Geophysical Investigation of Hydrogeological Conditions and Salination Processes at the Marathon - Kao Souli Basin (NE Attica, Greece)

This work presents the results of gravity, TEM and geological surveys conducted in the area of Marathon - Kato Souli Plain, as part of an effort to study its hydrogeological characteristics. The gravity survey offered a rather detailed image of the alpine basement and together with surface geological observations, insight into the post-alpine tectonic processes that have controlled the development of the area. The TEM survey produced detailed three-dimensional images of the aquifer systems and salination conditions. The results have shown that (a) the alpine basement is located much deeper than previously thought and, (b) that the sea water intrusion takes place both near sea level and at depth. The depth and morphology of the alpine basement are believed to have been fashioned by faults that either have not been active during the Quaternary, or are buried under thick terrestrial and alluvial deposits. Sea water intrusion forms at least two distinct salination horizons, presumably as a result of intersecting faulting structures that facilitate horizontal and vertical transportation of sea water between permeable formations. The vertical alternation of permeable-impermeable rock formations may be attributed to (alpine) folding, which results in vertical repetition of the same lithological units, in this case karstified marbles.