Neotectonic movements, sedimentation and water-level fluctuation of the Lake Vegoritis in Upper Quaternary

Vegoritis is a large, deep, mesotrophic, karstic lake in NW Greece, located in Ptolemais basin. Dramatic lowering of the lake's level has occurred during the last half century due to human pressures. The Ptolemais Basin and the lake itself are subjected to serious human pressures. Pollutants are carried into the lake through both, the atmosphere and surface runoff. In order to identify the levels, and assess the origin of heavy metals in surface lake sediments, 24 samples were collected and analyzed for their grain size, as well as for their mineral, organic matter, major element and heavy metal content. The origin of heavy metals has been attributed to specific geogenic and anthropogenic sources. Despite the anthropogenic disturbance, the levels of micropollutants were low, possibly due to the low retention time of lake water and the recent increase of sedimentation rates. Only Cr, Ni, Co As, and Ba were present in relatively high concentrations. Ba is derived from the erosion of acid silicate rocks, Cr primarily from mafic rocks and secondarily from pollution, whereas for Ni and Co the opposite is true, while As is primarily attributed to fly ash deposition. The lowering of the lakes' water level exposes sediments, which are then being oxidized. Mobilization of As and Cr could impair humans' and ecosystems' health.

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Quaternary Deformation of the Mavropigi Lignite Field (Western Margin of Ptolemais - Kozani Graben, Nw Macedonia, Greece)

Diamantopoulos

Dimitrakopoulos

Fountoulis

2004

geosociety

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The present study aims to analyse in details the tectono-sedimentary processes of the western borderline of the intra-continental graben of Ptolemais-Kozani in NW Macedonia, given the presentday mining activity of Public Power Corporation. Field studies in combination with drilling analysis revealed the extremely geometrical complexity of the sedimentary fill as the result of the recent Quaternary deformation. Bearing in mind, the recognition of left-lateral strike-slip component of movement in the western border fault zone-Mavropigi shear zone, the geometrical coincidence of the morphological shapes of the present-day morphology-of the top-of the bottom of the Pliocene earthy lignite sequence and of the sub-surface morphology of the pre-Cretaceous Pelagonian basement as well as the discovery of several reverse faults in the surrounding area have allowed us to accept the action of a composite Quaternary deformational pattern. For the first time in NW Macedonia, ductile-brittle type macrostructures (mega-anticlines) with NE-SW axis direction are confirmed, showing the simultaneous and progressive action of ductile and brittle deformation of all the geological formations of the western borderline, sedimentary fill and metamorphic basement. The aforementioned geometrical complexity and also the observed field structures strongly reveal the action of a rotational couple-type stress field in Ptolemais-Kozani graben, enclosed in the inca piate in-type deformation of NW Macedonia. In this framework, the occurrence of the extensional post-orogenic structures, which seems that they have been overestimated by previous researchers in the literature, is considered of secondary importance and constitutes part and expression of the complicated Quaternary tectonic structures of the sedimentary fill. This complex deformational pat tern controls and also defines the spatial distribution of the lignite reserves in the Mavropigi Lignite Field with a southward increasing of them as well as causes regions with a composite or a simple post-orogenic geometry and evolution, directly reflected by the sub-surface geometry of the Plio cene lignite sequence. The aforementioned complicated geometry is of great importance, either for the planning and the future expansion of the Mavropigi Lignite Field in the western borderline, or for the better approach of the intra-plate deformational processes of Ptolemais-Kozani graben.

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Neotectonic movements, sedimentation and water-level fluctuation of the Lake Vegoritis in Upper Quaternary

Cited by 4 publications

References 3 publications

Patterns, origin and possible effects of sediment pollution in a mediterranean lake

Patterns, origin and possible effects of sediment pollution in a mediterranean lake

Patterns, origin and possible effects of sediment pollution in a Mediterranean lake

Quaternary Deformation of the Mavropigi Lignite Field (Western Margin of Ptolemais - Kozani Graben, Nw Macedonia, Greece)

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