Tropical chemical weathering of hillslope deposits and bedrock source in the Aburrá Valley, northern Colombian Andes     

Edier Aristizbal  Barry Roser  Shuichiro Yokota 《Engineering Geology》2005,81(4):389-406

Tropical chemical weathering produces extensive lateritization and formation of deep weathering profiles. Both processes are fundamental to landscape evolution and slope instability. The Aburrá Valley of the northern Colombian Andes is characterized by tropical conditions. The valley slopes are mostly covered by hillslope deposits originating from four basement rock suites which comprise contrasting granitoid, volcanic–sedimentary, ophiolitic, and metamorphic sources, respectively. Tropical chemical weathering of the Aburrá hillslope deposits and their respective bedrock were examined using X-ray fluorescence and X-ray diffraction analysis, to document and quantify their chemical weathering profiles, compositions, and mineralogical properties. The Chemical Index of Alteration (CIA), loss on ignition (LOI), and the Mobiles index (Imob) were used to quantify the degree of weathering of hillslope deposits and bedrock source. Weathering trends were analyzed using A–CN–K and A–CNK–FM diagrams. The material mantling the slopes in the Aburrá Valley records an intense weathering history. Chemical weathering is characterized by increased development of clay minerals (kaolinite, halloysite) and iron and aluminum sesquioxides. Lateritization characterizes the final stage of the weathering profiles. Concentrations of CaO, Na₂O, K₂O decrease markedly in the weathering products compared to the fresh bedrock source, whereas concentrations of Al₂O₃, Fe₂O₃, and MgO increase significantly. CIA ratios of matrix slope deposits derived from all four sources near 100, whereas those of boulder slope deposits and saprolites are lower, but exceed source rock values. Different A–CN–K weathering paths are evident for each lithotype, validating the correlation established between the hillslope deposits and their various parents. Chemical weathering indices in some samples are strongly influenced by the presence of sesquioxides, as reflected by high LOI, anomalously low CIA, and varying enrichment trends on the A–CNK–FM diagrams. Consequently, different chemical indices based on different criteria need to be combined to obtain best results, as illustrated here by the combination of LOI, CIA, and Imob. The overall results suggest that tropical conditions have dominated for a long time in the northern Colombian Andes, leading to uniformly high weathering indices in matrix slope deposits irrespective of parent lithotype. Prolonged warm and humid conditions could thus be responsible for the weathering and remobilization of extensive old hillslope deposits during the Quaternary. However, in addition to the influence of climatic factors, tectonism has also undoubtedly influenced slope evolution in the Aburrá Valley.  相似文献   

SHIA_Landslide: a distributed conceptual and physically based model to forecast the temporal and spatial occurrence of shallow landslides triggered by rainfall in tropical and mountainous basins     

Edier Aristizábal  Jaime Ignacio Vélez  Hernán Eduardo Martínez  Michel Jaboyedoff 《Landslides》2016,13(3):497-517

Landslides are a main cause of human and economic losses worldwide. For this reason, landslide hazard assessment and the capacity to predict this phenomenon have been topics of great interest within the scientific community for the implementation of early warning systems. Although several models have been proposed to forecast shallow landslides triggered by rainfall, few models have incorporated geotechnical factors into a complete hydrological model of a basin that can simulate the storage and movement of rainwater through the soil profile. These basin and full hydrological models have adopted a physically based approach. This paper develops a conceptual and physically based model called open and distributed hydrological simulation and landslides—SHIA_Landslide (Simulación HIdrológica Abierta, or SHIA, in Spanish)—that is supported by geotechnical and hydrological features occurring on a basin-wide scale in tropical and mountainous terrains. SHIA_Landslide is an original and significant contribution that offers a new perspective with which to analyse shallow landslide processes by incorporating a comprehensive distributed hydrological tank model that includes water storage in the soil coupled with a classical analysis of infinite slope stability under saturated conditions. SHIA_Landslide can be distinguished by the following: (i) its capacity to capture surface topography and effects concerning the subsurface flow; (ii) its use of digital terrain model (DTM) to establish the relationships among cells, geomorphological parameters, slope angle, direction, etc.; (iii) its continuous simulation of rainfall data over long periods and event simulations of specific storms; (iv) its consideration of the effects of horizontal and vertical flow; and (vi) its inclusion of a hydrologically complete water process that allows for hydrological calibration. SHIA_Landslide can be combined with real-time rainfall data and implemented in early warning systems.  相似文献   

Morphometrical analysis of torrential flows-prone catchments in tropical and mountainous terrain of the Colombian Andes by machine learning techniques     

Arango  María Isabel  Aristizábal  Edier  Gómez  Federico 《Natural Hazards》2021,105(1):983-1012

Natural Hazards - Assessment of susceptibility to torrential flows at the catchment scale is a necessary step for prioritising zones that can be identified by hazard and risk maps. In the Andean...  相似文献