1,720,971 research outputs found
The F2 folds in the Verrucano as records of extensional tectonics in the Northern Apennines (Italy)
No full textPreliminary structural data from three localities where Verrucano sequences outcrop in the Northern Apennines (Italy) are reported. After a syn-collisional related D1 deformation phase, a D2 phase has been recognized. D2 causes prevailing recumbent symmetric folds (F2), whose geometric features imply vertical shortening and horizontal extension in NE-SW direction of steeply dipping sedimentary beds or tectonic layering, originated by the earlier D1 phase. The widespread occurrence of such structures in the outcrops of the Massa Unit of the Northern Apennines, suggests a general pure shear regime of deformation related to extensional tectonics
Mylonite development in the Hercynian basement of Sardinia (Italy)
No full textPlastic deformation predominates over large areas in the Hercynian basement of Sardinia during Lower Carboniferous continental shortening. Mylonitization associated with ubiquitous top-to-south-southwest thrusting decreases from internal (central Sardinia) to foreland areas (southern Sardinia). In the Barbagia unit, mylonites completely obliterate all the previous structures; in the Meana Sardo unit, plastic deformation strongly overprints early folds; and in the Gerrei unit, mylonites are found only below the Meana Sardo thrust. A thick shear zone, the Baccu Locci mylonite zone, develops between the Gerrei and Riu Gruppa units. Inferences from deformation mechanisms in quartz mylonites suggest a temperature during deformation below 400°C along thrusts throughout the study area. Overprinting relationships between foliations, deformation of annealed microstructures and porphyroblasts with inclusion patterns indicate that crystal growth occurred after early thrusting events and before the main nappe emplacement phase. Microstructural investigations in the Baccu Locci mylonites record two changes in the main deformation mechanism operating during progressive mylonitization. In the early stages of deformation, most of the strain is accommodated by dislocation creep in a fine-grained quartz matrix. At higher strain, dynamic recrystallization fully affects larger quartz crystals, producing pure quartz layers where plastic deformation and strain localize. Ongoing deformation together with syntectonic breakdown of feldspar producing mica leads to mineral changes, grain size reduction and reaction softening with strain localization in the fine matrix again. Dynamically deformed quartz is boudinaged in the later stages of mylonitization. Significant fluid infiltration during deformation can account for some of the large ore bodies hosted in the Baccu Locci mylonites. © 1998 Elsevier Science Ltd
GIS Technologies supporting the monitoring of water resource in the Cornia river basin (Tuscany, Italy).
No full textHydrochemistry of the high-boron groundwaters of the Cornia aquifer (Tuscany, Italy)
No full textThe groundwaters of the Cornia River alluvial aquifer (southern Tuscany) were studied to determine the origin of their characteristic high-boron content. The interpretation is based on concentrations of major ions and selected minor and trace elements (B, Br, F, and Li). Mass balance calculations confirm that the main processes in the entire system are mixing of three water types and cation exchange between waters and sediments. The observed geochemical patterns indicate that the Ca-HCO3 waters recharging the aquifer interact with the alluvial sediments, increasing the TDS contents of the groundwaters without changing their chemical facies. High SO4 (up to 1840 mg/l) and F (up to 2.6 mg/l) thermal (hot) waters are discharged at several points in the Cornia basin. These Ca-SO4 waters mix with the Ca-HCO3 waters in the upstream part of the basin. Near the coastline, seawater intrusion occurs as a result of over-pumping, giving rise to Na-Cl-dominated waters near the shore. Further inland, within the transition zone between fresh and salty waters, cation exchange on the clay fraction of the aquifer leads to a loss of Na and a gain of Ca, shifting the composition towards Ca-Cl and mixed-anion waters. Interaction with clay minerals explains the higher contents of B and Li in the Cornia groundwaters than in the seawater.
The geochemical data, presented in the form of GIS-based geochemical maps, provide a baseline that can be used as a useful diagnostic tool to monitor the hydrochemical evolution of the Cornia groundwaters in view of possible future degradation of their quality in response to natural causes and human activities, including geothermal developments in the general Larderello area
Enhanced water exploitation in the Val di Cornia (Italy): assuring quality and availability in a context of geogenic and anthropogenic groundwater contamination (boron, salinity, nitrates).
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Le sorgenti fredde dei Monti della Gherardesca (bacino del fiume Cornia, Toscana Meridionale): idrogeologia e geochimica.
No full textL'articolo descrive le sorgenti delle colline che bordano la Val Di Cornia (LI) dal punto di vista idrogeologico e geochimico
Carta geologica della Regione Autonoma della Sardegna - Sez.549 I «Castello di Quirra» in scala 1:25.000
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