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Significato dei megastrati carbonatici e silicoclastici nella Formazione di Albidona (Miocene Inf., Appennino meridionale): implicazioni paleogeografiche.
No full textMegastrati carbonatici e silicoclastici della Formazione di Albidona (Miocene, Appennino meridionale)
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Unravelling source rocks of episutural and foredeep Late Eocene-Miocene arenites of northern Apennines and southern Alps
No full textThe Late Eocene to Late Miocene successions deposited along the northern Apennines and southern Alps are re-examined through integration of arenite petrography with fission-track dating on apatite and zircon. Key heavy minerals and rock fragments, chosen as indicators of Austroalpine, Penninic, Southalpine and Ligurian rock associations, have been combined to match with cooling ages of potential source rocks.
Northwest of the Val Secchia area, the Late Eocene to late Rupelian wedge-top basins were fed by western sources (Penninic and Ligurian units), while the foredeep basins were supplied from Austroalpine units, with the addition of Southalpine sources from the Early Miocene. Effusive centres conveyed epiclastic sands and pebbles to the sub-Ligurian foredeep but only fall-out deposits to the wedge-top basins during the Rupelian. Non deposition or recycling from Ligurian units occurred in the basins southwest of the Val Secchia structural divide. From late Chattian to Tortonian times, the sedimentary basins migrating on top of the Apenninic thrust system were fed mainly by Ligurian units, with important contributions by the recycling of older wedge-top successions.
The Austroalpine basement was the main source also for the Southalpine foredeeps until the uplift of the Southalpine units, as indicated by a marked increase of limestone/dolostone and rhyolite fragments and Jurassic fission-track detrital ages. This tectonic event occurred during the Burdigalian in the Lombardic sector and the during Tortonian in the Venetian sector.
Glaucophane is present in small amounts in the late Serravallian-Tortonian Marnoso-arenacea Fm but not in the coeval Venetian foredeep deposits. It is suggested that this mineral was recycled either from epiligurian successions and/or the Chattian-Serravallian succession from the Venetian/Dinaric area
Fission-track reconstruction of the front of the northern Apennine thrust wedge and overlying Ligurian unit.
No full textIn the Northern Apennines foreland, the Marnoso-arenacea Formation (MA Fin) records post-depositional burial temperatures overlapping with those of the zone of partial annealing of apatite fission tracks. Because the stratigraphy, sedimentology, petrography and structural evolution of this turbidite succession has been intensively studied over the last 40 years, the MA Fin provides an ideal case to apply the apatite fission-track method. The data show a general decrease of the maximum paleotemperature undergone by the MA samples toward the foreland area. The maximum burial, calculated using a geothermal gradient of 20degreesC/km, spans from more than 5 km to less than 2.5 km and indicates that the reconstructed total thickness of the MA succession is not enough to justify the determined burial values. Stratigraphic data indicates that the missing section consisted of a lower component (foredeep successions) and an upper allocthonous component composed of disrupted and chaotic oceanic sediments and minor ophiolites (Ligurian unit). The Ligurian unit overrode the foredeep succession during deposition. Its advancement toward the foreland area was associated with subsidence and only locally contrasted by thrust growth. The reconstructed wedge shape of the Ligurian limit, in its final and pre-erosional configuration at time of the maximum burial of the MA succession, shows a flat upper surface, which corresponds to a paleosurface of Early Pliocene age. This surface marks at 4 to 5 Ma the onset of the exhumation phase, which occurred at a mean rate of 1.2 mm/yr
Eustatic and Tectonic Control on Foreland Basin Hybrid Arenites: Case Study of the Hecho Group Turbidites (Eocene, Pyrenees)
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Evoluzione composizionale di un sistema di avanfossa: Le torbiditi di Hecho (Eocene, Pirenei)
No full textTurbidite Systems and Depositional Sequences in the Inner Eocene Basin of the South Central Pyrenees
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