Alteración de las biotitas y biotitas clorizadas de la granodiorita de Collserola (Barcelona)

Se estudia la alteración natural experimentada por las biotitas y biotitas cloritizadas de la granodiorita de la Serra de Collcerola (Barcelona), bajo clima mediterráneo. Se muestrearon nueve perfiles, separándose  magnéticamente las biotitas de la fracción arena, analizándose químicamente (elementos totales), por difractometría de R.X. y microscopia electrónica de barrido. También se estudiaron con el microscopio petrográfico láminas delgadas de muestras no perturbadas. Las biotitas evolucionan  progresivamente primero a interestratificados biotita-vermiculita y después a vermiculita, apreciándose una tendencia a la esmectización, sugiriendo que las condiciones medioambitentales en las que se ha producido la alteración son muy similares a las actuales. La fase clorita procedente de las biotitas cloritizadas permanece inalterada en dicho medi

Characterising rainfall regimes in relation to recharge of the Sierra de Gador-Campo de Dalias aquifer system (S-E Spain)

This paper demonstrates the use of the deuterium excess parameter to distinguish between origin of precipitation in the Mediterranean basin. Isotope signatures in precipitation from the GNIP network around the Mediterranean basin and literature data are combined with isotopic data from aquifers in south east Spain to explain the typology of the precipitation events dominating recharge. Although precipitation from Atlantic origin (d-excess = 10‰) occurs more frequently in the western Mediterranean basin, the quantities in each event are generally moderate to low. Important rainfall events generally have Mediterranean origin (d-excess=15‰). The total precipitation in Gibraltar is a mixture between precipitation from both origins (d-excess in Gibraltar = 12.39‰). However, with increasing volume of the storms the Mediterranean character dominates. These heavier storms contribute mainly to recharge, as illustrated by the d-excess of 13.8‰ in deep groundwater of the Campo de Dalias (Almeria province). One of the challenges to meet ever-growing water demands is to increase recharge from events with a low return period yielding intermediate quantities per event, but forming the bulk of the annual precipitation.Cet article met en avant le paramètre «excès en deutérium» dans la détermination de l’origine des précipitations dans le bassin méditerranéen. Afin d’expliquer la nature des précipitations qui dominent la recharge de l’aquifère, nous avons combiné les signatures isotopiques fournies par le réseau GNIP avec les données de la littérature ainsi que des teneurs isotopiques provenant d’aquifères du sud-est de l’Espagne. Dans la partie ouest du bassin méditerranéen les précipitations provenant de l’Atlantique (excès en d. = 10‰) sont fréquentes mais celles d’origine méditerranéenne (excès en d. = 15‰) possèdent des volumes mensuels plus importants. La teneur isotopique des précipitations totales à Gibraltar indique une origine géographique mixte des pluies (excès en d. à Gibraltar = 12,39 ‰). Plus les volumes mensuels de pluie sont élevés plus le caractère méditerranéen s’affirme. Ces fortes précipitations contribuent principalement à la recharge, en effet l’excès en deutérium des nappes profondes du Campo de Dalias (province d’Almeria) correspond à 13,8 ‰. L’un des défis rencontrés pour satisfaire la demande croissante d’eau consiste à accroître la recharge à partir de précipitations présentant une faible période de retour et produisant des quantités moyennes de pluie par événement, mais qui constituent la majeure partie des précipitations annuelles

Estación Experimental "El Cautivo" (Desierto de Tabernas, Almería)

En: La Red de Estaciones Experimentales de Seguimiento y Evaluación de la Desertificación (RESEL) . Actividades y Resultados 1995-2004. Dirección General para la Biodiversidad, Ministerio de Medio Ambiente, MadridEl Área Experimental El Cautivo es una instalación permanente, mantenida y gestionada por el Departamento de Desertificación y Geoecología de la Estación Experimental de Zonas Aridas (EEZA) del CSIC, en Almería. El Cautivo inició su andadura en 1990 en el marco del proyecto “Erosión por acarcavamiento en medio semiárido: causas, evolución y restauración” (del Plan Nacional de Ciencia y Tecnología), y ha funcionado sin interrupción desde entonces asociada a otros proyectos de investigación. El Cautivo se escogió por ser una de las áreas del desierto de Tabernas en donde los procesos geomorfológicos parecen ser especialmente activos, enmarcados por el clima más árido de Europa que le confieren características geoecológicas muy especiales. Además, las áreas intensamente acarcavadas, conocidas como malpaís o badlands en inglés, son consideradas como laboratorios naturales que ofrecen en miniatura y en intervalos de tiempo cortos muchas de las formas y procesos erosivos de los paisajes fluviales.El trabajo presentado en este capítulo ha sido financiado total o parcialmente por los siguientes proyectos de investigación: 1) Erosión por acarcavamiento en medio semiárido: causas, evolución y restauración (NAT89-1072-C06-02), 2) DESERMA (AMB93-0844-C06-01), 3-4-5) MEDALUS I, II y III (EPOC-CT90-0014-SMA; EV5V-0128; ENV4-CT95-0118), 6) PROHIDRADE (AMB95-0986-C02-01), 7) EPOHIDRO (HID98-1056-C02-01), 8) PROHISEM (REN2001-2268-C02-01/HID), 9) GEORANGE (CE EVK2-2000-22089, CSIC ENVIR/992/0630), 10) ECONEXUS (REN2000-1513 GLO) y 11) PECOS (REN2003 - 04570/ GLO).Peer reviewe

