南海北部白云凹陷-东沙岛西南海区的浅地层探测与深水沉积特点   总被引：1，自引：0，他引：1  

阎贫  王彦林  郑红波 《热带海洋学报》2011,30(2)

采用新引进的海洋深水浅层剖面仪,从珠江口外陆架进入白云凹陷-东沙岛西南海区中陆坡区,进行了浅地层探测,获得了高分辨率反射记录.分析发现,白云凹陷上陆坡段沉积连续性较好,海底反射强度侧向变化平缓,显示了比较均一的沉积底质和微弱的海底水动力条件;在白云凹陷-东沙岛西南海区中陆坡区,海底滑坡严重,局部存在强烈的、平行陆坡的海底洋流冲蚀,海底地形崎岖不平,反射强度侧向变化大,表明海底底质不均匀,海底水动力强.浅地层记录还显示中陆坡海底山丘有海底气体泄露现象,结合常规反射地震识别的海底泥底辟特征,确定海底山丘为泥火山.气体泄露和海底反射振幅的变化代表了海底浅层聚有丰富的气体以及嗜甲烷生物链活动的钙化,因而推断该区不仅是油气的聚集区,也是水合物的聚集带.  相似文献   

Holocene storminess inferred from sediments of two lakes on Adak Island,Alaska     

Anne C.L. Krawiec  Darrell S. Kaufman 《Quaternary Research》2014

The abundance of sedimentary organic material from two lakes was used to infer past Holocene storminess on Adak Island where frequent storms generate abundant rainfall and extensive cloud cover. Andrew and Heart Lakes are located 10 km apart; their contrasting physical characteristics cause the sedimentary organic matter to respond differently to storms. Their records were synchronized using correlated tephra beds. Sedimentation rates increased between 4.0 and 3.5 ka in both lakes. Over the instrumental period, Andrew Lake biogenic-silica content (BSi) is most strongly correlated with winter sunlight availability, which influences photosynthetic production, and river input, which influences the dilution of BSi by mineral matter. Heart Lake BSi is likely affected by wind-driven remobilization of sediment, as suggested by correlations among BSi, the North Pacific Index, and winter storminess. The results indicate relatively stormy conditions from 9.6 to 4.0 ka, followed by drying between 4.0 and 2.7 ka, with the driest conditions from 2.7 to 1.5 ka. The stormiest period was between AD 500 and 1200, then drying from 1150 to 1500 and more variable until 1850. This record of Holocene storminess fills a major gap at the center of action for North Pacific wintertime climate.  相似文献   

Timing of the Northern Prince Gustav Ice Stream retreat and the deglaciation of northern James Ross Island,Antarctic Peninsula during the last glacial–interglacial transition     

Daniel Nývlt  Régis Braucher  Zbyněk Engel  Bedřich Mlčoch   《Quaternary Research》2014

The Northern Prince Gustav Ice Stream located in Prince Gustav Channel, drained the northeastern portion of the Antarctic Peninsula Ice Sheet during the last glacial maximum. Here we present a chronology of its retreat based on in situ produced cosmogenic ¹⁰Be from erratic boulders at Cape Lachman, northern James Ross Island. Schmidt hammer testing was adopted to assess the weathering state of erratic boulders in order to better interpret excess cosmogenic ¹⁰Be from cumulative periods of pre-exposure or earlier release from the glacier. The weighted mean exposure age of five boulders based on Schmidt hammer data is 12.9 ± 1.2 ka representing the beginning of the deglaciation of lower-lying areas (< 60 m a.s.l.) of the northern James Ross Island, when Northern Prince Gustav Ice Stream split from the remaining James Ross Island ice cover. This age represents the minimum age of the transition from grounded ice stream to floating ice shelf in the middle continental shelf areas of the northern Prince Gustav Channel. The remaining ice cover located at higher elevations of northern James Ross Island retreated during the early Holocene due to gradual decay of terrestrial ice and increase of equilibrium line altitude. Schmidt hammer R-values are inversely correlated with ¹⁰Be exposure ages and could be used as a proxy for exposure history of individual granite boulders in this region and favour the hypothesis of earlier release of boulders with excessive ¹⁰Be concentrations from glacier directly at this site. These data provide evidences for an earlier deglaciation of northern James Ross Island when compared with other recently presented cosmogenic nuclide based deglaciation chronologies, but this timing coincides with rapid increase of atmospheric temperature in this marginal part of Antarctica.  相似文献   

