National Technical University of Athens, School of Mining Engineering and Metallurgy, Zografou Campus, 15780 Athens, E-mail: gapo@metal.ntua.gr

Abstract: An integrated geophysical investigation including resistivity, gravity and SP measurements is used to reveal the overall tectonic status of the Sperchios River Valley, Central Greece, as well as the sedimentation of the valley at various depths in view of the geothermal status. Deep Schlumberger soundings are interpreted by 2D models and then used to constrain the density values in the corresponding gravity profiles. The combined interpretation of resistivity and gravity measurements suggests that the valley consists of deep sediments mainly of clayey origin and the valley fill reaches two kilometers beneath the Delta. The depth of the bedrock (which has ophiolite or flysch and limestone underneath) is controlled by some buried faults mainly of E-W strike. Other faults of NNW-SSE strike create some sinkings and uplifts in the bedrock relief. The interpretation of geophysical data verifies blocky shaped bedrock. Such a fault system in the southern part of the valley is also related to geothermal surface manifestations. Faults in the flysch give rise to a deep passage for geothermal fluids which reach the surface through geothermal circulation zones in the sediments detected by the SP method. The deposition of the Sperchios River and its torrents, and the tectonic activity (sinkings and uplifts in the bedrock detected by the whole geophysical survey), mainly affect character of the sedimentation (shown by resistivity interpretation) and river routes.