The Gulf of Corinth: an active half graben?

doi:10.1016/S0264-3707(03)00053-X

Journal of Geodynamics

Volume 36, Issues 1–2, August–September 2003, Pages 323-340

https://doi.org/10.1016/S0264-3707(03)00053-X Get rights and content

Abstract

The Gulf of Corinth is often considered as a typical example of a more or less simple half graben with major border faults to the south and a flexure of the northern shore. This paper reviews new data, especially subsurface data, from both onshore and offshore, compiled or acquired through the Corinth Rift Laboratory EEC project. This data indicate that (1) the Gulf of Corinth is bordered both north and south by active faults; (2) there is a lot of them, and not only the one bordering the Peloponnese coastline are still active; and (3) distinct opening phases may be recognized on the area. During the first phase, the depocenter was located near the northern shore, whereas during the most recent phase, and only in the centre and the eastern sector, the depocenter moved towards the southern shore. Furthermore, active tectonic, in this western sector, is characterised by a general uplift of the Peloponnese that leads to the formation of new faults, i.e. the Doumena, Aigion and Helike faults and to selective reactivation of older ones such as the Pirgaki fault. We suggest that this current tectonic phase started about 150–120 000 years ago in the Aigion area and about 350 000 years ago eastward (Corinth-city) and that it represents a third opening phase during the growth of the Gulf of Corinth.

Introduction

The Gulf of Corinth area (Fig. 1) has been studied for a long time, since its southern shore exposes spectacular outcrops and because it is the most seismically active zone of the European Union. However, until recently, subsurface data, from both offshore and onshore, were not available. Consequently, because synrift deposits crop out only along the southern shore of the Gulf, the models about the extensional processes in the area were build up on a small amount of data. Subsurface data have been collected offshore by Hellenic Petroleum, the National Centre of Marine Research (NCMR) and the Patras University, and more recently onshore by the cluster of European projects called “CRL” (Corinth Rift Laboratory, Moretti et al., 2002). This new data have lead to a better-constrained structural model of the Gulf that will be discussed in the following section. Through the CRL project, extensive field works have also been carried out around the Aigion area, together with detailed analyses of cuttings and cores collected on land as well as offshore. The CRL also has set-up the installation of few networks (seismic, GPS, strain meters, geochemical…) which have allowed the monitoring of the area and the recollection of a large mass of information. Our work suggests that the Gulf of Corinth is the result of a longer and more complex deformation history than the simple half graben, bordered southward by an unique active fault, often described in the literature.

Section snippets

Geological setting

Extension in the Aegean Sea started in Miocene times (Le Pinchon & Angelier, 1979, Jolivet et al., 1994, Armijo et al., 1996). This extension is thought to be due to both gravitational collapse of the thick crust inherited from earlier mountain building (Jolivet, 2001) and lithospheric thinning in the Aegean back arc region (Doutsos et al., 1988). The extension rate is fast, about 3 cm/year, with respect to Eurasia (Kahle et al., 2000, Jolivet, 2001) and progressively migrates to the south.

Fault activity

The faults exposed along the southern shore of the Gulf often dissect the synrift sediments and therefore have been often described (Doutsos & Poulimenos, 1992, Roberts et al., 1993 and many others). However, faults are numerous on both sides of the Gulf and available data show that some of the south dipping faults located on (or near) the northern shore are still active.

