Source rock potential of the late Miocene Metochia Formation of Gavdos Island, Greece

Rock-Eval method was used to analyze 53 samples from late Miocene Metochia Formation of Gavdos Island (south of Crete Island) in order to characterize the contained organic matter and to evaluate its potential as source rock. The samples were collected from Metochia Section which consists of about 100 m thick marlssapropels alternations. Organic matter analysis showed that the studied succession could be subdivided into two parts. The lower one, which is generally rich in organic matter and the upper one, which is poor. In the lower part the rich horizons in organic matter are characterized by Kerogen type II, III and IV, with low oxygen content, and with fair to very good potential for gas and/or oil hydrocarbon generation. Additionally, the studied samples are thermally immature. Taking into account that the studied area has never been buried in such a depth to reach conditions of maturation, as well as, that the studied section in Gavdos is connected with Messara basin located in the northeastern and, finally, that the main part of Gavdos basin, which is situated between Gavdos and Crete islands, has continuously encountered subsidence, we could conclude that sediments of Metochia Formation could act as source rocks but in the more deep central part of the Gavdos basin. Key words: Neogene, Rock-eval pyrolysis, Organic matter. Η μέθοδος πυρόλυσης Rock-Eval χρησιμοποιήθηκε για την ανάλυση 53 δειγμάτων από τον Άνω Mειοκαινικό σχηματισμό των Μετοχίων της Γαύδου (νότια της Κρήτης) ώστε να εκτιμηθεί το δυναμικό του ως μητρικό πέτρωμα υδρογονανθράκων. Τα δείγματα ελήφθησαν από την τομή Μετόχια η οποία αποτελείται από μία παχιά ακολουθία, περίπου 100 m, εναλλαγών μαργών-σαπροπηλών. Η ανάλυση του οργανικού υλικού έδειξε ότι η μελετώμενη ακολουθία θα μπορούσε να χωριστεί σε δυο μέρη. Tο κατώτερο το οποίο είναι γενικά πλούσιο σε οργανικό υλικό και το ανώτερο το οποίο είναι φτωχό. Στο κατώτερο τμήμα οι πλούσιοι σε οργανικό υλικό ορίζοντες χαρακτηρίζονται από κηρογόνο τύπου II, III και IV, με χαμηλό περιεχόμενο οξυγόνο, με μέτριο έως πολύ καλό δυναμικό για την παραγωγή αέριων και υγρών υδρογονανθράκων. Επιπρόσθετα, τα μελετώμενα δείγματα είναι θερμικά ανώριμα. Λαμβάνοντας υπόψη ότι η περιοχής μελέτης δεν βρέθηκε σε τέτοιο βάθος ώστε να φτάσει σε συνθήκες ωρίμανσης, ότι η μελετώμενη τομή στην Γαύδο συνδέεται με την ΒΑ ευρισκόμενη λεκάνη της Μεσσαράς και τέλος ότι το κύριο τμήμα της λεκάνης της Γαύδου, το οποίο βρίσκεται μεταξύ Γαύδου και Κρήτης, υπέστη συνεχώς καταβύθιση, μπορούμε να υποθέσουμε ότι τα ιζήματα του σχηματισμού των Μετοχίων θα μπορούσαν να λειτουργήσουν ως μητρικά πετρώματα αλλά στο βαθύτερο κεντρικό τμήμα της λεκάνης της Γαύδου

Drainage evolution and river flooding related to tectonic and human activities

Flooding events accompanied by destruction of human infrastructure many times are related with evolution of river drainage. If towns were built or will be built on or near an abandoned channel it is dangerous because if this channel is the misfit element of a reverse drainage basin, it could change again to its original flow forming a re-established drainage. In this case, the abandoned channel could become active, and in the area of the wind gap large gorges could be formed, with consequent impact on human activities. Also, we can predict that in the next e.g. ?100 years: a) The reverse drainages of Olvios and Rethis rivers, will remain stable, whereas the antecedent drainage of Piros and Selemnos rivers could change to a reverse drainage

