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1.
七野海泻湖的形成与演变   总被引:2,自引:0,他引:2  
七时海泻湖位于渤海海湾的西北岸,是全新世晚期的一个半封闭泻湖。在其演变过程中至少经历过两次由泻湖-淡水湖-泻湖的过程。水体及湖体性质的变化决定于其是否与海连通及河流注入情况。近期,受人类经济活动及工程的影响,七里海泻湖生态系统遭到严重的破坏,并加速了泻湖的退化和消亡。  相似文献   

2.
为了研究泻湖型海湾内经常出现的湾中岛的形成机理,应用水平二维潮流、泥沙输移和地形演变耦合模型,对具有典型的沙坝泻湖地貌形态的水东湾的湾中岛的形成和演化进行了数值模拟,成功地模拟出了涨潮三角洲(大洲岛)的形成过程,计算结果与实际地貌形态总体符合。模型中分别考虑了全沙输沙和推移质输沙两种输沙情况。结果表明,水东湾湾中岛是由涨潮流引起的泻湖内泥沙不断淤积而形成的,是一种涨潮三角洲的地貌形态;全沙输沙模式比推移质输沙模式更适合这一地形演化过程的模拟。模拟结果也再现了湾中岛在25 a期间的地形变化过程,这一研究结果为通过计算数值模拟来研究一般海湾的地貌形态的形成机理和演化过程提供了实际算例。  相似文献   

3.
泻湖是全新世海侵以来发育的以淤积为主的海岸地貌,其沉积地层蕴含了丰富的古环境演变信息.对朝阳港泻湖SO4钻孔岩芯样品作粒度、软体动物、孢粉和14C等项目的测试分析,将该孔地层自下而上划分成陆相、滨浅海相、泻湖相、泻湖-沼泽相等四层和Ⅰ,Ⅱ,Ⅲ,Ⅳ个孢粉组合带.基于对地层和孢粉组合特点的深入剖析,结果表明朝阳港泻湖自全新世海侵以来经历了海湾、沙坝-泻湖和泻湖-沼泽等3个环境演化阶段,同时存在明显的沉积环境和气候变化事件,包括8~7 ka B.P.海陆相之间的不整合沉积间断事件、7~6 ka B.P.的气候暖湿事件和5~4 ka B.P.的明显降温事件.  相似文献   

4.
山东荣成成山角至石岛海岸地貌和沉积特征   总被引:7,自引:0,他引:7  
山东东部成山角至石岛海岸属基岩岬湾岸,进一步可分为侵蚀岸,侵蚀堆积岸,湾内初期夷平岸及连岛砂坝岸等4种类型。本区砂坝-泻湖体系发育良好,泻湖有海湾-泻湖,半封闭泻湖和封闭泻湖等。海岸砂坝粒度和重矿物组合受制于基岩,如南段正长岩分布区,砂体主要由中砂构成,重矿物中锆石,钛铁矿占优势。钻孔资料揭示了海湾、泻湖、砂坝以及各类泻湖沉积的垂直层序,反映了海湾封闭而成泻湖的沉积过程,以及泻湖消亡的历史。  相似文献   

5.
七里海泻湖的形成与演变   总被引:3,自引:0,他引:3  
七里海泻湖位于渤海湾的西北岸,是全新世晚期的一个半封闭泻湖。在其演变过程中至少经历过两次由泻湖──淡水湖──泻湖的过程。水体及湖体性质的变化决定于其是否与海连通及河流注入情况。近期,受人类经济活动及工程的影响,七里海泻湖生态系统遭到严重的破坏,并加速了泻湖的退化和消亡。  相似文献   

6.
广西江平地区沙坝—泻湖沉积相序与沉积环境演变过程   总被引:3,自引:0,他引:3  
本文在地貌、第四纪地质野外调查和33个钻孔资料的基础上,运用粒度、碎屑重矿物、微体古生物和^14C年代测定等方法探讨江平沿岸沙坝-泻湖体系的沉积相序和沉积环境演变过程。沙坝-泻湖发育在一片起伏不平的基岩侵蚀面上,其沉积相序自下而上为:基岩侵蚀面→河床→、河漫滩相→河口湾、近岸浅海相→滨外沙坝、半封闭泻湖相→风成沙丘、封闭充填泻湖沼泽相。本区的沙坝泻湖属于海退型。作者初步认为本区沙坝可分为新、老2期  相似文献   

