Geomorfologia e Geodiversità della Sierra de Grazalema (Andalusia, Spagna)

The project related to the present PhD thesis aims to provide a new characterization and interpretation of the main features related to the geomorphology and geodiversity of the Sierra de Grazalema (southwestern Andalusia, Spain). To this end, we attempted to obtain objective evidences of discrimination (morphometric characterization, parameterization of spatial variables, detailed maps, etc..), as well as to refine existing models of morphological evolution related to the karstic massifs of the study area, the Grazalema Massif and the Libar Massif. On that latter point, it was important to try to define connections between the geological and morphostructural evolution of the two Massifs and the development of the local karstic and fluvial systems. The study area is characterized by an extraordinary amount, variety and spatial distribution of morphogenetic evidences (almost exclusively) associated to a morphodynamic karstic system. New instruments of representation and innovative collection of spatial data were necessitated by this large quantity of geodiversity features, in particular through the design and implementation of a structured database related to the elements relevant to geological and geomorphological interest (Sierra de Grazalema Database). In this way we tried to reach an improved, enriched (if compared to literature data) and, above all, spatially georeferenced awareness of active processes and forms which are present in the study area. The ultimate goal of this operative process relies on the inventorying of the elements of geodiversity and on supporting it with reliable and of high representative impact reconstructions, based on a careful modeling of the geomorphological processes that have contributed to increasing its value. The preliminary in-depth analysis of bibliographic references has shown that the Serrania de Grazalema area has already been the subject of investigations related to very different fields of study. In detail, the level of knowledge relating to the geological and paleogeographic framework of this sector of the Western Betic Ranges is very well developed; on the contrary, the interpretation of the karstic landscape morphodynamics revealed to be limited and not exhaustive. For this reason, the main elements of the climatic, biogeographical and pedological framework of the area were initially tested and revised. These elements provide qualitative and quantitative data useful for the assessment of the variables that affect the current processes on karst massifs. In addition, the definition of a stratigraphical and structural outline has proved useful for the general purposes of the project, especially considering the geological and tectonic complexity of this sector belonging to the Subbetic Outer Zones (also known as Penibetic). Once defined this multidisciplinary general framework we passed to the high morphometrical detail inventorying of the meso- to macroscale exokarstic landforms of the study area. Given the significant extension of the zone (about 285 km ²), an appropriate methodology of detection was adopted to get an almost complete coverage of the massifs. In this sense, the carrying out of this task was possible by using the most recent Remote Sensing techniques or by their original application. In detail, by interpolating the thematic layers (corresponding to the GIS features designed) with a DTM of adequate resolution (10 meters), the modeling of the spatial distribution and the assessment of morphometric parameters of the sinkholes and polje (which characterize both the Grazalema and the Libar Massifs) was obtained, as well as an indirect numerical information extremely valuable to the definition of the extent of karst morphodynamics of some sectors (rates of lowering of lateral corrosional surfaces of the Sierra Libar polje, analysis of distribution of sinkholes, etc..). The parametric measurements obtained, together with the revision of literature data relating to competing factors in triggering and developing karst morphogenetical features, have been properly treated in order to produce a map of the susceptibility to surface karstification. After presenting a reasoned inventory of the main karstic caves of the area and of the related endokarstic networks, some considerations on the evolution of the massifs of the Serrania de Grazalema were put forward. As there are no absolute datings nor evidences of undisturbed Quaternary deposits in the zone, we attempted to show how, by combining literature validated data and correctly georeferenced data with some morphological evidence, the relative chronology of the most important karstic systems in the area can be reconstructed, as well as, the accurate relationships between the structural and geological evolution of the massifs and the progression of the networks of local rivers can be inferred. Finally, through the design of a proper WebGIS application (GeoDIV), developed by using Open Source software, was presented the applicability of an innovative and near-to-zero cost system to promote and manage the geodiversity of the area of the Parque Natural de la Sierra de Grazalema.