1,721,001 research outputs found
CONTRIBUTION OF SEISMIC PROFILES, HISTORICAL MAPS, AND DIGITAL ELEVATION MODEL TO DEFINE BURIED GEOMORPHOLOGICAL FEATURES IN THE VENICE LAGOON SUBSOIL (ITALY)
No full textRecently, the integrated analysis of Very High Resolution Seismic (VHRS) profiles, satellite images, aerial photographs, maps, and topographic/bathymetric data has given an important contribution to the identification of buried geomorphological features in the Venice lagoon subsoil down to about 30 m b.s.l.. Investigations allow to attribute these features to the Late Pleistocene and the Holocene and to point out their relation with the evolution of the lagoon basin.
Results of this study are also assuming great importance in relation to coastal environmental problems. Relict sandy geomorphological features, characterized by high permeability, act as preferred pathways for groundwater flow and solute transport, enhancing saltwater intrusion in the watershed (Carbognin & Tosi, 2003; Carbognin et al., 2005; Pousa et al., 2007). Furthermore, salinization process can also trigger land subsidence induced by clayey particles rearrangement (Meade, 1964).
In addition, the different kinds of deposits that characterize geomorphological features are responsible for a differential lowering of the territory (Teatini et al., 2005).
Aerial photograph and satellite image interpretations, analysis of historical and recent maps, field surveys, and topographic/bathymetric investigations were first used to identify the main buried and surface geomorphological features. Afterwards, an important contribution to the present study was given by a single channel VHR seismic system, optimized for surveys in shallow water less than 1 m depth (Brancolini et al., 2006; Brancolini et al., 2007).
Seismic profiles were calibrated and validated using geological information obtained from existing cores.
The detailed reconstruction of the seismic-morpho-stratigraphic units present in the subsoil of the Venice Lagoon is still in progress. It is obtained integrating results of the investigations previously described with sedimentological, stratigraphic, geotechnical, mineralogical, textural, and paleoenvironmental data, and 14C dating (Serandrei Barbero et al., 2006; Tosi et al., 2007a; Tosi et al., 2007b).
The combined interpretation of results obtained from remote sensing investigations, topographic/bathymetric measurements, VHRS surveys, and analysis of multidisciplinary geological data allowed the discovery and characterization of buried paleoriver beds, ancient tidal channels, and paleobeach ridges and pointed out the relation among geomorphological features occurring in the lagoon basin and in the watershed.
In fact, most of the features recognized in the mainland, which apparently come to an end in correspondence to the lagoon margin, continue into the lagoon basin, where their identification is made difficult by the presence of water and by depositional/erosive processes active in this kind of environment.
Data show that relict geomorphological features composed of high permeability deposits provide the hydraulic connection between freshwater aquifers and the sea. In particular, results of the present study point out that well developed paleoriver systems, intersecting the southern lagoon margin and the nearby coastline and characterized by permeable sediments, represent preferential way of communication among waters having different salinity. By contrast thick silty-clayey layers preclude the salty pollution in the aquifers from the lagoon and the sea.
As pointed out close to the lagoon margin (Rizzetto et al., 2003), the different kinds of deposits, related to the presence of distinct geomorphological features, contribute to the differential lowering of the lagoon basin (Teatini et al., 2005). In particular, organic soils correspond to highly sinking areas, whereas sandy-silty sediments, which constitute fluvial and beach ridges, are more stable.
Future investigations have to be addressed to the quantitative geomorphological analysis aimed to know the past hydrologic conditions of the drainage systems, and to analyze the formative processes that control the morphological setting and evolution of lowland fluvial river and tidal creek systems.PublishedMunich, Germany6A. Monitoraggio ambientale, sicurezza e territorioope
CONTRIBUTION OF SEISMIC PROFILES, HISTORICAL MAPS, AND DIGITAL ELEVATION MODEL TO DEFINE BURIED GEOMORPHOLOGICAL FEATURES IN THE VENICE LAGOON SUBSOIL (ITALY)
No full textRecently, the integrated analysis of Very High Resolution Seismic (VHRS) profiles, satellite images, aerial photographs, maps, and topographic/bathymetric data has given an important contribution to the identification of buried geomorphological features in the Venice lagoon subsoil down to about 30 m b.s.l.. Investigations allow to attribute these features to the Late Pleistocene and the Holocene and to point out their relation with the evolution of the lagoon basin.
Results of this study are also assuming great importance in relation to coastal environmental problems. Relict sandy geomorphological features, characterized by high permeability, act as preferred pathways for groundwater flow and solute transport, enhancing saltwater intrusion in the watershed (Carbognin & Tosi, 2003; Carbognin et al., 2005; Pousa et al., 2007). Furthermore, salinization process can also trigger land subsidence induced by clayey particles rearrangement (Meade, 1964).
In addition, the different kinds of deposits that characterize geomorphological features are responsible for a differential lowering of the territory (Teatini et al., 2005).
