A deep, narrow, and distorted Benioff zone, plunging from the Ionian Sea towards the southern Tyrrhenian basin, is the remnant of a long and eastward migrating subduction of eastern Mediterranean lithosphere. From ...A deep, narrow, and distorted Benioff zone, plunging from the Ionian Sea towards the southern Tyrrhenian basin, is the remnant of a long and eastward migrating subduction of eastern Mediterranean lithosphere. From Oligocene to Recent, subduction generated the Western Mediterranean and the Tyrrhenian back-arc basins, as well as an accretionary wedge constituting the SouthernAoenninic Arc.In the Tyrrhenian Sea, stretching started in late Miocene and eventually produced two small oceanic areas: the Vavilov Plain during Pliocene (in the centralsector) and the Marsili Plain during Quaternary (in the southeastern sector). They are separated by a thicker crustal sector, called the Issel Bridge. Back-arc exten-sion was rapid and discontinuous, and affected a land locked area where continental elements of various sizesoccurred. Discontinuities in extension were mirrored bychanges in nature of the lithosphere scraped off to form the Southern Apenninic Arc. Part of the tectonic units of the southern Apennines, accreted into the wedge from late Miocene to Pliocene, had originally been laid down on thinned conti-nental lithosphere, which should constitute the deep portion of the present slab. After Plio-cene, only Ionian oceanic lithosphere wassubducted, because the large buoyancy of thewide and not thinned continental lithosphere of Apulia and Africa (Sicily) preserved the seelements from roll back of subduction. After Pliocene, the passively retreating oceanic slabhad to adjust and distort according to the geometry of these continental elements.The late onset of arc volcanism in respect to the duration of extension in the Tyrrhenian-Ionian system may find an expla-nation considering an initial stage of subduc-tion of thinned continental lithosphere. The strong Pleistocene vertical movements that occurred in the whole southeastern system(subsidence in the back-arc basin and upliftin the orogenic arc) may instead be related to the distortion of the oceanic slab.展开更多
The present-day topography of the Italian peninsula results from the interactions between crustal-mantle and surface processes occurring since the Late Miocene. Analysis of exhumation and cooling of crustal rocks, ...The present-day topography of the Italian peninsula results from the interactions between crustal-mantle and surface processes occurring since the Late Miocene. Analysis of exhumation and cooling of crustal rocks, together with Quaternary drainage evolution,helps to unravel the tectonic-morphologic evolution of the Apennines by distinguishing end-member models,and hence describing the orogenic belt evolution. The pattern of regional topography, erosional history and present-day distribution of active deformation suggests that the eastward migrating extensional-compressional paired deformation belts may still control the topogra-phy of the northern Apennines, albeit at slower rates than in the past. Conversely, Quaternary drainage evo-lution in the central and southern Apennines suggests that the topography of these regions underwent a Quaternary regional arching, which is only partly con-sistent with the persisting migration of the compres-sional-extensional pair.展开更多
The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by sur-face wave velocity tomography and non-linear inve...The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by sur-face wave velocity tomography and non-linear inversion.Maps of the Moho depth, of the thickness of the lithos-phere and of the shear-wave velocities, down to depths of 200 km and more, are constructed. A mantle wedge, iden-tified in the uppermost mantle along the Apennines and the Calabrian Arc, underlies the prmctpat recent votca-noes, and partial melting can be relevant in this part of the uppermost mantle. In Calabria, a lithospheric dou-bling is seen, in connection with the subduction of the Ionian lithosphere. The asthenosphere is shallow in the Southern Tyrrhenian Sea. High velocity bodies, cutting the asthenosphere, outline the Adria-lonian subduction in the Tyrrhenian Sea and the deep-reaching lithospheric root in the Western Alps. Less deep lithospheric roots are seen in the Central Apennines. The lithosphere-asthenos-phere properties delineate a differentiation between the northern and the southern sectors of the Adriatic Sea,likely attesting the fragmentation of Adria.展开更多
This paper summarises the geological features of the Larderello-Travale and Monte Amiata areas, where the world's most ancient exploited geothermal fields are located. In both geothermal areas, three regional t...This paper summarises the geological features of the Larderello-Travale and Monte Amiata areas, where the world's most ancient exploited geothermal fields are located. In both geothermal areas, three regional tectonostratigraphic elements are distinguished, from the top: (a) Late Miocene-Pliocene and Quaternary,continental to marine sediments; (b) the Ligurian and Sub-Ligurian complexes, which include remnants of the Jurassic oceanic realm and of the transitional area to the Adriatic margin, respectively; (c) the Tuscan Unit(Tuscan Nappe), composed of sedimentary rocks rang-ing in age from Late Triassic to Early Miocene. The sub-stratum of the Larderello and Monte Amiata areas isreferred to as the Tuscan Metamorphic Complex. This ismainly known through drilling of geothermal wells. This complex is composed of two metamorohic units: the upper Monticiano-Roccastrada Unit and the lower Gneiss Complex. The Monticiano-Roccastrada Unit consists of(from top to bottom): the Verrucano Group,the Phyllite-Quartzite Group and the Micaschist Group.The Gneiss Complex consists only of pre-Alpine poly-metamorphic gneiss. The Tuscan Metamorphic Complexis affected by contact metamorphism by Plio-Quater-nary granitoids and their dy ke swarms. Hydrothermal phenomena still occur in both geothermal fields. The Larderello-Travale and Mt. Amiata geothermal fields are located in the inner Northern Apennines, in an area that has been subject to extension since the ?Early-Mid-dle Miocene. Two main extensional events are well expressed in the structures of the geothermal areas. The first extensional event (?Early-Middle Miocene) deter-mined the tectonic delamination of the Ligurian Units and Tuscan Nappe. The second extensional event (LateMiocene-Present) is characterized by high-angle nor-mal faults bounding the Neogene tectonic depressions of southern Tuscany.展开更多
