A. Kilias

Postnappe stacking extension and exhumation of high-pressure/low-temperature rocks in the island of Crete, Greece

The island of Crete consists largely of nappes of contrasting lithologies and metamorphism that were stacked southward during an Oligocene-early Miocene N-S compression, with the lower nappes undergoing a high-pressure/low-temperature (HP/LT) metamorphism. This was followed by a N-S Miocene crustal extension that caused thinning of the nappes and uplift of the HP/LT metamorphic rocks. Ductile conditions took place in the lower nappes associated with a retrograde greenschist metamorphism, while semiductile to brittle conditions took place in the upper nappes. A major normal detachment fault separates the lower and the upper nappes. The quartz texture analyses and the symmetry of structures indicate bulk coaxial deformation, while the results of strain analysis suggest both constrictional and flattening strains. A younger NE-SW compression affected both the thinned nappe pile and the late Miocene-Pliocene sedimentary basins. Finally, a Pliocene NE-SW extension led to further uplift and exhumation of the HP/LT metamorphic rocks. This cyclic tectonometamorphic process of alternate compression and extension took place during the migration of the Hellenic orogenic belt toward the most external units, including successive tectonic events.

Tertiary extension of continental crust and uplift of Psiloritis metamorphic core complex in the central part of the Hellenic Arc (Crete, Greece)

Kinematic analysis of the deformation in central Crete suggests that the structural evolution and exhumation of the high pressure/low temperature (HP/LT) rocks outcropping at the Mount Psiloritis metamorphic core complex are associated with a regional, Miocene, north-south extension and thinning of the continental crust. This tectonic regime developed under bulk coaxial strain conditions, with ductile deformation in the lower and brittle deformation in the upper crust, and followed, on the decompressional path, a north-south compression associated with a HP/LT metamorphism in the lower crust. This compressional event took place during Oligocene—Early Miocene and led to overthickening of the accretionary wedge in the Hellenic Arc. An east-west directed compression accompanied, in the final stages, the Miocene north-south extension of the continental crust.

Thessaloniki–Gerakarou Fault Zone (TGFZ): the western extension of the 1978 Thessaloniki earthquake fault (Northern Greece) and seismic hazard assessment

Abstract Active faulting and seismic properties are re-investigated in the eastern precinct of the city of Thessaloniki (Northern Greece), which was seriously affected by two large earthquakes during the 20th century and severe damage was done by the 1759 event. It is suggested that the earthquake fault associated with the occurrence of the latest destructive 1978 Thessaloniki earthquake continues westwards to the 20-km-long Thessaloniki–Gerakarou Fault Zone (TGFZ), which extends from the Gerakarou village to the city of Thessaloniki. This fault zone exhibits a constant dip to the N and is characterised by a complicated geometry comprised of inherited 100°-trending faults that form multi-level branching (tree-like fault geometry) along with NNE- to NE-trending faults. The TGFZ is compatible with the contemporary regional N–S extensional stress field that tends to modify the pre-existing NW–SE tectonic fabric prevailing in the mountainous region of Thessaloniki. Both the 1978 earthquake fault and TGFZ belong to a ca. 65-km-long E–W-trending rupture fault system that runs through the southern part of the Mygdonia graben from the Strymonikos gulf to Thessaloniki. This fault system, here called Thessaloniki–Rentina Fault System (TRFS), consists of two 17–20-km-long left-stepping 100°-trending main fault strands that form underlapping steps bridged by 8–10-km-long ENE–WSW faults. The occurrence of large (M≧6.0) historical earthquakes (in 620, 677 and 700 A.D.) demonstrates repeated activation, and therefore the possible reactivation of the westernmost segment, the TGFZ, could be a major threat to the city of Thessaloniki. Changes in the Coulomb failure function (ΔCFF) due to the occurrence of the 1978 earthquake calculated out in this paper indicate that the TGFZ has been brought closer to failure, a convincing argument for future seismic hazard along the TGFZ.

Evaluating urban land cover change in the Hurghada area, Egypt, by using GIS and remote sensing.

