水下喷发火山碎屑岩储层特征及主控因素:以新西兰Taranaki盆地中新世Kora火山为例     

唐华风  王寒非  BenKENNEDY  张芯语  MarcosROSSETTI  AlanPatrickBISCHOFF  AndrewNICOL 《地学前缘》2021,28(1):375-387

新西兰Taranaki盆地中新世Kora火山是海底喷发形成的碎屑岩型火山,可代表浅埋藏火山岩的储层特征.本文根据5口钻井的孔隙度、渗透率、孔隙孔径和铸体薄片开展Kora火山的储层特征、储集空间组成、缝宽以及原生和次生孔隙之间关系的分析.研究结果如下:(1)储集空间主要为次生孔隙,然后是裂缝和原生孔隙;Kora火山具有高...  相似文献   

The role of macrophytes as a refuge and food source for the estuarine isopod Exosphaeroma hylocoetes ( )     

Tony O. Henninger  P. William FronemanNicole B. Richoux  Alan N. Hodgson 《Estuarine, Coastal and Shelf Science》2009

The role of submerged macrophytes as refugia from fish predation and as possible food sources for the estuarine isopod Exosphaeroma hylocoetes ( Barnard, K.H., 1940) was investigated. Laboratory experiments tested the effectiveness of artificial vegetation, replicating submerged vegetation, in enabling isopods to elude selected fish predators Rhabdosargus holubi, Glossogobius callidus, Monodactylus falciformis and Clinus cottoides. Isopods preferentially hid in the vegetation (>90%), even in absence of fish. The predatory fish had varying success in finding isopods within the vegetation. Isopod mortality ranged from 2% (R. holubi) to a maximum of 87% (C. cottoides) within vegetation, depending on the fish predator present. Stable isotope and fatty acid analyses ruled out the submerged macrophyte Ruppia maritima and inundated fringing grasses as direct food sources, but highlighted the epiphytic biota (mainly diatoms) found on the submerged vegetation and sediments as more likely food sources. These findings are consistent with gut content analyses. The results suggest that the close association of E. hylocoetes with R. maritima is the result of the vegetation providing the isopod with a refuge against fish predation as well as areas of increased food availability.  相似文献   

The internal tide of the Gareloch,a Scottish Fjord     

Peter E. Robins  Alan J. Elliott 《Estuarine, Coastal and Shelf Science》2009

Previous observations in the Gareloch, a Scottish silled fjord, have identified yet failed to explain the baroclinic circulation pattern. Additional fieldwork was carried out in April 2005, showing the loch to be stratified with two distinct layers and currents in each layer 180° out of phase at the M₂ frequency. The currents did not display the expected sinusoidal signal that is characteristic of the tide and instead were pulsated and stronger than predicted by barotropic forcing. Fourier analysis showed that the flow was dominated by short period non-linear oscillations that were harmonics of the semi-diurnal tide. Two hydrostatic estuarine models were applied to the Gareloch: a 2D vertical model (SLICE) and a 3D model (ECOMSED). Both models were capable of reproducing the observed (2005) baroclinic circulation at the M₂ time scale but failed to simulate the higher frequency, non-linear oscillations. However, each model generated higher harmonics in idealised scenarios. Because lateral motion was negligible and SLICE was an order of magnitude more efficient than ECOMSED, the 2D model was used to simulate the higher harmonics and showed that their generation was attributed to the non-linear distortion of the internal tide. When the internal Froude number (determined by barotropic velocity, stratification and water depth) was increased from a sub-critical value, non-linear advection became more important and higher harmonics were generated. The internal tide was further modified by wave reflection and interaction off steep boundaries, and by flow over the sill.  相似文献   

Growth dynamics and bioactivity variation of the Mediterranean demosponges Agelas oroides (Agelasida, Agelasidae) and Petrosia ficiformis (Haplosclerida, Petrosiidae)     

Cristina Ferretti  Simone Vacca  Chiara De Ciucis  Barbara Marengo  Alan R. Duckworth  Renata Manconi  Roberto Pronzato  & Cinzia Domenicotti 《Marine Ecology》2009,30(3):327-336

