La Isla de Fuerteventura se sitúa en el borde oriental del Archipiélago de Canarias, a sólo 100 km del continente africano. Presenta un relieve topográfico relativamente suave respecto a las otras islas del Archipiélago, lo que unido a su proximidad a la costa del Sahara explican el carácter árido del clima imperante. El sector estudiado se sitúa en la parte central de la Isla y abarca el Macizo de Betancuria y la Depresión Central. A partir de la distribución de las unidades geológicas e hidrogeológicas más importantes se ha dividido en dos dominios principales: un Dominio Occidental, constituido por rocas volcánicas e intrusivas del Complejo Basal (Cretácico Superior - Mioceno Inferior) y un Dominio Oriental, compuesto por lavas del Edificio Gran Tarajal (Mioceno) y por depósitos volcánicos (Pleistoceno-Holoceno) que conforman el Malpaís.En el Dominio Occidental las aguas subterráneas presentan un aumento de la salinidad con la profundidad. Se diferencia una Unidad Superior, que contiene aguas de menor conductividad eléctrica (2.5-5.5 mS/cm) y temperaturas que varían entre los 18 y los 25 ºC, y una Unidad Inferior, compuesta por aguas de mayor conductividad eléctrica (5.5-24 mS/cm) y temperaturas variables entre los 25 y 30 ºC. Las aguas de la Unidad Superior son del tipo clorurado-sódico con una alcalinidad moderada y bajos contenidos de sulfato y sílice. La concentración de nitrato es variable de un punto a otro, pero en la mayoría de los casos se sospecha una componente antrópica asociada a usos agropecuarios. Las aguas más salinas de la Unidad Inferior son de tipo clorurado-sulfatado-sódico. Los contenidos de sílice son altos y los contenidos de nitrato están ausentes. La elevada salinidad en las aguas de la Unidad Superior responde principalmente al efecto de la aridez climática y localmente a efectos puntuales de retornos de riego. A partir de la modelación hidrogeoquímica realizada con el programa PHREEQC se deduce que la aridez climática tiene su efecto en una mayor concentración del agua de lluvia como consecuencia de la evaporación. En menor medida existe una aportación debido a la interacción agua-roca que implica una aportación de sodio como consecuencia de la alteración de plagioclasas. No obstante, para las muestras de la Unidad Inferior es necesario considerar otros orígenes para la salinidad. A partir de la interpretación de la relación rCl/rBr, del estudio de los isótopos del agua (18O y deuterio), de las relaciones iónicas y de la modelación hidrogeoquímica se ha deducido una salinidad debido a la mezcla con agua marina. Esta correspondería a agua marina relicta presente en las rocas intrusivas del Complejo Basal. La menor permeabilidad que presentan las unidades intrusivas explicaría la existencia de agua de origen marino por sobre el nivel del mar. Estas aguas también presentan contenidos elevados de sulfatos los cuales tienen un origen distinto, asociado a la disolución de sulfatos de origen ígneo. Las aguas de menor mineralización reconocidas en el Dominio Oriental son de composición clorurado-sódica, con valores de las relaciones iónicas más próximos a los valores de la precipitación. Los valores de las relaciones iónicas de estas aguas se aproximan más a los valores del agua de lluvia respecto a las aguas de la Unidad Superior, lo que se atribuye a la menor solubilidad de los materiales que componen las lavas del Malpaís. A partir de la integración del estudio de la piezometría, de la interpretación de los análisis químicos e isotópicos de las aguas, del análisis de perfiles de temperatura y conductividad eléctrica en sondeos y de la interpretación de la distribución de las unidades geológicas en el subsuelo se ha establecido un modelo conceptual de funcionamiento hidrogeológico del acuífero. / The island of Fuerteventura es placed in the eastern limit of the Canarian Archipelago, only 100 km far from the African Continent. It has a relatively smooth topographic relief when compared to the other islands of the Archipelago. This and the closeness to the Sahara coast explain the dominantly arid climate. The study area is in the central part of the Island and comprises a