Abstract: North Evoikos Gulf, Greece, constitutes a land-locked, epicontinental and semi-enclosed basin, connected to the central-west
Aegean Sea through a strait, probably not allowing full exchange of intermediate and deep water masses. Benthic foraminifer analyses were carried out on a Late Quaternary core from the outer shelf of the basin with the aim to trace palaeoceanographic changes. The benthic foraminifer species percentage per sample was used to calculate two main biological proxies: the Benthic Foraminifer Oxygen Index (BFOI) and Benthic Foraminifer High Productivity (BFHP) proxy estimated by grouping benthic foraminifer taxa which are known to flourish under high Corg flux. The estimated values of BFHP and BFOI were controlled mainly by the abundance of bolivinid species which are generally considered as opportunistic and shallow infaunal species, tolerant to low oxygen conditions. The statistical analysis (Q-mode cluster analysis) singled out four time intervals each one characterized by certain levels of oxygenation and food availability. Time interval 1 (8513–8300 cal. yrs BP) is characterized by a mixed fauna of oxyphilic taxa and taxa that live in suboxic environment, indicating the existence of a relatively eutrophic system with a well-oxygenated sediment–water interface. Time interval 2 (8300 – 8100 cal.yrs BP) records a deterioration of conditions on sea-floor, testified by significant oxygen and biotic diversity decrease. Benthic foraminifer composition in Time interval 3 (8100 – 7000 cal. yrs BP) depicts environmental conditions still highly variable, yet with faunal indication of more stable conditions than during the previous interval. Finally, the benthic foraminifer assemblage of Time interval 4 (7000 – 3500 cal. yrs BP) is related to the high food supply and good bottom circulation. Our data suggest a strong linkage between the quantity and quality of the organic matter supplies, and the diversity and composition of the benthic foraminifer faunas. Moreover, this study clearly demonstrates that vertical tectonic movements need to be taken into account when reconstructing the late Quaternary palaeoceanography of this region.
Abstract: An integrated faunal and geochemical dataset has been generated by the study of a late Miocene (early
Tortonian) sedimentary section outcropping at Manassi, Levkas Island (eastern Mediterranean). Quantitative analysis of benthic foraminifers from the 25-m-thick section indicates changes of bottom palaeoecological conditions in this part of the eastern Mediterranean, during the analyzed time interval. Benthic foraminifer assemblages are typical of a bathyal environment and testify to relatively oxygenated conditions with low to moderate food supply alternating with periods with an increase in organic matter content. The long-term palaeoceanographic analyses indicate an anti-estuarine circulation model based on the benthic foraminifer and stable isotope results, which evolved in a strong estuarine circulation. The positive relationship existing between the plankton d18O and d13C, in most of the record, agrees well with the hypothesis of a variable contribution of runoff. In three stratigraphic levels, samples record heavy bottom water d18O and d13C values and light surface d18O values, representing a wet, warm, estuarine climate with a stratified water column. In two stratigraphic levels, samples have depleted d13C and d18O values for both surface and bottom waters. These two samples represent wet, warm climates with some ocean mixing and stratification. The stable isotope signal of foraminifer tests from the Manassi section was influenced by the global temperature changes, but the local factors also played an important role. The palaeoenvironments derived from stable isotope analysis in this study are interpreted as responses to the local tectonic instability together with monsoon intensities that enhanced continental runoff, characteristic for the time interval studied in the study area. Due to the limited data available from this study, no correlations with the precessional, obliquity, or eccentricity cycles can be made.
Abstract: In this paper two adjacent (Bo and Potamos) sections from the Early Tortonian of the island of Gavdos, Eastern Mediterranean, are extensively studied and compared as for their lithology and micropaleontological content with final aim their paleoecological and paleoenvironmental interpretation. These two sections are composed of clayey sediments and reefal limestones and of marls and sands of turbiditic origin, respectively. The qualitative and quantitative micropaleontological analyses that were realised in the contained benthic microfauna showed that the two sections are characterized by a shallowing upwards-general trend. However, the combined lithological and micropaleontological data suggest that, although adjacent, the two sections underwent different paleoenvironmental evolutions during the early Late Miocene: on the one hand, reef growth at the Bo shelf is suggestive of a current, providing warm, clear and low-nutrient waters to the shelf, and on the other hand, benthic foraminiferal assemblages from the Potamos shelf indicate cooler and eutrophic conditions, induced by enhanced river runoff and upwelling, impeding reefal promotion. This difference may be due to the separation of Bo and Potamos shelf by an island acting as a local oceanographic and biogeographic barrier.
