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Growth of the bluenose, Hyperoglyphe antarctica (Carmichael, 1818) from the lower east coast, North Island, was determined by counting growth check rings in otoliths. One growth check ring appeared to be laid down each year, so this technique is probably valid for aging bluenose. Female fish had a significantly higher growth rate than males. Comparisons of samples from three sites indicated no significant regional differences in growth. The von Bertalanffy parameters L8,K, and t0 fitted to back‐calculated fish lengths were, respectively, 81.1 cm, 0.308, ‐0.627 for males, and 86.1 cm, 0.308, ‐0.384 for females.  相似文献   

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渭南阎村W7孔岩心样品的古地磁学研究   总被引:5,自引:0,他引:5  
对渭南阎村W7孔岩心地层样品的磁性地层学研究,确定了黄土组、三门组地层的时代。这一地区的黄土/古土壤层形成始于松山反极性时晚期,约为1.1MaB.P.。按照地层样品的剩磁特征和岩性特征对黄土/古土壤层作更精细地划分,这一地区的黄土/古土壤层相当于马兰黄土、离石黄土层,缺失午城黄土。地层的剩磁极性资料表明,三门组地层形成于高斯极性时晚期—松山极性时中期,按照奥尔都维正极性亚时为第四纪下限的年代准则,确定三门组地层的时代为晚上新世。 W7孔岩心的地层样品的剩磁极性序列与已有的地磁极性年代表的磁极性序列大体相当,本项研究也揭示了二个短周期极性事件的存在,位于第5黄土层的安比拉事件(Emperor)发生的年代约为0.445—0.458Ma B.P.。位于第9黄土层的后期哈拉米洛事件(Post-Jaramillo)发生的年代约为0.77—0.81MaB.P.。 磁性地层学研究表明这一地区在松山反极性时中晚期出现过沉积间断,持续时约0.5Ma。 根据W7孔的地层学研究认为,选择以奥尔都维正极性亚时末期的年代(1.60MaB.P.)作为第四纪下限是有利于第四纪地层的划分和对比的。  相似文献   

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The major elements, trace elements, K-Ar age and Sr-Nd-Pb isotopic systems of the Cenozoic volcanic rocks in Daheishan Island and Cishan, Penglai, Shandong Province are measured. The volcanic rocks ( olivine-nephelinite and nepheline-basanite ) in DaheishanIsland erupted periodically in an interval of 0.32 Ma, from 8.72 Mm 8.39 Ma, 8.08 Ma to 7.73Ma. The volcanic rocks are all rich in light REEs. They are similar to the OIB-type alkali basalt in the trace elements normalized model by primordial mantle: rich in high field elements such as Nb and Ta, and imcompatible elements such as Cs, Rb, Ba, Th, U. The volcanic rocks show a depletion of K and Rb elements. It is suggested by the trace elements that the olivine-nephelinite in Daheishan Island is originated fi‘om deep resources under the continental mantle, ε Nd (0) values of the volcanic rocks in Daheishan Island and Cishan are 5.31 - 8.51 and 7.33 respectively, suggesting that the volcanic rocks are from the depleted mantle resources, which have higher Sm/Nd ratios than the CHUR. ^143Nd /^144Nd ratios of Daheishan Island olivine-nephelinite and Cishan alkali basalts are 0.512 910 - 0.513 074 and 0.513 014 resoeetivelv. The ^87Sr /^86Sr of Daheishan lsland volcanic rocks are lower than that of Cishan, 0.703 427 - 0.703 482 and 0.703 895 respectively. The Daheishan Island olivinenephelinite has the Pb isotopic values as follows: ^206Pb /^204pb= 18.028 9 ~17.972 8,^207Pb /^204Pb= 15,435 8 - 15.402 2 and ^208Pb /^204Pb=38.087 6 - 37.997 5, lower than those of Cishan basanite. The Cishan basanite has ^206Pb / ^204Pb = 18.240 1, ^208Pb /^204Pb = 15.564 5 and ^208Pb /^204Pb=38.535. The authors suggest that the olivine-nephelinite in Daheishan Island is similar to the E-type MORB or Hawaii OIB, and the alkali basalts in Cishan similar to the Kerguelen OIB. The dominant mantle components of DM PREMA and perhaps DM( Dupal type ) are the dominant mantle components for volcanic rocks in Daheishan Island and Cishan. The PREMA component plays an important role.  相似文献   