7.
广西江平地区沙坝-泻湖沉积相序与沉积环境演变过程   总被引:1,自引:0,他引:1  
本文在地貌、第四纪地质野外调查和33个钻孔资料的基础上,运用粒度、碎屑重矿物、微体古生物和14C年代测定等方法探讨江平沿岸沙坝-泻湖体系的沉积相序和沉积环境演变过程。沙坝-泻湖发育在一片起伏不平的基岩侵蚀面上,其沉积相序自下而上为:基岩侵蚀面→河床→、河漫滩相→河口湾、近岸浅海相→滨外沙坝、半封闭泻湖相→风成沙丘、封闭充填泻湖沼泽相。本区的沙坝泻湖属于海退型。作者初步认为本区沙坝可分为新、老2期,老沙坝大约形成于6700~3600aB.P,新沙坝大约形成于2300~1000aB.P。  相似文献   

8.
阿尔卡雄泻湖为一个大尺度三角形海湾,具有发育良好的潮沟体系及潮坪。在泻湖内的研究区,潮沟横切覆盖有海草的泥质潮坪,呈高度蛇曲、树枝状地貌状态。潮沟充填物由沉积在蛇曲顶点的点坝组成。它不是由通常的板状层理(Reineck,1985)构成,也不是由平行层...  相似文献   

9.
太湖的形成和演变过程   总被引:21,自引:0,他引:21  
本文从沉积学、地层学、地貌学、考古学和历史地理学角度,综合分析了太湖的成因和演变。认为地壳沉降与海面上升是构成江南碟形洼地的内外动力,为太湖的形成奠定了基础。全新世海侵最盛时,太湖海湾水深潮急、泻湖、滨海沼泽围绕海湾分布。随南部湾口沙嘴封堵,海湾趋于消失,陆地扩大,遗址增多。3700a来,海面回升,湖面逐渐扩展,形成现代太湖。  相似文献   

10.
黄渤海沿岸海湾—溺谷型潮汐汊道的地貌结构   总被引:4,自引:0,他引:4  
本文以丁字湾等基岩海湾为例,论述了黄渤海沿岸海湾-溺谷型潮汐汊道的地貌结构,尤其着重于口门段深槽及涨、落潮三角洲。认为涨、落潮三角洲的发育状况与入湾河流的供沙量、纳潮水域容量、波浪作用、潮差以及口外海域的开阔程度有关;泻湖型潮汐汊道的落潮三角洲的典型模式可以应用于海湾-溺谷型潮汐汊道,但涨潮三角洲因受基岩海湾的复杂岸线的限制而不能充分发育。本文还讨论了海湾型潮汐汊道与半开敞海湾在动力和形态中的差异  相似文献   

11.
鳚亚目 4 科 33 属 95 种,鰕虎鱼亚目 5 科 98 属 259 种,刺尾鱼亚目 5 科 11 属 65 种,鲈形目 19亚目 104 科 535 属 1799 种。  相似文献   

12.
Soil-sized particulates have been collected on board ship by a mesh technique from the lower troposphere of the North, Equatorial and South Atlantic Ocean, northern and southern Indian Ocean, South and East China Sea and various coastal localities.Spectrographic analysis reveals that, on average, the particulates have concentrations of Mn, Ni, Co, Ga, Cr, V, Ba, and Sr which are of the same order of magnitude as those in average crustal material. In contrast, the average concentrations of Pb, Sn, and Zn are one order of magnitude higher than those in average crustal material.Within this “world-wide” average there are significant geographical variations in the distributions of Pb, Sn, and Zn which may be related to anthropogenic sources.On the basis of trace-element distributions lower tropospheric soil-sized marine particulates have been divided into four genetic components; local, zonal, inter-zonal, and global. The proportions of these components vary geographically, and each component may have both a natural and an anthropogenic fraction.  相似文献   

