New Evidence on the Relief of the Southern Underwater Slope in the South Baikal Basin

A high-resolution bathymetric survey of the entire underwater slope in South Baikal was carried out for the first time by means of the multibeam echosounder. New elements were revealed in the underwater relief of the southern slope of the basin from the Kultuchnaya river to the Mysovka river, and a relevant regionalization was carried out into three areas according to the presence of ancient landforms and the intensity of the processes of their reworking, with the boundaries along the delta-front and the river fan of the Utulik and Pereemnaya. We reconstructed the formation process of the modern relief of this area of the underwater slope and determined a dominant role of the underwater-erosion processes in the formation of the modern relief, with the tectonic movements served as the “trigger” for them. The study revealed a direct correlation between the reworking of the ancient geomorphological surfaces and the occurrence of separate large underwater elevations or group ridges (remnants), canyons and linear depressions. It is determined that the pivotal role in the appearance of the modern relief of the underwater slope in the second area of extensive plano-convex (in section) and fan-shaped (in plan) delta-fronts of large rivers and debris fans enveloping the remnants. The existence of a steep underwater slope from the mouth of the Pereemnaya to the mouth of the Bol’shaya Tel’naya and of two large benches, and also the proximity of the maximum depths of the southern basin at the foot of this slope are explained by a more intense step-like lowering of this part of the lake when compared with the western part of the basin. This also accounts for the absence of large remnants in this part of the slope. The area of occurrence of lacustrine-fluvial and lacustrine-delta deposits of the Tankhoi paleobasin within the southern basin of Baikal is reconstructed. Four new hydrate-bearing structures associated with these deposits and morphologically pronounced in the vertex parts of the remnants were discovered. The morphological exploration indicators of the presence of new accumulations of gas hydrates on the underwater slopes of Baikal have been expanded.     

Chemical composition of snow in the water area of Lake Baikal and on the adjacent territory

It is found that pollution of the territory from local sources of the zone of atmospheric influence spreads over several tens of kilometers along the prevailing wind direction, and in the central zone it is replaced by regional pollution. Snow pollution in the water area of Lake Baikal was recorded near coastal settlements and in the mouth of the Selenga river. It is established that the southern hollow of Baikal holds the lead in the input of NO₂, NO₃, NH₄, PO₄, F, Al, Na, Ba, Mo, Mn, Pb, Cu, Zn, Sr, Hg and oil products to the lake’s water area in spite of the fact that it is twice as small as the northern hollow. The northern hollow receives much larger amounts of SO₄, H₂CO₃, Cl, Ca, Mg and K than the northern hollow, and much larger amounts of Be, V, Cr and Co than the middle hollow, which is associated with the operation of coastal enterprises, boilers, thermoelectric plants, stove heating, automobile exhaust emissions, and with the natural transport of dust in snow-deficient areas of the middle hollow. It is determined that that last five years saw a slight increase in regional pollution for separate components. It is shown that in the late 1990s and in the early 2000s, pollution decreased twice, which was due to the setback in industrial production.     

Magnetostratigraphic investigations of the Middle Triassic Badong Formation in South China

Magnetostratigraphic sampling of the Middle Triassic Badong Formation in South China was conducted at three sections. A dual-polarity characteristic remanent magnetization (ChRM) resolved from most samples by thermal demagnetization is shown to have been acquired prior to folding. The primary nature of the ChRM is corroborated by the discovery of the same magnetic polarity at equivalent stratigraphic levels in more than one section. The relative sample VGP (virtual geomagnetic pole) latitudes define nine magnetozones for the three major constituent members of the formation. Comparison with the Mid-Triassic magnetic polarity sequence observed from the western Tethyan region appears to indicate that the bulk of the Badong Formation is Anisian in age and that Ladinian sediments are largely missing. This agrees with palaeontological and stratigraphic evidence in the region and supports the view that Ladinian regression is a major event in the geological evolution of South China, which may signal the onset of amalgamation of the Yangtze Block (YB) with the North China Block (NCB).     

Microbes in the area of the South Shetland Islands

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Flood Hazard on the Rivers of the Baikal Region

A comprehensive characterization of the flood hazard on the rivers of the Baikal region is presented, which was obtained by investigating the streams within the basins of the Angara, Upper Lena (with the Vitim and Olekma), Lower Tunguska (headwaters), Upper Amur and Lake Baikal (including the entire Selenga basin). The main flood indicators for the period 1985–2017 are estimated: the genesis, recurrence, duration, flooded area and the force of impact. The influence of changes in the river runoff characteristics on the flood risk is shown by results of correlation analysis and analysis of integro-differential curves. An assessment is made of the changes in the flood frequency at gauging stations during the period of pronounced climatic changes (from 1981 to 2014), compared with the earlier period. The flood hazard within the spatial context for municipalities in the rank of administrative districts is determined on the basis of the dual (socio-economic and natural) nature of floods. It has been confirmed that the most dangerous in the Baikal region are rainfall floods in the southern areas of Irkutsk oblast, the Republic of Buryatia and Zabaikalskii krai. They have the highest frequency, and the largest flooding areas and force of impact and are characterized by the greatest damage and by the largest number of victims and evacuated people. At the same time, the frequency of floods at gauging stations in recent years has decreased compared to the earlier period against the background of the observed low-water period, which is most pronounced on the rivers of South Baikal and in the Selenga river basin.     

