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1.
The suspended particulate organic matter, SPOM, in the autumnal Black Sea has been characterised using catalytic hydropyrolysis (HyPy) of the total (bound plus free) lipid material. The technique, which generates maximum yields of volatile products from sediments, kerogens and phytoplankton, was followed using gas chromatography and gas chromatography/mass spectrometry. The generated alkanes were dominated by n-C18, hypothesised to arise predominantly from unsaturated C18 fatty acids. Steranes were generated from reductive conversion of free and bound sterols. The generation of branched alkanes and especially of hopanes provided formal evidence for the participation of bacteria in the mineralisation of the SPOM. Whereas similar distributions of n-alkanes were generated from SPOM sampled from different depths of the comparatively well-stirred Rhodes Gyre (eastern Mediterranean), mineralisation of the SPOM at each depth of the central Black Sea produced characteristic changes in the composition and concentration of the HyPy products. Depth profiles of the n-alkanes generated from SPOM in the region of the Rim Current were affected by the local hydrography. Polynuclear aromatic hydrocarbons (PAHs) of anthropogenic origin were present in the surface waters of the central Black Sea. Some methyl benzenes, thiophenes and pyrroles were also generated.  相似文献   

2.
The Western Black Sea basin opened during Cretaceous times by back-arc rifting in association with a north dipping subduction at the rear of the Cretaceous–Early Tertiary Pontide volcanic arc. The sedimentary wedge developed on the shelf of the Romanian Black Sea sector reflects a complex interplay between large scale rifting, uplift of the orogenic flanks, large-scale post-rift subsidence and sea level changes. We examine the detailed structural configuration of this sector for a regional correlation with the adjacent offshore in Ukraine and Bulgaria. The evolution of the western Black Sea basin started in the Albian–Cenomanian times, when two extensional phases with significantly different directions (N–S and subsequently E–W) lead to the formation of a complex interplay between isolated blocks organised in horsts and grabens generally deepening eastwards. Superposition of normal faults footwall blocks from the two extensional episodes generated a deeply subsided area with enhanced accommodation space, i.e., the Histria Depression, and, consequently, recorded a larger thickness of Paleogene sediments in the post-rift stage. (Re)activation of faults and associated folding reflects repeated inversion during the Late Cretaceous–Oligocene times, associated with subsequent periods of non-deposition and/or erosion during moments of basin fill exposure. These periods of inversion recorded in the Black Sea are controlled by coeval orogenic deformations taking place in the Balkans, Pontides and the Crimean thrust belt. Sea level fluctuations during the Neogene and late Alpine tectonics in the neighbouring orogens caused massive sedimentation followed by sediment starvation and/or significant erosion. Large thicknesses of sediments accumulated during the Pontian, presumably associated with an extensional episode deepening the distal parts of the basin and with differential compaction structures. The interpretation of a high-quality seismic dataset combined with published data allowed the correlation of major structural units and lineaments defined onshore towards the Carpathians with the ones deeply buried below the western Black Sea basin sediments. Unit correlations are furthermore used to derive an integrated tectonic image of the western Black Sea area.  相似文献   

3.
We describe an active right-lateral strike-slip fault zone along the southern margin of the Japan Sea, named the Southern Japan Sea Fault Zone (SJSFZ). Onshore segments of the fault zone are delineated on the basis of aerial photograph interpretations and field observations of tectonic geomorphic features, whereas the offshore parts are interpreted from single-/multichannel seismic data combined with borehole information. In an effort to evaluate late Quaternary activity along the fault zone, four active segments separated by uplifting structures are identified in this study. The east–northeast-trending SJSFZ constitutes paired arc-parallel strike-slip faults together with the Median Tectonic Line (MTL), both of which have been activated by oblique subduction of the Philippine Sea plate during the Quaternary. They act as the boundaries of three neotectonic stress domains around the eastern margin of the Eurasian plate: the near-trench Outer zone and NW–SE compressive Inner zone of southwest Japan arc, and the southern Japan Sea deformed under E–W compression from south to north.  相似文献   

