Gavdos Island Research Articles

Stress precursors of the Messinian salinity crisis as recorded by calcareous plankton and geochemistry in the Eastern Mediterranean: The Upper Metochia section of the Gavdos Island (Greece)

The road to the Messinian salinity crisis was paved with increasing environmental stress in the Mediterranean marine realm. The nature and origin of the crisis of the marine biota is still matter of debate because the crisis itself hinders univocal paleoenvironmental reconstructions by selecting the most resilient taxa, which are generally adapted to a wide range of stresses. The commonly accepted hypothesis, recently reiterated, is that increasing salinity was the main factor eliminating the marine biota from the geological record and eventually leading to the deposition of evaporitic carbonates in the Eastern Mediterranean just before the onset of the crisis dated at 5.97 Ma. We suggest that stratification and increasing restriction (continental water influence), leading to strong variability of surface water conditions, better explain the 87Sr/86Sr excursion below the global ocean value and the pattern of calcareous plankton events in the uppermost portion of the Metochia section (Gavdos Island, Greece), from 6.24 to 5.95 Ma. The early reduction of foraminifera at 6.07 Ma, typical of relatively deep successions lacking primary gypsum during the first phase of the crisis, precedes a sequence of calcareous nannofossil events such as the influx of Braarudosphaera bigelowi at 6.168 Ma, the acme of Reticulofenestra perplexa at 6.058–6.018 Ma, and the peaks of Sphenolitus spp. and Helicosphaera carteri at 5.99 and 5.973 Ma, respectively. The peak of such opportunistic calcareous nannofossil and the foraminifer disappearance, commonly observed in both deep and shelf successions, closely approximate the onset of the Messinian salinity crisis, regardless the occurrence of the Primary Lower Gypsum unit, and is interpreted as the final restriction step, which led to a 600 ky environmental perturbation culminating with the deposition of the Mediterranean salt giant.

A fossil assemblage from the mid-late Maastrichtian of Gavdos Island, Greece, provides insights into the pre-extinction pelagic ichthyofaunas of the Tethys.

The global body-fossil record of marine 'fishes' from the time interval immediately preceding the Cretaceous-Paleogene Extinction is markedly poor. This deficiency appears to be further exacerbated with regards to offshore and deep-water taxa, obscuring our understanding of the state and composition of corresponding vertebrate faunas at the onset of this major extinction event. Recent fieldwork in the mid-late Maastrichtian exposures of the Pindos Unit in Gavdos Island, Greece, yielded a small but informative sample of fossil 'fishes', which inhabited the Tethys approximately three to four million years before the extinction. In this work we describe this sample, which comprises between eight and nine discrete morphotypes of various size classes, belonging to †Ichthyodectoidei, Aulopiformes (†Dercetidae, †Enchodontidae, †Ichthyotringidae), cf. †Sardinioididae, as well as the hexanchid shark †Gladioserratus sp. The new material expands the faunal list for the Maastrichtian of Gavdos Island, and the Pindos Unit as a whole, and further allows for the description of a new genus and species of †Enchodontidae and a new species of †Ichthyotringidae. The two new taxa are found to be widespread in the Maastrichtian of the Pindos Unit. The overall character of the assemblage agrees with previous interpretations of an offshore and rather deep depositional environment for the fossiliferous horizons. Furthermore, it exhibits a higher diversity than, and little taxonomic overlap with penecontemporaneous teleost assemblages from the Tethys, and informs on the otherwise poorly known Maastrichtian offshore and deep-water marine ichthyofaunas of the region.

