Geological formations PDF Print E-mail

From the geological point of view, the island consists of the alpine basement, overthrust by a Tethyan ophiolitic nappe and postalpine formations. 


Geological sketch map of Lesvos Island

The alpine basement is a series of formations from the Carboniferous until the Upper Triassic   and it consists entirely of metaclastic rocks with lenses and intercalations of crystalline limestones and dolomites. It is characterized by a very low-grade metamorphism.


The formations are extended on the southeast part of the island. They consist of schists (mainly micaceous, sericitic and chloritic) alternating with metasandstones (mainly arkoses), quartzites and crystalline carbonate rocks in the form of lenses and intercalations. The age of these formations has been determined by the characteristic fossils found in the crystalline carbonate rocks of these formations. In several localities and in different stratigraphic horizons, a rich fauna was found consisting of foraminifers, bivalves, gastropods, echinoderms and corals.
The Tethyan ophiolitic nappe occupies a large area in the southeast part of Lesvos and towards the northwest they are covered by the volcanic formations of the Island. The rocks of the ophiolitic tectonic nappe have suffered at least one very low grade metamorphism.
The ophiolitic rocks are found overthrust, in their larger part, on the alpine formations and they are divided into two parts. The upper part consists entirely of ultramafic, dark in colors rocks of various degrees of serpentinization. Veins of pyroxenites and gabbros intersect these ultramafic rocks. The lower part consisting of metamorphic basic ophiolitic rocks, mainly amphibolites and amphibolitic schists, always intercalated tectonically between the upper part of the ophiolitic rocks and the underlying alpine formations.
The postalpine formations are extended in large areas of the island and including mainly volcanic rocks  and Neogene marine , lacustrine and alluvial deposits. The latter deposits are well represented in Vatera formation.


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