The rapid urban development in the Hurghada area since the 1980s has dramatically enhanced the potential impact of human activities. To inventory and monitor this urban development effectively, remote sensing provides a viable source of data from which updated land cover information can be extracted efficiently and cheaply. In this study, data from three satellite datasets, Landsat Thematic Mapper (Landsat 5 TM), Landsat Enhanced Thematic Mapper Plus (Landsat 7 ETM+) and Terra/Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), acquired during 1987, 2000 and 2005, respectively, were used to detect and evaluate Hurghadas urban expansion. Five change detection techniques were tested to detect areas of change. The techniques considered were image differencing, image ratioing, image overlay, multidate principal component analysis (PCA) and post-classification comparison. The post-classification comparison was found to be the most accurate procedure and produced three land use/land cover (LULC) maps of the years 1987, 2000 and 2005 with overall accuracies of 87.8%, 88.9% and 92.0%, respectively. The urban expansion analysis revealed that the built-up area has expanded by ∼40 km2 in 18 years (1987–2005). In addition, 4.5 km2 of landfill/sedimentation was added to the sea as a result of the coastal urban development and tourist activities. The booming coastal tourism and population pressure were considered to be the main factors driving this expansion, and some natural and artificial constraints constrained the physical shape of the city. The expansion is represented by urban fringe development, linear, infill and isolated models. Topography, lithology and structures were also analysed as possible factors that influenced the expansion. The understanding of the spatial and temporal dynamics of Hurghadas urban expansion is the cornerstone for formulating a view about the future urban uses and for making the best use of the limited resources that are available.

Geometry and kinematics of deformation in the Albanian orogenic belt during the Tertiary

Abstract Geological survey and structural analysis across the Central and Northern Albanides allows us to establish the kinematic and strain history of the Albanian orogenic belt from the time of the Tertiary continental collision between the Apulian and European plates. Four main deformation events are distinguished: D1 occurred during the Eocene–Oligocene, causing SW vergent imbrication of the External Albanides associated with NE-ward back thrusting. During D1 compression, the Korabi zone of the Internal Albanides together with the overlying Mirdita ophiolites, overthrust onto the External Albanides. Crustal thickening accompanied D1 deformation. D2 took place during the Oligocene–Miocene and was related to crustal thinning and extensional exhumation of the footwall External Albanides, while plate convergence continued and compression migrated SW-ward to the more external parts of the Albanides. During D2 extension, Mirdita ophiolites detached downwards to SW, covering parts of the External Albanides. A younger D3 NE-SW shortening followed during the Middle–Late Miocene. Finally, high angle D4 normal faults strongly modified from the Miocene onwards the pre-existing deformation geometry of the Albanides. The Tertiary kinematic evolution of the Albanides is in good agreement with the Tertiary kinematics history of the Hellenides, revealing that the same geodynamic processes affected both regions during the Tertiary.

Complex rotational deformations in the Serbo-Macedonian massif (north Greece): structural and paleomagnetic evidence

Abstract Structural data concerning the neotectonic deformation of the Serbo-Macedonian massif suggest a possible counterclockwise rotation of the stress field which corresponds to a clockwise rotation of the geological structures. Such a rotation is confirmed by paleomagnetic data, providing a new, alternative interpretation of the geodynamic evolution of this area.

Geometry and structural evolution of the Mesohellenic Trough (Greece): a new approach

Abstract The Mesohellenic Trough (MHT) is an elongate basin parallel to the Hellenide isopic zones that extends from southern Albania through northern Greece. The basin developed from Mid-Late Eocene to Mid-Late Miocene time related to Alpine orogenic processes. Structural and kinematic evidence shows that the MHT developed in response to successive tectonic events, involving isostatic crustal flexure, strike-slip and normal faulting, all related to inferred oblique convergence of the Apulian and Pelagonian microcontinents. The Mesohellenic Trough evolved as a piggyback basin above westward-emplacing ophiolites and higher Pelagonian units. This differs from previous interpretations that envisaged foreland flexure related to backthrusting, or subsidence associated with asymmetrical flexure, or normal faulting. The first stage of basin development during the Mid-Late Eocene was contemporaneous with the final emplacement of Pindos oceanic units and culminated in deformation and uplift of Eocene strata. The second phase was dominated by strikeslip faulting during Oligocene-Early Miocene time. The third stage was characterized by low-angle normal faulting at the eastern boundary of the MHT during the Early-Late Miocene. The evolution of the sedimentary basin ended around Late Miocene time, followed by rapid uplift and marine regression. A compressional event occurred during the latest Miocene. Finally, extensional tectonics affected the area from the Late Miocene to the present.

The recent crustal deformation of the Hellenic orogen in Central Greece; the Kremasta and Sperchios Fault Systems and their relationship with the adjacent large structural features [Die rezente Krustendeformation des Hellenischen Orogens im zentralen Griechenland; die Kremasta- und Sperchios- Störungssysteme und ihre Verhältnisse zu den benachbarten großen Bruchstrukturen.]

