Τμήμα Γεωλογίας (ΜΔΕ)
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- ItemOpen AccessA review on sediment samples from a deep hypersaline anoxic basin : Tyros
Τμήμα Γεωλογίας (ΜΔΕ)Νικητίδου, Αγγελική; Γεραγά, Μαρία; Γεραγά, Μαρία; Nikitidou, AngelikiThe Tyros basin is a presently deep hypersaline anoxic depression in the eastern part of the Mediterranean Sea. Its presence attributes to a combination of submarine dissolution of outcropping or subcropping evaporates (Messinian) which accumulate at the slopes of the basin and at its tectonic subsidence (pull-apart mechanism) that occurs in the western Strabos trench. Therefore, this unique environment consists of two major factors. The first one is a high density stagnant bottom-water column and the second is the preservation of the organic-rich sediments of the area due to the anoxic conditions. The core (TYRO5) that was retrieved from that basin had a total length of 285cm and comprises a complex lithostratigraphic sequence due to the strong geodynamic regime of the area. The analysis conducted on sediment samples from the core TYR05 included granulometry, mineralogy, micropaleontology, bulk geochemistry and total CHNS/organic carbon (TOC). The grain size distribution along with the planktonic foraminifera presents fluctuations which coincide with changes in the lithology of the core. The mineralogical composition of the sediments confirm the evaporate influence developed on the bottom of the basin, while both geochemistry and total CHNS/TOC verify the present anoxic conditions and the existence of organic-rich sediments. The synthesis of all the above analysis suggests that the sediment core consist mostly of sapropel to sapropelic layers and that it has a rather homogeneous character, because of its high re-sedimentation rate. Subsequently, it is indicated that the sapropel units refer to an S1 type, but further analyses are needed in order to be safely determine, such as radiocarbon dating C14 and stable isotopes of O, C.
- ItemOpen AccessAutomatic detection and spatial quantification of trawl-marks in sidescan sonar images through image processing and analysis
Τμήμα Γεωλογίας (ΜΔΕ)Γουρνιά, Χαρίκλεια; Παπαθεοδώρου, Γιώργος; Παπαθεοδώρου, Γιώργος; Κουτσικόπουλος, Κωνσταντίνος; Γεραγά, Μαρία; Gournia, CharikleiaBottom trawl footprints are a prominent environmental impact of deep-sea fishery that was revealed through the evolution of underwater remote sensing technologies. Image processing techniques have been widely applied in acoustic remote sensing, but accurate trawl-mark (TM) detection is underdeveloped. The paper presents a new algorithm for the automatic detection and spatial quantification of TMs that is implemented on sidescan sonar (SSS) images of a fishing ground from the Gulf of Patras in the Eastern Mediterranean Sea. This method inspects any structure of the local seafloor in an environmentally adaptive procedure, in order to overcome the predicament of analyzing noisy and complex SSS images of the seafloor. The initial preprocessing stage deals with radiometric inconsistencies. Then, multiplex filters in the spatial domain are performed with multiscale rotated Haar-like features through integral images that locate the TM-like forms and additionally discriminate the textural characteristics of the seafloor. The final TMs are selected according to their geometric and background environment features, and the algorithm successfully produces a set of trawling-ground quantification values that could be established as a baseline measure for the status assessment of a fishing ground.
- ItemOpen AccessBenthic plastic debris in Ionian Sea. How long until they degrade?
Τμήμα Γεωλογίας (ΜΔΕ)Αθανασοπούλου, Κωνσταντίνα Παρασκευή; Παπαθεοδώρου, Γεώργιος; Καραπαναγιώτη, Χρυσή; Γεραγά, Μαρία; Athanasopoulou, Konstantina ParaskeviThe ecological problems related to environmental pollution by synthetic polymers like plastics are one of the major concerns of the present days; especially because the degradation rate of the polymers is significally slow, which makes them extremely persistent. Unterstanding the surface alteration of plastics while in the marine environment assists to the understanding of the interaction between pollutant and plastic debris and estimating the duration of their existence in the marine environment. In the present study , polyethylene terephthalate bottles were collected from a submarine environment and analyzed with regard to environmental degradation. In order to estimate the period of existence of PETs in the marine environment, a temporal indication was used. Additionally, surface properties, for instance surface functional groups and surface topography are important indicators for the purpose of observing the degradation of plastic. A significant decrease in Fourier transform infrared peaks for eroded PETs were recorded; some native functional groups even disappear; or new -not typical for PETs- are created. Simultaneously, degraded PET surface was rough, uneven and occasionally, colonized by microorganisms. These surface properties were obtained due to degradation and could be used to explain the interaction between plastics, microorganisms and pollutants. Ultimately, the present research shows that plastic still exists for many decades after its generation. PET was found to degrade very slowly, as at least a decade is needed until the forming of a new chemical surface which would interact with pollutants or microorganisms.
- ItemOpen AccessBiogeochemistry and microbial ecology of shallow marine sediments from methane seeps, Katakolo Bay, Western Greece
Τμήμα Γεωλογίας (ΜΔΕ)Βαζιουράκης, Κωνσταντίνος-Μάριος; Παπαθεοδώρου, Γεώργιος; Κορμάς, Κωνσταντίνος; Teske, Andreas; Vaziourakis, Konstantinos-MariosAnaerobic oxidation of methane (AOM) and other hydrocarbons prevents methane emission from marine sediments into the atmosphere. This study tries to illuminate aspects of AOM investigating shallow marine core sediments from Katakolo bay (W. Greece), one of the vastest thermogenic gas seepage fields in Europe. Belonging to the central Ionian geotectonic zone of the external units of the Hellenides, Katakolo has attracted the interest of scientists due to the vast seepage occurring in the harbor and can be considered as a unique natural laboratory in studying O2 versus gas seepage by long term monitoring. In the terms of this master dissertation, a number of multidisciplinary methodologies was implemented in order to shed light on the key biogeochemical process and the microbial ecology of nearshore (less than eight meter water depth) organic carbon depleted silty sands. We combined pore-water geochemical measurements, bulk geochemical and mineralogical analyses with 16S rRNA sequencing-based community analysis for both Archaea and Bacteria and fluorescence in situ hybridization (CARD-FISH) to investigate and visualize the microbial communities in this environment. Although the sediments are highly disturbed by natural and anthropogenic activities at the port area, several geochemical proxies indicated the presence of recent and paleo-redox changes along the sediment cores. Congruent with the existence of a seep microbiome, a distinct microbial community shift was observed in deeper sediment horizons (25-35cm below seafloor). The archaeal community from surface sediments was characterized by Bathyarchaeia and the recently discovered, Woesarchaeota, whose metabolic potential is possible consistent with methanogenesis in hypoxic surface marine sediments. By contrast, in the deeper layer with methane as the dominant hydrocarbon, strictly anaerobic methane oxidation is likely the main process controlled by the governance of the clade of ANME-2c in conjunction with the presence of ethane and butane oxidizers. In the same depth, bacterial communities are characterized by the presence of Parcubacteria (Candidatus Moranbacteria). The latter coincides with the anoxic environment of the sediments but it differs from the typical governance of the sulfate reducing bacteria that were expected. Slight decrease of sulfate, formation of free sulfide and the presence of aggregates consisted of ANME-2c indicate the predominance of sulfate-coupled AOM in these anoxic shallow marine sediments.
