Detection of Miocene saucer‐shaped sills (offshore Senegal) via integrated interpretation of seismic,magnetic and gravity data     

Sergio Rocchi  Alfredo Mazzotti  Michele Marroni  Luca Pandolfi  Paolo Costantini  Bertozzi Giuseppe  Davide di Biase  Francesco Federici  Papa Goumbo L 《地学学报》2007,19(4):232-239

The Atlantic margin offshore Senegal has been explored by seismic reflection and GRAV‐MAG surveys. High‐amplitude, laterally transgressive seismic reflectors are found to coincide with gravimetric and magnetic highs. Once seismic data are integrated with potential fields modelling, these reflectors can be safely interpreted as saucer‐shaped igneous sills, up to some hundreds of metres thick, some km wide. The occurrence of hydrothermal vent complexes and forced folds in the stratigraphic sequence above the sills constrain the intrusion age to the Miocene. Field observations and in‐situ magnetic susceptibility measurements of Oligocene–Miocene and Quaternary igneous rocks emplaced in coastal Senegal support this interpretation.  相似文献   

The scales of variability of stream fish assemblages at tributary confluences     

I. Czeglédi  P. Sály  P. Takács  A. Dolezsai  S. A. Nagy  T. Erős 《Aquatic Sciences - Research Across Boundaries》2016,78(4):641-654

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UV-tolerance and instantaneous physiological stress responses of two Antarctic amphipod species Gondogeneia antarctica and Djerboa furcipes during exposure to UV radiation     

Obermüller B  Puntarulo S  Abele D 《Marine environmental research》2007,64(3):267-285

We investigated the shielding against solar ultraviolet radiation and inducible damage, as well as the short-term response of whole animal metabolic rate in two Antarctic shallow water amphipod species. Light absorbance by the carapace of Gondogeneia antarctica and Djerboa furcipes was higher in the UVR (UVB+UVA) range (42.1% and 54.5% on average respectively) compared to the PAR (photosynthetically active radiation) range (38.1% and 50.1% respectively) of the solar spectrum. Bands of higher absorbance correlated with maximal absorbance ranges of sunscreening compounds indicating mycosporine-like amino acids (MAAs) and carotenoids to be innate compounds of the exoskeleton of these species. Though the antioxidant enzyme catalase was photoinhibited, protein damage products did not accumulate under experimental exposure to a daily dose of 6.84 kJ m(-2) d(-1) UVB, 66.24 kJ m(-2) d(-1) UVA and 103.14 kJ m(-2) d(-1) PAR. Animal oxygen consumption during UV-exposure was measured as an indicator of immediate behavioural and physiological stress response. UVB as well as UVA induced a response with altered and highly variable respiratory intensity. Our findings indicate that sub-lethal UVR exposure causes increased oxygen consumption in polar amphipods due to radiation avoidance, shelter seeking behaviour, and presumably also from cellular repair processes.  相似文献   

Significance of polycyclic aromatic hydrocarbons (PAHs) in Permian/Triassic boundary sections     

Birgit Nabbefeld  Kliti Grice  Roger E. Summons  Lindsay E. Hays  Changqun Cao 《Applied Geochemistry》2010

In this study the abundances of several polycyclic aromatic hydrocarbons (PAHs Table 1, I–XXI) have been measured throughout three Permian/Triassic (P/Tr) sections from Meishan (South China), Kap Stosch area (East Greenland) and Peace River Basin (Western Canada). Dibenzothiophene (I) and dibenzofuran (II) were found to decrease in abundance just before or shortly after the P/Tr transition in all three sections while perylene (III) was observed to increase in abundance at the onset of the main extinction horizon (bed 25) in Meishan. Perylene has been attributed to a wood degrading fungal source and, therefore, it seems possible these phenomena are related to the demise of land plants. Further, distinct patterns of various combustion-derived PAHs occurring in each section imply that forest fire events occurred within the Late Permian and Early Triassic. In the Meishan section high amounts of combustion-derived PAHs [pyrene (IV), fluoranthene (V), benzo[a]anthracene (VI), benzofluoranthenes (sum, i.e. VII), benzo[a]pyrene (VIII), benzo[e]pyrene (IX) and coronene (X)] occur within bed 25, also containing ash attributed to the fallout from massive volcanic eruptions in Siberia and/or China.  相似文献   

Contribution of regional climate drivers to future winter sea-level changes in the Baltic Sea estimated by statistical methods and simulations of climate models     

Birgit H��nicke 《International Journal of Earth Sciences》2010,99(8):1721-1730

A statistical downscaling approach is applied to the output of five different global climate model simulations driven by twenty-first century future scenarios of greenhouse gas concentrations. The contribution of sea-level pressure (SLP) and precipitation changes to regional future winter sea-level changes is estimated for four Baltic sea-level stations by establishing statistical relationships between sea level as predictand and large-scale climate fields as predictors. Using SLP as predictor for the central and eastern Baltic Sea level stations, three climate models lead to statistically significant twenty-first century future trends in the range of the order of 1–2 mm/year. Using precipitation as predictor for the stations in the southern Baltic coast all five models lead to statistically significant trends with a range of the order of 0.4 mm/year. These numbers are smaller, but of the order of magnitude as the predicted global sea-level rise.  相似文献   

