Lake evolution since the bronze age in the lower Mincio river valley and the Forcello etruscan harbour (central Po plain) (original) (raw)
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Lake Patria is amesoaline coastal lagoon that develops along the coastal zone of the Volturno River plain (Campania, South Italy). The lagoon is a saline to brackish water body, ca. 2.0 long, and 1.5 km wide, with an average water depth of 1.5 m, reaching a maximum of ca. 3.0 m. The freshwater input into the lagoon is provided by a series of fresh to brackish water channels and small springs, landwards, while a permanent connection with the Tyrrhenian Sea is provided by a channel, 1.5 km long and a few meters wide. Drilling data from12 boreholes acquired in the study area indicate that Lake Patria is a man-modified remnant of a larger lagoonal area that developed during the last millennia along the Campania coastal zonewithin an alluvial delta system at the mouth of the paleo-Volturno River. Sedimentological and stratigraphic analyses of drill cores suggest that the lower Volturno delta plain developed in the last 6000 years. Depositional conditions during this period were dominated by flood-plain and alluvial plain settings, with transition to coastal bars and associated back-barrier coastal lagoons. Lake Patria started evolving at an early stage of the Volturno delta plain formation as a consequence of foreshore deposits damming-up by littoral drift. The first marine layers display a radiocarbon age of ca. 4.8 ka BP and overlie a substrate represented by volcaniclastic deposits, originated by the Campi Flegrei, and associated paleosols. The lagoonal succession cored at Lake Patria may be interpreted as the result of a dynamic equilibrium between marine influence and riverine input into the lagoonal systemthrough time, and has been tentatively correlatedwith the major climatic changes that occurred during Mid–Late Holocene. Insights into the recentmost evolution of the coastal lagoon of Lake Patria are provided by the GIS-based analysis of the physiographic changes of the region conducted on a series of historical topographic maps dating back to the early XVII century. Particularly, the superposition of historical cartography reveals the secular trends in the change of coastal environments and the role of human modification of natural habitats over the last 400 years.
The Upper Valdarno Basin stands out from the Neogene-Qua- ternary basins of the Northern Apennines given its outstanding fossil mammal record, good quality of natural and artificial outcrops and remarkable chronological control on the basin-fill succession. The present paper aims to summarize the stratigraphic and sedimento- logical studies focused on the Upper Valdarno Basin during the past decades, and integrate them with recent investigations. The Upper Valdarno Basin is located about 35 km SE of Florence between the Chianti Mountains and the Pratomagno Ridge. It consists of a main asymmetric tectonic depression filled with 550 m of Plio-Pleistocene fluvio-lacustrine deposits (Upper Valdarno Basin s.s.) and a minor basin known as the Palazzolo sub-basin. The Upper Valdarno Basin fill is made of three unconformity-bounded units, named Castel- nuovo dei Sabbioni (CSB), Montevarchi (VRC), Torrente Ciuffenna (UFF) synthems, whereas the Palazzolo sub-basin fill consists of the Fosso Salceto (OLC) and Torrente Ciuffenna (UFF) synthems. The Upper Valdarno Basin formed during Late Pliocene because of the tectonic damming of a northeastward flowing drainage. The early phase of basin development is recorded by the accumulation of flu- vial gravels in vallive settings, whereas the definitive of these streams damming caused the development of lacustrine conditions at about 3.1 Ma. The accumulation of deltaic sand fed from the SW margin caused the lake filling and stopped the deposition of the CSB Syn- them. Before 2.58 Ma, a tectonic phase caused uplift of the basin and partial erosion of the CSB deposits. Deposition of the lower part of the VRC Synthem occurred during a marked basin broadening and accumulation of alluvial fan successions, which were capped by aeolian-reworked alluvial sand deposited at about 2.5 Ma. At about 2.3 Ma, a new deformative phase caused further basin widen- ing, erosion along the SW margin and development of a small lake in the central areas. Deposition of the upper part of the Montevarchi Synthem started just after this tectonic phase and was characterized by development of axial fluvial drainage and marginal alluvial fans. During the Early Pleistocene (Olduvai Subchron, 1.95-1.78 Ma) a subsidence pulse promoted development of floodplain lakes and swamps in the axial part of the basin, where thick organic-rich mud were accumulated. During late Early Pleistocene the capture of the paleo-Arno River, which started to flow into the basin, caused the development of a marked unconformity. This unconformity was covered by fluvial and alluvial fan deposit in the axial part and along the margin respectively.
Méditerranée, 2005
This paper integrates geomorphological, archaeological and radiometric data to reconstruct the evolution of the Fortore River coastal plain and the Lesina Lake coastal barrier, in relation to the main seismic events, Middle-Late Holocene climate changes and the human impact which affected this area. The available data set indicates that the evolution of the coastal area can be subdivided into four main phases, separated by three strong earthquakes that struck this region during prehistorical and historical times. Furthermore, climate changes and human impact affected mainly the Fortore River dynamics and influenced at a smaller magnitude the evolution of the coastal plain and the strictly related coastal barrier.
Tectonostratigraphy of Lake Trasimeno (Italy) and the geological evolution of the Northern Apennines
Tectonophysics, 2010
Trasimeno, a~10 km diameter, shallow (b6 m deep) lake located in the Central Apennines (Italy) was investigated using an integrated geological/geophysical approach. Single-and multi-channel seismic reflection profiles were collected to reconstruct the geological history of the lake in connection with regional geo-tectonic evolution. Data from the lake, complemented by geological studies of the lake's surroundings, allowed us to recognize that its history is characterized by a rather continuous subsidence driven by normal faults that developed over pre-existing compressional structures. We found that the extensional tectonic regime affecting the entire sedimentary sequence up to the most recent deposits does not show important changes since the lake's formation (Middle-Late Pleistocene) and is probably responsible for its long-term preservation against sediment infill. Our data suggest that during Neogene-Quaternary times the Trasimeno depression developed as: i) a marine gulf in the continental shelf of the Tyrrhenian Sea (Early Pliocene); ii) a wide fluvial plain (Early Pleistocene); iii) a fresh-water lake filling a subsiding tectonic depression (Middle Pleistocene to present-day). Results of this study indicate that the Lake Trasimeno basin can be regarded as a rather efficient recorder of geological events; this might also be the case of other continental shallow-water basins, because these environments favor the acquisition of high-quality geophysical images of the subsurface, and could reveal high-resolution stratigraphic records not common in other continental environments.
To the northwest of the ancient city of Ostia, the analysis of cores revealed a stratigraphic sequence, which we interpret as the filling of a harbour basin. This basin, located at the west of the so-called "Palazzo Imperiale" presents seven characteristics: (1) The maximum depth is 6 m below the Roman sea level. This depth allowed any type of ship (even heavy tonnage) to access the harbour. (2) A chronostratigraphic gap at À6 m below Roman sea level suggests digging operations in the basin (or subsequent dredging) that have caused the loss of sedimentary archives. The filling consists of dark clays typical of a quiet environment but open to marine and river influences. (4) The dates at the base of this sequence give a range between the 4 th and the 2 nd century BC. (5) In the harbour sequence, a facies change at À2.5 m under the Roman sea level involves a change in the processes of sedimentation and/or operation. (6) No later than the beginning of the 1 st century AD, the thickness of the water column in the basin is less than 50 cm and seems to be caused by a massive siltation following a succession of floods of the Tiber. (7) This basin was thus already abandoned during the start-up of Portus.