25-31 July 2019, the INQUA Congress was held in Dublin, Ireland. The Congress was organized in twelve parallel sessions held simultaneously in five main areas (Coastal And Marine Processes, Paleoclimate, Human and Biosphere, Stratigraphy and Chronology, Terrestrial Processes, Deposits and History). Plenary reports and poster sessions were also organized daily.
VSEGEI Regional Geoecology and Marine Geology Department presented an oral report “New data about deglaciation of the Eastern Gulf of Finland basin, the Baltic Sea” (session “Geological and geophysical archives of ice sheets on continental shelves”) and three poster presentations on morphology and genesis of the Quaternary sediments of the bottom and coasts of the Eastern Gulf of Finland, and modern exogenous geological processes of the East Siberian Sea bottom. The reports aroused great interest of the audience, including in connection with the Transarctic expedition organized this year, during which it is planned to conduct core sampling in the East Siberian Sea with the participation of the GEOMAR Helmholtz Centre for Ocean Research Kiel.
Based on the analysis of the presentations that we have listened to, we can state that the use of modern high-resolution geological and geophysical methods (multi-beam echo sounding, 3D seismic and acoustic profiling), which allows for continuous survey, not only of the seafloor surface, but in some cases of buried geological bodies is more and more widespread and actively developed in mapping of the Quaternary sediments of the bottom of seas, oceans, and large lakes. As a result of the data obtained during such surveys, previously unknown geomorphological forms are revealed, which fundamentally changes the idea of the structure of near-surface geological section and the development history of areas in the Quaternary. Similar methods are used by experts from the Regional Geoecology and Marine Geology Department when working on grants from the RSF and RFBR in the Eastern Gulf of Finland thanks to successful cooperation with the Institute of Oceanology of the Russian Academy of Sciences (joint expeditionary research), whose vessels have the appropriate modern equipment. The results of these works were given in an oral presentation (Appendix). Numerous discoveries of various glacial forms (circular moraines, tunnel channels, dead moraines, etc.) on land within previously seemingly well-studied areas were revealed during the Earth's surface survey using LIDAR technology.
A series of presentations was devoted to the identification of the Late Glacial deposits, which are characterized by specific deformation textures (diapirs, draping, etc.), originating presumably from seismic activation as a result of compensatory uplift of the Baltic Shield.
It should also be noted the widespread use of non-invasive laboratory methods that allow high-resolution core studies (including bottom sediments) to be performed (XRF X-ray fluorescence analysis (resolution to 1 mm, measurement time 1 sec, set of elements to 40); microtexture analysis using X-ray shooting, etc.). The transition from expensive discrete types of sample analysis to obtaining large amounts of information about the physical properties, chemical composition, and age of deposits with high resolution allows us to reach a fundamentally new level of paleogeographic and paleoclimatic reconstructions.
Geochemical studies are characterized by the use of a wide range of chemical isotopes to solve a variety of problems. Thus, to assess the anthropogenic impact on sedimentation, we used the determination of δ15NNO3- and δ18ONO3- isotopes; to determine the paleotemperatures and age of deposits, δ18O in diatoms, to reconstruct the biogeochemical sedimentation cycles, δ30Sidiatom, to study the groundwater sources, δ18O and δ2Н, to determine the age of biogenic carbonates, 87/87Sr etc. A comparatively innovative and actively developed is the DNA analysis of organic matter of plant residues in the Quaternary sediments for taphonomic analysis and restoration of sedimentation paleoconditions.
Methods for determining the Quaternary deposit age are quite rapidly developing. Along with the already traditional OSL (optically stimulated luminescence) of quartz, the results of such methods as violet stimulated luminescence (VSL), isothermal thermoluminescence (ITL), allowing to operate in the age range to 1 million years, are presented. New methods have been developed for determining age from feldspar using infrared (IR) stimulation (IR stimulated luminescence and IR photoluminescence) and IR radiation (for example, IR radiofluorescence). OSL is sometimes used in combination with electron spin resonance (ESR) to determine the time and velocity at which electrons are captured and thermally released in minerals in response to in situ radiation exposure and rock cooling. Among the isotope analyses for geochronological studies, U-Th, 26Al, 14C (including for pollen age determining), 10Be (for determining the time of deglaciation onset), 87/87Sr (for determining the biogenic carbonate age) are used. Quite exotic geochronological methods are, for example, dating by the decay of intracrystalline protein (IcPD) in mammoth tooth enamel. It should be noted that age determinations obtained using different methods for the same samples often differ by hundreds and thousands of years.
Map of the Quaternary sediments of the Virgin Islands key area, compiled from continuous acoustic profiling analysis from the adjoining network of lines (A): Holocene: 1 – marine littorinia (LIT) and post-littorinia (pLIT) sediments (mud); 2 – Ancylus lacustrine deposits (ANC); Upper Neopleistocene: 3 – glacial-lacustrine clay of Baltic Ice Lake (BIL); 4 – homogeneous clay (BP); 5 – varved clay (LG); 6 – glacial deposits (G); lithological types of deposits 7 – silt-pelitic mud; 8 – homogeneous clay; 9 – varved clay; 10 – diamicton. Interpretation of CSP lines with outcrops of sediments of various acoustic complexes (B) to the bottom surface. 3D surfaces constructed from the results of CSP line analysis: glacial deposits (C-a), Upper Neopleistocene glacial-lacustrine deposits (C-b), bottom surface (C-c). An example of CSP line interpretation (D) (GSS - gas saturated sediments)
Map of the Quaternary deposits of the Sommers Island Region key area, compiled from continuous acoustic profiling analysis from the adjoining network of lines (A): Holocene: 1 – marine littorinia (LIT) and post-littorinia (pLIT) sediments (silts); 2 – Ancylus lacustrine deposits (ANC); Upper Neopleistocene: 3 – glacial-lacustrine clay of Baltic Ice Lake (BIL); 4 – homogeneous clay (BP); 5 – varved clay (LG); 6 – glacial deposits (G); lithological types of deposits 7 – silt-pelitic mud; 8 – homogeneous clay; 9 – varved clay; 10 – diamicton. Interpretation of CSP lines with outcrops of sediments of various acoustic complexes (B) to the bottom surface. 3D surfaces constructed from the results of CSP line analysis: glacial deposits (C-a), Upper Neopleistocene glacial-lacustrine deposits (C-b), bottom surface (C-c). An example of CSP line interpretation (D) (GSS - gas saturated sediments)