Person: Muñoz Martín, Alfonso
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First Name
Alfonso
Last Name
Muñoz Martín
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Geodinámica, Estratigrafía y Paleontología
Area
Geodinámica Interna
Identifiers
3 results
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Item Waste dump erosional landform stability – a critical issue for mountain mining(Earth surface processes and Landforms, 2017) Martín Moreno, Cristina; Duque, José F. Martín; Ibarra, José M. Nicolau; Muñoz Martín, Alfonso; Zapico, IgnacioMining is the largest producer of solid wastes which, when released to land or into waterways, can cause harmful environmental impacts. This is mostly due to fluvial erosion, which is highly increased in mountain areas, due to abrupt slopes. We have analysed this situation at a mountain watershed (192 ha), where steep mined sites and their waste dumps are the main source of sediment in a Natural Park. This problem was tackled by building gabion check dams downstream from the mined sites. We used the DEM of Differences (DoD) method to quantify erosion and sediment yield from three waste dumps (5 ha). Their topography and substrate properties were analysed to understand the erosion problem. The sediment trapped by the check dams was quantified by Electrical Resistivity Tomography. The rainfall characteristics triggering an episode that filled the check dams with sediment in the winter of 2009-2010, were studied to confirm whether it was a case of extreme precipitation conditions. The waste dumps sediment yield (353 ± 95 Mg ha-1 yr-1) suggests severe landform instability. Analysis of topographic and substrate properties confirmed long, steep slopes combined with highly erodible materials. The check dams proved to be inefficient in controlling sediment loads, as they had only functioned for four years of 31 of existence, having trapped 13000 ± 660 m3 of sediment, whereas we estimated that the waste dumps have yielded approximately three times more sediment for the same period. Rainfall analyses showed that neither intense nor extreme conditions (return period of 25-35 years) triggered the mobilization of 37 ± 2 Mg ha-1 in a month. This study highlights the fact that mining operations in similar mountainous settings, with equivalent waste dump construction and reclamation practices, are currently unfeasible. We conclude that landform stability cannot be achieved at this site without landform changes.Item Comparison among SASW, ReMi and PS-logging techniques: Application to a railway embankment(Journal of applied geophysics, 2011) Pérez Santisteban , Itziar; García Mayordomo, Julián; Muñoz Martín, Alfonso; Carbó Gorosabel, AndrésResults obtained by SASW and PS-logging (in-hole) seismic techniques are compared with the relatively new ReMi (Refraction microtremor) method at a common site with a well-known soil profile: a recently constructed high-speed railway embankment. PS-logging is the most accurate technique in identifying the soil profile of the embankment followed by Re-Mi and SASW. Mean shear wave velocity estimations are also higher for PS-logging, followed by SASW and ReMi, while mean deviation is similar in each technique. The ReMi technique has provided very accurate results in the study of the embankment profile, which in addition to its high operability and its fast data processing, makes it a very convenient technique for extensive geotechnical surveysItem Near surface geophysical analysis of the Navamuño depression (Sierra de Béjar, Iberian Central System): Geometry, sedimentary infill and genetic implications of tectonic and glacial footprint(Geomorphology, 2018) Carrasco González, Rosa María; Turu, Valenti; Pedraza Gilsanz, Javier de; Muñoz Martín, Alfonso; Ros, Xavier; Sánchez Vizcaíno, Jesús; Ruiz Zapata, Blanca; Olaiz Campos, Antonio José; Herrero-Simon, RamónThe geometric and genetic characterization of the Navamuño depression peatland system (Iberian Central System) is presented here using results from a geophysical survey. This depression is a ~30 ha pseudo-endorheic flat basin over granitic bedrock. Three geophysical techniques were used to map the subsurface geology, and identify and describe the infill sequence: shallow seismic refraction (SR), magnetic resonance sounding (MRS) and electrical resistivity measurements (VES and ERT). The three main geoelectrical layers (G1, G2, G3) identified in previous research, have also been identified in the present work. Using the data obtained in this new research we have been able to analyse these three geological layers in detail and reinterpret them. They can be grouped genetically into two sedimentary units: an ancient sedimentary body (G3), of unknown age and type, beneath an Upper Pleistocene (G2) and Holocene (G1) sedimentary infill. The facies distribution and geometry of the Upper Pleistocene was examined using the Sequence Stratigraphy method, revealing that the Navamuño depression was an ice-dammed in the last glacial cycle resulting in glaciolacustrine sedimentation. A highly permeable sedimentary layer or regolith exists beneath the glaciolacustrine deposits. Below 40 m depth, water content falls dramatically down to a depth of 80 m where unweathered bedrock may be present. The information obtained from geophysical, geological and geomorphological studies carried out in this research, enabled us to consider various hypotheses as to the origin of this depression. According to these data, the Navamuño depression may be explained as the result of a transtensional process from the Puerto de Navamuño strike-slip fault during the reactivation of the Iberian Central System (Paleogene-Lower Miocene, Alpine orogeny), and can be correlated with the pull-apart type basins described in these areas. The neotectonic activity of this fault and the icedammed processes in these areas during the Last Glacial Cycle (MIS2) were the main causes of recent sedimentary infill in this depression.