ACTIVE FAULTING IN THE NORTH AEGEAN BASIN

Abstract

Detailed analysis of air gun lithoseismic profiles in the north Aegean basin has permitted construction of a tectonic map on the pre-existing detailed bathymetric map. The basin is structurally subdivided into three parts. (1) A continental platform borders the basin at ̃200 m depth and shows no significant internal deformation. (2) Continental slope areas, usually occurring at 400-900 m depth, are shaped by major marginal faults (>1 km throw) trending mainly northeast-southwest and secondarily northwest-southeast. The dominant structure of the basin is a 160 km-long northeastsouthwest- trending fault extending from Skopelos to Limnos, which borders the basin's southern margin and accommodates more than 2 km of throw. This structure probably represents the continuation of the North Anatolian fault. (3) Basinal areas at ̃900-1650 m depth include a complex alternation of ridges and basins bordered by active faults. The main structural trend within the basinal areas trends east-west and dominates in the western part of the basin. In the central and eastern parts, northeastsouthwest structures become more important. Late Pliocene-Quaternary fault throw ranges between a few tens of meters and 200 m, with higher vertical throws occurring only on northeast-southwest marginal faults bordering the intermediate horst structure. Several northeast-southwest shear zones occur in the central part of the basin parallel to the major southern northeast-southwest marginal fault. A distinctive eastwest shear zone occurs in the southwestern part of the basin, where maximum subsidence is observed. An angular unconformity occurs within the Plio-Pleistocene sequence linked to uplifted/tilted neotectonic blocks and anticlinal hinges. The overall interpretation of the mapped structures indicates oblique opening of the basin marked by northeast-southwest strike-slip on both marginal and internal faults, east-west strike-slip faults only in the basinal areas, and northwest-southeast normal faults on the southwestern (Pelion) and northeastern (Athos) margins. This structural architecture is the combined result of the WSW escape of Anatolia on dextral northeastsouthwest and east-west strike-slip faults due to Eurasia-Arabia collision and the extension on northwest-southeast normal faults associated with the southwest pull of the retreating Hellenic subduction zone in the Ionian Sea to the west. The main effect of this complex deformation is an increase in the normal character of fault structures from northeast to southwest. © 2006 Geological Society of America.