Aerial photograph and satellite image interpretations, analysis of historical and recent maps, field surveys, and topographic/bathymetric investigations were first used to identify the main buried and surface geomorphological features. Afterwards, an important contribution to the present study was given by a single channel VHR seismic system, optimized for surveys in shallow water less than 1 m depth (Brancolini et al., 2006; Brancolini et al., 2007).
Seismic profiles were calibrated and validated using geological information obtained from existing cores.
The detailed reconstruction of the seismic-morpho-stratigraphic units present in the subsoil of the Venice Lagoon is still in progress. It is obtained integrating results of the investigations previously described with sedimentological, stratigraphic, geotechnical, mineralogical, textural, and paleoenvironmental data, and 14C dating (Serandrei Barbero et al., 2006; Tosi et al., 2007a; Tosi et al., 2007b).
The combined interpretation of results obtained from remote sensing investigations, topographic/bathymetric measurements, VHRS surveys, and analysis of multidisciplinary geological data allowed the discovery and characterization of buried paleoriver beds, ancient tidal channels, and paleobeach ridges and pointed out the relation among geomorphological features occurring in the lagoon basin and in the watershed.
In fact, most of the features recognized in the mainland, which apparently come to an end in correspondence to the lagoon margin, continue into the lagoon basin, where their identification is made difficult by the presence of water and by depositional/erosive processes active in this kind of environment.
Data show that relict geomorphological features composed of high permeability deposits provide the hydraulic connection between freshwater aquifers and the sea. In particular, results of the present study point out that well developed paleoriver systems, intersecting the southern lagoon margin and the nearby coastline and characterized by permeable sediments, represent preferential way of communication among waters having different salinity. By contrast thick silty-clayey layers preclude the salty pollution in the aquifers from the lagoon and the sea.
As pointed out close to the lagoon margin (Rizzetto et al., 2003), the different kinds of deposits, related to the presence of distinct geomorphological features, contribute to the differential lowering of the lagoon basin (Teatini et al., 2005). In particular, organic soils correspond to highly sinking areas, whereas sandy-silty sediments, which constitute fluvial and beach ridges, are more stable.
Future investigations have to be addressed to the quantitative geomorphological analysis aimed to know the past hydrologic conditions of the drainage systems, and to analyze the formative processes that control the morphological setting and evolution of lowland fluvial river and tidal creek systems.PublishedMunich, Germany6A. Monitoraggio ambientale, sicurezza e territorioope
Very high resolution seismic surveys in the lagoon and gulf of Venice shallow waters
No full textWithin the framework of the geological mapping of the Venice area (CARG Project: Map Sheet 128 “Venezia” and Map Sheet 148-149 “Chioggia-Malamocco”) a very high resolution seismic survey (VHRS) was carried out to correlate data from hundreds of cores with the main aim to map the depth of the Late Pleistocene and Holocene unconformity (Brancolini et al., 2005; Rizzetto et al., 2005; Tosi et al., 2006a,b). Due to logistic and technical limits, the acquisition of seismic survey in the Venice Lagoon was restricted to the channels with more of 5 m water depth, most of them artificial or dredged. A new survey, with the aim to extend the VHRS surveys to the shallow water, such as the tidal flats, is in progress within the Co.Ri.La. Project framework (3.16 Subproject). The Co.Ri.La 3.16 Subproject is based on an acquisition system installed on a boat with a very shallow draught. The new survey will allow the detection and mapping of many interesting geological-geomorphologic structures, i.e. paleoriver beds, ancient lagoon channels and shoreline ridges, that are like-outcropping, and that have been only partially recognized in the previous surveys.PublishedBarcelona (Spain)7A. Geofisica di esplorazioneope
Very high resolution seismic surveys in the lagoon and gulf of Venice shallow waters
No full textWithin the framework of the geological mapping of the Venice area (CARG Project: Map Sheet 128 “Venezia” and Map Sheet 148-149 “Chioggia-Malamocco”) a very high resolution seismic survey (VHRS) was carried out to correlate data from hundreds of cores with the main aim to map the depth of the Late Pleistocene and Holocene unconformity (Brancolini et al., 2005; Rizzetto et al., 2005; Tosi et al., 2006a,b). Due to logistic and technical limits, the acquisition of seismic survey in the Venice Lagoon was restricted to the channels with more of 5 m water depth, most of them artificial or dredged. A new survey, with the aim to extend the VHRS surveys to the shallow water, such as the tidal flats, is in progress within the Co.Ri.La. Project framework (3.16 Subproject). The Co.Ri.La 3.16 Subproject is based on an acquisition system installed on a boat with a very shallow draught. The new survey will allow the detection and mapping of many interesting geological-geomorphologic structures, i.e. paleoriver beds, ancient lagoon channels and shoreline ridges, that are like-outcropping, and that have been only partially recognized in the previous surveys.PublishedBarcelona (Spain)7A. Geofisica di esplorazioneope
Weak Underwater Signals’ Detection by the Unwrapped Instantaneous Phase
Full text linkIn marine seismic surveys, weak signals can be overlaid by stronger signals or even random noise. Detecting these signals can be challenging, especially when they are close to each other or partially overlapping. Several normalization methods have already been proposed, but they often lead to distortion. In this paper, we show that the unwrapped instantaneous phase of the associated analytical signal is an effective detection tool and validate it using synthetic and real data examples. This approach does not require user-defined parameters and therefore does not introduce personal bias in the results. We show that weak signals from submarine fluid plumes can be successfully detected by seismic surveys. These plumes can reveal anomalies in shallow sediments such as near-surface gas pockets and soft formations, which can severely affect offshore structures such as platforms and wind farms
The subsoil architecture of the Lagoon and Gulf of Venice (Italy) by very high resolution seismic surveys in shallows
No full textThe Project “Application of innovative of very high resolution seismic methodologies in shallow waters aimed at the study of the subsoil of the Venice Lagoon” allowed the characterization of the Late Pleistocene and Holocene depositional sequences with a detail, that has never been reached in the past.
