Influence of anthropogenic pressure and seasonal upwelling on coral reefs in Nha Trang Bay (Central Vietnam)          下载免费PDF全文

Konstantin S. Tkachenko  Temir A. Britayev  Nguyen H. Huan  Mikhail V. Pereladov  Yuri Y. Latypov 《Marine Ecology》2016,37(5):1131-1146

The growing coastal development, dredging and dumping activities, overfishing and expansion of marine cage culture in Nha Trang Bay (NTB) of Central Vietnam since the beginning of the 2000s have resulted in a dramatic decrease of live coral cover. Surveys conducted in April–May 2013 and the same period in 2014 revealed that with an increase in distance from the outer part of the bay towards the mainland, the rivers’ influxes and dredged areas, coral cover decreased from 75% to 0.6% and species richness from 63 to 5, while the abundance of macroalgae increased from 0% to 56%. These changes correlate with differences in the concentration of suspended sediments on the same gradient. The abundance of the crown‐of‐thorns starfish Acanthaster planci and of the echinoid Diadema setosum significantly increased between the first estimation in 1998 and the survey in 2014, from 0 to 1.7 individuals (ind.) per 100 m^?2 and from 50.8 to 94.5 ind. per 100 m^?2, respectively, contributing to coral loss and intensive bioerosion of the reef framework in the bay. The large sizes of adult colonies of tabulate Acropora on the remote stations with negligible sedimentation and eutrophication loads were inconsistent with the assumptions that temperature‐induced coral bleaching or cyclones could be the major impacts in Nha Trang Bay. Analysis of the 16‐year thermal history of the bay did not reveal any instances in which the coral thermal bleaching threshold had been exceeded up to the present study. Seasonal upwelling, which occurs annually in the vicinity of Central Vietnam, may contribute to mitigation of thermal anomalies within NTB and to the maintenance of healthy coral communities on the remote reefs with relatively low anthropogenic impact.  相似文献   

Formation of intracratonic basins by lithospheric shortening and phase changes: a case study from the ultra‐deep East Barents Sea basin     

Sébastien Gac  Ritske S. Huismans  Nina S. C. Simon  Yuri Y. Podladchikov  Jan Inge Faleide 《地学学报》2013,25(6):459-464

The origin of large subsidence in intracratonic basins is still under debate. We propose a new and self‐consistent model for the formation of those basins, where lithospheric shortening/buckling triggers metamorphism and densification of crustal mafic heterogeneities. We use a forward thermo‐mechanical finite element technique to evaluate this mechanism for the typical example of the East Barents Sea basin (EBB) where a very large and compensated subsidence, accommodating an up to 20‐km‐thick sediment succession, is observed. The lower crust in the dynamic model is modelled with petrologic‐consistent densities for a wet mafic gabbroic composition that depend on pressure and temperature taking into account dehydration at high PT conditions. The model successfully explains the main characteristics of the EBB, notably the large anomalous and fast subsidence during the Late Permian–Early Triassic, its present‐day geometry and the absence of a significant gravity anomaly.  相似文献   

Campanian Climatic Change: Isotopic Evidence from Far East, North America, North Atlantic and Western Europe          下载免费PDF全文

Yuri D. Zakharov  Yasunari Shiget  Kazushige Tanabe  Yasuhiro I  Olga P. Smyshlyaev  Ekaterina A. Sokolov  Alexer M. Popov  Tatiana A. Velivetskay  Tamara B. Afanasyeva 《《地质学报》英文版》2007,81(6):1049-1069

Paleoclimatic settings have been reconstructed for the Campanian using original oxygen-isotopic analyses of well-preserved molluskan and foraminifera shells from Russian Far East, Hokkaido, USA, Belgium and some DSDP holes (95, 98, 102, 390A, and 392A) in North Atlantic. Early Early Campanian climatic optimum has been recognized from data on high bottom shelf water paleotemperatures in middle latitudes of both the western circum-Pacific (to 24.2°C) and the eastern circum-Pacific (to 26.4°C) areas and high bottom shallow water paleotemperatures in high latitudes of the Koryak Upland (22.4–25.5°C), which agrees with the data on the Campanian Barykovskaya flora in high latitudes (Golovneva and Herman, 1998) and Jonker flora and its equivalents in middle latitudes. Judging from the data on comparatively high bottom shallow water paleotemperature values in high latitudes, South Alaska (19.4°C) and the Koryak Upland (22.4–25.5°C), we also expect Latest Campanian temperature maximum, which has not been confirmed, however, for low and middle latitudes by neither of isotopic nor paleobotanic data now. Main climatic tendency during the Campanian (with the exception of Latest Campanian) has been learned from isotopic composition of Campanian aragonitic ammonoid shells from the Hokkaido-South Sakhalin (Krilyon) marine basin. In contrary to Huber’s et al. (2002) assumption, we expect warm greenhouse conditions during the most part of the Campanian.  相似文献   

Introduction     

Nemesio M. Pérez  Sergio Gurrieri  Chi-Yu King  Yuri Taran 《Pure and Applied Geophysics》2007,164(12):2373-2375

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鄂霍茨克海的地球物理场与地质构造   总被引：1，自引：0，他引：1  

