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The uplifted southern shoulder of the Corinth rift is characterized by step-like topography. This step-like topography is more prominent in the western part between Egio and Akrata and in the eastern part between Xylocastro and Corinth. (Fig 1.1)
The marine terraces in the western part were examined in detail by McNeil and Collier 2004 and McNeil et al 2006. A max. of 8 to 9 terraces were identified with the oldest one reaching a max elevation of 520m. (Fig 4.1) These terraces are on the footwall of the Helike fault (Fig. 4.1) and are of late Pleistocene to Holocene in age. These terraces correspond to sea-level highstands and were formed by wave erosion, marine deposition or delta progradation. The sequence of terraces matches well eustatic sea-level highstands. There is a reasonable correlation on fitting terrace elevation to the sea level curve as compiled by Chappell et al 1996. (Fig 4.2) The uplift rate for the Helike fault for the last 300.000 years is estimated to be between 1 and 1.5 mm/year.
The marine terraces in the eastern part were examined by Deperet (1913), Vita-Fintzi & King (1985), Keraudren and Sorel (1987), Doutsos and Piper (1990) and Armijo et al (1996). A max. of 11 terraces were identified with the oldest reaching a max. elevation more than 1000m. (Fig. 4.3)
Deperet (1913) attributed this step topography to a single faulted Tyrrhenian terrace. Similarly Vita-Finzi & King (1985) and Doutsos & Piper (1990) accepted that some of the steps correspond to sea-level high stands but interpreted most of the steps as a single faulted surface. Keraudren and Sorel (1987) and Armijo at al 1996 interpreted all the steps as marine terraces. Each terrace comprises a “caprock” generally 2 to 6m thick formed from well-cemented sand and conglomerate. The caprock corresponds to cycles starting with marine transgression, generally with angular unconformity over the underlain marls, followed by regression.
Palaeontological and radiometric dating has shown that the oldest terrace is dated at 450.000ka (OIS – 11.3) and that the number of terraces is close to the number of oxygen isotope stages of high sea-level stands (Keraudren & Sorel 1987). This allows a correlation between the altitude of the terraces and the time (age) of their formation. (Fig. 4.4)
This correlation shows that the average uplift rate for the last 450.000years is 1.5 mm/yr and that with time there is a decrease in the uplift (Keraudren & Sorel 1987).
Armijo et al (1996) associated the uplifting of the terraces to the uplift of the footwall of the offshore Xylocastro fault and estimated that for the last 450.000years the uplift rate is 1.3 to 1.6 mm/year.
In addition to the marine terraces observed in the uplifted southern shoulder of the Corinth rift, by Keraudren & Sorel, transgressive cycles, which were observed in the Corinth canal by Collier 1990, Collier et al 1992 attest to this area having been uplifted. Each transgressive cycle is bounded by an unconformity surface and comprises beach to shore face facies. The dates of the transgressive cycles measured with U/Th techniques are well correlated with interglacials of isotope stages 5.7 and 9 of the marine record. This correlation shows that the average uplift of the Corinth canal area has been 0.3 mm/yr for the last 205.000 years.
Fig.4.1: Eastern Helike Fault system including stepover regions with the Western Helike Fault to the west and Derveni Fault to the east. Fault trace determined from cumulative scarps and geomorphology. Marine terraces uplifted in the footwall block and mapped in this study are shown, with both inner and outer edges marked. Profiles A-F across the uplifted terraces are correlated against the sea-level curve. Holocene terraces (beach and fluvial) and the positions of dated coral samples and uplifted limestone notches are also indicated. Positions of trenches EET1 and ET1A are indicated by black boxes. Borehole EEB is located at the northern end of EET1A. (From McNeill et al 2006)
Fig. 4.2: Best-fit correlations between terrace sequences and eustatic sea level curve for Profiles A,BE and F. Preferred uplift rastes of 1.1+-0.1 and 1.5 +- 0.1 mm/yr are shown. Uplift of 1.1mm/yr (0.9mm/yr at the eastern tip) agrees with dated material and correlation of two prominent terrace sequences with OIS 5 and 7. Sea level curve derived from Chappell et al. (1996)
Fig. 4.3: Morphostratigraphic map of the main terraces in the Corinth area. Name of the terraces: 11.3=Veliniatika (A2); 9.3=Fortikia (east of Solomos river)=Nicoletto (A2)=Megali Lakka (B); 7.5=Tempel (A1,A2,B,C); 7.3=Ancient Corinth (A1,A2,B,C); 7.1=Tripos (A1,A2,B,C); 5.5=New Corinth(A1,B,C); Kounoukles (C); 5.1=Agios Spiridon (A1,C). From Keraudren and Sorel 1987)
Fig. 4.4: Altitude versus age curves obtained by correlation of the marine terraces (on the land sections A1, A2, B and C of Fig. 4.3) with the low δ 18 Ο (high sea level) peaks of the oceanic oxygen-isotope curve (below). The isotopic curve is that given by Imbrie et al. (1984). (From Keraudren and Sorel 1987).
Armijo R., Meyer B., King G., Rigo A., and Papanastasiou D. 1996. Quaternary evolution of the Corinth Rift and its implication for the Late Cenozoic. Evolution of the Aegean. Geophysical J. Intern. 126:11-53.
Chappell J., Omura A., Esat. T., McCulloch M., Pandolfi J., Ota Y., Pillans B., 1996. Reconciliation of late Quaternary sea levels derived from coral terraces at Huon Peninsula with deep oxygenisotope records. Earth Planetary Science Letters 141: 227-236
Collier R., 1990. Eustatic and tectonic controls upon Quaternary coastal sedimentation in the Corinth Basin, Greece. J. of the Geological Society, London. 147:301-314.
Collier R., Leeder M., Rowe P. and Atkinson T. 1992. Rates of tectonic uplift in the Corinth and Megara basins, central Greece. Tectonics 11: 1159-1167
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. 102:812-829.
Keraudren and Sorel 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.
McNeill L. & Collier R. 2004. Uplift and slip rates of the eastern Helike fault segment, Gulf of Corinth Greece, inferred from Holocene and Pleistocene Terraces. J. of the Geological Society of London 161:81-92.
McNeill L. & Collier R., Pantosti D., De Martini P., D’ Addezio G., 2006. Recent History of the Eastern Helike Fault: Geomorphology, Paleoseismology and impact on Paleoenvironments. Ancient Helike and Aigialeia: Archaeological Sites in Geological Active Regions (Eds D. Katsanopoulos, S. Soter and I. Koukouvelas). Proceedings of the 3rd Intern. Conference on Helike III pp 243-265.
Vita- Finzi G. & King G. 1985. The seismicity geomorphology and structural evolution of the Corinth area of Greece. Phil. Trans. R. Soc. London. 314:379-407.