北部湾北海─临高海区的空气微生物     

陈皓文 《热带海洋学报》1999,(3)

对北部湾的北海-临高海区作了空气微生物含量考察。结果表明,测区的空气平均细菌、真菌、总菌量及真菌/总菌的百分比分别为632．3,1324．0,1956．3CFU·m-3及67．7％。数据分析显示：测区空气微生物含量呈北高、南低、中间最少的势态;近岸海区的比相邻陆区的低,海上部分的平均比环海南岛上空的稍大,比粤西海区的稍少。其昼夜变化显示出空气细菌量峰值出现在晨间,谷值在中午。真菌量的峰值出现在黄昏,谷值在上午。其状态基本上不同于北海市区的,但近似于相邻海区的。空气做生物含量与气温间无显著相关关系。结果意味着空气污染近岸区重于海上区,人为活动的影响也较海上区的大。  相似文献   

Facies and sequence stratigraphic architecture of the Mural Limestone (Albian), Arizona: Carbonate response to global and local factors and implications for reservoir characterization     

Rachel Aisner-Williams  Charles Kerans 《Sedimentology》2020,67(7):3735-3768

This study documents the detailed facies and sequence stratigraphic architecture of a multi-cyclic patch-reef and its associated ramp interior facies that formed during Oceanic Anoxic Event 1b in the Mural Limestone, Arizona, USA. Ramp interior facies are comprised of bedded wackestone/packstone, rudist build-up and coral–algal patch-reef facies located north of Bisbee, Arizona, at the Grassy Hill locality. The larger multi-cyclic patch-reef that developed coevally ca 5 km to the south of Grassy Hill consists of a high-angle windward margin with a narrow ca 70 m long reef frame containing vertically zonated Microsolena, Actinastrea, diverse branching coral and rudist assemblages, and an 870 m long low-angle leeward margin comprised of reef debris rudstone and grainstone shoal facies. Similar reef geomorphology and orientation is documented across the Gulf of Mexico and reflects the shelf-wide north to north-east-trending prevailing wind and current energies. Controls affecting reef formation and growth patterns include changes in accommodation space associated with low-amplitude global sea-level rise and regional thermotectonic subsidence, local accommodation space and nutrient fluctuations associated with the inner shelf depositional setting within a humid and siliciclastic-rich environment. Four aggradational to retrogradational high-frequency sequences are documented in Arizona: High-frequency sequences 1 and 2 represent the first pulse of patch-reef development in an overall second-order marine transgression over the Sonora/Bisbee Shelf. These sequences correlate to δ¹³C signatures associated with Oceanic Anoxic Event 1b across the Gulf of Mexico and suggest that carbonate reefs persisted on the ramp interior during this time. High-frequency sequences 3 and 4 record a second brief transgression and backstepping of reef facies followed by the final regression of shallow shelf carbonates that correlates to more robust patch-reef development in Sonora, Mexico. The patch-reef at Paul Spur is an excellent outcrop analogue for productive patch-reefs in the Maverick Basin (Comanche Shelf) of Texas. Detailed facies mapping of this outcrop analogue shows that the greatest reservoir potential is contained within the backreef grainstone shoals where primary porosity of up to 15% is observed.  相似文献   

Are carbonate barrier islands mobile? Insights from a mid to late-Holocene system,Al Ruwais,northern Qatar     

John Rivers  Max Engel  Robert Dalrymple  Ruqaiya Yousif  Christian J. Strohmenger  Ismail Al-Shaikh 《Sedimentology》2020,67(1):534-558

