778 research outputs found
Petrological evolution of the European lithospheric mantle: from Archean to present day
No full textFrom 29 to 31 August 2007 the city of Ferrara (Italy) hosted the first workshop on European mantle petrology (EMAW2007). The event was organized by M. Coltorti (Earth Sciences Department, University of Ferrara), H. Downes (Birkbeck College, London University), M. Grégoire (Observatoire Midi Pyrénées, CNRS, Toulouse) and S. Y. O’Reilly (ARC National Key Centre, GEMOC, Macquarie University) and was sponsored by the University of Ferrara, the Istituto Universitario di Studi Superiori (IUSS) of the same university, the Gruppo Nazionale di Petrografia (GNP) and the Federazione Italiana di Scienze della Terra (FIST)
Late Pleistocene and Holocene fluvial–coastal evolution of an uplifting area: The Tronto River (Central Eastern Italy)
No full textThe piedmont area of the River Tronto (Italy) is characterised by Pleistocene and Holocene terraces at progressive elevations a.s.l. After the formation of wide unpaired meander terraces during the Early Holocene, the river created a 20-m-deep gorge into bedrock in its inner part. In mid-valley, the thalweg progressively enlarges and the Late Pleistocene and Holocene terraces converge downstream. A
wide alluvial plain was formed during braid-plain aggradation from ca. 4.3 BP, to the end of the 19th century, associated with slope erosion activated by human activities. Since the end of the 20th century, two series of artificial levees were created in order to prevent floods. Due to the reduced dimensions of the artificial river bed, floods still affect large parts of the plain after extreme events.
In the coastal sector, during the Early Holocene, a large bay extended approximately 3km inland from the present-day coastline. A barrier beach evolved during the Bronze–Iron Age and, until the Middle Ages, the river mouth entered a large lagoon. Progradation occurred from then until the beginning of the 20th century, when a delta extended up to 500m seaward. During the 20th century, following the creation of the artificial levees and quarrying the beach underwent coastal erosion, and had to be protected by breakwater
reefs. The anthropogenic modifications and their effects are among the main factors in the Holocene evolution of the landscape
Geomorphic and neotectonic evolution of the Ecuadorian Andes
No full textIn Early Miocene times the Cordillera did not exist and the Pacific Ocean reached the Oriente. In the Middle Miocene, the uplift of an elongated swell, consisting of Palaeozoic and older rocks, created the Eastern Cordillera. Decollements were activated diverging away from the Eastern Cordillera. In the eastern trench, located approximately in correspondence with the present day Interandean Depression, many thousands of meters of sediments were deposited. A planation surface was created at the end of Lower Pliocene from the Costa to the Oriente graded to sea level. Later, ignimbric flows covered much of the planation surface. Uplift brought the planation surface to 3500-4000 m. The Interandean Depression, bounded by normal faults, was created during the Upper Pliocene, and large strato-volcanoes erupted at this time. The volcanic activity contributed to the filling of an accumulation plateau preserved today in many parts of the Interandean Depression. The creation of the Interandean Depression is the result of lateral spreading activated as a consequence of uplift of the Cordillera. In the Middle and Late Pleistocene the Cordillera and the Accumulation plateau were mostly affected by downcutting with minor episodes of accumulation during the cold phases. (C) 2000 Elsevier Science B.V. All rights reserved
Caratteri geomorfologici della fascia costiera compresa tra la foce del fiume Albegna, la Laguna di Orbetello ed Ansedonia