4.
Based on proxy records from western Black Sea cores, we provide a comprehensive study of climate change during the last glacial maximum and late-glacial period in the Black Sea region. For the first time we present a record of relative changes in precipitation for NW Anatolia based on variations in the terrigenous supply expressed as detrital carbonate concentration. The good correspondence between reconstructed rainfall intensity in NW Anatolia and past western Mediterranean sea surface temperatures (SSTs) implies that during the glacial period the precipitation variability was controlled, like today, by Mediterranean cyclonic disturbances. Periods of reduced precipitation correlate well with low SSTs in the Mediterranean related to Heinrich events H1 and H2. Stable oxygen isotopes and lithological and mineralogical data point to a significant modification in the dominant freshwater/sediment source concomitant to the meltwater inflow after 16.4 cal ka BP. This change implies intensification of the northern sediment source and, with other records from the Mediterranean region, consistently suggests a reorganization of the atmospheric circulation pattern affecting the hydrology of the European continent. The early deglacial northward retreat of both atmospheric and oceanic polar fronts was responsible for the warming in the Mediterranean region, leading simultaneously to more humid conditions in central and northern Europe.  相似文献   

5.
Ferruginate shells and tubular worm burrows from the oxygenated zone of the Black Sea (Kalamit Bay and Danube River mouth) are studied using transmission and scanning electron microscopy combined with analyses of elemental composition. Iron and manganese hydroxide nodules considered here are enriched in phosphorus. They contain variable amounts of terrigenous and biogenic material derived from host sediments. The hydroxides are mainly characterized by colloform structure, whereas globular and crystalline structures are less common. The dominating iron phase is represented by ferroxyhite and protoferroxyhite, whereas the manganese phase is composed of Fe-free vernadite. Relative to sediments, concentrations of Mn, As, and Mo increase 12–18 times, while concentrations of Fe, P, Ni, and Co increase 5–7 times during the nodule formation.  相似文献   

6.
Partitioning of heavy metals in surface Black Sea sediments   总被引：1，自引：0，他引：1  
Bulk heavy metal (Fe, Mn, Co, Cr, Ni, Cu, Zn and Pb) distributions and their chemical partitioning, together with TOC and carbonate data, were studied in oxic to anoxic surface sediments (0–2 cm) obtained at 18 stations throughout the Black Sea. TOC and carbonate contents, and available hydrographic data, indicate biogenic organic matter produced in shallower waters is transported and buried in the deeper waters of the Black Sea. Bulk metal concentrations measured in the sediments can be related to their geochemical cycles and the geology of the surrounding Black Sea region. Somewhat high Cr and Ni contents in the sediments are interpreted to reflect, in part, the weathering of basic-ultrabasic rocks on the Turkish mainland. Maximum carbonate-free levels of Mn (4347 ppm), Ni (355 ppm) and Co (64 ppm) obtained for sediment from the shallow-water station (102 m) probably result from redox cycling at the socalled ‘Mn pump zone’ where scavenging-precipitation processes of Mn prevail. Chemical partitioning of the heavy metals revealed that Cu, Cr and Fe seem to be significantly bound to the detrital phases whereas carbonate phases tend to hold considerable amounts of Mn and Pb. The sequential extraction procedures used in this study also show that the metals Fe, Co, Ni, Cu, Zn and Pb associated with the ‘oxidizable phases’ are in far greater concentrations than the occurrences of these metals with detrital and carbonate phases. These results are in good agreement with the recent studies on suspended matter and thermodynamic calculations which have revealed that organic compounds and sulfides are the major metal carriers in the anoxic Black Sea basin, whereas Fe-Mn oxyhydroxides can also be important phases of other metals, especially at oxic sites. This study shows that, if used with a suitable combination of the various sequential extraction techniques, metal partitioning can provide important information on the varying geological sources and modes of occurrence and distribution of heavy metals in sediments, as well as, on the physical and chemical conditions prevailing in an anoxic marine environment.  相似文献   