Abstract: Assemblages of benthic foraminifera from one clastic succession in the Afales Basin (Ithaki Island, western Greece) were investigated to reconstruct palaeoenvironmental conditions during the Oligocene. The section consists of alternating hemipelagic marls and detrital deposits, designated as flysch-like beds, attributed to biostratigraphic Zones P20 and P21. Planktic percentages are mostly high (66-80%). Benthic foraminiferal assemblages comprise calcareous and agglutinated taxa (up to 15%). The prevalence of epifaunal foraminifera indicates good ventilation of the bottom water resulting from basin morphology, which enabled the undisturbed flow of water throughout the basin. Palaeodepth estimates imply bathyal deposition, from about 800 to 1200 m deep. The benthic foraminiferal fauna is of high diversity along the section, as is expected in deep marine environments. The abundances of the most common foraminiferal taxa (Cibicidoides spp., Oridorsalis umbonatus, Gyroidinoides spp., Stilostomella spp., Nodosariidae, Nuttallides umbonifera) are quite variable and imply generally oligotrophic to mesotrophic environmental conditions with variable organic flux.
Abstract: Sedimentological and eco-taphonomic attributes of the Lower Pliocene (Zanclean) regressive sequence exposed at Rafina Cliff near Pikermi in Attica, Greece, are analyzed in terms of their bearing on environmental conditions under which the large- to giant-sized balanid cirripedes Concavus (Concavus) concavus (DARWIN, 1854) [non BRONN, 1831] have profusely lived and become buried either scatterly through the sequence, or mass-aggregated in one, spectacularly structured bed of the Fossillagerstδtte type. All balanids, regardless of their solitary or clustered lifestyle, are post-mortem transported, abraded and/or bioeroded, and deposited in offshore tempestites during high-stand pulses. The burrows of the callianassid shrimp Upogebia, and of the ghost crab Ocypode, indicate short-termed, extremely shallow sub- to intertidal low-stand pulses. The whole sequence, being the uppermost part of the â€post-Pikermian’, Lower Pliocene (Zanclean) marine overflood, is composed of three, successively thinning, shallowing-up cyclothems, topped by sub- to intertidal and/or emersive episodes, the last of which is featured by beachrock horizons that terminate the regressive events preceding an encroachment of the potamogenic (fluvial and/or deltaic) regime.
Abstract: A marine sedimentary sequence of the Pakhiammos section that crops out in the Ierapetra Basin (eastern Crete, Greece)
is described here in detail for the first time. Diverse and abundant foraminifera have been recovered from the
Pakhiammos section. Planktonic species indicate that sediments span the interval from Zone MPL1 to above the
MPL1/MPL2 boundary (Zanclean, early Pliocene). R-mode cluster analysis identified three benthic foraminiferal assemblages
named by their dominant taxa: Bolivina spathulata, Cibicidoides pseudoungerianus, and Siphonina
reticulata assemblages respectively. Palaeoenvironmental implications of each assemblage and their stratigraphic distribution
allow the recognition of two fossil associations: a well-diversified Association A, representative of a stable marine
ecosystem, and a less diversified Association B, representative of a sapropel-like event. The deposition of
the sapropel-like interval suggests that sapropels resulted from the interaction between sea surface temperature variations,
productivity increases and reduced bottom water ventilation. This study represents the first report of early Pliocene
marine sediments in the Ierapetra Basin and contributes to the understanding of the evolution of the Neogene basins in
eastern Crete.
