Morphogenetic and palaeoenvironmental evolution of the Lagoon of Kotychi in western Peloponnese, Greece, during the Holocene

Multidisciplinary researches allowed us to describe the morphological and palaeoenvironmental dynamics of the Kotychi Lagoon in the Holocene. This transition environment is separated from the open sea by a low barrier and has limited communication with it through a stable, short, and narrow inlet. The lagoon is limited by a modern alluvial plain made by several streams. Along the landward lagoon margins, small-scale deltas of these streams prograded into the lagoon. Intertidal and supratidal mud flats developed among the deltas, covered with vegetation (e.g., Salicornia sp.). Northwards, the lagoon is limited by a large marshy area. To the North of this area, a group of well-developed beach ridges parallel to the current shoreline is present. These are affected by erosion, and migrating sandy dunes have buried some of the beach ridges. South of the lagoon, the ancient Peneus River delta is located. The bottom depth in the Kotychi Lagoon decreases gradually from the landward of the barrier to the inner lagoon margins. Although the maximum depth is about 2.5 m in front of the inlet, the average depth is only 0.5 m. The main lithological type of the lagoon sediments is sandy mud, with some ex- ceptions in the eastern edge of the lagoon and some locations around it where silty-clayey sediment was deposited. According to geomorphological surveys and palaeoecological interpretation of two cores analysis as well as with previous researches and datings, the recent morphogenetic evolution of this lagoon is mainly due to three Holocene phases: 1) 7-4 ka BP: sediment filling, development of a primitive open lagoon; 2) 4 – 1.5 ka BP: development of sandy ridges, partially closed lagoon; 3) 1.5 ka BP - present-day: closed lagoon, with one mouth. Fractal analysis confirms that currently the basin shape is evolving from a lagoon towards a coastal pond, due to contraction and filling up by sediments.