Manifestation of the Late Famennian Dasberg Event in the shelf-batial transition (Pai-Khoi sequences)

Research subject. Regional manifestations of the Dasberg eustatic event in the shelf and bathyal Pai-Khoi successions. The event appears in the Lower-Middle expansa zones interval (Upper Devonian, Famennian).Aim. To evaluate the manifestations of the event in the realm of transition from the shallow-water shoal succession of the Pai-Khoi carbonate parautokhtone towards the deep-water (bathyal) successions of the Kara shale allokhtone.Materials and methods. A number of successions comprising different facies and located in different parts of Pai-Khoi were studied: the Silova-Yakha River section and Tal’beyshor Creek section (south-western Pai-Khoi), the Lymbad’yakha section and the Peschanaya River section (northern Pai-Khoi). The interpretation of facies and the reconstruction of transgression-regression couplets were conducted based on the previously developed models of shoal and bathyal sedimentation. The stratigraphic framework comprised data on conodonts, transgression acmes, and carbonate carbon isotopic record.Results. The Pai-Khoi successions comprising Lower–Middle expansa zones demonstrate four transgression-regression cycles. The transgression acme of the third cycle marks the Dasberg eustatic event. The absence of anoxia is characteristic of this event in the region under consideration. The carbonate carbon isotope record of the Silova-Yakha River section shows a structure similar to that of North American successions. Variations in δ13Cкарб were likely to be caused by climate changes and perturbations of the global oceanic circulation.Conclusions. The stratigraphic interval comprising Lower–Middle expansa or Lower–Upper expansa (expansa s. l.) zones is detected clearly in different facies. A more detailed subdivision and correlation in the region under consideration is possible on the basis of evaluating manifestations of the Dasberg eustatic event: a characteristic eustatic succession and variations of the carbonate carbon isotopic composition.

Ecological Parameters of Water Bodies in the Northern Part of the Upper Volga Region with River Flow Regulations

The regulation of river flow in the Volga basin has caused irreversible changes to aquatic ecosystems. The transformation of the Volga into a cascade of hydraulic structures with a non-flow regime has resulted in a decrease in depth and flow, and an increase in the temperature and concentration of chemical elements, which has induced the process of eutrophication. The change in the species diversity of aquatic organisms under conditions of intense eutrophication was studied on models of water bodies from the Volga basin; the Kostroma section of the Gorky reservoir (Kostroma spill and the middle river section), and lakes Galichskoe and Chukhlomskoe were studied. Rheophilic biocenosis was replaced by a limnophilic one, the migration paths of fish were disrupted, and population characteristics were changed. In accordance with environmental conditions, the level of primary production and the calculated Carlson trophic index (TSI) and Broth-proposed index (ITS) (1987), the water bodies of the northern part of the upper Volga region are classified as follows: the middle river section of the Gorky reservoir is mesotrophic-eutrophic (TSI = 55.2, ITS = 16.2); the Kostroma spill is eutrophic with a tendency to hypertrophy (TSI = 67.4, ITS = 6.8); Lake Galichskoe is eutrophic with a tendency to dystrophy (TSI = 63.2, ITS = 8.4), and Lake Chukhlomskoe is hypertrophic with a tendency to dystrophy (TSI = 77.4, ITS = 8.0). In addition, frequent fluctuations in water level, reaching 1 m, have had an adverse effect on inhabitants of the littoral zone including the spawning fish, which may lead to disappearance of some of the region’s most sensitive species.

Role of water bodies in the structure of open public spaces of cities (Chermyanka river)

Most of the cities standing on rivers are currently faced with the problem of the formation of near-water depressed spaces. The paper presents the results of a study of the depressive territory of the Chermyanka River section (Moscow), in which the authors took part. Based on the results of the reconnaissance survey and sociological research, the main problems of the study area were identified. Based on the analysis of successful foreign and domestic projects for the revitalization of depressed spaces, ways of solving these problems are proposed. The paper describes an option of the reorganization of the depressed territory under consideration, developed by the authors. The choice of zoning the territory of the river into green and open public spaces has been substantiated. The functional content of public spaces and communications is described, allowing them to be combined into an integral recreational complex. The new public space will allow the Bibirevo and Otradnoye districts to be linked by a pedestrian route and will provide free movement between the banks of the river.