Abstract: The Messinian pre-evaporitic sedimentary succession of Gavdos Island (Metochia section) is a nearly uninterrupted succession of marine sediments, dominated by finely laminated diatomaceous marls, which are cyclically alternating with clayey diatomites and white diatomites. The qualitative and quantitative analysis of the planktonic foraminiferal fauna allowed the recognition of nine bioevents, which have been astronomically dated for the Mediterranean. The base of the diatomitic succession in Gavdos Island is dated at 6.722 Ma and the top at 6.015 Ma. The studied section contains benthic foraminiferal genera characteristic of an outer shelf to slope environment. The qualitative and quantitative analysis of this microfauna revealed three benthic foraminiferal fossil assemblages and the occurrence of allochthonous species transported into the bathyal environment by current activity. The cyclical pattern of the benthic foraminifera assemblages indicates that the studied sediments have been affected by repeated episodes of basin restriction characterized by low diversity benthic foraminifera populations, and a limited planktonic foraminifer association typified by shallow, surface-dwelling forms. This restriction was partly due to Antarctic cooling, which produced palaeo-Mediterranean sea-level oscillations during the Early Messinian, as a prelude to closure of the Atlantic connections. The relative impact of climatic versus tectonic control on sedimentation patterns within this basin is discussed.
Abstract: The Lower Tortonian Ag. Giannis section, in Gavdos Island, Greece, consists of an outer neritic to upper bathyal, marly hemipelagic sequence which is interrupted by thick turbidite-like sandy deposits. During deposition of the marly intervals, reworking was considerably reduced.
This paper contributes to knowledge concerning benthic foraminiferal response to dynamic sedimentary environments. Important palaeoecological information for benthic foraminiferal assemblages was gathered and analyzed in order to create a regionally consistent picture of the palaeoenvironment. Samples were analyzed statistically in order to identify the different palaeoenvironmental settings during turbiditic sedimentation. Undisturbed basal marls of the section are characterized by the predominance of a diversified Uvigerina striatissima assemblage typified by a broad variety of morphotypes with different inferred habitat preferences and feeding strategies, indicating rather well-oxygenated bottom waters. This environmental stability was subsequently disrupted by recurrent deposition of turbidite-like sands. A low-diversity Valvulineria complanata-Globobulimina sp. assemblage is dominant in this part of the succession, as these specialized endobenthic species could keep pace with high-energy sedimentary settings. Just above the turbidites, a “recolonization” fauna (Bolivina alata assemblage), composed entirely of infaunal elements is observed, indicating a nutrient-rich substrate. This oligotypic fauna is later replaced by a more diversified microfauna capable of occupying a wider range of ecological niches.
Abstract: Th e present study describes the early late Miocene paleoenvironmental evolution
and the main paleoclimatic trends of Gavdos Island (eastern Mediterranean)
reconstructed using planktonic foraminifera. Th e three stratigraphic sections
studied in this area are characterized by whitish to greyish marls and sands
(Potamos and Ag. Giannis sections) and by grey-bluish marls and reefal limestones
(Bo Section). Based on the distributional pattern of neogloboquadrinids
in the three sections, we attribute a lower Tortonian age to studied sediments,
corresponding to the interval ranging between 11.21 to 10.01 Ma. Four distinct
assemblages of planktonic foraminifera were identifi ed by Q-mode cluster
analysis. Th e succession of assemblages allows dividing each section into four
paleoceanographic stages: 1) a warm-oligotrophic stage characterized by the
prevalence of Globigerinoides obliquus-Globoturborotalita apertura; 2) a cooleutrophic
stage characterized by Neogloboquadrina acostaensis; 3) upwelling
conditions dominated by Globigerina bulloides; and 4) a relatively warm with
seasonal high productivity stage characterized by the N. acostaensis and Globigerinoides
trilobus. On the basis of planktonic foraminifera paleoclimatic indices,
paleoclimatic curves were constructed for each section. Our data suggest that,
although adjacent, the areas where the three sections are located underwent
diff erent paleoclimatic and paleoenvironmental evolution during early late
Miocene: Bo shelf is characterized by warmer, nearly oligotrophic conditions
compared to cooler and eutrophic conditions on the adjacent Potamos and
Ag. Giannis shelves. Th is diff erence is probably related to the presence of an
island between Bo shelf and the open sea which acted as a local oceanographic
and biogeographic barrier.
