Millennium scale environment changes of the Okhotsk Sea during last 80 kyr and their phase relationship with global climate changes     

Sergey Alexandrovich Gorbarenko  Evgenia L’vovich Goldberg  Michaele Kashgarian  Tat’yana Alekseevna Velivetskaya  Sergey Petrovich Zakharkov  Vladimir Stepanovich Pechnikov  Alexandr Anatol’evich Bosin  Olga Yur’evna Psheneva  Elena Diamilevna Ivanova 《Journal of Oceanography》2007,63(4):609-623

The paper presents the records of several paleoproductivity proxies (PP) (biogenic opal and Ba (Si_bio, Ba_bio), organic carbon (C_org) and carbonate Ca_carb, chlorin and benthic foraminifera abundance (BFA)) in sediments of the Okhotsk Sea for the last 80 kyr with a resolution of ∼100–300 years. The sediment age model was based on the AMS ¹⁴C data, records of benthic foraminifera δ¹⁸O, paleointensity of the Earth’s geomagnetic field and magnetic susceptibility. PP values demonstrate series of severe prolonged productivity drops in the Okhotsk Sea followed by a sharp increase during the last glaciation. On the basis of quantitative estimations of the paleoproductivity in the Okhotsk Sea during the cold MIS 2 and warm Holocene (Gorbarenko and Goldberg, 2005), it is suggested that the millennium scale relationship in productivity-climate changes of this basin was similar: an increase in the sea’s productivity was related with regional climate warming and vice-versa. The PP records of productivity/climate oscillations in the Okhotsk Sea during MIS 2–4 occurred contemporaneously with the North Atlantic cold Heinrich events (HE) and Greenland Dansgaard-Oyeshger interstadial (DOI). Observed successions of prolonged climate cooling events followed by rapid, abrupt warming are similar to climate and environmental oscillations in the N. Atlantic and Greenland, that confirms the millennium-scale climate changes synchronicities in the Northern Hemisphere including the far NW Pacific, the hydrology and climate conditions of which are close to those of the Okhotsk Sea. Synchronism of the N. Hemisphere severe cooling (including the Okhotsk Sea) with the Antarctic warming suggests that mechanisms of the “seesaw” effect (Blunier and Brook, 2001) in the low latitude heat redistribution between high latitudes of both hemispheres were more complicated than direct NADW formation forcing and encompasses the global atmospheric reorganization. Within the PP used a closer connection in the Okhotsk Sea millennium oscillations was observed for the C_org, BFA and chlorin; Ba_bio increases more closely to DOI. Si_bio variability does not show any evident correlation with productivity changes.  相似文献   

Kinetics of dissolution of mechanically comminuted rock-forming oxides and silicates—I. Deformation and dissolution of quartz under laboratory conditions     

Radomir Petrovich 《Geochimica et cosmochimica acta》1981,45(10):1665-1674

The extensive evidence on the properties of ground quartz such as grain morphology and adherence and subsurface structural damage shows a consistent pattern, interpretable in terms of the competing processes of fracture and of local plastic deformation.The well-documented pattern of dissolution of ground quartz in aqueous solutions is also consistent. At large undersaturations and constant other environmental variables, the apparent dissolution rate of ground quartz decreases exponentially with the increasing thickness of the equivalent dissolved disturbed layer, and the rate of release of adherent tiny fragments shows roughly the same dependence on the latter. At small undersaturations distribution of solubilities also needs to be considered.  相似文献   

A 450-ka long record of glaciation in Northern Mongolia based on studies at Lake Khubsugul: high-resolution reflection seismic data and grain-size variations in cored sediments     

Andrey Petrovich Fedotov  Michael A. Phedorin  Mark De Batist  Galina A. Ziborova  Alexsey Yu Kazansky  Michael Yu Semenov  Galina G. Matasova  Andrey V. Khabuev  Sergey A. Kugakolov  Sergey V. Rodyakin  Svetlana M. Krapivina  Tom Pouls 《Journal of Paleolimnology》2008,39(3):335-348