青岛灵山岛晚中生代重力流沉积特征及环境分析   总被引：3，自引：0，他引：3  

邵珠福  钟建华  李勇  倪良田  刘圣鑫  范莉红  陈彬 《地质论评》2014,60(3):555-566

青岛灵山岛晚中生代发育一套重力流沉积,国内学者对其成因机制存在争议。笔者通过对造船厂、灯塔、千层崖、羊礁洞、老虎嘴、背来石等剖面的重点观察发现:灵山岛晚中生代地层出露以厚度不等的细粒砂泥岩与火山熔岩、火山碎屑岩为主,夹沉火山碎屑岩和侵入体,地层从老到新组合为一个水体变浅的水退序列。地层中发育不同类型、不同尺度、不同期次的软沉积变形构造,如软沉积变形褶皱、布丁构造、负载构造和火焰构造、软双重构造等。灵山岛晚中生代重力流沉积碎屑岩主要是块体搬运沉积(砂质滑塌和砂质碎屑流)和浊流沉积,向上过渡为陆相三角洲前缘沉积,其成因机制是物源供应充足的湖盆三角洲前缘在构造坡度或沉积坡度控制下,受地震和火山活动影响发生的块体搬运沉积和浊流沉积。初步研究认为沉积时的古斜坡方向为南东—北西方向。  相似文献   

Morphodynamics of a mesotidal rocky beach: Palmeras beach,Gorgona Island National Natural Park,Colombia     

《Journal of South American Earth Sciences》2014

The response of a rocky beach to different possible combinations of hydrodynamic conditions (tides, waves, oceanic currents) has been little studied. In this work, the morphodynamic response to different hydrodynamic forcing is evaluated from sedimentological and geomorphological analysis in seasonal and medium term (19 years) scale in Palmeras beach, located in the southwest of Gorgona Island National Natural Park (NNP), a mesotidal rocky island on the Colombian Pacific continental shelf. Palmeras is an important nesting area of two types of marine turtles, with no anthropogenic stress. In the last years, coastal erosion has reduced the beach width, restricting the safe areas for nesting and conservation of these species. Until now, the sinks, sources, reservoirs, rates, and paths of sediments were unknown, as well as their hydrodynamic forcing. The beach seasonal variability, from October 2010 to August 2012, was analyzed based on biweekly or monthly measurements of five beach profiles distributed every 200 m along the 1.2 km of beach length. The main paths for sediment transport were defined from the modeling of wave currents with the SMC model (Coastal Modeling System), as well as the oceanic currents, simulated for the dry and wet seasons of 2011 using the ELCOM model (Estuary and Lake COmputer Model). Extreme morphologic variations over a time span of 19 years were analyzed with the Hsu and Evans beach static equilibrium parabolic model, from one wave diffraction point which dominates the general beach plan shape. The beach lost 672 m³/m during the measuring period, and erosional processes were intensified during the wet season. The beach trends responded directly to a wave mean energy flux change, resulting in an increase of up to 14 m in the width northward and loss of sediments in the beach southward. This study showed that to obtain the integral morphodynamic behavior of a rocky beach it is necessary to combine information of hydrodynamic, sedimentology and geomorphology in different time scales.  相似文献   

海南岛晚海西-印支期埃达克质岩的构造环境判别及其对比     

高小卫  吴秀荣  杨振强 《华南地质与矿产》2014,(3):206-217

本文采用岩浆岩石地球化学作图软件,处理了海南岛晚海西-印支期埃达克质岩以及钾玄质岩的岩石化学分析数据,目的在于探讨其形成构造环境。根据地球化学-构造环境判别图解,海南岛在海西-印支期属于火山-岩浆弧环境,并将其与隔海相望的印支陆块东侧和华南板块同构造旋回的埃达克质岩进行对比。对比结果表明:海南岛与长山带晚海西-印支期埃达克质岩具有相似的构造环境,主要为主动大陆汇聚边缘带,其次为碰撞后板内地壳伸展-减薄环境。而华南板块同期的埃达克质岩则为大陆板内陆-陆同碰撞成因,与陆内深大断裂的活动有关。  相似文献   

