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Idrogeologia e carsismo del bacino del Fiume Frigido (Alpi Apuane)
... This difference, which is due to the recent morphotectonic evolution of the region, is what causes the prevailing groundwater flow from NE to SW and the underground capture of water by coastal basins from the adjacent tributary basins of the Serchio River [46]. The most known example of this underground piracy is that of the Frigido River basin, whose groundwater divide defines a catchment area that extends over 35% beyond the surface watershed [29,47]. ...
... Other important springs in this basin are the Cartaro-13 (0.4 m 3 /s), Renara-14 (0.2 m 3 /s) and Altagnana-15 (0.06 m 3 /s) springs (Fig. 5). Polla di Forno spring has been the subject of numerous hydrogeological studies aimed at determining the recharge area and estimating the mean flow rate [47]. It was the first Apuan spring to be monitored in flow rate for a continual period of 3 years, from 1993 to 1995 [32,66]. ...
Carbonate rocks may be considered among the most important and strategic aquifers, given their widespread and the general high quality of groundwater flowing through them. Nevertheless, the karst systems developed within such aquifers promote conditions of high vulnerability to contamination and a high variability of groundwater flow rate, thus making the management of these water resources difficult. These critical features can be accentuated in metamorphosed carbonates, because of the massive structure of the rock that favours a low density of the karst network, and a preferential flow pattern throughout well-developed karst conduits. Furthermore, these rocks are often subject to quarrying and associated risk of pollution, mainly due to the fine slurry produced during marble cutting. This chapter presents the case of the Apuan Alps (NW Tuscany, Italy), where the main hydrogeological units are represented by metamorphosed dolostones and limestones (“Grezzoni” and marble, respectively), the latter being widely quarried to produce ornamental stones, as the famous Carrara marble. High-pressure ductile deformations and the consequent metamorphism have reduced the hydraulic conductivity of bedding surface, whereas the tectonic exhumation due to low-angle extensional faults has limited the development of diffuse fracture joints. For these reasons, an important subterranean storage of water is represented by epikarst porosity (unloading fissures and solution pockets) and vadose seepage, whereas in the epiphreatic and phreatic zones, the karst conduits have a high hydraulic conductivity but a low storage capability. Large flow rates and physical-chemical and isotopic variations, both in space and time, are observed at the springs as a consequence of differentiation of groundwater flow paths and hydrodynamic conditions. The main results derived from several years of study in the region are discussed in order to underline the high complexity of aquifer systems hosted in metamorphic carbonate rocks and to emphasize that multidisciplinary studies can provide knowledge useful for managing water resources in these very complex contexts.
... Carcaraia Caratteri geologici ed evoluzione idro-morfologica Figura 1. Stralcio della Carta idrogeologica del bacino del Frigido (da: Piccini & Pranzini, 1989, modificata), con riportati gli ingressi delle principali grotte. Legenda: 1) coperture detritiche (dt), moreniche (mo) e alluvionali (al), 2) rocce carbonatiche a permeabilità alta per carsismo e fratturazione (gr = Grezzoni, m = Marmi e Marmi Dolomitici), 3) rocce carbonatiche a permeabilità media per carsismo e fratturazione (cs = Calcari Selciferi, csE = Calcari Selciferi ad Entrochi), 4) rocce silicee (d = Diaspri) a permeabilità bassa, per moderata fratturazione, o nulla; 5) rocce impermeabili (sc = Scisti Sericitici), 6) ingressi dei complessi carsici maggiori, 7) ingressi delle principali cavità a sviluppo verticale (il numero è quello del Catasto delle Grotte della Toscana), 8) spartiacque superficiali. ...
... Benché una piccola parte delle numerose cavità conosciute in questa zona (quelle catastate sono circa 130) permettano di accedere a sistemi sotterranei complessi, il totale di condotti carsici conosciuti assomma già a circa 50 km di sviluppo. Il potenziale carsificabile è il maggiore di tutte le Apuane, di poco superiore a 1600 m, limitato in basso dalla quota della Sorgente del Frigido, che da quest'area trae la maggior parte della sua alimentazione (Piccini & Pranzini, 1989;Piccini 1994-b). Questa sorgente è, con 1500 l/s di portata media, la maggiore di tutte le Apuane ed ha un regime idrogeologico che lascia prospettare l'esistenza di un da brecce dolomitiche, verso il tetto la stratificazione si fa più eviden te e compaiono filladi cloritiche lungo i giunti di strato. ...
