Geomorphology and Late Pleistocene–Holocene Sedimentary Processes of the Eastern Gulf of Finland

Abstract

In 2017, a detailed study of the Eastern Gulf of Finland (the Baltic Sea) seafloor was performed to identify and map submerged glacial and postglacial geomorphologic features and collect data pertinent to the understanding of sedimentation in postglacial basins. Two key areas within the Gulf were investigate using a multibeam echosounder, SeaBat 8111 and an EdgeTech 3300-HM acoustic sub-bottom profiling system. High-resolution multibeam bathymetric data (3-m resolution) were used to calculate aspect, slope, terrain ruggedness and bathymetric position index using ArcGIS Spatial Analyst and the Benthic Terrain Modeler toolbox. These data and resultant thematic maps revealed, for the first time, such features as streamlined till ridges, end-moraine ridges, and De Geer moraines that are being used for the reconstruction of the deglaciation in the Eastern Gulf of Finland. This deglaciation occurred between 13.8 and 13.3 ka BP (Pandivere-Neva stage) and 12.25 ka BP (Salpausselkä I stage). Interpretations of the seismic-reflection profiles and 3D models showing the surfaces of till, and the identification of the Late Pleistocene sediment and modern bottom relief, indicate deep relative water-level fall in the Early Holocene and, most likely, several water-level fluctuations during this time.

Impact of climate change on sedimentation processes in the eastern Gulf of Finland during the Middle to Late Holocene

“…According to the acoustic data and using comparison with geological (core description) data, AU5 has been interpreted as glacial till from the Late Pleistocene, with a highly dissected surface. Within some areas (for example, sedimentary basin 8E), the surface of the Last Glacial till is represented by several large ridges with small subparallel ridges of the De Geer moraine (Ryabchuk et al 2018). Dense and distinctly laminated brownish varved clays of about 5 m thick represent AU4, with an average thickness of about 6 m. The next unit, AU3 (with a maximal thickness of 8-9 m) is represented by less dense thin-laminated (1 mm and less) to homogenous brownish clays of the Baltic Ice Lake sediments (with an average thickness of about 5 m).…”

“…The main characteristics of the EGoF are: (i) low rates of recent (last 2000 years) glacio‐isostatic rebound (0–2 mm a –1 ) and slow relative sea‐level rise (according to the data obtained from a Kronshtadt sea‐gauge, the rate of sea‐level rise from 1835 to 2005 was 0.7 mm a –1 ) (Gordeeva & Malinin 2014); (ii) relative shallowness, with the average water depth being 20 m and a maximum of 92 m to the west of Gogland Island (Petrov 2010); (iii) relatively low relief contrast caused by accumulation and erosion processes; and (iv) Holocene mud accumulation localized within sedimentary basins positioned at water depths ranging from 5 m in Neva Bay, to 70–80 m in the vicinity of Gogland Island (Ryabchuk et al . 2018).…”

Charting the Course for Future Developments in Marine Geomorphometry: An Introduction to the Special Issue

“…While simple methods to correct for different types of artefacts in DBMs are still lacking, the awareness of artefacts and their potential impacts on applications is now regularly acknowledged and reported on (e.g., Ryabchuck et al [27]), which used to be very uncommon [28,29]. In this special issue, Hughes Clarke [30] addresses the main factors that affect data quality in bathymetric data collected using multibeam echosounders.…”

“…The author asserts that the formation, maintenance, and modification of the Mendocino Channel have occurred through a combination of significant and numerous earthquakes and wave loading resuspension by storms forming turbidity currents. Ryabchuk et al [27] used both a multibeam echosounder and a sub-bottom profiler to identify and map submerged glacial and post-glacial geomorphological features, enabling them to interpret the sedimentation regimes of two post-glacial basins in the Gulf of Finland. The geomorphological analysis has led to the identification of Late Pleistocene sediment and more modern bottom relief, which together indicated the occurrence of a deep-water level fall in the Early Holocene and multiple water-level fluctuations during this period.…”