Ionian sea (Western Greece): Its structural outline deduced from drilling and geophysical data

Abstract

This paper outlines the preliminary structural results obtained by the compilation of geological, drilling and geophysical data in western Greece. Most external geotectonic zones of the Hellenides are included in the geological setting of the marine and insular domain of western Greece: Ionian, pre-Apulian and Apulian zones. The Gavrovo and Pindus zones make a restricted contribution to the marine geological framework (continental shelf of southwest Peloponesus). Besides the geographical setting of the geotectonic units, their general tectonic characteristics allow the following remarks to be made: The main tectonic events younger than Eocene are well-marked in both Ionian and pre-Apulian zones. The detrital sequence shows a fast pinch-out towards the Apulian platform where the Plio-Quaternary clastic layers overlap what are probably late Mesozoïc or early Tertiary limestones. Taking into consideration general tectonic features, we can distinguish a northern area and a southern one, separated by a fault trending 30°N, located on the western margin of Kephallinia, Lefkas Islands: 1. (a) in the northern area we observe a strong tangential tectonism decreasing towards the Apulian platform with transitional characteristics on the pre-Apulian zone (Paxos) where asymmetrical folding occurs; 2. (b) in the southern area (from Lefkas-Kephallinia islands to the S.W. Cape of Peloponesus) the tangential tectomism is well-masked by strong vertical faulting attributed to young Plio-Quaternary deformations. The fast subsidence induces huge diapiric structures in the Ionian zone (salt walls originating from Triassic layers intersect a thick Pleistocene sequence).