- ItemOpen AccessCharacterization, provenance and statistical analysis of coarse clastic deposition in the Pindos foreland basin
Τμήμα Γεωλογίας (ΜΔΕ)Κοβάνη, Ανδριάνα; Kovani, AndrianaThis thesis integrates provenance and statistical data, along with published sedimentological results, applied on the Upper Eocene-Lower Oligocene submarine fan deposits in Pindos foreland basin. Twelve (12) outcrops were described and interpreted using facies analysis, conglomerate clast composition analysis, petrographic analysis, and statistical analysis. Sedimentological analysis had revealed that the studied deposits correspond to inner fan deposits. Facies analysis documented twelve (12) sedimentary facies that are grouped into two facies associations, conglomeratic channel fill deposits (FA1) and internal levee deposits (FA2). The internal levee deposits are also divided in two (2) sub-facies, the inner (FA2a) and the outer (FA2b) internal levee deposits. Conglomerate clast composition analysis suggests three sedimentary sources, a major limestone source and two (2) secondaries sources, one sandstone and one chert source. Petrographic analysis was performed, applying the Gazzi-Dickinson Point Counting method and the Cathodoluminence technique (CL). The Point Counting method confirms the existence of these three sedimentary sources and also suggests an additional low-grade metamorphic source, which is also confirmed by the Cathodoluminence analysis. Statistical analysis of clast lithology included principal component analysis (PCA) and cluster analysis and suggests three (3) groups of outcrops based on the lithology. The combination of statistical analysis and stratigraphic information indicated that sediment clast provenance within the basin was affected by increasing amounts of black chert, especially at the northern part of the study area. This deposition is interrupted by sandstone dominated flow episodes and at the later stages of sedimentation, at the southern part of the study area, sedimentation was characterized by increased inputs of carbonate and red chert abundances, probably sourced from Pindos orogene. The combined results of all these methodologies suggest that the major sediment provenance for the studied deposits was the Pindos orogen.
- ItemOpen AccessClimatology via applied satellite remote sensing : chlorophyll blooms in the North Aegean Sea
Τμήμα Γεωλογίας (ΜΔΕ)(2014-09-16) Γεωργακάς, Κωνσταντίνος; Παπαθεοδώρου, Γεώργιος; Χρόνης, Θεμιστοκλής; Παπαθεοδώρου, Γεώργιος; Φερεντίνος, Γεώργιος; Χρόνης, Θεμιστοκλής; Georgakas, KonstantinosThe current study focuses on the phenomenon, mostly accounted within the past recent time, of the algae blooms (chlorophyll burst) in the area of the North Aegean Sea. The study attempts to coincide and amplify the approach of Satellite Remote Sensing monitoring, as means of applied oceanographic methods, in order for possible seasonal, spatio-temporal trends of this phenomenon to be identified, thus making the correlation of the indices-variations, though interdisciplinary, to be explained to an extend plainly, in terms of ‘why’ and ‘why-then’ they occur. The North Aegean Sea is directly influenced by the outflow of the Black Sea water masses, through the Dardanelles Strait. Secondary, riverine discharge is into account, along with special hydrodynamic characteristics of the basin. This Black Sea contribution to the North Aegean basin is cold, brackish and rather rich in biomass and nutrients and via the eutrophic blooms, fluctuate the relative meso-poor nutrient character of the basin. The environmental impacts and causes of the occurrences have a multidisciplinary analysis. They affect local ecology systems, water quality, coastal regions, the ichtyo-stock, the eco-balance on food-dependable species and ultimately the human health. The current study leans emphasis on the meteorological-oceanographic analysis for the algae blooms in the North Aegean Sea, depending on the use of satellite derived data and optical color imaginary, concerning the area under study. The preliminary concern, along with secondary conclusions, among the variable instability of the local biogeochemical recycling of the phenomenon, the prolonged temporal time of its dispersion and its correlation with surface winds and meteo-characteristics, was verified. Data from Giovanni, that is a Web-based application developed by the GES DISC (Goddard Earth Sciences Data and Information Services Center) Interactive Online Visualization ANd aNalysis Infrastructure-NASA, where used for the analysis, in order for possible correlations between oceanographic and meteorological variables to be identified, such as: Chlorophyll-a concentrations, Precipitations rates, Euphotic Zone Depth, Colored Dissolved Organic Matter, Absorption coefficient for phytoplankton, Sea Level Pressure, Surface Pressure and Northwards wind component.