large part of the Massif of Betancuria and the Central Depression. Following the distribution of the most important geological and hydrogeological Units, the study area has been divided in two main subareas: a western subarea formed by volcanic and intrusive rocks of the Basal Complex (Upper Cretaceous-Lower Miocene) and an eastern subarea formed by lavas of the Gran Tarajal Edifice (Miocene) and volcanic deposits (Pleistocene-Holocene) which form the Malpais (badlands).In the western subarea groundwaters are characterised by an increasing salinity with depth. Thus, it is possible to differentiate an Upper Unit, containing waters of lower electrical conductivity (2.5 to 5.5 mS/cm) and temperatures between 18 and 25ºC, and a Lower Unit, with groundwaters with a higher electrical conductivity (5.5 to 24 mS/cm) and temperatures between 25 and 30ºC. Groundwaters from the Upper Unit are of the sodium-chloride type with generally a moderate alkalinity and low sulphate and silica contents. Nitrate contents of these waters varies from point to point, but in most cases an anthropic component is suspected, which is associated to farming activities. The more saline groundwaters of the Lower Unit are of the sodium-chloride-sulphate type, except for some one which is more diluted as a consequence of the mixture of waters from the Upper and Lower Units inside the boreholes.The high salinity of groundwater from the Upper Unit is mainly the result of the island's climatic aridity, and locally to point effects of excess irigation water. From the hydrochemical modelling carried out with the code PHREEQC it is deduced that climatic aridity produces an intense evaporation concentration of rainfall. To a lesser extent there is a contribution due to rock-water interaction, which corresponds mostly to plagioclase weathering. However, the more saline waters in the Lower Unit have to be explained by means of other salinity origins. From the interpretation of the rCl/rBr ratio, the study of water isotopes (180 and deuterium), the most important ionic ratios and chemical modelling, the salinity can be linked to the admixture with sea water. This sea water seem to be relict and it is found in the intrusive rocks of the Basal Complex. The smaller permeability of the intrusive units may explain the presence of seawater above present sea level, as remnants of moments in which the ocean was relatively at a higher elevation. These waters also present high sulphate contents. The sulphate has a different origin, which is associated to the dissolution of sulphates of igneous origin. Groundwaters of a lower salinity found in the eastern subarea represent recharge water and also have a marked sodium-chloride composition, with ionic ratios which are closer to those of precipitation. Generally the ionic rations of these waters are closer to those of rainfall than the samples from the Upper Unit. This is explained by the faster turnover time and low solubility of the materials of the Malpais recent lavas.By integrating the piezometric study, the interpretation of water chemical and isotopic analyses, the analysis of temperature and electrical conductivity borehole logs, and the interpretation of underground distribution of geological units, a conceptual model of the aquifer hydrogeological functioning has been established, which explains reasonably well the results commented above.

This work is studying the development and actual situation of landscape in Canary Islands with focusing on islands of Gran Canaria and Fuerteventura. The specific geologic and climatic conditions with huge impact of human activity and tourism started to change the landscape radically. First part contains analysis of the geographical, geological and nature conditions of all seven Canary Islands and the process of colonisation through the boom of tourism and its impact to the landscape. Second part of the study is focused on measures how to preserve the original character of the landscape in coordination with development of tourism and economic activity. The work also contains an application of the assessment method of larger areas created by Ing. Roman Bukáček.