No full textLa fascia costiera compresa tra la foce del Fiume Albegna e il promontorio di Ansedonia è una costa mista la cui genesi è stata dominata prevalentemente da processi erosivi in corrispondenza del promontorio del M. Argentario e di Ansedonia e da processi deposizionali nei cordoni litorali limitrofi. La crescita dei cordoni litorali è fortemente condizionata dagli apporti fluviali dell’Albegna a nord e del Fiora a sud. L’analisi geomorfologica ha permesso di individuare le varie tappe dell’evoluzione costiera e della genesi della laguna verificatesi durante l’Olocene. Sono stati individuati numerosi paleoalvei dell’Albegna che hanno creato degli apparati deltizi sia prima della genesi dei cordoni che successivamente. La massima ingressione olocenica ha generato una scarpata di erosione che ha interessato, terrazzandoli, depositi di conoide alluvionale, fluviali, detritici ed eolici deposti durante l’ultima fase fredda pleistocenica. Terrazzi minori associati alla divagazione laterale di meandri ad ampio raggio di curvatura e paleoalvei caratterizzano il bordo settentrionale della pianura dell’Albegna
Recent extensional faulting in the Gulf of Taranto area: Implications for nuclear waste storage in the vicinity of Scanzano Ionico (Basilicata) [Deformazioni distensive recenti nell’entroterra del Golfo di Taranto: implicazioni per la realizzazione di un deposito geologico per scorie nucleari nei pressi di Scanzano Ionico (Basilicata)]
No full textIn questo studio viene segnalato un sistema di faglie dirette che interessa depositi marini terrazzati recenti nell’entroterra del Golfo di Taranto. L’area di indagine è collocata lungo il fronte dell’Appen- nino meridionale, una catena a pieghe e sovrascorrimenti originatasi in seguito alla chiusura del bacino oceanico mesozoico della Tetide, ed alla deformazione compressiva del margine passivo adriatico du- rante il Terziario ed il Quaternario. Il fronte della catena è parzial- mente sepolto dai depositi sinorogenici Plio-Pleistocenici, che costi- tuiscono il riempimento della Fossa Bradanica. La porzione superiore della successione del Pleistocene medio è costituita da sab- bie e conglomerati di origine marina la cui sommità è modellata in vari ripiani che una precedente letteratura interpreta come terrazzi marini organizzati in ordini distinti.
Le analisi di immagini da satellite e di foto aeree, e la realizza- zione di una carta geomorfologica di dettaglio, indicano la presenza di numerosi lineamenti morfologici che controllano la distribuzione attuale del reticolo idrografico superficiale. Alcune di queste strutture coincidono con le tracce di faglie dirette che dislocano le superfici dei terrazzi marini producendo gradini di circa 10 m. Per questo motivo i vari ripiani possono essere considerati elementi di un unico terrazzo dislocato da faglie dirette. Sebbene molti di questi gradini di faglia si esauriscano lateralmente, le scarpate principali raggiungono e a volte superano, un’estensione di 4 km. Le scarpate hanno altezza compresa fra 2 e 10 m, ma localmente è possibile quantificare rigetti verticali fino a 50 m. La maggior parte dei lineamenti morfologici, il cui anda- mento cartografico evidenzia una prominente struttura arcuata, han- no una direzione compresa fra ENE-WSW e N-S.
L’esame dei caratteri geomorfologici, sedimentologici e stratigra- fici dell’area consente di avanzare un’ipotesi originale sui rapporti fra le faglie dirette e lo sviluppo dei terrazzi. I depositi terrazzati si sono formati in seguito ad un evento di progradazione durante il Pleistoce- ne medio, ben documentato anche in altre aree dell’Italia peninsula- re. L’analisi dei lineamenti morfologici evidenzia una stretta relazio- ne tra la distribuzione cartografica arcuata dei sistemi di faglie dirette e l’andamento della linea di costa attuale, indicando un con- trollo tettonico sulla morfologia del litorale ionico. Lo sviluppo delle faglie dirette potrebbe essere ricondotto a processi di tettonica gravi- tativa, in cui i singoli elementi si scollerebbero a livelli sub-superficia- li. I movimenti regionali che marcano la terminazione meridionale dei depositi di Fossa Bradanica sarebbero originati dal generale ba- sculamento di questo dominio verso i quadranti sud-orientali, con l’attivazione di un collasso gravitativo della scarpata continentale.
