Geo-structural map of the Laguna Blanca basin (Southern Central Andes, Catamarca, Argentina)

The Laguna Blanca basin is a rhomb-shaped basin located at the SE margin of the Puna plateau in the southern Central Andes (Catamarca, Argentina). An interactive analysis using remote sensing and field mapping enabled us to produce a geo-structural map at a 1:350,000 scale. Satellite images from multispectral sensors (ASTER and Landsat 7 ETM+) and medium resolution Digital Elevation Models (SRTM and ASTER GDEM) were used in order to recognize the structures and main lithologies, which were validated in the field and through laboratory tests (e.g. spectral analysis). The final result is a geo-structural map of the Laguna Blanca basin with a new geological unit subdivision, highlighting its tectonic origin, which appears to be related to a releasing stepover along N-S sinistral strike-slip master faults

Analisi morfologica di sistemi carsici tramite software di elaborazione 3D: il caso dei Piani Eterni nel Parco Nazionale Dolomiti Bellunesi, Veneto, Italia

Negli ultimi anni lo sviluppo di software per la resa vettoriale 3D dei sistemi carsici e per la costruzione di modelli geologici, ha permesso di ampliare notevolmente le potenzialità delle analisi di controllo strutturale e litologico dei vuoti carsici. L’analisi tridimensionale dei condotti, in cavità topografate per almeno 5 km di sviluppo spaziale (sistemi di dimensione non locale), permette di individuare le zone di maggiore carsificazione dei massicci carbonatici e di metterle in relazione al contesto geologico della zona. Le caratteristiche morfologiche dei sistemi carsici epigenetici sono controllate da fattori direttamente connessi con l’assetto strutturale dei massicci, le litologie e l’evoluzione paleogeografica dell’area. Grazie ai software di resa 3D è possibile individuare inception horizons da analisi statistiche della distribuzione dei vuoti, ricostruire in tre dimensioni particolari orizzonti stratigrafici e desumere le successive fasi di stazionamento della tavola d’acqua nel sistema carsico. Lo studio tramite metodologie 3D del Sistema dei Piani Eterni, nelle Dolomiti Bellunesi, ha evidenziato le varie fasi di stazionamento del livello di base, le relazioni tra le paleo- tavole d’acqua con le superfici di controllo stratigrafico e tettonico, fornendo interessanti spunti sull’evoluzione paleogeografia e morfotettonica dell’intero massiccio.In the last decade the development of 3D cave topography software has allowed to perform new methods of analysis on the structural and lithological control of karst systems. The 3D statistical analysis of conduit distribution provides identification of strata or structural discontinuities more favorable for the speleogenetic process and the finding of correlations with the geological context of the area. The structural settings, the lithologies and the paleogeographical conditions control directly the morphologic characters and the general shape of an epigenic karst system. The 3D analysis permits to identify inception horizons and to infer the subsequent lowering stages of the paleo-watertable. This study of the Piani Eterni Karst System (Belluno Dolomites) by a 3D approach has demonstrated the validity of this method, detecting the most important paleo-phreatic levels and their relationship with the inception horizons, and the main structural and stratigraphic surfaces

Regional polyphase deformation of the Eastern Sierras Pampeanas (Argentina Andean foreland): strengths and weaknesses of paleostress inversion

The Eastern Sierras Pampeanas of central Argentina are composed of a series of basement-cored ranges, located in the Andean foreland c. 600 km east of the Andean Cordillera. Although uplift of the ranges is partly attributed to the regional Neogene evolution (Ramos et al. 2002), many questions remain as to the timing and style of deformation. In fact, the Eastern Sierras Pampeanas show compelling evidence of a long lasting brittle history (spanning the Early Carboniferous to Present time), characterised by several deformation events reflecting different tectonic regimes. Each deformation phase resulted in further strain increments accommodated by reactivation of inherited structures and rheological anisotropies (Martino 2003). In the framework of such a polyphase brittle tectonic evolution affecting highly anisotropic basement rocks, the application of paleostress inversion methods, though powerful, suffers from some shortcomings, such as the likely heterogeneous character of fault slip datasets and the possible reactivation of even highly misoriented structures, and thus requires careful analysis. The challenge is to gather sufficient fault-slip data, to develop a proper understanding of the regional evolution. This is done by the identification of internally consistent fault and fracture subsets (associated to distinct stress states on the basis of their geometric and kinematic compatibility) in order to generate a chronologically-constrained evolutionary conceptual model. Based on large fault-slip datasets collected in the Sierras de Cordoba (Eastern Sierras Pampeanas), reduced stress tensors have been generated and interpreted as part of an evolutionary model by considering the obtained results against: (i) existing K\u2013Ar illite ages of fault gouges in the study area (Bense et al. 2013), (ii) the nature and orientation of pre-existing anisotropies and (iii) the present-day stress field due to the convergence of the Nazca and South America plates (main shortening oriented WSW-ENE). Although remarkable differences in reactivation mechanisms have been observed for the various studied lithological domains (schist, gneiss and granitic rocks), the brittle regional polyphase deformation of the Eastern Sierras Pampeanas appears to be dominated by two extensional episodes (sigma3 oriented NE/ENE and WNW, respectively), which can be associated with Middle-Late Permian to Early Cretaceous tectonism, followed by a compressional paleostress (sigma1 oriented ENE), which is compatible with the present day Andean convergence. Paleostress inversion techniques, despite all uncertainties involved, represent a robust approach to disentangle complex polyphase deformation histories both in term of reactivation mechanisms and strain partitioning

