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61.
渤海的地质演化与断裂活动 总被引:3,自引:0,他引:3
李延成 《海洋地质与第四纪地质》1993,13(2):25-34
本文将渤海的地质演化分为:前中生代、中生代和新生代三大时期,并论述各个时期的构造特征和地层分布。渤海的断裂系统主要有北北东—北东、近东西和北西向三组,每组断裂既有其各自的发生、发展规率,同时彼此之间又有一定的关联。 相似文献
62.
The European Regional Seas Ecosystem Model (ERSEM) has been coupled with a two-dimensional depth-averaged transport model of the Humber plume region and run to simulate 1988–1989. Simulations of the spatial and temporal variations in chlorophyll-a, nitrate, phosphate and suspended particulate matter distributions in winter, spring and summer show how the development of the spring bloom and subsequent maintenance of primary production is controlled by the physicochemical environment of the plume zone. Results are also shown for two stations, one characterised by the high nutrient and suspended matter concentrations of the plume and the other by the relatively low nutrient and sediment concentrations of the offshore waters. The modelled net primary production at the plume site was 105 g C m−2 a−1 and 127 g C m−2 a−1 offshore. Primary production was controlled by light limitation between October and March and by the availability of nutrients during the rest of the year. The phytoplankton nutrient demand is met by in-situ recycling processes during the summer. The likely effect of increasing and decreasing anthropogenic riverine inputs of nitrate and phosphate upon ecosystem function was also investigated. Modelling experiments indicate that increasing the nitrogen to silicate ratio in freshwater inputs increased the production of non-siliceous phytoplankton in the plume. The results of this model have been used to calculate the annual and quarterly mass balances describing the usage of inorganic nitrogen, phosphate and silicate within the plume zone for the period of the NERC North Sea survey (September 1988 to October 1989). The modelled Humber plume retains 3.9% of the freshwater dissolved inorganic nitrogen, 2.2% of the freshwater phosphate and 1.3% of the freshwater silicate input over the simulated seasonal cycle. The remainder is transported into the southern North Sea in either dissolved or particulate form. The reliability of these results is discussed. 相似文献
63.
The results of the two- and three-dimensional magnetic inversions performed on data located between 20°–24° N on the Mid-Atlantic Ridge indicate the crustal magnetization has decayed exponentially for the last 10 Ma, and that this decay has been fairly symmetric about the ridge axis. After removal of the mean temporal decay, the residual field is characterized by more positive magnetizations at the second-order discontinuities, regardless of initial magnetization direction. A model that involves the preferential emplacement of serpentinized lithologies near the discontinuities is proposed to explain this correlation. The temporal detrending method also indicates that several ridge-parallel depressions located on the flanks of the ridge axis are regions of more positive magnetizations. These bathymetric depressions may mark the locations of detachment faulting that occurred during amagmatic periods of extension. The general symmetry of the crustal magnetization about the ridge axis does not support the occurrence of continuous detachment faulting proposed to correspond to the inner and outer corners of ridge axis discontinuities. 相似文献
64.
雷启修 《中国海洋大学学报(自然科学版)》1991,(4)
宁镇山脉的褶皱带被一系列横断层分割为褶断段。横断层相邻的断块,无论是褶皱的形态、纵断层的数目、规模和断距等特征沿纵向跨越横断层均存在不连续性的跃变,表明这些横断层是早于褶皱或与之伴生的纵断层而存在,并对各断块内发育的地质构造起到限制作用。因横断层作为较早的边界,后期的挤压在被分割的各块段内可以是有差异的,导致宁镇褶皱带在总体上的一致性,分段上的有特殊性。 相似文献
65.
66.
C.G. Castro M. Nieto-Cid X.A. lvarez-Salgado F.F. Prez 《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(12):1925-1940
The short-time-scale variability of the remineralization patterns in the domain of Eastern North Atlantic Central Waters (ENACW) off the NW Iberian Peninsula is studied based on biogeochemical data (oxygen, nutrient salts, total alkalinity, pH, dissolved organic matter and fluorescence of dissolved humic substances) collected weekly between May 2001 and April 2002. The temporal variability of inorganic variables points to an intensification of remineralization during the summer and autumn, with an increase of nutrients, total inorganic carbon and fluorescence and a decrease of oxygen. During the subsequent winter mixing, there is a biogeochemical reset of the system, with lower nutrients, total inorganic carbon and fluorescence and higher oxygen. In contrast to inorganic variables, the levels of dissolved organic matter in the ENACW seem to respond to short-term events probably associated with fast sinking particles, where solubilisation of organic matter prevails over remineralization. Applying a previously published stoichiometric model, we observed a vertical fractionation of organic-matter remineralization. Although there is a preferential remineralization of proteins and P compounds in the entire domain of ENACW, the percentage was higher in the upper ENACW (σ<27.10 kg/m3) than in the lower; the percentage of N and P compounds in the oxidised organic matter was >80% for the upper ENACW and 63% for the lower. Likewise, the redissolution of calcareous structures contributes about 6% and 13% to the carbon regenerated in the upper and lower layers of ENACW, respectively. 相似文献
67.