A boat, particularly suitable for very high resolution seismic survey in shallow water (less than 1 m deep) has been fully equipped and tested. It allowed to carried out surveys of specific areas of the Lagoon that have never been investigated in the past. Moreover a seismo-stratigraphic model of the lagoon and gulf of Venice subsoil has been performed. The seismic acquisition system allowed to investigate the subsoil down to 30-40 m deep.
The new data provided significant geological features related to the Late Pleistocene and Holocene evolution of the investigated areas: the southern lagoon, the Lido and Chioggia inlets and part of the shelf of the Gulf of Venice.PublishedVenice, Italy7A. Geofisica di esplorazioneope
The subsoil architecture of the Lagoon and Gulf of Venice (Italy) by very high resolution seismic surveys in shallows
No full textThe Project “Application of innovative of very high resolution seismic methodologies in shallow waters aimed at the study of the subsoil of the Venice Lagoon” allowed the characterization of the Late Pleistocene and Holocene depositional sequences with a detail, that has never been reached in the past.
A boat, particularly suitable for very high resolution seismic survey in shallow water (less than 1 m deep) has been fully equipped and tested. It allowed to carried out surveys of specific areas of the Lagoon that have never been investigated in the past. Moreover a seismo-stratigraphic model of the lagoon and gulf of Venice subsoil has been performed. The seismic acquisition system allowed to investigate the subsoil down to 30-40 m deep.
The new data provided significant geological features related to the Late Pleistocene and Holocene evolution of the investigated areas: the southern lagoon, the Lido and Chioggia inlets and part of the shelf of the Gulf of Venice.PublishedVenice, Italy7A. Geofisica di esplorazioneope
Geophysical survey to study active and capable faults in Friuli Venezia Giulia: the example of the Maniago thrust (Meduno, NE Italy).
No full textThree-dimensional analysis of the Plio-Pleistocene seismic sequences in the Venice Lagoon (Italy)
No full textIntegrated seismic and well data provide for the first time a picture of the geological evolution of the Venice area over the last 5 Ma and a 3D subsoil model, which is fundamental to prediction of the anthropogenic uplift of Venice by seawater injection. A Pliocene southward prograding complex formed a shelf–slope system, whereas subsidence related to the Apennine foredeep development led to the establishment of a Early Pleistocene deep-water environment, favouring the
accumulation of a thick turbidite succession. The NE progradation of the palaeo-Po river delta during the Middle Pleistocene promoted a drastic environmental revolution, followed by the deposition of cyclothems linked to glacio-eustatic changes
PRELIMINARY STUDY OF GEOMORPHOLOGICAL FEATURES DISCOVERED IN TIDAL FLATS OF THE VENICE LAGOON BY VHR SEISMIC SURVEYS
No full textAbstract.
Available sedimentological, stratigraphic and bathymetric data, historical maps and a number of new Very High Resolution Seismic (VHRS) surveys acquired in the lagoon shallows were processed. Collected data allowed the characterization of the geomorphological setting at regional scale, whereas new VHRS data locally provided details of feature extent.
In particular the new VHRS surveys pointed out, for the first time, the occurrence and, in some cases, the evolution of buried and surface morphological features found in the lagoon shallows.
Riassunto.
In questo studio sono stati elaborati i dati sedimentologici, stratigrafici, batimetrici e cartografici disponibili pregressi e una serie di nuovi rilievi sismici ad altissima risoluzione eseguiti sui bassi fondali lagunari. I dati raccolti hanno consentito di individuare le strutture geomorfologiche a scala regionale mentre quelli di nuova acquisizione hanno fornito una serie di dettagli locali delle stesse strutture.
In particolare, i nuovi dati sismici hanno permesso di individuare per la prima volta la presenza di elementi geomorfologici nei bassifondi lagunari ed in alcuni casi di caratterizzare la loro evoluzione spazio-temporale.PublishedVenice, Italy7A. Geofisica di esplorazioneope
- …