- ItemOpen AccessConglomerate clast composition analysis in a submarine fan depositional environment : a statistical approach in the provenance of the Cenozoic Pindos foreland basin in Achaia, Western Greece
Τμήμα Γεωλογίας (ΜΔΕ)Σάββα, Βασιλική; Ζεληλίδης, Αβραάμ; Ζεληλίδης, Αβραάμ; Μαραβέλης, Άγγελος; Παπαθεοδώρου, Γεώργιος; Savva, VasilikiIn this thesis is studied the Pindos foreland basin and specifically conglomerate of the Tritea sedimentary sub-basin. Also, statistical analysis of conglomerate became for further investigation. The Pindos foreland basin seems to have a petroleum potential, is characterized by petroleum accumulation in turbidite sandstone reservoirs and the porosity permeability of the reservoir is extremely complex. The Tritea sub-basin is in Achaia in NW Peloponnesus and is bounded to the east by the Pindos Thrust and to the west by the Gavrovo Thrust. Conglomerates are siliciclastic sedimentary rocks that consist predominantly of gravel-size clasts. They are usefulness in tectonic, provenance analysis, in the rather specialized depositional environments of conglomerates and some conglomerates serve as reservoir rocks for oil and gas. The conglomerate measurements include the sphericity, the roundness, the length of long axis and the lithology. Descriptive classification of conglomerates is useful in relating clast composition to sediment sources (provenance) and relate to depositional origin. So, nine outcrops (eleven sections) were analyzed and they were described section by section. Also, the depositional facies, the facies associations and depositional sub-environments were recognized. Bar diagrams about roundness, sphericity, long axis, pies for lithology were made for each section as well as comparative diagrams for all sections. The combined results from the different used tools are that the major provenance was the Pindos mountains, whereas Skolis Mountain was excluded as source area and transportation from the sourced rocks or internally to the basin took place in different distances. There are at least two different mechanisms of transportation one from Pindos Mountains and a second from uplifted earlier deposited sub-marine fans. Megaclasts were produced from cannibalized pre-existing submarine fans that accumulated earlier in the eastern parts of the basin, and were affected by basin deformation due to tectonic activity. The observed differentiations in lithology, roundness, sphericity and length of long axis support the idea of the existence of a thin bedded source of Pindos Mountains rocks affected by nappe tectonics. The statistical results from PCA are in accordance with sedimentological results, which suggest two groups of sections.
- ItemOpen AccessContribution to coalification processes from geological and microbiological aspect : the case of Philippi peat/lignite
Τμήμα Γεωλογίας (ΜΔΕ)Καλατζή, Μαρία Ιγνατία; Χρηστάνης, Κίμων; Χρηστάνης, Κίμων; Καλαϊτζίδης, Σταύρος; Lever, Mark; Kalatzi, Maria IgnatiaThis study deals with the characteristics of peat at depths of 0.20 - 191 m, to detect the changes in the physical and chemical characteristics of organic sediments and the microbiological aspect. The research focused on the Philippi peat (N. Kavala). The Philippi peatland grows in an intercontinental basin, whose sinking is mainly controlled by tectonic agents, with the development of peatgenetic plant species such as Cyperaceae, and is influenced by karst aquifers, constituting a topogenous mire, with main morphological characteristic the presence of hummocks. The qualitative and quantitative characteristics of the organic and inorganic sediments were examined. Particularly elementary and elemental analysis, mineralogical determinations and trace analysis (ICP-MS) were performed. Also, the abundances, compositions, and activities of microbial communities were investigated. Despite the important role of peatlands in the global carbon cycle, microbial communities in these environments remain understudied. Peats have been gradually recognized as a home to diverse microbial assemblages primarily through cultivation based studies. Modern molecular techniques have begun to be employed to explore microbial community structure in peatlands. DNA extraction, Nanodrop-3300 measurements, bacterial and archaeal qPCRs, mcrA genes qPCRs, normal PCRs and gel electrophoresis were performed. Ash content fluctuates greatly, and in particular the average ash value in peat is 40.79% by weight a value that is consistent with the topogenic character of the peat. Ash values in the samples range from 11.79% to 80.82%. The eC ranges from 183.5 - 1621 μS / cm, with an average of 746.7 μS / cm and pH from 4.70 to 7.69 with an average of 6.4. The minerals that appear in almost all samples are quartz, calcite, alkaline feldspars, clay minerals - more particularly, kaolinites - muscovite and bassanite (2CaSO4 • H2O). In this study, the conclusions that have emerged are that the Philippe peat is an intercontinental limestone-alkaline topogenous mire. The characteristics of sediment deposited vary mainly due to climatic changes. The Philippi peatland has a "moderate" content of minerals. In Holstein, the Eemian and Upper Weichsel there is a strong inflow of aluminosilicated grain, while in Saalian and the Holocene intense carbonate inorganic sedimentation. The shift of microbial abundance, community composition, and activity parallels with the stark differences in pH, eC, elementary and elemental analysis and in mineralogical determinations and trace analysis (ICP-MS).
- ItemOpen AccessDevelopment of strong ground motion database for the strong motion data of the Seismological labaratory of the University of Patras
Τμήμα Γεωλογίας (ΜΔΕ)Διονυσάτου, Κωνσταντίνα; Σώκος, Ευθύμιος; Σαμπατακάκης, Νικόλαος; Κουκουβέλας, Ιωάννης; Dionysatou, KonstantinaThe assessment of ground motion damage potential, due to an earthquake, is of enormous importance. Efficient design of structures is the key point for risk mitigation and can be achieved in accordance with it. Strong motion data should always include a description of a) the local site conditions (this is usually done through the Vs30 parameter), b) source parameters e.g. magnitude (preferably Mw), focal mechanism c) distance measures e.g. epicentral, hypocentral distance, distance from fault trace etc. In the present dissertation, we have compiled a strong motion database, using the data recorded by the strong motion stations of the University of Patras, Laboratory of Seismology, Seismic Network. A total of eleven strong motion stations, located in Western Greece, were used. We applied several methods and derived Vs30 estimates for all stations based on topography and geology. Moreover, we collected and included in the database all the crucial information regarding magnitude (in Mw scale), style of faulting and epicentral distance. Thus, the database includes all the necessary information for strong ground motion studies. Records were included in the database after careful processing which included various steps (e.g. format change, filtering, pre-selection etc). Finally, a number of key ground motion parameters (PGA, PGV, PGD, spectra) were obtained through the appropriate processing for the 110 accelerograms that were included in the database. As a final step, the Danciu & Tselentis, 2007 ground motion prediction equation (GMPE) was used for comparison and validation of the results. Results indicated a good comparison of ground motion values calculated during this Thesis and the predicted values obtained by the Danciu & Tselentis, 2007 GMPE. The database is accessible through a web interface , that allows the easy search, plotting and data export.
