Sea-level stands and Holocene geomorphological evolution of the northern deltaic margin of Amvrakikos Gulf (western Greece)

摘要

The present contribution aims to identify the various sea-level stands in association with deltaic sedimentation processes, within Amvrakikos Gulf (western Greece); the latter is a semi-enclosed and relatively shallow (<65 m) embayment, separated from the open Ionian Sea by a rather narrow and shallow (< 10 m) passage. Furthermore, this investigation has been based, primarily, upon the identificationof different sedimentary environments within sedimentary cores, radiocarbon dating of characteristic stratigraphic horizons; and, secondarily, upon subaerial and subaqueous geological and geomorphological characteristics as well as archeological evidence. On the basis of the above information, the Holocene evolution of the northern deltaic margin of the Amvrakikos Gulf is attributed to the active interaction between sea level rise, regional tectonism, riverine sediment supply and differential rates of the sedimentation. The Holocene formation and evolution of the northern deltaic margin of the Amvrakikos Gulf is attributed primarily to the deltaic progradation of the River Arachthos, whilst the action of River Louros has been restricted only to its northwestern part. Although a regional curve of sea level rise for the Holocene period could not be constructed with accuracy, due to the above-mentioned complexity of the operating processes, it is most likely that in the beginning of the Holocene period (earlier than 10 000 years BP) sea water from the open Ionian Sea had already entered into the Gulf, occupying water depths 35-40 m below present mean sea level. Following, sea level was rising at a rate of 0.5+0.02 cm per year up to ca 2000 years BP. Within the last 2000 years, sea level has fluctuated within a range of 1-2m.