The volcanic origin of the Canarian Archipelago widely determines the landscape of these islands. Partially in coastal near areas the volcanic rocks are covered by dune fields. The eastern Canary Islands show the largest areas of sand deposits. On northern Fuerteventura sandpits and deep incised gully systems allow broader insight into generations of these archives. The dune material originates from the shallow shelf. Hence, the mineral composition is dominated by calcite and aragonite. The outcrops show the layering of several generations of biogenic carbonate sands which are separated by palaeosurfaces. These surfaces suggest soil-forming processes by their (often) reddish colour. Generally, the occurrence of several palaeosurfaces promises a high potential of those Quaternary dune archives on northern Fuerteventura. Former studies focussed on just few quarries being situated in close distances. Differing formation concepts and contradicting chronologies (Middle to Late Pleistocene versus Late Pleistocene) suggest the need for further investigation of landward palaeo dune sections, resulting in a DFG funded project with regard to palaeo dune sequences within the catchments of two Barrancos on northern Fuerteventura. Firstly, the project called for defining representative sections of the two catchments for the purpose of working out a correlation and deducing a standard profile, both should be based on stratigraphic findings. IRSL dating shall contribute to finally establishing a chrono-stratigraphy. Besides the carbonate sands, the dune archives are influenced by the imprint of volcanic material (tephra, lapilli, and basaltic rock) and Saharan dust. Generally, the archives’ composition and appearance raise several further questions: Are periods of surface formation dependent on reduced sand supply or on changes in climatic conditions? Which soil forming processes contribute to the characteristics of palaeosurface layers? How about the influence of Saharan dust? As dating of lava flows on northern Fuerteventura revealed Middle to Late Pleistocene ages, a further question refers to the relationship of dune formation and volcanic activity. Mainly deduced from findings in the field but also by use of grain size distribution, elemental composition, content of CaCO3, determination of Fed, measurements of rock magnetic parameters, analyses of gastropod associations, micromorphological analyses, determination of quartz content via Morphologi G3-ID measurements, XRD analyses, and IRSL dating, this thesis provides a chronostratigraphy of palaeo dune archives of northern Fuerteventura deduced from a correlation of sections close to the western coast and sections close to the eastern coast. The derived standard profile shows 15 units divided into 5 main sequences. These 5 sequences mainly differ in sand supply and accumulation, in changing humidity, and in imprint of volcanic activity. The chrono-stratigraphy dates back to about 450 ka. Generally, the archives are very site-specific, because features of a stratigraphic layer often change within close distances, depending on connectivity to erosion pathways and distance to sand sources. Micromorphological analyses indicate soil forming processes which are restricted to de- and recalcification and recrystallisation of iron and manganese. Ultimately, the palaeosurfaces are primarily dominated by the characteristics of Saharan dust (silt dominated, yellow to red in colour, containing hematite and goethite). The archives indicate a cyclicity of predominant processes, starting with I) sand accumulation, followed by II) dust accumulation and weak soil formation, leading to III) water-induced relocation. On the basis of this cyclicity a conceptual approach of the archives’ relationship to changes in sea level could be drawn. We assume highest sand supply during starting regression after sea level maxima. With dropping sea level, the distance between the studied sites and the sand source area (which are the gradually exposed shallow shelf areas) increases, leading to reduced sand accumulation. Starting transgression at the end of glacials suggests the lowest potential of sand accumulation. Furthermore, the concept is based on the assumption that with lower sea levels, more precipitation can reach the Canary Islands. Deduced from periods of lowest potential of sand accumulation in combination with periods of increased precipitation, best conditions for predominant dust accumulation and in-situ processes should be given at terminations. Generally, prevalence of palaeosurface formation is related to transgression periods. These periods are in good agreement with increased dust supply, which, in turn, seem to be affected by precession minima (according to Moreno et al., 2001). The predominance of dust accumulation and in-situ processes causes the fining of sediments, leading to reduced morphological resistance and, finally, water-induced relocation. Ultimately, site-specific sand availability seems to determine whether surfaces are exposed for longer durations, whereas the availability of precipitation (and dust) suggests determining the intensity of surface formation. The studied sections indicate a strong relationship to local volcanic activity because lava flows are able to cut off sand pathways and cover former sand source areas. In combination with dated lava flows the findings point to three different periods of volcanic activity which ceased the sand supply gradually. A first period around 180-170 ka, a next period around 135 ka, and a third period after 100 ka but latest around 50 ka which, finally, completely stopped the sand supply. Regarding the northern part of Fuerteventura, the latest period has so far not been described.