12 research outputs found
Educational software bundle for studying magnetotelluric theory and specific geoelectric structure models
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
Groundwater resource of the Geropotamos coastal aquifer of Crete, Greece: hydrochemical and isotopic analysis.
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
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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