7.
Past hydrological interactions between the Mediterranean Sea and Black Sea are poorly resolved due to complications in establishing a high‐resolution time frame for the Black Sea. We present a new greigite‐based magnetostratigraphic age model for the Mio‐Pliocene deposits of DSDP Hole 380/380A, drilled in the southwestern Black Sea. This age model is complemented by 40Ar/39Ar dating of a volcanic ash layer, allowing a direct correlation of Black Sea deposits to the Messinian salinity crisis (MSC) interval of the Mediterranean Sea. Proxy records divide these DSDP deposits into four intervals: (i) Pre‐MSC marine conditions (6.1–6.0 Ma); (ii) highstand, fresh to brackish water conditions (~6.0–5.6 Ma); (iii) lowstand, fresh‐water environment (5.6–5.4 Ma) and (iv) highstand, fresh‐water conditions (5.4–post 5.0 Ma). Our results indicate the Black Sea was a major fresh‐water source during gypsum precipitation in the Mediterranean Sea. The introduction of Lago Mare fauna during the final stage of the MSC coincides with a sea‐level rise in the Black Sea. Across the Mio‐Pliocene boundary, sea‐level and salinity in the Black Sea did not change significantly.  相似文献   

8.
Information on the depth of the sulfide onset in the Black Sea has been analyzed for the period 1910–1995. Correlation between the depth of the sulfide onset and the density structure of the layer of the main pycnocline is significant for the entire period covered. Correlation coefficients (R) between the depth of the sulfide onset and the position of isopycnal surfaces in the layer of the main pycnocline vary, on average, 0.71–0.88. The average value of density (t) at the depth of sulfide onset, defined as a sulfide concentration equal to 3 M, is close to 16.17. Oscillations in the average depth of the sulfide onset range over 24 m and indicate that a steady-state trend does not occur. The period of these oscillations may occur over a century timescale. The dataset for the period 1960–1995 has been used to analyze temporal variations in concentrations of sulfide inside the anoxic zone of the Black Sea. The results of isopycnal analysis demonstrate that possible temporal variations in the average position of sulfide onset versus density (t) scale do not exceed 0.15, which is close to the limit of uncertainties for data obtained before 1988. In contrast, a prominent increase in sulfide concentration, as well as nutrient levels, within the anoxic zone is shown and is related to anthropogenic impact.  相似文献   

9.
Land-locked seas were polluted mainly by land-based pollutants. The Black Sea is the largest enclosed sea in the world and widely perceived to be heavily polluted. In order to determine the impact of marine activities on heavy metal pollution, shore (500 m distance from edge)–offshore (5,555 m distance from edge) samples of various stations through the Sinop, Samsun and Ordu cities located in the Middle Black Sea region between May 2000 and October 2001 were taken. In addition, samples were taken between April–May 2000 in order to designate the heavy metal pollution of certain rivers, streams, harbor and shores in Samsun’s boundary and 32 sampling stations for the routine pollution monitoring studies are selected including rivers, streams, industrial and domestic discharge points along the Black Sea coast of Turkey in the year 1996. Heavy metal concentrations of whole samples were measured and compared with “Quality Criteria of General Marine and Continental Inside Water Sources” currently effective in Turkey so as to bring up the levels of pollution in marine, rivers and streams.  相似文献   

10.
Currently, the species list of the macroalgae (excluding Charales) inhabiting the southern seas of Russia includes 388 species, specifically, 362 species in the Black Sea, 46 species in the Sea of Azov, and 70 species in the Caspian Sea. The species list has been increased by approximately 30% (96 species, most of them are registered in the Black Sea), compared to the data obtained 30 years ago. The green and red macroalgae of warm-water Mediterranean and tropical origin (Ceramium, Polysiphonia, Laurencia, Ulva, and Chaetomorpha) and brown algae (Sargassum and Cytoseira) were the key invaders. Nowadays the maximal species diversity is found on the Crimean coast and the Turkish coast of the Black Sea; and the species list of the Turkish coast differs significantly from all the other studied sites of the Black Sea. The number of the algae of the warm-water complex increased the most in 1990s–2000s in the Black Sea; species of boreal-tropical and subtropical origin dominate. However, such a tendency was not observed in the Sea of Azov and in the Caspian Sea, but expansion of the habitats of the brackish green algae has been registered.  相似文献   

11.
The Sea of Marmara Basin (SMB) is connected to the fully marine Mediterranean by the Dardanelles strait and to the brackish Black Sea by the Thracian Bosporus. This linkage to two different marine realms with contrasting water chemistry has been a prime control on the sedimentary history of the SMB, which in turn was controlled by its tectonics. Isolation from any of these realms resulted in drastic changes in its paleoceanographic conditions and made it a part either of the global ocean system or of a brackish-marine environment, depending on the realm from which the connection was severed.