The activity of the Delphi fault (Fig. 3d), for example, has been recorded for more than 3000 year by repetitive destructions

Kinematics of the Gulf opening

Ori (1989) divides the Gulf of Corinth's evolution into two main phases. During the first phase the proto-Gulf of Corinth was filled with continental and shallow-water deposits. During the second phase, the Gulf of Corinth acquired its current orientation and sedimentation was characterised by the deposition of Gilbert-type deltas along the southern shore and by turbidites within the Gulf itself. Ori (1989) suggested that the first phase could be rather “old” and related to the Aegean Sea

Block tilting in the Gulf of Corinth

Tilted blocks usually exist in rifts, and have been described worldwide on seismic lines as well as in the field. Often the blocks are at the scale of the upper crust, as in the Gulf of Suez (Moretti and Colletta, 1988), and the tilt process is due to the rotation of rigid blocks. In the case of domino on planar faults, extension does not imply any absolute uplift of the crest of the blocks (Angelier and Colletta, 1983). In the case of listric faults, the crest may be effectively uplifted by

Uplift

As there is no evidence of block tilting, the uplift of the area cannot be caused by the rotation or by elastic rebound of a tilted block. On the eastern part of the Gulf, Armijo et al. (1996) interpret the uplift of marine terraces, outcropping between Corinth and Xylocastro, as the elastic rebound of the footwall of a major fault. They reached the conclusion that the required synrift sediment thickness for such an uplift (800 m in 350 000 years) was in the range of 10 km and the elastic

Conclusions

The data summarized here allow us to confute some of the previous simple models which have been proposed for the evolution of the Gulf of Corinth. In particular it has been assessed that:

1.
The Gulf of Corinth is not an asymmetric simple half graben. There are active normal faults on both sides of the Gulf and the depocenters depend on the place northward, at the center or southward. The maximum water depth is measured almost everywhere in the central sector of the basin.
2.
There is no evidence of

Acknowledgments

This study has been founded by the EEC (Vth PCRD) through the projects 3F-Corinth (ENK6-CT-2000-00056) and DG-Lab (EVR1-CT-2000-40005), G. Ollier and J. Schuppers being the scientific advisers. We are very grateful to F. Ghisetti, L. Vezzani and R. Sibson who mapped the Aigion area. We also thank D. Sorel, T. Doutsos and I. Koukouvelas who spent some of their time with us in the field, and G. Ferentinos and A. Stefanos for stimulating discussions and for access to their onshore seismic data.

References (68)

M. Brooks et al.
Tectonics and sedimentation in the gulf of Corinth and the Zakynos and Kefallinia channels, western Greece
Tectonophysics
(1984)
C. Dart et al.
Sequence stratigraphy of (?) Pliocene–quaternary synrift, Gilbert-type fan deltas, northern Peloponnesos, Greece
Marine and petroleum Geology
(1994)
T. Doutsos et al.
Geometry and kinematics of active faults and their seismotectonic significance in the western Corinth-Patras rift (Greece)
J. Struct. Geol.
(1992)
J. Jackson et al.
Seismicity, normal faulting, and geomorphological development of the Gulf of Corinth (Greece)the Corinth earthquake of february and march 1981
Earth and Planetary Science Letters
(1982)
L. Jolivet
A comparison of geodetic and finite strain pattern in the Aegean, geodynamic implications
Earth and Planetary science letters
(2001)
B. Keraudren et al.
The terraces of Corinth [Greece]—a detailed record of eustatic sea-level variations during the last 500,000 years
Marine Geol.
(1987)
F. Lemeille et al.
Quantification de la déformation associée à la faille d'Aigion (Golfe de Corinthe, Grèce) par l'étude des dépôts du Pleistocène supèrieur et de la transgression marine holocène
CRAS
(2002)
J. Makris et al.
Thinned continental crust below northern Evoikos Gulf, central Greece, detected from deep seismic soundings
Tectonophysics
(2001)
I. Moretti et al.
Fault-block tiltingthe Gebel Zeit example, Gulf of Suez
J. of Struct. Geology
(1988)
I. Moretti et al.
How does a block tilt?
Tectonophysic
(1988)

C. Perissoratis et al.

Alternating marine and lacustrine sedimentation during late Quaternary in the Gulf of Corinth rift basin, central Greece

Mar. Geol.

