Investigation of the structural control of a deltaic valley with geophysical methods. The case study of Pineios river delta (Thessaly, Greece)

Abstract

The current study aims to clarify the structural regime of the deltaic valley of Pineios river (Thessaly, Greece). The structural control of a deltaic area is usually a crucial parameter for its Palaio-geographical evolution and the latter needs to be clear for the contemporary conservation of such a sensitive ecotope environmentally. The investigation of the concealed subsurface tectonic structures was accomplished through the combined interpretation of gravity measurements, VES and TEM soundings. The standard gravity data reduction has been carried out and the residual anomaly was isolated with the contribution of the Fourier filters. The Euler deconvolution has been applied, providing the corresponding depth solutions between 159.8 and 1716.6 m. In the context of the qualitative interpretation, we produced several structural maps (THDR, VDR, Tilt and Theta) in order to enhance the edges of density sources that may reflect fault zones. Severe indications for the delineation of fault zones of the area were provided by these maps. Moreover, 3D density models of the area have been constructed illustrating the subsurface density distribution, up to depths of 3370 m. A main zone of lower densities in the central part of the delta has been revealed, surrounded by three zones of higher densities. Afterwards, the densities of the majority of the existing geological formations were determined with laboratory measurements from geological specimens. Therefore, three geophysical-geological profiles have been constructed, based not only on the gravity modelling but also on the geological interpretation of the geoelectrical layered models from the VES and TEM measurements. In conclusion, concealed and unknown tectonic structures of the Pineios deltaic valley have been identified beneath the surface.