Intercomparison of Multiple Hydroclimatic Datasets across the Lower Nelson River Basin,Manitoba, Canada     

《大气与海洋》2012,50(4):262-278

ABSTRACT

This study evaluates the 1981–2010 spatiotemporal differences in six available climate datasets (daily total precipitation and mean air temperature) over the Lower Nelson River Basin (LNRB) in ten of its sub-watersheds at seasonal and annual time scales. We find that the Australian National University spline interpolation (ANUSPLIN), and inverse distance weighted (IDW) interpolated observations from 14 Environment and Climate Change Canada (ECCC) meteorological stations show dry biases, whereas reanalysis products tend to overestimate precipitation across most of the basin. All datasets exhibit prominent disagreement in precipitation trends whereby the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim) and European Union Water and Global Change (WATCH) Forcing Data ERA-Interim (WFDEI) show exceptional wetting trends, while the IDW and ANUSPLIN data manifest drying trends. Mean air temperature trends generally agree across most of the datasets; however, the North American Regional Reanalysis (NARR) and IDW show stronger warming relative to other datasets. Overall, analyses of the different climate datasets and their ensemble reveal that the choice of input dataset plays a crucial role in the accurate estimation of historical climatic conditions, particularly when assessing trends, for the LNRB. Using the ensemble has the distinct advantage of preserving the unique strengths of all datasets and affords the opportunity to estimate the uncertainty for hydrologic modelling and climate change impact studies.  相似文献   

Geomorphic positioning and depositional dynamics of river systems in Lower Siwalik basin,Kumaun Himalaya     

U. K. Shukla  D. S. Bora  C. K. Singh 《Journal of the Geological Society of India》2009,73(3):335-354

Qualitative and quantitative analysis of river systems in the Lower Siwalik sequence has enabled characterization of channel patterns, river metamorphosis and resulting sandstone body evolution in time and space. Processes related six lithofacies repeat to generate 8–10 m thick multistoried sandstone complexes deposited in perennial channel belts. Based on lateral mapping of the sandstone bodies, the surfaces of genetic significance ranging from 3^rd, 4^th and 5^th order, suggest presence of meandering, braided and anastomosing river patterns that were responsible for the Lower Siwalik sedimentation. Variation in local base-level in response to allogenic factors including climate and tectonics forced river systems to acquire different patterns. Eustasy seems to control large-scale basin level changes. Quantitatively reconstructed morphological parameters and their comparison with modern and ancient analogues, supported by other independent evidences such as stratigraphical position of sandstone bodies in vertically measured columns and mineralogical characteristics of channel sandstones, enabled to decipher the geomorphic positioning of the Lower Siwalik channels in distal parts of megafan and interfluve areas within the foreland basin setting.  相似文献   

Detailed gravity studies over Jabera — Damoh region of the Vindhyan basin (Central India) and crustal evolution     

Ravi P. Srivastava  Nimisha Vedanti  O. P. Pandey  V. P. Dimri 《Journal of the Geological Society of India》2009,73(5):715-723

Vindhyan Basin of Central India situated just north of SONATA rift zone, forms one of the major geotectonic segment of the Indian subcontinent which is associated with complex thermo-tectonic history. Southern part of this basin is known to contain favorable conditions for hydrocarbon entrapment. Keeping this in view, a detailed gravity survey network comprising 40 gravity bases and 1500 data points in an area of about 110 × 100 km² was planned in and around Jabera-Damoh region. Analysis of Bouguer and free air gravity anomaly maps, prepared using fractal based gridding method, indicates presence of two sedimentary basins (Jabera and Damoh) faulted on either sides beside ridge like features. However, well-known Jabera domal structure appeared to be a shallow feature only. Inversion of gravity data further reveals presence of 5 to 6 km thick Vindhyan sediments in the Jabera basin which are underlain by Mahakoshal/Bijawar group of rocks, resting directly over the lower crust, thereby indicating almost total absence of granitic crust from this region. It appears that due to an underlying thermal anomaly, the entire region may have been subjected to sustained uplift, deformation, erosion and consequent crustal extension during early to mid Proterozoics which brought high velocity mafic crust to such shallow levels.  相似文献   