Barrier islands are important landforms in many coastal systems around the globe. Studies of modern barrier island systems are mostly limited to those of siliciclastic realms, where the islands are recognized as mobile features that form on transgressive coastlines and migrate landward as sea-level rises. Barrier islands of the ‘Great Pearl Bank’ along the United Arab Emirates coast are the best-known carbonate examples. These Holocene islands, however, are interpreted to be anchored by older deposits and immobile. The mid-Holocene to late-Holocene depositional system at Al Ruwais, northern Qatar, provides an example of a mobile carbonate barrier island system, perhaps more similar to siliciclastic equivalents. Sedimentological and petrographic analyses, as well as ¹⁴C-dating of shells and biogenic remains from vibracored sediments and surface deposits, show that after 7000 years ago a barrier system with a narrow back-barrier lagoon formed along what is now an exposed coastal zone, while, contemporaneously, a laterally-extensive coral reef was forming immediately offshore. After 1400 years ago the barrier system was forced to step ca 3 km seaward in response to a sea-level fall of less than 2 m, where it re-established itself directly on the mid-Holocene reef. Since that time, the barrier has retreated landward as much as 1000 m to its current position, exposing previously-deposited back-barrier lagoonal sediment at the open-coast shoreline. In modern neritic warm-water carbonate settings mobile barrier island systems are rare. Their construction and migration may be inhibited by reef formation, early cementation, and the relative inefficiency of sourcing beach sediments from open carbonate shelves. Carbonate barrier island systems likely formed more commonly during geological periods when ramps and unrimmed shelves predominated and in calcite seas, when meteoric cementation was minimized as a result of initial calcitic allochem mineralogy. As with their siliciclastic analogues, however, recognition of the influence of these transient landforms in the rock record is challenging.  相似文献   

广西北海半岛夏季营养盐及水质状况分析   总被引：1，自引：0，他引：1  

徐轶肖  陶晓娉  刘成辉  韦光领  何喜林  姚秋翠  陈武荣  李斌 《海洋科学》2021,45(6):107-117

近年北部湾藻华灾害频发,为了解与藻华暴发密切相关的营养盐及水质状况,2020年8月作者对北部湾北海半岛铁山港、营盘、涠洲岛、斜阳岛及涠洲岛西部远岸海域共21个站位采集表层海水,分析营养盐含量和结构特征,并利用富营养化指数和有机污染指数对该海域水质进行等级划分与评价。结果表明：北海半岛海域DIN、PO₄-P和SiO₃-Si均值分别为0.210、0.021和0.270 mg/L。其中,铁山港营养盐由港内至港外呈递减趋势,营盘海域由近岸至远岸,DIN和SiO₃-Si含量先递减再增加,PO₄-P则表现为递增,涠洲岛海域及远岸各站位营养盐分布无明显特征。北海半岛海域N/P、Si/N和Si/P均值分别为11.8、1.7和14.6,显示47.6%海域为潜在N限制,而潜在P限制和Si限制海域均为9.5%;叶绿素a仅与COD显著相关,相关系数为0.475。调查海域富营养化指数均值1.82,以铁山港港内富营养化程度最高,由港内严重富营养至港外贫营养递减,营盘近岸7号站位中度富营养,其余76.2%调查站位仍处于贫营养水平;有机污染指数均值1.85,良好和较好水质共占38.1%,其余61.9%水质受到不同程度有机污染,亦以铁山港水质污染最为严重,重度污染仅在该海域发现。可见,北海半岛夏季表层海水以潜在N限制为主,铁山港和营盘近岸富营养化和有机污染较严重,其余站位基本良好,影响表层水体叶绿素a含量的主要因素是有机质,可能与海域微生物强烈降解作用相关。本研究可为北部湾海洋环境保护和赤潮研究提供基础环境数据。  相似文献   

广西北部湾地区表层土壤As分布特征及其影响因素     

郑国东  覃建勋  付伟  杨志强  赵辛金  卢炳科 《吉林大学学报(地球科学版)》2018,48(1):181-192

选取广西北部湾地区表层土壤中As元素为研究对象,采集了7 327个土壤样品,400个岩石样品,分析As、K₂O、Na₂O、CaO、MgO、SiO₂、Al₂O₃、TFe₂O₃、Mn、Ti、pH和有机碳（SOC）等指标,探讨了土壤成土母岩、成土作用、土壤组成、pH和有机质等对表层土壤As元素的影响。结果表明：As元素平均质量分数为7.96×10^-6,为中国土壤背景值0.80倍;风化作用对于As元素的次生富集起到极为重要的作用,明显强于成土母岩As元素背景的影响。Pearson相关分析和主成分分析表明：在土壤组成和土壤性质等因素中,含Al矿物（Al₂O₃）、含Fe矿物（TFe₂O₃）、含Si矿物（SiO₂）和SOC,对土壤As的富集起到主导作用;pH 和含 Ca矿物（CaO）的作用较弱;而含K矿物（K₂O）、含Na矿物（Na₂O）和含Mg矿物（MgO）对As的次生富集作用可以忽略不计。  相似文献   

