GEOLOGICAL SETTING

   The Gulf of Corinth is an active 950m deep graben structure occupying the northernmost part of the Plio-Quaternary Corinth rift (Brooks and Ferentinos 1984; Stefatos at al 2002). (Fig1.1) The present day gulf occupies about 2.400km2 of approximately 4100 km2 that corresponds to the area extent of the Corinth rift.
   The Corinth rift is a topographic depression trending WNW-ESE across the NNW-SSE trending fabric of the Hellenic mountain belt, which includes Mesozoic and Tertiary rocks (Fig 1.1)
   The Corinth rift was formed around middle Pliocene due to a N-S/NNE-SSW directed extension caused by: (i) the westward motion of the Anatolian Plate (Taymaz at al 1991; Le Pichon at al 1995) or (ii) the arc-normal pull acting on the Aegean plate margin (Hatzfeld at al 1997) or (iii) a combination of both mechanics (Doutsos & Kokkalas 2001).
   A series of en-echelon normal fault segments bound the rift along the southern border. These fault segments with lengths between 15 and 25km have an average strike of WNW-ESE direction and a northward dip (Doutsos & Poulimenos 1992; Sorel 2000) (Fig 1.1)
   They are listric faults forming a low angle detachment zone dipping at about 15o that cuts obliquely to the north through the nappe pile of the Hellenides (Fig 1.2) (Doutsos & Poulimenos 1992; Sorel 2000)
   These faults were active in the early rifting stage, then steeper faults formed successively northwards, as the southern part of the detachment became inactive. The younger faults have steeper plannes dipping northwards between 40o and 60o and reach depths of about 10 to 12km where they root the low angle detachment zone (Sorel 2000). (Fig 1.2)
   The entire southern part of the Corinth rift, a 25km wide zone south of the Gulf of Corinth, has been uplifted since the early Pleistocene. (Fig 1.1) The uplift may be related either to underplating of sediments in the Hellenic Trench (Le Pichon & Angelier 1981 Hatzfeld et al 1989) or to footwall uplift adjacent to a major normal fault (Jackson at al 1982 a, b) or both.
   The older rift fill is middle to late Pliocene lacustrine and fluvial sand silts. These are overlain by thick Quaternary conglomerates which have prograded northward forming Gilbert-type fan-deltas and are interbedded with marls which contain nannofossil assemblages corresponding to middle Pleistocene isotopic stage 12 or younger, that is younger, than 450 ka. (Doutsos et al 1988; Doutsos and Piper 1990).
   The marls are overlain either unconformably or conformably, by shallow marine or fluvial sandstones and or conglomerates with a thickness less than 30m, forming a “caprock” (Keraudren and Sorel 1987).
   The uplift has interacted with sea-level changes to produce α staircase morphology in the landscape defined by flat terraces climbing southwards (Keraudren and Sorel 1987; Doutsos and Piper 1990; Collier 1990 and Armijo at al 1996), (McNeill and Collier 2004, 2006) (McNeill and Collier 2004, McNeill et al 2006) (Fig.1.1).

  Fig. 1.1: Geological Map of Corinth Gulf.

 

Fig.1.2: North-south section along Krathis River(location in Fig. 1). 1: Lower to early- middle Pleistocene fan breccia. (Qbr:=Quaternary breccians) 2: Early Pleistocene to Holocene synrift deposits. 3: Pindos-Olonos napple (P/O): more than 500m of Senonian limestones. 4: Gavroro-Tripolitsanapple (G/T): as much as 1500m nonmetamorphic Mesozoic carbonates 5: Zarouchla Group: mainly epimetamorphic schists. 6: Stratigraphic contact 7:Alpine thrusts or locked normal faults. 8:Locked Khelmos detachment 9: Active Helike fault, propably connected to seismic detachment beneath gulf. 10: Dashed line is profile of Krathis River.

