Tectonically active landscapes, drainage and coastal evolution in Phthiotis, central-eastern mainland Greece

H. Kranis, K. Vouvalidis, A. Chatzipetros, S. Pavlides, G. Syrides, K. Albanakis, S. Pechlivanidou, and P. Tsourlos

Pthiotis is an area where the interplay between active tectonics, sedimentation and sea-level change has been shaping the landscape: range-front marginal faults control on- and offshore basins, such as the Sperchios Graben and the North Gulf of Evia (NGE), while significant events and cultural activities in historical times are linked to the evolution of the Sperchios River delta. However, the only onshore fault that has been affirmatively connected with strong earthquakes in the historical times, is the Atalanti Fault, which ruptured at 20 and 17 April 1894, producing two of the most destructive earthquakes in the recent history of Greece.

The western part of southern coast of the NGE is controlled by the Lokris Coastal Fault System (LCFS), which comprises three faults, the Arkitsa, the Agios Konstantinos and Kamena Vourla Faults. The Arkitsa fault segment has an impressive fault surface (slickenside), which features a plethora of perfectly preserved kinematic indicators, such as milimetric scratches to cm-scale tool and plod marks, corrugations, tension gashes, debris trails, etc. All slip features are consistent with oblique-normal slip; due to this, the fault surface displays alternations of polished and “dull” bands, parallel to the mean slip vector.

The Sperchios Fault System (SFS) controls the southern margin of the namesake Graben and has a total length that exceeds 80 km. It consists of two major fault segments, the Kompotades and the Spercheias Faults. The former is associated with a footwall relief that exceeds 2 km, and a total throw up to 3 km. Recent research suggested that the SFS, together with the LCFS further to the east, correspond to an undelapping crustal fault zone which accommodates the differential movement between the North Aegean Fault in the east and the Kefallonia Fault in the west, on the western termination of the Hellenic Arc.

The coasts of the Maliakos and the North Evia Gulfs have undergone considerable modification in the Upper Quaternary, owing to the combination of tectonic activity, sea level fluctuation and evolution of the Sperchios river delta. The historical Thermopylae Pass, locus of one of the most significant battles in the classical antiquity, was a few tens of m narrow landstrip between the foot of Mt Kallidromo and the Maliakos Gulf. Nowadays, this area is a 5 km-wide coastal plain. Near-surface geophysics, coring and archaeological investigations document the evolution of the prograding Sperchios River delta, which takes place in a tectonically active area: tectonic uplift has been held responsible for the maintenance of Neolithic coastal settlements above sea-level, despite the Holocene sea-level rise.

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