Hydrocarbon source rock potential in the southwestern Gulf of Suez graben: Insights from organic geochemistry and palynofacies studies on well samples from the Ras El Bahar Oilfield     

《Marine and Petroleum Geology》2017

Palynological and biomarker characteristics of organic facies recovered from Cretaceous–Miocene well samples in the Ras El Bahar Oilfield, southwest Gulf of Suez, and their correlation with lithologies, environments of deposition and thermal maturity have provided a sound basis for determining their source potential for hydrocarbons. In addition to palynofacies analysis, TOC/Rock-Eval pyrolysis, kerogen concentrates, bitumen extraction, carbon isotopes and saturated and aromatic biomarkers enable qualitative and quantitative assessments of sedimentary organic matter to be made. The results obtained from Rock-Eval pyrolysis and molecular biomarker data indicate that most of the samples come from horizons that have fair to good hydrocarbon generation potential in the study area. The Upper Cretaceous–Paleocene-Lower Eocene samples contain mostly Type-II to Type-III organic matter with the capability of generating oil and gas. The sediments concerned accumulated in dysoxic–anoxic marine environments. By contrast, the Miocene rocks yielded mainly Type-III and Type-II/III organic matter with mainly gas-generating potential. These rocks reflect deposition in a marine environment into which there was significant terrigenous input. Three palynofacies types have been recognized. The first (A) consists of Type-III gas-prone kerogen and is typical of the Early–Middle Miocene Belayim, Kareem and upper Rudeis formations. The second (B) has mixed oil and gas features and characterizes the remainder of the Rudeis Formation. The third association (C) is dominated by amorphous organic matter, classified as borderline Type-II oil-prone kerogen, and is typical of the Matulla (Turonian–Santonian) and Wata (Turonian) formations. Rock-Eval T_max, PI, hopane and sterane biomarkers consistently indicate an immature to early mature stage of thermal maturity for the whole of the studied succession.  相似文献   

The relationship among environmental variables,jellyfish and non‐gelatinous zooplankton: A case study in the north of the Gulf of Oman          下载免费PDF全文

Fatemeh Pourjomeh  Mohammad Reza Shokri  Hamid Rezai  Hassan Rajabi‐Maham  Elham Maghsoudlou 《Marine Ecology》2017,38(6)

Processes underlying the temporal and spatial variations observed in the distribution of jellyfish and non‐gelatinous zooplankton in the Gulf of Oman are not well understood. This information gap is clearly a major issue in controlling the harmful blooms of jellyfish and non‐gelatinous zooplankton. Samples of jellyfish and non‐gelatinous zooplankton were collected from six stations in Chabahar Bay and three stations in Pozm Bay within four seasons. At each station, environmental variables were also recorded from bottom and surface water. A total of 83 individuals of medusae representing four species of Scyphozoa (i.e., Cyanea nozakii, Chrysaora sp., Pelagia noctiluca, Catostylus tagi) and species of Hydrozoa (i.e., Diphyes sp., Rhacostoma sp., Aequorea spp.) were observed in the study area. A total of 70,727.25 individuals/m^?3 of non‐gelatinous zooplankton dominated by copepods and cladocerans were collected in nine stations within the four seasons. The results of a RELATE analysis yielded no significant association between species composition for jellyfish and non‐gelatinous zooplankton. Among environmental variables, water transparency, nitrite concentration, water depth and temperature were better associated with the total variation in jellyfish species composition than with that of non‐gelatinous zooplankton. Dissolved oxygen, pH, and phosphate concentration were significant environmental variables associated with the variation in the spatial and temporal distribution patterns of non‐gelatinous zooplankton assemblages. Although some jellyfish species (i.e., Rhacostoma sp., Pelagia noctiluca, Catostylus tagi) occur independently of non‐gelatinous zooplankton assemblages, other jellyfish (i.e., Chrysaora sp., Aequorea spp., Cyanea nozakii, Diphyes sp.) are strongly correlated with non‐gelatinous zooplankton assemblages.  相似文献   