The Messinian of Agios Myron (Crete, Greece): A key to better understanding of diatomite formation on Gavdos (south of Crete)

The Agios Myron section in the NE of the Heraklion Basin on central Crete exposes a pre-evaporitic Messinian sequence of 24 sedimentary cycles of deep-marine homogeneous and laminated marls (sapropels). Planktonic foraminiferal biostratigraphy and ash layers show that the 24 cycles in section Agios Myron correlate to cycles M79 to M102 in the well-studied and orbitally tuned Metochia section on Gavdos Island. The correlation of the cycle patterns in sections Agios Myron and Metochia not only provides tuned ages for sedimentary cycles, planktonic foraminiferal bioevents, and ash layers in Agios Myron, but also reveals that the diatomites in Metochia cycles M94-M102 have no equivalents at Agios Myron. The onset of diatomite formation on Gavdos at 6.72 Ma is shown to coincide with eutrophication and related to a restriction-imposed increase in salinity 20 kyr earlier at 6.74 Ma. Geographic differences in productivity and possibly also the better preservation potential of siliceous microfossils on the much deeper seafloor at the Metochia site are believed to explain why diatomites are present on Gavdos and absent in time-equivalent levels at Agios Myron.

Three (middle to) late Miocene plant macroremain assemblages (Pitsidia, Kassanoi and Metochia) from the Messara–Gavdos region, southern Crete

Based on macroremains, we describe three fossil plant assemblages from the Miocene of the Messara Basin (southern Crete) and the adjacent Gavdos Island. The palaeoflora of Kassanoi, which is the oldest (Messara Basin, Viannos Fm, Serravallian/early Tortonian), is documented mainly by leaf imprints, including a fern, a conifer (Tetraclinis cf. salicornioides) and 23 angiosperms. The assemblage is dominated by Daphnogene polymorpha, Podocarpium podocarpum and Myrica lignitum. The plant record from Pitsidia (Messara Basin, Ambelouzos Fm, early Tortonian) comprises thousands of specimens. The plant fossils are preserved as imprints often covered by an inorganic encrustation (replica). One alga, 2 ferns, at least 5 conifers and more than 45 woody angiosperms were identified. Dominant taxa are Myrica and Pinus pitsidiensis, documented by numerous vegetative and reproductive organs (Zidianakis et al., 2015, 2016). Leaves of oaks (Q. pseudocastanea, Q. kubinyii) and Daphogene polymorpha as well as twigs of Taxodium dubium are also fairly common. From the palaeoflora of Metochia, which is the youngest (Gavdos Island, Metochia Fm, middle Tortonian), (Mantzouka et al., 2015), we report further taxa, including Quercus mediterranea, Ziziphus paradisiaca and a palm (Sabalites sp.). The vegetation is assessed both empirically (phytosociologically) and by Integrated Plant Record (IPR) Vegetation Analysis. The reconstructed vegetation models are presented in detail and discussed in the context of the geological and palaeontological settings of the area. The climate is assessed based on the Coexistence Approach (CA) and the Climate Leaf Analysis Multivariate Program (CLAMP). The palaeoclimatic datasets reveal a warm temperate to subtropical climate, probably with a weak seasonal drought.

Absolute Calibration of the European Sentinel-3A Surface Topography Mission over the Permanent Facility for Altimetry Calibration in west Crete, Greece

This work presents calibration results for the altimeter of Sentinel-3A Surface Topography Mission as determined at the Permanent Facility for Altimetry Calibration in west Crete, Greece. The facility has been providing calibration services for more than 15 years for all past (i.e., Envisat, Jason-1, Jason-2, SARAL/AltiKa, HY-2A) and current (i.e., Sentinel-3A, Sentinel-3B, Jason-3) satellite altimeters. The groundtrack of the Pass No.14 of Sentinel-3A ascends west of the Gavdos island and continues north to the transponder site on the mountains of west Crete. This pass has been calibrated using three independent techniques activated at various sites in the region: (1) the transponder approach for its range bias, (2) the sea-surface method for the estimation of altimeter bias for its sea-surface heights, and (c) the cross-over analysis for inspecting height observations with respect to Jason-3. The other Pass No.335 of Sentinel-3A descends from southwest of Crete to south and intersects the Gavdos calibration site. Additionally, calibration values for this descending pass are presented, applying sea-surface calibration and crossover analysis. An uncertainty analysis for the altimeter biases derived by the transponder and by sea-surface calibrations is also introduced following the new standard of Fiducial Reference Measurements.

FORAMINIFERAL RECORD OF ENVIRONMENTAL CHANGES: PREEVAPORITIC DIATOMACEOUS SEDIMENTS FROM GAVDOS ISLAND, SOUTHERN GREECE.

