阿尔丹—斯塔诺夫地区右线性构造聚矿构造     

V. V. Vinogradov  陈硕彦 《西北地质》1986,(2)

阿尔丹一斯塔诺夫地区是苏联最大的早前寒武纪地层出露地区之一。这套地层可以划分为阿尔丹和斯塔诺夫两个褶皱系,二者在构造面貌、变质作用级别等方面均有差异。迄今对二者的关系知道很少,故以构造—变质面貌将二者彼此分开。然而地学界多认为它们属太古界无疑。因此,整个地区应是一个太古代固结区。在早、中元古代时期,该区破裂为一个被缝合槽分隔的断块系。晚元古代时期,处于地台快速发育阶段。随后在古、中、新生代时期经受了各种构造、岩浆活化作用的干挠。  相似文献   

冰川学和冰期     

A lbert V.Carozzi  邓金宪 《世界地质》1987,(3)

冰川学的开始从Josias Simler(1530—1576)、Johann Heinrich Hottinger(1680—1733)特别是Johann Jacoh Scheuchzer(1672—1733)对瑞士的阿尔卑斯式(Alpine)冰川的早期观察,冰川学就开始了(Simler,1574; Hottinger,1706;Scheuchzer,1723)。直到十八世纪中叶,才有少数几位自然科学家勇敢地登上了展现冰的壮观景象的高山。Simler和Scheuchzer都认为冰川的形成是雪在高阿尔卑斯山(Alps)堆积的结果。Schen chzer区分出永久冻雪和冰川,并且阐述了由于产生冰川的山岳特征不同而冰川互不相同。他证实了Hottinger的冰川层叠、前进和后退的观察,并且说明了由于渗透于冰裂隙中的水冻结膨胀引起的冰川运动。这种观点后来成为众所周知的膨胀理论。  相似文献   

方解石和硬石膏结构中的硼——能否作为成矿作用的指示标志?     

V.V.Rudnev  L.T.Rakov  V.Malinko  靳娟娟 《世界地质》1987,(3)

我们已积累了大量值得考虑的有关硼在各种岩石中(包括那些对硼的成矿作用有经济价值的岩石)的分布数据。石灰岩中硼的含量范围为0.5～300ppm,白云岩中硼的含量范围为5—700ppm,硼主要以泥质混合物或分散细晶硼矿物的形式存在。化学性质较纯的粗粒结晶方解石一般不含硼,硼若存在,其数量至少要超过十分之几ppm。变质岩中的硼含量要比同类岩石中受蚀变的硼含量少。对于具有和不具有硼矿化阼用的镁质和钙质的矽卡岩,矿物的空间分布和局部射线(x)分析的研究表明,在分析灵敏度的极限内(几个ppm)测得方解石结构中缺少硼。  相似文献   

中纬度锋系的中尺度结构     

Peter V. Hobbs  高良成 《气象科技》1983,(3):36-40

本文对温带气旋中尺度云和降水的动力学、构成情况和结构的观测研究作了回顾。一般说来,大的中尺度降水带由最强烈的降水区构成,这种中尺度降水带分为六种类型:暖锋型、暖区型、宽广冷锋型、狭窄冷锋型、锋前冷空气爆流(Cold—Surge)型及锋后型。通常,这些降水带内的降水较多是小的中尺度。本文对大的中尺度和小的中尺度的可能机制进行了判别。  相似文献   

Human-driven topographic effects on the distribution of forest in a flat,lowland agricul-tural region简   总被引：1，自引：0，他引：1  

Mette V. ODGAARD  Peder K. B CHER  Tommy DALGAARD  Jesper E. MOESLUND  Jens-Christian SVENNING 《地理学报(英文版)》2014,24(1):76-92

Complex topography buffers forests against deforestation in mountainous regions. However, it is unknown if terrain also shapes forest distribution in lowlands where human impacts are likely to be less constrained by terrain. In such regions, if important at all, to- pographic effects will depend on cultural-historical factors and thus be human-driven （an- thropogenic） rather than natural, except in regions where the general climate or extreme soils limit the occurrence of forests. We used spatial regression modeling to assess the extent to which topographic factors explain forest distribution （presence-absence at a 48x48 m resolu- tion） in a lowland agricultural region （Denmark, 43,075 km2） at regional and landscape scales （whole study area and 10x10 km grid cells, respectively）, how landscape-scale for- est-topography relationships vary geographically, and which potential drivers （topographic heterogeneity, forest cover, clay content, coastal/inland location） determine this geographic heterogeneity. Given a moist temperate climate and non-extreme soils all landscapes in Denmark would naturally be largely forest covered, and any topographic relationships will be totally or primarily human-driven. At regional scale, topographic predictors explained only 5% of the distribution of forest. In contrast, the explanatory power of topography varied from 0%-61% at landscape scale, with clear geographic patterning. Explanatory power of topog- raphy at landscape scale was moderately dependent on the potential drivers, with topog- raphic control being strongest in areas with high topographic heterogeneity and little forest cover. However, these conditioning effects were themselves geographically variable. Our findings show that topography by shaping human land-use can affect forest distribution even in flat, lowland regions, but especially via localized, geographically variable effects.  相似文献   