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Tautog, Tautoga onitis, is an abundant species of fish in estuaries of the northeastern United States. Planktonic tautog larvae are abundant in summer in these estuaries, but there is little information on rates of growth of tautog larvae feeding on natural assemblages of food in the plankton. We examined abundance and growth of larval tautog and environmental factors during weekly sampling at three sites along a nearshore‐to‐offshore transect in Buzzards Bay, Massachusetts, USA during summer 1994. This is the first study of a robust sample size (336 larvae) to estimate growth rates of field‐caught planktonic tautog larvae feeding on natural diets, using the otolith daily‐growth‐increment method. The study was over the entire summer period when tautog larvae were in the plankton. The sampling sites contrasted in several environmental variables including temperature, dissolved oxygen (DO), and chlorophyll a concentration. There was a temporal progression in the abundance of tautog larvae over the summer, in relation to location and temperature. Tautog larvae were first present nearshore, with a pronounced peak in abundance occurring at the nearshore sites during the last 2 weeks in June. Larvae were absent at this time further offshore. From late June through August, larval abundance progressively decreased nearshore, but increased offshore although never approaching the abundance levels observed at the nearshore sites. The distribution and abundance of tautog larvae appeared to be related to a nearshore‐to‐offshore seasonal warming trend and a nearshore decrease in DO. Otoliths from 336 larvae ranging from 2.3 to 7.7 mm standard length had otolith increment counts ranging from 0 to 19 increments. Growth of larval tautog was estimated at 0.23 mm·day?1, and length of larvae prior to first increment formation was estimated at 2.8 mm indicating that first increment formation occurs 3–4 days after hatching at 2.2 mm. Despite spatial and temporal differences in environmental factors, there were no significant differences in growth rates at any of three given sites over time, or between sites. Because larval presence only occurred at a narrow range of temperature (17–23.5 °C) and DO (6.5–9.3 mg·l?1), in situ differences in growth did not appear to be because of differences in larval distribution and abundance patterns relative to these parameters.  相似文献   

18.
Results of trace-metal analyses of water samples obtained during a cruise with the Soviet R.V. “Akademik Kurchatov” in the Indian Ocean are presented. The determinations were performed on board with atomic absorption spectrophotometry after a two-stage dithiocarbamate—Freon extraction procedure. Trace-metal concentrations found are in the same range as those found recently for similar open-ocean areas by other workers. The values for lead and zinc are probably high due to contamination. Vertical profiles indicate biogenic processes as controlling factors for the increase of cadmium, copper and nickel concentrations with depth. Iron shows an irregular depth distribution as a result of large random variations in concentration.  相似文献   

19.
In June 1981, dissolved Zn, Cd, Cu, Ni, Co, Fe, and Mn were determined from two detailed profiles in anoxic Baltic waters (with extra data for Fe and Mn from August 1979). Dramatic changes across the O2H2S interface occur in the abundances of Cu, Co, Fe, and Mn (by factors of ?100). The concentrations of Zn, Cd, and Ni at the redox front decrease by factors between 3 to 5.Equilibrium calculations are presented for varying concentrations of hydrogen sulfide and compared with the field data. The study strongly supports the assumption that the solubility of Zn, Cd, Cu, and Ni is greatly enhanced and controlled by the formation of bisulfide and(or) polysulfide complexes. Differences between predicted and measured concentrations of these elements are mainly evident at lower ΣH2S concentrations.Cobalt proved to be very mobile in anoxic regions, and the results indicate that the concentrations are limited by CoS precipitation. The iron (Fe2+) and manganese (Mn2+) distribution in sulfide-containing waters is controlled by total flux from sediment-water interfaces rather than by equilibrium concentrations of their solid phases (FeS and MnCO3). The concentrations of these metals are therefore expected to increase with prolonged stagnation periods in the basin.  相似文献   

20.
Concentrations of dissolved nutrients (NO3, PO4, Si), germanium species, arsenic species, tin, barium, dimethylsulfide and related parameters were measured along the salinity gradient in Charlotte Harbor. Phosphate enrichment from the phosphate industry on the Peace River promotes a productive diatom bloom near the river mouth where NO3 and Si are completely consumed. Inorganic germanium is completely depleted in this bloom by uptake into biogenic opal. The GeSi ratio taken up by diatoms is about 0·7 × 10?6, the same as that provided by the river flux, confirming that siliceous organisms incorporate germanium as an accidental trace replacement for silica. Monomethylgermanium and dimethylgermanium concentrations are undetectable in the Peace River, and increase linearly with increasing salinity to the seawater end of the bay, suggesting that these organogermanium species behave conservatively in estuaries, and are neither produced nor consumed during estuarine biogenic opal formation or dissolution. Inorganic arsenic displays slight removal in the bloom. Monomethylarsenic is produced both in the bloom and in mid-estuary, while dimethylarsenic is conservative in the bloom but produced in mid-estuary. The total production of methylarsenicals within the bay approximately balances the removal of inorganic arsenic, suggesting that most biological arsenic uptake in the estuary is biomethylated and released to the water column. Dimethylsulfide increases with increasing salinity in the estuary and shows evidence of removal, probably both by degassing and by microbial consumption. An input of DMS is observed in the central estuary. The behavior of total dissolvable tin shows no biological activity in the bloom or in mid-estuary, but does display a low-salinity input signal that parallels dissolved organic material, perhaps suggesting an association between tin and DOM. Barium displays dramatic input behavior at mid-salinities, probably due to slow release from clays deposited in the harbor after catastrophic phosphate slime spills into the Peace River.  相似文献   

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