Hydrology, circulation and distribution of particulate matter in Thermaikos Gulf (NW Aegean Sea), during September 2001–October 2001 and February 2002     

V. Zervakis  A.P. Karageorgis  H. Kontoyiannis  V. Papadopoulos  V. Lykousis 《Continental Shelf Research》2005,25(19-20):2332

The hydrography, circulation and distribution of particulate matter in Thermaikos Gulf (NW Aegean Sea) are described, for September 2001 and October 2001 and February 2002. The observations were obtained to assess the impact of anthropogenic and natural resuspension processes on the coastal ecosystem. The first two periods represent highly stratified conditions and mild weather conditions; in September trawling is prohibited, whilst the October cruise took place following the commencement of the activity. The sampling in February was undertaken to record the contribution of natural resuspension to the system, in a stormy period.The water circulation was mainly baroclinic during autumn and barotropic in winter; this was due to vertical homogenisation of the water column, during the latter period. The distribution of the bottom nepheloid layer (BNL) was very different in the winter than in the autumn.Microstructure measurements were undertaken, which allowed the vertical eddy diffusivity to be estimated, together with the near-bed shear stresses. Computation of the diffusive flux of particulate matter (PM), from the BNL into the intermediate water column in response to turbulent motions, reveals that the PM flux was much higher in October than in September; this is despite the fact that the friction velocities were similar. This observation could explain partly the observed higher PM concentrations (PMC) in the intermediate layer, in October. Likewise suggest that the higher PMC in October could be attributed to trawling. The limited shear stress and friction velocity values obtained during the September and October cruises were always low; these were possibly capable of resuspending only recently deposited, “fluffy” material. Thus, the observed nepheloid layers are likely to be maintained by advection from the shallow water regions and trawled areas.  相似文献   

Potential toxicity of resuspended particulate matter and sediments: Environmental samples from the Bay of Banyuls-sur-Mer and Thermaikos Gulf     

E. Cotou  A. Gremare  F. Charles  I. Hatzianestis  E. Sklivagou 《Continental Shelf Research》2005,25(19-20):2521

This contribution attempts to determine whether, and to what degree, environmental samples of resuspended particulate matter and sediments exert a toxicological impact. Further, an attempt is made also to screen the toxic level of potentially hazardous sites, based upon established sediment toxicity criteria. Therefore, a rapid, cost-effective and highly sensitive biotest (bioluminescence assay, based upon marine bacteria) has been applied on: biological fluid extracts; bottom sediments; and sediment trap samples. Samples were taken either from the Bay of Banyuls-sur-Mer (northwestern Mediterranean, France) or Thermaikos Gulf (northeastern Mediterranean, Greece). Biological fluid extracts and sediment trap samples corresponded to periods of resuspension events, or preceding and following such events.The results have revealed that the sampling strategy and biotest implemented in this study might be a useful tool for screening the toxicity of resuspended matter and sediments. Resuspension events appear to be able to exert an influence on the chemical forms of the micro-pollutants; thus on their bioavailability and toxicity. Nevertheless, based upon chemical analysis combined with the bioassay, the toxic level of the sediment samples could be determined, with the level at potentially hazardous sites being characterised.  相似文献   

Morphological and microtectonic analysis of Quaternary deformation from Puná and Santa Clara Islands, Gulf of Guayaquil, Ecuador (South America)     

J.F. Dumont  E. Santana  W. Vilema  K. Pedoja  M. Ordez  M. Cruz  N. Jimnez  I. Zambrano 《Tectonophysics》2005,399(1-4):331

This paper presents the neotectonic study of Santa Clara and Puná Islands sited in the Gulf of Guayaquil eastern part. Both islands are located on the south-western segment of the fault zone bounding to the east the North Andean Block. Fault motion and morphostructural analysis were carried out from Pleistocene age terrain. A two step deformation characterises the South Puná tectonics. The first step involves the Zambapala Cordillera uplift that post-dates Pleistocene sediments and pre-dates a marine terrace correlated with the M.I.S. 11 or 13 (440–550 ka). The second step is the formation of a pull-apart that shows evidence of 2.9 km dextral offset since the M.I.S. 11 or 13, giving an offset mean rate of 5.3 to 6.6 mm/yr. This rate is higher than the one calculated on the Pallatanga Fault northeast of the study area, in the Western Andean Cordillera, suggesting that deformation is split in different fault segments from the Gulf of Guayaquil to the continent. The Zambapala Cordillera uplift and transpression deformation requires a compressive event that may have been induced by the subduction process during the early Pleistocene.  相似文献   

