S. Dilalos

Adumbration of Amvrakia’s spring water pathways, based on detailed geophysical data (Kastraki - Meteora)

The Amvrakia spring is located at the bottom of Meteora pillars and more specifically near the village of Kastraki (Kalambaka municipality). It is a seasonal spring since it functions only during the wet period. The Meteora conglomerates which dominate the area are characterized by large discontinuities creating a network of groundwater pathways above the impermeable strata of the underlying marls. The research targets was to define these water pathways in order to understand the mechanism of Amvrakia spring, by mapping the exposed discontinuity network and define their underground extension with the contribution of geophysical techniques. Electrical Resistivity Tomography (ERT) and Very Low Frequency (VLF) methodologies were applied. The VLF method is indicated for the detection of water-bearing fracture zones, but before the application of their filters they had to be processed for topographic corrections, as the area had not smooth relief. Five (5) VLF profiles were conducted with different directions around the spring’s area, in order to detect possible conductive zones in the conglomerates surrounding the study area. Moreover, two (2) ERT sections of a total length of 140m were carried out, parallel to existent VLF sections, for cross-checking the geophysical information. Both techniques revealed important conductive zones (<200 Ohm.m) from the south-eastern Meteora conglomerate pillars, possibly interpreted as discontinuities filled with water feeding the spring.

Application of Geoelectrical Techniques in the Investigation of a Coastal Sand Dune Field

A geophysical research was carried out to investigate the lithostarigraphic substratum characteristics of the dune field of the central Kyparissiakos Gulf (W. Peloponnese, Greece), which is characterised by the presence of four dune lines. For this purpose, the geophysical techniques of Electrical Resistivity Tomography (ERT) and Vertical Electrical Soundings (VES) were applied, along with detailed morphological mapping and the collection of geological and geomorphological information. The processing of the geophysical data that were collected from two ERT soundings, perpendicular to the general direction of the dune lines, and seven geoelectrical soundings revealed four geoelectrical layers with the two surficial resistive layers adumbrating the extent and thickness of the four sand dune ridges and the associated slags. The third layer, corresponding to the underlying geoelectrical formation of 50-75 Ohm.m, is interpreted as a layer of transgressive Holocene deposits saturated with fresh water, while the deepest geoelectrically identified layer seems to correspond to the “Neda” formation, which consists of marls, sandy marls and conglomerates. It is concluded that the combined application of the aforementioned techniques has the potential to provide valuable data for the investigation of complex coastal depositional environments.

A Geophysical Insight for the Occurrence of Mediterranean Temporary Ponds on Mts. Oiti and Kallidromo (Greece)

A geophysical survey was performed at selected locations of Mt. Oiti and Mt. Kallidromon characterized by the hosting of priority habits of Mediterranean temporary ponds and the threatened plant species of Veronica oetaea, in order to understand the geoenvironment and contribute to the conservation of biodiversity. Primarily, the formation of these seasonal ponds, where Veronica oetaea occurs, seems to depend exclusively on the local hydrogeological regime. Thus, we investigated the subsurface structure of “Livadies” and “Nevropolis” ponds with the application of Electrical Resistivity Tomography for high accuracy information and Vertical Electrical Sounding for deeper data acquisition. Four ERT sections and 15 geoelectrical soundings in total were carried out. The combined results of their processing revealed differences at the geological structure beneath the ponds locations. At “Livadies” pond (Mt. Oiti), two geoelectrical layers were distinguished both corresponding to a folded flysch succession, contributing to the formation of this pond. On the contrary, at “Nevropolis” pond two geoelectrical layers were identified and interpreted as a surficial soil deposit stratum covering the geomorphological karst structure of a polje, created on the underlying limestones. The combined geophysical research offered significant data for the formation and the hydrogeological status of the priority habitats.