Palaeoenvironmental significance of a late Miocene benthic foraminifera fauna from Apostoli Formation, Central West Crete, Greece

The palaeoenvironmental and palaeoecological reconstruction of the Apostoli Basin (Crete, Rethymnon Region) during early Late Miocene by means of benthic foraminifers is given. Biologically important factors, such as oxygen and nutrient content of sea-water, played a great role in the evolution of the palaeoecosystem. A gradual deepening took place during the deposition of the Apostoli Formation. The sediments of the lower part of the formation document a shallow-marine environment with vegetation in the neighborhood. In the middle part of the formation sediments are characterized by intermediate oxygenated conditions, whereas the upper part of it is characterized by the establishment of a restricted envrironment, where organic matter accumulates and infaunal opportunistic species capable of surviving in stressed conditions dominate, being favoured by abundant nutrients

Climatic vs tectonic control on the Early Late Miocene tectono-stratigraphic deposits of the Pre-Apulian Zone, Western Greece.

Στην εργασία αυτή διευκρινίζεται η σχέση μεταξύ τεκτονικής και κλίματος και η επιρροή τους στην ιζηματογένεση. Για το σκοπό αυτό μελετήθηκε ένας αριθμός θαλάσσιων δειγμάτων από μία τομή που βρίσκεται στο βόρειο περιθώριο της λεκάνης του Αγίου Πέτρου (Κατ. Τορτόνιο, Λευκάδα, Δυτική Ελλάδα), προκειμένου να διαπιστωθούν και να ερμηνευθούν οι παλαιοπεριβαλλοντικές και παλαιοβαθυμετρικές αλλαγές. Τα πρότυπα κατανομής των κυρίαρχων και των συναφών βενθονικών τρηματοφόρων (Siphonina reticulata και Cibicidoides kullenbergi), σε συνδυασμό με τον μειωμένο αριθμό βενθονικών τρηματοφόρων (BFN), την αυξημένη ποικιλότητα και την υψηλή αναλογία πλαγκτονικών-βενθονικών τρηματοφόρων, δείχνουν εναπόθεση στη βαθύαλη ζώνη με μέτρια εισροή οργανικής ύλης και αυξημένη περιεκτικότητα σε οξυγόνο. Οι ιζηματογενείς αποθέσεις της λεκάνης του Αγίου Πέτρου, ηλικίας Κατώτερο Τορτόνιο σχετίζονται με την προς τα δυτικά προέλαση της Ιόνιας ζώνης η οποία προκάλεσε κάμψη λόγω φόρτισης και την επακόλουθη άνοδο της σχετικής στάθμης της θάλασσας.Here, we elucidate the relationship between tectonics and climate and their influence on sedimentation. A number of marine sediment samples were collected from a section located in the northern margin of the Agios Petros Basin (Early Tortonian, Levkas Island, W. Greece) for micropalaeontological analysis, in order to establish and interpret of the palaeoenvironmental and palaeobathymetric changes. The distribution patterns of the dominant and associated benthic foraminiferal species (Siphonina reticulata and Cibicidoides kullenbergi), together with the decreased Benthic Foraminiferal Number (BFN) values, elevated diversities and higher planktonic- to-benthic ratios, suggest deposition at bathyal water depths with moderate organic matter fluxes and elevated oxygen contents of the bottom water, typical for this water depth interval. The early Late Miocene infilling of the Agios Petros basin is related to the westward advances of the Ionian zone which induced flexural loading and subsequent relative sea-level rise

Planktonic foraminiferal ecozones: response of the pelagic environment to palaeoclimatic changes in the eastern Mediterranean Sea

A detailed study of the planktonic environment of the eastern Mediterranean Sea has permitted the reconstruction of the climatic history of this part of the basin during the time span from 9.7 to 6.6 Ma. The eastern Mediterranean Sea is confirmed as having a strong sensitivity to the climatic changes that occurred during that timespan. One of the very few complete hemipelagic successions of the Upper Miocene in Mediterranean is found in Gavdos island (SW Crete). Quantitative and qualitative modifications of the planktonic foraminiferal communities observed in Metochia section exhibit a sequence of biological events summarized in 11 successive main time intervals. The bioevents are defined by frequency peaks and/or local (re)-occurrences or (temporary) disappearances of some of the taxa, in association with more or less important fluctuations of the more common species. The planktonic foraminifera show a strong correlation with sea surface temperature variations and with changes in the physical and chemical properties of the upper water column caused by the climatic instability. Two prominent shifts in faunal parameters divide the period recorded in Metochia section into three major time slices that are discussed in chronological order: a cooling trend from 9,7 to 7,6 Ma, a warmer period from 7,6 to 7,2 Ma and then a cooling trend which finishes at the Messinian

MIOCENE SCLERACTINIAN CORALS OF GAVDOS ISLAND, SOUTHERN GREECE: IMPLICATIONS FOR TECTONIC CONTROL AND SEA-LEVEL CHANGES

Low-diversity scleractinian patch reefs that have been developed, during Early to Middle Tortonian, in Gavdos island are studied, aiming in a better understanding of the time and space relationships of the reef development and the associated basin fill evolution. Gavdos island consists part of a tectonically active setting constituting the southernmost extension of the Hellenic arc (Eastern Mediterranean). A representative Tortonian section (Bo section), located in the northwest part of the island, which hosts a mass occurrence of hermatypic corals, is studied. Scleractinian samples were collected from the upper 12 m of the section, which is characterized by interchanges of marly limestone and compact marls. The reefs are represented by the coral species Heliastraea oligophylla, Porites maicientensis, Thegioastraea roasendai and Porites collegniana. The microfacies analysis showed that the mediumto-thin-bedded carbonates of the limestone-marl alternations comprise patch reefs (boundstones-framestones, SMF 16, sensu Wilson, 1975, FZ 7-8, sensu Flügel 1982) consisted of screractinian corals. Corals are associated with corallinacean algae. Patch reefs are associated by bioclastic packstones-floatstones, characterized by benthic foraminifera, calcareous algae, spines of echinoids, gastropods and molluscs. Reefs are laterally associated by a bioclastic limestone rich in planktonic forams, associated by detrital material (fragments of quartz, feldspars, quartzites and cherts). The studied reef facies have been dolomitized and cemented in the meteoric realm. In places pseudomorphs after evaporites have been observed, tending to occlude cavities resulted after dissolution. The depositional environment corresponds to a moderate to high-energy inner platform setting, experiencing open-ocean influences. The pattern of coralgal reef development during Miocene, in the tectonically controlled Gavdos island, represents a complex interaction of tectonic activity and global sea-level changes