Seasonal contribution of living phytoplankton carbon to vertical fluxes in a coastal upwelling system (Ría de Vigo, NW Spain)     

D. Zúñiga  F. Alonso-PérezC.G. Castro  B. ArbonesF.G. Figueiras 《Continental Shelf Research》2011,31(5):414-424

The aim of this study is to explore the contribution of living phytoplankton carbon to vertical fluxes in a coastal upwelling system as a key piece to understand the coupling between primary production in the photic layer and the transfer mechanisms of the organic material from the photic zone. Between April 2004 and January 2005, five campaigns were carried out in the Ría de Vigo (NW Iberian Peninsula) covering the most representative oceanographic conditions for this region. Measurements of particulate organic carbon (POC), chlorophyll-a (chl a), phaeopigments (phaeo), and identification of phytoplankton species were performed on the water column samples and on the organic material collected in sediment traps.The POC fluxes measured by the sediment traps presented no seasonal variation along the studied period ranging around a mean annual value of 1085±365 mg m⁻² d⁻¹, in the upper range of the previously reported values for other coastal systems. The fact that higher POC fluxes were registered during autumn and winter, when primary production rates were at their minimum levels points to a dominant contribution of organic carbon from resuspended sediments on the trap collected material. On the contrary, fluxes of living phytoplankton carbon (C_phyto) and chl a clearly presented a seasonal trend with maximum values during summer upwelling (546 mg m⁻² d⁻¹ and 22 mg chl a m⁻² d⁻¹, respectively) and minimum values during winter (22 mg m⁻² d⁻¹ and 0.1 mg chl a m⁻² d⁻¹, respectively). The contribution of C_phyto to the vertical flux of POC ranged between 2% and 49% in response to the pelagic phytoplankton community structure. Higher values of C_phyto fluxes were registered under upwelling conditions which favour the dominance of large chain-forming diatoms (Asterionellopsis glacialis and Detonula pumila) that were rapidly transferred to the sediments. By contrast, C_phyto fluxes decreased during the summer stratification associated with a pelagic phytoplankton community dominated by single-cell diatoms and flagellates. Minimal C_phyto fluxes were observed during the winter mixing conditions, when the presence of the benthic specie Paralia sulcata in the water column also points toward strong sediment resuspension.  相似文献   

影响多年冻土上限变化的因素探讨   总被引：6，自引：6，他引：0  

王银学  赵林  李韧  吴通华  乔永平 《冰川冻土》2011,33(5):1064-1067

利用地温及活动层水热观测资料,分析青藏公路沿线近年来影响多年冻土上限的变化因素.研究结果显示,青藏公路沿线冻土上限总体呈现下降趋势,冻土上限的变化与近年来区域气候变化的趋势一致;近年来多年冻土上限下降0.1～0.5 m,所处的地理位置不同,冻土上限下降的幅度也不同.气温变化是影响冻土上限的一个重要的外部因素,上限变化的...  相似文献   

Export and mesopelagic particle flux during a North Atlantic spring diatom bloom   总被引：2，自引：0，他引：2  

Patrick Martin  Richard S. LampittMary Jane Perry  Richard SandersCraig Lee  Eric D'Asaro 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(4):338-349

Spring diatom blooms are important for sequestering atmospheric CO₂ below the permanent thermocline in the form of particulate organic carbon (POC). We measured downward POC flux during a sub-polar North Atlantic spring bloom at 100 m using thorium-234 (²³⁴Th) disequilibria, and below 100 m using neutrally buoyant drifting sediment traps. The cruise followed a Lagrangian float, and a pronounced diatom bloom occurred in a 600 km² area around the float. Particle flux was low during the first three weeks of the bloom, between 10 and 30 mg POC m⁻² d⁻¹. Then, nearly 20 days after the bloom had started, export as diagnosed from ²³⁴Th rose to 360-620 mg POC m⁻² d⁻¹, co-incident with silicate depletion in the surface mixed layer. Sediment traps at 600 and 750 m depth collected 160 and 150 mg POC m⁻² d⁻¹, with a settled volume of particles of 1000-1500 mL m⁻² d⁻¹. This implies that 25-43% of the 100 m POC export sank below 750 m. The sinking particles were ungrazed diatom aggregates that contained transparent exopolymer particles (TEP). We conclude that diatom blooms can lead to substantial particle export that is transferred efficiently through the mesopelagic. We also present an improved method of calibrating the Alcian Blue solution against Gum Xanthan for TEP measurements.  相似文献   

