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南黄海和东海北部陆架重矿物组合分区及来源 总被引:17,自引:0,他引:17
利用大洋-50型海底取样器,在南黄海和东海北部陆架(125°E以西)海上调查获取了海底表层沉积物样品,其中包括1998年以来"黄东海地质地球物理补充调查"和"中韩黄海沉积动力学与古环境演变"2项研究所获得的样品共380个,选取0.063~0.125mm粒级的沉积物,进行碎屑矿物分析,最后选出9个代表性的优势重矿物种的数据为变量,利用Q型聚类(分层聚类)的数学方法,进行聚类组合,在数学统计的基础上,将研究区划分出4个重矿物组合区。客观地反映出黄河物质、长江物质和原地物质的影响范围,同时也体现出物质来源和水动力以及海底风化作用对重矿物分布的影响程度和范围,因而可以得出,在一定的范围内陆架表层沉积物中的重矿物具有趋同的演化效应。 相似文献
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S. García-Gil E. de Blas N. Martínez-Carreño J. Iglesias R. Rial-Otero J. Simal-Gándara A.G. Judd 《Estuarine, Coastal and Shelf Science》2011
Ría de Vigo is a river valley flooded by the sea, with a bay (San Simón Bay) at its innermost part. The accumulation of Holocene sediment in San Simón Bay has been studied by the integration of 1) large scale high resolution seismic data, and 2) detailed geochemical analysis of a gravity core. In San Simón Bay the majority of the seismic records are obscured by acoustic turbidity which represents gassy sediments, but on records from Rande Strait it is possible to distinguish two Quaternary seismic sequences; an Upper Pleistocene sequence (SQ1) and a Holocene sequence (SQ2). Only SQ2 is recognized in San Simón Bay where it is comprised of two seismic units; the upper unit represents the HST sediment, i.e. the period of highest sea level. A gravity core taken within the gassy zone at 10 m water depth provided 3.55 m of fine-grained sediments (muds) from the youngest seismic unit (4 m thick). Geochemical analysis show high values (4 to 10%) of TOC. Sediment and porewater analyses indicate a distinct sulphate–methane transition zone (SMTZ) between 60 and 80 cm where sulphate is depleted (to <1.7 mM) and methane increases (to >0.4 mM). The top of the acoustic turbidity (the gas front) at 80 cm corresponds to the lower limit of the SMTZ. The methane cannot have been derived from the underlying metamorphic and granitic rocks, but was probably derived by microbial degradation of the organic matter in the Holocene sediments. We estimate that the sediments of the Bay contain approximately 1.8 × 106 m3 of organic carbon and 275 ton of methane. 相似文献
96.
海洋是多尺度强迫-耗散系统,机械能主要在大尺度输入,在小尺度耗散。在大、中尺度运动的能量向小尺度湍流传递过程中,内波扮演着重要角色。内波的生成和破碎可打破海洋动力平衡,而在陆架区,内波(主要是内孤立波)的浅化演变与耗散则是驱动湍流混合的关键过程。通过长期的理论、观测与数值模拟研究,目前已认识到内波浅化过程中主要发生如下演变:波形调制、极性转变、裂变、破碎与耗散。相较于直接发生破碎,浅化演变过程中的裂变及其引发的剪切不稳定和对流不稳定是内孤立波在陆架区的主要耗散机制,显著调制陆架区的跃层混合。从能量串级的角度讲,内孤立波浅化裂变为动力不稳定的高频内波是潮能串级的重要通道。本文简要回顾南海北部陆架区内波的研究历史,并着重总结内波在陆架区演变与耗散机制的研究进展。 相似文献
97.
ZHENG Lianming LIN Yuanshao LI Shaojing CAO Wenqing XU Zhenzu HUANG Jiaqi 《海洋学报(英文版)》2009,28(1):109-115
Aequorea taiwanensis, a new hydrozoan species from the Taiwan Strait was described using morphological and molecular characteristics. Both morphological and mitochondrial cytochrome oxidase subunit I (mtCOI) data supported A. taiwanensis n. sp. as a valid species. Sequence divergence and genetic distance of A. taiwanensis n. sp., A. papillata and A. conica were analysed based on the mtCOI gene sequences. The mtCOI sequences from these three species of the genus Aequorea showed high variation frequency, with sequence divergences ranging from 9.10% to 11.9%, and pairwise genetic distances ranging from 0.097 to 0.130. MtCOI sequence analysis provided diagnostic molecular systematic characteristics for accurate identification and discrimination of the species of Aequorea or their populations, and will be used to resolve evolutionary relationships among them.It was suggested that 10%—20% pairwise mtCOI sequence differences indicated the specieslevel divergence among congeneric species in the Hydromedusae. 相似文献
98.
