Morfologie carsiche della Cirenaica (Nord-Est Libia)

A campaign of investigations has started in 2007 aiming at studying the karst morphologies of the Jabal Al Akhdar (Green Mountains). Such a campaign is within a research agreement stipulated between the Earth Sciences Department of Garyounis University of Benghazi, Libya and the HyIblean Speleo-hydrogeological Research Centre of Ragusa, Italy. Among the objectives of the project there are: that more general concerning the formulation of a speleogenetic model consistent with the geodynamic evolution and climate changes taken place in the tethyan-mediterranean region from the end of the Cretaceous; those with application fall-outs into the local socioeconomic framework addressing the finding out and protection of new water resources, the mapping of man altered areas, potentially at risk of instability and / or sinking because of the presence of karst voids, and the promotion and popularization of the karst geomorphological heritage which has the requirements to become a geopark enjoyed for scientific and geoturistic ends. Al Jabal Al Akhdar belt is located in the northeastern part of Libya and it consists of a prominent promontory on the southern edge of the Mediterranean coast. It is 350 km long and 100 km wide. Tectonically, this belt is an inverted basin and has been affected by the Tethyan tectonic activities since its opening during the Jurassic. Lithologic outcrops of Al Jabal Al Akhdar belt involve limited exposures of upper-Cretaceous carbonates that constitute E-W to ENE-WSW structural inliers emerged within extensive exposures of Eocene, Oligocene and, sometimes, Miocene limestones. The campaign of geospeleological investigations carried out in the 2007, 2008 and 2009 years has concerned the karst area of the coastal belt of Benghazi, Sousa and the plateau of Al Marj, Al Bayda and Dernah. The study of a series of large collapse dolines, connected with the network of conduicts draining the ground water along the coast, was started in the area of Benghazi. Still in the same area, the Lethe karst system with a large underground lake, which was the subject of a tourist fruition during the Italian colonial period, is of particular interest, even historic. In the coastal area of Sousa a significant karst outcrop, surveyed and documented, is the Brag Notta system constituted by a collapse doline and a large neighbouring lake connected hydrologically by a recent tectonic structure draining the brackish ground. In raised areas of El Beida and El Marj plateau a very interesting geomorphologic and hydrogeologic study shows some big dolines and dip shafts, inserted in the context of a typical cockpit relief, while in the plateau of Dernah the exploration of a complex labyrinthine cave has allowed also the discovery of paleontologic and archaeological finds. Speleological explorations and geological investigations of the above mentioned karst areas should be continued in the future compatibly with the return to a normal peaceful condition in the whole area of the Country. Riassunto Si espongono i primi risultati di una serie di campagne di studi sulle morfologie carsiche del Jabal Al Akhdar (Montagne Verdi), campagne iniziate nel 2007 e condotte dal Centro Ibleo di Ricerche Speleo-Idrogeologiche di Ragusa e dal Dipartimento di Scienze della Terra dell’Università Garyounis di Bengasi. Sono brevemente illustrati la geologia e la struttura dell’area carsica della piana di Bengasi, dell’area carsica fra Ras Hilal e Derna, le aree carsiche di El Marj e El Beida e la fascia costiera di Sousa e il plateau di Cirene.