(2000)

N. White et al.

The relationship between the geometry of normal faults and that of sedimentary layers in the hanging walls

J. Structural. Geology

(1986)

J. Angelier et al.

Tension fractures and extensional tectonics

Nature

(1983)

R. Armijo et al.

Quaternary evolution of the Corinth Rift and its implications for the Late Cenozoic evolution of the Aegean

Geophys. J. Int.

(1996)

P. Bernard et al.

The Ms=6.2, June 15, [1995] Aigion earthquake (Greece): evidence for low angle normal faulting in the Corinth rift

J. Seismol.

(1997)

H. Billiris et al.

Geodetic determination of tectonic deformation in Central Greece from 1900 to 1988

Nature

(1991)

P. Briole et al.

Active deformation, of the gulf of Korinthos, Greece: results from repeated GPS surveys between 1990 and 1995

JGR

(2000)

Causse, C., Plagnes, V., Moretti, I., Ghisetti, F., 2001. Direct Dating (U-Th) of Fault Cements from the Corinth Rift...

Causse, C., Moretti, I., Ghisetti, F., Eschard, R., Micarelli, L., Ghaleb, B., Frank, N. Kinematics of the Corinth Gulf...

Clément, C., 2000. Imagerie sismique crustale de la subduction hellénnique et du golfe de Corinthe. Thèse de doctorat,...

R.E. Collier et al.

Rates of uplift in the Corinth and Megara basins, central Greece

Tectonics

(1992)

R.E. Collier et al.

High sediement yields and cool, wet wintersrest of past glacial paleoclimates in the northern Mediterranean

Geology

(2000)

R.R. Davies et al.

Geodetic strain of Greece in the interval 1892–1992

J. Geophys. Res.

(1997)

D. Dinter

Late Cenozoic extension of the Alpine collisional orogen, northeastern Greeceorigin of the north Aegean basin

GSA Bulletin

(1998)

T. Doutsos et al.

The Corinth-Patras rift as the initial stage of the continental fragmentation behind an active island arc [Greece]

Basin Research

(1988)

J.L. Faure et al.

Deformation of tilted blocks, consequences on block geometry and extension measurements

Bull. Soc. Geol. France

(1989)

N. Flotté et al.

Attemps to date Pleistocene normal faults of the Corinth-Patras Rift (Greece) by U/Th method and tectonic implication

Geophysical resaerch metters

(2001)

Flotté, N., Sorel, D. 2001. Structural cross section through the Corinth-patras detachement fault-system in the...

Ghisetti, F.C., Vezzani, L., Agosta, F., Sibson, R., Moretti, I., 2001. Tectonic setting and sedimentary evolution of...

Ghorbal, B., 2002. Quels arguments en faveur d'un détachement plio-quaternaire au sud du Golfe de Corinthe? DEA thesis,...

L. Jolivet et al.

3D kinematics of extension in the Aegean region from the early Miocene to the present, insights from the ductile crust

Bul. Soc. Geol. France

(1994)

H. Kahle et al.

GPS-derived strain rate field within the boundary zones of Eurasian, African, and Arabian Plates

JGR, v 105

(2000)

X. Le Pichon et al.

The Hellenic arc and trench systema key to the neotectonic evolution of the eastern Mediterranean area

Tectonophysics

(1979)

LePourhiet, L., Burov, E., Moretti, I. How the initial crustal thickness variations control the extension in a back arc...

