Pre-Holocene Morphobathymetry of Sea of Marmara (SoM) Sedimentary Basins: A Case Study With Precise Correlations Developed by Sediment Cores and HR Seismic Profiles

Late Quaternary paleoceanography and hydrography of the Sea of Marmara (SoM) have been extensively investigated because of its key location between the Black Sea and the Mediterranean Sea. Although the hydrography and paleoceanography of the SoM are reasonably known for the MIS 1-MIS 6, our knowledge of the stages is revealing and based on discontinuous seismic records from shelf cores. Integrated three-dimensional paleomorphologic and sedimentary modeling was used to predict the basin architecture and depositional pattern of sedimentary units in SoM.

By unraveling the structure and decompressing the stratigraphy of the targeted stratigraphic unit, we successfully modeled the ancient bathymetry during the MIS1-2 and MIS4-5 transition periods. Over 700 gridded 3.5 kHz high-resolution seismic profiles were processed, revealing distinct reflectors and stratigraphic units separated by reflectors that signify regional unconformities across 12 sediment piston cores, totaling approximately 25 meters in length. Accurate depth-scaling of chronostratigraphic units within cores is crucial for precise sedimentation rate calculations. Aligning seismic profiles with cores involved cross-referencing Multi-Sensor Core-Logger (MSCL) data with seismic reflection coefficients and amplitudes across various stratigraphic layers. Using data from the MSCL, we produced different synthetic seismograms to identify and correct depth-scale inconsistencies caused by mismatches in the upper sedimentary layers in seismic profiles. This technique is centered on synchronizing synthetic seismograms, derived from high-quality physical property logs, with corresponding CHIRP profiles to rectify these discrepancies. Mapping sequence boundaries, delineated by distinct reflection coefficients and amplitude values across the entire gulf area using pseudo-3D seismic data, allowed for comprehensive representation. To model basin evolution, isopach and isochron maps were constructed using a 2-D cubic B-spline interpolation method.

This study transferring the boundaries determined in marine isotopic periods, MIS5-MIS4, from cores to the acoustic environment for the creation of paleo-depth maps has been completed. Sample comparison models have been prepared on profiles taken from Çınarcık Basin towards Tekirdağ Basin for the application of grid interpolation modeling for different basins, using amplitude values from produced synthetic seismograms.

The robust age models derived from these cores, paired with reflectors corresponding to known levels in existing literature, positioned the marine-lacustrine transition at 13.7 k years before present (ka BP) at a water level of -85 meters and at 97.4 ka BP, the transition from marine to terrestrial environment. Using this timeline, we generated multiple maps illustrating paleo-bathymetry, sediment thickness, and mass-flow charts in the different basins, allowing us to simulate the environmental conditions in the SoM during the transitions.

Keywords: Sea of Marmara, Seismic Stratigraphy, Synthetic Seismogram, Age-Depth Modeling, Paleobathymetry Modelling