We use high-resolution reflection seismic data and detailed grain-size analysis of a drill core (KDP-01) from Lake Khubsugul (northern Mongolia) to provide an improved reconstruction of the glacial history of the area for the last 450 ka. Grain-size analysis of suspended sediment load in modern rivers draining into the lake and of moraine material from the northern part of the catchment shows that the silt fraction is transported to the central part of the lake mainly by river suspension, whereas the clay fraction is mainly transported by glacial meltwater during deglaciation. The changes in of the clay/silt ratio in Lake Khubsugul sediments correlates well with the standard global paleoclimate records: low clay/silt ratios indicate warm climates, while a high clay/silt ratio reflects glacial erosion and cold climates. Pulses of clay input into the lake occur at the final stages of glacial periods (i.e., glacial maxima and subsequent onsets of deglaciation). The periodicity in glacial clay input in Lake Khubsugul is in tune with global periods of deglaciation, but there are differences in the intensity of the deglacial events for MIS-12 and MIS-2. These differences are attributed to specific conditions in regional distribution of moisture during glaciation, glacial ice volumes, and solar insolation intensity at the onset of deglaciation. Deglaciation of the Khubsugul glaciers occurred in response to an increase in summer solar insolation above a threshold value of 490 W/m². Two types of deglaciation can be distinguished: (1) slow melting during several tens of 1,000 years during weak increases in summer insolation, and (2) short and fast melting during several thousands of years in response to strong increases in summer insolation. The maximum ice volume in the area of Lake Khubsugul during the past 450 ka occurred during the period of 373–350 ka BP (MIS 11a-10) and was caused by high levels of moisture in the region, whereas the MIS-2 and MIS-12 glacial periods were characterized by minima in ice volume, due to the strong aridity in the region.  相似文献   

On M-Theory     

Hermann Nicolai 《Journal of Astrophysics and Astronomy》1999,20(3-4):149-164

This contribution gives a personal view on recent attempts to find a unified framework for non-perturbative string theories, with special emphasis on the hidden symmetries of supergravity and their possible role in this endeavor. A reformulation ofd = 11 supergravity with enlarged tangent space symmetry SO(1, 2) × SO(16) is discussed from this perspective, as well as an ansatz to construct yet further versions with SO(1, 1) × SO(16)^∞ and possibly even SO(1, 1)₊ × ISO(16)^∞ tangent space symmetry. It is suggested that upon “third quantization”, dimensionally reduced maximal supergravity may have an equally important role to play in this unification as the dimensionally reduced maximally supersymmetricSU(∞) Yang Mills theory.  相似文献   

Groundwater quality and rural drinking-water supplies in the Republic of Moldova   总被引：1，自引：0，他引：1  

Ruslan Melian  Nicolai Myrlian  Alexander Gouriev  Constantin Moraru  Frank Radstake 《Hydrogeology Journal》1999,7(2):188-196

 This paper describes the results of a groundwater quality assessment conducted in two pilot areas, Balatina and Carpineni, in the Republic of Moldova. Shallow groundwater is the main source of drinking water in rural areas, but reliable data on its quality are currently insufficient for developing rural water-supply systems with standard designs. The main components of the study included a field sampling program (including pesticides), an evaluation of the reliability of existing drinking-water data, an analysis of land use and groundwater-pollution risks using GIS, and the formulation of recommendations to reduce risks for public health. Microbiological, nitrate, and selenium contamination are most serious in the villages. These contaminants should be given priority in addressing drinking-water aspects for rural water-supply development in the two pilot areas. Pollution occurs mainly due to poor sanitary conditions. In a few shallow wells, traces of selected pesticides were observed, but the effect of these levels of pesticides on public health is still unclear. Limited resources of shallow groundwater of good quality occur outside the villages. Additional pilot studies should be implemented to prove the technical and institutional feasibility of developing and protecting these resources. Received, September 1997 Revised, September 1998 Accepted, March 1999  相似文献   

Are There Differences in the Response of Natural Stand and Plantation Biomass to Changes in Temperature and Precipitation? A Case for Two-needled Pines in Eurasia     

USOLTSEV Vladimir Andreevich  SHOBAIRI Seyed Omid Reza  TSEPORDEY Ivan Stepanovich  AHRARI Amirhossein  ZHANG Meng  SHOAIB Ahmad Anees  CHASOVSKIKH Viktor Petrovich 《资源与生态学报(英文版)》2020,11(4):331-341

A comparative discussion of the advantages and disadvantages of natural stands and plantations, including in terms of their productivity and stability, began from the moment of the first forest plantings and continues to this day. In the context of the progressive replacement of natural forests by plantations due to deforestation, the question of how will change the carbon storage capacity of forest cover when replacing natural forests with artificial ones in a changing climate becomes extremely relevant. This article presents the first attempt to answer this question at the transcontinental level on a special case for two-needled pine trees (subgenus Pinus L.). The research was carried out using the database compiled by the authors on the single-tree biomass structure of forest-forming species of Eurasia, in particular, data of 1880 and 1967 of natural and plantation trees, respectively. Multi-factor regression models are calculated after combining the matrix of initial data on the structure of tree biomass with the mean January temperature and mean annual precipitation, and their adequacy indices allow us to consider them reproducible. It is found that the aboveground and stem biomass of equal-sized and equal-aged natural and plantation trees increases as the January temperature and precipitation rise. This pattern is only partially valid for the branches biomass, and it has a specific character for the foliage one. The biomass of all components of plantation trees is higher than that of natural trees, but the percent of this excess varies among different components and depends on the level of January temperatures, but does not depend at all on the level of annual precipitation. A number of uncertainties that arose during the modeling process, as well as the preliminary nature of the obtained regularities, are noted.  相似文献   