Cited by (142)

Late Quaternary deformation in the western extension of the North Anatolian Fault (North Evia, Greece): Insights from very high-resolution seismic data (WATER surveys)
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.
Harbour geoarchaeology of Lechaion (Corinth area, Greece) sheds new light on economics during the Late Bronze Age/Early Iron Age transition
2023, Marine Geology
Lechaion in Corinth, Greece, is the largest ancient port in Greece. Harbour geoarchaeological investigations, based on ¹⁴C-dated palaeoenvironmental archives taken from a well-studied inner basin (Basin 3) and a still unknown outer basin (Basin 4), revealed anthropogenic lead excesses starting from the 12th century BCE, associated with brown coal fragments, for the first time discovered in such an ancient archaeological context. Given that historical sources trace the foundation of the port back to the 7th century BCE, these results attest to protohistoric industrial use of the site and push back its chronology by over five centuries. The existence of such ancient port activity not only extends the chronological horizon for harbour activity in the Corinthian area, but also provides new insights for the Late Bronze Age/Early Iron Age (LBA/EIA) transition, including potential trading routes that may have transited through Lechaion, likely spanning across the Gulf of Corinth and possibly even beyond, to western Mediterranean urban centers.
The 2020–2021 seismic sequence in the Western Gulf of Corinth: Insights on the triggering mechanisms through high resolution seismological and geodetic data analysis
2023, Tectonophysics
The 2020–2021 seismic sequence at the Western Gulf of Corinth, Central Greece, has been thoroughly analyzed using seismological and geodetic data processing. We present a high-resolution dataset of over 4000 relocated earthquakes between June 2020 and February 2021, delineating the activated structures. We examine the evolution of various clusters that were triggered during a three-stage sequence which began on December 23, 2020, with an M_w = 4.6 event near Marathias, migrated eastwards, following an M_w = 5.0 event on January 12, 2021 near Trizonia Island, and culminated on February 17 with an M_w = 5.3 offshore event north of Psathopyrgos. Focal mechanisms for the 20 stronger events, determined by moment tensor inversion, and 36 weaker ones, obtained through first motion polarities measurements, revealed dominant normal faulting. The fault plane of the February 17, 2021 major event is modeled through the inversion of geodetic data. Results suggest a very shallow geodetic centroid at 1.5 km depth, consistent with the seismic centroid (3.5 km), but different from the relocated hypocenter (7.5 km). Spatiotemporal analysis reveals seismic migration, following a diffusion law with D values in the range 0.06–0.25 m²s⁻¹, consistent with triggering due to pore-pressure diffusion by fluids intrusion. This enables failure on non-optimally oriented faults, which explains the significant proportion of the observed strike-slip and oblique-normal faulting. Coulomb stress transfer due to the major events shows only weak stress-loading on the fault of the January 12, 2021 earthquake and a higher level of positive stress transfer to the south-dipping than to the north-dipping nodal plane of the 17 February event. The latter could have facilitated the nucleation of the rupture at 7.5 km and its further propagation to shallower depths along a south-dipping plane, where the bulk of its seismic and geodetic moment was released.
Hydrodynamics and sedimentary processes in the modern Rion strait (Greece): Interplay between tidal currents and internal tides
2022, Marine Geology
Straits are crossed by marine currents that are amplified due to constrictions. These nearshore high-velocity flows are problematic for offshore infrastructures (bridge pillars, cables, pipelines, etc), but constitute an interesting carbon-free energy source. Many modern straits are dominated by tidal currents which flow axially, with reversal directions and phase difference between the two interlinked basins. These tidal currents interplay with: sediment sources (including in situ carbonate production and deltas), tectonic activity, and inherited lowstand features, all shaping the seafloor into complex geomorphologies. Previous studies have highlighted a common tidal strait depositional model with a strait-center zone in erosion and on each side a dune-bedded strait zone with 3D and 2D tidal dunes and tidal ripples. Even if the internal waves associated with and generated by the straits are widely documented, the effects of the internal waves on the seafloor need to be further investigated. The aim of this study is to unravel the combined effects of the tidal currents and the internal tides on current pattern and on the morphosedimentary features.
We present a strait example based on an interdisciplinary approach using high-resolution geophysical and oceanographical data to better constrain the hydrodynamics and the processes acting on the seafloor. We focus on the Rion Strait in Greece which controls the connection between the Corinth Gulf and the Mediterranean Sea. Based on high-resolution multibeam bathymetry (MBES) over an area of 211 km², we identify and quantify different morphologies by extracting bathymetric swath profiles. These results are integrated with currents data (ADCP) and CTD profiles. In addition, we use high-resolution chirp sub-bottom profiles and sparker seismic reflection profiles to document the morphology and internal architectures of the sedimentary deposits and the erosional features in the strait bottom. To complete this dataset, we analyzed Sea Surface Temperatures (SST) from satellite sensors.