The Messinian pre-evaporitic sedimentary succession of Gavdos island (Metochia section) is a nearly uninterrupted succession of marine sediments, dominated by finely laminated diatomaceous sediments, which are cyclically alternating with marlstone and white limestone beds. The purpose of this study is to analyze in detail the benthic and planktonic foraminiferal microfauna preserved in the sediments of this section. The qualitative and quantitative analysis of the planktonic foraminifera fauna allowed the recognition of seven bioevents, which have been astronomically dated for the Mediterranean. The base of the diatomitic succession in Gavdos Island is dated at 6.696 Myr, whereas its top at 6.0 Myr. Our results suggest that two environmental parameters are the most important factors that control the community structure of the benthic foraminiferal fauna: the food availability and oxygen concentration. In addition, local upwelling phenomena evidenced by signals from the benthic foraminifera and the distribution pattern of the planktonic G. bulloides may have played a role in the faunal density and composition

TORTONIAN CLYPEASTER FAUNA (ECHINOIDEA: CLYPEASTEROIDA) FROM GAVDOS ISLAND (GREECE

The Tortonian sediments of Gavdos Island (Greece) contain a rich and diverse echinoidfauna. Clypeasteroid (sand dollars) echinoids are an important component of this fauna and sixteen taxa are recognized. Of these, eleven species are new records for Gavdos Island. The present paper is an annotated species list along with notes on certain aspects of the ecology of the determined echinoderms.

“New Mediterranean Biodiversity Records” (March 2017)

This Collective Article presents information on 22 species belonging to 5 Phyla, arranged geographically from from west to east. The new records were found in 8 countries as follows: Spain: first record of the two scarcely known nemerteans Baseodiscus delineatus and Notospermus geniculatus in Formentera; Malta: second record of the alien fish Lagocephalus sceleratus; Italy: the alien polychaete Syllis pectinans and the isopod Paranthura japonica, as well as the cryptogenic opisthobranch Anteaeolidiella lurana, were found in the fouling assemblages along the docks of the port of Livorno. New decapod records are reported from Sicily (the alien Callinectes sapidus and the native Pachygrapsus maurus) and Apulia (Percnon gibbosus and Procambarus clarkii); the lesser amberjack Seriola fasciata extended its geographical range to the Egadi Isands and Siganus luridus was documented for the first time along the Ionian coasts of Apulia and Calabria. Slovenia: the first record of the alien bivalve Brachidontes pharaonis is reported, together with a survey of up to date Adriatic records. Greece: the first record of the gastropod Rhinoclavis kochi is reported from Gavdos island. In addition, two records of endangered and rare cartilaginous fish were reported, namely, the shark Hexanchus griseus and the ray Leucoraja fullonica, as well as additional records of Siganus luridus for Lesvos and Malleus regula and Fulvia fragilis from Astypalaia. Turkey: the black wing flyingfish Hirundichthys rondeletii is reported for the very first time from the Black Sea. Egypt: the Indo-Pacific crab Halimede ochtodes is reported as established in Port Said. In addition, biometric parameters and meristic counts are reported for Anthias anthias in Damietta. Cyprus: the alien opisthobranch gastropod Bursatella leachii is reported for first time.

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.

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.

Possibility of Zeroing CO<sub>2</sub> Emissions Due to Energy Use in Gavdos Island, Greece

The possibility of transforming Gavdos Island located south of Crete, Greece to a 100% renewable energies island has been investigated. Gavdos Island has few inhabitants but it hosts a large number of tourists during the summer. Due to the small size of the island the use of vehicles is limited. It has abundant local energy resources, mainly solar and wind energy, which are currently underutilized. Electricity is locally generated with diesel oil and its electric grid is not interconnected with the grid of Crete. Energy demand in the island has been estimated as well as the availability of various renewable energy resources. The most reliable and cost effective of them, including solar thermal, solar and wind power, solid biomass burning and high efficiency heat pumps have been indicated for achieving a 100% renewable island. Electric vehicles must also replace conventional vehicles in order to zero carbon emissions in transport. Since the power grid in the island is isolated, electricity storage is required and it could be obtained either with electric batteries or with a small hydro-pump storage system. The nominal power of the required solar-PV system for covering all the electricity needs in Gavdos island has been estimated at 848 KWp and the required electricity storage capacity was at 19.2 MWh.