城市热环境调节服务供需失衡关键区识别与优先级划分     

辛儒鸿  曾坚  李凯  沈中健 《地理研究》2022,41(11):3124-3142

城市热环境效应严重威胁人类生命安全和社会经济的可持续发展,识别热环境调节服务供需失衡关键区对于缓解城市热环境效应至关重要。本文基于环境风险评估框架和环境公平理论,构建了城市热环境调节服务供需评价指标体系与研究框架：选取危险源、暴露度、脆弱性指标,评价城市居民对热环境调节服务的需求水平;选取热环境调节效率指标评价绿色基础设施对热环境调节服务的供给能力;使用供需匹配和优先级指数识别供需失衡关键区,并划分规划干预优先级。结果表明： ① 厦门岛城市热环境危险源、暴露度和脆弱性之间存在明显的空间异质性,3项指标共同决定需求水平,高需求区占比29.13%,并呈现出“全域分散,局部密集”的空间格局特征。② 厦门岛绿色基础设施空间占比集散特征明显,决定了城市热环境调节供给能力分布不均,低值区占比72.9%,且与热环境调节需求水平存在相反的局部空间集聚特征。③ 厦门岛城市热环境调节服务供需关系具有“高供-高需”“低供-高需”“低供-低需”和“高供-低需”4种类型,其中有451个单元处于“低供-高需”失衡状态,面临供不应求的严峻挑战。④ 有84个单元处于高干预优先级别,主要分布于马垅社区、江村社区、屿后社区及鹭江社区等片区,该类区域是需要优先调控的关键区。本文可为高效选址,针对性地制定城市热环境缓解策略提供科学依据,所构建的指标体系与研究框架适用于其他城市。  相似文献   

REPORT ON PONTONIINE SHRIMPS (CRUSTACEA: DECAPODA) COLLECTED BY JOINT CHINESE-GERMAN MARINE BIOLOGY EXPEDITIONS TO HAINAN ISLAND,SOUTH CHINA SEA I. ANCHISTUS, CONCHODYTES, CORALLIOCARIS     

李新正  刘瑞玉 《中国海洋湖沼学报》2002,(4)

ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｄｏ ＷｅｓｔＰａｃｉｆｉｃｗａｔｅｒｉｓｔｈｅｍａｉｎｄｉｓｔｒｉｂｕｔｉｏｎａｒｅａｏｆｓｈｒｉｍｐｓｏｆｔｈｅｓｕｂｆａｍｉｌｙＰｏｎｔｏｎｉｉｎａｅ ,ｗｈｅｒｅｍｏｒｅｔｈａｎ 60ｏｆｔｈｅ79ｃｕｒｒｅｎｔｌｙｒｅｃｏｇｎｉｚｅｄｐｏｎｔｏｎｉｉｎｅｇｅｎｅｒａｈａｖｅｂｅｅｎｆｏｕｎｄ .Ｔｈｅｒｉｃｈｐｏｎ ｔｏｎｉｉｎｅｆａｕｎａｏｆＨｏｎｇＫｏｎｇ ( 2 3ｓｐｅｃｉｅｓ,Ｂｒｕｃｅ ,1 982 ,1 990 ) ,ａｎｄｔｈｅｎｅｉｇｈｂｏｒｉｎｇｗａｔｅｒｓ,Ｐｈｉｌｉｐ ｐ…  相似文献   

Evolution of Br/Cl ratios in fumarolic salammoniac from Vulcano (Aeolian Islands,Italy)     

Nara Coradossi  Anna Garavelli  Martino Salamida  Filippo Vurro 《Bulletin of Volcanology》1996,58(4):310-316

 Bromine/chlorine ratios in salammoniac samples, collected from 1983 to 1994 at the Fossa crater fumaroles of Vulcano (Aeolian Islands), were determined. The data obtained in this work have been compared to those obtained by Coradossi et al. (1985) in order to carry out a systematic study of the Br/Cl ratio variations since 1977. Br/Cl ratios range from 0.04 to 0.29. The Br/Cl ratio variations observed have been interpreted as the result of different contributions among deep and shallow components feeding the fumarolic fluids of Vulcano. The Br/Cl increases, which occurred from 1977 to 1979, in 1983–1984 and in 1992–1993, have been connected to an increased input of magmatic gases. Received: 10 November 1995 / Accepted: 12 July 1996  相似文献   

REPORT ON PONTONIINE SHRIMPS（CRUSTACEA：DECAPODA）COLLECTED BY JOINT CHINESE—GERMAN MARINE BIOLOGY EXPEDITIONS TO HAINAN ISLAND,SOUTH CHINA SEA i.ANCHISTUS,CONCHODYTES,CORALLIOCARIS     

李新正  刘瑞玉 《中国海洋湖沼学报》2002,20(4):371-377

The present paper reports 7 species of pontoniine shrimps collected from Hainan Island,South China Sea,by the Joint Chinese-German Marine Biology Expeditions,in which,Conchodytes nipponensis(De Haan,1844)and Coralliocaris brevirostris Borradaile,1898 are new records from Chinese waters.  相似文献