Lake Baikal is the only freshwater reservoir on Earth with gas-hydrate accumulations in its bottom sediments, partly due to the activity of mud volcanoes. This paper describes a group of mud volcanoes recently discovered on the slope of the Academician Ridge between the northern and central Lake Baikal basins. Our analysis of diatom skeletons in the mud breccia sampled from the study area shows a high abundance of Cyclotella iris et var. These extinct species were also discovered in a core sample from BDP-98 borehole. Based on the biostratigraphic and seismostratigraphic correlations, the age of the mud breccia in the studied mud volcanoes ranges from the Late Miocene to the Early Pliocene (4.6 to 5.6 Ma). The correlations suggest that the material originated from a depth of less than 310 m below the lake bottom.
Detailed geological and geophysical investigations of the underwater topography of Lake Baikal, based on single-channel high-resolution seismic profiling and bathymetric survey using an ELAC SeaBeam 1050 multibeam echosounder, as well as the data obtained during diving of MIR deep-sea manned underwater submersibles determined the morphological characteristics of the Posolsky Bank and Kukuy Griva elevations suggesting that their elevated parts represent fragments of the once common delta surface of the Selenga River. The current relief of these structures resulted from the joint activity of tectonic and underwater erosive processes. Sediments at the base of the slope of the Kukuy Griva are likely to be no older than 1.8 Ma.
The article outlines the main approaches to studying the bottom topography of Lake Baikal and interpretation of bathymetric data. Measurement equipment and experimental data processing algorithms are described. A measuring complex is based on using the Kongsberg EM710S multibeam echosounder which allows one to take a detailed digital elevation model of the bottom. The paper demonstrates experimental results obtained during a series of expeditions to the Baikal in 2015 – 2019. Currently an area of about 12117 km2 (∼38%) of Lake Baikal bottom has been explored. Examples of a digital model of the Baikal bottom are also presented. The paper demonstrates 3D models of detected water columns showing intense of a gas bubbles emanation near the mouth of Selenga river, acoustic images of the Baikal Gigaton Volume Detector (Baikal-GVD), and a bathymetric map of Academician Ridge that was previously examined with the Mir 1 and Mir 2 in July 2009.
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