不同含水量亚黏土的崩解特性实验研究   总被引：2，自引：1，他引：1  

张泽  马巍  PENDIN Vadim V  张中琼  何瑞霞 《水文地质工程地质》2014,(4):104-107

为了分析土的初始含水量与其崩解性的相关关系,选取了一种高孔隙率、粉黏粒含量较高,且不具有湿陷性的轻质亚黏土作为研究对象。对7组不同含水量的土样品进行崩解试验,发现随着初始含水量的增大,其崩解时间越长,初始含水量接近于风干含水量的土样品能够完全崩解,当初始含水量为天然含水量时,土样品崩解的过程是由"内"到"外",由整体崩解为大块,然后再崩解为更小的块状;当初始含水量为风干含水量时,土样品崩解过程是由"外"到"内"以鳞片状一层一层地崩解;随着土样初始含水量的增大其崩解速率逐渐变小,初始含水量接近风干含水量时,土样在完全崩解的过程中,其崩解敏感性较强;初始含水量接近天然含水量的情况下,在不完全崩解的过程中,其崩解敏感性较弱。  相似文献   

Polychlorinated biphenyls and DDT residues distribution in sediments of Cortiou (Marseille, France)   总被引：1，自引：0，他引：1  

Wafo E  Sarrazin L  Diana C  Schembri T  Lagadec V  Monod JL 《Marine pollution bulletin》2006,52(1):104-107

  相似文献   

Validation of soft bottom benthic habitats identified by single-beam acoustics     

Freitas R  Sampaio L  Oliveira J  Rodrigues AM  Quintino V 《Marine pollution bulletin》2006,53(1-4):72-79

Acoustic diversity charts were produced for a Portuguese soft bottom mid-shelf area, depth from 30 to 90 m, using a single-beam echo sounder coupled to the acoustic systems QTC VIEW Series IV and V. A similar acoustic pattern was identified by both systems, which, after ground-truth interpretation based in available sediment and biological data, established a preliminary spatial distribution model of the benthic habitats in this coastal area. However, some of the acoustic areas were interpreted using one or very few sediment and benthic samples. A specific validation survey was conducted a posteriori, in which the positioning of the sediment and benthic community sampling sites was based on the acoustic diversity previously identified. The results clearly confirm the benthic habitats distribution model suggested by the acoustic method, indicating a high potential for the use of such approach in the identification and mapping of large-scale soft bottom coastal shelf habitat diversity.  相似文献   

Scientific management of Mediterranean coastal zone: a hybrid ocean forecasting system for oil spill and search and rescue operations     

Jordi A  Ferrer MI  Vizoso G  Orfila A  Basterretxea G  Casas B  Alvarez A  Roig D  Garau B  Martínez M  Fernández V  Fornés A  Ruiz M  Fornós JJ  Balaguer P  Duarte CM  Rodríguez I  Alvarez E  Onken R  Orfila P  Tintoré J 《Marine pollution bulletin》2006,53(5-7):361-368

The oil spill from Prestige tanker showed the importance of scientifically based protocols to minimize the impacts on the environment. In this work, we describe a new forecasting system to predict oil spill trajectories and their potential impacts on the coastal zone. The system is formed of three main interconnected modules that address different capabilities: (1) an operational circulation sub-system that includes nested models at different scales, data collection with near-real time assimilation, new tools for initialization or assimilation based on genetic algorithms and feature-oriented strategic sampling; (2) an oil spill coastal sub-system that allows simulation of the trajectories and fate of spilled oil together with evaluation of coastal zone vulnerability using environmental sensitivity indexes; (3) a risk management sub-system for decision support based on GIS technology. The system is applied to the Mediterranean Sea where surface currents are highly variable in space and time, and interactions between local, sub-basin and basin scale increase the non-linear interactions effects which need to be adequately resolved at each one of the intervening scales. Besides the Mediterranean Sea is a complex reduced scale ocean representing a real scientific and technological challenge for operational oceanography and particularly for oil spill response and search and rescue operations.  相似文献   

PAH transport by sinking particles in the open Mediterranean Sea: a 1 year sediment trap study   总被引：1，自引：0，他引：1  

Bouloubassi I  Méjanelle L  Pete R  Fillaux J  Lorre A  Point V 《Marine pollution bulletin》2006,52(5):560-571

One year time series of sinking particles were collected at two depths in the open Mediterranean Sea and analysed for polycyclic aromatic hydrocarbons (PAH). Average total PAH concentrations were 593+/-284 ng g(-1) at 250 m and 551 +/- 198 ng g(-1) at 2850 m. Total PAH fluxes averaged 73 +/- 58 ng m(-2) d(-1) at 250 m and 53 +/- 39 ng m(-2) d(-1) at 2850 m. Contamination levels and, thus, exposure of marine organisms to PAH are comparable in surface and deep waters. Deep waters appear as a significant, yet overlooked, PAH sink. PAH temporal patterns show noticeable seasonality. This is partly due to varying levels of specific components such as the winter increase of pyrolytic PAH. Downward transport processes and the nature of sinking particles also impact on PAH fluxes, as inferred during periods of increasing productivity. Different phase-associations and interactions with particulate organic carbon for low-MW fossil PAH and high-MW pyrolytic PAH influence their downward transport efficiency.  相似文献