Tectonic Ledges at the Bottom of Lake Ladoga

EGU21-1789 https://doi.org/10.5194/egusphere-egu21-1789 EGU General Assembly 2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License.

Tectonic ledges at the bottom of Lake Ladoga

Vladimir Anokhin1,2,3, Dina Dudakova1, and Mikhael Dudakov1 1Institute of Limnology RAS, St. Petersburg, Russian Federation ([email protected]) 2St. Petersburg Research Centre RAS, St. Petersburg, Russian Federation ([email protected]) 3Herzen State University, St. Petersburg, Russian Federation ([email protected])

For the last several years, the Institute of Limnology RAS has been conducting geological and geomorphological studies of the bottom of Lake Ladoga, the largest lake in Europe. Beginning in 2018, these studies began to use underwater photo and video camera, created at INOZ RAS. The use of this new research tool led to the discovery of a number of new facts of the structure of the bottom of Lake Ladoga. In particular, during the 2020 field season, the authors discovered in several areas of Lake Ladoga the existence of underwater subvertical scarps, composed of bedrocks. At the same time, the submarine towing boat stood in one place, and the camera vertically upward from depths of about 100 - 120 meters to depths of 20 - 30 meters. During this entire rise, the camera recorded the bedrock ledge with vertical and even negative angles. No traces of glacier processing were found, which indicates the Holocene age of the found scarps. In 2020, such ledges were found in 3 regions of Lake Ladoga: in a depression near the Pitkyaranta in the northeastern part of the lake, in the Suuri-Viroluoto trench in the northern part of the lake and on the western underwater slope of Valaam Island. A mention of the possibility of the existence of such ledges (up to the first tens of meters in height) in the northern part of Lake Ladoga is found in the works of V.A. Rumyantsev and V.N. Rybakina (2012), A.V. Amantov (2014), Bolshiyanov (2018). M.A.Naumenko, who studied the underwater slope of Valaam Island, considered the maximum angle of this slope to be 60 degrees (2019). We found sub-vertical ledges up to 100 meters high. In addition, these scarps are in spatial relationship with the existing tectonic faults, confirming their significant fault component. The presence of young vertical high ledges at the bottom of Lake Ladoga indicates powerful young tectonic movements in this region.