Growth dynamics and bioactivity variation of the Mediterranean demosponges Agelas oroides and Petrosia ficiformis were investigated over 15 months at Paraggi and Colombara within the Marine Reserve of Portofino Promontory (Mediterranean Sea, Ligurian Sea, Italy). For both species, growth rates varied between individuals and were unaffected by initial sponge size. The two species showed a different trend in growth pattern: A. oroides did not vary significantly between seasons, sites and depths; in contrast, some individuals of P. ficiformis showed a seasonal pattern, shrinking during winter as water temperature decreased and growing during summer when water temperature increased. Differences in growth between the two species may result from different reproductive cycles, food availability, species-specific thermophily and patterns of spatial competition. Moreover, spatial competition probably induced sponges to produce bioactive secondary molecules. Spatial and temporal variation of bioactivity of both species was examined for the first time by studying its effect on human neuroblastoma cells. The bioactivity of A. oroides extracts differed significantly between seasons, sites and depths, whereas the cytotoxicity of P. ficiformis differed significantly between seasons and depths (differences for sites were not determined). These results suggest the possible influence of environmental factors on bioactive metabolite biosynthesis.  相似文献   

胶州湾浮游原生生物时空分布特征——丰度周年变化及与环境因子间的关系   总被引：2，自引：0，他引：2  

姜勇  许恒龙  朱明壮  陈旭淼  范鑫鹏  姜佳枚  Alan War-ren  胡晓钟  宋微波 《中国海洋大学学报(自然科学版)》2010,40(3)

为了解胶州湾浮游原生生物时空分布特征及与环境因子间的关系,自2007年6月～2008年5月,对青岛胶州湾内5个站点表层水的浮游原生生物丰度及环境因子进行了累计24次的周年采样调查及定性、定量分析.结果显示:(1) 浮游原生生物周年变动具有2个高峰,分别出现在4月和8月;(2) 浮游硅藻、鞭毛藻和纤毛虫的丰度周年变动均为双峰型:春节(4月)高峰、秋节(8月)高峰;(3) 浮游原生生物丰度与叶绿素a和溶解氧呈显著性相关,而其群落结构的变化与盐度、溶解氧、硝态氮和亚硝态氮的组合呈显著性相关.本工作为进一步探讨富营养化的内湾型近岸水体内原生生物生态学结构与功能提供了一份必要的基础资讯.  相似文献   

Remote sensing of terrestrial impact craters: The TanDEM‐X digital elevation model          下载免费PDF全文

Manfred Gottwald  Thomas Fritz  Helko Breit  Birgit Schättler  Alan Harris 《Meteoritics & planetary science》2017,52(7):1412-1427

With the TanDEM‐X digital elevation model (DEM), the terrestrial solid surface is globally mapped with unprecedented accuracy. TanDEM‐X is a German X‐band radar mission whose two identical satellites have been operated in single‐pass interferometer configuration over several years. The acquired data are processed to yield a global DEM with 12 m independent posting and relative vertical accuracies of better than 2 m and 4 m in moderate and mountainous terrain, respectively. This DEM provides new opportunities for space‐borne remote‐sensing studies of the entire sample of terrestrial impact craters. In addition, it represents an interesting repository to aid in the search for new impact crater candidates. We have used the TanDEM‐X DEM to investigate the current set of confirmed impact structures. For a subsample of the craters, including small, midsized, and large structures, we compared the results with those from other DEMs. This quantitative analysis demonstrates the excellent quality of the TanDEM‐X elevation data. Our findings help to estimate what can be gained by using the TanDEM‐X DEM in impact crater studies. They may also be beneficial in identifying the regions and morphologies where the search for currently unknown impact structures might be most promising.  相似文献   

Sandy beach ecosystems: key features, sampling issues, management challenges and climate change impacts   总被引：4，自引：0，他引：4  

Thomas A. Schlacher  Dave S. Schoeman  Jenifer Dugan  Mariano Lastra  Alan Jones  Felicita Scapini  & Anton McLachlan 《Marine Ecology》2008,29(S1):70-90

