D. Mountrakis

Tectonic Development of the Eastern Mediterranean Region

The Eastern Mediterranean region is a classic area for the study of tectonic processes and settings related to the development of the Tethyan orogenic belt. The present set of research and synthesis papers by Earth scientist from countries in this region and others provides an up-to-date, interdisciplinary overview of the tectonic development of the Eastern Mediterrenean region from Precambrian to Recent. Key topics include continental rifting, ophiolite genesis and emplacement, continental collision, extensional tectonics, crustal exhumation and intraplate deformation (e.g. active faulting). Alternative tectonic reconstructions of the Tethyan orogen are presented and discussed, with important implications for other regions of the world. The book will be an essential source of information and interpretation for academic researchers (geologists and geophysicists), advanced undergraduates and also for industry professionals, including those concerned with hydrocarbons, minerals and geological hazards (e.g. earthquakes).

The Pelagonian Zone in Greece: A Polyphase-Deformed Fragment of the Cimmerian Continent and Its Role in the Geotectonic Evolution of the Eastern Mediterranean

Data from Macedonia (Greece), correlated with those reported from the Pontides (Turkey), indicate that the Pelagonian zone of the Hellenides represents a fragment of the Cimmerian continent which separated the Paleo-Tethys and Neo-Tethys Oceans. A Permo-Triassic age is suggested for separation of the Paleozoic continent and initial rifting in the two oceanic basins. As the Pelagonian zone represented the northwestern (European) end of the Cimmerian continent, the Paleo-Tethys and the northern branch of Neo-Tethys would have been very close to each other on either side of this zone. Thus both oceans at their European end closed within a short time of each other in the Late Jurassic-Early Cretaceous. The sequential development of the two oceans outlines a model for the geotectonic evolution of the Internal Hellenides in which a correlation of thrusting and folding phases is also given.

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.

Extensional tectonics of northwestern Macedonia, Greece, since the late Miocene

Tectonic field studies in the Florina-Ptolemais basin (northwestern Greece) were carried out in an attempt to define the regional stress tensors in selected areas affected by Neogene and Quaternary faulting, using recently proposed quantitative methods. The analysis allows us to distinguish two extensional phases in the area: a late Miocene-Pliocene one with a NESW average direction of extension: and a Pleistocene-Recent one with a NWSE direction of extension. We conclude that the principal stress axes α2 and α3 were interchanged in passing from one phase to the other. These results are reasonably consistent with results of studies carried out in other parts of the Aegean area, especially the south Aegean back-arc domain.

The seismic parameter b of the frequency-magnitude relation and its association with the geological zones in the area of Greece

Abstract The parameter b of the frequency-magnitude relation has been accurately calculated for each of the 21 seismic zones into which the Aegean and surrounding area (34°N–43°N, 18°E–30°E) has been divided on the basis of several seismotectonic criteria. These 21 seismic zones have been geographically separated into three (A, B, C) groups (regions), according to the values of the parameter b . The outer region (A) is characterized by a relatively high value (= 1.03) the middle region (B) by an intermediate value (= 0.84) and the innermost region (C) by a low value (= 0.60). The boundaries of these three groups of zones almost coincide with the boundaries of well-known geological zones. This observation is interpreted in terms of mechanical heterogeneity of the material, and of structural and stress conditions in the area.

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.

Surface Fault Traces, Fault Plane Solution and Spatial Distribution of the Aftershocks of the September 13, 1986 Earthquake of Kalamata (Southern Greece)

A shallow earthquake ofMS=6.2 occurred in the southern part of the Peloponnesus, 12 km north of the port of the city of Kalamata, which caused considerable damage. The fault plane solution of the main shock, geological data and field observations, as well as the distribution of foci of aftershocks, indicate that the seismic fault is a listric normal one trending NNE-SSW and dipping to WNW. The surface ruptures caused by the earthquake coincide with the trace of a neotectonic fault, which is located 2–3 km east of the city of Kalamata and which is related to the formation of Messiniakos gulf during the Pliocene-Quaternary tectonics. Field observations indicate that the earthquake is due to the reactivation of the same fault.A three-days aftershock study in the area, with portable seismographs, recorded many aftershocks of which 39 withMS≥1.7 were very well located. The distribution of aftershocks forms two clusters, one near the epicenter of the main shock in the northern part of the seismogenic volume, and the other near the epicenter of the largest aftershock (MS=5.4) in the southern part of this volume. The central part of the area lacks aftershocks, which probably indicates that this is the part of the fault which slipped smoothly during the earthquake.