The SMB represents the inundated part of the northwestern Anatolian graben system that resulted from the interaction between the North Anatolian fault (NAF) zone and the present N-S extensional tectonic regime of the Aegean. The geologic history of this basin began during the late Serravallian when the NAF was initiated. The first inundation of the basin coincided in both time and space with this initiation. The invading sea was the Mediterranean, which stayed there for a short period and subsequently was replaced by the Paratethys during the late Miocene. Paratethyan conditions prevailed in the basin until the latest Pliocene, when the second flooding from the Mediterranean occurred through the Dardanelles. Owing to glacio-eustatic sea-level changes during the Pleistocene, Paratethyan/Black Sea and Mediterranean conditions alternated. In the last (Würm) glaciation, the SMB was completely isolated and turned into a euxinic lacustrine environment, similar to the Black Sea at that time. Following the Würm glaciation, the Mediterranean Sea broke its way once more into the SMB and filled it with salt water. When sea level in the basin rose above the Bosporous sill at 7.5 Ka B.P., the present dual flow regime was established.  相似文献   

12.
After the Last Glacial Maximum, the semi-land-locked Black Sea basin was flooded by warm water from the Mediterranean Sea. This major sea level rise and change of physical water properties had a large impact on the gas hydrate reservoir in the sediments below. Modelling of the regional response of the gas hydrate stability zone (GHSZ) to the Black Sea flooding 7100 years ago shows that a strong effect of near-bottom temperature increase pushes the gas hydrate reservoir to a large shrinking of 15–62% that may release up to 1.1–4.6 Gt of methane. This catastrophic scenario is, however, delayed because of the transient nature of the heat wave propagation. The large-scale reduction of the GHSZ is only to take place within the next thousand years. At present, widespread hydrate dissociation is only expected to occur where there is a minimum water depth for hydrate stability.  相似文献   

13.
Bacteriohopanepolyols (BHPs) are lipid constituents of many bacterial groups. Geohopanoids, the diagenetic products, are therefore ubiquitous in organic matter of the geosphere. To examine the potential of BHPs as environmental markers in marine sediments, we investigated a Holocene sediment core from the Black Sea. The concentrations of BHPs mirror the environmental shift from a well-mixed lake to a stratified marine environment by a strong and gradual increase from low values (∼30 μg g−1 TOC) in the oldest sediments to ∼170 μg g−1 TOC in sediments representing the onset of a permanently anoxic water body at about 7500 years before present (BP). This increase in BHP concentrations was most likely caused by a strong increase in bacterioplanktonic paleoproductivity brought about by several ingressions of Mediterranean Sea waters at the end of the lacustrine stage (∼9500 years BP). δ15N values coevally decreasing with increasing BHP concentrations may indicate a shift from a phosphorus- to a nitrogen-limited setting supporting growth of N2-fixing, BHP-producing bacteria. In sediments of the last ∼3000 years BHP concentrations have remained relatively stable at about 50 μg g−1 TOC.The distributions of major BHPs did not change significantly during the shift from lacustrine (or oligohaline) to marine conditions. Tetrafunctionalized BHPs prevailed throughout the entire sediment core, with the common bacteriohopanetetrol and 35-aminobacteriohopanetriol and the rare 35-aminobacteriohopenetriol, so far only known from a purple non-sulfur α-proteobacterium, being the main components. Other BHPs specific to cyanobacteria and pelagic methanotrophic bacteria were also found but only in much smaller amounts.Our results demonstrate that BHPs from microorganisms living in deeper biogeochemical zones of marine water columns are underrepresented or even absent in the sediment compared to the BHPs of bacteria present in the euphotic zone. Obviously, the assemblage of molecular fossils in the sediments does not represent an integrated image of the entire community living in the water column. Remnants of organisms living in zones where effective transport mechanisms - such as the fecal pellet express - exist are accumulated while those of others are underrepresented. Our work shows a high stability of BHPs over geological time scales. Largely uniform distributions and only minor changes in structures like an increasing prevalence of saturated over unsaturated BHPs with time were observed. Consequently, sedimentary BHP distributions are less suitable as markers for in situ living bacteria but are useful for paleoreconstructions of bacterioplanktonic communities and productivity changes.  相似文献   