In recent years, the exploration of large cave complexes is providing with new data concerning the geological and hydrogeologic underground setting of northern M. Tambura. Based on the present knowledge of karts, we can assert that M. Tambura present an exceptional development of caves, the total development of caves being presently about 50 km. A large part of the several surface pits are closed by rockfalls and detritus after only few meters. The caves with a development upper than 100 m are about 20, they present a mainly vertical pattern, with the significant exclusion of the deeper part of major caves. The whole endokarts system is characterized by a well developed network of vertical vadose passages, which drain the see-pages water to the present phreatic zone, whose elevation ranges from 500 to 340 m a.s.l.. At an elevation of 650-800 m, a wide abandoned phreatic network occur, extending from the Abisso Saragato to the Abisso Mani Pulite. The present drainage is toward NW and the springs are those located near Equi Terme, in the extreme North of Alpi Apuane. These drainage pattern must be inherited from a previous hydrogeologic configuration, in which a southward drainage should be difficult because the elevation of impermeable rock on the seaward side of Apuane was upper than now. Although a Northward drainage is not the most convenient in the present hydrogeo-logical setting, the past imprinting survives. A possible pathway for underground water is along the Pizzo Maggiore – Foce a Giovo transect, where the Orto di Donna syncline could be cross by deep-phreatic passages.
... Piccini & Pranzini (1989), investigating the hydrogeologic setting of the F. Frigido basin, the largest karst drainage basin in the region, attributed the predominantly south-westward underground water flow to differences in the base level, which is lower in elevation in the valleys of Versilia (200-300 m) than in the Garfagnana (500 m). Therefore, the western, maritime side of the Apuan Alps is dominated by horizontal caves, which provide mostly a drainage function in these phreatic conditions. ...
Renowned since the Roman Period for the extraction of precious marble, the Apuan Alps (northern Tuscany) are an extraordinary region of natural and cultural heritage in the Mediterranean basin and contain a large number of geosites of international and national interest. The great variety of morphologic and topographic contexts, ranging from the coastal plain of Versilia to the rugged, harsh landscape in the interior, makes this region remarkable for its peculiar geologic and geomorphologic setting. Two map sheets are appended to this paper: (1) a geomorphological map of Apuan Alps Regional Park and its immediate surroundings at a scale of 1:50,000 and (2) two thematic maps at a scale of 1:100,000 ('Neotectonic Map' and the 'Map of Selected Sites of Geomorphological Significance') and other four thematic maps at a scale of 1:200,000 that present the relief, slope aspects, drainage networks, and climatic elements of the region. The preparation of the Geomorphological Map followed the principles adopted by the National Group of Physical Geography and Geomorphology and by the National Geological Survey, Working Group for Geomorphological Cartography and was updated using the guidelines for the fieldwork and preparation of the Geomorphological Map of Italy at a scale of 1:50,000. The geomorphologic data were stored in a spatial database and managed using a GIS application (ArcGis (TM)). The high relief, complex geologic structure, and Pleistocene climate condition have deeply shaped the evolution of the Apuan landscape, which is characterized by great structural control of the landforms, an extensive and complex epigean and hypogean karst landscape, and impressive shaping by glaciers during the Late Pleistocene. In addition, gravity, frost shattering, marine action, and running water have played significant roles as active morphogenetic agents. The coastal belt has been the source of abundant valuable data regarding the Holocene coastal evolution, Finally, the present-day landscape has also been extensively shaped by a long history of anthropic activities, including agriculture, timber production, intense marble quarrying in the interior and widespread urban and productive settlements in the coastal plain.
... Geologic sketch map of Frigido Basin with the location of investigated caves (fromPiccini and Pranzini, 1989). ...
A multidisciplinary integrated approach was used to study the structural architecture influencing the circulation pattern of geother - mal fluids in the Equi Terme area (NW Alpi Apuane, Tuscany). Geological-structural surveys were carried out to define the structural setting of the area and to characterize geometries and kinematics of fault systems. Chemical (major components) and isotopic analyses (δ18O‰, δ2H‰, 3H, δ13C‰DIC, δ34S‰SO4]) were performed on thermal water and cold springs. A geophysical survey was also conducted by means of both Magnetotelluric and Electrical Resistivity Tomography methodologies, in order to gain insight into the resistivity distribution at depth and to indirectly image the subsurface structure. This multidisciplinary approach proved to be a powerful tool, since it unravels the complexity of this natural geothermal system and provides useful suggestion for reconstructing the fluid circulation outflowing at the Equi Terme thermal spring. Results pointed out how the E-W oriented fault system (the Equi Terme Fault) play a key role in controlling the thermal groundwater outflow, and the chemical-physical features of this resource. This structural lineament separates high permeability carbonate complexes (footwall), in which both shallow and deep flow paths develop, from a medium-low permeability succession (hangingwall) that contains evaporitic formations from which thermal water acquires a high salinity and a composition of the Na-Cl (Ca-SO4) type. During the uprising along the fault system, the thermal water is also affected by a mixing with shallow fresh-cold waters that lead to a strong seasonal variation in the chemical-physical properties of the thermal springs.
This paper provides an overview of international organizations who have substantive interests in the field of karst research. Details are provided of the current activities of the IGU Study Group "Environmental Changes in Karst Areas". The role of IGCP Project 299 "Geology, Climate, Hydrology and Karst Formation" is reviewed in relation to the present needs for international research and action in this field. Proposals are made for future international cooperation in karst research, specifically with reference to the establishment of an integrated monitoring network along the lines of the IGBP "geosphere-biosphere observatories" and to the establishment of a UNESCO convention for the protection of significant karst sites.
