Abstract A strong and potentially dangerous decreasing trend in the level of water in Vrana Lake over the last three decades was analysed. This freshwater lake is a unique karst hydrology feature located on the small Adriatic island of Cres (405.71 km 2 ), which is entirely composed of carbonate rocks. The lake is situated in a large cryptodepression and its base reaches a depth of 61.3 m below mean sea-level. The lake is a complex hydrological–hydrogeological system with an average water volume of c. 220 × 10 6 m 3 . The larger geographical region has been affected by an increase in air temperature over the last c. 40 years. This exceptionally clean freshwater lake is the only source of potable water for the whole Cres archipelago. A dangerous drop in the water level of the lake started in 1983. This decreasing trend is driven by both global climate change and anthropogenic (the overexploitation of water) factors.

Soft-sediment deformation structures crop out in the Lower Cretaceous succession of the Gubbio anticline in the Umbria-Marche Apennines of Italy. The deformation interval is ~13 m thick and occurs between the upper Hauterivian–lower Aptian Maiolica Formation and the Aptian Marne a Fucoidi Formation. It can be observed along the anticline for a distance of 12 km. Different types of deformation structures are distributed in several outcrops, with detachment extensional structures prevailing in the southeast sector. Imbricated slides, slump structures, and chaotic layers are distributed vertically and longitudinally in the middle and/or lower part of the deformed sediments. In the northwest sector of the anticline, compressional duplex structures can be considered the lower section of a large sediment failure. Geometrical and kinematic analysis of the fold axis trends and sliding surfaces have led to infer a single, large gravitational event possibly Albian in age. The synsedimentary deformation could be activated by several internal trigger mechanisms induced by external regional tectonic events such as earthquakes. An orthogonal system of calcite veins crossing the limestone layers represents the primary pathway for fluid-driven breaching of joint seals. These fluids can be related to the significant increase in the total organic carbon in the Hauterivian–Aptian layer of the Maiolica and Marne a Fucoidi Formations. This suggests the possibility that the limestone layer, sandwiched and sealed between clay of the organic-rich black shales, could have favored a pore pressure increase approaching lithostatic stress. With a thin overburden, lithostatic stress is more easily reached at low hydrostatic pressure. This slump sheet occurrence suggests the existence of a local paleoslope dipping toward the north-northwest, where the mass involved in the deformation is distributed over an estimated area of 60 km 2 for a volume of 0.8 km 3 of displaced sediments. The restoration and rotation of the slump fold hinges to the Early Cretaceous direction, in line with available paleomagnetic data, have shown that the strike of the slope corresponds to the main trend of the oldest Jurassic extensional lineaments and is linked to transform faults of the westernmost Tethys rifting systems.

We investigated the petrogenetic characteristics of the Paleogene Veneto volcanic province and compared them with other intraplate magmatic occurrences of the Adria–North Africa plate since Late Cretaceous time. Veneto volcanic province magmas were erupted through a transtensional rift system that resulted from intra-plate reactions to the Alpine collisional events. The lavas, mostly basic in composition, encompass a wide range of serial affinities from (mela)-nephelinites to quartz-normative tholeiites. Nephelinites and basanites often carry spinel-peridotite mantle xenoliths that have rheologic and thermobarometric characteristics that indicate an origin from the mechanical boundary layer at depths not exceeding 50–60 km. Incompatible element patterns of the most primitive Veneto magmas, together with their isotopic signature ( 87 Sr/ 86 Sr 0.70315–0.70386; 143 Nd/ 144 Nd 0.51279–0.51298; 206 Pb/ 204 Pb 18.8–19.8), share geochemical characteristics with other magmatic occurrences of Adria–North Africa domains, and they show a clear affinity with intraplate sodic lavas, particularly HIMU (high U/Pb = high µ) and, to a lesser extent, enriched-mantle–ocean-island basalt (EM2-OIB) magmas. An integrated petrogenetic model, generally applicable for Adria–North Africa domains, suggests that most of the magmas were generated within the spinel-peridotite lithospheric mantle, from progressively deeper sources (30–100 km) and with a concomitant decrease in the degrees of partial melting (25%–3%) from quartz-normative tholeiites to nephelinites. The modeled magma sources invariably require enrichments in incompatible elements and metasomatic phases comparable (or equivalent) to those observed in some mantle xenoliths associated with the Veneto volcanic province lavas. Two kinds of mantle sources were identified: lherzolites bearing amphibole ± phlogopite for tholeiites to basanites, and lherzolites bearing amphibole ± phlogopite plus carbonatitic components for nephelinites. The elemental and isotopic characteristics of these mantle sources correspond to variable mixing of HIMU and, to a lesser extent, EM2 metasomatic components with a pristine depleted-mantle (DM) lithosphere. The HIMU metasomatizing agents may possibly be related to the mantle plume that is thought to extend from the eastern Atlantic to Europe and the Mediterranean, including Adria–North Africa domains, since the Late Cretaceous. These components more effectively accumulated in the lower lithospheric portion, i.e., the thermal boundary layer, whereas older metasomatic EM2 components may have been better preserved in the upper, more rigid, mechanical boundary layer.

