The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Deposits of cobbles and boulders found hanging on midslopes of the Itatiaia Plateau reflect tectonic reactivation and a large range of climate-controlled processes, probably including frost weathering. These processes, more efficient in detaching debris from freefaces, were replaced, at the end of the Pleistocene, by colluviation. On the lower slopes of the plateau, less coarse C I and C...
The erosion rates in the Vallcebre basin (Pyrenees) are controlled predominantly by the physical weathering rate of bare regolith, i.e. mudrocks. To obtain information on the influence of thermic and moisture regimes on the weathering dynamics, laboratory experiments were carried out to investigate how freezing-thawing or wetting-drying cycles, under controlled conditions, affect structure and porosity...
The geochemical behaviour of specific elements in fluvial sediments, topsoils, soil profiles and plant material on a sequence of Quaternary alluvial terraces was reconstructed semi-quantitatively using indices of accumulation or depletion with respect to abundance in the lithosphere, local soils and sediments. Topsoils of different ages and soil profiles are most clearly differentiated by the degree...
In calculating catchment weathering rates using strontium isotope ratios, one of the parameters required is the 87 Sr/ 86 Sr ratio of the streamwater. The effect of flow rate on this ratio is not well understood with conflicting reports in the literature. To provide more detailed information on the effect of flow rate on strontium isotope ratios, the 87 Sr/ ...
Landscape evolution in terrains that have been unaffected by glacial or aeolian erosion, occurs by cycles of deep weathering and stripping. Several factors have been proposed to control these cycles including sea level, climate and tectonics. In this study, a tectonic model of landscape evolution recently developed for Uganda, was tested by detailed study of the weathered mantle. The study involved...
A combination of micromorphology and different in situ sub microscopical techniques, performed on thin sections of soil, saprolite, and rock samples, was used to assess possible relationships between micro- and nano-variability and macro- and micro-environmental conditions of mineral transformation during weathering. Four examples, presented in this study illustrate variability in morphology, chemistry...
Microscopic study of twelve weathering profiles developed on granitic rocks in Galicia (NW Spain) showed that, in most cases, the transformation of the parent rock into saprolite occurs with pseudomorphic alteration of the plagioclases. It was seen that the transformation and the retention of plagioclases in the alteration profile are directly related to the conservation of the general structure of...
Weathering of a calcalkaline granite was studied in the south of Galicia (NW Spain) where the average annual precipitation is 1400 mm and the average annual temperature is 12 o C. The original rock contains perthitic K-feldspars, plagioclases with inclusions of muscovite and opaque minerals, quartz and chloritized biotite, with apatite, zircon, sphene and opaques as accessories. In the saprolite...
The existence of erosion surfaces has long been recognised as a macroscale feature of the southern African landscape. Evidence is presented here to demonstrate that laterisation as a soil process affected the calcareous Tertiary Wankoe Formation of the southern Cape. Remnants of the Tertiary African Surface along the southern Cape Coastal Plateau are characterised by deep weathering mantles capped...
Weathering and soil formation rates are regarded as the main criteria of a tolerable soil loss. The efficiency of weathering in the seasonal semiarid tropics has often been greatly over-estimated especially in the geomorphologic literature in which weathering is assumed to be as fast or even faster than surface erosion. Six selected ''Red Soils'' in two intramontane basins of hyperthermic SW Nepal...
Profile development indices of Harden [Harden, J.W., 1982. A quantitative index of soil development from field: examples from a chronosequence in Central California. Geoderma 285, 1-98] and Ferrari and Magaldi [Ferrari, G., Magaldi, D., 1983. Significato ed applicazioni della paleopedologia nella stratigrafia del Quaternario. Boll. Mus. Civ. St. Nat. Verona 10, 315-340] have shown their utility for...
The effects of weathering in a Mediterranean climate on the mineralogy and microfabric of Paleozoic gneiss of the Sila Massif, Calabria, southern Italy, have been studied. Field observations show highly weathered rock forms a residual soil. Micromorphological and mineralogical properties of bedrock and saprolite show that the weathering process is characterized by at least two major stages, having...
The soils of Galicia, NW Spain, developed on gabbro often include one or more buried profiles. In the modern overlying soil, gibbsite is common and the Fe oxyhydroxides include maghemite. In the buried soil interstratified kaolinite-smectite is abundant, gibbsite is present in traces and the Fe oxyhydroxides are mostly formed by goethite. Chemical and mineralogical data show that the modern soil has...
To examine the rate of chemical weathering, field experiments using microweight-loss techniques were carried out. Two kinds of porous rhyolite forming lava domes in Kozu-shima Island were selected: (1) a younger rock (weathering period is 2.6 ka) and (2) an older rock (20 ka). Both rocks seem to have been very similar in their initial composition and structure. They have, however, different properties...
The weathering of a Late Miocene gypsum-calcareous mudstone outcropping in large badland areas of SE Spain, under a semi-arid Mediterranean climate, was studied by means of two experimental approaches. Field and laboratory experiments were carried out to reproduce, though in accelerated form, some of the weathering conditions of the consolidated mudstone. In the laboratory, three sequences of 5, 10...
Two soil chronosequences of mountainous ecosystems in Switzerland served as the basis to calculate the accumulation of soil organic matter, transformation of pedogenic Fe and Al and net losses of the main elements (Ca, Mg, K, Na, Fe, Al, Mn and Si) by means of mass-balance calculations. Elemental losses due to deglaciation and exposure to the weathering environment were calculated. These mass balance...
Carbonate leaching rates in several soils in Switzerland and in the Lake Constance region were calculated and related to landscape development. The leached depth of the soil, the carbonate content and the soil density profile are sensitive to soil age. A first database of carbonate leaching and its relationship to soil age is presented. A simple relationship between the amount of precipitation and...
This paper characterizes the weathering products of the two-mica Oporto granite in terms of its mineralogical, chemical, geotechnical and physical properties. This information is used to identify a physical property that can be used as an index of the degree of weathering and to estimate other properties. In outcrop, the Oporto granite is always weathered and weathering profiles frequently exceed...
Upland and shield areas of central and northwestern Europe are characterised by an abundance of relict weathering mantles (saprolites). These saprolites, if accurately dated and interpreted, may serve as an important complementary source of information about long-term environmental history. In this paper, methods used to establish ages of weathering mantles are reviewed, such as stratigraphic and...
The stone circle complex at Copney, County Tyrone is a key Bronze Age site that forms part of the Mid-Ulster stone circle complex. This site was excavated in 1995 and since then, deterioration of the archaeological stonework has been a serious problem. Deterioration is visible as splitting/fracturing of stones, the development of a bleached outer margin, surface scaling and granular disintegration,...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.