North Marmara Trough architecture of basin infill, basement and faults, from PSDM reflection and OBS refraction seismics

Abstract

The reflection and refraction seismic data collected during the SEISMARMARA Leg 1 survey in the Sea of Marmara provide detailed imaging of sedimentary record and fault activity with deep penetration into its basement. First, a detailed analysis of pre-stack depth-migrated seismic lines crossing the Central Basin enable us to discuss the space and time relations of the large and smaller nested basins of the inner depression, as well as the diversity of style and rate of activity of motion at the diverse basin border faults. Second, forward modeling of OBS refraction arrival times reveals the effect of compaction on the sedimentary pile whereas its layering imaged by MCS as seismic reflectors rather recorded the tectonic evolution. Another major result of the refraction modeling is the identification of the crystalline basement. The latter is imaged about 1 or 2 km deeper than the base of the layered sedimentary sequence imaged on the coincident MCS profiles. This basement exhibits sharp topography across the Central High, the Kumburgaz Basin and the eastern tip of the Cinarcik–North Imrali Basin in an unexpected way with respect to the sea-bottom depressions. We furthermore imaged several large tilted basement blocks, which separate the deep basins as between the Cinarcik and Imrali basins. Despite the varying width of the NMT and the sizes of the tilted blocks, we propose that the imaged finite deformation results from a similar process of partitioning deformation over more than one or even two faults across the NMT that may have changed activity with time and space.