Paleomagnetic Studies of the Late Miocene Mangapoike River Section, Northern Hawke's Bay, New Zealand

<p>The Mangapoike River section (38.9 degrees S, 177.6 degrees E), on the eastern limb of the Wairoa Syncline, northern Hawke's Bay, is a thick (> 4000 m) and well exposed sequence of Waiauan to Waipipian sediments in which foraminiferal and radiolarian biostratigraphy and silicic tuff lithostratigraphy are well known. An Early Pliocene magnetostratigraphy has been determined by Kennett and Watkins (1974). The present study extends the magnetostratigraphy to the Middle -Late Miocene, and establishes a late Miocene to Early Pliocene 3000 m magnetostratigraphic reference column for New Zealand. The only identifiable remanence carrying magnetic mineral in the Mangapoike sediments is titanomagnetite. Its chemistry does not vary with grain size. Oxidation of the titanomagnetite is deuteric, and thus pre-depositional. Fluctuations of titanomagnetite concentration between 10-3 to 10-4 wt percent are the main influence on the variation of NRM intensity. Viscous magnetisations characterised by both the alignment of NRM directions in a general present day field direction and remanence decay and aquisition over laboratory time were recognised in 85 percent of the 1204 paleomagnetic specimens. Secondary magnetisations were removed by thermal demagnetisation at temperatures varying between 200 degrees C and 320 degrees C. AF demagnetisation was not effective in removing viscous magnetisations, even at peak alternating fields of 35 mT, since the coercivities of the primary and secondary magnetisations overlap completely. The random relationship between the degree of bioturbation and in-site dispersion at individual sites indicates the magnetisation is acquired after bioturbation, and thus is a post-depositional detrital magnetisation. The time lag between deposition and acquisition of the magnetisation is approximately 1000 yrs. Six normal (MN1 - MN6) and seven reversed (MR1 - MR7) polarity magnetozones are identified within the late Miocene at Mangapoike. Only one normal magnetozone (MN6) is recognised in the stratigraphic interval equivalent to that from which Kennett and Watkins (1974) reported two normal zones (C1 and C2). MN6 is correlated to C2. C1 is inferred to be an uncleaned normal overprint. The magnetozones are correlated to Chrons 11 to 4, which implies an average sedimentation rate of 64 cm/1000 yrs. The previously known Miocene - Pliocene 3 degrees angular unconformity at Mangapoike (Hornibrook 1977) represents the period from 6.3 Ma to at least 5.41 Ma. A previously unrecognised unconformity from at least 6.86 to at least 6.42 Ma is postulated, based on the preferred magnetostratigraphic interpretation. The presence of the unconformity is supported by radiolarian and benthic foraminiferal biostratigraphy. Three distinct lithological events at Mangapoike, based both on the synchroneity with deep-sea benthic delta 18O records and unconformities of the Vail-curve, are inferred to result from glacioeustatism. At Mangapoike, the Waiauan - Tongaporutuan boundary, as defined by the incoming of Bolivinita cf pohana, has a magnetostratigraphic age of 10.3 Ma. Both the LAD of Loxostomum truncatum and the FAD of Bolivinita cf pohana are less than 42,000 yrs. younger than the late Waiauan glacioeustatic event. The Waiauan - Tongaporutuan boundary is thus postulated to result from glacioeustatism. Glacioeustatism may also explain the excellent age correlation between the base of the Tongaporutuan and the base of the Tortonian stratotype. Correlation of the late Miocene and early Pliocene magnetostratigraphies and biostratigraphies of on-shore New Zealand with either of the magnetostratigraphic interpretations of DSDP Site 594 results in an unacceptably high diachroneity of some planktic taxa of 1.8 Ma over 3.6 degrees of latitude. Of four possiblities to resolve the anomaly, incorrect magnetostratigraphic correlations at Site 594 is the most likely. The previously determined age of 6.2 Ma for the LAD of Globoquadrina dehiscens in New Zealand is erroneous. A magnetostratigraphic age for the LAD of G. dehiscens at Mangapoike is 9.2 Ma. This age is not an extinction date for the taxon throughout New Zealand, and the LAD may well be erratic and diachronous within New Zealand. The Wairoa Syncline, a forearc basin within the Hikurangi margin, has a rotation rate as determined from declination directions, of 7-8 degrees /Ma for the last 5 Ma. Of this less than 1.5 degrees /Ma is due to apparent polar wander of the Australian plate. Extrapolation of this rate towards the present is consistent with a present day rotation rate of 7 degrees /Ma derived from strain analysis of geodetic data. Prior to 10 Ma the rate of tectonic rotation is poorly constrained and may vary between 3 degrees /Ma and 0 degrees /Ma. The change in the rate of rotation of the Wairoa Syncline around 5 Ma is probably related to a marked change in regional tectonic regime involving opening and spreading to the north of New Zealand and compression and shortening to the south.</p>