Kilias, A.A., Tranos, M.D., Papadimitriou, E.E. & Karakostas, V.G. (2008): The recent crustal deformation of the Hellenic orogen in Central Greece; the Kremasta and Sperchios Fault Systems and their relationship with the adjacent large structural features. (Die rezente Krustendeformation des Hellenischen Orogens im zentralen Griechenland; die Kremasta- und Sper- chios-Storungssysteme und ihre Verhaltnisse zu den benachbarten grosen Bruchstrukturen.) - Z. dt. Ges. Geowiss., 159: 533-547, Stuttgart. Abstract: The 70 km long WNW-ESE trending Kremasta and Sperchios Fault Systems cutting at high angle the Pindos Mountain range in Central Greece have been defi ned and mapped in detail. The geometry and kinematics of both fault sys- tems including normal faults that have been reactivated since Quaternary defi ne a contemporary N-S extensional stress re- gime. In more regional scale, both the Kremasta and Sperchios Fault Systems represent an underlapping extensional zone between the Cephalonia Transform Fault and the North Anatolia Fault and form with the Corinth Gulf Fault System in Cen- tral Greece antithetic domino-type trailing faults in respect to the SSW-wards motion of the Aegean block. Kurzfassung: Es wurden die 70 km langen WNW-ESE streichenden Kremasta- und Sperchios-Storungssysteme, die schrag mit einem hohen Winkel das Pindos-Gebirge im zentralen Griechenland schneiden, ausfuhrlich untersucht und kartiert. Die Geometrie und Kinematik beider Storungssysteme, die aus wahrend des Quartars reaktivierten Abschiebungen bestehen, defi nieren ein modernes N-S streichendes Extensions-Spannungsregime. Im regionalen Masstab sind die Kremasta- und Sperchios-Storungssysteme als eine Extensions-Verbindungsbruchzone zwischen den Kephalonia- und nordanatolischen grosen dextralen Blattverschiebungen anzusehen. Die Kremasta- und Sperchios-Storungssysteme bilden zusammen mit dem Abschiebungssystem des Golfs von Korinth ein antithetisches Dominotyp-Storungssystem im Zusammenhang mit der nach SSW gerichteten Bewegung des Agaischen Blocks ab.

Fission track data from the Mesohellenic Trough and the Pelagonian zone in NW Greece: Cenozoic tectonics and exhumation of source areas

The Mesohellenic Trough (MHT) trends parallel to the structural fabric of the Hellenides and covers the suture between the Apulian microplate and the Pelagonian block. It comprises an up to ∼4 km thick middle Eocene to upper Miocene sedimentary sequence. We have studied the thermal history of the Pelagonian basement and the provenance of the detrital material in the clastic sediments of the MHT by fission track dating. Apatite and zircon fission track (AFT, ZFT) analysis is applied to samples from the Pelagonian microcontinent along the eastern border of the MHT, and AFT analysis to the sedimentary rocks in the southern MHT. Eocene AFT age populations in the sedimentary strata indicate a proximal position of the Pelagonian microcontinent, which shows the same or even younger AFT ages, as the source area of the detrital material in the MHT. Late Cretaceous to Palaeocene age populations point to a more distant or structurally higher (now eroded) source area. The Eocene orogenic event caused only weak thermal overprinting in rocks of the Pelagonian microcontinent. In its eastern part, the AFT ages show only partial resetting, if any, whereas in its western part the ages were clearly reset during the Eocene event. AFT age‐elevation relations, correlation of zircon and apatite FT ages from the same samples, and thermal modelling based on AFT ages and track length distributions were all used to reconstruct the low‐temperature cooling history of the Pelagonian basement adjacent to the MHT. The results document fast cooling and exhumation in the Eocene that were possibly related to thrusting and associated erosion, followed by slow cooling and exhumation during Oligocene and Miocene time. This scenario is confirmed by the AFT data from the detrital material in the MHT sedimentary strata. The slow cooling period coincides with a stagnation period or crustal extension and possible reheating, which is probably also responsible for the partial rejuvenation of the ages of the detrital apatites in the oldest (Eocene) formation in the sediment sequence of the MHT.

Support of unstable wedges along the Platamon railway tunnel under construction, in northern Greece

Abstract In this paper, support measures obtained with the RMR classification method were used for estimating the support capacity of wedges found in relatively shallow tunnels. This was done for the Platamon railway tunnel, in northern Greece, which is at present, under construction. According to our investigation, the safety factors, which were calculated using the above mentioned support measures, were much higher than the theoretically needed safety factor. In cases where the height of the wedges is much greater than their base and the rockmass quality is very poor, the proposed RMR support measures could be introduced. In these cases, additional techniques, which include steel ribs and shotcrete (together with rock bolts), could be used.