Depositional environments of tertiary turbiditic sediments in Metsovo Basin, NW Greece

Tertiary sediments in Metsovo area consist of submarine fan turbidite deposits accumulated in the proximal part of the basin and represent mostly inner fan. The most proximal part of the inner fan could be related to a shelf environment. Palaeocurrent data indicate mainly two directions. The main direction is SW and results mainly from groove marks. The second direction represents an WNW trend which results mainly from flute marks. The Metsovo area seems to have multiple feeders from North and East. The total thickness of the turbiditic deposits in Metsovo area is approximately 6800 m due to tectonic stacking and folding

GEOCHEMICAL CHARACTERIZATION OF SATELLITE HYDROCARBON FORMATIONS IN PRINOS-KAVALA BASIN (NORTH GREECE)

Στη λεκάνη Πρίνου-Καβάλας επικράτησαν ευνοϊκές συνθήκες γένεσης, μετανάστευσης και παγίδευσης υδρογονανθράκων ώστε να δημιουργηθούν οικονομικά εκμεταλλεύσιμα κοιτάσματα. Το κοίτασμα φυσικού αερίου Νότιας Καβάλας, όπως επίσης το κοίτασμα πετρελαίου Πρίνου αποτελούν αξιόλογα παραδείγματα. Στη λεκάνη αποτέθηκαν ιζήματα με τη δομή υποθαλάσσιου ριπιδίου που αναπτύχθηκε κατά το Ανώτερο Μειόκαινο. Οι τουρβιδίτες που φιλοξενούν τους υδρογονάνθρακες αποτέθηκαν σε περιβάλλον ιδιαίτερα αναγωγικό, με υψηλά ποσοστά θείου, ενώ εμφανίζονται κατά επανάληψη εβαποριτικές ενστρώσεις. Στη μελέτη αυτή, η οποία αποτελεί μέρος διδακτορικής διατριβής, εκχυλίσματα από δείγματα πετρωμάτων στρωματογραφικά αντίστοιχων με τους πετρελαιοφόρους τουρβιδίτες του Πρίνου, από δυο περιφερειακούς σχηματισμούς της L·κάvης, τους Έψιλον και Καλιράχη, μετά από εργαστηριακή ανάλυση, βρέθηκαν να εμφανίζουν κοινά χαρακτηριστικά σύστασης. Η αξιολόγηση των βιοδεικτών που αναγνωρίστηκαν φανερώνει ανώριμο οργανικό υλικό, απουσία βιοαποικοδόμησης, προέλευση από άλγη και περιορισμένη συμμετοχή χερσογενούς υλικού. Διαφοροποιήσεις χαρακτηριστικών γεωχημικών δεικτών όπως οι λόγοι πριστάνιο/φυτάνιο, ολεανάνιο/χοπάνιο καθώς και ο δείκτης στερανίων, πιθανώς υποδεικνύουν διαφορές στο τύπο του οργανικού υλικού, ή στο περιβάλλον απόθεσης. Ο προσδιορισμός του τύπου του οργανικού υλικού, της γένεσης των υδρογονανθράκων, των δρόμων μετανάστευσης και των παγιδεύσεων τους, για κάθε δομή στη λεκάνη Πρίνου-Καβάλας είναι κρίσιμα στοιχεία για τη διαμόρφωση ενός γεωλογικού μοντέλου και την περαιτέρω έρευνα υδρογονανθράκων σε αντίστοιχες λεκάνες του Βορίου Αιγαίου.Conditions favoring generation, migration and trapping of hydrocarbons generated economically significant reservoirs in Prinos-Kavala Basin. Prinos oil field and South Kavala gas field are characteristic examples. The submarine fan packed the basin during Upper Miocene. The hydrocarbons were accumulated in turbidites, deposited in a strongly reducing environment, with high sulfur concentration. Evaporates are also deposited before and after the turbidite system. In this study, which is part of a doctorate thesis, extracts retrieved from cored samples of two satellite formations in Prinos-Kavala Basin, Epsilon and Kalirahi, selected at the "Prinos equivalent" formations, have been analyzed, using geochemical methods, and found to exhibit common compositional characteristics. The analysis of biomarkers indicates that the bitumens are immature and non-biodegraded, while their origin is considered mainly algal, with minor terrestrial contribution. Variations on characteristic geochemical ratios between formations, such as Pr/Ph, Ts/Tm, oleanane/hopane and steranes index, are attributed to differences on the type of organic mater input, or the depositional setting of sediments. The identification of the organic matter type, the hydrocarbons generation, migration paths and traps of each structure within the basin is vital for the evaluation of a reliable model of the basin and further hydrocarbon exploration in North Aegean basin