Paleomagnetic Studies of the Late Miocene Mangapoike River Section, Northern Hawke's Bay, New Zealand

<p>The Mangapoike River section (38.9 degrees S, 177.6 degrees E), on the eastern limb of the Wairoa Syncline, northern Hawke's Bay, is a thick (> 4000 m) and well exposed sequence of Waiauan to Waipipian sediments in which foraminiferal and radiolarian biostratigraphy and silicic tuff lithostratigraphy are well known. An Early Pliocene magnetostratigraphy has been determined by Kennett and Watkins (1974). The present study extends the magnetostratigraphy to the Middle -Late Miocene, and establishes a late Miocene to Early Pliocene 3000 m magnetostratigraphic reference column for New Zealand. The only identifiable remanence carrying magnetic mineral in the Mangapoike sediments is titanomagnetite. Its chemistry does not vary with grain size. Oxidation of the titanomagnetite is deuteric, and thus pre-depositional. Fluctuations of titanomagnetite concentration between 10-3 to 10-4 wt percent are the main influence on the variation of NRM intensity. Viscous magnetisations characterised by both the alignment of NRM directions in a general present day field direction and remanence decay and aquisition over laboratory time were recognised in 85 percent of the 1204 paleomagnetic specimens. Secondary magnetisations were removed by thermal demagnetisation at temperatures varying between 200 degrees C and 320 degrees C. AF demagnetisation was not effective in removing viscous magnetisations, even at peak alternating fields of 35 mT, since the coercivities of the primary and secondary magnetisations overlap completely. The random relationship between the degree of bioturbation and in-site dispersion at individual sites indicates the magnetisation is acquired after bioturbation, and thus is a post-depositional detrital magnetisation. The time lag between deposition and acquisition of the magnetisation is approximately 1000 yrs. Six normal (MN1 - MN6) and seven reversed (MR1 - MR7) polarity magnetozones are identified within the late Miocene at Mangapoike. Only one normal magnetozone (MN6) is recognised in the stratigraphic interval equivalent to that from which Kennett and Watkins (1974) reported two normal zones (C1 and C2). MN6 is correlated to C2. C1 is inferred to be an uncleaned normal overprint. The magnetozones are correlated to Chrons 11 to 4, which implies an average sedimentation rate of 64 cm/1000 yrs. The previously known Miocene - Pliocene 3 degrees angular unconformity at Mangapoike (Hornibrook 1977) represents the period from 6.3 Ma to at least 5.41 Ma. A previously unrecognised unconformity from at least 6.86 to at least 6.42 Ma is postulated, based on the preferred magnetostratigraphic interpretation. The presence of the unconformity is supported by radiolarian and benthic foraminiferal biostratigraphy. Three distinct lithological events at Mangapoike, based both on the synchroneity with deep-sea benthic delta 18O records and unconformities of the Vail-curve, are inferred to result from glacioeustatism. At Mangapoike, the Waiauan - Tongaporutuan boundary, as defined by the incoming of Bolivinita cf pohana, has a magnetostratigraphic age of 10.3 Ma. Both the LAD of Loxostomum truncatum and the FAD of Bolivinita cf pohana are less than 42,000 yrs. younger than the late Waiauan glacioeustatic event. The Waiauan - Tongaporutuan boundary is thus postulated to result from glacioeustatism. Glacioeustatism may also