文摘A deep, narrow, and distorted Benioff zone, plunging from the Ionian Sea towards the southern Tyrrhenian basin, is the remnant of a long and eastward migrating subduction of eastern Mediterranean lithosphere. From Oligocene to Recent, subduction generated the Western Mediterranean and the Tyrrhenian back-arc basins, as well as an accretionary wedge constituting the SouthernAoenninic Arc.In the Tyrrhenian Sea, stretching started in late Miocene and eventually produced two small oceanic areas: the Vavilov Plain during Pliocene (in the centralsector) and the Marsili Plain during Quaternary (in the southeastern sector). They are separated by a thicker crustal sector, called the Issel Bridge. Back-arc exten-sion was rapid and discontinuous, and affected a land locked area where continental elements of various sizesoccurred. Discontinuities in extension were mirrored bychanges in nature of the lithosphere scraped off to form the Southern Apenninic Arc. Part of the tectonic units of the southern Apennines, accreted into the wedge from late Miocene to Pliocene, had originally been laid down on thinned conti-nental lithosphere, which should constitute the deep portion of the present slab. After Plio-cene, only Ionian oceanic lithosphere wassubducted, because the large buoyancy of thewide and not thinned continental lithosphere of Apulia and Africa (Sicily) preserved the seelements from roll back of subduction. After Pliocene, the passively retreating oceanic slabhad to adjust and distort according to the geometry of these continental elements.The late onset of arc volcanism in respect to the duration of extension in the Tyrrhenian-Ionian system may find an expla-nation considering an initial stage of subduc-tion of thinned continental lithosphere. The strong Pleistocene vertical movements that occurred in the whole southeastern system(subsidence in the back-arc basin and upliftin the orogenic arc) may instead be related to the distortion of the oceanic slab.
文摘The present-day topography of the Italian peninsula results from the interactions between crustal-mantle and surface processes occurring since the Late Miocene. Analysis of exhumation and cooling of crustal rocks, together with Quaternary drainage evolution,helps to unravel the tectonic-morphologic evolution of the Apennines by distinguishing end-member models,and hence describing the orogenic belt evolution. The pattern of regional topography, erosional history and present-day distribution of active deformation suggests that the eastward migrating extensional-compressional paired deformation belts may still control the topogra-phy of the northern Apennines, albeit at slower rates than in the past. Conversely, Quaternary drainage evo-lution in the central and southern Apennines suggests that the topography of these regions underwent a Quaternary regional arching, which is only partly con-sistent with the persisting migration of the compres-sional-extensional pair.
文摘The velocity-depth distribution of the lithosphere-asthenosphere in the Italian region and surroundings is imaged, with a lateral resolution of about 100 km, by sur-face wave velocity tomography and non-linear inversion.Maps of the Moho depth, of the thickness of the lithos-phere and of the shear-wave velocities, down to depths of 200 km and more, are constructed. A mantle wedge, iden-tified in the uppermost mantle along the Apennines and the Calabrian Arc, underlies the prmctpat recent votca-noes, and partial melting can be relevant in this part of the uppermost mantle. In Calabria, a lithospheric dou-bling is seen, in connection with the subduction of the Ionian lithosphere. The asthenosphere is shallow in the Southern Tyrrhenian Sea. High velocity bodies, cutting the asthenosphere, outline the Adria-lonian subduction in the Tyrrhenian Sea and the deep-reaching lithospheric root in the Western Alps. Less deep lithospheric roots are seen in the Central Apennines. The lithosphere-asthenos-phere properties delineate a differentiation between the northern and the southern sectors of the Adriatic Sea,likely attesting the fragmentation of Adria.
文摘This paper summarises the geological features of the Larderello-Travale and Monte Amiata areas, where the world's most ancient exploited geothermal fields are located. In both geothermal areas, three regional tectonostratigraphic elements are distinguished, from the top: (a) Late Miocene-Pliocene and Quaternary,continental to marine sediments; (b) the Ligurian and Sub-Ligurian complexes, which include remnants of the Jurassic oceanic realm and of the transitional area to the Adriatic margin, respectively; (c) the Tuscan Unit(Tuscan Nappe), composed of sedimentary rocks rang-ing in age from Late Triassic to Early Miocene. The sub-stratum of the Larderello and Monte Amiata areas isreferred to as the Tuscan Metamorphic Complex. This ismainly known through drilling of geothermal wells. This complex is composed of two metamorohic units: the upper Monticiano-Roccastrada Unit and the lower Gneiss Complex. The Monticiano-Roccastrada Unit consists of(from top to bottom): the Verrucano Group,the Phyllite-Quartzite Group and the Micaschist Group.The Gneiss Complex consists only of pre-Alpine poly-metamorphic gneiss. The Tuscan Metamorphic Complexis affected by contact metamorphism by Plio-Quater-nary granitoids and their dy ke swarms. Hydrothermal phenomena still occur in both geothermal fields. The Larderello-Travale and Mt. Amiata geothermal fields are located in the inner Northern Apennines, in an area that has been subject to extension since the ?Early-Mid-dle Miocene. Two main extensional events are well expressed in the structures of the geothermal areas. The first extensional event (?Early-Middle Miocene) deter-mined the tectonic delamination of the Ligurian Units and Tuscan Nappe. The second extensional event (LateMiocene-Present) is characterized by high-angle nor-mal faults bounding the Neogene tectonic depressions of southern Tuscany.
