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11.
南海及周边部分地区特提斯构造遗迹:问题与思考 总被引:6,自引:1,他引:6
对全球二叠纪-三叠纪古气候特征的研究表明,东特提斯地区晚三叠世古气候标志具有带状分布的特征。北巴拉望地块卡拉棉群岛科龙岛的晚三叠世沉积中发育反映较干燥古气候特征的鲕状灰岩,因此在古气候特征方面,北巴拉望地块晚三叠世地层不能与华南和印支地块同期地层对比,而应该与印度地块北缘喜马拉雅地区(向西)和琉球群岛(向东)对比。根据该古气候分析,北巴拉望地块在晚三叠世时应该位于南部亚热带较干燥气候带内,其晚三叠世的古地理位置比印支地块更靠南。对南海及南海周边部分地特提斯构造遗迹的研究,将有助于深入了解南海北部陆缘区相关构造带的性质及正确恢复南海扩张之前该区的地质发展历史。南海北部陆缘区也是研究解决特提斯构造向东延伸问题以及特提斯构造-太平洋构造时空转化问题的关键地区。 相似文献
12.
Domenico Voltolina Leslie N. Brown Maurice G. Robinson 《Estuarine, Coastal and Shelf Science》1985,21(6):817-822
The results of eight sets of repeated observations on the vertical variations of the chlorophyll maximum layer in a shallow lagoon during a red tide show that these were more frequently hydrologically induced, rather than due to active vertical migrations of the red tide-forming organism. These results are discussed and compared to those existing in the literature, with special regard to the role of light and nitrogen in conditioning vertical migrations in red tide-forming dinoflagellates. 相似文献
13.
Sebastiano Calvo Gianfranco Lovison Maria Pirrotta Germana Di Maida Agostino Tomasello & Mariangela Sciandra 《Marine Ecology》2006,27(4):361-371
The relationship between flowering and growth performance of Posidonia oceanica (L.) Delile in meadows distributed along the south‐eastern coast of Sicily (Italy) was investigated by means of a statistical model (generalized linear mixed model) combined with the lepidochronological analysis. Over a 28‐year period, 67 floral stalk remains were observed. The highest flowering index was recorded in lepidochronological year 1998 (10.1%) and the Inflorescence Frequency per age showed a clear decrease corresponding to 15‐year‐old shoots. The sexual reproductive event had positive effects on rhizome elongation (cm year?1) and leaf production (no. leaves year?1) in the same flowering year, whilst no effect on the rhizome production (mg year?1) was observed. Rhizome growth variables showed significant negative lagged responses in the two years following flowering. On the whole, we calculated that the effect exerted by flowering, in terms of loss on rhizome elongation and production, was about 27% and 38%, respectively. Although it has been demonstrated that recovery from the stress induced by sexual reproduction is limited to the two years after flowering, the magnitude of the reproductive cost may become quite considerable especially in comparison with the whole lifespan of individual shoots. 相似文献
14.
A study of sea surface wave propagation and its energy deformation was carried out using field observations and numerical experiments over a region spanning the midshelf of the South Atlantic Bight (SAB) to the Altamaha River Estuary, GA. Wave heights on the shelf region correlate with the wind observations and directional observations show that most of the wave energy is incident from the easterly direction. Comparing midshelf and inner shelf wave heights during a time when there was no wind and hence no wave development led to an estimation of wave energy dissipation due to bottom friction with corresponding wave dissipation factor of 0.07 for the gently sloping continental shelf of the SAB. After interacting with the shoaling region of the Altamaha River, the wave energy within the estuary becomes periodic in time showing wave energy during flood to high water phase of the tide and very little wave energy during ebb to low water. This periodic modulation inside the estuary is a direct result of enhanced depth and current-induced wave breaking that occurs at the ebb shoaling region surrounding the Altamaha River mouth at longitude 81.23°W. Modelling results with STWAVE showed that depth-induced wave breaking is more important during the low water phase of the tide than current-induced wave breaking during the ebb phase of the tide. During the flood to high water phase of the tide, wave energy propagates into the estuary. Measurements of the significant wave height within the estuary showed a maximum wave height difference of 0.4 m between the slack high water (SHW) and slack low water (SLW). In this shallow environment these wave–current interactions lead to an apparent bottom roughness that is increased from typical hydraulic roughness values, leading to an enhanced bottom friction coefficient. 相似文献
15.