explain the excellent age correlation between the base of the Tongaporutuan and the base of the Tortonian stratotype. Correlation of the late Miocene and early Pliocene magnetostratigraphies and biostratigraphies of on-shore New Zealand with either of the magnetostratigraphic interpretations of DSDP Site 594 results in an unacceptably high diachroneity of some planktic taxa of 1.8 Ma over 3.6 degrees of latitude. Of four possiblities to resolve the anomaly, incorrect magnetostratigraphic correlations at Site 594 is the most likely. The previously determined age of 6.2 Ma for the LAD of Globoquadrina dehiscens in New Zealand is erroneous. A magnetostratigraphic age for the LAD of G. dehiscens at Mangapoike is 9.2 Ma. This age is not an extinction date for the taxon throughout New Zealand, and the LAD may well be erratic and diachronous within New Zealand. The Wairoa Syncline, a forearc basin within the Hikurangi margin, has a rotation rate as determined from declination directions, of 7-8 degrees /Ma for the last 5 Ma. Of this less than 1.5 degrees /Ma is due to apparent polar wander of the Australian plate. Extrapolation of this rate towards the present is consistent with a present day rotation rate of 7 degrees /Ma derived from strain analysis of geodetic data. Prior to 10 Ma the rate of tectonic rotation is poorly constrained and may vary between 3 degrees /Ma and 0 degrees /Ma. The change in the rate of rotation of the Wairoa Syncline around 5 Ma is probably related to a marked change in regional tectonic regime involving opening and spreading to the north of New Zealand and compression and shortening to the south.</p>

Studies and research on the phenomenon of hydrodynamic erosion in river beds

The phenomenon of hydrodynamic erosion affects the riverbeds in which sub-crossings of pipes or bridges are located. The depth of erosion is determined at a point in the riverbed by the use of specialized computational relationships. For some works located in the riverbed it is necessary to know the erosion depths on the perimeter of the flow section. The analysis models used to investigate the phenomenon of hydrodynamic erosion were: a - topographic model; b - calculation relations from the technical regulations; c - erosion simulation model on a river section. The obtained results were materialized by the evolution of the erosion depths on the considered river sector over an interval of about 5-15 years. The depth of erosion on the lower course of the Moldova River showed values from 0.75 m to 1.65 m on a research sector. The research results were capitalized on the design of the rehabilitation works of the constructions present in the riverbed.

Navigational Atlas of the Selenga River section within Mongolian People’s Republic, 1925

The article provides information on the manuscript atlas of the Selenga and Orkhon rivers within the Mongolian People’s Republic (MPR), compiled on the basis of data from 1924-1925. It was developed for the Selenga Technical Section of the Ministry of the River Fleet to guide navigation along the rivers of Mongolia. The shooting was carried out on a steam boat “Shilka”. The atlas is of interest for the dynamics of river channel processes in northern Mongolia. The materials provide information on where and how to carry out technical work to improve navigation. In addition to information on navigation, it provides economic and geographical information on the north of Mongolia in the 1920s.