Escalating pressures caused by the combined effects of population growth, demographic shifts, economic development and global climate change pose unprecedented threats to sandy beach ecosystems worldwide. Conservation of beaches as functional ecosystems and protection of their unique biodiversity requires management interventions that not only mitigate threats to physical properties of sandy shores, but also include ecological dimensions. Yet, beach management remains overwhelmingly focused on engineering interventions. Here we summarise the key outcomes of several workshops, held during the 2006 Sandy Beach Ecology Symposium in Vigo, Spain, that addressed issues of climate change, beach management and sampling methodology. Because efficient communication between managers and ecologists is critical, we summarise the salient features of sandy beaches as functional ecosystems in 50 'key statements'; these provide a succinct synopsis of the main structural and functional characteristics of these highly dynamic systems. Key outcomes of the workshops include a set of recommendations on designs and methods for sampling the benthic infaunal communities of beaches, the identification of the main ecological effects caused by direct and indirect human interventions, the predicted consequence of climate change for beach ecosystems, and priority areas for future research.  相似文献   

Wondering about …. Geography—Its nature and its relevance?     

Tony Binns  Alan Kinder 《New Zealand geographer》2019,75(2):93-95

In the context of the current review of New Zealand's National Certificate of Educational Achievement (NCEA), the paper reflects on the nature and relevance of geography in education, life and work. The context of school geography programmes is critically examined, and a checklist of points for further consideration and action is presented.  相似文献   

Textural Quantification and Classification of Drill Cores for Geometallurgy: Moving Toward 3D with X-ray Microcomputed Tomography (µCT)     

Guntoro  Pratama Istiadi  Ghorbani  Yousef  Butcher  Alan R.  Kuva  Jukka  Rosenkranz  Jan 《Natural Resources Research》2020,29(6):3547-3565

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Retreat of the Smith Sound Ice Stream in the Early Holocene     

Anne E. Jennings  John T. Andrews  Brett Oliver  Maureen Walczak  Alan Mix 《Boreas: An International Journal of Quaternary Research》2019,48(4):825-840

Nares Strait, a major connection between the Arctic Ocean and Baffin Bay, was blocked by coalescent Innuitian and Greenland ice sheets during the last glaciation. This paper focuses on the events and processes leading to the opening of the strait and the environmental response to establishment of the Arctic‐Atlantic throughflow. The study is based on sedimentological, mineralogical and foraminiferal analyses of radiocarbon‐dated cores 2001LSSL‐0014PC and TC from northern Baffin Bay. Radiocarbon dates on benthic foraminifera were calibrated with ΔR = 220±20 years. Basal compact pebbly mud is interpreted as a subglacial deposit formed by glacial overriding of unconsolidated marine sediments. It is overlain by ice‐proximal (red/grey laminated, ice‐proximal glaciomarine unit barren of foraminifera and containing >2 mm clasts interpreted as ice‐rafted debris) to ice‐distal (calcareous, grey pebbly mud with foraminifera indicative of a stratified water column with chilled Atlantic Water fauna and species associated with perennial and then seasonal sea ice cover) glacial marine sediment units. The age model indicates ice retreat into Smith Sound as early as c. 11.7 and as late as c. 11.2 cal. ka BP followed by progressively more distal glaciomarine conditions as the ice margin retreated toward the Kennedy Channel. We hypothesize that a distinct IRD layer deposited between 9.3 and 9 (9.4–8.9 1σ) cal. ka BP marks the break‐up of ice in Kennedy Channel resulting in the opening of Nares Strait as an Arctic‐Atlantic throughflow. Overlying foraminiferal assemblages indicate enhanced marine productivity consistent with entry of nutrient‐rich Arctic Surface Water. A pronounced rise in agglutinated foraminifers and sand‐sized diatoms, and loss of detrital calcite characterize the uppermost bioturbated mud, which was deposited after 4.8 (3.67–5.55 1σ) cal. ka BP. The timing of the transition is poorly resolved as it coincides with the slow sedimentation rates that ensued after the ice margins retreated onto land.  相似文献