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Early Cretaceous tectonic event in the Adria: Insight from Umbria-Marche pelagic basin (Italy)
No full textSoft-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 fl uid-driven breaching of joint seals. These fl uids 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 km2 for a volume of 0.8 km3 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
Postfazione di Giulia Simonetti
No full textPostfazione del libro "Tre pilastri del benessere psicologico" di Emanuela Menichetti. Piemme Mondadori
CO2 and speleogenesis: suggestions from hypogene karst of Italy
No full textThe CO2 driving the main karst processes needs to be considerate from different sources. The carbon dioxide produced in the soil and dissolved in the percolation water is considered as the main agent for karstification in the carbonate rocks. Superficial morphologies and underground caves are product of the corrosion of the limestone, while carbonate speleothems is the other end member of the process. Hypogene speleogenesis driven by deep seated fluids is the cave formation processes for the main karst systems in the Apennines of Italy. Hydrogen sulfide and endogenic carbon dioxide are the main agents for underground karst corrosion and the soil carbon dioxide plays a secondary rule. The limestone corrosion driven by hydrogen sulfide produces gypsum deposits in caves that could be assumed as the indicator of the hypogene speleogenesis. The action of endogenic carbon dioxide in the cave formation, especially if it operates at lower temperature, is not easy to detect and the resulting cave morphology is not helpful to recognize the cave formation process. The main sources of carbon dioxide in the underground karst system in the Apennines of Italy can be related to different processes driven by the endogenic fluids emissions. The crustal regional degassing seems to be the prevalent source for carbon dioxide in the karst massifs with the main release in the groundwater. Hydrogen sulfide and methane oxidation, possibly mediated by bacteria activity, are other sources in the buried Cenozoic sediments. Releasing of carbon dioxide along the faults and in the fractures occurring in the carbonate rocks is an important source, especially in theseismically active area. Finally, thermogenic reactions with carbonate rocks are well known as one of the main production mechanism of carbon dioxide released in the atmosphere. Data from carbon dioxide monitoring in several caves show a relevant contribution of the endogenic carbon dioxide (about 75 %) in the karst system which drives the speleogenesis reactions and shapes the underground morphologies
HYPOGENIC CAVES IN WESTERN UMBRIA(CENTRAL ITALY)
No full textThree karst areas located in the western sector of the Umbria Region (Central Italy) are here described: one northof Perugia, and the others to the south, close to Todi. All the end members of karst processes, from solution caves to Quaternary travertine deposits, are present in this region, associated withCO2 and H2S emissions. The geological and hydrogeological aspects of the main karst systems are analyzed and their underground morphologies and patterns taken into account. Caves have different sizes and vary from a single conduit to complex systems, where the passages show features related to a possible hypogenic speleogenesis. In the area northof Perugia there are small horizontal and vertical solution caves developed in poorly karstified marly limestone, along fracture systems, where phreatic morphologies are prevalent. The endogenic CO2 emissions seem to drive the underground karst evolution. Pozzi della Piana, located west of the town of Todi, is a fossil branchform network cave system developed in a Quaternary travertine and extending for more than 2500 m. The cave passages are arranged on at least two levels, withphreatic morphologies, cupola ceilings, and blind pits. Microcrystalline spalled gypsum blocks are associated withcusp features and wall pockets. The cave-forming process is believed to be linked to travertine deposition by supersaturated carbonate hydrothermal water richin H2S. In the Parrano area, the underground karst system consists of solution caves extending for many hundreds of meters at different elevations in bothsides of a small gorge. The cave patterns vary from single conduits to ramiform passages withanastomotic galleries and pits that intercept the water table witha temperature of 26°C, p CO2 of 10-1 atm, and H2S concentrations of 10 mg/l. Spongework, corrosion pockets, and cupola ceilings are common morphologies, withgypsum replacing limestone wall deposits. Cave formation by hypogenic speleo genesis is also well known in the Apennine karst system of M. Cucco and Frasassi, where bothfossil and active processes are observable. The same processes are responsible for the genesis of these karst systems in different geological and hydrogeological contexts.
Structural setting of the Acquasanta Terme geothermal system (Ascoli Piceno)
No full textThe low temperature (<50°) geothermal field of Acquasanta is located in a carbonate reservoir in the core of an anticline surronded by marls and sandstones acquiclude. The thermal water rises along an extended fracture system related to strike-slip faults. Thermal and geochemical dilutions occur in the upper part of the water-table. The water temperatures recorded in a deep karst system, show a predominant convective heat transfer along the fractures and a conductive thermal flow in the rock matrix. The hydrogeological system can be related to a thermally driven convective circulation, with a regional recharged area located in the Sibillini Mountains, a flow few kilometres depth, and a discharge along the F. Tronto valley
[2+4] vs [4+2] Cycloaddition Reactions of ortho-Thioquinones with 1,3-Dienes
No full textMono-ortho-thioquinones, of general formula 1, can be generate under very mild conditions by reacting the corresponding ortho-hydroxythiophthalimides 2 with bases.[1] Species 1, generate in situ, can be trapping through cycloaddition reactions with 1,3-dienes. This chemistry allowed us to study in detail the reactivity of thioquinones 1 and to demonstrate their double behaviour as hetero dienophiles, across the carbon-sulfur double bond, to give the spiro derivates 4 and as hetero dienes leading to the formation of the benzoxathiin derivatives 5.[2]
The reagents structure and the reaction conditions chosen make the difference in this reactions driving the interaction between o-thioquinones and 1,3-dienes to the formation of the [2+4] dihydrothiopyran spiro and/or the [4+2] benzoxathiin cycloadducts.
A computational study was conduct in order to achieve a deep understanding of both [2+4] and [4+2] paths.
[1] a) Capozzi, G.; Menichetti, S.; Nativi, C.; Simonti, C. Tetrahedron Lett. 1994, 35, 9451. b) Capozzi, G.; Falciani, C.; Menichetti, S.; Nativi, C. J.Org. Chem. 1997, 62, 2611.
[2] Menichetti, S.; Viglianisi, C. Tetrahedron 2003, 59, 5523
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