- ItemOpen AccessForaminiferal analysis of marine sediments from the last interglacial period. IODP expedition 381, Corinth gulf
Τμήμα Γεωλογίας (ΜΔΕ)Καστανά, Αικατερίνη; Kastana, AikateriniThis thesis examines the benthic foraminifera composition in specific sedimentary intervals from the core M0079 recovered from the Corinth rift in the framework of IODP Expedition 381. These intervals are parts of the lithostratigraphic subunit 1.3 (LSU 1.3) deposited from 154.47 mbsf to 179.8 mbsf. LSU 1.3 appears to coincide broadly with the prevalence of MIS 5 which is dated between 75 ka and 122 ka. The aim of this work is to assess the variation of the seafloor environmental conditions of the Corinth gulf within this period.
- ItemEmbargoGeochemistry, sedimentology, contamination assessment and submerged aquatic vegetation (SAV) mapping using unmanned surface vehicle (USV) : the Gialova lagoon case study
Τμήμα Γεωλογίας (ΜΔΕ)Παπακωνσταντίνου, Μαρία; Papakonstantinou, MariaGialova lagoon, suited in SW Peloponnesus (Greece), constituted the subject of this study, where a multidisciplinary methodological approach was followed. The main objectives of this study were to identify the morphology and characteristics of the lagoon’s floor, to visualize the spatial distribution of sedimentological characteristics of the lagoon, to examine possible correlations amongst acoustic characteristics of the lagoon’s floor and granulometry, to calculate the elemental concentration of surface sediments and finally to examine potential heavy metal enrichment by validated techniques. The purposes of the study were fulfilled on the basis of two sampling campaigns carried out on August and on December 2020, during which geophysical and sedimentological data were collected, respectively. The reconnaissance survey revealed the geophysical and natural characteristics of the lagoon, using a high resolution side scan sonar (SSS) on board an Unmanned Surface Vehicle (USV). A total area of 0.85 km2 was insonified (almost the 36 % of the 2.37 km2 in total) and after the processing of the SSS data, the Gialova lagoons’ floor surface mosaic was revealed. The E-W and the N-S running ridges have also been recorded on the mosaic. A detailed bathymetry map was also acquired from the single beam echosounder collected data, with the additional information obtained by the two indices extracted values, E1 (roughness) and E2 (hardness), all of which showed that Gialova lagoon consists of an extremely shallow water body, with a minimum and maximum water depth of 0.40 m and 0.70 m, respectively. Three morphological parts were defined: (i) the western shallow basin with maximum water depth of 0.65 m, (ii) the eastern shallow basin with slightly higher depth (0.70 m) and (iii) the central and coastal part with water depth less than 0.55 m. It is found that, the spatial distribution of the backscatter coincides well with the three morphological parts and the subaqueous vegetation of the lagoon. The examination of the side scan sonar mosaic, through a manual classification process, showed that six (6) distinct acoustic types (AT) were identified in the lagoon floor. The manual acoustic classification of lagoons’ floor was based on the reflectivity (low or high) and on the alternation of the reflectivity (fragmented or continuous) within the respective AT. Along with the in situ ground truthing results, the submerged aquatic vegetation (SAV) is found to cover each of the six (6) AT. The ATs 1, 2 and 3 are representing areas covered by SAV in a percentage of <1 %, 5-12 % and (13 %)-25-50 %, respectively, each of which occupying the 12.55 %, 17.77 % and 19,99 % of the total surveyed area, correspondingly. Similarly, ATs 4 and 5, which are representing areas covered by SAV in a percentage of 50-75 % and >75%, respectively, hold the 38.94 % and the 9.13 % of the total surveyed area, correspondingly. AT 6 holds the 1.61 % of the total surveyed area and it represents the E-W ridge. With the use of SonarClass software and based on: (i) the extracted tonal grey level statistics (1st order), (ii) the textural statistical parameters (2nd order), extracted by the Grey Level Co-occurrence Matrices (GLCMs), and (iii) the ground-truthed training samples, the unsupervised classification results were revealed, regarding the overall SSS mosaic dataset. The unsupervised classification results are correlated very well with the AT spatial distribution, as defined by the manually classification procedure. Further, a cloud free imagery from the archive of MAXAR Technologies was selected for the mapping of the SAV in Gialova lagoon, with emphasis on the percentage cover. The selected image was an 8-band multispectral WorldView II, collected at 27/06/2020. The classification scheme was based on the analysis of the hydroacoustic data, mainly the SSS mosaic and the delineation of the percentage of cover of the SAV in each region. The overall accuracy of the resulted pixel based classification was 54 % and the F1 score was 49.2 %. The SAV coverage spatial distribution based on the satellite image processing, found to be very well correlated with the SAV spatial distribution, as it emerged from the manual and unsupervised classification procedures. Further, on the basis of the bathymetric map and the backscatter properties of the lagoon floor, sediment samples were collected from 28 pre-defined sampling stations, for the investigation of the spatial distribution of the lithological characteristics, the major/ trace elements and the organic carbon. Sediment samples were subjected to macroscopic description, granulometry and chemical analysis. Initially, all sediment samples were visually described in terms of the color scale of Munsell and by visual inspection of sediments textural features. Grain size analysis was performed using a Malvern Mastersizer 2000 particle analyzer, while prior to analysis, Hydrogen peroxide (H2O2) treatment was applied for the elimination of organic matter. Also, textural evaluation of the sediments (0.063 – 1 mm size range) was made with the use of Leica binocular microscope. Based on the grain size analysis, the macroscopic observations and the textural evaluation, the sediment samples of Gialova lagoon are classified in 4 sediment types. Type A is consisted of very dark grey (5Y 3/1) mud with rare – sparse presence of bioclasts (sand to gravel sized bivalve shells) and there is rare presence of plant residues. Type B is comprised of very dark grey (5Y 3/1) silt with increased clay and water content. In this type, there is rare to sparse presence of bioclasts and sparse to common presence of plant residues. Type C is consisted of very dark grey (5Y 3/1) sandy silt with common presence of plant residues and bioclasts (gastropods and bivalve shells fragments) whereas Type D contains very dark grey (5Y 3/1) silt with common to dominant presence of bioclasts and plant residues. It is also noteworthy that, a thin (mm scale) dark grayish brown (2.5Y 4/2) mud layer found to cover