郝天珧  Yuri Neprochnov  江为为  宋海滨  刘建华  刘伊克 《地球物理学进展》2001,16(1):1-10

鄂霍茨克海位于西太平泮边缘海最北部，受欧亚大陆板块和太平洋板块的作用，有十分复杂的地质地球物理特征，鄂霍茨克海不仅有海隆，还有三个著名的盆地，其中的千岛盆地，是研究鄂霍茨克海的一个窗口，本文通过对大量相关资料的二次开发，详细地讨论了鄂霍茨克海的地球物理场特征，沉积特点、热流分及深部结构特点，并对该边缘海的形成演化进行了初步的探讨，我们认为，对鄂霍茨克海研究的结果，将对中国边缘海地质特征的研究起到帮助和借鉴作用。  相似文献   

Strain and competence contrast estimation from fold shape     

Stefan M. Schmalholz  Yuri Yu. Podladchikov 《Tectonophysics》2001,340(3-4):195-213

A new method to estimate strain and competence contrast from natural fold shapes is developed and verified by analogue and numerical experiments. Strain is estimated relative to the nucleation amplitude, A_N, which is the fold amplitude when the amplification velocities caused by kinematic layer thickening and dynamic folding are identical. A_N is defined as the initial amplitude corresponding to zero strain because folding at amplitudes smaller than A_N is dominantly by kinematic layer thickening. For amplitudes larger than A_N, estimates of strain and competence contrast are contoured in thickness-to-wavelength (H/λ) and amplitude-to-wavelength (A/λ) space. These quantities can be measured for any observed fold shape. Contour maps are constructed using existing linear theories of folding, a new nonlinear theory of folding and numerical simulations, all for single-layer folding. The method represents a significant improvement to the arc length method. The strain estimation method is applied to folds in viscous (Newtonian), power-law (non-Newtonian) and viscoelastic layers. Also, strain partitioning in fold trains is investigated. Strain partitioning refers to the difference in strain accommodated by individual folds in the fold train and by the whole fold train. Fold trains within layers exhibiting viscous and viscoelastic rheology show different characteristic strain partitioning patterns. Strain partitioning patterns of natural fold trains can be used to assess the rheological behaviour during fold initiation.  相似文献   

Paleolithic archeology and the paleogeographical study of loess-paleosol sequences in Eastern Europe     

Elena I. Kurenkova  Yuri N. Gribchenko  Ludmila V. Grekhova 《GeoJournal》1995,36(2-3):229-235

The paper is concerned with problems of the study of Paleolithic sites in the loess regions of the Russian Plain. It is of great significance to correlate prehistorical settlement with Upper Pleistocene cycles of loess and soil formation — not solely in the reconstruction of paleoenvironments. From the cultural layers at various sites paleontological finds and objects were collected for radiocarbon dating. A complex analysis of archeological objects embedded in the loess-paleosol sequence helps us date Upper Pleistocene loess formation cycles. The data acquired from the investigation of the lithological properties of loess and their modification through time and their dependence on relief characteristics permitted a correlation between the various paleoenvironments and the dust accumulation cycles, which played a decisive role in the selection of the most habitable sites.  相似文献   

Storm surges in the northern part of the Sea of Japan     

Yuri V. Lyubitsky 《Natural Hazards》1995,11(2):99-110

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   

A candidate of the Induan-Olenekian boundary stratotype in the Tethyan region   总被引：10，自引：0，他引：10  

童金南  Yuri D.Zakharov  殷鸿福  Hans J.Hansen 《中国科学D辑(英文版)》2003,46(11):1182-1200

The Olenekian Stage was proposed by Kiparisova and Popov[1] based on the type section along the lower reaches of the Olenek River, Siberia. Later research showed that this section con-tains only the Olenikites spiniplicatus Zone of the Upper Olenekian Sta…  相似文献   

Improved approaches to ecotoxicity testing of petroleum products     

Tsvetnenko Y  Evans L 《Marine pollution bulletin》2002,45(1-12):148-156

Crude oils produced in the North West shelf of Western Australia are highly volatile, a characteristic not shared by most of the Northern Hemisphere crude oils on which internationally accepted toxicity test protocols were developed. Because of this volatility and some other factors, the LC50 and EC50 values obtained from acute toxicity tests will be significantly affected by the changes of toxicant concentration in test solutions during the period of exposure. To address these issues all steps of a standard protocol for crude oil toxicity testing have been revised. A systematic study has been performed on factors which affect petroleum hydrocarbon solubilisation in aqueous systems during test solution preparations. The influence of mixing time, agitation energy and volume/interface ratio on a hydrocarbon concentration in a water-soluble fraction (WSF) was studied for heavy, medium and light crude oils. A study of the sensitivity of marine unicellular algae to WSF of crude oils was conducted with Isochrysis sp., Nannochloropsis-like sp. and Nitzchia closterium. Total concentrations of hydrocarbons dissolved in test solutions were estimated by UV-spectrometry and GC/FID chemical analyses. When the toxicant concentration decreased during the exposure period, the EC50 values derived from initial or final concentrations either underestimate or overestimate toxicity, respectively. Therefore, weighted average concentrations (WAC) calculated for the whole test period were recommended for expressing hydrocarbon concentrations in test solutions of crude oils. Toxicity indices calculated from WAC of total hydrocarbons for different crude oils can be compared regardless of the rates of hydrocarbon loss.  相似文献