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 USE OF STATISTICAL ANALYSIS IN THE LITHOSTRATIGRAPHY OF SUBMARINE FAN DEPOSITS. AN EXAMPLE FROM SOUTHEAST GREECE (KARPATHOS ISLAND)

Τα τελευταία χρόνια γίνεται προσπάθεια από πολλούς γεωλόγους στην κατεύθυνση της ποσοτικοποίησης και στατιστικής ανάλυσης των γεωλογικών δεδομένων. Ένα από τα πεδία αυτής της έρευνας είναι οι αποθέσεις υποθαλάσσιων ριπιδίων («φλύσχης»). Η στατιστική ανάλυση σε τέτοιου είδους αποθέσεις εστιάζεται κυρίως στο πάχος των στρωμάτων και έχει σαν στόχο τον προσδιορισμό παραμέτρων όπως το περιβάλλον απόθεσης, η πηγή τροφοδοσίας ιζήματος, οι υδροδυναμικές συνθήκες απόθεσης κτλ. Κύρια εργαλεία ανάλυσης είναι οι λογαριθμικές κατανομές του πάχους των στρωμάτων. Στην παρουσίαση δίνονται παραδείγματα διαφόρων ειδών λογαριθμικών κατανομών που έχουν προταθεί τα τελευταία χρόνια, καθώς και ένα παράδειγμα εφαρμογής τους σε αποθέσεις υποθαλάσσιων ριπιδίων στη ΝΑ Ελλάδα (Κάρπαθος).Examples of various types of statistical analysis of submarine fan bed thickness distributions that have been proposed in the past are reported, as well as an example of their application in Late Eocene-Oligocene submarine fan deposits of SE Greece (Karpathos Island). Generally, the sandstone bed thickness data measured in two outcrops of Karpathos submarine fans seems to follow power law (fractal) cumulative distributions. A deviation from the power law was observed as amalgamationprocedures become more frequent. These observations gave important information about Tertiary turbidite sedimentation in the area which probably was punctuated and had a single main sediment source. Information taken from statistical analysis of submarine fans bed thickness data has immediate applicability in hydrocarbon exploration because sandstones constitute ideal reservoirs

APPLICATION OF BED THICKNESS DISTRIBUTIONS IN LATE EOCENE-OLIGOCENE TURBIDITE DEPOSITS OF GREECE: SOME PRELIMINARY RESULTS

Μια απλή εφαρμογή των κατανομών πάχους στρωμάτων επιχειρήθηκε σε φυσικές τομές τουρβιδιτών Άνω Ηωκαινικής - Ολιγοκαινικής ηλικίας σε τρεις διαφορετικές περιοχές της Ελλάδας. Οι τρεις τομές που με^ήθηκαν βρίσκονται στο Ευηνοχώρι Αιτ/νίας (Δυτική Ελλάδα), το νησί της Καρπάθου (ΝΑ Ελλάδα) και το νησί της Λήμνου (ΒΑ Ελλάδα). Όλες οι τομές παρουσιάζουν παρόμοια ιζηματολογικά χαρακτηριστικά. Τρία είδη διαγραμμάτων χρησιμοποιήθηκαν: διάγραμμα λογαρίθμου- λογαρίθμου, λογαρίθμου-κλίμακας πιθανότητας και καμπύλης συχνότητας. Οι κατανομές του πάχους των στρωμάτων και στα τρία είδη διαγραμμάτων δείχνουν ομοιότητα ανάμεσα στους τουρβιδίτες Δυτικής και ΝΑ Ελλάδας και διαφορά τους από αυτούς της ΒΑ Ελλάδας. Το γεγονός αυτό πιθανά οφείλεται σε διαφορετική μορφολογία των λεκανών ιζηματογένεσης των τουρβιδιτών, λόγω διαφορετικών τεκτονικών διεργασιών.A simple application of bed thickness distributions was attempted in outcrops of Late Eocene-Oligocene turbidites in three dispersed localities of Greece. The three studied sections are located at Evinohori area (West Greece), Karpathos Island (SE Greece) and Limnos Island (NE Greece). All outcrops show similar sedimentological characteristics. Three types of plots were used: log-log, log-probability and frequency curves. Bed thickness data indicate similarity between West-SE Greece turbidites and discrimination from NE Greece turbidites which is attributed to different basin morphology due to different tectonic processes

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