the Gialova lagoon bottom sediments. The definition of the main four grain size statistical parameters, mean (Mz), sorting (σi), skewness (Sk) and kurtosis (KG) were calculated with the GRADISTAT program, while sediment classification was based on Folk (1974) nomenclature. The investigation of the surface sediments granulometry showed that it coincides well with the morphology of the lagoons’ floor. More specifically, the western basin consists of very fine-grained sediments, the eastern basin is covered by slightly coarser sediments, whereas the central shallower part of the lagoon is covered by coarser sediments compared to the two basins. The central part displays the highest sand mean percentage, high silt and the lower clay percentage. The spatial distribution of clay proportion clearly reflects the three different morphological parts of the lagoon. The coarser sediments associated with the higher sand proportion were obtained along the southwestern coast of the lagoon, just north of the sandy lagoon barrier separating the lagoon from Navarino Bay and near the inlet. Total Organic Carbon (TOC) was measured using a LECO Carbon analyzer after HCL (25%) pre-treatment to remove carbonates. The spatial distribution of the TOC seems to be affected by the morphology of the lagoons’ floor. The higher TOC percentages were measured in the two shallow basins where the very fine sized sediments dominate, while low concentrations were obtained along the sand barrier at the southwestern part of the lagoon and at the central part. The concentrations of selected major (wt%) and trace elements (ppm) in the surface sediments of Gialova Lagoon were determined by four acid digestion followed by ICP-MS finish. The spatial distribution of sediment characteristics was visualized using the Surfer 9 and ArcGIS software. The whole geochemical dataset (Ag, Al, Ba, Be, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, Hf, In, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Rb, S, Sb, Sc, Se, Sn, Sr, Ta, Th, Ti, Tl, U, V, W, Y, Zn, Zr and Corg) was subjected to Multivariate statistical treatment. R-mode Factor Analysis (FA) was used for revealing the dominant geochemical processes in the lagoon and Q-mode FA, for detecting the interrelationships of the sediment samples, in terms of their geochemical composition. Five (5) different geochemical processes occurring in the lagoon bottom sediments were identified based on R-mode FA. There are processes defined by the presence of terrigenous aluminosilicates associated with Corg which present a clear antipathetic relation with autochthonous biogenic carbonates, processes driven by agricultural drainage, processes oriented by phosphates and selenium element and processes driven by the association of Y adsorbed and/ or co-precipitated with amorphous Mn oxyhydroxides. Through Q-mode Factor Analysis plot, three (3) surface sediment samples clusters were identified: the sediment samples included in cluster A represent the terrigenous aluminosilicates associated with Corg which is characterized by elevated concentrations of many metals, the sediment samples which are classified in cluster B represent the biogenic carbonates with the highest Calcium (Ca) and Strontium (Sr), whereas sediment samples of cluster C, located in the midpoint of factor plot, show intermediate element concentrations compared to the end-member samples (Cluster A and B). The Q factor plot can be considered that portrays the entire spectrum of contamination of the surface sediments of the lagoon from the most contaminated to less contaminated. For the assessment of the level of trace metals contamination and the possible anthropogenic impact on the sediments of Gialova lagoon, three (3) of the most used pollution indices were applied: Geo-accumulation Index (I-geo) (Muller, 1979), Enrichment Factor (EF) (Kemp et al., 1976) and Pollution Load Index (PLI) (Tomlinson et al., 1980). For the calculation of the indices, the global average shale data from Turekian and Wedepohl (1961) were used as background. I-geo values indicated that the Gialova lagoon is characterized from unpolluted to moderately polluted sediments for the elements Mo, Na, Ni, Pb and Se and from strongly polluted sediments in S element. EF values showed that elements with moderate enrichment are: Mn, Mg, Cr, Ni, Pb, Mo and Sr, whereas, elements with significant enrichment are: Na, Se and S. PLI exhibiting values lower than one (1), therefore the sediments are unpolluted to slightly polluted.
- ItemEmbargoGeographical reconstrustion of the area of the ancient harbour of Lechaion using marine geophysical methods
Τμήμα Γεωλογίας (ΜΔΕ)Γκριμπούλη, Μαρία-Αφροδίτη; Παπαθεοδώρου, Γεώργιος; Παπαθεοδώρου, Γεώργιος; Γεραγά, Μαρία; Καλαιτζίδης, Σταύρος; Gkrimpouli, Maria-AfroditiThe Gulf of Corinth is the second most active continental rift in the world and thus a much-studied natural laboratory for analyzing details of rift history. The Gulf of Lechaion sited S-E of the Corinth Gulf is the least studied area of the active Corinth graben. Although, the study of the Lechaion Gulf renders great importance as its formation is estimated to constitute an early rifting stage, where the evolution of the Corinth Gulf started. Therefore, more offshore seismic surveys combined with the already acquired data in this least studied part, will shed light to the tectono- sedimentary evolution of the eastern end of the Corinth rift. Besides the geological importance, Lechaion Gulf hosts the ancient harbour of Lechaion, which is of great archaeological significance and was built at 600BC, a period of zenith for ancient Corinth when its military and naval activities flourished. The coastal installations of the ancient harbor are still visible today, though part of them are partly or completely submerged due to the glacio- eustatic and tectonic movements in the area during Quaternary. The present thesis aims to the reconstruction of the coastal palaeoenvironment of the ancient harbour of Lechaion and the recent geological activities nearby the submerged installations through the interpretation of the seismic stratigraphy and the seafloor morphology data. The survey was conductedin three sessions, at November 2013, 2014 and 2015 and the data were collected with high frequency 3.5 kHz Pinger type subbotom profiler, where an area of 8,5 km2was scanned and 146 routes with 145,4 km length of seismic data were collected, reaching a maximum depth of 60m below the sea surface. The seismic profiles were then processed with specialized programs at the Laboratory of Marine Geology and Physical Oceanography. The digital process enabled the design of bathymetric maps, isopach maps and also 3D models depicting the marine geomorphology around the harbor area and the sediment distribution near the ancient installations. The composition and processing of all these seismic data enabled the estimation of the chrono- stratigraphy, paleo- morphology and geological regime of the ancient harbour of Lechaion.
