Mineralogical and grain size composition of clays developing calanchi and biancane erosional landforms |
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| Institution: | 1. College of Tourism and Environment Science, Shaanxi Normal University, Xi''an, China;2. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, CAS, Xi''an, China;3. College of Geographical Sciences, Fujian Normal University, Fuzhou, China;1. GeoQuest Research Centre, School of Earth and Environmental Sciences, University of Wollongong, Wollongong, 2522 NSW, Australia;2. Desert Research Institute, Nevada System of Higher Education, Reno, NV 89512, USA;1. Department of Geography, Hebrew University of Jerusalem, 91905 Jerusalem, Israel;2. Soil Erosion Research Station, Ministry of Agriculture, Bet Dagan, Israel;3. Ariel University, Department of Civil Engineering, Ariel, Israel;4. Institute of Chemistry, Technology and Metallurgy, Belgrade, Serbia;1. Departamento de Enxeñaría de Recursos Naturais e Medioambiente, Escola de Minas, Universidade de Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain;2. CERENA, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;3. Defense University Center at the Naval Academy, Universidade de Vigo, Plaza de España, 36920 Marín, Spain |
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| Abstract: | Clayey terrains outcropping in many parts of Italy are frequently affected by accelerated erosion processes producing landforms known as calanchi and biancane. The calanchi are intensely dissected landscapes, presenting rill and gully landforms and a dense dendritic drainage network. The biancane are landforms characterized by bare cones and hummocks, separated by flatter areas of surface wash deposits. The factors controlling the development of these two landforms are still poorly understood. This study was undertaken to identify the material properties of calanchi and biancane. The data suggest: (a) biancane tend to develop in very fine sediments, such as silty clays with a very high clay content (65–70%); (b) calanchi tend to occur in relatively coarser sediments, such as clayey silts and sandy clayey silts having a notable sand fraction (6–18%); (c) both biancane and calanchi may develop in intermediate textures, such as silty clays and clayey silts, made up of approximately equal quantities of silt and clay; (d) no strong trend in clay mineralogy can be correlated with the landforms; the swelling phyllosilicate contents are roughly equivalent in the parent materials of biancane and calanchi; (e) pore water chemistry seems to play a very important role in the development of these landforms; the biancane have high concentrations of sodium relative to other cations (essentially calcium and magnesium) in pore water; all the analysed calanchi pore waters have low concentrations of sodium relative to divalent cations. |
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