and its implications     

Hongjie Ji  Junli Qiu  Hengye Wei 《International Geology Review》2020,62(10):1319-1342

ABSTRACT

The siliciclastic rocks in the Xishanyao (XSY) and Toutunhe (TTH) formations recorded the Middle Jurassic palaeogeographic evolution processes of the Bogda Mountains. To explore their provenance, the geochronological, geochemical, and petrological characteristics of the Middle Jurassic sandstones from the west Bogda area are analyzed in this study. The detrital grains of sandstones are generally poorly to moderately sorted and subangular to subrounded. Low to moderate CIA* (chemical index of alteration), PIA (plagioclase index of alteration), CIW (chemical index of weathering) and relatively high ICV (index of compositional variability) values indicate the overall low to moderate weathering intensity, low sediment recycling, and abundant first-cycle siliciclastics supply. The abundant acid volcanic lithic fragments and element contents/ratios of the sandstones indicate source areas dominated by felsic rocks. The detrital zircon U-Pb age spectrum of the lower XSY Formation is dominated by a single Carboniferous age group. Multiple Palaeozoic zircon U-Pb age groups exist in the middle-upper XSY Formation. The TTH Formation has a typical age of late Middle Jurassic. Combined with the sedimentological characteristics, it reveals that (1) the Eastern Bogda Mountains (EBM) were the only provenance for the lower XSY Formation; (2) both the Yemaquan arc and the EBM provided detritus for the middle XSY Formation; (3) the Yemaquan arc became a minor provenance for the TTH and upper XSY formations. Middle Jurassic palaeogeographic evolution in the EBM is inferred as follows: (1) during the deposition of the lower XSY Formation, the EBM suffered a rapid uplift and became an obvious positive relief; (2) the palaeorelief became high in the Yemaquan arc area and low in the EBM during the deposition of the middle XSY Formation; (3) the Yemaquan arc was considerably eroded, which caused the palaeotopography to decline sharply during the deposition of the upper XSY Formation; (4) the EBM uplifted again during the TTH Formation period, accompanied by volcanic activities at ~165Ma.  相似文献   

Experimental simulation of rapid rock block disintegration by sodium chloride in a foggy coastal desert     

A.S. Goudie  A.G. Parker 《Journal of Arid Environments》1998,40(4):347-355

An environmental chamber was used to simulate a 24-h cycle of rock surface temperature and relative humidity, a stone pavement with differing levels of sodium chloride content, and differing levels of fog precipitation to assess some of the controls of rock weathering in the vicinity of Swakopmund in the Namib Desert. The rock employed was Cretaceous Chalk. Some treatments were effective at causing disintegration after 76 temperature/humidity cycles and 10 fog cycles. Small amounts of fog moisture (0.5 mm per event) were associated with the greatest amounts of breakdown, whereas the amount of salt in the simulated pavements appeared to be of less significance. The experiment showed that sodium chloride can be an effective agent of weathering in a coastal foggy environment.  相似文献   

Effects of direct and indirect heating on the validity of rock weathering simulation studies and durability tests   总被引：2，自引：0，他引：2  

P. A. Warke  B. J. Smith 《Geomorphology》1998,22(3-4)

Rock surface and subsurface temperature responses in samples exposed to direct heating (insolation) under natural hot desert conditions reveal considerable variability between lithologies related to differences in thermal properties, especially albedo and thermal conductivity. However, when the same samples are heated indirectly by air in an oven-based environmental cabinet, lithological differences in temperature response disappear and all samples attain temperatures similar to the air temperature within the cabinet. Rates and patterns of rock decay produced in such environmental cabinets may not, therefore, reflect those encountered under natural conditions, where breakdown is related to micro-environmental conditions at the rock/air interface and where rock temperature is one of the most important controlling factors. In addition to implications for assessment of weathering effectiveness, use of only indirect forms of heating affects the determination of comparative rock durability because all rock types are cycled through the same temperature regimes. Because temperature exerts such a major control on rock breakdown through its control on physical and chemical weathering processes, all significant factors influencing it must be included in the design of weathering simulations and durability tests.  相似文献