- ItemOpen AccessIchnofauna research as a tool for unraveling the paleoclimatology and paleoecology in active continental margins : a case study from the cenozoic submarine fans of Pindos foreland basin in Achaia, Western Greece
Τμήμα Γεωλογίας (ΜΔΕ)Μπουρλή, Νικολίνα; Ζεληλίδης, Αβραάμ; Μαραβέλης, Άγγελος; Ηλιόπουλος, Γεώργιος; Mpourli, NikolinaTurbidite facies distribution, ichnofacies and ichnofossils analysis of submarine fan can give results of paleoenvironment and paleoclimate in a sedimentary basin. The evolution in the Pindos foreland basin of the west Peloponnesus indicates that the part of the foreland was developed during Late Eocene to Early Oligocene in the sub-basin of Tritea. The purpose of this paper is to improve the knowledge of how the ichnofossils affect the sedimentary basin. The analysis of the diversity and the abundance of ichnotaxa submarine fans, results on paleoenvironments how they affect the sedimentary basin and the paleoclimate. In this study 16 different taxa of tracefossils have been recognized in deep-sea fan deposits. The sections which are closer to the Pindos thrust are characterized by high abundance, low diversity and low oxygen level in contrast with the distal areas from Pindos thrust which are characterized by low abundance, high diversity and high oxygen level. The ichnodiversity and ichnoabundance decrease upward gradually reflecting the impact of the changing depositional environments from basin ﬂoor fans, to slope systems and then to shelf environments. The regional basin-ﬁll history, rather than global climatic changes, was probably the fundamental controlling factor on the distribution of trace fossils across the E/O boundary.
- ItemOpen AccessImprovement of regional seismic hazard assessment considering active faults
Τμήμα Γεωλογίας (ΜΔΕ)Τσιπιανίτης, Αλέξανδρος; Σώκος, Ευθύμιος; Τσελέντης, Γεράσιμος; Κουκουβέλας, Ιωάννης; Tsipianitis, AlexandrosSeismic hazard assessment is a required procedure to assist effective designing of structures located in seismically active regions. Traditionally, in a seismically active region as Greece, the seismic hazard evaluation was based primarily on the historical seismicity, and to lesser extent based on the consideration of the geological information. The importance of the geological information in seismic hazard assessment is significant, for the reason that earthquakes occur on faults. This approach also covers areas with few instrumental recordings. Mapping, analyzing and modeling are needed for faults investigation. In the present dissertation, we examined the seismic hazard for the cities of Patras, Aigion and Korinthos, considering the seismically active faults. The active faults considered in this investigation consists of 148 active faults, for which a minimum amount of information was available (i.e. length, maximum magnitude, slip rate, etc.). For some critical parameters, e.g. slip rate, if an estimate could not be found in the literature it was calculated based on empirical laws. Specifically, the slip rate for each fault was resulted from the division of total displacement with the stratigraphic age. Two different approaches (historical seismicity, length of faults) were followed for the estimation of total displacement for each fault. A distribution of slip rates was made because uncertainties are considered. The resulted slip rates were converted into seismic activity. Thus, we were able to construct a complete database for our research. Epistemic uncertainties were accounted at both seismic source models as well as at the ground motion via a logic tree framework resulted in two different calculation procedures (including or not the b value uncertainty). The seismic hazard model was implemented following the OpenQuake open standards – NRML, and the seismic hazard computation was performed for the region of interest. The seismic hazard was quantified in terms of seismic hazard maps, hazard curves and uniform hazard spectra for the region of interest. Different intensity measure types were considered, Peak Ground Acceleration, Spectral Acceleration at two fundamental periods 0.1 and 1.0 sec. Finally, the results of this thesis were compared with the Greek Seismic Code and other seismic hazard estimations for the investigation region.
- ItemOpen AccessInterpretation of Pleistocene deposits from Magoula (northwestern Peloponnesus, Greece)
Τμήμα Γεωλογίας (ΜΔΕ)Καρανίκα, Κωνσταντίνα; Ηλιόπουλος, Γεώργιος; Κουκουβέλας, Ιωάννης; Gliozzi, Elsa; Karanika, KonstantinaThis work involves the palaeoecological study of Pleistocene deposits from Magoula (northwestern Peloponnesus, Greece), based on the analysis of microfaunal elements. The study area has been chosen not only as a site of significant palaeontological interest where plant fossils, mammal bones and a wide range of different kinds of invertebrate and microfossils occur, but also for its tectonic position at the Rio –Antirio basin. The former basin bridges the Patraikos and Corinth Grabens. Microfaunal analyses were carried out on 267 samples collected every 20-40cm from two natural sections in the area of Magoula. From the first section (section M), which has a total thickness of 31.30 meters, 133 samples were processed, whereas from the second section (section K) with a total thickness of 27.20 meters, 134 samples. Sediment samples were wet sieved with tap water through 500 and 63 μm mesh sieves. Microfossils were sorted from the dried residues and subsequently were studied under the stereoscope. Species were determined based on previous studies of Mediterranean benthic taxa. The collected data were analyzed, relative abundance diagrams were prepared for each species using the software C2. Furthermore, taphonomic indices (Right/Left valve ratio, Sex ratio, Adult/Juvenile ratio and Carapace/Disarticulated Valves ratio) were calculated for most of the abundant species of ostracods. Also, stratigraphic columns were plotted according to collected section log data. Considering both the stratigraphic and the micropalaeontological analysis results, a detailed palaeoenvironmental reconstruction took place. In section M, according to microfaunal analysis, 4 ostracod taxa (Cyprideis torosa (both un-noded and noded morphotypes), Candona neglecta, Ilyocypris gibba, Aurila convexa) were recorded in the studied samples. The most abundant were C. torosa and C. neglecta. Two benthic foraminifera taxa (Ammonia tepida and Haynesina depressula), as well as some charophyte gyrogonites, freshwater gastropod opercula and fragments (Bithynia sp. and Valavata cristata) were identified as well. These data suggest that an initially lagoon system, turned gradually into a lagoonal river mouth environment (barren layers) due to sea level drop, and finally when sea level rose, it became again a lagoonal environment influenced by a river system with strong freshwater influxes. Moreover, the relative abundance diagrams and the taphonomic indices in combination with the stratigraphic column characterize a possible flood event at 24.10-24.30 meters. Thus paleoenvironmental changes occurred due to eustatism. In section K, according to the microfaunal analysis, 6 ostracod taxa (C. torosa (un-noded morphotypes), C. neglecta, Loxoconcha elliptica, Cytheridea neapolitana, Leptocythere rara and A. convexa were recorded in the studied samples, 6 benthic foraminifera taxa (A. beccarii, Ammonia tepida, H. depressula, Elphidium advenum, Elphidium crispum and Quinqueloculina seminula), as well as some brackish gastropods (Hydrobia acuta) brackish bivalves and fragments (Cerastoderma glaucum and Mytilidae) were identified as well. Palaeonvironmental changes occurred due to eustatism. Initially a lagoon system, turned gradually into an open lagoon environment due to sea level rise, and finally when sea level dropped became again a lagoonal environment influenced by a river system with freshwater influxes. The distance between section M and section K is only 138 meters, however, there is no connection between the two referred palaeoenvironments. The small distance between the two sections and the difference of the determined palaeoenvironments indicate the effect of a fault, with a total throw of at least 58.5 metres.
