Estuarine, Coastal and Shelf Science (2000) 00, 000–000 doi:10.1006/ecss.1999.0620, available online at http://www.idealibrary.com on Origin and Distribution of Clay Mineralsin the Alexandroupolis Gulf, Aegean Sea, Greece K. Pehlivanogloua, A. Tsirambidesb and G. Trontsiosb aDepartment of Oceanography, Hydrographic Service, Hellenic Navy, T.G.N. 1040, Holargos, Athens, Greece; e-mail:
[email protected]. bDepartment of Geology, Aristotle University of Thessaloniki, 540 06 Thessaloniki, Greece Received 29 March 1999 and accepted in revised form 18 December 1999 The mechanisms of clay mineral distribution in Alexandroupolis Gulf are studied. The annual solid supply of the Evros River, flowing into the Gulf, amounts to at least 1 000 000 m3. The surficial bottom sediments are commonly fine-grained and are distributed along zones almost parallel to the coastline. In the central part of the Gulf clay-silt size sediments predominate. The main clay minerals in the size fractions (2–1, 1–0·25 and <0·25 m) are illite, smectite, kaolinite and in small amounts interstratified illite/smectite. Quartz, feldspars, amphiboles and chlorite occur in traces in the coarser fraction (2–1 m) of some samples. All the above minerals are the weathering products of the Evros River drainage basin, as well as of the Neogene and Quaternary unconsolidated sediments of the coast. The hydrodynamic regime and physical grain size are the main mechanisms, which control the distribution of the clay minerals in the Gulf. The low content of kaolinite in all samples and the presence in traces of chlorite and amphiboles in some coarse clay fractions may be due to the unfavourable climatic and physicochemical conditions, as well as to the rapid transport and deposition of freshly weathered material.