Braided rivers within an arid alluvial plain (example from the Lower Triassic,western German Basin): recognition criteria and expression of stratigraphic cycles     

S. BOURQUIN  F. GUILLOCHEAU  S. PÉRON 《Sedimentology》2009,56(7):2235-2264

Based on a detailed sedimentological analysis of Lower Triassic continental deposits in the western Germanic sag Basin (i.e. the eastern part of the present‐day Paris Basin: the ‘Conglomérat basal’, ‘Grès vosgien’ and ‘Conglomérat principal’ Formations), three main depositional environments were identified: (i) braided rivers in an arid alluvial plain with some preserved aeolian dunes and very few floodplain deposits; (ii) marginal erg (i.e. braided rivers, aeolian dunes and aeolian sand‐sheets); and (iii) playa lake (an ephemeral lake environment with fluvial and aeolian sediments). Most of the time, aeolian deposits in arid environments that are dominated by fluvial systems are poorly preserved and particular attention should be paid to any sedimentological marker of aridity, such as wind‐worn pebbles (ventifacts), sand‐drift surfaces and aeolian sand‐sheets. In such arid continental environments, stratigraphic surfaces of allocyclic origin correspond to bounding surfaces of regional extension. Elementary stratigraphic cycles, i.e. the genetic units, have been identified for the three main continental environments: the fluvial type, fluvial–aeolian type and fluvial/playa lake type. At the time scale of tens to hundreds of thousands of years, these high‐frequency cycles of climatic origin are controlled either by the groundwater level in the basin or by the fluvial siliciclastic sediment input supplied from the highland. Lower Triassic deposits from the Germanic Basin are preserved mostly in endoreic basins. The central part of the basin is arid but the rivers are supplied with water by precipitation falling on the remnants of the Hercynian (Variscan)–Appalachian Mountains. Consequently, a detailed study of alluvial plain facies provides indications of local climatic conditions in the place of deposition, whereas fluvial systems only reflect climatic conditions of the upstream erosional catchments.  相似文献   

Ammonites from the <Emphasis Type="Italic">Deshayesites</Emphasis> genus from Aptian (Lower Cretaceous) sediments in the Mountainous Crimea     

I. A. Mikhailova  E. Yu. Baraboshkin 《Moscow University Geology Bulletin》2009,64(1):29-34

Stratigraphically important ammonites Deshayesites ex gr. deshayesi (d’Orbigny, 1840), Deshayesites sp. juv., and Paradeshayesites aff. callidiscus [Casey, 1961] from lower Aptian pelagic sediments at the Verkhorech’e Village have been described and depicted. The new finds and revision of previously found ammonites allow the recognition of ammonite zones Deshayesites volgensis and Deshayesites deshayesi in the Southwestern Crimea.  相似文献   

Early Cretaceous fish trails from La Rioja, Spain     

Loïc Costeur  Rubn Ezquerra 《Cretaceous Research》2009,30(4):1027-1030

We report a new find of the fish trail Undichna unisulca in fluvial sediments of the Lower Cretaceous Oliván Group of the Cameros Basin (Aptian-Albian; Valtrujal, La Rioja, northern Spain). It is the second Mesozoic record of Undichna unisulca after the first discovery in the Lower Cretaceous of central Spain (Las Hoyas, Cuenca, central Spain). The trails are characterized by single sinusoidal waves which in this case are often surrounded by well-preserved lateral levees that rule out an undertrail hypothesis.The continental depositional setting, a floodplain fluvial system, reflects the known broad palaeoenvironmental distribution of Undichna and confirms its occurrences in freshwater settings.  相似文献   