- ItemRestrictedInvestigation of the modal composition and three-dimensional modelling of plutonic rocks : a case study on the Vardar ophiolites (Greece)
Τμήμα Γεωλογίας (ΜΔΕ)Γιαμάς, Βασίλειος; Giamas, VasileiosX-ray micro–Computed Tomography (μCT) is a technique that has been applied to several geological samples including meteorites, igneous and metamorphic rocks, ore/drill cores, sediments organic or inorganic and fossils. Representative lithotypes from a complete ophiolitic sequence, have not been extensively examined, although there are a few cases reported concerning specific lithological types such as chromitites or serpentinized and carbonitized ultramafics. Aim of this study is to evaluate the applicability of X–ray micro–Computed Tomography technique upon relatively unaltered ophiolitic rocks and to provide suggestive methodologies coupled with other state-of-the- art techniques to be implemented for optimum characterization of ophiolitic rocks to assist in resolving specific geological or related geoengineering queries where ophiolites are involved. The results and methodologies presented provide an innovative approach: i) to distinguish amongst principal rock forming minerals, ii) to precise identify and quantify their textural features in a three-dimensional perspective, and iii) to detect deformation patterns related to post-magmatic metamorphic processes.
- ItemOpen AccessIODP - expedition 381, site 79A : insights into the palaeoceanography of the Corinth gulf in the upper Quaternary from the study of foraminifera assemblages
Τμήμα Γεωλογίας (ΜΔΕ)Αγγελοπούλου, Δήμητρα; Γεραγά, Μαρία; Γεραγά, Μαρία; Παπαθεοδώρου, Γιώργος; Σακελλαρίου, Δημήτρης; Angelopoulou, DimitraThe Corinth Gulf is considered one of the high degree of important natural laboratories for the natural scientists. The Corinthian Gulf is an asymmetrical tectonic rift. High tectonic activity and complex geomorphological evolution indicatea highly active deformation of the area, highlighting the geological importance of the region. This is the main reason why International Ocean Discovery Program (IODP) proposed the study of Corinth Gulf. As the basin has subsided, fluctuating global sea level and its absolute position relative to sea level, has affected the depositional environment. This appears from the basin sediments which record this spatial and temporal advancement. The principal objective of International Ocean Discovery Program (IODP) Expedition 381 was to retrieve a record of early continental rifting and basin development from the rift, in the Corinth gulf, central Greece. During this expedition three different sites (Site M0078, M0079, M0080) in the Corinth Gulf were drilled, cored and logged. The main finding of this study was that the Corinthian Gulf presented periods of connection with the open sea and its isolation from it during the Quaternary period. In the present master thesis, 175 sediment samples were studied from the M0079 core in 125µm and 63µm fractions to examine the presence of planktonic and benthic foraminifera. These sediment samples are located between0.23and148.43mbsf (meters below seafloor). This interval corresponds to the Subunits SU1 and SU2, as these determined from the scientific sedimentological group of the expedition. SU1 extends from 0.23 to 32.02 mbsf and it most probably corresponds to Marine Isotopic Stage (MIS) 1. In this unit foraminifera are abundant though the number of benthic specimen is significant higher than that of the planktonics. This suggests that SU1 corresponds to a marine phase. SU2 extends from 32.59 to 148.43 mbsf and most probably it corresponds to MIS 2, 3 and 4.SU2 is characterized in general by absence or low numbers of foraminiferal specimen suggesting that SU2 corresponds to an isolated phase. This isolated phase is interrupted by short marine phase intervals where planktonic and benthic foraminifera are abundant. The deposition of these short intervals could be related to temporal rises of sea level due to eustatic –isostatic factors or to tectonic driven mechanisms.
