Late Quaternary depositional history of the North Evvoikos Gulf, Aegean Sea, Greece

doi:10.1016/j.margeo.2006.07.004

Marine Geology

Volume 232, Issues 3–4, 7 November 2006, Pages 157-172

https://doi.org/10.1016/j.margeo.2006.07.004 Get rights and content

Abstract

A high-resolution seismic reflection survey was carried out in the North Evvoikos Gulf, a deep (450 m) semi-enclosed basin in east-central Greece connected to the Aegean sea via a 45-m sill to the north and a 30-m wide, 10-m deep straight to the south. This active extensional basin is bound by major normal faults, that switch polarity along strike, thereby controlling the asymmetric shape of the basin. The survey records show a continuous upper unit in the marine strata deposited since the post-glacial transgression on an erosion surface generated during the last glacial. The upper unit can be traced downslope into the basin plain where it merges into a unit of laterally continuous interbedded turbidites and hemipelagic deposits. The buried erosion surface has many terraces distributed over several depth zones, between 65 m and 165 m below present sea-level that are evidence for a fluctuating water level when, in the last glacial interval, the sill depth in the north was about 55 m below today's sealevel and the gulf became isolated from the Aegean Sea. Thus during the last 70 kyr the water level of the lowstand lakes fluctuated in correspondence with the Oxygen Isotope Stages (OIS) and the climatic conditions. In the dryer stages (OIS 4, 2) the lake water level was lower, in the wetter stages (OIS 1, 3) the lake water level was higher. These events are also correlated with sediment budgets input from the surrounding land to the basin.

Researches carried out in many other gulfs of variable depth in the Ionian and Aegean seas indicated presence of sills at today's depths between − 50 and − 70 m. The generation of these features is postulated as sedimentary as many sea level fluctuations ranged in this depth interval.

Section snippets

Introduction–objectives–regional setting

In recent years the Aegean region has inspired much research into its active continental tectonics, because this seismically active region is rapidly deforming. In central Greece, the most prominent extensional structures are the Gulf of Corinth and the Evvoikos Gulf, both WNW–ESE trending graben systems about 100 km long and bordered by discontinuous normal faults (Fig. 1; Roberts and Jackson, 1991). The Gulf of Corinth and the Neogene and Quaternary tectonic history of the region ashore of

Materials and methods

The principal data set comprises 306 km of single-channel, high-resolution analogue seismic reflection data, using both ORE 3.5 kHz and SIG sparker (500–1000 J) systems simultaneously. The data were recorded directly onto paper on a 500 ms TWT (two-way-time) scale for the sparker and a 250 ms TWT scale for the 3.5 kHz data. Navigation was by Loran-C with an accuracy of about 100 m. In addition we studied 417 km of sparker, Uniboom and 3.5 kHz data collected by The Institute of Geology and

Major fault systems and their morphological expressions

The North Evvoikos Gulf is connected with the Aegean Sea in the north via the Orei Straits with a sill at 45 m bsl (below today's sea level) and with the South Evvoikos Gulf in the south by a narrow 10 m deep passage at Chalkis (Fig. 2). Three major active normal fault systems (Fig. 1), the Thermopylae–Arkitsa (th–ar), Atalandi–Martinon (at–ma) and Aedipsos–Politika (ae–po) faults, constitute the boundaries of the Gulf (Fig. 1).

The S-dipping Aedipsos–Politika system forms the north shore of the

Submarine erosional terraces: evidence of previous lake levels

The unconformity described earlier displays many apparently erosional terraces, ranging in depth from 50 to 70 m bsl. Those terraces must have been formed when the level of the Aegean Sea was below that of the sill in the Orei Straits during the last glacial and early deglaciation before the Aegean Sea rose above the level of the Orei Straits sill. This level is now 45 m bsl, but the erosion surface underlying the transparent unit places the late glacial sill depth at about 55 m bsl (Table 1).

