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

Late Quaternary micropalaeontological record of a semi-enclosed marine basin, North Evoikos, central Aegean Sea

North Evoikos Gulf constitutes a deep (450 m) semi-enclosed basin in east-central Greece connected to the Aegean Sea via a 42-m sill to the north and a 40-m wide, 8-m deep channel to the south. Six gravity cores retrieved from different physiographic settings of the Gulf were analyzed for their benthic foraminiferal content, in order to reconstruct the local and regional palaeoenvironmental changes. Species Correspondence Analysis separates the foraminifera into 4 clusters: Cluster 1 is composed of Agglutinated species, Elphidium spp. and Ammonia beccarii; Cluster 2 is exclusively composed of Bulimina marginata; Cluster 3 consists of Bolivina spathulata and Bulimina costata and finally Cluster 4 comprises the 10 remaining species: Cibicides lobatulus, Cibicidoides pachyderma, Bulimina aculeata, Cancris oblonga, Melonis barleeanum, Chilostomella oolina, Cassidulina laevigata, Hyalinea balthica and Miliolidae. These clusters represent four distinct foraminiferal biofacies and are interpreted as reflecting different ecological conditions: Biofacies p-H corresponds to the proximal part of the shelf and it is characterised by the absence of foraminifera, skeletal debris and abundant peloids. Its topmost part shows an erosional surface, aged 32.4 ka, characterised by shell debris, and the appearance of few shallow marine benthic foraminifera. Biofacies Ia and Ib consist of a low-diversity Holocene assemblage which is mainly dominated by Textularia spp. and Elphidium spp., reflecting a low-energy restricted lagoon and the deeper water assemblage of B. marginata and H. balthica (Biofacies Ib) as well as by a mollusc assemblage dominated by Corbula gibba. These biofacies are only present in the mid-shelf setting. Biofacies II (Cluster 3: B. spathulataeB. costata) shows a possible positive correlation with nutrient contents and it exhibits a complementary pattern of distribution with Biofacies III (Cluster 4: B. marginata). Two main palaeoenvironmental settings were recognized: a) In the first setting dominated by Biofacies Ia and Ib, the succession of the benthic faunas is mainly controlled by the ongoing sea level rise; b) in the second setting, the species typical of shelf environment (C. laevigataeH. balthica) give way to opportunistic species (B. spathulata) and species that are more resistant to bottom water changes (B. marginata). This pattern is attributed to variations in the food chain and oxygenation. North Evoikos Gulf during the Uppermost Quaternary reflects a passive response to a globally fluctuating sea level that was not significantly modified by dramatic tectonic processes. Therefore, its palaeoceanographic evolution is primarily driven by climatic (eustatic) processes and accurately depicts local conditions