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21.
Geological and seismic profiling data (more than 25000 km of seismic profiles and about 1000 sediment sampling stations) collected
during the last 30 yr by research vessels of the Shirshov Institute of Oceanology, Russian Academy of Sciences are summarized.
Seismic records are directly correlated with sediment cores. The distribution map (scale 1 : 500000) of Quaternary lithofacial
complexes corresponding to certain stages of the Baltic Sea evolution is compiled. The following four complexes are distinguished
(from the base to the top): (I) moraine, with maximum thicknesses 60 and 170 m in valleys and ridges respectively: (II) varved
clay of periglacial basins and from the Baltic Ice Lake (BIL), up to 25 m thick in depressions; (III) lacustrinemarine homogeneous
clay with a thickness up to 4–8 m in depressions; (IV) marine sediments (mud, aleurite, coarse-grained deposits) accumulated
in environments with intense bottom currents activity (thickness 2–4 m in the Gotland Basin, 4–6 m in the Gdansk Basin, and
10–20 m in fans and prodeltas). The Quaternary sequence is cut through by inherited valleys, where the thickest Holocene sediments
are noted. Today, these valleys serve as routes of sediment transport to slope bases and central parts of basins. Outblows
of deep gas (through faults and fractures) and diagenetic gas (from sediments) to the bottom surface also occur in the valleys.
Sedimentation rates are higher in the Gdansk Basin (up to 100–120 cm/ka). Thick sand, aleurite, and mud bodies are accumulated
here (about 15–20 m in the Visla River prodelta). The sedimentation rate is slower in the Gotland Basin (up to 50–60 cm/ka),
where thin (2–4 m) sections of more fine-grained mud occur 相似文献
22.
A catalog of X-ray sources as observed by the TTM/COMIS telescope onboard the Mir-Kvant observatory is presented. Brief information about the 67 sources detected at a confidence level higher than 4σ between 1988 and 1998 is provided. X-ray properties and characteristic spectra of different types of sources are briefly described. 相似文献
23.
We analyze observations of the burster 4U 1724-307 (1E 1724-3045) in the globular cluster Terzan 2 from 1971 until 2001. Uhuru, OSO-8, Einstein, and EXOSAT observations are used. In addition, we analyze data from the TTM telescope onboard the Mir/Kvant observatory and from the ASM and PCA instruments onboard the RXTE observatory. Based on PCA/RXTE scanning observations, we have mapped the sky in the Galactic-center region. The derived light curve of the burster 4U 1724-307 shows the source to be variable on a time scale of 30 years: over the first 20 years of observations (1970–1990), the source flux was approximately constant, while in the 1990s, it rose over ～5 years and declined over approximately the same period, approaching its original value. We discuss several scenarios to explain the behavior of the light curve, including the evolution of the mass outflow rate from the donor-star surface, the episodic appearance of a second source in the globular cluster, and gravitational microlensing. As one of the scenarios, we also consider the possibility that the passage of a third star affects the accretion rate in the binary 4U 1724-307. We show that if this event is responsible for the 10-year-long rise in the luminosity of the burster 4U 1724-307, then the size and period of this binary can be estimated. 相似文献
24.
E. V. Ivanova I. O. Murdmaa E. M. Emelyanov E. A. Seitkalieva E. P. Radionova G. N. Alekhina S. M. Sloistov 《Oceanology》2016,56(1):118-130
This paper presents reconstructions of ice sheet boundaries, lacustrine and marine paleobasins, as well as the connections of the Barents and Baltic seas with the North Atlantic from the Last Glacial Maximum to the Holocene. The reconstructions are based on original and published data obtained from the northern and western parts of the Barents Sea and Baltic depressions with account for the available regional schematic maps of deglaciation. The early deglaciation of the Scandinavian–Barents ice sheet culminated with the Bølling-Allerød interstadial (14.5–12.9 cal ka BP), which was characterized by a more vigorous Atlantic meridional overturning circulation (AMOC) and a corresponding increase in surface Atlantic water inflow into the Barents Sea through deep troughs. The Baltic Ice Lake (BIL) remained a dammed-up isolated basin during deglaciation from 16.0 to 11.7 cal ka BP. In the Younger Dryas (YD), the lake drained into the North Sea and was replaced by a brackish Yoldia Sea (YS) at the beginning of the Holocene (Preboreal, 11.7–10.7 cal ka BP), due to a limited connection between two basins through the Närke Strait. In the Barents Sea, the next increase in the Atlantic water influx into the deep basins corresponded to terminal YD and Preboreal events with a culmination in the Early Holocene. The Yoldia Sea became a lake again during the next stage, the Ancylus (~10.7–8.8 cal ka BP). Atlantic water inflow both into the Barents and Baltic seas varied during the Holocene, with a maximum contribution in the Early Holocene, when the Littorina Sea (LS, 8–4 cal ka BP) connection with the North Sea via the Danish Straits was formed to replace the Ancylus Lake. The recent, post-Littorina stage (PS, the last 4 cal ka) of the Baltic Sea evolution began in the Late Holocene. 相似文献
25.