LS凹陷岩性油气藏勘探实践     

姚云霞  刘江  刘金水  张雷 《海洋地质译丛》2011,(3):32-35

LS凹陷是一个东断西超的断陷盆地,古新统MYF组低位沉积时期,西斜坡上形成了“沟＋坡＋扇”沉积格局,岩性圈闭发育其中。从岩性圈闭沉积背景出发,综合应用高分辨率层序地层学、沉积相分析、储层预测和描述等关键技术,发现了一组有利油气聚集的低位扇,揭示了一个具有相同沉积背景、相同成藏机理的勘探领域。  相似文献   

重磁力联合反演在研究复杂盆地基底构造中的应用     

王西文 《地球科学与环境学报》1993,(1)

本文采用重磁力联合反演方法,计算了民和盆地基底深度和视磁化强度。针对该盆地特点,设计了等效和非均质重力反演模型,在约束条件下分块反演得到准确可靠的基底深度;用基底深度和航磁异常反演基底视磁化强度,根据岩石磁化率参数,判定基底岩性横向分布。该方法不仅能提供盆地基底构造形态,而且能提供基底岩性信息。  相似文献   

Characteristics of resuspended sediment from Georges Bank collected with a sediment trap     

C.M. Parmenter  M.H. Bothner  B. Butman 《Estuarine, Coastal and Shelf Science》1983,17(5):521-533

A sediment trap was deployed 3 m from the bottom at a water depth of 62 m on the southern flank of Georges Bank (41°02·2′N, 67°33·5′W) from 30 September 1978 to 10 March 1979 to qualitatively determine the size of sediments resuspended from the bottom by winter storms and to determine if seasonal changes in the phytoplankton could be observed in the trapped sediment.Bulk X-ray analyses of the trapped sediment showed layers of distinctly different textures preserved in the collection vessel. The median grain size of sampled layers ranged from 2·7 to 6·5 φ (fine sand to silt), but all layers contained a pronounced mode in the 3 φ (fine sand) range. Nine layers containing relatively large amounts of sand were present. The sand content was 75% in the coarest layers and about 32% in the fine layers. The median grain size of bottom sediments at the deployment site was considerably coarser than the trap samples, although the dominant grain size was also 3 φ.Average bottom-current speeds during the deployment period were about 30 cm s^?1 with a range of 10 to 50 cm s^?1. Bottom stress, computed from the observed currents and waves, suggest that 11 storms caused sufficient stress to resuspend 3 φ-sized sediments, in good agreement with the nine layers of relatively coarse sediments collected in the trap. Surface waves had to be included in the calculation of bottom stress because the bottom currents alone were insufficient to cause the resuspension of 3 φ-sized sediment.The trapped sediments contain numerous diatoms and coccoliths that are typical of late fall and winter assemblages. No clear seasonal difference in the flora was noted among sampled layers, probably due to the large influx of resuspended material and a reduced primary flux during this period. An undescribed species of Thalassiosira (G. Fryxell, personal communication), and siliceous scales of unknown systematic position were observed at all levels.  相似文献   

Distribution of Mid-deeply Buried Sand-bodies and their Hydrocarbon Significance at Basin Margins: Case Study of the Paleogene in the Eastern Liuzan Area of the Nanpu Sag,Bohai Bay Basin,China     

CUI Lijie  JIAN Shikai  ZHANG Boming  XIE Xiongju  LI Liang 《《地质学报》英文版》2021,95(4):1279-1294

