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81.
82.
锥形海山是马里亚纳弧前区非火山成因的海山。它是由俯冲的太平洋板块对仰冲板块的上推作用,地壳下的上地幔物质底辟侵入的结果。海山顶部的岩石是由蛇纹石化超镁铁质方辉橄榄岩组成。其主要矿物成分为斜方辉石、橄榄石、尖晶石、磁铁矿、蛇纹石和碳酸盐。手标本呈显晶质块状构造,薄片中呈粒状、残留状、筛网状及斑状变晶结构。岩石化学特征表现为:低Si和Al,高M/F值,含水,亏损了所有过渡金属。岩石的成因属超基性岩浆直接结晶,后经海水的参入,在热液作用下普遍发生蛇纹石化和碳酸盐化。 相似文献
83.
庵东浅滩沉积分带和沉积速率 总被引:4,自引:0,他引:4
杭州湾南岸的庵东浅滩具有地貌特征、沉积类型和沉积构造各异的三个沉积相带。垂向沉积带为潮滩沉积体的盖层,以泥滩、粘土质粉砂和薄砂泥交互层为特征;改造带位于中低潮位线附近,以粉砂滩、潮沟系统、粉砂沉积和沙波层理为特征;横向沉积带为潮滩堆积体的基础,以滩坡、粉砂及细砂质粉砂沉积、冲刷-充填构造为特征。据潮汐韵律层的统计,庵东浅滩沉积速率的短周期分量,常态条件下为每半日潮周期0.1~2.0cm,异常条件下可达每半日潮周期4~64cm。沉积速率的长周期分量,据地形对比和~(210)Pb推算,垂向沉积带为2~4.5cm/a;改造带中的粉砂滩为2.1~4.5cm/a,潮沟影响范围内为1~10~1cm/a量级;横向沉积带则以高于50cm/a的高沉积速率和变幅为主。近10年来,该浅滩的年淤积量为6×10~7t/a,其中85%集中于横向沉积带。 相似文献
84.
Taxonomy and ultrastructure of five species of Tetraselmis (Prasinophyceae) isolated from China seas
INTRODUCTIONThegenusTetraselmisStein ( 1 878)isagreenflagellates (Prasinophyceae)thatconsistsofmanymarineaswellasafewfreshwaterspecies .Marinespeciesoftenoccurindensepopula tionscausingbloomsintidepoolsorbays ,therebybeingimportanttoanunderstandingofthedynam… 相似文献
85.
On the basis of the wave energy balance equation, the response model of mean directions of locally wind-generated waves in slowly turning wind fields has been derived. The results show that in a homogeneous field, the time scale of the response is not only related to the rate of wave growth, but also to the directional energy distribution and the angle between the wind direction and the mean wave direction. Furthermore, the law of change in the mean wave direction has been derived. The numerical computations show that the response of wave directions to slowly turning wind directions can be treated as the superposition of the responses of wave directions to a series of sudden small-angle changes of wind directions and the turning rate of the mean wave direction depends on the turning rate and the total turning angles of the wind direction. The response of wave directions is in agreement with the response for a sudden change of wind directions if the change in wind directions is very fast. Based on the no 相似文献
86.
The oceans have rich resources of microbes. In recent years, searching for antibiotic of new structure and special biological activity from marine microbes has received great attention. This paper reports the results of the studies on the distribution and the antibacterial properties of Streptomyces in the intertidal zone of Southern Fujian. These studies have important significance to further investigate 相似文献
87.
88.
Recently, some results have been acquired with the Monte- Carlo statistical experiments in the design of ocean en gineering. The results show that Monte-Carlo statistical experiments can be widely used in estimating the parameters of wave statistical distributions, checking the probability model of the long- term wave extreme value distribution under a typhoon condition and calculating the failure probability of the ocean platforms. 相似文献
89.
By analysing the scatter diagrams of characteristic the wave height H and the period T on the basis of instrumental data from various ocean wave stations, we found that the conditional expectation and standard deviation of wave period for a given wave height can be better predicted by using the equations of normal linear regression rather than by those based on the log- normal law. The latter was implied in Ochi' s bivariate log-normal model(Ochi. 1978) for the long-term joint distribution of H and T. With the expectation and standard deviation predicted by the normal linear regression equations and applying proper types of distribution, we have obtained the conditional distribution of T for given H. Then combining this conditional P(T / H) with long-term marginal distribution of the wave height P(H) we establish a new parameterized model for the long-term joint distribution P(H,T). As an example of the application of the new model we give a method for estimating wave period associated with an extreme w 相似文献
90.
The vertical migration of diatoms in mud-flats was studied in littoral of Xibian, Longhai County and Xiao'ao, Lianjiang County, the dominant species being Gyrosigma spencerii and Hantzschia virgata respectively. Both light and tide are important factors affecting the vertical migration of diatoms. With the advent of tide, the diatom community disappears from the surface. It reappears gradually when exposed to light. In the dark, the diatoms never appear in great quantity on the surface in laboratory or in littoral. Whether in the light or in the dark, the diatoms aggregate in maximum numbers in the upper 2 mm of the sediment. But when the tide has covered the sediments for 4 hr, Hantz. virgata penetrates the mud down to a depth of 14 mm, Gy. spencerii, 12 mm. We have found that Gy. spencerii posseses phototaxis, but no tide rhythm and no day-night rhythm in our laboratory. 相似文献