A high resolution approach in the recent sedimentation processes at the head of Zakynthos Canyon, western Greece

Abstract

The recent sedimentation processes at the head of Zakynthos Canyon in western Greece have been re-examined using a dense grid of high resolution seismic reflection profiles and sediment cores. The current survey has revealed three new sediment sources that contribute considerably to the filling of the canyon floor that were not detected in previous surveys. These sediment sources are (a) a string of five large pockmarks and (b) a large slide, both along the north Killini shelf, and (c) a canyon (Arcoudi Canyon) dissecting the central Killini shelf/slope. Furthermore, the erosional/depositional area, which was found to lie at the centre of the canyon floor, extends downslope and seems to be actively receiving material mainly from the Killini side. Three potential salt diapir locations were found and steeper slope gradients were proved to border the canyon head, in contrast to the results of the older surveys. Mass movements affect almost the entire part of the slopes bounding the canyon head and can be distinguished in slides, mass flows and turbidity currents. The subbottom structure of the canyon floor confirms this evidence since it is constructed of alternating mass flow and turbidity current deposits. The sedimentation processes are obviously affected by the high seismicity of the area, although salt diapirism and associated high slope inclinations, ascending gas from deeper sedimentary layers and homoclinal stratification seem to be dominant contributing factors. Sediment sources are classified according to their priority in the filling of the canyon floor.