The current research aims to unlock the temporal and spatial distribution of sand-bodies and their relationship with hydrocarbon accumulation in the mid-deep layer of basin margins, located in the eastern part of the Liuzan area of the Nanpu Sag, Bohai Bay Basin, China. Through this study, the main target interval of the area was divided into two fourth-order sequences. The lean sand mixed sedimentary belt with great importance in controlling hydrocarbon accumulation was identified through the comprehensive use of 3D seismic data, logging data, lithological data and seismic inversion data. A detailed analysis of sand-body development characteristics and their role in controlling hydrocarbon accumulation was conducted. The results reveal that the study area mainly develops two distinct fan-delta lobes from the NE-trending sediment supply direction. Due to the relatively high influence of the lacustrine transgression event, the scale of the lean sand mixed sedimentary belt within the SQ1-1 (the lacustrine transgressive systems tract) is relatively small, showing a relatively continuous distribution of sand bodies in the plane. Conversely, due to the relatively high impact of the lacustrine regression event, the scale of the lean sand mixed sedimentary belt developed within the SQ1-2 (the highstand systems tract) is relatively large, the two east sets of fan-delta sedimentary systems being clearly separated. The lean sand mixed sedimentary belt formed a good lateral occlusion belt in favor of hydrocarbon accumulation. Through composite analysis of structural interpretation results, sand-body distribution and well test data, it is evident that the lean sand mixed sedimentary belt located in the structural high is not a favorable zone for hydrocarbon accumulation. In contrast, the wing of the high part of the structure is the zone of sand-bearing bodies and is a favorable zone of hydrocarbon accumulation.  相似文献   

Mapping salt diapirs and salt diapir-affected areas using MLP neural network model and ASTER data     

《International Journal of Digital Earth》2013,6(2):143-157

Abstract

This study employs visible-near infrared and short wave infrared datasets of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) to map salt diapirs and salt diapir-affected areas using Multi-Layer Perceptron (MLP) in the Zagros Folded Belt, Iran, and introduces the role of earth observation technology and a type of digital earth processing in lithological mapping and geo-environmental impact assessment. MLP neural network model with several learning rates between 0.01 and 0.1 was carried out on ASTER L1B data, and the results were compared using confusion matrices. The most appropriate classification image for L1B input to MLP was produced by learning rate of 0.01 with Kappa coefficient of 0.90 and overall accuracy of 92.54%. The MLP result of input data set mapped lithological units of salt diapirs and demonstrated affected areas at the southern and western parts of the Konarsiah and Jahani diapirs, respectively. Field observations and X-ray diffraction analyses of field samples confirmed the dominant mineral phases identified remotely. It is concluded that MLP is an efficient approach for mapping salt diapirs and salt-affected areas.  相似文献   

Characteristics and influencing factors of shale oil reservoir: A case study of Luojia area in Zhanhua sag          下载免费PDF全文

JIA Shen  JIANG Zaixing 《中国地质调查》2014,7(2):13-20

In order to find out the characteristics and influencing factors of shale oil reservoir in the lower third member of Shahejie Formation of Paleogene in Luojia area of Zhanhua sag, the authors studied the lithology, space type, influencing factors and evaluation parameters of shale oil reservoir by comprehensive analysis of cores, thin sections, SEM and so on. The results show that mineral composition and sedimentary structure are two important factors, based on which the shale oil reservoir can be divided into seven types. The reservoir space of different lithological types varies greatly. Laminated argillaceous limestone and limestone reservoirs were mostly developed, and laminated gray mudstone reservoirs were relatively developed, followed by massive mudstone. The massive argillaceous limestone, massive grey mudstone and laminated siltstone reservoirs were less developed. The reservoir space of shale oil reservoir in the study area was mainly influenced by mineral composition, sedimentary structure, organic matter content and occurrence mode as well as diagenesis. On this basis, calcite content, laminar structure, TOC content, R_o and porosity were selected as evaluation parameters and the shale reservoir in Luojia area of Zhanhua sag was classified into three types: high quality reservoir, favorable reservoir and unfavorable reservoir.  相似文献   

概率神经网络在地震岩性反演中的应用     

彭刘亚  崔若飞  张亚兵 《煤田地质与勘探》2012,40(4):63-65,70

卧龙湖煤矿北二采区岩浆岩侵入8煤层的现象较为严重,同时该区煤层中构造煤比较发育,瓦斯富集问题较为突出。利用三维地震资料、测井曲线进行约束反演得到的波阻抗作为外部属性,并使用step-wise属性选择法确定合适数目的地震属性,利用概率神经网络技术(PNN)对该区进行孔隙度预测反演。孔隙度反演结果与波阻抗反演结果的对比表明:孔隙度较波阻抗对于识别瓦斯富集带具有更高的分辨能力;概率神经网络具有高稳定性、计算精度高等特点,可作为研究构造煤发育和瓦斯赋存的有效手段。   相似文献