厦门地区潮间带蟹类的种类组成与分布 总被引:2,自引:0,他引:2
本文根据厦门地区三个岛屿潮间带调查所获的资料,研究了蟹类的种类组成与分布,并应用多样性指数分析了蟹类的结构特征。经鉴定的蟹类有14种55属91种,其中软相57种,岩相44种。软相的蟹类组成与岩相的明显不同。 相似文献
68.
郯庐断裂带及其周缘中新生代盆地发育特征 总被引:19,自引:2,他引:19
郯庐断裂带作为中国东部滨太平洋地区一条巨型走滑构造带,对其周缘中、新生代盆地的发育、演化起着重要的控制作用。随着太平洋板块俯冲方向从NNW向NW到NWW的变化,郯庐断裂带的活动方式逐步从中生代左行走滑-左行斜向滑动过渡到早第三纪以左行斜向-倾向滑动,晚第三纪-第四纪转为倾滑-右行斜向滑动-右行走滑。走滑活动经历了一个循序渐进的周期演变过程。随着郯庐断裂活动方式的演变,其周缘中、新生代盆地的发育逐渐向北迁移,其中南段周缘盆地主要为中生代盆地,中段周缘盆地主要为中、新生代叠加盆地,中北段周缘盆地主要为早第三纪盆地。每个盆地都经历了拉分(伸展)裂陷到挤压反转的演化过程。此外,在同一时期、同一区域剪切应力场作用下,不同区段因其走向变化导致局部应力场变化,在增压弯曲部位发生会聚、挤压、隆升;而释压拉张部位发生离散、伸展、沉降,从而盆地发育。 相似文献
69.
Brent L. Lewis Brian T. Glazer Paul J. Montbriand George W. Luther III Donald B. Nuzzio Timothy Deering Shufen Ma Stephen Theberge 《Marine Chemistry》2007,105(3-4):296-308
A combination of CTD casts, discrete bottle sampling and in situ voltammetric microelectrode profiling was used to examine changing redox conditions in the water column at a single station south of the Bay Bridge in the upper Chesapeake Bay in late July/early August, 2002–2005. Short-term (2–4 h) fluctuations in the oxic/suboxic/anoxic interface were documented using in situ voltammetric solid-state electrodes. Profiles of dissolved oxygen and sulfide revealed tidally-driven vertical fluctuations of several meters in the depth and thickness of the suboxic zone. Bottom water concentrations of sulfide, Mn2+ and Fe2+ also varied over the tidal cycle by approximately an order of magnitude. These data indicate that redox species concentrations at this site varied more due to physical processes than biogeochemical processes. Based on analysis of ADCP data, tidal currents at this station were strongly polarized, with the principal axis of tidal currents aligned with the mainstem channel. Together with the chemical data, the ADCP analysis suggests tidal flushing of anoxic bottom waters with suboxic water from north of the site. The present study is thus unique because while most previous studies have focused on processes across relatively stable redox interfaces, our data clearly demonstrate the influence of rapidly changing physical mixing processes on water column redox chemistry.Also noted during the study were interannual differences in maximum bottom water concentrations of sulfide, Mn2+ and Fe2+. In 2003, for example, heavy spring rains resulted in severe hypoxia/anoxia in June and early July. While reported storm-induced mixing in late July/early August 2003 partially alleviated the low-oxygen conditions, bottom water concentrations of sulfide, Mn2+ and Fe2+ were still much higher than in the previous year. The latter implies that the response time of the microbial community inhabiting the suboxic/anoxic bottom waters to changing redox conditions is slow compared to the time scale of episodic mixing events. Bottom water concentrations of the redox-sensitive chemical species should thus be useful as a tracer to infer prior hypoxic/anoxic conditions not apparent from ambient oxygen levels at the time of sampling. 相似文献
70.
We present a linear Boltzmann equation to model wave scattering in the Marginal Ice Zone (the region of ocean which consists of broken ice floes). The equation is derived by two methods, the first based on Meylan et al. [Meylan, M.H., Squire, V.A., Fox, C., 1997. Towards realism in modeling ocean wave behavior in marginal ice zones. J. Geophys. Res. 102 (C10), 22981–22991] and second based on Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136]. This linear Boltzmann equation, we believe, is more suitable than the equation presented in Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136] because of its simpler form, because it is a differential rather than difference equation and because it does not depend on any assumptions about the ice floe geometry. However, the linear Boltzmann equation presented here is equivalent to the equation in Masson and LeBlond [Masson, D., LeBlond, P., 1989. Spectral evolution of wind-generated surface gravity waves in a dispersed ice field. J. Fluid Mech. 202, 111–136] since it is derived from their equation. Furthermore, the linear Boltzmann equation is also derived independently using the argument in Meylan et al. [Meylan, M.H., Squire, V.A., Fox, C., 1997. Towards realism in modeling ocean wave behavior in marginal ice zones. J. Geophys. Res. 102 (C10), 22981–22991]. We also present details of how the scattering kernel in the linear Boltzmann equation is found from the scattering by an individual ice floe and show how the linear Boltzmann equation can be solved straightforwardly in certain cases. 相似文献