ΤΗE PELAGONIAN NAPPE PILE IN NORTHERN GREECE AND FYROM. STRUCTURAL EVOLUTION DURING THE ALPINE OROGENY: A NEW APROACH

The geometry of kinematics and the deformation history of the Pelagonian nappe pile during the Alpine orogeny have been studied in Northern Greece and FYROM. Deformation was started in Middle-Late Jurassic time and was initially associated with ocean-floor subduction followed by ophiolites obduction, nappe stacking and duplication of the Pelagonian continent. The footwall Pelagonian segment from top to bottom was metamorphosed under greenschist to amphibolit facies conditions and a relative high pressure (T = 450o to 620o C and P = 12,5 to 8 kb). Blueschist facies metamorphic assemblages of Late Jurassic age are immediately developed between both hangingwall and footwall Pelagonian segments. Transgressive Late Jurassic-Early Cretaceous neritic limestones and clastic sediments on the top of the obducted ophiolites are maybe related to extension and basins formation simultaneously with the nappe stacking and metamorphism at the lower structural levels of the Pelagonian nappes. Contractional tectonics and nappe stacking continued during the Albian-Aptian time. Simultaneously retrogression and pressure decreasing taken place at the tectonic lower Pelagonian footwall segment. Low grade mylonitic shear zones, possible related to extension, are developed during Late Cretaceous time simultaneously with basins formation and sedimentation of neritic Late Cretaceous to Paleocene limestones and flysch. Intense shortening and imbrication under semi-ductile to brittle conditions occurred during Paleocene to Eocene time resulting the onset of the dome like formation of the footwall Pelagonian segment. The next stages of deformation from Oligocene to Quaternary are related to brittle extension and the final uplift and configuration of the Pelagonian nappe pile

The Mesohellenic trough and the Thrace Basin. Two Tertiary molassic Basins in Hellenides: do they really correlate?

Με βάση τη λιθοστρωματογραφία, την τεκτονική ανάλυση και τη γεωλογική χαρτο- γράφηση συγκρίθηκαν μεταξύ τους, οι μολασσικές λεκάνες της Θράκης (ThB) στη ΒΑ Ελλάδα (συμπεριλαμβάνονται οι Παλαιογενείς αποθέσεις της λεκάνης Αξιού) και της Μεσοελληνικής Αύλακας. Αμφότερες οι λεκάνες χαρακτηρίζονται από μια παχειά, μολασσικού-τύπου ιζηματογενή ακολουθία (3-5 km πάχος) Τριτογενούς ηλικίας, που καλύπτεται ασύμφωνα από Νεογενή και Τεταρτογενή ιζήματα. Η μολασσκή ιζηματογένεση αρχίζει σχεδόν ταυτόχρονα και στις δύο περιοχές κατά τη διάρκεια του Μέσου- Άνω Ηωκαίνου όμως σταματάει σε διαφορετικούς χρόνους, στο Μέσο-Άνω Μειόκαινο για τη ΜΗΤ και στο Άνω Ολιγόκαινο για τη ThB. Η ιζηματογένεση στη ThB συνοδεύτηκε επί πλέον από έναν ασβεσταλκαλικής και τοπικά σωσωνιτικής σύστασης μαγματισμό, Ηωκαινικής-Ολιγοκαινικής ηλικίας. Ερμηνεύσαμε τη ΜΗΤ ως μια πολυιστορική οριζόντιας μετατόπισης, piggy-back λεκάνη, που αποτέθηκε επάνω σε οφιόλιθους και στο Πελαγονικό κάλυμμα κατά την προς τα δυτικά τοποθέτησή τους πάνω στο κρύο πρίσμα επαύξησης των Ελληνίδων. Αντίθετα, η ThB αναπτύχθηκε ως μια Παλαιογενή λεκάνη, πάνω σε ρήγμα διαφυγής και στις γεωλογικές ενότητες των εσωτερικών Ελληνίδων, κατά τη διάρκεια της Ηωκαινικής-Ολιγοκαινικής έκτασης των Εσωτερικών Ελληνίδων. Ο σύγχρονος με την ιζηματογένεση μαγματισμός, πιθανόν, συνδέεται με τις ορογενετικές διαδικασίες υποβύθισης του ωκεανού της Πίνδου ή του Αξιού. Σε κάθε περίπτωση ΜΗΤ και ThB αναπτύχθηκαν κατά τη διάρκεια πλάγιας σύγκλισης της Απουλίας πλάκας και των Εσωτερικών Ελληνίδων.Based on lithostratigraphic and structural data, as well as geological mapping, the mollasic Thrace Basin (ThB) in NE Greece (including the Paleogene deposits of the Axios Basin) was compared with the Mesohellenic Trough (MHT) in NW Greece. Both basins are characterized by a thick sedimentary sequence of molassic-type strata (3-5km thickness) of Tertiary age, overlain unconformably by Miocene- Pliocene and Quaternary deposits. Molassic sedimentation started almost simultaneously in both areas during the Mid-Upper Eocene but it finished in different time, in the Mid-Upper Miocene for the MHT and the Upper Oligocene for the ThB, respectively. Sedimentation in ThB was also linked with an important calc-alkaline and locally shoshonitic magmatism of Eocene-Oligocene age. We interpreted the MHT as a polyhistory strike-slip and piggy-back basin, above westward-emplacing ophiolites and Pelagonian units on the cold Hellenic accretionary prism. In contrast to MHT, the ThB evolved as a Paleogene supra-detachment basin above the strongly extended during the Eocene-Oligocene Hellenic Hinterland. The syn-depositional magmatic products, linked possibly with subduction processes in Pindos or Axios ocean(s). In any case, MHT and ThB are related to inferred oblique convergence of the Apulia plate and the internal Hellenic units

Analysis of potential field anomalies in Lavrion mining area, Greece

Mining activities in Lavrion began during the first millennium B.C, after the decline of ancient Athens and then restarted more deliberately during the nineteenth century. Aeromagnetic data from a 1967 survey of the mining area was recompiled, processed, and interpreted for the present study. The original flight lines were digitized and leveled, and the international geomagnetic reference field (IGRF) was removed. The data were inverted by means of a terracing technique that defines separate domains of uniform distribution of physical properties that cause the magnetic anomalies. The log power spectrum was computed; along with the results of terracing, it suggested the existence of two sources of the magnetic anomaly. The long-wavelength anomaly reflects a large, concealed body that is most probably a granitic intrusion, consistent with local geological evidence. The source of the short-wavelength anomaly is a strongly magnetized body attributed to the net effect of various thin, magnetite-bearing sulfide zones. The anomalies were then separated in the wavenumber domain. Magnetic susceptibility measurements were made in situ on the exposed parts of the local formations. Three-dimensional models whose effect simulates the observed anomalies were calculated. Results of the modeling show that the large magnetic body is buried at 0.68 km depth. The small, relatively shallow body is about 0.035 km thick and buried at 0.6 km depth. The bodies do not show any corresponding gravity anomaly on the regional Bouguer gravity anomaly map