Formation & evolution of the Ververonda Lagoon (Porto-Heli Region,SE Argolic Gulf) during historical times, on the basis of geophysical data and archeological information

摘要

The scope of the present contribution is to investigate the formation and evolution of the Ververonda 'lagoon' that belongs to the South Argolid peninsula (Porto Heli region) during the last transgression (Holocene) period. This is achieved by utilising existed information and the production of the appropriate supplementary data; the former refers to geology, seabed morphology and stratigraphy, relative sea-level rise and archeological evidences, while the latter involves in-situ coastal geomorphological mapping, analysis of surficial sediment samples, the collection of a sediment core and the application of geophysical techniques (e.g. electrical resistivity). On the basis of the interpretation of all the above infor-mation, it has been found that the Ververonda lagoon was formed after the 2nd century A.D. and has kept its lagoonal hydrological characteristic until the middle of the 20th century when two artificial channels permit exchange of water with the open bay. During the late Mesolithic period (ca. 6,000 years BC) the lagoon was coastal land with the bay of Ververonda being mach smaller in size. At the end of the Early Helladic period (some 2,000 years BC) the sea has invaded the inner part of the Ververonda Bay, covering most of the current lagoonal area. The sea have continued to rise, not necessarily with a stable rhythm, reaching a level of approx. 2 m below its present stage at Roman period (2,000 BP). At this period the lagoon was deeper while the ephemeral streams discharging along the northern side of Ververonda Bay (including the present lagoonal coast) provided substantial sediment influxes. Thus, over the last 2,000 years when sea-level was rising slowly, marine processes had formed gradually the barrier that separated eventually the inner part of the Bay forming the Ververonda lagoon; this process is estimated to have been concluded some hundred years ago. Human interference during the second half of the 20th century destroyed its lagoonal hydrological character by establishing free-communication with the open bay waters, through two artificially dredged channels.