GEOPHYSICAL INVESTIGATION OF THE SHALLOW SUBSURFACE OF THE KOLPOS ATALANTIS WITHIN THE NORTHERN EUBOEAN GULF

The Northern Euboean Gulf (Vorios Evvoikos Kolpos) in Central Greece reaches depths of over 500m, stretches 100 km from the 50-m wide straight at Chalkida in the SE to Lamia and the straights of Diavlos Oreon (4-km wide) in the NW, where the submerged landscape creates lacustrine conditions during lowered sea levels. Several fault systems cut diagonally across this region, with tectonic blocks of approximately 10-km wide creating stretches of coast with differential relative sea-level rise rates. This area provides a large natural experiment of differential relative sea-level rise rates in a very small area, and the preservation potential of varied sedimentary environments under varied sea-level rise scenarios. The goal of this project is to understand the relative evolution of the paleolandscape in an area with diverse sea-level change rates, with limited variation in other oceanographic conditions.

In order to document the varied landscape now buried by differential subsidence rates, a high-resolution geophysical survey was conducted to document the general stratigraphic framework of the nearshore zone. This acoustic geophysical study, focused on a 20-km stretch of embayed coastline between Arkitsa and Theologos on the SW coast, documents the shallow stratigraphy from the coastal zone out to approximately 175m (5-km offshore) where submarine canyons begin to feed the basin to the NE.. Several small rivers empty into the area, and the geology comprises sandy to bouldery beaches backed by a range of uplands consisting of Mesozoic limestones, ophiolites, Tertiary marine deposits, and modern fluvial and alluvial systems. Offshore, approximately 150 km of chirp subbottom profiler data were collected, with several distinct stratigraphic zones recognized. These zones range from thick (>25m) transparent sequences in the north, to distinctly bedded sequences isolated by bedrock highs throughout the central section, to large seaward dipping sequences offshore the Atalanti alluvial plain. As we continue to study this region in more detail, we expect to better understand the response of differential sea-level rise scenarios against a complex bedrock geological system will provide a natural model of coastal response to different areas of the world.