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 increases the local fracturing and the permeability favoring the upwelling of the thermal waters. Numerical simulations are performed to validate the proposed conceptual model using a finite difference code that simulates thermal energy transport in hydrothermal systems. A specific configuration of thermal conductivity and permeability for the formations involved in the thermal system is obtained after calibration of these parameters. This set of parameters is verified in a long-term simulation (55,100 years) obtaining a 60–70 °C plume in the EGF area. The modeled temperatures approach the measured temperatures of 60–86 °C, demonstrating that this conceptual model can be realistically simulated

Fault Control on a Thermal Anomaly: Conceptual and Numerical Modeling of a Low\u2010Temperature Geothermal System in the Southern Alps Foreland Basin (NE Italy)

The interest on low\u2010temperature geothermal resources is progressively increasing since their renewability and widespread availability. Despite their frequency, these resources and their development have been only partially investigated. This paper unravels the major physical processes driving a low\u2010temperature geothermal resource in NE Italy (Euganean Geothermal System) through conceptual and numerical modeling. Dense fracturing associated to regional fault zones and a relay ramp enhances regional to local flow of thermal waters. Their rapid upwelling in the Euganean Geothermal Field is favored by open extensional fractures deforming the relay ramp. The water (65\u201386 \ub0C) is intensively exploited for balneotherapy, rendering it a profitable resource. Three\u2010dimensional coupled flow and heat transport numerical simulations based on this conceptual model are performed. Despite the presence of a uniform basal heat flow, a thermal anomaly corresponding to field observations develops in the modeling domain reproducing the relay ramp. Intensive fracturing extending across a wide area and a slightly anomalous heat flow favors a local increase in convection that drives the upwelling of deep\u2010seated hot waters. The simulations corroborate and refine the conceptual model, revealing that water of up to 115 \ub0C is likely to be found in the unexplored part of the thermal field. This study furthers knowledge on fault\u2010controlled low\u2010temperature geothermal resources where the geological setting could enhance local convection without anomalous heat flows, creating temperatures favorable for energy production. Conceptual and numerical modeling based on solid geological and hydrogeological reconstructions can offer a support tool for further detailed explorations of these prominent resources

Unravelling the importance of fractured zone in regional fluid flow: insights from the hydrothermal modelling of the Euganean geothermal system (ne Italy)

Euganean Geothermal System, fault system, 3D coupled flow and heat transport numerical model

defining the hydrogeological behavior of karst springs through an integrated analysis a case study in the berici mountains area vicenza ne italy

Knowledge of the hydraulic and geological properties of karst systems is particularly valuable to hydrogeologists because these systems represent an important source of potable water in many countries. However, the high heterogeneity that characterizes karst systems complicates the definition of karst hydrogeological properties, and their estimation involves complex and expensive techniques. In this study, a workflow for karst spring characterization was used to analyze two springs, Nanto spring and Mossano spring, located in the Berici Mountains (NE Italy). Based on the data derived from 4 years of continuous hourly monitoring of discharge, water temperature and specific electrical conductivity, a hydrogeological conceptual model for the monitored springs was proposed. Flow rate measurements, which combined recession curve, flow duration curve and autocorrelation function techniques, were used to evaluate the spring discharge variability. Changes in spring discharge can be related both to the degree of karstification/permeability and to the size of the karst aquifer. Moreover, combining monitored parameters and rainfall—analyzed by the cross-correlation function and VESPA (Vulnerability Estimator for Spring Protection Areas) index approach—permitted assessment of the spring response to recharge and the behavior of the drainage system. Although the responses to the recharge events were quite similar, the two springs showed some differences in terms of the degree of karstification. In fact, Mossano spring showed a more developed karst system than Nanto spring. Three systems (two karsts and one matrix/fractured) are outlined for Mossano spring, while two systems (one karst and one matrix/fractured) are outlined for Nanto spring

Pre-Alpine and Alpine deformation at San Pellegrino pass (Dolomites, Italy)

In this work, we present the geological map of the San Pellegrino pass, inserted in the spectacular scenario of the Dolomiti region (Southern Alps, Italy), at a scale of 1:10.000 and accompanied by geological cross-sections. The detailed distinction of lithological thin units allowed to achieve a consistent interpretation of the local structural setting by drawing brittle and ductile Alpine tectonic deformations. The differential deformation and structural styles within the geological map are the result of the different rheological nature of volcanic and sedimentary rocks, as well as of the superimposition of compressional Alpine tectonics over Permo-Mesozoic extensional tectonic phases, and consequent reactivation of inherited structures

Geo-structural map of the Laguna Blanca basin (Southern Central Andes, Catamarca, Argentina)

The Laguna Blanca basin is a rhomb-shaped basin located at the SE margin of the Puna plateau in the southern Central Andes (Catamarca, Argentina). An interactive analysis using remote sensing and field mapping enabled us to produce a geo-structural map at a 1:350,000 scale. Satellite images from multispectral sensors (ASTER and Landsat 7 ETM+) and medium resolution Digital Elevation Models (SRTM and ASTER GDEM) were used in order to recognize the structures and main lithologies, which were validated in the field and through laboratory tests (e.g. spectral analysis). The final result is a geo-structural map of the Laguna Blanca basin with a new geological unit subdivision, highlighting its tectonic origin, which appears to be related to a releasing stepover along N-S sinistral strike-slip master faults