The Rion Strait displays complex bathymetric features without tidal dunes. At the excepted depositional location of tidal dunes, we identify an erosive area with a pool and crest morphology. This new example completes the tidal strait depositional model by a re-localization of erosion, bypass and deposition in an asymmetric strait swept by baroclinic currents. This example illustrates the key role of internal tides in straits located between a confined deep basin and an open sea.
Palaeoenvionmental inferences on the Pleistocene deposits of the Charadros River (Rio graben, Western Corinth Gulf, Greece)
2021, Quaternary International
Citation Excerpt :
A common characteristic between active grabens is that the current deformation is accommodated into first and second order faults as happens in Afar Graben (Illsley- Kemp et al., 2018). This is also noticed in areas located at the flanks of the Corinth Graben (Zelilidis et al., 1988; Doutsos and Piper 1990; Moretti et al., 2003; Ford et al., 2013; Zygouri et al., 2008; Taylor et al., 2011). In our study area, first order faults define kilometer wide blocks with significant offset.
Rio graben is a region of significant stratigraphic and palaeontological interest where several environmental changes have been recorded during the Quaternary. These changes are a result of active tectonism, related to the well-known rifting process that has been occurring in the geotectonic region of the Corinth-Patras Rift, as well as of the influence of continuous eustatic and climatic changes. Fossil assemblages from Middle to Upper Pleistocene transitional to marine and terrestrial sedimentary sequences located at Sichaena (Rio Graben) on the west side of Charadros river in NW Peloponnesus, Greece, are analyzed herein in order to distinguish tectonic and eustatic controls.
The name of the studied section is Vigla 1 (50 m thickness), belonging to the NE-trending Rio graben, a structure bridging the Corinth graben to the east and the Patras graben to the west. The presence of two normal antithetic second order faults and an unconformity were identified separating the studied stratigraphic section into four distinct sedimentological sequences. The purpose of this work is to determine the palaeoenvironmental conditions of the studied section and to unravel the Middle-Late Pleistocene palaeoenvironmental changes. The micro-fauna evidences oligohaline lagoon sediments at the lower sequence (Sequence 1). Conversely, at the middle (Sequence 2) and at the upper sequence (Sequence 3), the recorded species indicate lagoonal to shallow marine depositional environments. At the top of the section, an unconformity brings into contact Sequence 3 with a sequence consisting a red conglomerate (Sequence 4) that indicates an alluvial fan environment. In order to constrain chronologically the sediments Optically Stimulated Luminescence (OSL) dating was applied. According to the OSL dating results, an Upper Middle Pleistocene age has been attributed for the studied sequences. Moreover, projecting the dating results to the marine isotope curve, a high degree of consistency can be seen between the OSL ages and MIS 7e, 7c and 6d, where the transition from lagoonal facies to shallow marine alternations in sequence 2 correlates well with the MIS 7c highstand, and sequence 3 with MIS 7e and the MIS 6d low stand. Thus, our results indicate the spatial palaeoenvironmental evolution of the studied area which during the Upper Middle Pleistocene is characterised by intense local tectonic movements in conjunction with eustatic sea level changes.
The Kefalonia Transform Fault: A STEP fault in the making
2020, Tectonophysics
Vertical edges along subducted slabs have been recognized in the majority of subduction zones. Surprisingly, slab edges evolved into Subduction-Transform-Edge-Propagator (STEP) faults in only a few regions; the conditions under which STEPs form are special. It is relevant to constrain the conditions that facilitate STEP fault initiation because they leave a clear geological footprint in the overriding plate, whereas vertical tears generally do not. We therefore study a candidate region for STEP fault initiation in the western Hellenic Subduction Zone.
We investigate the structure and seismicity of the shallow western Hellenic Subduction Zone using a recent full-waveform inversion model which both captures details of crustal and upper-mantle structure, yielding constraints in the depth interval from 10 to 200 km where lithosphere-mantle interactions have tectonic expressions. The western end of the Hellenic Subduction Zone is fragmented near the Kefalonia Transform Fault. We identify a separate Epirus lithospheric fragment that is roughly vertical below the southern Albanides. We also identify a new and major contrast within the lithospheric mantle of the Ionian ocean basin, which aligns with a gradient in free-air anomalies.
In the overriding plate, the Kefalonia Transform Fault zone accommodates right lateral strike-slip deformation. We interpret this fault zone as a proto-STEP fault that formed simultaneously with Pliocene fragmentation of the Epirus fragment.
Comparing the recent evolution of the NW Hellenic slab edge with currently active STEPs indicates that along-trench variations in convergence velocity are a prerequisite for STEP fault initiation. Such velocity variations may result from subduction of continental crust along part of the trench. Resistance to sea ward tear propagation by a mechanically strong subducting plate may prevent variations in convergence velocity to occur, and thus STEP fault initiation. The amount of time over which a velocity contrast persists will also be relevant for STEP fault initiation. Mechanical coupling between upper- and lower-plate, and the deformability of the upper-plate appear to also play a role in the initiation of the STEP fault once a slab is fragmented.