Tectonic development of the Eastern Mediterranean region: an introduction

Abstract The Eastern Mediterranean is one of the key regions for the understanding of fundamental tectonic processes, including continental rifting, passive margins, ophiolites, subduction, accretion, collision and post-collisional exhumation. It is also ideal for understanding the interaction of tectonic, sedimentary, igneous and metamorphic processes through time that eventually lead to the development of an orogenic belt. Below, we will outline some milestones in the development of tectonic-related research in the Eastern Mediterranean region. We will mention how studies of the Eastern Mediterranean contribute to our understanding of fundamental tectonic processes and indicate how papers in this volume contribute to this aim. Current and emerging research themes will be highlighted. We will also outline the main alternative tectonic reconstructions of the region (see Fig. 1), and mention which of these the different contributors favour. Tethyan nomenclature remains controversial and we will suggest an appropriate informal terminology for the various oceanic basins that existed. An entrée to some of the key literature sources is also provided. Citations here are mainly to edited volumes, which provide access to this large subject area. Many of the papers in this book integrate and synthesize large amounts of geological information for extended periods of geological time. The papers are ordered in a general time sequence with a view to linking those that consider comparable tectonic setting and processes. The locations of the areas are shown in Figures 2 and 3. Figure 2 also shows the main sutures, and Figure 3 illustrates the main neotectonic elements of the region.

Neotectonic and seismological data concerning major active faults, and the stress regimes of Northern Greece

Abstract Northern Greece is an intracontinental region behind the Hellenic subduction zone, with widespread seismic activity (ranging from low to high), with strong destructive earthquakes of M ≥ 6.0 in historical to recent times. Geological and seismological data indicate that recent seismic activity is mainly localized along large, inherited, fault zones, which have transected Northern Greece since Oligocene-Miocene times. The main active fault zones in Thrace, and Eastern and Central Macedonia strike approximately east-west, with lengths of 40–120 km. Fault segments strike WNW-ESE to ENE-WSW and range from 10 to 30 km in length. In Western Macedonia the main active fault zones strike NE-SW to ENE-WSW with lengths of 40–60 km and consist of 10–30 km segments. The region’s strong earthquakes are usually associated with reactivation of these fault segments and are estimated at M = 5.6–6.5. Focal mechanisms and fault-slip data from the fault zones indicate a change in the trend of extension axes from NNE-SSW in Eastern Macedonia-Thrace to NNW-SSE in Western Macedonia. Thus, neotectonic and seismological data suggest that variations in fault patterns, as determined from the large inherited fault zones transecting Northern Greece, are the major factor governing this change in the trend of maximum extension. This interpretation is consistent with the long-lived arcuate shape of the Hellenic subduction zone.

Seismic fault geometry and kinematics of the 13 May 1995 Western Macedonia (Greece) earthquake

Abstract During the devastating earthquake of 13 May 1995, in the Kozani-Grevena area (Western Macedonia, Greece), many surface ruptures formed in the epicentral area. Most of these fractures were due to faulting, but some were secondary ground ruptures and landslides. Geological field work in the area has shown that the Aliakmon river neotectonic fault consists of several (three or more) fault strands: the Servia, the Rymnio and the Paleochori-Sarakina strands. Using geological criteria, all of these fault strands were judged to be active faults affecting recent (Holocene) deposits and scree. The main new surface fractures caused by the earthquake, and particularly those clearly of tectonic origin, follow systematically the traces of the last two neotectonic fault strands, forming a new fracture line. This tectonic line, trending ENE-WSW (N 70 °), coincides with the focal mechanism solution and the satelite image major lineament. Both the geological and instrumental seismological data suggest that the seismogenic fault is a segment of the Aliakmon river neotectonic fault zone situated among the villages of Rymnio, Paleochori, Sarakina, Kentro and Nisi. The total length of the reactivated fault segment is about 30km long overall and is separated from the non-activated Servia fault segment by a geometrical seismic segment barrier near the village of Goules. The seismic fault is a normal fault trending ENE-WSW and dipping to NNW, with high angle at the surface and low angle at depth. The majority of the epicentres of the seismic sequence were distributed on the hangingwall of this reactivated fault segment. Additionaly a series of subparallel antithetic surface fractures, mainly striking E-W or ENE-WSW and dipping to the South, following previous neotectonic strike-slip faults, were reactivated during the earthquake with the geometry of normal faults antithetic to the main seismic fault. The most important of these are the Chromio-Varis-Myrsina fracture line (length 15km), along the Vourinos corridor dextral strike-slip structure and the Felli fracture line (length 6 km) along the Felli sinistral strike-slip fault. An interpretation of the geometry and kinematics of the reactivated faults is shown in the proposed geological model with simplified cross sections.