Artículos (GIGAI)

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  • Ítem
    Erosional and depositional features produced by a convulsive event, San Carlos, Colombia, September 21, 1990
    (Springer Verlag, 1992-04-01) Hermelin Arbaux, Michel; Mejía, Oscar; Velásquez, Elkin; Universidad EAFIT. Departamento de Geología; Michel Hermelin Arbaux (; Geología Ambiental e Ingeniería Sísmica (GIGAI)
    Le bassin supdricur de la riviC:re San Carlos, situd sur le flanc est de la Cordill~re Centrale de Colombie, a dtd aft'ectd par un << ~vdnemertt convulsif ,, le 2I septembre 1990. Une averse de 208 ram. ~,ans 6.quiva/enl historique dans ia zone, a cau.,,6 lu mort de 20 personnes et d'importants ddgfits. Plus de cent couldcs boueuses se sont produites sur les versants les plus 61evds et les plus inclinds, quelle que soil la nature du sol. Dans les zones moyennes du bassin Its lits des torrents ont did dlurgis et approfondis p~u" le creusement d'anciens ddp6ts torrentiels et de versants et de la granodiorite mdtdorisde. Une grande quantit6, de matdriau a dt~. drod~e, y compris des blocs d'un diametre atteignant 8 m. Les d@6ts montrent une diffdrenciation classique : les blocs accumules sur la pattie haute, les sables sur le cours moyen, et les argiles ont dr6. transport6es jusqu'au rdservoir de Punchin'a, environ 20 km en aval. Une couche de cendres volcaniques qui recouvre les ddp6ts torrentiels anciens montre des associations mindralogiques qui pet, vent etre corrdldes avec d'autres cendres trouvdes plus 5, I'est, dont I'&ge radiomdtrique cst de I0.500 ans BP environ
  • Ítem
    Valle de Aburrá: ¿Quo vadis?
    (Universidad Nacional de Colombia, 2007-08-31) Hermelin Arbaux, Michel; Universidad EAFIT. Departamento de Geología; Michel Hermelin Arbaux (; Geología Ambiental e Ingeniería Sísmica (GIGAI)
    This paper intents a brief description of the evolution that characterised natural risk prevention in the area surrounding the city of Medellin, Colombia, called the Aburra Valley. Both the lithological and structural composition of the Valle and its topographic and climatic conditions contribute to the abundance of destructive natural phenomena as earthquakes, slope movements, flash floods and, in a lower proportion, to floods. The population increase, which reaches now 3.5 millions inhabitants and the frequent occupation of sites exposed to natural hazards have resulted in numerous disasters. At present two entities called SIMPAD and DAPARD work on risk prevention, on city and department scale respectively. The amount of knowledge about physical environment is considered to be insufficient, together with regulations which should direct land use in accordance to restrictions related to natural hazards. Several seminars on this topic have already been carried out and the organisers of the present one, destined to commemorate the twentieth anniversary of the Villa Tina disaster, should make the decision to meet each two years. Furthermore, the creation of a permanent commission dedicated to study past events, to foster information broadcasting and to seek a better knowledge of the Aburra Valley, should be considered.
  • Ítem
    Factors controlling sediment yield in a major South American drainage basin: the Magdalena River, Colombia
    (Elsevier, 2005-05-04) Restrepo, Juan D.; Kjerfve, Bjo¨rn; Hermelin Arbaux, Michel; Restrepo, Juan C.; Universidad EAFIT. Departamento de Geología; Michel Hermelin Arbaux (; Geología Ambiental e Ingeniería Sísmica (GIGAI)
    The Magdalena River, a major fluvial system draining most of the Colombian Andes, has the highest sediment yield of any medium- sized or large river in South America. We examined sediment yield and its response to control variables in the Magdalena drainage basin based on a multi-year dataset of sediment loads from 32 tributary catchments. Various morphometric, hydrologic, and climatic variables were estimated in order to understand and predict the variation in sediment yield. Sediment yield varies from 128 to 2200 t kmK2 yrK1 for catchments ranging from 320 to 59,600 km2. The mean sediment yield for 32 sub-basins within the Magdalena basin is w690 t kmK2 yrK1. Mean annual runoff is the dominant control and explains 51% of the observed variance in sediment yield. A multiple regression model, including two control variables, runoff and maximum water discharge, explains 58% of the variance. This model is efficient (MEZ0.89) and is a valuable tool for predicting total sediment yield from tributary catchments in the Magdalena basin. Multiple correlations for those basins corresponding to the upper Magdalena, middle basin, Eastern Cordillera, and catchment areas greater than 2000 km2, explain 75, 77, 89, and 78% of the variance in sediment yield, respectively. Although more variance is explained when dataset are grouped into categories, the models are less efficient (ME!0.72). Within the spatially distributed models, six catchment variables predict sediment yield, including runoff, precipitation, precipitation peakedness, mean elevation, mean water discharge, and relief. These estimators are related to the relative importance of climate and weathering, hillslope erosion, and fluvial transport processes. Time series analysis indicates that significant increases in sediment load have occurred over 68% of the catchment area, while 31% have experienced a decreasing trend in sediment load and thus yield. Land use analysis and increasing sediment load trends indicate that erosion within the catchment has increased over the last 10–20 years.
  • Ítem
    Modelo cronoestratigráfico para el emplazamiento de los depósitos de vertiente en el Valle de Aburrá.
    (Universidad Nacional de Colombia, 2006) Rendón G., Diego Armando; Toro V., Gloria Elena; Hermelin Arbaux, Michel; Universidad EAFIT. Departamento de Geología; Diego Armando Rendón G. (; Gloria Elena Toro V. (; Michel Hermelin Arbaux (; Geología Ambiental e Ingeniería Sísmica (GIGAI)
    This paper presents new stratigraphic and chronologic data related with a widespread and complex sequence of slope deposits located at "El Poblado" sector, southeast area of the Medellín City, and Envigado County. Geomorphologic cartography, stratigraphic work in civil excavations, and fission track ages of interbedded volcanic ash deposits let us to divide the slope deposits in at least four stages: I, II, III, and IV. Such slope materials, mainly mud and debris flows, present a staircased distribution (telescopic). The oldest deposits, stages I and II, crop out on the middle and higher parts of the slope; while the younger ones, stages III and IV, show wide and nicely preserved fan shape over slope foothills. The oldest ages found in volcanic zircons (obtained around 30 m depth) reach 2.63 Ma, Early Pliocene, representing the maximum age of stage I, which lower age is approximately 1.8 Ma. Stage II has a wide thickness range, and ages between 2.0 and 0.9 Ma, Late PliocenePleistocene. Finally, behind deposits belonging to stage III, other authors report peat layers with ages beyond of the application time span of C14 method (older than 40k.a.). In addition, several basement zircons were found in the deposits, with ages between 45 and 48 Ma.
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