TRIASSIC CARBONATE AND EVAPORITE SEDIMENTATION IN THE IONIAN ZONE (WESTERN GREECE): PALAEOGEOGRAPHIC AND PALAEOCLIMATIC IMPLICATION

The Triassic is considered a crucial interval because during that time huge areas in our planet suffered an intense, long lasting, period of aridity, which favored the formation of worldwide evaporitic bodies. During the Triassic, great volumes of evaporites were formed in the Ionian basin (Western Greece). On the surface chaotically textured gypsum, surrounded by dolomitic breccias of solution-collapse origin, appears. Sedimentological and diagenetical data proposed that these salt bodies were formed in an intertidal to supratidal environment. Although halite suggests precipitation under long-term arid conditions, clay film intercalations reveal intervals of short term humid conditions. During arid periods sabkhas prevailed and brines were of marine origin. Instead, during humid intervals brines were modified by meteoric water and stormy episodes could be responsible for the transportation of clay-sized material, from the low relief surrounding terrains, into the evaporative basin. Death and burial of cyanobactehal population during storm events could be responsible for the enrichment of clayey layers in carbonaceous material. The co-existence of halite and clays in the Ionian evaporitic sequence imposes a complicated climate, possibly periodically and seasonally controlled. The impact of the precession of the equinoxes plus the palaeogeographical position dominates the local climate. The insolation over the Triassic Ionian basin and nearby sea and land areas is a crucial factor. Climate responses to gradual insolation forcing with an ocean land atmosphere feedback mechanism. The desert / monsoonal dominated climatic model seems to be most proper for the explanation of the existing lithologigal record