Abstract: The occurrence of fossil fishes in the Messinian diatomites of Gavdos Island (Greece) was recently observed. This fish fauna is dominated by the Myctophids, which constitute more than two thirds of the collected material. Among them, Myctophum (s. l.) licatae (Sauvage) is by far the most abundant, with more than 50% of the specimens. Although the mesopelagic components are overwhelmingly dominant, epipelagic fishes, like Syngnathus cf. albyi Sauvage, are also present. The composition of this fish fauna is indicative of a sedimentation influenced by the action of upwelling currents, an interpretation that is also suggested by the composition of the diatom flora.
Abstract: Although the occurrence of fossil fishes is known since more than one century in the Neogene of Gavdos Island (Greece), its composition remained hitherto unknown. The present study demonstrates that, in the Tortonian of Gavdos, the most abundant species is Bregmaceros albyi (Sauvage), which constitutes two thirds of the collected material. This fish fauna is indicative of an environment of moderate depth, probably corresponding to the external edge of the neritic zone, or possibly to the upper part of the continental slope.
Abstract: Changes in benthic foraminiferal and mollusk assemblages from the lower part of the Upper Pliocene of the Atsipades Section (Iraklion Basin, central Crete) were studied. The Atsipades Section represents a shallowing-upward sequence from outer shelf blue–gray clays at the bottom of the sequence, deposited below the storm wave base, to shallow inner shelf deposits affected by storm waves at the top. The foraminiferal assemblage at the bottom of the sequence is dominated by Bolivina spathulata, Bolivina dilatata and Uvigerinidae, a microfossil assemblage corresponding to the deepest deposits formed under dysoxic sea-floor conditions. Foraminiferal assemblages of the middle part of the section are highly diversified, predominantly Haynesina depressula, Cassidulina carinata and Reusella spinulosa. The top of the section is mainly characterised by Asterigerinata planorbis, Bolivina pseudoplicata, Cibicides lobatulus and Elphidium sp., a typically epiphytic foraminiferal assemblage which can be correlated with the presence of an algal covered sea-bottom. Within this general environmental trend, a minor shallowing cycle can be differentiated. The boundaries of this cycle can be inferred, based on a substantial microfossil assemblage change and on the coincidence of species diversity maximum and a planktonic/benthic (P/P + B) ratio peak. Nonetheless, upwelling currents and/or over-abundance of nutrients due to continental outflow could also contribute to increased diversity and P/P + B ratio. The character of the mollusk assemblages is in accordance with these trends. Moreover, the increase in diversity and in sculpture constitutes a clear indication of an increase in hydrodynamic energy related to a shallowing-upward trend.
Abstract: Biostratigraphy based on Bolboforma is applied for the first time in the Metochia Section, Gavdos Island, south of Crete (Greece). The sequence interval investigated spans, according to planktonic foraminiferal biostratigraphy, a time interval from 9.7 to 6.6 Ma (Late Miocene). Two Bolboforma species, one incertae sedis, and the Bolboforma intermedia Zone (7.7–5.6 Ma) have been identified. The B. metzmacheri Zone (9.7–7.7 Ma) has not been found in the s tudied section, may be due to palaeoecological reasons. Bolboforma specimens are shown to be useful both in stratigraphical and palaeoclimatological analysis.
Abstract: 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.
Abstract: The Apostoli Basin, in the central-west part of Crete, was formed as a fore-arc type basin related to the convergent plate boundary between the African and the Eurasian plates. Most of the Neogene sediments filling the basin were deposited in a terrestrial to shallow marine environment. The succession is a transgressive cycle, which culminates in the alternation of Rethymnon bioclastic limestones with marls, documenting the important Tortonian marine transgression.