Thermoluminescence chronology of late quaternary deposition on the riverine plain of South‐Eastern Australia

Thermoluminescence (TL) dating of surficial deposits of the Riverine Plain of south‐eastern Australia has revealed a record of fluvial, aeolian and lacustrine deposition during the last 100,000 years (100Ka). At the end of the last interglacial the Plain was networked by low sinuosity, bedload‐dominated prior streams which declined in activity after about 85Ka. A subsequent phase of prior stream activity in the northern Murrumbidgee region dates at between 50 and 40Ka and corresponds with a period of high lake levels in southern Australia. Local tectonism on the southern part of the plain confuses an interpretation of riverine response to changing Pleistocene climate. TL dates show that drainage diversion in response to tectonic movement along the Cadell Fault near Echuca began as early as 60Ka but that the damming of the Goulburn River to produce Lake Kanyapella did not occur until about 30Ka. Hydrologic changes on the Riverine Plain correlate broadly with those documented elsewhere in Australia, notably in the Lake Eyre Basin and numerous inland playa systems.     

Ethno-recreational potential of the Baikal region

An overview of ethno-recreational resources is presented, and a preliminary analysis is made of the potential for ethnographic tourism development in the Baikal region. This study is built upon the contemporary views concerning traditional culture and lifestyle of indigenous peoples living on the region’s territory; the focus is on searching for scientifically grounded approaches to conservation of ethno-cultural diversity under formation conditions for the international recreational space.     

Historical-geographical mapping of the Baikal region

The structure of the block of retrospective maps of ecological contents has been developed for the digital Atlas of sustainable development of the Baikal region. Presented are the methods for reconciliation and integration of different-time interdisciplinary geographical information, originating from different archival sources, into a unified cartographic system.     

Small hollows in the Baikal Rift Zone

Large grabens, or rift valleys, are of the utmost significance in the neotectonic structure of the Baikal Rift Zone. It is also the home for numerous small hollows which are distinguished by their morphological diversity, structural positions and special features of neogeodynamics. The distribution and types of small hollows are considered, and their structural-morphological classification is suggested.     

Influence of climate fluctuation on clay formation in the Baikal drainage basin

Sedimentary cores BDP 96 and 98 and VER 96-2 St. 3 from Academician Ridge in Lake Baikal were investigated to investigate the effect of climatic fluctuations on rock weathering and clay formation in the Baikal drainage basin. Illite, smectite, vermiculite, and kaolinite were identified as the major clay minerals in the sediments by X-ray diffraction analysis. Biotite in gravels in alluvial soils of the Baikal drainage area weathers through illite to vermiculite, smectite, and finally to kaolinite. To investigate the relationship between weathering and climate, we measured the clay content and the concentration of biogenic silica in the sediments. High surface productivity (increased biogenic silica) and high chemical weathering (decreased clay content) occurred simultaneously, showing that crustal weathering and soil formation were enhanced under warm climatic conditions.Clay formation was enhanced in the watershed from the Late Miocene to the Middle Pliocene, and mechanical weathering of rocks increased during glacial intervals after the climate began to cool in Late Pliocene time. This change in the weathering mode in the watershed reduced the nutrient flux and aquatic productivity of Lake Baikal.     

The natural-climatic events on the coast of Middle Baikal in the Early Holocene

Presented are the results from pedolithological investigations and reconstructions of the naturalclimatic events in the Early Holocene (radiocarbon age 10.3?8 ka; calendar age 11.7?8.8 ka) on the coast of Middle Baikal, based on data obtained by studying the structure, composition and properties of subaerial deposits and soils in terrestrial sections. A study was made of the numerous soil profiles and sections of geoarchaeological sites. The investigation revealed common features in the layered structure of the Early-Holocene portion of the terrestrial sections and evidence of climate warming represented by buried soils, signals of a cooling in the form of cryogenic fissures, and signals of drying in the form of aeolian drifts and evidence of deflation. It is shown that the Early Holocene was the time of cardinal changes in the nature of subaerial sedimentation (calcareous deposits were replaced by noncalcareous deposits) and the pedogenesis. Considerable cold storage from inherited permafrost and humidification of soils and earth materials with moisture from the thawing of permafrost were responsible for the specific character of soil formation, and for the spread of forest vegetation under a rather low atmospheric humidity. The phases of climate warming were accompanied by an intensification of soil formation with the production of soils of two types: early boreal, and boreal. Deluvial, colluvial and sometimes (in Priol’khonie) aeolian deposits accumulated during the cooling phases (Late Preboreal and Late Boreal). Small cryogenic fissures were generated. The issues of man’s adaptation to the cardinally changed natural conditions at the turn of the Pleistocene and Holocene and over the course of the Early Holocene are associated with the problem of Baikal’s water level and human settlement on its shores. The Lake Baikal stage at the end of the Late Neopleistocene was lower than at present; during the Early Holocene it was rising to reach at the late-boreal period the present-day level (or even exceeded it). The rises of Baikal’s stage at the Mid- and Late-Holocene period were causing scouring and destruction of the Early-Holocene sites that were located at lower elevations.     

