Formation, evolution and demise of a tectonically controlled volcanic lake: A case study from the lower Pleistocene Sousaki succession

Abstract

Abstract The complex interaction of local tectonics and volcanism usually produces palaeoenvironments that require to be studied in detail in order to define the role of each factor in the local palaeoenvironmental evolution. This is the case for the Sousaki Basin lying at the eastern part of the Gulf of Corinth. It presents a complex Pliocene and Pleistocene stratigraphy, affected by deformational processes due to the local tectonic regime. The Sousaki volcano is a low standing volcano that constitutes the western endpoint of the South Aegean Volcanic Arc and may also contribute to the palaeoenvironmental evolution of the basin. The studied section, in the Sousaki Basin, consists of marly and conglomeratic layers with intercalations of organic rich sediments. The base of the section consists of impermeable volcanic products. A micropalaeontological analysis based on 29 samples has been conducted in order to reconstruct the palaeoenvironment after the termination of the activity of the last volcanic period. A diversified fauna has been retrieved, consisting of Gelasian (early Pleistocene) ostracods, gastropods, diatoms, charophyte gyrogonites, thecamoebians, fish otoliths and teeth. Count-based statistical treatments performed on ostracod species revealed that a volcano-tectonic lake evolved after the emplacement of the volcanic products in the basin. Afterwards, a braided river environment dominated the landscape. Due to the lateral migration of the riverbed, several laterally evolving sub-environments were established, ranging from marginal lakes to marshes. Ultimately, the palaeoenvironmental reconstruction of the study area revealed the formation, evolution and demise of a tectonically controlled volcanic lake.