Electromagnetic methods for near-surface applications: a critical analysis of different investigation approaches

Collecting the information regarding the sedimentary patterns of ancient tidal channels and providing a better understanding of their influence on the morphodynamic evolution of the lagoon environment, requires an expensive process that involves high resolution sediment coding. In this work we discuss the methods and results obtained from the electromagnetic survey carried out in the northern Venice Lagoon. We investigated meander deposit using two different conductivity meters: a multi-coil sensor and a multifrequency one. The aim of this study was to reveal the lateral and vertical structure of the meander body. The interpretation of the geophysical data has been correlated with borehole analysis, carried out from five sediment cores collected on the site area. In addition, the information regarding the architectural structure of the point bar deposit observed in the channel, from two seismic profile shown in the literature, has been considered. The results show that this method allows us to identify a sand deposit buried in a mud-silty contest, that is not related with the point bar deposit identified with the tidal meander. Moreover, we demonstrated that the proposed geophysical technique, is not only rapid and non-invasive, but is also a successful tool in detecting strata architecture and the definition of its spatial distribution.