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Unsaturated tropical residual soils and rainfall induced slope failures in Malaysia
Published in H. Rahardjo, D.G. Toll, E.C. Leong, Unsaturated Soils for Asia, 2020
Large deposits of colluvium often exist in conjunction with residual materials, particularly as colluvial fans on footslopes of hillsides. Colluvium is material derived from the weathering of any parent rock which has been transported downhill by the agencies of gravity and water. It can range in general composition from a collection of matrixless boulders at one extreme to a fine slopewash material at the other. It poses many of the same general characteristics as residual material, particularly in the context of engineering behaviour. Because it is commonly found as slope cover over weathered rock profiles, it is sometimes difficult to distinguish between colluvium and the in situ material if only drillhole samples are available for examination. For geotechnical engineering purpose, colluvium can therefore be grouped with residual soil.
Landslide movement monitoring as an element of landscape protection
Published in Soňa Molčíková, Viera Hurčíková, Vladislava Zelizňaková, Peter Blišťan, Advances and Trends in Geodesy, Cartography and Geoinformatics, 2018
The landslides examined by the authors (with the total of nine distinguished landslide areas) to be found within the Kadzielnia reserve are of the insequent type. The shearing surface partly belongs to the weathered rock area and partly runs along the fissure surface. Colluvium consists of detritus-block material (granular soils, weathered rock, rock boulders). Due to the almost vertical slope wall, the mass movement in the area of Kadzielnia can also be classified as falling.
Landslide risk management
Published in David M. Cruden, Robin Fell, Landslide Risk Assessment, 2018
Mt. Dandenong (620m above sea level) is part of the Dandenong Ranges which form a prominent ridge with steep forest covered northwestern slopes. For the purpose of the study, these slopes were divided into 26 labelled catchments. The ridge is made up of weathered volcanic rocks overlain by residual soils. Colluvium occurs on the lower parts of the steep slopes, and in fan deposits downhill from gullies at the base of the slopes.
Risk assessment of agricultural soils surrounding an iron ore mine: A field study from Western Ghat of Goa, India
Published in Soil and Sediment Contamination: An International Journal, 2023
Amrita Daripa, Sudipta Chattaraj, Lalchand Malav, Prasenjit Ray, Ramprasad Sharma, Deepak S. Mohekar, Ramamurthy V, Mahendra S. Raghuvanshi, Nitin G. Patil
The study was conducted in the area surrounding an iron mine site of Bicholim Block of Goa state that lies at the foothills of Western Ghat. The present study area extended from 73° 52’ 25”E to 73° 57’ 15” E longitudes and 15° 33’ 55” to 15°37’ 45” N latitudes, covering an area of about 2192 ha (Figure 1). It is an ecologically fragile land characterized by undulated topography and tropical monsoon climate with hot humid weather having mean maximum temperature; annual rainfall and relative humidity of 35°C, 2932 mm and 70%, respectively. The soils of study area were mostly lateritic impregnated with alluvium and colluvium deposits at low land. Mean elevation of the study area ranged from 0 to 168 m above mean sea level (Figure S1a) indicating the presence of hilly to plain landforms. The iron ore mine is situated along the summit surrounded by forest and scrubs present in the moderately steeply to steeply sloping side slopes (Figure S1b). Subsequently at the low lands, slopes flatten out and cultivated lands are mostly present in this zone; majority of which are turned into fallow lands as indicated in the land use land cover map (Figure S1c) due to long-term mining deposits accumulation from uphill side that led to poor soil drainage. The geology of the study area is characterized by undifferentiated parent material at the undulating terrain, schist in the mine area, colluvium and alluvium deposits in low lands (Figure S1d). The principal crops include rice, coconut, areca nut, cashew nut, and vegetable crops.
Assessing the Lithium Potential of the Paleoproterozoic Rocks of the West African Craton; the Case so Far
Published in Geosystem Engineering, 2023
The pegmatites of Issia, in the Western part of Côte d’Ivoire, are known to host pegmatites which contain significant deposits of lithium (Allou, 2005). This area is the only location in Côte d’Ivoire where the production of columbo-tantalite is carried out in the form of eluvium, colluvium and alluvium which has an inferred relationship to the granitic rocks of the area. The suspected host granitic rocks include the two mica granite known as the Lobo type; oriented granite with dominant muscovite (Bitapia type) and unoriented porphyritic granite with dominant muscovite (Issia type). These granites intrude into the Lower Proterozoic sedimentary rocks (Allou, 2005). The most potentiate pegmatites in the Issia area or the Nb-Ta-Be-Li pegmatites are related to Issia-type granite. They can be grouped into four main types: type A, consisting of sterile pegmatites, type B, consisting of beryl pegmatites, type C, consisting of beryl pegmatites and columbo-tantalite, type D, consisting of beryl pegmatites, columbo-tantalite and lithiniferous micas.
Geomorphic provinces and regolith-landform evolution of the Capricorn Orogen, Western Australia
Published in Australian Journal of Earth Sciences, 2021
R. L. Thorne, S. C. Spinks, R. R. Anand
The most obvious silicified features in the landscape are silcrete capped mesas. Here silcrete has replaced and cemented both Mesoproterozoic sediments and younger colluvium and alluvium. The silcretes precipitated in topographic lows when fluids became saturated with respect to silica. Silica may be sourced at a distance from the site of precipitation and stay in solution for an extended period before precipitation occurs (Stephens, 1971). Taylor and Eggleton (2017) suggest that in stagnant or slowly flowing water the presence of organic material leads to a lower pH that can result in the etching of quartz and the combined break down of aluminosilicate and mafic minerals. The addition of silica saturated groundwater with a higher pH to this system will precipitate silica as the pH increases. Climate change, landscape evolution or sealing of the pore spaces can then lead to a reduction in the ingress of water (Taylor & Eggleton, 2017). Crystalline quartz can then be precipitated, forming silcrete (Thiry & Millot, 1987). After silcrete precipitation landscape inversion leads to the formation of silcrete capped mesas.