14.
We present the results of work on the compilation of a fuller and more comprehensive historical catalogue of earthquakes and tsunamis in the basin of the Black Sea and the Sea of Azov, an area of primary importance for the Russian Federation. In the 20th century, there were no significant tsunamis in the Black Sea; therefore, its coast was not considered tsunami-prone. A systematic search for new data sources, a revision of earlier ones, and the use of new approaches to the identification of tsunamigenic events resulted in a more than doubling of the number of known tsunamigenic events in this basin, bringing it up to 50. The total length of the new tsunami catalogue reached 3000 years, which makes it the second longest after the Mediterranean tsunami catalogue (about 4000 years). Taking into account the seismotectonic features of the Black Sea region, we processed data on historical tsunamis and analyzed the geographical and temporal distributions of their sources. For all tsunamigenic events we performed a parameterization of available information about their sources and coastal manifestations, evaluated the tsunami intensity based on the Soloviev-Imamura scale, and proposed a classification of tsunami and tsunami-like water wave disturbances based on their genesis. Tsunami run-up heights, inland penetration, and damage were estimated with regard for the newly found data. Among the identified historical events, there are devastating tsunamis with run-ups of 4-5 m, sometimes up to 6-8 m, which resulted in disastrous consequences for several ancient cities (Dioscuria, Sebastopolis, Bizone, and Panticapaeum) and many coastal settlements. Expert assessments of the most tsunami-prone areas of the coasts are given.  相似文献   

15.
As part of the Antarctic Digital Magnetic Mapping Project (ADMAP) workers from VNIIOkeangeologia (Russia), the British Antarctic Survey (UK) and the Naval Research Laboratory (USA) have brought together almost all of the available magnetic data in the area 0–120°W, 60–90°S. The final map covers the whole Weddell Sea and adjacent land areas, the Antarctic Peninsula and the seas to the west, an area comparable in size with that of the USA. This paper describes the methods used during the compilation of the map and reviews briefly some of the main features shown on it. Distinct magnetic provinces are associated with Precambrian rocks of the East Antarctic craton, highly extended continental crust in the Weddell Sea embayment, the arc batholith of the Antarctic Peninsula, and oceanic crust of the northern Weddell Sea, which was created as a direct consequence of South America–Antarctica plate motion and oceanic crust generated at the Pacific–Antarctic ridge. The magnetic anomaly map thus provides an overview of the fragmentation of south-western Gondwana and the tectonic development of the Weddell Sea sector of Antarctica.  相似文献   

16.
All the available historic records of sea level and appropriate weather charts have been used to study storm surges in the northern part of the Sea of Japan. The generation of surges in this area was investigated by means of a two-dimensional numerical model. Computed sea levels were compared with hourly observed residual sea levels in De-Kastri. The agreement between computed and observed storm surges is quite satisfactory. The relative importance of various meteorological parameters and bottom topography in formation of the strong storm surge on 20–21 September 1975 was studied numerically.  相似文献   

17.
Ten years after the USAC (U.S.–Argentina–Chile) Project, which was the most comprehensive aeromagnetic effort in the Antarctic Peninsula and surrounding ocean basins, questions remain regarding the kinematics of the early opening history of the Weddell Sea. Key elements in this complex issue are a better resolution of the magnetic sequence in the western part of the Weddell Sea and merging the USAC data set with the other magnetic data sets in the region. For this purpose we reprocessed the USAC data set using a continuation between arbitrary surfaces and equivalent magnetic sources. The equivalent sources are located at a smooth crustal surface derived from the existing bathymetry/topography and depths estimated by magnetic inversions. The most critical area processed was the transition between the high altitude survey over the Antarctic Peninsula and the low altitude survey over the Weddell Sea that required downward continuation to equalize the distance to the magnetic source. This procedure was performed with eigenvalue analysis to stabilize the equivalent magnetic source inversion.The enhancement of the Mesozoic sequence permits refining the interpretation of the seafloor-spreading anomalies. In particular, the change in shape and wavelength of an elongated positive in the central Weddell Sea suggests that it was formed during the Cretaceous Normal Polarity Interval. The older lineations in the southwestern Weddell Sea are tentatively attributed to susceptibility contrasts modeled as fracture zones. Numerical experimentation to adjust synthetic isochrons to seafloor-spreading lineations and flow lines to fracture zones yields stage poles for the opening of the Weddell Sea since 160 Ma to anomaly 34 time. The corresponding reconstructions look reasonable within the known constraints for the motions of the Antarctic and South America plates. However, closure is not attained between 160 and 118 Ma if independent published East Antarctica–Africa–South America rotations are considered. The lack of closure may be overcome by considering relative motion between the Antarctic Peninsula and East Antarctica until 118 Ma time, an important component of convergence.  相似文献   

