Fishing capacity of South Baikal in terms of tourism development and limitations on fishing industry

The article considers eco-economic aspects of using the fishing capacity of the basin of South Baikal in the framework of the development of tourism of the coastal territory within Slyudyansky Municipal District of Irkutsk Oblast and within the entire southern Baikal Region. The article proposes to more strongly focus on developing sport and recreational fishing in this most developed area of Lake Baikal. The eco-economic and legal analysis carried out by the authors allows them to conclude that the traditional regulation of the stock of omul in Baikal by determining the total allowable catches and quotas is not effective enough, since it has led to the prohibition of not only industrial but also limitation of sport and recreational fishing for omul. At the same time, there is no reliable data that recreational fishing along the southern coast of Baikal is the reason for the decrease in the total stocks of omul in Baikal. On the contrary, the South Baikal fishing area can become the basis for a more dynamic development of the tourism industry in the region, including such types of it as cognitive tourism, ecological tourism and sports and recreational one. Moreover, it is the South Baikal fishing area and the coastal territory of Slyudyansky Municipal District that can become a testing site for developing more optimal (considering the specifics of various areas of Lake Baikal) ecological approaches to the regulation, rational use and reproduction of the stock of omul in Baikal for the purposes of sport and recreational fishing at Lake Baikal, as well as development of an environmentally friendly tourism industry in the region. The authors propose to review the strategy of fishery development of the stocks of omul at Lake Baikal and remove restrictions on recreational fishing, accompanying this with organizational and legal measures that allow obtaining reliable statistical data on catches. Precisely in this most economically developed area of Lake Baikal it is advisable to practice the organizational and legal mechanisms for the environmentally friendly development of tourist and recreational activities based on the available water bioresources of the unique lake.

Occurrence of Tankhoy field coals in South Baikal bottom sediments

The purpose of the study is to describe the first finds of coal-bearing clays and coals in the bottom sediments of the southern basin of Lake Baikal and compare them with terrestrial coal-bearing deposits of the Tankhoy field. Comparative analysis of the lithological composition and colour of bottom sediments and terrestrial sections, as well as the concentration of organic carbon and conducted palynological analysis allowed their correlation. At the lake’s depth of 900 m the authors discovered a coal-bearing strata in situ (st 56), which later was stratigraphically correlated with the terrestrial coalbearing part of the Tankhoy suite. The fragments of coal found in bottom sediments basically along the entire Tankhoy field, especially bedrock coals on the underwater slope in South Baikal up to 1300 m deep prove the distribution of the coal-bearing part of the Tankhoy suite in the sublacustrine part of the lake throughout the entire slope (from 5 to 10 km offshore) and confirm the distribution area of the Tankhoy paleolake over a significant area of the contour of modern southern basin of Lake Baikal. The finds of coal-bearing strata on these and other various sub-bottom depths, i.e. under various pressure and temperature conditions, suggest that coals themselves and coal-bearing mudstones may be a generation facility of secondary microbial methane. This should be taken into account when searching for gas hydrocarbon and gas hydrate accumulations as well as assessing methane cycles in Lake Baikal.

Is a High Abundance of Spring Diatoms in the Photic Zone of Lake Baikal in July 2019 Due to an Upwelling Event?

A high abundance of planktonic microalgae is typically thought to be related to their ‘bloom’, that is, to active population growth. Diatom blooms in the photic zone of Lake Baikal generally occur during hydrological spring (April–June); when the summer arrives and the surface water temperature increases, diatoms are replaced by other microalgae. In July 2019, we found a concentration of the diatom Fragilaria radians at a station in South Baikal that was extremely high for that season. This species generally blooms in spring, but in spring (May) of 2019, this alga was nearly absent from the phytoplankton population. Microscopic analysis of the sample taken in July 2019 revealed that the cells were in a dormant stage. The species composition of microalgae in phytoplankton samples from May 2018 and July 2019 was similar. According to the temperature profile analysis, a summer upwelling event from a depth of ca. 100 m occurred in 2019. We hypothesised that this event caused the resuspension of microalgae, including Fragilaria radians, which were deposited on the slopes of the lake in 2018. Hence, the high abundance is not always a ‘bloom’ or an active growth.

TRACES OF HIGH SEISMIC ACTIVITY IN THE UPPERMOST SEDIMENTS OF LAKE BAIKAL, SIBERIA

Sedimentation in Lake Baikal is significantly affected by continuous seismic activity in the Baikal Rift Zone. Our study shows that historical earthquakes, as well as recent seismic events, considerably influenced sedimentation in this deep tectonic basin. Here we present some of the results of extensive international research activities during the period of 1996–2019. To identify traces of seismic events in the uppermost sediments (<1.5 m), short cores were recovered from many coring stations throughout the entire lake. Based on lithological descriptions, measurements of magnetic susceptibility, and concentration of inorganic and organic components, we identified earthquake indicators in the sediment cores. Impacts of historical earthquakes were traced within South Baikal (near the Sharyzhalgai Station and the Station 106-km of the Circum-Baikal railway, hereafter CBR) and Proval Bay (near the Selenga River delta).

