Hydrogeology of Stromboli volcano, Aeolian Islands (Italy) from the interpretation of resistivity tomograms, self-potential, soil temperature and soil CO2 concentration measurements

International audienceTo gain a better insight of the hydrogeology and the location of the main tectonic faults of Stromboli volcano in Italy, we collected electrical resistivity measurements, soil CO2 concentrations, temperature and self-potential measurements along two profiles. These two profiles started at the village of Ginostra in the southwest part of the island. The first profile (4.8 km in length) ended up at the village of Scari in the north east part of the volcano and the second one (3.5 km in length) at Forgia Vecchia beach, in the eastern part of the island. These data were used to provide insights regarding the position of shallow aquifers and the extension of the hydrothermal system. This large-scale study is complemented by two high-resolution studies, one at the Pizzo area (near the active vents) and one at Rina Grande where flank collapse areas can be observed. The Pizzo corresponds to one of the main degassing structure of the hydrothermal system. The main degassing area is localized along a higher permeability area corresponding to the head of the gliding plane of the Rina Grande sector collapse. We found that the self-potential data reveal the position of an aquifer above the villages of Scari and San Vincenzo. We provide an estimate of the depth of this aquifer from these data. The lateral extension of the hydrothermal system (resistivity ∼15-60 ohm m) is broader than anticipated extending in the direction of the villages of Scari and San Vincenzo (in agreement with temperature data recorded in shallow wells). The lateral extension of the hydrothermal system reaches the lower third of the Rina Grande sector collapse area in the eastern part of the island. The hydrothermal body in this area is blocked by an old collapse boundary. This position of the hydrothermal body is consistent with low values of the magnetization (<2.5 A m−1) from previously published work. The presence of the hydrothermal body below Rina Grande raises questions about the mechanical stability of this flank of the edifice

Exploitation du milieu montagnard dans le Moustérien final : la Grotte du Noisetier à Fréchet-Aure (Pyrénées centrales françaises)

Characterized by marked climatic contrasts and important differences in altitude, the mountain environment is generally regarded as constraining for Paleolithic hunter-gatherers groups. The Mousterian site of Grotte du Noisetier is exceptional within the framework of the Pyrenees by its altitude and its settlement in the middle of the chain. It offers the opportunity to wonder about the reasons having led the Neanderthal groups to attend this a priori difficult context. The traditional interpretation of the site as a hunting-camp related to the exploitation of mountain ungulates is questioned. The taphonomic study particularly shows that the Izard remains were mainly accumulated by bearded vulture and that the most frequently hunted species by the human groups is the Red Deer, which is not dependent of the mountain environment at all. The Neanderthal presence cannot be explained either by the exploitation of specific mineral resources. In the current state of research, only hypothesis can be proposed to explain the Mousterian occupation of Grotte du Noisetier: it could be in particular a temporary residence site or a stopping place during displacements towards the southern side of the Pyrenees.Caractérisé par des contrastes climatiques marqués et par des dénivelés importants, le milieu montagnard est généralement considéré comme contraignant pour les groupes de chasseurs-collecteurs paléolithiques. Le site moustérien de la Grotte du Noisetier, exceptionnel dans le cadre des Pyrénées par son altitude et son implantation au coeur de la chaîne, offre l'opportunité de s'interroger sur les raisons ayant poussé les groupes néandertaliens à fréquenter ce contexte a priori difficile. L'interprétation traditionnelle du site comme halte de chasse liée à l'exploitation des ongulés de montagne est remise en question. L'étude taphonomique montre notamment que les restes d'Isard ont majoritairement été accumulés par le Gypaète barbu et que la principale espèce chassée par les groupes humains est le Cerf, aucunement inféodé au milieu montagnard. La présence néandertalienne ne peut non plus être expliquée par l'exploitation de ressources minérales spécifiques. En l'état actuel des recherches, seules des hypothèses peuvent être proposées pour expliquer l'occupation moustérienne de la Grotte du Noisetier: il pourrait s'agir notamment d'un site d'habitat temporaire ou d'un site d'étape lors de déplacements vers le versant sud des Pyrénées

Hydrogeology of Stromboli volcano, Aeolian Islands (Italy) from the interpretation of resistivity tomograms, self-potential, soil temperature and soil CO2 concentration measurements

To gain a better insight of the hydrogeology and the location of the main tectonic faults of Stromboli volcano in Italy, we collected electrical resistivity measurements, soil CO2 concentrations, temperature and self-potential measurements along two profiles. These two profiles started at the village of Ginostra in the southwest part of the island. The first profile (4.8 km in length) ended up at the village of Scari in the north east part of the volcano and the second one (3.5 km in length) at Forgia Vecchia beach, in the eastern part of the island. These data were used to provide insights regarding the position of shallow aquifers and the extension of the hydrothermal system. This large-scale study is complemented by two high-resolution studies, one at the Pizzo area (near the active vents) and one at Rina Grande where flank collapse areas can be observed. The Pizzo corresponds to one of the main degassing structure of the hydrothermal system. The main degassing area is localized along a higher permeability area corresponding to the head of the gliding plane of the Rina Grande sector collapse. We found that the self-potential data reveal the position of an aquifer above the villages of Scari and San Vincenzo. We provide an estimate of the depth of this aquifer from these data. The lateral extension of the hydrothermal system (resistivity ∼15–60 ohm m) is broader than anticipated extending in the direction of the villages of Scari and San Vincenzo (in agreement with temperature data recorded in shallow wells). The lateral extension of the hydrothermal system reaches the lower third of the Rina Grande sector collapse area in the eastern part of the island. The hydrothermal body in this area is blocked by an old collapse boundary. This position of the hydrothermal body is consistent with low values of the magnetization (<2.5 A m−1) from previously published work. The presence of the hydrothermal body below Rina Grande raises questions about the mechanical stability of this flank of the edifice