A new late Miocene (Tortonian) flora from Gavdos Island in southernmost Greece evaluated in the context of vegetation and climate in the Eastern Mediterranean

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Palaeoecological and sedimentological characteristics of the Lower Tortonian scleractinian reef corals of Gavdos Island, southern Greece

Early Late Miocene coral assemblages from five outcrops of Gavdos Island, Southern Greece, are investigated with respect to their palaeoecological implications. Small patch reefs with Porites assemblage are a common feature of the low-diversity coral occurrences. The determined hermatypic colonies indicate a nearshore palaeoecosystem prevailing in a tropical to subtropical coastal sea at depths ranging from 5 to 50m with an average temperature of 22–26°C. Microfacially, the studied Scleractinian patch reefs are represented by Coral Framestones-Floatstones. The reefal facies has been affected by syndepositional processes (boring activities-micritization), as well as by post-depositional diagenesis in the meteoric realm (dissolution, cementation and intense pedogenesis). The palaeoecological and sedimentological analysis indicates a restricted to open-marine inner platform setting of moderate to high energy, possibly of ramp-type (inner-mid ramp). Coral reef growth took place mainly during stages of accommodation (i.e., transgressive episode, cycle 3.1 of Vail curve) and of relatively low siliciclastic input.

Reseda minoica(Resedaceae), a New Species from the Eastern Mediterranean Region

Reseda minoica Martín-Bravo & Jim. Mejías (Resedaceae), a new species from the eastern Mediterranean region, is described and illustrated. It is distributed in Crete (Gavdos Island), Cyprus and S Anatolia (Mersin), where it grows mostly on basic, occasionally schistose, substrates near the coast. It is included in Reseda sect. Phyteuma, a taxonomically complex group mostly containing narrow endemics from the western or eastern Mediterranean region. Reseda minoica has been confused with R. odorata, R. orientalis and R. balansae in Crete, Cyprus and Turkey. It can be distinguished from those by the lower number of stamens, seed size, colour of petals and indumentum. An identification key to the eastern Mediterranean taxa of Reseda sect. Phyteuma is provided.

Micropaleontological parameters as proxies of late Miocene surface water properties and paleoclimate in Gavdos Island, eastern Mediterranean

Micropaleontological parameters as proxies of late Miocene surface water properties and paleoclimate in Gavdos Island, eastern Mediterranean

Foraminiferal stratigraphy and palaeoecological implications in turbidite-like deposits from the Early Tortonian (Late Miocene) of Greece

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.

Foraminiferal biofacies and paleoenvironmental implications of the Early Tortonian deposits of Gavdos Island (Eastern Mediterranean)

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.

Palaeoenvironmental conditions preceding the Messinian Salinity Crisis: A case study from Gavdos Island

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.

THE APPLICATION OF CYCLOSTRATIGRAPHY AND ASTROCHRONOLOGY IN THE NEOGENE MARINE DEPOSITS OF EASTERN MEDITERRANEAN: METOCHIA SECTION (GAVDOS ISLAND)

Significant lithostratigraphical and micropaleontological signatures, of Milankovitchscale climatic changes are recorded in Miocene deep-sea sediments. As a case study, the Metochia Section, in Gavdos Island, which covers the time interval from 9.7 to 6.6 Ma, is used. This study emphasizes the sedimentological and micropaleontological characteristics of the section, attributed to Milankovitch-scale climatic changes. The short-term variations in climate and faunal composition are related to precession- controlled sedimentary cycles and the long-term trend in climate is related to eccentricity and obliquity cycles. Regional changes in sea surface temperature in combination with variations of solar insolation have caused the cyclical astronomical controlled pattern of Globorotalia species.

A new marine fish fauna from the pre-evaporitic Messinian of Gavdos Island (Greece)

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. Pour citer cet article : J. Gaudant et al., C. R. Palevol 5 (2006) .