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Geomorfologiya i Paleogeografiya

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No 4 (2017)

Short communications

27-34 774
Abstract

Significant seismic events of the recent geological past are reflected in the relief of some areas of the Black Sea coast of the Caucasus region, of which the highest degree of seismotectonic transformation was characteristic to the area from Anapa to Novorossiysk. The current study was aimed at identification of palaeoseismodislocations and seismogravitational deformations, holding their morphological and morphometric analysis in order to determine the mechanism of formation, relative age, role in shaping the modern landscapes. It was found that seismogravitational structures have a complex composition and are distinctly expressed in relief. Many of them have common morphological features such as clear lines of landslide separation, typical hilly terrain morphology, occurrence of seismogravitational xenoliths and steep front benches.

Geomorphological analysis and interpretation of satellite images revealed two main types of seismogravitational structures. These structures have different ages and were formed in several stages, connected with the repeated display of seismic events. Most distinct are differences in the submarine topography of different age structures.

The modern exogenous processes are prone to the significant influence of the seismogenic relief transformation. The most active surface processes are erosion and rockfall processes occurring in unconsolidated seismogravitational sediments. Total scale of landscape changes indicates a high energy class of earthquakes and the probable location of their epicenters within or very close to the studied territory

35-49 545
Abstract
The Late Pleistocene-Holocene history of the caldera complex is characterized by large fluctuations of the lakes’ level, which were repeated probability at each eruption. This led to the formation of lake terraces, as well as the effect on the character of the development of intracaldera river network. Large amounts of volcanic material supplied on the calderas slopes are subsequently subjected to erosion with the formation of lahars and debris fans in the lakes area. Our research in 2016 showed that abrasion is the dominated process on the shores of Klyuchevoye and Shtyubel lakes, accumulation prevails only near river mouths where there is an active removal of debris from the caldera slopes. Four levels of terraces can be traced on the shores of the lakes, as a rule, they are erosion. Three lower terraces (3–5, 7–8, 12–15 m above lakes level) are usually correlated with extensive proluvial fans and at these places they may be accumulative. Formation of these levels occurred after the eruption of the young Shtyubel cone in 1907. Probably it was caused by partitioning of the Teplaya river source by explosive deposits and its subsequent gradual incision. Formation of the terrace level of 25–30 m height, which is fixed near edges of the youngest caldera, probably due to the accumulation and subsequent redeposition of pyroclastic of another Shtyubel cone explosion after last caldera eruption 1725 years BP. The presence of well-defined abrasion niches in strong andesites near the modern lake Klyuchevoye level shows that the level was stable for enough long time with fluctuations up to 1 m. The cemented well-sorted coastal sediments were found at the level of +1 m above the present shoreline of lakes in the valleys of some intracaldera streams. They were accumulated in the period between the formation of 4 and 3 terrace levels when hydrothermal activity in the lakes was higher than at present.
50-63 462
Abstract
New features of the structure of the Ulleung basin & trough (Southern Japan Sea) and its Neogene-Quaternary sediment cover were found by newly conducted single- & multichannel seismic profiling and drilling. Both landforms appeared in consequence of contrast tectonic movements and active volcanism in the Middle-Late Pleistocene and related subsidence of sea bottom by 2–2.5 km and inversion of Nakton marginal trough axis (Oki ridge). It was confirmed that sediment accumulation in the basin was governed by the Hwang Ho (Yellow River) delta, avandelta and submarine fan growing and filling the marginal Nacton basin by crossbedded sediments in the Neogene – Early Quaternary. The Ulleung basin formation was accompanied by sliding of the avandelta edge, which still continues at present and produces block landslides with tsunamigenic potential. Traces of gas- and may be oil present in fan deposits were detected in SCP sections (upper, contrast and low, semitransparent strata).
64-75 420
Abstract
The Lower Priamurye geoblock (the first-rank structural element of the Amur plate) was distinguished based on the morphostructural data. This geoblock is affected by neotectonic right-lateral strike-slip displacements along northeast-striking transregional faults. Arc faults have been formed inside the geoblock due to the imposed stresses. The faults are geomorphologically expressed as a conjugate system of river valleys bordering four blocks with rounded habitus that are composed of Mesozoic-Cenozoic magmatic and folded sedimentary rocks. A vortex-like arrangement of the faults inside the blocks, and the right-lateral strike-slip displacements consistent with the direction of deformations along the northeast striking faults, indicate the counter-clockwise rotation of these blocks.
76-90 587
Abstract

On the basis of the complex lithological and geomorphological zonation, the features of morphosystem characteristics were revealed. Map was produced of morphostructural provinces, paleogeographical zones of different age glaciations, which were divided into 19 areas.

The map legend contains specific geomorphological and lithological indicators of the regional morpholithosystems. As a result of the comparative analysis of the most important patterns of formation and trends of spatial variability characteristics the following issues were established: a) the provincial morphostructural and geological inheritance; b) paleogeographically preconditioned zonality of morphosculptures, types of sediment sequences and facial-genetic diversity; c) landscape and climate relations and regional particularities of exogenous processes in the relief transformation and sedimentation. The complex lithological-geomorphological zoning has high scientific and methodological value. The identified regional patterns and characteristics of morpholithosystems are relevant for reliable paleogeographic reconstruction and interregional correlations, as well as to assessment of the forecast and the state and prognosis of geo-environmental sustainability of the natural environment.

Articles

3-15 536
Abstract

Irreversible vertical deformation implies the systematic incision or sediment deposition within a considerable length of the river, in the course of which rise or lowering of river long profile and change of its general shape occur. Contemporary deformations occur in time intervals documented by historical materials and direct observations, that span several centuries, develop under the human influence or have a purely anthropogenic origin, although natural deformations due to tectonics and climate change play some role as well.

To analyze the dynamics of the riverbed vertical deformations process, published sources for several rivers over the World were used as well as authors’ own studies in a number of rivers: Ob river upstream and downstream of Novosibirsk reservoir, Kama river downstream of the Votkinsk dam, Selected reaches in rivers Tom’, Oka, Belaya Rivers with a large scale in-stream mines. Dam construction and creation of reservoirs as well as in-stream extraction of building materials most notably contribute to the development of vertical deformations.

Results show that both the process of incision downstream of dam and in sections with in-stream mines and the process of regressive accumulation upstream of the reservoirs are described by an exponential relationship reflecting the asymptotic nature of the lowering or rise of the riverbed. The relationship coefficients depend on the mobility of the channel. In the course of incision, riverbed becomes less movable, and its recovery may occur in other hydrological and geomorphological setting.

Ecological and Applied Geomorphology

16-26 777
Abstract
The article investigates the basic regular patterns reflecting the features and conditions of erosion processes treated as a consequence of human economic activities in river water catchment areas, the role in relief-formation and the influence on the state of natural-economic systems in the South Urals and Cis-Urals. One of the main factors predetermining the intensification of erosion processes is the transformation of slope runoff, including the increasing in its surface component and the destructive potential of water-flows under the deterioration of natural complexes in water catchment areas. It is shown that intensified development and trends for their growth are still observed in the regions (for example, in the Republics of Bashkortostan and Tatarstan) due to the increasing pasture load resulting from the growing livestock number in the private sector and due to the disappearance of economic incentives for avoiding cropland erosion, despite the overall decrease of anthropogenic impact. The article also provides analysis of the negative effect posed by the above-mentioned processes on the economic and environmental as well as the ecological conditions of minor river basins.


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ISSN 2949-1789 (Print)
ISSN 2949-1797 (Online)