Dario Zampieri

Tertiary extension in the southern Trento Platform, Southern Alps, Italy

The southern Trento Platform (Southern Alps, NE Italy) was the locus of abundant mafic volcanism associated with Paleogene extensional tectonics. During the Pal eocene and throughout the Eocene, a NNW–SSE trending graben (the Alpone-Agno Graben (AAG)) developed in the eastern Lessini Mountains. The graben was filled with basaltic volcaniclastics, calcarenites, and lava flows. The AAG is a half-graben system probably bounded by rotational listric normal faults. Most faults in the graben dip towards the WSW. Paleostress analysis within the AAG shows that during the Eocene the direction of horizontal extension was ENE–WSW. The volcanic activity continued into the Oligocene; however, the relation between Oligocene tectonics and volcanism remains unclear. Gravimetric and magnetic anomalies in conjunction with the crustal thickness variations suggest a locus of lithospheric thinning slightly off-axis from the AAG. This can be explained by an overall asymmetric extensional geometry dominated by a WSW dipping detachment fault. The Paleogene geodynamic scenario of the Trento Platform suggests that the AAG developed as a foreland extensional response to the active collisional convergence between the European and Adriatic plates. Neogene compressional tectonics reactivated some of the Paleogene normal faults as strike-sup faults.

Evidence of recent surface faulting and surface rupture in the Fore-Alps of Veneto and Trentino (NE Italy)

Abstract The Fore-Alps of western Veneto and Trentino regions belong to the central Southern Alps (NE Italy), in which there is little evidence of very fresh surface ruptures or surface faulting. This does not seem to match historical data about earthquakes, some of which have been very intense. The strong influence of the inherited structures makes it difficult to detect a direct link between morphotectonic features and present-day stress fields. In the present study, four areas (Orsara, Scandole, Naole and Soran) with surface faulting and surface rupture features were examined, and models of morphotectonic evolution are discussed. In the Lessini Mountains, the Orsara graben and Scandole ridge show examples of surface faulting and surface rupture, respectively, reactivating Paleogene normal faults and fractures. Within the Orsara graben, rocky bluffs displace the previous morphological features. The bluffs are some decimetres to some metres high and are practically devoid of evidence of either physical or chemical weathering; on the slopes above them are steep areas which may be interpreted as the remnants of previous strongly weathered bluffs. The Scandole ridge has many trenches, some with rocky walls, which may be the result of several episodes of morphotectonic rupture. In the Giudicarie Belt, the Naole and Mt. Soran surface faulting landforms are details within large frontal culmination walls of Neogene thrusts. The Naole ridge corresponds to the southeastern sector of Monte Baldo. Here, inside a fault angle valley, a sinuous scarp originating from surface faulting marks the base of the fault scarp slope. Ridge splitting is the expression of the backward migration of separation niches due to slope tectonics, also evidenced on the slope by several terrace-like features and by a lower belt of very thick slope breccias. On Mt. Soran, in the Gruppo di Brenta massif, the surface faulting scarp faces uphill, giving rise to a trench-like feature. Downvalley of the scarp, there is the niche of a large landslide dated to 3 kyears B.P. All these landforms are consistent with slope tectonic movements caused by intense earthquakes. Whereas the morphostructures in the Lessini Mountains are the result of responses by sensitive structures, the Naole and Mt. Soran features express the evolution of frontal culmination walls of thrusts, with clear evidence of present-day tectonic activity. On the basis of the weathering of the scarps and associated features, the relative seismotectonic episodes probably occurred between the Bronze and Middle Ages.

Conceptual and numerical models of a tectonically-controlled geothermal system: a case study of the Euganean Geothermal System, Northern Italy

The Euganean Geothermal Field (EGF) is the most important thermal field in northern Italy. It is located in the alluvial plain of the Veneto Region where approximately 17*106 m3 of thermal water with temperatures of 60–86 °C are exploited annually. A regional-scale conceptual model of the Euganean Geothermal System is proposed in this paper using the available hydrogeologic, geochemical and structural data for both the EGF and central Veneto. The thermal water is of meteoric origin and infiltrates approximately 80 km to the north of the EGF in the Veneto Prealps. The water flows to the south in a Mesozoic limestone and dolomite reservoir reaching a depth of approximately 3,000 m and a temperature of approximately 100 °C due to the normal geothermal gradient. The regional Schio-Vicenza fault system and its highly permeable damage zone act as a preferential path for fluid migration in the subsurface. In the EGF area, a geologic structure formed by the interaction of different segments of the fault system in...

Mapping the variation of the potentiometric level of the Euganean thermal aquifer and relationship with the exploitation

The Euganean Geothermal Field (EGF) and its thermal water are a relevant natural and economical resource for Veneto Region (NE Italy). Approximately 14×106 m3 of hot water (temperature ranging from 65°C to 86°C) were exploited by 145 wells in 2014. The most exploited thermal aquifer is located at a depth ranging from 300 m to 600 m in fractured layers hosted within Mesozoic limestones. Six abandoned wells have been used to monitor its potentiometric level since 1975. The results show periods of level decrease followed by a recovery related to the exploitation of the thermal water. The aim of this work is to verify the reliability of the proposed model for the EGF area. Five monitoring surveys were carried out from November 2014 to November 2015 during periods of high and low exploitation. The potentiometric level of the aquifer, the temperature of the water and the flow rate were measured in approximately 130 wells. In particular, the data collected in the surveys of February 2015 (low exploitation) and April 2015 (high exploitation) were used to perform two maps of the potentiometric level. The maps are compared evidencing a general decrease of the potentiometric level from February to April in agreement with the variations observed by the continuous monitoring network. The results of this study permit to detail the areal distribution of both the potentiometric level and its variation.

Anthropic impact on thermal aquifer: the case study of the Euganean Geothermal Field (NE Italy)

The Euganean Geothermal Field represents an important natural and economical resource for Veneto region (NE Italy) and its thermal water is mainly used for balneotherapy. Approximately 170 wells exploit 14*106 m3/y of hot water (temperature from 65°C to 86°C) from rocky aquifers located at different depths. The potentiometric level of the most exploited 300-500 m deep aquifer has been monitored by a network of abandoned wells since 1975, and the exploitation has been monitored since 1979. The analysis of the level evidences an anthropic annual regime related to the touristic seasons and characterized by a decrease during spring and autumn (high rate of incoming tourists and high exploitation) and a recovery during winter and summer (low exploitation). In addition, a general increasing trend of the potentiometric level has been recorded since the 1990s and it can be related to the decrease of the exploitation. The time series showing the clearest relationship between level and flow rate is used to perform a black-box model using a Generalized Additive Model. The model estimates a natural potentiometric level of 15 m above the ground level, comparable with the level measured in a well far from the most exploited areas of the thermal field.