High-resolution geological mapping towards an understanding of post-glacial development and Holocene sedimentation processes in the eastern Gulf of Finland; an EMODnet Geology case study

Analyses of high-resolution multibeam and sub-bottom profiling data, acquired during marine geological field cruises between 2017 and 2019 in the eastern Gulf of Finland (Baltic Sea), enabled the detailed mapping of Quaternary deposits, and revealed diverse submerged glacial and post-glacial landforms (e.g. streamlined moraine ridges, large retreat moraine ridges, De Geer moraines and kettle holes). The morphology of these glacial features provides evidence of the ice-sheet retreat direction and rate throughout the deglaciation of the region, which occurred between 13.8 and 13.3 ka BP (Pandivere-Neva Stage) and 12.25 ka BP (Salpausselka I Stage). Analysis of sub-bottom profiling, supported by piston long-core sampling, indicates periods of bottom erosion/non-deposition during the Holocene caused by relative water-level regressions. Significant negative relief features are also observed in the area for the first time. These linear and curved V-shaped furrows are several kilometers long and 5 m deep, and are tentatively ascribed to bottom current and gas-seepage processes.