Overturned Eocene – Lower Pliocene alluvial stratum on the southern coast of Lake Baikal and its neotectonic significance

The study is focused on a section of sediments exposed on the right bank of Mishikha River, Russia. These sediments have a wide range of ages, from the Eocene to the Lower Pliocene. The stratigraphic subdivision of the section is based on the lithogeochemical data and X-ray phase analysis of the mineral compositions. The particle-size analysis shows the alluvial origin of the deposits. Their ages are constrained by spore-pollen spectra in three palynozones: I – Eocene – Oligocene, II – Early – Middle Miocene (subzone a – Tsuga, Picea in the lower part, and Quercus, Taxodiaceae, Momipites, Carya in the upper part; subzone b – Fagus, Quercus, Tsuga), and III – the Late Miocene – beginning of the Pliocene (subzone ν – Ulmus, Juglans, Carya; subzone g – Carya, Alnus). The section shows a combination of normal and overturned sedimentary layers. The tectonic displacement of the block with its flip was accompanied by the entry into contact of the unlithified Pliocene sediments with a rigid bed and the development of a landslide. The lower age limit of deformations is constrained from the youngest (beginning of the Pliocene) spore and pollen spectrum extracted from deformed layers. It is suggested that the overturned layers result from strike-slip deformations of the sediments at the beginning of the late orogenic stage of the Baikal rift development. The regional correlations of the sedimentary strata give grounds to conclude that the Mishikha section is characteristic of alluvial sedimentation that dominated at the eastern end of the Tankhoi tectonic step (Mishikha-Klyuevka paleovalley), in contrast to the Tankhoi block in the central part of the step, wherein a thick Lower Miocene stratum of swampy-oxbow sediments accumulated. The stratons of the Mishikha section correlate with sedimentary units detected by drilling in the Selenga delta at the central part of the South Baikal basin.

Volcanic rocks and pseudotachylytes from sources of crust-mantle complementary layers: Insight into geodynamics of the Baikal Rift System, Southern Siberia

&lt;p&gt;We present results of detail geochemical study of 18&amp;#8211;12 Ma volcanic rocks from the Kamar-Stanovoy Zone of Hot Transtension (KSZHT), located in the central Baikal Rift System (BRS), and older pseudotachylytes from the Main Sayan Fault (MSF). These rocks designate geochemically distinguished from the OIB sources that are referred to the Slyudyanka zone of paleocollision occurred between the Khamardaban terrane and Siberian paleocontinent about 488 Ma ago. We define crustal and mantle signatures (with and without garnet, respectively) for the KSZHT volcanic rocks and crustal ones for the MSF basic pseudotachylytes. The signatures are indicative for tracing complementary relations between layers of the crust&amp;#8211;mantle transition (CMT). We infer that the KSZHT volcanic activities accompanied rifting of a paleocontinental margin but got quiescent after a structural separation of the South Baikal Basin from the Tunka Valley, when the former had been sufficiently extended and subsided in contrast to the latter, which had been notably compressed and uplifted. From geological evidence and a detail seismic tomography model, we suggest that the KSZHT crust&amp;#8211;mantle magmatic processes were due to delamination of a thickened root part of the South Baikal Orogen that preceded rifting in the South Baikal Basin area in the Late Cretaceous and Paleogene. Volcanic rocks of the past 17 Ma from the southwestern BRS denoted similar CMT sources and delamination processes beneath the East Hangay orogen and adjacent Orkhon-Selenga saddle. In the central and southwestern BRS, the CMT sources marked mutually overlapping deformational fields related to Indo-Asian convergence and pool-to-axis forces of the Japan-Baikal geodynamic corridor.&lt;/p&gt;&lt;p&gt;This work is supported by the RSF grant 18-77-10027.&lt;/p&gt;

Petrology of Basanitic Lavas of the Daur–Hentiyn Range (P–T Conditions of Formation, Crystallization Sequence, and Sources of Material)

—We performed a comprehensive study of basanites from the Daur–Hentiyn Range and present the first data on their Sr and Nd isotope and mineral compositions (electron probe microanalysis). The study has shown that the basanites are chemically similar to the volcanic rocks of the South Baikal volcanic area (SBVA) and are slightly different from oceanic island basalts in higher contents of Ba, Th, La, and Sr. The crystallization temperatures and pressures for the Fo0.85 olivine–melt equilibrium have been estimated, 1186–1137 ºC, 1.09–1.06 GPa, and the sequence of mineral crystallization has been established. The obtained Sr and Nd isotope data indicate that the basanitic magmas were generated from material with PREMA and EMI isotope parameters.

The Relationship between Powerful Geodynamic Impacts and an Increase in the Mercury Content of the Water of the Angara River Source (Baikal Rift Zone)

—The results of Hg content determination in the water of the Angara River source are considered in relationship with the seismic processes proceeding at different levels of the lithosphere in the Baikal Rift Zone (BRZ), the geodynamic rejuvenation of the South Baikal rifting attractor structure (RAS), and the time distribution of M ≥ 7 earthquakes which occurred at a significant distance from the water sampling station. The correlation coefficients calculated between the pairs Hg content–earthquake numbers n and Hg–logarithm of summary seismic energy lgΣES are most often low, thus indicating the absence of a statistically meaningful relationship between the remote seismic process and the dynamics of mercury release. However, the correlation coefficients in the vicinity of the Angara River source are high, thus proving the relationship of the mercury release with the deformation of this territory. The statistical validity of the «deformation–mercury release» cause-and-effect relationship is verified by the fact that strong geodynamic impacts precede all meaningful Hg release maxima. In the period 1997–1998, the South Baikal RAS produced the highest impact, being in the phase of the maximum geodynamic activity. The combined impact of the RAS and the South Baikal earthquake of 1999 resulted in a series of the maximum mercury contents within 1999–2000. The subsequent gradual relaxation of the RAS activity led to a reduction in the average annual Hg content. Remote M ≥ 7 earthquakes and close strong earthquakes of the BRZ are responsible for the significant Hg release maxima. The predicted trend of the average annual Hg contents is their considerable increase in the fields of fluid discharge of faults under the powerful geodynamic impact of the RAS or strong earthquake. We assume that in the study lithosphere area, the powerful geodynamic impact caused an opening of fault zones leading to decompression with boiling and degassing of mercury and its rapid rise to the surface.