101,897 research outputs found
Progresso e tradizione nella storiografia filosofica dell’Ottocento spagnolo
No full textAnalisi della riflessione di Menéndez Pelayo sul problema della relazione tra tradizione e progresso
Note Illustrative della Carta geologica d'Italia alla scala 1:50.000 F. 171 Cesana Torinese, Servizio Geologico d'Italia - ISPRA
No full text<p>Note illustrative redatte per il Foglio geologico n. 171 Cesana Torinese della Carta Geologica d'Italia alla scala 1:50.000. 132 pp.</p>
Il Kant di Miguel de Unamuno
No full textAnalisi dell'interpretazione unamuniana del pensiero kantian
Evolution of karst in Messinian gypsum (Monferrato, Northern Italy)
No full textIn the Tertiary Basin of Piedmont (Northern Italy) an important Messinian sedimentary succession crops out, composed of pre-evaporitic clays, macrocrystalline gypsum beds with marly interbeds, a microcrystalline gypsum bed, redeposited gypsum and post-evaporitic lacustrine-marine fine sediments. In the Monferrato area the entire thickness of the evaporite sequence is extremely variable, between a maximum of 70 meters up to only a few meters, due to an important erosional surface that cuts the upper part of the Messinian series. This erosional surface has formed at the end of the evaporite cycle, when freshly deposited gypsum rocks were exposed undergoing an extensive karstification both at the surface and at depth. Some of the known karst voids appear to have started forming during a short intra-Messinian phase of emersion. This hypothesis is based on three observations: 1) in many sectors of the area gypsum beds have been karstified although outcropping only rarely, most of the time composing a confined unit between Pre-Messinian and Upper Messinian-Pliocene impermeable beds of clay- and siltstones; 2) the fauna associations found in cave sediments, although partially remobilised, indicate a Burdigalian-Lower Pliocene age and would agree with a Messinian age of the voids they occupy. Their mobilisation with the Pliocene impermeable cover in place seems hard to defend; 3) the best developed karst conduits in gypsum have been discovered well below the present valley bottoms, and their genesis is difficult to explain in a phreatic situation between two impermeable beds. These voids have probably formed above local base level during the intra-Messinian uplift period
Geology of the Villalvernia – Varzi Line Between Scrivia and Curone valleys (NW Italy)
No full text<p>The External Ligurian and Epiligurian Units in the Northern Apennines of Italy are tectonically juxtaposed with the Tertiary Piedmont Basin along the Villalvernia – Varzi Line, which represents a regional scale fault zone, E-striking. Our map, at the 1:20,000 scale, describes the tectono-stratigraphic evolution of this sector that resulted from multistage faulting along that fault zone. Four main tectonic stages are defined on the basis of the crosscutting relationships between mapped faults and stratigraphic unconformities: late Priabonian – Rupelian, Chattian – early Miocene, late Serravallian – Tortonian, and late Messinian – early Pliocene. Our results demonstrate that since the late Burdigalian, the Villalvernia – Varzi Line was sealed by the gravitational emplacement of a chaotic rock body. The deposition of the late Serravallian – early Messinian succession is controlled by NW-striking strike-slip faults that crosscut to the west the Villalvernia – Varzi Line. Extensional tectonics related to regional scale N-dipping tilting characterized the late Messinian – early Pliocene time interval.</p
Stratigraphic evidence of glacier interactions in the Isarco-Pusteria valley junction (Italian Alps): unraveling the Late Pleistocene landscape evolution
No full textThe valley junction of Isarco and Pusteria (Rienza River), located in the Bressanone area, showcases a complex stratigraphic succession that traces back to the Late Pleistocene evolution. Extensive field surveys and numerous drillings conducted between Bressanone and Varna/Sciaves have unveiled the stratigraphic architecture of the valleys. Four distinct glacier advances have been identified, with the thickest deposits attributed to the Last Glacial Maximum (LGM), characterised by a fine-grained subglacial traction till up to 30 metres thick. Additionally, two Lateglacial stadial moraines are linked to the Isarco glacier, indicating that the modern Rienza lower valley was sculpted as the ice retreated at the end of the LGM. A pre-LGM fluvial-lacustrine system, receiving contributions from both valleys, suggests that the junction was located further north than its current position. Below this deposit, an older glacigenic sediment layer consisting of coarse subglacial traction till marks a phase between two major ice advances. At the deepest point, core samples from the Isarco valley reveal fluvial deposits from the Pusteria valley catchment, highlighting the existence of a narrower lower reach across the Rienza River. This evidence indicates the long-standing presence of the river valley at the junction in the Sciaves/Varna area, well before the LGM. The discovery of a large landslide reveals notable slope dynamics due to glacial erosion, with the landslide body covered by LGM glacial deposits, whereas post-LGM slope deposits are related to small-scale slope processes