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广西英罗港红树植物木榄种群年龄结构的研究   总被引:1,自引:0,他引:1  
在广西英罗港红树林区(21°28′~21°37′N、109°37′~109°47′E)选择和设置了4个有代表性的木榄群落样地,测量木榄胸径大于等于2.5 cm的所有个体的株高、胸径、冠幅、坐标位置等,同时随机选择15~30株木榄个体,在离地面30~50 cm处钻取木芯以确定其年龄。采用回归方程定量分析木榄个体年龄与其胸径之间的关系。以5 a为1个年龄级,对个体年龄进行年龄级的划分,并构建种群年龄结构图。根据个体的年龄大小和坐标位置,采用Matlab软件来绘制种群年龄分布的等值线图,由此分析种群年龄的水平空间结构特征。结果表明,木榄个体年龄与其胸径之间的线性回归方程显著。根据这些方程来估算木榄种群其它个体的年龄,得出多数群落的木榄种群是以年龄为20~35 a的个体为主,占个体总数的65%~80%;少数群落的木榄种群以年龄为5~15 a的个体居多,约占75%;除少数群落外,多数群落的木榄种群缺乏树龄为10 a以下的个体。根据年龄结构和存活曲线分析,木榄种群属于增长型,最大个体年龄小于70 a。在水平空间上,木榄种群的年龄结构呈现不同程度的、不规则的斑块状镶嵌分布,即是由不同年龄阶段的个体斑块镶嵌而成。处于不同年龄阶段的各种个体群斑块相互镶嵌,形成了种群的空间格局。为了维持木榄种群的可持续发展,必须增加群落更新层的木榄个体的数量。采取的主要措施是进行人工抚育,通过抚育使胸径较大的个体数量增加,自然枯损率降低,促进木榄种群的自然更新进程。  相似文献   

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四、“柳夼红层”的物质组成 本文(Ⅰ)所列“柳夼红层”剖面地层层序进行了物相、粒度、X衍射和ESR年代测定,其结果与宏观观察结果相吻合。 “柳夼红层”,剖面序列,层位和时代有所不同,成因有别,而在物质组成上却大同小异,表现出从晚更新世早期至全新世地层,其物源供应基本相同,都来源于燕山期斑状花岗岩的风化破碎产物,属就地近源搬运。  相似文献   

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The age structure, annual growth, length-weight relationship, reproduction and other aspects of the general biology in Boyer's sandsmelt, Atherina boyeri, from the Severn estuary, have been studied for the period 1974–1977. The results are compared with those found in previous investigations of A. boyeri from more southerly waters.  相似文献   

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Surface waves are the roughness element of the ocean surface. The parameterization of the drag coefficient of the ocean surface is simplified by referencing to wind speed at an elevation proportional to the characteristic wavelength. The dynamic roughness is analytically related to the drag coefficient. Under the assumption of fetch limited wave growth condition, various empirical functions of the dynamic roughness can be converted to equivalent expressions for comparison. For datasets covering a wide range of the dimensionless frequency (inverse wave age), it is important to account for the variable rate of wave development at different wave ages. As a result, the dependence of the Charnock parameter on wave age is nonmonotonic. Finally, the analysis presented here suggests that the significant wave steepness is a sensitive property of the ocean surface and a single variable normalization of the dynamic roughness using a wavelength or wave height parameter actually produces more robust functions than bi-variable normalizations using wave height and wave slope.  相似文献   

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本文报道了深沪湾古森林树桩和牡蛎礁的牡蛎壳的~(14)C测年数据,表明它们分别为距今7000~8000a和9335±199a,属于中全新世早期和早全新世的产物。  相似文献   

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