Hydrography of the eastern Arabian Sea during summer monsoon 2002     

D. Shankar  S. S. C. Shenoi  R. K. Nayak  P. N. Vinayachandran  G. Nampoothiri  A. M. Almeida  G. S. Michael  M. R. Ramesh Kumar  D. Sundar  O. P. Sreejith 《Journal of Earth System Science》2005,114(5):459-474

Hydrographic observations in the eastern Arabian Sea (EAS) during summer monsoon 2002 (during the first phase of the Arabian Sea Monsoon Experiment (ARMEX)) include two approximately fortnight-long CTD time series. A barrier layer was observed occasionally during the two time series. These ephemeral barrier layers were caused byin situ rainfall, and by advection of low-salinity (high-salinity) waters at the surface (below the surface mixed layer). These barrier layers were advected away from the source region by the West India Coastal Current and had no discernible effect on the sea surface temperature. The three high-salinity water masses, the Arabian Sea High Salinity Water (ASHSW), Persian Gulf Water (PGW), and Red Sea Water (RSW), and the Arabian Sea Salinity Minimum also exhibited intermittency: they appeared and disappeared during the time series. The concentration of the ASHSW, PGW, and RSW decreased equatorward, and that of the RSW also decreased offshore. The observations suggest that the RSW is advected equatorward along the continental slope off the Indian west coast.  相似文献   

北部湾沉积物粘土矿物分布特征及其环境意义     

何海军 《地质与勘探》2016,52(3):584-593

本文以南海北部湾SO-31沉积柱为研究对象,研究了14C年代学和粘土矿物学特征,并对部分全球气候事件进行了对比,为古环境、古气候的恢复提供基础资料,也为全球重大气候事件在该区域的响应提供信息。结果显示全新世以来地层沉积正常,平均沉积速率为0.57mm/a。粘土成分主要由蒙脱石、伊利石、高岭石和绿泥石组成,组合类型为蒙脱石-伊利石-高岭石-绿泥石型。全新世以来环境气候演变可划分为五个阶段:低温期阶段、干湿交替的寒冷气候阶段、逐渐升温阶段、干旱温暖气候阶段、湿热阶段。气候在每个阶段背景下还存在一些次级波动,总体趋势为干湿交替,温度逐渐上升。由于海域环境及矿物指标的影响,北部湾SO-31沉积柱粘土矿物记录的降温事件时间比其他指标记录的新仙女木降温事件发生时间滞后500~800a。  相似文献   

辽东湾坳陷东部地区走滑双重构造的发育特征 及其石油地质意义   总被引：6，自引：0，他引：6  

吴智平  张婧  任健  徐长贵  李伟  张晓庆 《地质学报》2016,90(5):848-856

在将构造发育特征与走滑双重构造理论模型进行类比分析的基础上,对辽东湾坳陷东部地区的走滑双重构造的发育特征进行了研究,并结合油气勘探实践成果,就其石油地质意义进行了探讨,研究结果表明:在受控于走滑与拉伸并存的多动力源区域地质背景下,辽东湾坳陷新生代构造演化体现了断陷与拗陷、拉张与走滑的叠加效应,NNE走向的辽中1号断裂、辽中2号断裂及辽东断裂的发育不仅控制了辽东湾坳陷东部地区的凸凹格局,其走滑侧接关系也导致了研究区走滑双重构造的发育;辽东凸起是由于辽中2号断裂、辽东断裂走滑弯曲、右行左阶侧接而形成的挤压走滑双重构造,而辽中凹陷在早期拉张断陷基础上,经历了后期走滑作用的改造,其断裂体系的发育体现了辽中1号断裂与辽中2号断裂的右旋右行侧列所产生的拉张走滑双重构造效应;在走滑双重构造的增压带,断裂侧向封堵性强,有利于形成有效的断层圈闭,是油气藏发育的有利区带。  相似文献   

广西北部湾地区表层土壤中Cu地球化学分布特征及影响因素研究     

郑国东  覃建勋  赵辛金  吴天生  陈彪  陆康运 《矿产与地质》2016,(3):455-460

选取广西北部湾地区表层土壤为研究对象,采集7327件土壤样品,400件岩石样品,分析K_2O、Na_2O、CaO、MgO、SiO_2、Al_2O_3、TFe_2O_3和有机碳,探讨了土壤成土母岩、成土作用、土壤组成和土壤性质等对表层土壤Cu元素的影响。结果表明,研究区表层土壤Cu元素含量低于中国土壤背景值;风化作用对于Cu元素的次生富集起到极为重要的作用,强于成土母岩元素含量背景的影响。Pearson相关分析和主成分分析结果表明,土壤组成和土壤性质等因素中,含Al矿物、含Fe矿物和有机碳(SOC)对土壤Cu的富集起到主导作用;pH和含Ca矿物起到次要作用,而含K矿物、含Na矿物和含Mg矿物的作用较弱,可以忽略不计,SiO_2则起反作用。  相似文献   