- ItemOpen AccessIODP-expedition 381, site 79A. Palaeoceanographic evolution of the Corinth gulf during the MIS5, based on the downhole distribution of foraminiferal assemblages
Τμήμα Γεωλογίας (ΜΔΕ)Αντωνίου, Δήμητρα; Γεραγά, Μαρία; Παπαθεωδόρου, Γεώργιος; Σακελλαρίου, Δημήτριος; Antoniou, DimitraAs an early continental rift with high strain rates, the Gulf of Corinth has mainly attracted many geoscientists due to its preservation of the synrift succession both onshore and offshore. This feature was recognized by the International Ocean Discovery Program (IODP) when marine scientists proposed Corinth Gulf as a study area in European Consortium for Ocean Research Drilling during the program “Exploring the Earth under the sea”. One of the expedition objectives was the generation of a new high-resolution record of the Quaternary paleoclimate. Throughout this expedition three different sites (Site M0078, M0079, M0080) in the Corinth Gulf were drilled, cored and logged. After this phase, the holes were submitted to many and different methods and techniques whereby new data and information for lithostratigraphy, structural geology, geochemistry and micropaleontology of the sediments were arisen. Regarding the micropaleontology, preliminary results of the holes showed that there were temporal intervals when Gulf of Corinth was connected with the open sea and isolated from it. To reinforce the previous results, in the terms of the master thesis, 58 sediment samples from hole M0079 studied in 125μm and 63μm fractions for the existence of planktonic and benthic foraminifers. The present master thesis aims to study the environmental conditions which contributed to the formation of Corinth Gulf throughout the SU3 deposition (149.2-183.87 mbsf; meter below sea floor) and the upper part of SU4 (186.37-201.01 mbsf). The distribution of foraminifers during the deposition of SU3 sediments shows a high variety and quantity of planktonic and benthic foraminifers with the former be more abundant. Below SU3, foraminifers are significantly decreased. These results in conjunction with the curves of global sea-level fluctuations signify that during SU3 deposition the distribution of planktonic foraminifers along the hole coincides with the substages of Marine Isotope Stage 5 (5a, b, c, d, e) when the rift was connected with the open sea. Finally, the transition from the SU3 to SU4 is characterized by the rapid depletion of foraminifers indicating the onset of MIS 6 when the rift was an isolated/semi-isolated environment.
- ItemOpen AccessKατολισθητικά φαινόμενα στις πυρόπληκτες περιοχές του Ν. Ηλείας : α) Διερεύνηση της αποτελεσματικότητας των έργων αποκατάστασης στο Δήμο Αμαλιάδας. β) Τεχνικογεωλογικές-γεωτεχνικές συνθήκες στην κατολίσθηση στο Παλαιοχώρι του Δήμου Ζαχάρως
Τμήμα Γεωλογίας (ΜΔΕ)(2012-02-14) Καραμπούλη, Παναγιώτα; Σαμπατακάκης, Νικόλαος; Κούκης, Γεώργιος; Λαμπράκης, Νικόλαος; Karampouli, PanagiotaΣτην παρούσα εργασία αξιολογήθηκαν τα κατολισθητικά φαινόμενα που εντοπίστηκαν στους πυρόπληκτους Δήμους του Νομού Ηλείας. Δίνεται ιδιαίτερη έμφαση στα έργα αποκατάστασης στο Δήμο Αμαλιάδας, όπου επλήγη από τις καταστροφικές πυρκαγιές τον Αύγουστο του 2007. Συνολικά καταγράφηκαν έξι (6) θέσεις σε οικισμούς του Δήμου Αμαλιάδας στις οποίες παρουσιάζονται προβλήματα κατολισθήσεων. Παρατηρήθηκαν αστοχίες επιχωμάτων οδών, εδαφικές ροές, περιστροφικές ολισθήσεις, εδαφικοί ερπυσμοί, ροές γαιών και επιφανειακές διαβρώσεις λόγω της δράσης των επιφανειακών νερών και της απώλειας της βλάστησης μετά τις πυρκαγιές. Στις θέσεις αυτές, μελετήθηκαν και αξιολογήθηκαν όλα τα προτεινόμενα μέτρα προστασίας και αντιμετώπισης όπως αυτά προτάθηκαν σε παλαιότερη μελέτη που είχε εκπονηθεί από την Περιφέρεια Δυτικής Ελλάδας. Στη συνέχεια, η έρευνα επικεντρώθηκε στην κατολίσθηση του Παλαιοχωρίου, που εκδηλώθηκε μετά τις παρατεταμένες βροχοπτώσεις το χειμώνα 2009-2010. Πραγματοποιήθηκε λεπτομερής γεωτεχνική - τεχνικογεωλογική έρευνα για την αντιμετώπιση της μετακίνησης της κατολισθαίνουσας ζώνης. Έπειτα από την εκτέλεση μιας (1) δειγματοληπτικής γεώτρησης και εργαστηριακών δοκιμών προσδιορίστηκαν τρείς (3) γεωτεχνικές ενότητες. Έγινε σύνταξη τεχνικογεωλογικού χάρτη και σχεδιάστηκαν τεχνικογεωλογικές τομές σε κλίμακα 1:1000. Στην αστοχία αυτή που μελετήθηκε, έγινε ανάλυση οριακής ευστάθειας πρανών χρησιμοποιώντας το λογισμικό SLIDE 5.0, Rock science Inc. Το πρόγραμμα έδειξε την ασταθή κατάσταση του πρανούς με συντελεστές ασφάλειας Fs<0,4 για διαφορετικές επιφάνειες ολίσθησης σε όλη την κατολισθαίνουσα μάζα. Για την βελτίωση του συντελεστή ασφάλειας Fs προτείναμε μέτρα εξυγίανσης και αποκατάστασης του πρανούς. Με την εφαρμογή των μέτρων αυτών παρατηρήθηκε ότι ο συντελεστής ασφάλειας αυξήθηκε ξεπερνώντας την τιμή Fs=3.
- ItemOpen AccessLate Holocene hydro-climatic variability in the eastern Mediterranean : a spatial multiproxy approach
Τμήμα Γεωλογίας (ΜΔΕ)Μπασούκας, Δημήτριος Αδριανός; Bassukas, Dimitrios AdrianosIn the current master thesis (13) paleoclimatic archives of the broader eastern Mediterranean area were collected and examined statistically in search of underlying millennial trends for the period 200-2800BP (before 1950). For each archive, a proxy record representative of hydroclimatic changes was selected, normalized using z-factors, to facilitate intercomparison, and analyzed statistically. The multivariate statistical analysis was performed using a clustering analysis (HCA) and dimension reduction (PCA), which led to groupings of similar records in a temporal manner and allowed the identification of spatially underlying millennial scale modes of variability. Two main modes of variability were identified, further supporting complex trajectories of paleoclimatic evolution in the region. A first mode was identified for sites presenting a millennial scale trend from a wetter to an overall drier phase, with respective changes at major phase shifts at 1400BP and 1100BP. All sites were from the southern Balkan region and north as well as southwestern Turkey. A contrasting dry to wet millennial scale trend was identified for a site in the Peloponnese (Greece) and the Levant area, with major phase shift around 750BP. The inclusion of different proxies from very different environmental settings and the 200-year window has complicated the connection of established short-term climatic events to the study findings.