Canyons of the Eastern Shore of Southern Baikal: Morphology and Genesis

Аннотация

We present new data on canyons and other morphological features of the underwater slope on the eastern coast of the southern basin of Lake Baikal obtained during high-resolution bathymetric surveys of the bottom using multibeam echo-sounders ELAC SeaBeam 1050 and Kongsberg EM710S. Based on the array of bathymetric data generated, we have constructed a digital elevation model for which we used at once several software products responsible for individual tasks. Analysis of the digital elevation model has indicated that tectonic processes played the leading role in the creation of the main, most noticeable forms of relief on the underwater slope. These processes formed a graben-like depression to the south of the Posol’skaya Bank and tectogenic scarps at the foot of the southern slope of the depression as well as canyon-shaped valleys along the entire coast. We have determined that the unusual direction of the Posol’skii canyon across the coastal slope and the relatively small size of the fan in this canyon are due to the history of the tectonic development of this part of the shoreline: in the past, the canyon valley skirted the continental slope of the Selenga river paleodelta from the southeast, and after the formation of a younger graben-like depression it preserved the old direction of its channel. We have suggested that underwater erosion processes initiated tectonic lowering of the floor of the basin. Ultimately, this resulted in the destruction and erosion of the ancient geomorphological surfaces and formation of the ridge and hollow relief and canyon valleys that are currently at different stages of development. Landslide forms resulting from paleoseismic dislocations play a secondary, yet a significant role in the relief of the slope, which undoubtedly complicated the geomorphological surface. It is assumed that the fans created by the activities of the canyons, the ancient channels of canyons and landslide bodies may be promising for the search for hydrate-bearing structures in this part of the lake.