18.
A comprehensive record of lake level changes in the Dead Sea has been reconstructed using multiple, well dated sediment cores recovered from the Dead Sea shore. Interpreting the lake level changes as monitors of precipitation in the Dead Sea drainage area and the regional eastern Mediterranean palaeoclimate, we document the presence of two major wet phases ( 10–8.6 and  5.6–3.5 cal kyr BP) and multiple abrupt arid events during the Holocene. The arid events in the Holocene Dead Sea appear to coincide with major breaks in the Near East cultural evolution (at  8.6, 8.2, 4.2, 3.5 cal kyr BP). Wetter periods are marked by the enlargement of smaller settlements and growth of farming communities in desert regions, suggesting a parallelism between climate and Near East cultural development.  相似文献   

19.
Late Cenozoic geodynamic evolution of eastern Indonesia   总被引：2，自引：0，他引：2  
This paper presents an internally and globally consistent model of plate evolution in eastern Indonesia from Middle Miocene to Present time. It is centered on the Banda Sea region located in the triple junction area between the Pacific–Philippine, Australia and South–East Asia plates. The geological and geophysical data available from Indonesia were until recently insufficient to define a unique plate tectonic model. In this paper, the new data taken into account clearly restrict the possible interpretations. Owing to a great number of geological, geophysical and geochemical studies, the major plate boundaries (the Sunda–Banda subduction zone to the south, the Tarera–Aiduna Fault zone and the Seram Thrust to the east, and the Sorong Fault zone and Molucca Sea collision zone to the north) are now clearly identified. The age of the major tectonic structures is also better known. Geodetic measurements well constrain the Present time plate kinematics. We also consider the deformation history within eastern Indonesia, where numerous short-lived microplates and their related microcontinents successively accreted to the Asiatic margin. Moreover, magnetic anomalies identification of the North and South Banda Sea basins allows a precise kinematic reconstruction of the back-arc opening. We used the Plates software to test the coherency of our model, presented as a series of 4 plate reconstruction maps from 13 Ma to the present. Finally, the origin of oceanic domains restored by our reconstruction is discussed.  相似文献   

20.
【研究目的】在末次冰期，全球气候变化以千年尺度的快速、大幅度温度波动旋回为特征，这种波动变化在两极冰芯、深海沉积、中国黄土和洞穴石笋等诸多地质样品中均有记录。黑海位于北大西洋与东亚季风区过渡带，具有极有代表性的沉积记录。本文旨在通过对黑海沉积序列的研究，建立起其区域环境变化与北大西洋及东亚季风气候域气候变化的联系。【研究方法】研究对取自黑海西北部罗马尼亚陆坡区多瑙河峡谷北侧GAS-CS12钻孔的长22.0 m的岩芯样品，进行了粒度、矿物成分、主量元素、有机碳、总氮及碳氮同位素等分析。【研究结果】揭示出该段岩芯沉积于末次冰期中后期“Neoeuxine”湖相阶段，可划分为5个沉积单元，对应于北大西洋H4、H3、H1气候变化事件、末次冰盛期（LGM）及Bolling-Allerod气候变暖事件。【结论】建立起了其沉积序列及区域环境变化与北大西洋及东亚季风气候域气候变化的联系，印证了末次冰期千年尺度的气候变化事件在北大西洋、东亚季风区及两者过渡带上具有高度的一致性。创新点：建立了黑海西北沉积序列与区域环境变化的关系；补充了北大西洋与东亚季风区两者过渡带上气候波动事件的可靠时标。  相似文献   

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