Analysis of symbiotic Symbiodinium in scleractinian corals off Northwestern Kish Island,Persian Gulf          下载免费PDF全文

Amirhossein Gheitanchi Mashini  Mona Fard Yazdani  Pargol Ghavam Mostafavi  Mohammad Hassan Shahhosseiny 《Marine Ecology》2017,38(2)

The genus Symbiodinium plays an essential role in the resistance and survival of reef‐building corals during temperature anomalies. Coral colonies inhabiting the Persian Gulf (PG) experience extended periods of different stresses. Kish Island is located in the harsh environment of the Northern PG with previously reported bleaching episodes. Samples of six coral species from Northwestern Kish Island were analysed by internal transcribed spacer 2 of ribosomal DNA to identify in hospite Symbiodinium populations. The results showed that lineage D of Symbiodinium was the most prevalent clade among different coral colonies, while clade C was only detected in symbiosis with a single coral species. However, the detected Symbiodinium subclades belonged to two host generalists. The predominance of the stress tolerant Symbiodinium trenchii and subclade C3 could suggest an acclimatization strategy to cope with the hostile environment of the PG.  相似文献   

Seafloor and buried mounds on the western slope of the Niger Delta     

《Marine and Petroleum Geology》2017

Seafloor mounds are potential geohazards to offshore rig emplacement and drilling operations and may contain evidence of underlying petroleum systems. Therefore, identifying and mapping them is crucial in de-risking exploration and production activities in offshore domains.A 738 km² high resolution three-dimensional seismic dataset was used to investigate the occurrence, seismic characteristics and distribution of features interpreted as seafloor and buried sediment mounds, at water-depths of 800–1600 m, on the western Niger Delta slope. Fifteen seafloor mounds and eighteen shallowly buried mounds were identified. The seafloor mounds are characterised by lower seismic amplitude anomalies than the surrounding seabed sediments, and overlie vertical zones of acoustic blanking. The buried mounds in contrast are characterised by high amplitude anomalies; they also directly overlie sub-vertical zones of acoustic blanking. Seismic evidences from the features, their distribution patterns and tectono-stratigraphic associations suggest that their formation was controlled by the juxtaposition of buried channels and structural highs and their formation caused by focused fluid flow and expulsion of entrained sediments at the seabed.Considering the acoustic and geometrical characteristics of the mounds and comparing them with mound-shaped features from around the world, we conclude that the mounds most likely comprise heterolithic seafloor extrusions of muds and sands from the Agbada Formation with gas and possibly oil in some of the pore space giving rise to the acoustic characteristics.  相似文献   

海南岛及北部湾海域海啸数值模拟与影响分析     

李智广  谢顺平  都金康  黄洋  左天惠  郑文龙 《地球信息科学学报》2015,17(8):937-944

海底地震引发的海啸灾害,对沿海国家和地区的影响是相关领域的研究热点。研究采用COMCOT海啸数值模拟模型,对可能发生在马尼拉海沟一次地震活动（M_w=9.0级）所引起的海啸过程进行了数值模拟,并研究了该海啸传播到海南岛和北部湾的过程及其特点,分析海啸波对这一地区可能造成的影响。研究发现,传播到北部湾地区的海啸波具有明显的非线性特征,海啸发生后2 h 10 min左右到达海南岛东海岸,首轮波高达2.1 m;随着湾内水深逐渐变浅,受制于海底摩阻,及海南岛的阻隔与缓冲作用,海啸到达广西壮族自治区南部沿海地区的时间,被推迟到距地震发生8 h后,海啸波高减小到0.4 m,海啸波能量大为衰减。研究结果表明,马尼拉海沟地震引发海啸,对海南岛东南部沿海影响较大,有成灾的可能性;而对广西壮族自治区南部沿海及北部湾地区的影响较弱,一般不会造成大的灾害。  相似文献