Conclusions

For the most part the North Evvoikos Gulf fault systems resemble the pattern of major faults for the entire region described by Roberts and Jackson (1991). Reflectors within the Maliakos Gulf and western North Evvoikos Gulf dip south towards the Thermopylae–Arkitsa fault system, reflectors within the central and eastern Gulf dip northeast towards the Aedipsos–Politika fault system and reflectors in the Gulf of Atalandi dip south towards the Atalandi–Martinon fault. Where changes in polarity of

Acknowledgements

This paper rests on data obtained during a marine survey carried out by the personnel of the Marine Geology Department of IGME. The seismic reflection records were processed by Andrew Smith at Cambridge under the guidance of the first author. Smith also obtained the auger cores from the coastal zone of the Bay of Atalandi. This material formed part of his doctoral thesis (Smith, 1994) but the thesis was not published because the author soon chose a totally different career and contact with him

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2024, Tectonophysics
Since the Pliocene, rift basins have developed in the North Evia region at the south-western extension of the North Anatolian Fault. North Evia, therefore, is a key area for investigating Plio-Quaternary deformation within the diffuse Anatolian-Aegean–Eurasian plate boundary. In this study, we present a detailed map of offshore faults in the North Evia region based on three seismic reflection surveys: an airgun (2004) and two very high-resolution Sparker (2017 and 2021) single-channel surveys. Careful and systematic interpretation of these datasets revealed i) the identification of a new basin (Skiathos Basin) located at the western extension of the North Anatolian Fault and ii) two main fault sets striking oblique to the active N–S-directed extension. The seismicity analysis of the study area reveals pure strike-slip displacements along faults previously identified as normal. The NW–SE-striking faults bordering the North Evia Gulf rift are characterised by left-lateral displacements, and the NE–SW faults present dextral focal mechanisms, following the kinematic character of the North Anatolian Fault. We show that dextral strike-slip deformation recently occurred (in the late Quaternary) in the south-western extension of the North Anatolian Fault, suggesting the significant role of this fault system in the complex structural development of the North Evia region.
Late Quaternary micropalaeontological record of a semi-enclosed marine basin, North Evoikos, central Aegean Sea
2014, Quaternary International
Citation Excerpt :
Sperchios River discharged its waters directly into the Aegean during uppermost Quaternary low sea level stands. Moreover, Xerias River has built the only substantial fan delta, the Loggos fan delta with a maximum 52 m of Holocene sediments (Van Andel and Perissoratis, 2006). Other sources of fresh water include underwater springs, along both the western and eastern coastlines (Scoullos and Dassenakis, 1983; Friligos, 1985).
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. spathulata–B. 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. laevigata–H. 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.
Benthic foraminifer palaeoecology of the Late Quaternary continental outer shelf of a landlocked marine basin in central Aegean Sea, Greece
2012, Quaternary International
North Evoikos Gulf, Greece, constitutes a landlocked, 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 of tracing 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 characterized by certain levels of oxygenation and food availability. Time interval 1 (8513–8300 cal 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 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 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 BP) is related to the high food supply and good bottom circulation.
The 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.
Holocene emergence in Euboea island (Greece)
2012, Marine Geology
Citation Excerpt :
In the northern Euboean Gulf, uplifted Holocene shorelines (Stiros et al., 1992; Pirazzoli et al., 1999a, 1999b) and volcanism (Innocenti et al., 1979) provide evidence of important crustal movements. In addition, the uplift of the fault-bounded NE Euboean coast (Stiros et al., 1992) is related to a > 400 m deep valley in the NE part of this Gulf (Stiros and Pirazzoli, 2006). The present study is based on new field observations in the coastal part of Euboea between Edipsos and Ilia (Fig. 1), and 14 C dating of uplifted lithophagid shells collected in growth position.
Detailed mapping along the northwestern coastline of Euboea has provided new evidence of colonization by Lithophaga lithophaga (L.) reaching about 3.8 m above the present biological MSL. Such marine biological marks, together with morphological notches, correspond to the occurrence of two sequences of Holocene vertical displacements higher than those reported by previous studies, on the central part of the southern coast and along the northern coast of the island. A well developed emerged notch is found at + 1.7 ± 0.1 m above present mean sea level, whereas the uppermost part of the lithophagid holes suggest a former emerged shoreline at least at + 3.8 ± 0.1 m. Radiocarbon AMS dating of Lithophaga shells found in their burrows, showed that the lower uplifted shoreline corresponds to a tectonic event (probably coseismic) apparently dated at 2200 a BP, while the higher shoreline corresponds to an older relative sea-level transgression, possibly of tectonic origin, apparently dated about 5570 a BP. The apparent radiocarbon age of lithophagid shells can be about 350 to 400 years older than the uplift event that exposed them, due to incorporation of host-rock carbon. Nevertheless, the two new paleoshorelines provide evidence that repeated uplift movements, greater than those reported by previous authors, occurred during the late Holocene, uplifting the western part of the island.
Origin and distribution of the terrigenous component of the unconsolidated surface sediment of the Aegean floor: A synthesis
2009, Continental Shelf Research
The Aegean Sea covers an area of some 160×10³ km² and receives the water/sediment fluxes from a mountainous drainage basin of >200×10³ km². On the basis of its morphodynamic characteristics, the Aegean Basin could be divided into: (1) the North Aegean Sea, an elongated region (trending between N50° and N70°) including the extensive northern shelves and the Deep Aegean Trough; (2) the Central Aegean, which includes: the Cyclades Plateau, a relatively shallow (average depth <350 m) submerged platform, surrounded by small basins (up to 1000 m depth), including also the relatively extended eastern shelf of Asia Minor, and (3) the Southern Aegean Sea, located southwards of the Hellenic volcanic arc, which presents the characteristics of a true back-arc basin (the Cretan Sea).
The surficial unconsolidated sediments of the north Aegean floor are dominated by the terrigenous component (from 50% up to >90%) due to the large terrigenous riverine fluxes. The South Aegean presents high percentages (>50%) of biogenic material, due to the small terrigenous inputs and despite the fact that it is more oligotrophic than the North Aegean. The Central Aegean presents a transitional character with the terrigenous influxes being imported along its eastern part and quantitatively being in between those of the North and South Aegean Sea sub-regions.
The coarse-grained materials in shallow (shelf) areas are attributed to ‘relict’ deposits, while those in large water depths are almost exclusively biogenic products. The offshore distribution of the fine-grained terrigenous material is dominated by the overall circulation pattern, while meso-scale eddies may, locally, either enhance (anticyclones) or reduce (cyclones) settling rates. Moreover, the spatial distribution of the predominant clay minerals (illite and smectite) and of kaolinite and chlorite is governed by the lithology and proximity to land source areas, the water circulation and the processes of differential settling and flocculation.
Overall, the North Aegean is characterised by sedimentation processes similar to those of a ‘continental margin’, primarily neritic and secondarily hemipelagic, the Central Aegean region mostly by hemipelagic and the South Aegean, behaving more like an ‘oceanic margin’, mostly by pelagic processes.
Comment to the article "Late Quaternary depositional history of the North Evvoikos Gulf, Aegean Sea, Greece" by Van Andel, T. and Perissoratis, C., Marine Geology, 232, 157-172, 2006
2007, Marine Geology