The concentration distribution was studied for dissolved oxygen, phosphorus forms, and particulate matter in Curonian Bay of the Baltic Sea in poorly known consolidated ice cover conditions during the winter seasons of 2010, 2011, and 2013. The surface and near-bottom waters were sampled at 51 stations. The ice cover exerts no significant effect on the typical seasonal variation of all considered parameters in the basin. The concentrations of mineral and organic phosphorus in the bay appeared to be lower by factors of 2–4 compared to summer values. A two- to threefold decrease in the concentrations of organic phosphorus since 2010 to 2011 and then to 2013 was recorded in the bay, which resulted from a decrease in phosphorus production by phytoplankton. Despite water being isolated from air by ice, the absence of wave mixing, and the decrease in oxygen production owing to the seasonal winter decrease in the intensity photosynthetic processes, no oxygen deficiency was found in the basin. This is because oxygen supplied to the bay by river runoff and production by photosynthesis in the bay exceed the utilization for oxidation of organic matter resulting from low bioproductivity of the waters during winter. The winter decrease in the fraction of biogenic particulate matter is seen as a four- to sevenfold drop in its total concentration in the waters compared to summer seasons. The absence of wave roiling of bottom sediments also caused a decrease in the secondary supply of biogenic particulate matter from sediments into near-bottom waters. No negative trends of geoecological conditions in the bay were revealed by the studied parameters under consolidated ice cover conditions. 相似文献
26.
Pisman T. I. Erunova M. G. Botvich I. Yu. Emelyanov D. V. Kononova N. A. Bobrovsky A. V. Kryuchkov A. A. Shpedt A. A. Shevyrnogov A. P. 《Izvestiya Atmospheric and Oceanic Physics》2021,57(9):1188-1197
Izvestiya, Atmospheric and Oceanic Physics - This paper presents the results of a study assessing the degree of weed infestation of wheat crops. They are obtained using optical ground-based and... 相似文献
27.
I. O. Murdmaa G. H. Kazarina L. Beaufort E. V. Ivanova E. M. Emelyanov V. A. Kravtsov G. N. Alekhina V. E. Vasileva 《Lithology and Mineral Resources》2010,45(2):154-171
Core MD02-2508 retrieved from the plateau of the continental slope off Baja California recovered a 40-m-thick section of sapropel
(up to 15% Corg), calcareous clay, and diatom ooze with the age of 120 ka at the core bottom. The section is subdivided into three units:
Unit I (Holocene) consists of the laminated sapropel; Unit II comprising oxygen isotope stages (MIS) 2, 3, and 4 is represented
by homogeneous calcareous clay with interbeds of slightly siliceous sapropelic mud; and Unit III (MIS-5) is composed of laminated
sapropelic diatom ooze. Laminated intervals are characterized by the intercalation of two lamina types: (1) dark-colored organic-rich
laminae containing multi-species “oceanic” diatom assemblages, as well as radiolarians, coccoliths, planktonic and benthic
foraminifera; (2) lighter-colored laminae consisting of diatom ooze with the neritic colonial diatom assemblages commonly
composed of one to three species of a single genera. The dark laminae are assumed to be generated within a high productivity
zone over the slope, whereas light ones likely represent diatom mats produced by short-term boisterous phytoplankton blooms,
possibly in the coastal upwelling. 相似文献