1,721,476 research outputs found
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
Tre nuovi trancianti in selce in Lombardia. Osservazioni tecniche, cronologice e culturali
No full textMiddle-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. [...
Guado San Nicola acheulean site: preliminary remarks on the litho-, morpho- and pedo-stratigraphical setting
No full textThe Last Interglacial Pedocomplexes in the litho- and morpho-stratigraphical framework of the Central-Northern Apennines (Central Italy)
No full textRecently in Italy, a great deal of effort has been devoted to the mapping of Quaternary continental deposits. Several Unconformity Bounded Stratigraphic Units (UBSU) have been defined. The unconformities indicate important phases of changing dynamics linked to Quaternary climatic changes, and have been related to valley downcutting simultaneous with paleosol formation during interglacials. However, glacial periods are characterised by deposition of thick continental sequences. We suggest that the UBSU's belonging to the late Middle Pleistocene (MIS 6) and Late Pleistocene can also be defined under a pedostratigraphic point of view. Locally at the top of the UBSU attributed to MIS 6, buried or relict paleosols are preserved. The paleosols developed in calcareous fluvial and moraine gravels with minor flints. The pedocomplexes are made of three paleosols separated by erosion surfaces and/or stonelines. The older paleosol (MIS 5e) is severely truncated and is characterised by a Ck horizon overlain by strongly leached reddish Bt horizons with flinty rock fragments (with a diagnostic wavy lower boundary). In some sites, subsequent secondary precipitation of carbonates transformed this horizon into a Btk. This paleosol is buried by a younger paleosol (MIS 5c) with less leached reddish Btk horizons, quartz of aeolian origin, and very small and scarce calcareous clasts. The main pedofeatures are associated with colluvial processes, biological activity, and carbonate precipitation. This paleosol is also truncated and buried under a similar paleosol (MIS 5a). Therefore, the lower paleosol of the pedocomplex can be attributed to the Eemian, and constitutes a valid marker for the definition and mapping of the underlying and overlying sedimentary units. In other parts of the Apennines, no sedimentary units have been found that correspond to the unconformities separating different pedostratigraphical units. In order to map the different UBSU's, due to the poor lateral continuity of the preserved paleosols, morpho- and litho-stratigraphical investigations and correlation are always recommended. (c) 2006 Elsevier Ltd and INQUA. All rights reserved
The southern east-Tiber Basin (Spoleto, Central Italy): geology and stratigraphy of the Plio-Pleistocene sediments
No full textFluvial architecture and dynamics in rising mountain chains and related basins; tectonic, climatic influence and human impact: The FLAG-SEQS (Fluvial Archive Group – Subcommission for European Quaternary Stratigraphy) Siena Meeting
No full textThermobarometric evolution and metasomatic processes of upper mantle in different tectonic settings: evidence from spinel peridotite xenoliths
No full textPetrological studies of spinel peridotite xenoliths provide information on the nature and physico-chemical evolution of the upper mantle and its variability on a regional scale, in both oceanic and continental environments. Thermobarometric estimates based on phase equilibria and CO2 inclusions indicate different pressure - temperature equilibration histories for xenoliths from different tectonic settings. In spinel peridotite xenoliths from all tectonic settings, modal metasomatic processes are suggested by widespread pyrometamorphic textures in some cases associated with new phases such as amphibole or jadeitic Cr-endiopside. Chemical effects of metasomatism include variable enrichment of incompatible elements. The metasomatic agents can be envisaged as strongly alkaline H2O-CO2-rich silicate melts. In the case of Cape Verde, the widespread development of jadeitic Cr-endiopside is better accounted for by assuming a carbonatite melt as metasomatizing agent which progressively converte..
Quaternary evolution of the "Castelluccio di Norcia" basin (Umbro-Marchean Apennines, Italy)
No full textCastelluccio di Norcia basin is a Quaternary depression located in the southern part of the umbro-marchean apennines
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