 

 

References:

Armijo R., Meyer B., King G., Rigo A. and Papanastasiou D. (1996) Quaternary evolution of the Corinth Rift and its implications for the Late Cenozoic evolution of the Aegean. Geophysical Journal Intern. 126: 11-53

Brooks M and Ferentinos G. 1984. Tectonics and sedimentation in the Gulf of Corinth and the Zakinthos and Kefallinia Channels, Western Greece. Tectonophysics 101:25-54

Collier R., 1990, Eustatic and tectonic controls upon Quaternary coastal sedimentation in the Corinth Basin, Greece J. of Geol. Soc. London 147:301-314

Doutsos T., and Piper D., 1990. Listric faulting, sedimentation and morphological evolution of the Quaternary eastern Corinth rift, Greece: First stages of continental Rifting. Geol. Society of America Bull. 102:81-89

Doutsos T., and Poulimenos G., 1992. Geometry and kinematics of active faults and their seismotectonic sigmificance in the western Corinth – Patras Rift (Greece).

J. Structural Geology 14: 689-699.

Doutsos T. and Kokalas S. 2001. Stress and deformation patterns in the Aegean region.  J. of Structural Geology. 23: 455-472.

Doutsos T., Kontopoulos N. and Poulimenos G. 1988.  The Corinth –Patras Rift as the initial stage of continental fragmentation behind an island arc (Greece). Basin Research 1:177-180.

Hatzfeld D., Pedotti G., Hatzidimitriou R.. et al 1989. The Hellenic subduction beneath the Peloponnesus: first results of a microearthquake study. Earth Planetary Science Letters.  93:283-291.

Hatzfeld D., Martinod J., Bastet G., and Gautier P., 1997. An analogue experiment for the Aegean to describe the contribution of gravitational potential energy. J. of Geophysical Research. 102: 649-659

Jackson J., King G., and Vita-Finzi C., 1982. The Neotectonics of the Aegean: an alternative view. Earth Planetary Science Letters 61:301-318

Jackson J., Gagnepain J., Houseman G., King G., Papadimitriou P., Soufleris C., and Virieux J. 1982. Seismicity, normal faulting and the geomorphological development of the Gulf of Corinth. Earth Planetary Science Letters 57:377-397

Jackson J., Haines J. and Holt W., 1994. A Comparison of satellite laser ranging and seismicity data in the Aegean region. Geophys. Res. Lett. 21: 2849-2852.

Keraudren B., and Sorel D. 1987. The Terraces of Corinth (Greece). A detailed record of eustatic sea level variations during the last 500.000 years. Marine Geology 77:99-107

Le Pichon X. and Angelier J. 1981. The Aegean Sea. Philos. Trans. R. Sor. London. Ser. A300: 357-372

Le Pichon X., Chamot-Rooke N., Lallemant S., Noomen R., and Veis G. 1995. Geodetic determination of the kinematics of central Greece with respect to Europe. Implications for Eastern Mediterranean tectonics, J. of Geophysical Research 100:12675-12690.

McNeill L., and Collier R. (2004). Uplift and slip rates of the eastern Helike fault segment, Gulf of Corinth, Greece, inferred from Holocene and Pleistocene terraces. Journal of Geological Society of London. 161:81-92

McNeill L., Collier R., Pantosti D., De Martini P., and D’Addezio C. 2006. Recent history of the eastern Helike Fault: Geomorphology, Palaeoseismology and Impact on Palaeoenviroment in Ancient Helike and Aegialeia – Archaeological Sites in Geologically Active Regions (eds D. Katsonopoulou S., Soter and I. Koukouvelas) Helike III, Athens 2005

Sorel D., 2000. A Pleistocene and still active detachment fault and the origin of the Corinth – Patras rift, Greece. Geology. 28:83-86.

Stefatos A., Papatheodorou G., Ferentinos G. Leeder M and Collier R. 2002. Seismic reflection imaging of active offshore faults in the Gulf of Corinth: their seismotectonic significance. Basin Research 14:487-502

Taymaz T., Jackson J., and McKenzie D., 1991. Active tectonic of the north and central Aegean Sea. Geophysical Journal Intern. 106:433-49

 

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