ABSTRACT The management and protection of water resources in karst envi-ronment require detailed knowledge of the aquifer system which can be obtained through a multidisciplinary approach, including not only hydrogeological/structural assessment, but also the use of tools not commonly used in hydrogeology, as the isotope ratios. In the present work some examples of isotopic applications on karst aquifers are discussed in relation to hydrogeological studies carried out in the Carrione Stream, Frigido River, and Versilia River catchments (Apuan Alps, Tuscany). In particular, during such studies the isotopic ratios 18 O / 16 O and 2 H / 1 H of the water molecule, mainly, and 13 C / 12 C of inorganic carbon in solution were used. The isotopic data, and their comparison with the hydrogeo-logical and structural-geological ones, were useful: to obtain in-formation about the hydrodynamic conditions in the aquifer; to define the recharge area of main springs; and to identify different circulation systems drained by closing springs which have similar chemistry. The obtained results confirm that in karst systems, where it is often difficult to carry out conventional hydrogeological surveys, the isotopic instruments have a fundamental role in the study of water circulation.
Studi di geomorfologia di superfi cie e ipogea, unitamente ai risultati di recenti datazioni eseguite su concrezioni di grotta, permettono di ricostruire le principali tappe evolutive dei sistemi carsici delle Alpi Apuane. Le forme più antiche possono essere fatte risalire al primo denudamento delle formazioni carbonatiche della successione apuana metamorfi ca (soprattutto marmi e dolomie), e che probabilmente risale al Pliocene Medio-Superiore. La distribuzione altimetrica dei piani freatici nei principali sistemi carsici e di alcune cavità relitte suggerisce l'esistenza di almeno tre principali fasi di sviluppo, che trovano riscontro anche in elementi morfologici del paesaggio (superfi ci a bassa pendenza o creste a sviluppo orizzontale). Le grotte più antiche, con morfologie freatiche relitte, poste intorno ai 1500 m di quota, si sono formate in un paesaggio ben diverso dall'attuale con un livello di base almeno 1000-1200 m più alto. La presenza di ciottoli di arenarie non metamorfi che nelle gallerie superiori del Complesso Carsico del M. Corchia fa propendere per un'età riferibile al Pliocene Superiore, in cui l'idrografi a superfi ciale sulle Apuane non era ancora condizionata dai bacini intramontani del Serchio e della Val di Magra. In una fase successiva, legata probabilmente ad un lungo periodo di stasi tettonica, si sono formati i piani di grandi gallerie del Corchia, posti intorno a 1100-1200 m di quota, grazie all'esistenza di un bacino chiuso che convogliava grosse quantità di acque verso questa zona. La seconda e più diffusa fase di sviluppo ha dato origine alla maggior parte delle cavità freatiche, ora situate prevalentemente tra 750 e 1000 m. Una terza fase regionale ha dato origine a sistemi paleo-freatici posizionati intorno ai 500-650 m di quota con drenaggio centrifugo. Questa terza generazione di grotte è ancora attiva sul versante garfagnino delle Apuane, mentre su quello marino, un ulteriore abbassamento del livello di base ha provocato lo spostamento delle sorgenti carsiche tra 250 e 300 m di quota. Abstract Surface and hypogean geomorphology of karst, together with the results of recent dating of speleothems, allow to infer the main evolution steps of karts systems in the Alpi Apuane. The oldest karst forms could be coeval with the fi rst denudation of metamorphic carbonate formations of Apuane succession (mainly marble and dolomite), which probably dates to Middle-Late Pliocene. The altitudinal distribution of phreatic conduits in the major karst systems and of some relict caves suggests the occurrence of at least 3 important development stages, which can be related with topographical features (low gradient surfaces or horizontal ridges). The fi rst generation of caves, which consist of relict phreatic passages located around 1500 m a.s.l., probably formed in a landscape very different from the present one, characterised by a base level about 1000-1200 m higher than now. Exotic pebbles of non-metamorphic sandstones, in the upper level of M. Corchia Karst Complex, could imply a Late Pliocene age, when surface hydrograph pattern should not be yet strongly infl uenced by the intramontane basin of Serchio and Magra River. During a further phase, probably related to a long period of uplift standstill, the planes of large conduits in the Corchia complex, located around 1100-1200 m of altitude, were formed thanks to the huge quantity of water drained from a surface closed basin. The second, and widely diffuse, development stage of karst originated the large part of palaeo-phreatic caves, now located between 750 and 1000 m a.s.l. on a large part of Apuane. A third regional phase is responsible of the formation of phreatic systems at 500-650 m a.s.l., with centrifugal drainage. This third generation of cave is still active in the Garfagnana side, while on the seaward side, a further lowering of base level is the cause of the present location of karst spring at 250-300 m of altitude.
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