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Late Quaternary depositional history of the North Evvoikos Gulf, Aegean Sea, Greece

Abstract

Section snippets

Introduction–objectives–regional setting

Materials and methods

Major fault systems and their morphological expressions

Submarine erosional terraces: evidence of previous lake levels

Conclusions

Acknowledgements

Quat. Int.

Earth Planet. Sci. Lett.

Quat. Sci. Rev.

Mar. Geol.

Earth Planet. Sci. Lett.

Tectonophysics

Quat. Res.

Mar. Geol.

Mar. Geol.

Quat. Sci. Rev.

Sediment. Geol.

Quat. Res.

Quat. Res.

Quat. Sci. Rev.

Mar. Geol.

Oceanic topography and morphological regime of Northen Evvoikos Gulf

Seismicity and associated strain of central Greece between 1890 and 1988

Geophys. J. Int.

U–Th ages obtained by mass spectrometry in corals from Barbados: sea level during the past 130,000 years

Nature

Pollen analytical investigations in Thessaly, Greece

Palaeohistoria

Oxygen isotopes and sea level

Nature

Physics of Sound in Marine Sediments

Surficial sediment map of the Aegean sea floor (Pagasitikos Sheet)

The pass at Thermopylae, Greece

J. Field Archaeol.

Variations in the mode of formation and temperature of oceanic deep waters over the past 125,000 years

Nature