Evaluation of deep crustal earthquakes in northern Germany – Possible tectonic causes     

Christian Brandes  Thomas Plenefisch  David C. Tanner  Nicolai Gestermann  Holger Steffen 《地学学报》2019,31(2):83-93

We present new evidence for seven deep crustal, intraplate earthquakes in northern Germany, a region regarded as an area of low seismicity. From 2000 to 2018, seven earthquakes with magnitudes of M_L 1.3–3.1, were detected at depths of 17.0–31.4 km. By placing the earthquake hypocentres in a geological three‐dimensional model, we can correlate two of the earthquakes with the Thor Suture, a major fault zone in this area. Five of the earthquakes group in the lower crust near the Moho, which implies that parts of the lower crust and the crust/mantle boundary in northern Germany act as a structural discontinuity on which deformation localizes. Numerical simulation implies that stress changes due to glacial isostatic adjustment most likely triggered these deep crustal earthquakes.  相似文献   

Reconnaissance survey of the Duolun ring structure in Inner Mongolia: Not an impact structure          下载免费PDF全文

Xiaoming Xu  Thomas Kenkmann  Zhiyong Xiao  Sebastian Sturm  Nicolai Metzger  Yu Yang  Daniela Weimer  Hannes Krietsch  Meng‐Hua Zhu 《Meteoritics & planetary science》2017,52(9):1822-1842

The Duolun basin, which is located in Inner Mongolia, China, has been proposed to be an impact structure with an apparent rim diameter of about 70, or even 170 km. The designation as an impact structure was based on its nearly circular topography, consisting of an annular moat that surrounds an inner hummocky region, and the widespread occurrences of various igneous rocks, polymict breccias, and deformed crustal rocks. Critical shock metamorphic evidence is not available to support the impact hypothesis. We conducted two independent reconnaissance field surveys to this area and studied the lithology both within and outside of the ring structure. We collected samples from all lithologies that might contain evidence of shock metamorphism as suggested by their locations, especially those sharing similar appearances with impact breccias, suevites, impact melt rocks, and shatter cones. Field investigation, together with thin‐section examination, discovered that the suspected impact melt rocks are actually Early Cretaceous and Late Jurassic lava flows and pyroclastic deposits of rhyolitic to trachytic compositions, and the interpreted impact glass is typical volcanic glass. Petrographic analyses of all the samples reveal no indications for shock metamorphic overprint. All these lines of evidence suggest that the Duolun basin was not formed through impact cratering. The structural deformation and spatial distribution pattern of the igneous rocks suggest that the Duolun basin is most likely a Jurassic–Cretaceous complex rhyolite caldera system that has been partly filled with sediments forming an annular basin, followed by resurgent doming of the central area.  相似文献   

Stability issues of the continuous welded rail track on the concrete sleepers on the curves with radius R ≤ 300 m     

Victor Vasylevich Rybkin  Nicolai Petrovich Nastechik  Ruslan Volodymyrovych Marcul 《寒旱区科学》2013,5(5):0654-0658

This paper describes the economic and technological benefits of installing continuous welded rail(CWR) track on sharp(radius ≤ 300 m) railway curves. A new form of prestressed concrete sleepers developed by the V. Lazaryan Dnipropetrovsk National University of Railway Transport is shown to improve the lateral shift resistance of CWR track in sharp curves and the use of anchor sleepers on tangents is shown to make it possible to lower the fastening temperature of the CWR track in order to increase the rail lifespan.  相似文献   

Radiogenic trigger and driver for continental rifting and initial ocean spreading     

Yuriy Petrovich Maystrenko  Trond Slagstad 《地学学报》2020,32(2):159-165

Closure and opening of oceans on time‐scales of a few hundred million years is a fundamental tectonic process on Earth, typically referred to as a “Wilson cycle”. Subduction of oceanic and continental crust leading up to and during continent–continent collision can refertilize and enrich the orogenic continental lithospheric mantle in heat‐producing elements. The resulting thermal anomaly weakens the lithosphere and, along with structural weaknesses (e.g. sutures), make this orogenic lithosphere more prone to rifting given an extensional stress field. Thermal modelling shows that anomalously hot lithosphere can focus asthenospheric upwellings over time‐scales of a few hundred million years. Processes related to closure of oceans thus provide a mechanism for later localization of rifting and an extensional driving force.  相似文献