The Rethymnon limestones are classified as a typical non-tropical carbonate lithofacies. Two particular lithofacies have been recognized: (a) a rhodalgal-type lithofacies, characterized by predominance of encrusting coralline algae and bryozoans, and (b) an echinofor-type lithofacies, characterized by predominance of echinoderms and/or benthic foraminifera. The coralline algae occur mostly as in situ spheroidal or branched rhodoliths, whereas benthic foraminifera are mainly represented by larger foraminifera. In both lithofacies, typical tropical carbonate elements are lacking. Skeletal elements consisted of low- and high-Mg calcite. Although the observed lithofacies possess many similarities with facies of non-tropical carbonates, the presence of large benthic foraminifera suggests development in a warm temperate biogeographic province.
The depositional environment corresponds to a shallow ramp, the sediments being deposited in a nearshore environment and under conditions analogous to those prevailing in the present-day circalittoral bottoms of the Mediterranean Sea. The main carbonate accumulation area is located at the factory area itself (rhodalgal-type sediments), and downslope from the factory area (echinofor-type sediments). In the classic zonation of Mediterranean benthic assemblages of Peres and Picard [Rec. Trav. Stn. Mar. (1964)], the rhodalgal-type sediments of the Rethymnon Fm correspond to the “Facies a Pralines”, developed in areas strongly controlled by currents (e.g., tops of plateaus), and the echinofor-type sediments to the “Detritique Cotier” bioclastic deposits, derived mostly by bioerosion and fragmentation of local and adjacent calcareous benthic communities.
Abstract: A data set, constituted by counted samples of benthic foraminifera, has been subjected to cluster and principal component analyses, in order to demonstrate the linkage between taxa distribution and pa-leoenvironmental gradients. The foraminiferal fauna from the Plio-Pleistocene Katakolon section in western Greece is dominated by inner to mid-shelf benthic forms, especially the rotallids, cibicids and buliminids. A cluster analysis of the species occurrences and relative abundances identified two major assem-blages, A to B, up section. Assemblage A is indicative of an oligotrophic biofacies dominated by A. beccarii whereas Assemblage B is indicative of a more eutrophic biofacies where B. marginata prevails. Our results suggest that oxygenation and trophic conditions of the near-surface sediments are the most important factors that control the community structure of the benthic foraminiferal fauna. In addition, upwelling phenomena evidenced by signals from the benthic foraminifera may have played a role in the study area.
Abstract: The study of fossil mammals of Lesvos Island can give us good paleogeographical results. Paleogeographic sketches that indicate the relative positions of various paleogeographic domains during some critical periods will describe the paleogeographic evolution of Lesvos Island during the Late Cainozoic, with emphasis on the Pliocene/Pleistocene period.
Abstract: Vertical trends in architecture and facies of delta systems are preserved in a clastic wedge of an expanding marine half-graben in which tectonics, eustatic sea-level change and climatic change are roughly known from independent evidence. The studied half-graben is situated on Crete (Greece) and part of a larger, E-W-trending extensional domain situated north of the Hellenic subduction zone. The extension seems to be related to the southward migration of the trench (roll-back) in early Late Miocene times. The infill pattern is discussed in the light of theoretical fault-growth models for expanding half-grabens.
The geometry of the half-graben fill is typically wedge shaped, with a thickness of nearly 1000 m near the fault scarp thinning to c. 50 m about 20 km away from the scarp. The lower part of the wedge (Stratified Prina Series) contains coarsening-upward units representing progradational, shallow-marine deltas. At the base of the wedge these units are thin and retrogradationally stacked. Upwards in the succession, the units become composite (coarsening-upward subunits), thicker and finer grained. The composite structure, the thickening and the fining trend is related to progressive increase in accommodation space inherent in fault growth.
Rapid deepening of the basin from the photic zone (evidenced by intercalated coral and stromatolite beds) up to a depth of 900 m started at the top of the Stratified Prina Series. The deepening continued over some tens of metres of marly sediments of the base of the Kalamavka Formation and may be related to structural collapse of the fault block. After the structural collapse, basin depth remained more or less constant and basin infilling occurred by progradation of deep-water delta systems. These systems are characterized by a muddy delta slope with channelized conglomerates, and by mainly aggradation of prodelta turbidites deposited in small lobes at the base of slope.