Abstract In the Jurassic-lower Cretaceous sequence of central Apennines and their foreland (onshore and offshore Marche-Abruzzi regions), the dolomitization processes enhanced the petrophysical properties of the carbonate platform and slope series. The area experienced a first phase of passive-margin regime, from the Lower Jurassic to the Miocene: the Liassic carbonate platform underwent extensional tectonics that established the southern Apulian-Apennines persisting platforms and the northern Umbria-Marche basin; within the basin, differential subsidence rates created faulted horsts characterized by condensed series. From upper Miocene, the area entered the collision-margin phase when its eastern part was involved in the Apennines orogeny. The aim of this study was to analyze the dolomitization process in relation with the fluid-flow changes caused by the evolution of the geological framework. Dolomitized bodies are mainly located at the Jurassic-Early Cretaceous platform edges and in the paleohigh areas, particularly in the platform Calcare Massiccio and basinal Corniola formations, with minor extension to younger slope successions (up to Maiolica Formation). The petrographic observations evidenced a multiphase dolomitization of alternated dolomite replacement, dissolution, and recrystallization. The carbon and oxygen isotopic analyses suggest a seawater-derived diagenesis in a wide temperature range; this is confirmed by the fluid-inclusion analyses that detected a few stages of dolomitization events during a progressive heating of the carbonate series. The reconstructed paragenetic sequence is almost the same in all the studied successions, both in outcrop and subsurface. The data collected show that the dolomitization processes changed during the evolution of the area from a passive-margin domain to the collision-margin regime. In both phases, the interaction between the increasing burial temperature and the fluid migration paths, which is driven by the approaching orogenic wave, is suggested. The first dolomitization event (dolomite 1) is characterized by low homogenization temperature ( T h ) and is interpreted as a replacement of calcite precursor; its formation occurred during the passive-margin domain and is strongly dependent on the rate of subsidence of the different areas. The dolomite 1 time of generation varies from Cretaceous, in the highly subsiding areas of the thrust zone, to the Miocene in the paleohighs of the foreland. Dolomite overgrowths (dolomite 2) precipitated at higher temperatures. In the depocenters of thrust zone, those temperatures (as much as 130°C) were reached during maximum overburden during the upper Miocene, whereas in the foredeep and foreland areas, the high-temperature dolomitizing fluids seem to flow through faults during the orogenic phases (Pliocene). In the whole studied area, pore-filling dolomite cements (dolomite 4 and saddle dolomite) are supposed to be precipitated from heated fluids coming from deep strata along fault planes. Regional considerations and salinity data of the fluid inclusions support the hypothesis that the dolomitizing fluids of the last phases could come from Triassic evaporites that are present in the area and represent the detachment surface of the thrusts.