辽东宽甸东北沟钼矿二长花岗岩年代学、地球化学及Hf同位素特征   总被引：1，自引：0，他引：1       下载免费PDF全文

张朋  陈冬  寇林林  赵岩  杨宏智 《中国地质》2016,(6):2092-2103

东北沟钼矿是辽宁宽甸地区近些年发现的大型隐爆角砾岩型钼矿床。文章首次对东北沟钼矿床赋矿围岩二长花岗岩进行LA-MC-ICP-MS锆石U-Pb定年,主量元素、微量元素和Hf同位素地球化学研究,锆石U-Pb定年结果表明,二长花岗岩形成年龄为(129.4±0.3)Ma(MSWD=0.83),为燕山期构造岩浆活动产物。地球化学成分上,岩石具有富硅(SiO_2=62.21%~83.21%)、高钾(K_2O/Na_2O=3.35~20.27)和富碱(K_2O+Na_2O=5.82%~12.23%)的特点,属于钾玄岩系列。岩石富集轻稀土元素(LREE/HREE=10.26~24.21),亏损重稀土元素,具有弱负铕异常(δEu=0.63~1.07),富集大离子亲石元素(如K、Rb、Pb)和不相容元素(如Th、U)的特征,相对亏损高场强元素(如Nb、Ta、P、Ti)。锆石Hf同位素分析结果表明,东北沟钼矿二长花岗岩的ε_(Hf)(t)值为介于-12.4~-8.5,二阶段模式年龄(t_(DM2))介于442~1610 Ma,反映岩浆源区可能来源于中元古界古老地壳的再熔融。结合区域构造演化,成岩成矿构造背景为早白垩世古太平洋板块向欧亚之下俯冲,岩石圈减薄的构造环境。  相似文献   

Distribution and relative density of cetaceans in the Hauraki Gulf,New Zealand     

SL Dwyer  DM Clement  MDM Pawley  KA Stockin 《新西兰海洋与淡水研究杂志》2016,50(3):457-480

Understanding species distributions, and how they change in space and time, is vital when prioritising conservation or management initiatives. We assessed the distribution and density patterns of common dolphins (Delphinus sp.), bottlenose dolphins (Tursiops truncatus) and Bryde’s whales (Balaenoptera edeni) in the Hauraki Gulf, New Zealand. Dedicated boat-based surveys were conducted in the inner Hauraki Gulf (IHG) and off Great Barrier Island (GBI) during 2010–2012. Generalised linear models were used to investigate temporal changes in relative densities and kernel density estimation was implemented to examine spatial trends. Common dolphins were widely distributed during all seasons, with higher densities observed during winter and spring in the IHG but during autumn off GBI. There was inter-annual variation in Bryde’s whale distribution, with high densities recorded off GBI in 2011. Bottlenose dolphins were infrequently sighted in the IHG but regularly encountered off GBI, with the highest densities during spring and summer.  相似文献   

The influence of physical and biological processes on the ichthyoplankton communities in the Gulf of Sirte (Southern Mediterranean Sea)          下载免费PDF全文

Angela Cuttitta  Sergio Bonomo  Salem Zgozi  Angelo Bonanno  Bernardo Patti  Enza Maria Quinci  Marco Torri  Mohamed Hamza  Abdul Fatah  Daw Haddoud  Akram El Turki  Abdul Bari Ramadan  Simona Genovese  Salvatore Mazzola 《Marine Ecology》2016,37(4):831-844

This paper reports on the first study on the ichthyoplankton community structure in the Gulf of Sirte and its spatial distribution in relation to environmental conditions and zooplankton abundance. The results make an important contribution to the future management of fisheries in this unexplored, but much exploited, area. Biological samples were collected in July 2008 using a Bongo40 net. In total, 1914 larvae were found and 1652 of these were identified. In particular, bathypelagic taxa were the most abundant, followed by demersal, mesopelagic, pelagic and epipelagic taxa. The ichthyoplankton community had a patchwork distribution influenced by oligotrophic conditions, the bottom depth and oceanographical features. The results suggest that environmental forcings were able to transport the ichthyoplankton to productive areas. Indeed, maximum fish egg densities were found in coastal stations in correspondence with the Atlantic Tunisian Current inflow, whereas larvae were mainly concentrated in the east side of the Gulf, probably as a result of advection by the anticyclonic circulation. Additionally, the distribution patterns of the total larvae density and the different assemblages were well matched with the abundance of the zooplankton, probably determining final larval survival, growth and recruitment.  相似文献