VERBI VEnice Research BIbliography

This unconformity represents the boundary between the LST and the Holocene Transgressive System Tract (TST) or, mainly in the inner part of the lagoon, the High System Tract (HST), depending on the hiatus.

The upper layer of the LST is often characterized by the occurrence of a clay rich deposit, historically called “caranto” by the Venetians, that shows pedogenesis evidence due to its subaerial exposure.

Since its formation, the morphology of the Venice Lagoon underwent a rapid evolution, that became much more intensive in the last centuries, due to the impact of human activities, e.g. defences for the islands, digging of the channel, dumping of the sediments etc. (Albani et al., 1984, Albani et al., 1995).

The knowledge of the sediment dynamics, with the identification of erosional areas, the sedimentation rate and the flux of sediments, is a fundamental issue for the knowledge of the lagoon evolution and the impact assessment for engineering works. (Umgiesser et al., 2005; Amos et al., 2005).

Our knowledge of the geological settings of the upper Pleistocene and Holocene deposits of the Venice area mainly results from analyses based on cores that, even if collected in a large number, give only local information (Tosi, 1994a; Tosi 1994b). On the other hand, seismic surveys, which can offer the possibility to correlate layers between cores, were rarely carried out in the past because of poor results due to the extreme environment of the lagoon, i.e. very shallow water (McClennen et al., 1997). In recent years, within the CARG Project, the very high-resolution (VHR) seismic technique has been updated and seismic surveys have been performed in the lagoon channels, and offshore, to a minimum water depth of 5 m. (Baradello et al., 2002; Tosi et al., 2005a and 2005b).

In order to provide new geological knowledge on the Venetian architecture subsoil, within the Co.Ri.La. Project, a VHR seismic system has been adapted for very shallow water, i.e. 1-2 m depth, and is currently under installation on a dedicated boat. Preliminary surveys have been carried out with this new technique in the lagoon, sea and Sile River. This paper reports and discusses these results and focuses on the characterization of the three main seismic units detected, which relate to the upper Pleistocene Low System Tract (LST), the Holocene Transgressive System Tract (TST) and the Holocene High System Tract (HST). In particular, the target of the investigation was the recognition within these units of features, such as filled paleo-river beds and lagoon channels, ancient littoral ridges and beach rock formations.