The potential of permanent gullies in Europe as geomorphosites

Geotourism is a useful way to educate societies in the field of geomorphology and natural hazards. Geosites, including geomorphosites, represent the basis for the development of this type of tourism. This study describes twelve representative gully regions within nine European countries. The characteristics of 42 permanent gullies, gully systems and badland landscapes are presented and a geotouristic assessment of these gullies was made, based on scientific, educational, functional and touristic indicators. This assessment demonstrates a large difference between the selected gully sites, particularly with regard to functional and tourist values. The geotouristic potential of gullies is the highest in Italy and Spain and the lowest in Romania and Latvia. In some countries, permanent gullies are not regarded as geotouristic attractions at all, while in others they constitute a significant element of their tourism development strategy. Based on the analysis of scientific values of the gully sites, educational lessons to be learned were identified that are mainly related to i) gullies as a geological window, ii) present-day geomorphological processes, and iii) stages of historical gully erosion reflecting past human-environment interactions. These must be part of a broader strategy for the development of geotourism in gully regions. Gullies are potential geosites within existing or planned geoparks. Values of gullies for other forms of tourism (active, cultural, nature), should be also emphasized

Relationship of Weather Types on the Seasonal and Spatial Variability of Rainfall, Runoff, and Sediment Yield in the Western Mediterranean Basin

Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations

Hydrological consequences of soil surface type and condition

Extensive semi-arid areas over mica schist in SE Spain have soils with a sandy loam texture, a poorly developed structure, a relatively high infiltrability and a quite high saturated hydraulic conductivity. Under non-tillage land use, a stony pavements armours the soil surface and is responsible for high infiltration, low runoff and almost negligible erosion. However, when this stony pavement is absent, and no plant cover is present, i.e. in tilled soils, this soil is very vulnerable to surface crusting and erosion. With the aim to ascertain the formation stages of this stony pavement as well as to know its hydrologic and geomorphologic behaviour, an experimental study has been carried out in a runoff plot under simulated rainfall. A laser micro-relief meter has been used to characterise the spatial distribution erosion-sedimentation patterns during the experiments, and soil micromorphology to characterise stony pavements and underlying sieving crusts. In the first stage of a rainfall event after the land has been tilled, runoff and erosion are very reduced because the newly created structure absorbs most of the water and the energy of raindrops progressively destroys clods, seals the surface, detaches and transports downslope most of the fine earth. In the subsequent stage, some minutes after the rainfall started, a physical surface crust develops, and runoff and erosion progressively increase. As rainfall continues, in a third stage, the progressive removal of fine particles from the surface leaves a residue of rock fragments and runoff and erosion decrease due to both an increase in infiltration and the armouring effect of the stony pavement.Peer reviewe

Hydrofobicity phenomena in semi-arid Mediterranean soils: hydrological implications for an experimental small catchment in SE Spain

