The lebanese landscape is characterized by karstic mountain chains (Mount-Lebanon and Anti-Lebanon) with a variety of surface karstic forms as well as endokarstic network systems. Karst landforms covers up to 60% of the lebanese territory. Several questions related to the morphogenesis and evolution of landscapes, espacially coastal valleys remain unsolved. Whereas geomorphic indicators are rare on the surface due to urban pressure and topgraphic constraints, we used sub-surface geomorphologic indicators revealed from the speleogenesis study of caves. Subsusrface karst network systems are an alternative mean to address these constraints and reconstitute the morphogenesis stages of the coastal valleys' landscape. Morphogeneitic and environmental reconstitution are based on both geomorphoic indiators of underground networks and on the sediments (clastic and speleothems) in caves. The PhD research focuses on "the contribution of endokarst networks in reconstituting past environments and morphogenestic phases of coastal valleys of Mount-Lebanon”. Two valleys located in the central part of Mount-Lebanon, are chosen for this study: i) the valley of Nahr el-Kelb with a study focused on Jeita cave network system, and ii) the Antelias valley two cave were selected in this sector, Kanaan cave (162 m long) and Kassarat Nabay cave network system (4,6 km long). The first objective of the study are: i) to reconstitute the stages of the karst system related with the downcutting of the Mediterranean hydrographic network (Antelias and Kelb river). The palaeogeographical framework is based on the geomorphological approach applied in the caves of Kanaan, of Ksarat-Nabay and Jeita. It implements the mapping process applied on the underground systems and analyses of the stages of cave evolution. The second objective is to understand the environmental changes in this region related to climate variations and human settlement. The study (detrital) is based on a detailed analysis (morphoscopic, morphometric, mineralogical, and magnetic color) of sediements in cave systems.