A class of coupled system of the E1 Ni(n)o/La Ni(n)a-Southern Oscillation (ENSO) mechanism is studied. Using the perturbed theory, the asymptotic expansions of the solution for ENSO model are obtained and the asymptotic behavior of solution for corresponding problem is considered. 相似文献
99.
基于高分辨率的单道地震和多波束测深数据,识别并对比了东海陆架中部同一海区相距20余万年的层U14和层U2两期沙脊群,其中层U14期沙脊属于埋藏沙脊,位于东海海底以下90 m深处,推测属于距今320~200 ka的海侵体系域(TST),沙脊顶界面是该期海侵的最大洪泛面(MFS);层U2期沙脊位于东海陆架,属于衰退沙脊,系末次盛冰期(LGM)以来的TST,顶界面是LGM以来的MFS。尽管两期沙脊形成年代相距20余万年,地层层位相距近90 m,但是沙脊群总体走向一致,表明距今2×105 a以来东海陆架潮波基本格局稳定。从层U2期可识别出4个亚期沙脊,通过多波束海底地形图可识别出4组走向的沙脊,多亚期、多走向沙脊是LGM以来海平面阶梯状波动在海底地形演变过程中的响应证据。 相似文献
100.
Methylmercury production in sediments of Chesapeake Bay and the mid-Atlantic continental margin 总被引:3,自引:0,他引:3
Methylmercury (MeHg) concentration and production rates were studied in bottom sediments along the mainstem of Chesapeake Bay and on the adjoining continental shelf and slope. Our objectives were to 1) observe spatial and temporal changes in total mercury (HgT) and MeHg concentrations in the mid-Atlantic coastal region, 2) investigate biogeochemical factors that affect MeHg production, and 3) examine the potential of these sediments as sources of MeHg to coastal and open waters. Estuarine, shelf and slope sediments contained on average 0.5 to 1.5% Hg as MeHg (% MeHg), which increased significantly with salinity across our study site, with weak seasonal trends. Methylation rate constants (kmeth), estimated using enriched stable mercury isotope spikes to intact cores, showed a similar, but weaker, salinity trend, but strong seasonality, and was highly correlated with % MeHg. Together, these patterns suggest that some fraction of MeHg is preserved thru seasons, as found by others [Orihel, D.M., Paterson, M.J., Blanchfield, P.J., Bodaly, R.A., Gilmour, C.C., Hintelmann, H., 2008. Temporal changes in the distribution, methylation, and bioaccumulation of newly deposited mercury in an aquatic ecosystem. Environmental Pollution 154, 77] Similar to other ecosystems, methylation was most favored in sediment depth horizons where sulfate was available, but sulfide concentrations were low (between 0.1 and 10 μM). MeHg production was maximal at the sediment surface in the organic sediments of the upper and mid Bay where oxygen penetration was small, but was found at increasingly deeper depths, and across a wider vertical range, as salinity increased, where oxygen penetration was deeper. Vertical trends in MeHg production mirrored the deeper, vertically expanded redox boundary layers in these offshore sediments. The organic content of the sediments had a strong impact on the sediment:water partitioning of Hg, and therefore, on methylation rates. However, the HgT distribution coefficient (KD) normalized to organic matter varied by more than an order of magnitude across the study area, suggesting an important role of organic matter quality in Hg sequestration. We hypothesize that the lower sulfur content organic matter of shelf and slope sediments has a lower binding capacity for Hg resulting in higher MeHg production, relative to sediments in the estuary. Substantially higher MeHg concentrations in pore water relative to the water column indicate all sites are sources of MeHg to the water column throughout the seasons studied. Calculated diffusional fluxes for MeHg averaged 1 pmol m− 2 day− 1. It is likely that the total MeHg flux in sediments of the lower Bay and continental margin are significantly higher than their estimated diffusive fluxes due to enhanced MeHg mobilization by biological and/or physical processes. Our flux estimates across the full salinity gradient of Chesapeake Bay and its adjacent slope and shelf strongly suggest that the flux from coastal sediments is of the same order as other sources and contributes substantially to the coastal MeHg budget. 相似文献