[ES] Las elevadas heterogeneidades de los regímenes de precipitación y de las propiedades edáficas que caracterizan a los ambientes semiáridos propician la aparición de complejos teselares de vegetación que pueden llegar a tener repercusiones hidro-geomorfodinámicas a diferentes escalas. A su vez el fenómeno de hidrofobia puede adquirir una gran relevancia en estos ambientes siendo la vegetación la principal fuente de aporte de compuestos hidrofóbicos. El presente trabajo pone de manifiesto la existencia de suelos hidrofóbicos en un ambiente semiárido del SE ibérico, así como el papel que desempeñan la vegetación, la textura del suelo y las letrinas de conejos en la aparición del fenómeno. Para demostrarlo se ha realizado una aproximación a diferentes escalas (medidas de hidrofobia puntual, simulaciones de lluvia en parcelas de 0.24 m2 y medidas de escorrentía bajo condiciones de lluvia naturales en parcelas de 20 m2). Se discuten las repercusiones que la repelencia puede tener a escala de cuenca y las implicaciones en los flujos hídricos y dinámica de sedimentos.[EN] Semiarid environments are characterised by the high variability of rainfall and the spatial heterogeneity of soil surface properties. These conditions favour the formation of sparse vegetation mosaics constituted by cells of plant patches and bare ground, that behave like sources and sinks of water and sediment fluxes. In turn, in these environments, the hydrofobicity phenomena may reach a great relevance, being the vegetation the main source of hydrophobic compounds. The present work shows the existence of water repellent soils in a semiarid environment in SE Spain and studies the role played by the vegetation, the soil properties and the latrines of rabbits in soil hydrophobicity generation. To demonstrate it, an approach at different scales (point hydrophobicity measurements, rain simulations in 0.24 m2 plots and runoff data from 20 m2 plots in natural rainfall events) has been carried out. The impacts of hydrophobicity at hillslope and catchment scale as well as and the implications in the hydrological responses are discussed.Peer reviewe

Meteorización y erosión en el subdesierto de Tabernas

[EN]The largest badlands in SE Spain, within the Tabernas sub-desert (Almería, Spain) is a mosaic of physiographic units concentrating most of the water erosion features of fluvial landscapes, specially those from arid regions. A Mediterranean semiarid climate in its driest end, along a main lithology on gypsum-calcaric mudstones, all explain the large variability of this landscape. Though the local geomorphology might suggest large erosion rates, the special climatic conditions of the area, with scarce rainfall events usually of low magnitude and intensity, restrict soil erosion. In this chapter the main geomorphic processes which have shaped the area are reviewed: from weathering, to regolith and soil formation, along with the indispensable role played by plant cover and its co-evolution with erosion.[ES]El área acarcavada, o malpaís, de mayor extensión del sudeste peninsular, en el sub-desierto de Tabernas, Almería, es un mosaico de teselas en donde se encuentran concentradas muchas de las formas de erosión de la mayoría de paisajes fluviales, y muy en especial los de zonas áridas. Un clima Mediterráneo semiárido, cercano a su extremo más árido, y una particular litología sobre una alternancia de margas yesíferas y calcarenitas explican la enorme variedad de geoformas de este paisaje. Si bien la geomorfología de la zona sugiere elevadas tasas de erosión, las particulares condiciones climáticas, con escasez de eventos de elevada intensidad y/o magnitud impiden que la erosión sea elevada. Se explican sucintamente los principales procesos geomorfológicos que han configurado este malpaís: desde la meteorización de la principal roca madre, la marga yesífera, pasando por la formación de regolitos, suelos y sus costras superficiales y un conjunto muy particular de comunidades vegetales que conviven con los procesos erosivos y las peculiares condiciones climáticas, los grupos de factores ecológicos más importantes y típicos de la zona.Peer reviewe

Organic wastes as amendments for limestone quarry restoration in semiarid environments

En: 1st Spanish National Conference on Advances in Materials Recycling and Eco – Energy Madrid, 12-13 November 2009.-- Editors: F. A. López, F. Puertas, F. J. Alguacil and A. Guerrero.-- 3 pages, 1 figure, 1 table.An experimental soil restoration project started in 2008 in a calcareous rock quarry in SE Spain, under Mediterranean semiarid conditions, on two different substrates (marl and topsoil). The substrates were amended with two different organic wastes: a sewage sludge and a compost. Two different mulches, mineral and organic, to mitigate soil water losses, were also tested. Three perennial species from nursery (Stipa tenacissima, Antyllis terniflora and Anthyllis cytisoides) were planted in subplots within every one of 16 experimental plots. A drip irrigation system was implemented to provide support water to every seedling under critical soil water conditions during the first months after plantation. The first results show an average survival rate of 73% in the replanted area. Survival was higher in the plots on marl than in the plots on topsoil, where the role of spontaneous vegetation might have played a negative role. A vigor index which considered plant height, width and number of leaves, has revealed that Stipa tenacissima reaches the highest vigor average value, followed in decreasing order by Anthyllis cytisoides and Anthyllis terniflora. However, when comparing the different treatments, the highest plant vigor corresponds to Anthyllis cytisoides in plots which combine the use of organic amendments and mineral mulch. Statistical GLM analyses indicate the significant role of support irrigation, organic amendments and mulches (in this order) for vegetation establishment and growth in this semiarid environment.Acknowledgements to HOLCIM ESPAÑA SA for financial support.Peer reviewe