SEDIMENTOLOGICAL AND GEOPHYSICAL OBSERVATIONS IN THE DELTA PLAIN OF SELINOUS RIVER, ANCIENT HELIKE, NORTHERN PELOPONNESUS GREECE

Fine and coarse grained lithofacies and depositional environments were distinguished in Selinous River delta plain, from sediment cores using an Eijkelkamp percussion corer with barrel windows. The sedimentary sequence of deltaic plain deposits of Selinous River mostly consists of fine lithofacies interbedded occasionally with conglomerate facies. Fine grained lithofacies based on sediment types, structure, color, as well as contact depths and bed characteristics were interpreted as floodplain, crevasse splay, back swamp / fresh water swamp, permanent shallow fresh water lake and ephemeral fresh water lake facies. The coarse grained lithofacies consists of pebble - conglomerates and were interpreted as paleochannels. The Time-Domain Electromagnetic technique, (TEM) was applied in order to define the spatial distribution of lenses of conglomerates, palaeochannels and fine grained sedimentary material to be recognised, at a depth up to 35m. Both the sedimentological and geophysical approaches, in combination with the available geological and geomorphological data of the area, can provide information about the evolution, existence and the geometry of paleochannels of the Selinous River flood plain, and the paleoenvironment of the area of the ancient Helike

Geophysical and geochemical study of geropotamos aquifer in the north-central coast of crete

The geological setting of Geropotamos aquifer on the north-central coast of Crete, Greece, is considered complex, while the local tectonic regime of the study area is characterized by two sets of faults orientated NW-SE and NE-SW. Investigation of the aquifer using the Transient ElectroMagnetic method (TEM) has resulted initially in 1D models of geoelectric structures and a final 3D geoelectrical model was constructed, depicting the zones of salination of groundwater in the aquifer. Groundwater samples were analysed and the most important chemical parameters were determined to provide an independent dataset for comparison with the TEM results, while Groundwater Quality Maps were produced. TEM and geochemical data correspond and provide verification of the TEM approach. As a result, saline intrusion is likely to occur along fractures in a fault zone through bedrock, and this work emphasises the critical role of fracture pathways in salination problems of coastal aquifers

The basement structure below the peat-lignite deposit in the Philippi sub-basin (Northern Greece) inferred by electromagnetic and magnetic methods

During 2009 and 2010 electromagnetic (EM) soundings and a high-resolution magnetic survey were conducted to study the deeper structure of the peat-lignite deposit in the Philippi sub-basin in Northern Greece. The primary intention of investigating the basement structure of the Philippi sub-basin is to propose the ideal location for a deep and continuous paleoclimate drill site. Data were collected along a 12 km transect (NNE-SSW) through the largest extension of the basin from Krinides at the North to Eleftheroupolis at the South. We used a combined set of Radiomagnetotelluric (RMT), Time Domain Electromagnetic (TEM) and Audiomagnetotelluric (AMT) soundings to derive a 2D model of the electrical resistivity distribution versus depth using a joint inversion approach. This model was then cross correlated with a 2D forward model of magnetic anomaly data. The magnetic survey detected strong anomalies in the North that appeared to have been generated by the Philippi granitoid pluton. All three individual data sets support each other and have jointly been analyzed. From this study we yield an asymmetric graben model of the basin structure that shows maximum thickness (ca. 500 m) in the northern part of the basin leading to a reduction of the thickness to the South. The interface between the basin fill and the bedrock ascend steeply in the North. The overall assessment of the deeper basin structure reveals a detachment system that is in good accordance with previous findings. (C) 2015 Elsevier B.V. All rights reserved

Geophysical and geochemical study of geropotamos aquifer in the north-central coast of crete, Greece. Conference poster at Near Surface Geoscience 2014,

The geological setting of Geropotamos aquifer on the northcentral coast of Crete, Greece, is considered complex, while the local tectonic regime of the study area is characterized by two sets of faults orientated NW-SE and NE-SW. Investigation of the aquifer using the Transient ElectroMagnetic method (TEM) has resulted initially in 1D models of geoelectric structures and a final 3D geoelectrical model was constructed, depicting the zones of salination of groundwater in the aquifer. Groundwater samples were analysed and the most important chemical parameters were determined to provide an independent dataset for comparison with the TEM results, while Groundwater Quality Maps were produced. TEM and geochemical data correspond and provide verification of the TEM approach. As a result, saline intrusion is likely to occur along fractures in a fault zone through bedrock, and this work emphasises the critical role of fracture pathways in salination problems of coastal aquifers.Operational Program "Education and Lifelong Learning" and is cofinanced by the European Union (European Social Fund) and Greek national fund

Geochemistry and quality of the groundwater from the karstic and coastal aquifer of Geropotamos River Basin at north central Crete, Greece.

In Geropotamos River Basin, located on the north-central part of Crete, Greece, two main factors were believed to be affecting the geochemistry of the ground- water with high salt contents: seawater intrusion and/or Miocene evaporates. To identify the origin of the high salinity in groundwater, a hydrogeochemical and isotopic study was performed. Water samples from 22 wells and 2 springs were analyzed for physico-chemical parameters, major ions analysis, as well as stable isotopes (d18O, dD). From the present survey, in which detailed hydrogeo- chemical investigation was conducted, the uncertainty of the contamination sources was decreased in the northern part of Geropotamos Basin. The results complement the scenario in which seawater and the widespread human activities are the principal sources of groundwater con- tamination. Moreover, the results of the stable isotopes analyses (d18O and dD) support the same hypothesis and make seawater intrusion the most probable cause for the highest salinity waters. It is indicated that saline intrusion is likely to occur along fractures in a fault zone through otherwise low-permeability phyllite–quartzite bedrock, which demonstrates the critical role of fracture pathways in salination problems of coastal aquifers

Groundwater high salinity in Geropotamos basin (Crete, Greece): sea water intrusion or Miocene Evaporites water interaction processes?

The aim of the study is to determine the origin of the high salinity groundwater of Geropotamos carbonate aquifer, located in an important touristic and agricultural area, on the central-northern coast of Crete (Greece). The main aquifer is composed by fractured and karstic carbonate rocks of Tripolis and Ionian tectonic nappes. Suggestions that Miocene Evaporites led to groundwater salinization were implied from previous studies, but they were unconfirmed. Water samples from 22 wells and 2 springs were analysed. The water temperature ranges between 18.1 and 22.9°C and the pH values ranging from 6.7 to 8.07 (slightly basic water). Cl, Ca, Na, HCO3 and SO4 concentrations are generally higher than Mg and K. The hydrogeochemical results showed different levels of mixing between a shallow end-member with bicarbonate-alkaline composition due to the leaching of carbonates rocks, and deeper fluids rich in Na and Cl. The Cl and Na contents are well correlated (r2=0.996) with an average Na/Cl ratio of 0.3, which is lower than Tyrrhenian Sea ratio (Na/Cl=0.56) and the dissolution of halite (Na/Cl=1) as well. The different Na/Cl ratio can be explained either by a depletion of Na, due to anionic exchanges processes with Ca between water and clay minerals, occurring in study area, or because of high salinity of the Cretan Sea (high Cl values). From this study we inferred that the sea water intrusion is the main contamination source to the aquifer, probably caused by increased over-pumping