View all citing articles on Scopus

View full text

The Gulf of Corinth: an active half graben?

Abstract

Introduction

Section snippets

Geological setting

Fault activity

Kinematics of the Gulf opening

Block tilting in the Gulf of Corinth

Uplift

Conclusions

Acknowledgments

Tectonophysics

Marine and petroleum Geology

J. Struct. Geol.

Earth and Planetary Science Letters

Earth and Planetary science letters

Marine Geol.

CRAS

Tectonophysics

J. of Struct. Geology

Tectonophysic

Mar. Geol.

J. Structural. Geology

Tension fractures and extensional tectonics

Nature

Quaternary evolution of the Corinth Rift and its implications for the Late Cenozoic evolution of the Aegean

Geophys. J. Int.

The Ms=6.2, June 15, [1995] Aigion earthquake (Greece): evidence for low angle normal faulting in the Corinth rift

J. Seismol.

Geodetic determination of tectonic deformation in Central Greece from 1900 to 1988

Nature

Active deformation, of the gulf of Korinthos, Greece: results from repeated GPS surveys between 1990 and 1995

JGR

Rates of uplift in the Corinth and Megara basins, central Greece

Tectonics

High sediement yields and cool, wet wintersrest of past glacial paleoclimates in the northern Mediterranean

Geology

Geodetic strain of Greece in the interval 1892–1992

J. Geophys. Res.

Late Cenozoic extension of the Alpine collisional orogen, northeastern Greeceorigin of the north Aegean basin

GSA Bulletin

The Corinth-Patras rift as the initial stage of the continental fragmentation behind an active island arc [Greece]

Basin Research

Deformation of tilted blocks, consequences on block geometry and extension measurements

Bull. Soc. Geol. France

Attemps to date Pleistocene normal faults of the Corinth-Patras Rift (Greece) by U/Th method and tectonic implication

Geophysical resaerch metters

3D kinematics of extension in the Aegean region from the early Miocene to the present, insights from the ductile crust

Bul. Soc. Geol. France

GPS-derived strain rate field within the boundary zones of Eurasian, African, and Arabian Plates

JGR, v 105

The Hellenic arc and trench systema key to the neotectonic evolution of the eastern Mediterranean area

Tectonophysics