Seismic Landscape of the Monferrato Arc
No full textThe Emilia and Lombardia 2012 seismic sequence (two main shocks of Mw ca. 6.0) revamped once again the
scientific debate about the seismic hazard posed by Quaternary tectonic structures of the Po Plain foredeep (e.g., Serva,
1990; Boccaletti et al., 2004; Picotti and Pazzaglia, 2008; Michetti et al., 2012; Galli et al., 2012). The W sector of the
foredeep represents in particular the area with most controversial interpretation in terms of active tectonics and seismic
potential. For instance, in the ITHACA catalogue of capable faults the Monferrato Arc is regarded as a seismogenic
structure with potential for surface faulting earthquakes; while in the DISS database the W Lombardia and Piemonte
are essentially interpreted as areas lacking any evidence of active faulting and seismic sources with Mw > 5.5. In order
to attack this issue, we conducted field investigation, geomorphic analyses and the revision of the large existing
database of seismic reflection profiles covering the study area in order to assess the seismic landscape of the Monferrato
Arc. Our investigations confirm that the Late Quaternary landscape evolution of the South-Central Piemonte is the
result of the interaction between active tectonics and widespread phenomena of river avulsion and piracy, which
affected virtually the whole Piemonte and nearby Liguria region. In fact, these dramatic changes in the regional
drainage network are controlled by shortening and thrust fault growth, which started during Oligo-Miocene times and is
still active with visible deformation rates (Carraro et al., 1995). The development of the Apennines buried thrust fronts
since Miocene give rise to the progressive uplift of the Monferrato and Torino Hills, translated above the depositional
sequences of the Po Plain foredeep. The continuing deformation and displacement of the surficial deposits up to at least
the Mid Pleistocene allow us to regard the buried structures of the Monferrato Arc as potentially capable faults (IAEA,
2010). Therefore, based on the available data, the regional seismotectonic framework for the W Po Plain is comparable
with the one already recognized in the Emilia Arc or in the LombardiaVeneto S Alps (Modena 2012, Brescia 1222,
Verona 1117). The seismic landscape of the Monferrato Arc thus includes potential surface faulting earthquakes, with
M max in the order of 6.0 – 6.5 (Michetti et al., 2012), and accompanied by considerable liquefaction and earthquake
environmental effects
Miocene climate cooling and aridification of Antarctica may have enhanced syn-extensional magmatism in the western Ross Sea
No full textContinental rift systems are commonly characterized by volcanism with parental basaltic magmas sourced from the mantle. Erosion of the rift shoulders and sedimentation in the adjacent basins can affect the stress and thermal fields at depth, thereby affecting partial mantle melting. However, the sensitivity of magmatic activity to such surface forcing is elusive. Geological observations from the western Ross Sea, Antarctica, suggest rift onset in the Cretaceous with a transition from wide-rifting to narrow-rifting at the boundary between the Antarctic craton and the Transantarctic Mountains. Miocene climate cooling during rifting in the western Ross Sea, in addition, leads to an abrupt decrease in sedimentation rate, synchronous to the emplacement of the McMurdo Volcanic Group. This represents the largest alkali province worldwide, extending both inland and offshore of Transantarctic Mountains and western Ross Sea, respectively. Here, we use coupled thermo-mechanical and landscape evolution numerical modeling to quantify melt production in slowly stretching rift basins due to changes in erosion/deposition rates. The model combines visco-elasto-plastic deformation of the lithosphere and underlying mantle during extension, partial rock melting, and linear hillslope diffusion of the surface topography. The parametric study covers a range of slow extension rates, crustal thicknesses, mantle potential temperatures and diffusion coefficients. Numerical simulations successfully reproduce the similar to 150-200-km-wide extension of western Ross Sea and Miocene-to-present asthenospheric melt production (McMurdo Volcanic Group). Results further show that slow rifts magmatism is highly sensitive to sediment deposition within the basin, which inhibits mantle decompression melting and delays the crustal breakup. Regional climate-driven sedimentation rate changes are thus likely to have affected the syn-rift magmatic history of the western Ross Sea, Antarctica, supporting the relevance of interactions between surface and deep-seated processes across extensional settings
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