Sedimentological and clay mineralogical investigations in Maliakos Gulf, eastern Greece

The distribution patterns of fine-grained sediments (sand, silt and clay) and the relative abundance of clay minerals (illite, smectite, chlorite and kaolinite) in the clay fraction (< 2 µm) of surficial sediments in Maliakos Gulf is examined. Sedimentation processes within the gulf are controlled by the presence and evolution of the delta of the River Sperchios, which forms the western and southern coastlines of Maliakos Gulf. Sand is more abundant near the river mouths and along the northern shoreline, with percentages in excess of 80%. The silt content is highest (40-50%) at the delta front area, whilst clay (> 60%) dominates in the central part of the gulf. The most abundant clay mineral present is illite (60-80%). The smectite content varies between 5% and 20%, whilst the chlorite-kaolinite content lies between 15% and 25%. Clay minerals are of terrigenous origin, with their abundances related to the lithology of the region over which the rivers drain into the gulf. The clay mineral distributions may be explained in terms of differential settling (size sorting), flocculation and the action of biophysicochemical processes (i.e., pelletization).