在南海北部利用地球化学方法作为油气勘探的一种辅助手段。在6个航次中采集了沉积物、底层海水及海面大气样品,测定了近50种化探指标,并采用稳健统计方法进行了数据处理和异常圈定。化探结果在油气藏上方发现了清晰的、具不同指标组合的综合化探异常,与邻近空构造形成鲜明的对照。圈闭顶部的块状异常和圈闭周绿的环状、半环状异常是下伏油气藏的良好指示,而剖面上呈锯齿状、平面上呈线状的异常则与断裂带有关。实践表明,建立已知油气藏上方的化探异常模式及解剖已知空构造上方的地球化学特征对于指导本区或邻区的化探异常评价是十分必要的。 相似文献
16.
Sixteen mucilages sampled in the Adriatic and Tyrrhenian seas during 1999–2001 were characterised using spectroscopic [Fourier transform infrared spectroscopy (FTIR); colorimetric], chromatographic [thin-layer chromatography (TLC)], and elemental analysis techniques. Most samples contained comparable fractions of organic and inorganic compounds, with the exception of a few samples where the inorganic fraction was greater than the organic fraction. Carbohydrates were important in the samples rich in organic matter, while carbonate and silica (quartz and biogenic silica) were the most important constituents of the inorganic fraction. Carbonate and silica were the only important constituents of the samples with a very low organic content.According to chemical analyses, mucilage aggregates show the typical structure of humin—the insoluble fraction of the humic substance. Classification of mucilage samples as humin-like compounds, together with a reexamination of the factors involved in the formation of organic aggregates in marine environment, has led to the formulation of a reasonable hypothesis for mucilage formation. 相似文献
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18.
Alessandro Buccolieri Giovanni Buccolieri Nicola Cardellicchio Angelo Dell'Atti Antonella Di Leo Antonella Maci 《Marine Chemistry》2006,99(1-4):227
Al, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Ti and Zn concentrations have been determined in surface sediment samples collected in the Taranto Gulf (Ionian Sea, Southern Italy) in order to evaluate their levels and spatial distribution in this important area of the Mediterranean Sea. For various metals, the geoaccumulation index has been calculated as a criterion to assess if their concentrations represent contamination levels or can be considered as background levels. The results show that metals concentrations in sediments can be considered near the background levels found in the Mediterranean Sea.Analytical results have been elaborated by using a Geographical Information System (GIS) software to show metals accumulation areas. Using multivariate statistical analysis, we evaluate the possibility to distinguish the sampling stations, in relation to their geographical position. Results have showed metals distribution in the Taranto Gulf is principally influenced by industrial and urban wastes, located mostly in the northern coastal area of the Ionian Sea. Rivers in the Basilicata region and prevailing anticlockwise marine currents are further factors influencing metal accumulation in sediments. 相似文献
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20.
M. Cristina Fossi Silvia Casini Letizia Marsili Stefania Ancora Gabriele Mori Giovanni Neri Antonella Ausili Teresa Romeo Alessandra Moscatelli Giuseppe Notarbartolo Di Sciara 《Marine Ecology》2002,23(S1):184-189
Abstract. Endocrine Disrupting Chemicals (EDCs) have the potential to alter hormone pathways that regulate reproductive processes in wildlife and fisheries. In this research the unexplored hypothesis that Mediterranean top predator species (such as large pelagic fish and marine mammals) are potentially at risk due to EDCs is investigated. In the Mediterranean environment, top predators accumulate high concentrations of polyhalogenated aromatic hydrocarbons (PHAHs) and toxic metals, incurring high toxicological risk. Here we illustrate the need to develop sensitive biomarkers for evaluation of toxicological risk in top marine predators (Xiphias gladius, Thunnus thynnus thynnus) and non-lethal techniques, such as non-destructive biomarkers, for the hazard assessment of threatened species exposed to EDCs, such as marine mammals ( Stenella coeruleoalba, Tursiops truncatus, Delphinus delphis and Balaenoptera physalus ). 相似文献