I risultati di questo studio hanno un’importante ricaduta che in- veste il delicato aspetto della sicurezza sociale. Nel novembre 2003 la zona di Scanzano Ionico è stata dichiarata, con Decreto Legge n. 314 del 14/11/03, idonea alla realizzazione di un deposito geologico per scorie nucleari. La segnalazione di importanti faglie dirette che di- slocano depositi marini terrazzati indica che l’entroterra del Golfo di Taranto è stato soggetto a movimenti tettonici in epoca recente. Le evidenze di superficie disponibili non consentono, inoltre, di esclu- dere che alcune di queste strutture possano, in toto od in parte, essere ancora attive. Questi dati, pertanto, dovrebbero costituire elemen- ti per un’approfondita riflessione sulla generale stabilità geologica dell’area e sulla possibilità che l’area di Scanzano Ionico venga riproposta come sito per la realizzazione di un deposito geologico per scorie nucleari.The Gulf of Taranto in southern Italy provides an excellent case where it is possible to document the importance of normal faults in displacing terraced deposits. The study area is located at the front of the southern Apennines, that is a fold-and-thrust belt developed following the closure of the Mesozoic Tethys Ocean, and the deformation of the Adriatic passive margin during Tertiary and Quaternary times. The outer, eastern parts of the belt were structured in recent, i.e. up to Middle Pleistocene times. The front of the chain is partially sealed by Pliocene-Pleistocene foredeep deposits, which represent the infill of the Bradanic trough. The upper portion of the middle Pleistocene succession consists of marine sands and conglomerates that in the previous literature have been arranged in several orders of terraces. Analysis of aerial photographs and geomorphological mapping has shown the occurrence of prominent geomorphic lineaments, which appear to control the local drainage pattern. Some of these structures coincide with the map trace of normal faults that produce vertical offsets of the marine terrace surfaces in the order of ca. 10 m each. Most of the fault escarpments can be traced for up to 3-4 kilometres, and laterally reduce their elevation and terminate. Scarp height is comprised between 2 and 10 meters, although some faults are locally observed to produce displacements up to 50 m. Their mean trend ranges from ENE-WSW to N-S and defines an arcuate pattern that mimics the present coastline. An accurate geomorphological, sedimentological and stratigraphic analysis has been carried out in a selected area of the Bradanic trough (Pisticci transect) to investigate in detail the relationships between normal faults and the development of the terraces. This analysis allowed 5 facies associations to be recognised, related to the upper and lower beachface and to the neritic clays which represent the substratum of the terraces. More importantly, we observed that all the terraced deposits in the Pisticci transect could be referred to a single sedimentary body displaced by faults. The terraced deposits are related to an event of beach progradation, of Middle Pleistocene age, which has been documented in other areas of the Italian peninsula. These results outline an intimate relationship between the arcuate trend of the recognised fault set and the present coastline pattern. The development of the normal faults can be related to large-scale gravitational processes developed after the general tilting of the Bradanic trough towards the SE. The development of normal faults could be related to gravity tectonics connected to a shallow-dipping détachment horizon. These large-scale movements involve the southern part of the Bradanic trough. They appear related to a gravitational collapse towards the SE of the continental escarpment generated by the general tilting of the Bradanic trough. In addition, and more important, the recognition of recent extensional faulting and tectonic instability in the Taranto Gulf has a relevant implication for a matter of social security. In November 2003, the area of Scanzano Jonico was proposed as a site for nuclear waste deposit. The discovery of recent extensional faults undermine the generalised assumption of a long-lasting tectonic quiescence in the Taranto Gulf, and suggests that the entire investigated area may not be suitable for nuclear waste storage
Tre nuovi trancianti in selce in Lombardia. Osservazioni tecniche, cronologice e culturali
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Middle-Upper Pliocene ‘compression’ and Middle Pleistocene ‘extention’ in the modelling of the East Tiber Basin (Central Italy): from ‘perched’ to ‘extentional basin in the Northern Apennines
No full textThe late Lower Pliocene Planation surface and mountain building of the Apennines (Italy)
No full textInvestigations on the nature, age and lateral relationships of the remnants of Italian planati on surfaces indicate that: 1) a single planation surface (PS) is recognisable across the Apennines along the inner part of the Italian Peninsula; 2) it was originally very flat; 3) it is better preserved on harder rocks and is not preserved on the higher relief because of major uplift and consequent dissection or glacial erosi on; 4) it cuts terrain ranging in age from Palaeozoic to early Lower Pliocene; 5) it planated the tectonic structures developed in earlier times; 6) it is at places buried under continental and marine deposits younger than late Lower Pliocene; 7) the PS was eroded in a much shorter time than is usually assumed; 8) the PS was modeled during the climatic amelioration that generated the Late Lower Pliocene transgression and largely corresponds to a plain of marine erosion; 9) after the end of Lower Pliocene it was uplifted and deformed by very limited re-activation of thrusts; 10) since the Lower Pleistocene it was displaced by high angle normal faults. [...
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