THE TECTONO - STRATIGRAPHIC EVOLUTION OF PINDOS FORELAND EAST OF MESOLONGI

Η ιζηματολογική ανάλυση των υποθαλασσίων ριπιδίων, βόρεια και νότια του ποταμού Εύηνου, ανατολικά της πόλης του Μεσολογγίου, έδειξαν διαφορετικές συνθήκες ιζηματογένεσης. Το νότιο τμήμα που εμφανίζεται μεταξύ των βουνών Κλόκοβα και Βαράσοβα, που επηρεάστηκε από τη δράση της επώθησης της Γαβρόβου, χαρακτηρίζεται από αδρομερείς αποθέσεις εσωτερικού ριπιδίου, τα οποία προέρχονται τόσο από την οροσειρά της Πίνδου όσο και από τα αναδυθέντα όρη της Κλόκοβας και Βαράσοβας. Η επώθηση της Γαβρόβου έλαβε χώρα κατά τη διάρκεια τη ιζηματογένεσης παράγοντας ενδολεκανικά υβώματα τα οποία επηρέασαν τη γεωμετρία της λεκάνης. Στο βόρειο τμήμα, οι αποθέσεις εξωτερικού ριπιδίου περνούν προς τα πάνω σε αποθέσεις εσωτερικού ριπιδίου και δεν παρατηρείται η επώθηση της Γαβρόβου να έχει επηρεάσει το τμήμα αυτό παρά μόνο η επώθηση της Εσωτερικής Ιόνιας ζώνης. Μεταξύ των δύο μελετηθέντων περιοχών, υπάρχει μία έντονα παραμορφωμένη περιοχή, πλάτους περίπου 1km, η οποία εκτείνεται παράλληλα στον ποταμό Εύηνο με μια ΑΒΑ διεύθυνση, δείχνοντας ότι πιθανά ο ποταμός Εύηνος κινείται πάνω σε ένα ρήγμα οριζόντιας μετατόπισης.Sedimetological analysis of submarine fan deposits, both north and south of Evinos River, east of Mesolongi town, showed that there are different sedimentological conditions. The southern part outcropped between Klokova and Varasova Mountains, influenced by Gavrovo thrust activity, is characterized by coarse grained inner fan deposits, and sourced both from Pindos chain and the uplifted Klokova and Varasova Mountains. Gavrovo thrust activity, took place during the sedimentation producing intrabasinal highs, changing basin geometry. In the northern part, where outer fan deposits passes upwards to inner fans, there is no obvious influence of Gavrovo thrust but mostly the influence of internal Ionian Thrust. Between the two studied areas there is a high deformed area, about 1km wide, trending parallel to the Evinos River in a ENE direction, showing that probable Evinos River flows on a strike-slip fault

TRIASSIC CARBONATE AND EVAPORITE SEDIMENTATION IN THE IONIAN ZONE (WESTERN GREECE): PALAEOGEOGRAPHIC AND PALAEOCLIMATIC IMPLICATION

The Triassic is considered a crucial interval because during that time huge areas in our planet suffered an intense, long lasting, period of aridity, which favored the formation of worldwide evaporitic bodies. During the Triassic, great volumes of evaporites were formed in the Ionian basin (Western Greece). On the surface chaotically textured gypsum, surrounded by dolomitic breccias of solution-collapse origin, appears. Sedimentological and diagenetical data proposed that these salt bodies were formed in an intertidal to supratidal environment. Although halite suggests precipitation under long-term arid conditions, clay film intercalations reveal intervals of short term humid conditions. During arid periods sabkhas prevailed and brines were of marine origin. Instead, during humid intervals brines were modified by meteoric water and stormy episodes could be responsible for the transportation of clay-sized material, from the low relief surrounding terrains, into the evaporative basin. Death and burial of cyanobactehal population during storm events could be responsible for the enrichment of clayey layers in carbonaceous material. The co-existence of halite and clays in the Ionian evaporitic sequence imposes a complicated climate, possibly periodically and seasonally controlled. The impact of the precession of the equinoxes plus the palaeogeographical position dominates the local climate. The insolation over the Triassic Ionian basin and nearby sea and land areas is a crucial factor. Climate responses to gradual insolation forcing with an ocean land atmosphere feedback mechanism. The desert / monsoonal dominated climatic model seems to be most proper for the explanation of the existing lithologigal record

STUDYING IN THE PAXOS ZONE THE CARBONATE DEPOSITIONAL ENVIRONMENT CHANGES DURING UPPER CRETACEOUS, IN SAMI AREA OF KEFALLINIA ISLAND, GREECE

The shallow-marine carbonate sequence of Sami (Kefallinia isl. Fig. 1) is a part of the Upper Cretaceous carbonate platform of the Paxi zone. Detailed lithostratigraphic and microfacies analysis of that sequence revealed clear periodicities and cyclicity. The high-resolution stratigraphic analysis has shown a number of lithofacies organized in groups (lithofacies associations), suggesting, on the whole, sedimentary environments ranging from lagoonal to peritidal context. The vertical arrangement of these lithofacies allowed the identification of a cyclic recurrence of the depositional and early diagenetic features, including a meteoric overprint on top of the elementary cycles. The cycles exhibit a shallowing upward trend from shallow subtidal to inter-supratidal and hypersaline facies, in a warm shallow marine environment