Donda, Federica

We investigated the spatial relationships among 18 known seismogenic faults and 1651 wells drilled for gas exploitation in the main hydrocarbon province of northern-central Italy, a unique dataset worldwide. We adopted a GIS approach and a robust statistical technique, and found a significant anticorrelation between the location of productive wells and of the considered seismogenic faults, which are often overlain or encircled by unproductive wells. Our observations suggest that (a) earthquake ruptures encompassing much of the upper crust may cause gas to be lost to the atmosphere over geological time, and that (b) reservoirs underlain by smaller or aseismic faults are more likely to be intact. These findings, which are of inherently global relevance, have crucial implications for future hydrocarbon exploitation, for assessing the seismic-aseismic behaviour of large reverse faults, and for the public acceptance of underground energy and CO2 storage facilities-a pillar of future low carbon energy systems-in tectonically active areas.

A new method merges conventional and quantitative biostratigraphic approaches, supported by magnetic polarity data, to develop a chronological framework for sediment core MD03-2595 retrieved on the continental rise off Wilkes Land, East Antarctica before proceeding to paleoceanographic and paleoclimatic analysis. This combined method helped to identify climatic cycles, highlight stratigraphic discontinuities and reworking, and assess regional sedimentological and diatom biostratigraphic evolution. Core MD03-2595 spans the last 0.8 Ma, from the Mid Pleistocene Transition (MPT) to the Early Holocene. A hiatus including Marine Isotope Stages (MIS) 19, 18 and 17 was identified, and a decreasing trend in sediment accumulation rates from MIS 16 to the Holocene was observed. This quantitative diatom biostratigraphic dataset, placed in its own sedimentological and paleomagnetic context, provides new information regarding the paleobiogeographic distribution and ecological responses of biostratigraphically significant diatom species, such as Thalassiosira elliptipora and T. fasciculata, for the Matuyama–Brunhes (M–B) transition, and Actinocyclus ingens, Hemidiscus karstenii and Rouxia spp. for the middle and late Pleistocene diatom biozonation.

The Venice Lagoon is characterized by a remarkable vertical and lateral variability of deposits, mainly produced by delta, tidal channels and sand bar migration. High resolution seismic surveys and coring analysis, carried out in the frame of the Co.Ri.La. research line 3.16, produced new insight in the evolution of the Venice Lagoon through the Holocene. Based on the new data, it has been possible, for the first time, to image and map the three main phases that characterized the formation and the evolution of the lagoon. Initially, the marine ingression, between 10,000 and 6,000 years B.P., produced the submersion by the Adriatic Sea of the Pleistocene alluvial plain. During this phase, longshore drift triggered the formation of the Venice palaeo lagoon. Then, the following sea level highstand recorded the predominance of sediment supply from rivers and the progressive advance of the coastline toward the sea. Finally, the more recent phase was characterized by the predominance of erosion and sediment exportation from the lagoon, as the consequence of human interventions on river mouths and inlets since historical time. These distinct phases are associated to sedimentary deposits with different geotechnical, sedimentological and geochemical characteristics, which play different roles in the erodibility of the sea floor and in the hydrogeological regime. In this paper we present the main results from the surveys carried between 2003 and 2006 in the southern portion of the lagoon, where the Holocene deposits reaches their maximum thickness.

Abstract. 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.

The 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.

Within 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.