辽宁五龙金矿黄铁矿的热电性标型特征   总被引：2，自引：0，他引：2  

魏存弟  刘宗秀 《黄金地质》2001,7(2):6-10

黄铁矿是五龙金矿的主要载金矿物之一，热电性以P型为主，占总数的90.8%，变化范围为4.3-392.0uV/℃，N型占9.2%，变化范围为-28.6--177.1uV/℃；不同世代黄铁矿热电性不同，第一世代为P型，第二、三世代为P、N混合型；横向上从矿体到围岩；热电系数由小变大，As使其呈P型，而C0、Ni使其呈N型。  相似文献   

黑龙江省老柞山金矿床毒砂热电性研究     

魏存弟  周喜文  王秀平  于国兴 《吉林大学学报(地球科学版)》2001,31(2):132-135

毒砂是老柞山金矿主要载金矿物。早期与晚期成矿作用形成的毒砂 ,其热电性具明显差异 :早期毒砂热电系数为正值 ,平均 2 5 0 .3μV /℃ ,P型导电 ;晚期毒砂热电系数为负值 ,平均- 2 16 .9μV /℃ ,为N型导电。通过对不同成矿期以及同一样品中不同导型毒砂的热电性特征与成分关系的研究得出 :毒砂的热电性特征由As、S相对含量决定 ,若为富As型毒砂 ,则为P型导电 ,若为富S型毒砂 ,则为N型导电。  相似文献   

分布式仿真系统中环境场景的实时定位     

蒋定华  符冉迪  游代安  余旭初 《测绘学院学报》2001,(Z1)

分布式仿真系统中 ,各节点之间通过消息互相交流信息 ,3维地形虚拟场景通常在大量的仿真系统中作为重要的对象参与仿真。由于各个对象的参考坐标系之间存在差异。所以在 3维地形虚拟场景节点与系统中其他各节点之间进行消息交换时 ,存在一个坐标转换的问题。文中给出了一种坐标转换的快速算法 ,从而保证仿真过程中场景的实时定位  相似文献   

Boundary-layer observations over water and arctic sea-ice during on-ice air flow     

Burghard Brümmer  Birgit Busack  Heinrich Hoeber  Gottfried Kruspe 《Boundary-Layer Meteorology》1994,68(1-2):75-108

Observations made on 8 and 9 May 1988 by aircraft and two ships in and around the marginal ice zone of the Fram Strait during on-ice air flow under cloudy and cloud-free conditions are presented.The thermodynamic modification of the air mass moving from the open water to the ice over horizontal distances of 100–300 km is only a few tenth of a degree for temperature and a few tenth of a gram per kilogram for specific humidity. This is due to the small temperature differences between sea and ice surfaces. During the day, the ice surface is even warmer than the sea surface. The stably stratified 200–400 m deep boundary layer is often topped by a moisture inversion leading to downward fluxes of sensible as well as latent heat.The radiation and energy balance at the surface are measured as functions of ice cover, cloud cover and sun elevation angle. The net radiationR _Nis the dominating term of the energy budget. During the day, the difference ofR _Nbetween clear and overcast sky is only a few W/m² over ice, but 100–200 W/m² over water. During the night,R _Nover ice is more sensitive to cloud cover.The kinematic structure is characterized by strong shears of the longitudinal and the transversal wind component. The profile of the latter one shows an inflection point near the top of the boundary layer. Dynamically-driven roll circulations are numerically separated from the mean flow. The secondary flow patterns have wavelengths of about 1 km and contribute substantially to the total variances and covariances.  相似文献   

Characterization of sediments in an abandoned mining area; a case study of Mansfeld region,Germany   总被引：1，自引：0，他引：1  

Rainer?WennrichEmail author  Jürgen?Mattusch  Peter?Morgenstern  Klaus?Freyer  Hanns-Christian?Treutler  Hans-Joachim?St?rk  Lutz?Brüggemann  Albrecht?Paschke  Birgit?Daus  Holger?Weiss 《Environmental Geology》2004,45(6):818-833

The distribution of selected heavy metals, including some radionuclides, metalloids and non-metals was determined in stream sediments in a region influenced by abandoned copper mining and ore processing activities. A considerable amount of the ore processing waste with a very complex composition and highly elevated concentrations of zinc, sulfur, lead, copper, arsenic, and a lot of other elements in the range between 100 and 1,000 mg/kg (Sb, Mn, Ni, Cr, Cd, Hg, and Ag) was piled up on mine dumps. The dispersion of the pollutants originating from this source and their environmental impact were investigated. Both, sediments and original waste material were studied to indicate the pathways and the mobilization behavior of different pollutants. For this purpose, the process of the elution of pollutants by application of different fractionation schemes was studied. The capabilities of different analytical techniques are shown for the analysis of solid samples (X-ray fluorescence spectrometry, Gamma-spectrometry) and liquid ones (ICP-atomic emission spectrometry, ICP-mass spectrometry and different techniques of atomic absorption). Additionally, the coupling of ion chromatography and ICP-MS detection was used to study the distribution of arsenic species in the sediment cores of a lake which acts as a natural sink for the region.  相似文献