Tendencies of long-term changes in water quality of water bodies in the South of Russia

Based on analyzing long-term (1968–2010) national monitoring data from Rosgidromet and other agencies as well as on research results for the Lower-Don and Kuban’ river basins, we identified observation posts on water bodies with a stably high pollution level and gave a characterization of the spatiotemporal tendencies of its changes. Long-term changes in water quality are exemplified by an alternation of periods of increasing and declining pollution; its level showed a decrease from the period 1980–1990 to the end of the last decade.     

The influence of deep convection on aeration of the bottom zone in Baikal

We investigated the influence of deep forced temperature convection on aeration of the bottom water layer in the pelagic zone of Baikal. Temperature T (± 0.002°C) and oxygen O₂ concentration (± 0.01 mg/L) were measured by using the SBE-25 probe with the SBE-43 oxygen sensor in May-July 2006?2007 and 2009?2013. Oxygen input into the bottom layer with cold intrusions was determined for 79 cases. The study revealed a quantitative correlation between the heat deficit and the rise in oxygen content in the bottom layer during cold intrusions. This correlation was used to reconstruct the values of intrusion aeration of the bottom layer during 1993?2005. It is ascertained that the intrusion-caused 2006?2013-average oxygen input into Baikal’s bottom layer is virtually close to the annual oxygen demand for oxidation processes in the water column and bottom sediments. In the southern and middle parts of Baikal, intrusion-caused input of oxygen corresponds to a higher rate of its demand (4.5?4.6x10^-4 mg/L per day). A slight increase in oxygen concentration was detected in the bottom layer of the South and Middle Baikal and a slight decrease in the bottom layer of North Baikal during 1993?2013.     

Tardigrada from the Husvik area, South Georgia, sub-Antarctic

Eleven species of tardigrades in South Georgia, of which two are new to science, were found in samples collected at fifteen localities. The highest number of species was found in moss from a scree field. Twenty species of tardigrades are presently known from South Georgia, but the island remains insufficiently investigated. The species composition is similar to that of southern South America. The high number of cosmopolitan species makes the geographical distribution pattern of the South Georgian tardigrades more similar to that of macrolichens than to that of insects and vascular plants.     

The Potential for Mixed Methods: Results from the Field in Urban South Africa

With the “cultural turn” in geography, scholars have become more focused on the politics of representation, politics of fieldwork, and politics of the research setting. In human geography, this epistemological shift has been accompanied by a methodological move toward intensive methods at the expense of extensive methods. In this article, I suggest that mixed methods that utilize the strengths of both intensive and extensive methods can offset the weaknesses of each method. Moreover, results from the field suggest that the combination of intensive and extensive methods could produce unique insights only possible from a mixed method approach.     

System approach to nature management in the Baikal region

The theoretical and practical aspects of sustainable development using the system approach are considered. An analysis is made of a number of major economic projects that were implemented in the Baikal region.     

Traditional life support methods of the Evenki in the Baikal region

The strategies and local varieties of life-support systems of the Evenki in the Baikal region in the pre-collectivization period are considered. The specific character and the role of traditional kinds of activity, and the resources of flexibility and sustainability of a traditional lifestyle are revealed. The culturalgeographical reconstruction of the economic adaptation of the Evenki, undertaken in this study having regard to the multivariate character of the natural and social environments, is compared with current problems of ethnic identity conservation.     

Siliceous microfossil distribution in the surficial sediments of Lake Baikal

Examination of surficial sediments at 16 stations shows minor, but consistent differences in the numbers and kinds of siliceous microfossils deposited in different regions of Lake Baikal. There is a general north-south decreasing trend in total microfossil abundance on a weight basis. Endemic plankton diatom species are the most abundant component of assemblages at all stations. Chrysophyte cysts are present at all stations, but most forms are more abundant at northern stations. Non-endemic plankton diatom species are most abundant at southern stations. Small numbers of benthic diatoms and sponge spicules are found in all samples. Although low numbers are present in offshore sediments, the benthic diatom flora is very diverse. Principal components analysis confirms primary north-south abundance trends and suggests further differentiation by station location and depth.