海南岛西北部早石炭世褶颊类三叶虫化石的发现及其古生物地层学意义   总被引：1，自引：0，他引：1  

姚华舟  袁金良  张仁杰 《地质论评》2009,55(5):614-619

海南岛西北部白沙县金波老村附近南好组第二段首次发现Australosutura sp.,Conophillipsia sp.,Hunanoproetus sp.,Linguaphillisia sp.,Weberiphillipsia cf. linguiformis Yuan & Li,和Werberiphillipsia sp.等5属6种褶颊类三叶虫,据三叶虫生物地层年代确认,为分布广泛的早石炭世早期的属种。三叶虫化石的发现,不仅扩展了早石炭世三叶虫动物群的地理分布,而且为白沙地区南好组地层年代的修订及与岛内不同地区南好组的地层对比及与岛外同期地层的对比提供了精确的三叶虫生物地层的重要化石材料。  相似文献   

辽西下白垩统义县组湖相碳酸盐岩及其沉积环境研究   总被引：3，自引：0，他引：3  

陈登辉  巩恩普  梁俊红  李永杰 《地质论评》2009,55(6):896-904

辽西地区下白垩统义县组是热河生物群产出的主要地层,其中产出大量精美的生物化石,但是由于受到后期构造破坏和风化作用影响,难以开展野外工作,热河生物群产出的古地理环境及盆地沉积环境的研究程度仍然较低。该组地层中湖相碳酸盐岩比较发育,本次工作主要对辽西义县组老公沟—金刚山剖面4个沉积层中产出的多层湖相碳酸盐岩沉积层进行了深入研究。通过野外工作结合室内镜下鉴定,分析了义县组湖相碳酸盐岩的产出状态和岩石类型,划分出5个岩相类型和两个相组合。结合野外实测剖面中碳酸盐岩与其它沉积岩层的组合关系对义县组湖相碳酸盐沉积环境进行了探讨,发现义县组湖相碳酸盐岩主要为洪水—漫湖沉积体系中较浅的储水洼地和滨浅湖半咸水沉积环境,并建立了义县组湖相碳酸盐岩沉积相模式。  相似文献   

陕西勉县后沟-大坪山锰矿床地质-地球化学特征及控矿因素   总被引：2，自引：0，他引：2       下载免费PDF全文

杨钟堂  乔耿彪  李智明  杨晓勇  黄洪平  蓝翔华  宋忠宝  刘小舟  万伟 《地质科学》2009,44(1):88-102

近年里在南秦岭磷.锰成矿带中-东段的后沟-大坪山一带发现3条锰-磷矿化带,并圈定出3个锰矿体.锰矿体均赋存于下寒武统塔南坡组碳泥质岩-碳酸盐岩内,属海相沉积变质+改造类型锰矿床.本文在初步总结该区锰矿成矿地质特征的基础上,对优质锰矿成矿条件和成矿控制作用进行了系统深入的探讨.研究表明：本区锰成矿元素沉积受扬子地台北缘具有准稳定性质的前震旦纪基底裂陷构造盆地的控制,具有磷-锰共存、低Co、低Co/Ni比以及相对较高富集系数的Ni、Pb、Zn和B等成矿地球化学特征,成矿物质具有多源性,主要与扬子地块前震旦纪基底的陆源风化迁移沉积有关.锰成矿作用具有明显的盆控性、层控性和岩性专属性.优质锰受磷、锰分离沉积控制,层位上具有下磷上锰分层成矿特点.基于上述研究,本文提出含锰灰岩（白云质灰岩）和含黄铁矿碳质千枚岩为本区锰矿找矿标志.  相似文献   

西南天山下二叠统小提坎立克组火山岩地球化学特征   总被引：3，自引：1，他引：2  

李建兵  魏永峰  杜红星  孙涛 《新疆地质》2009,27(4)

小提坎里克组火山岩分布于西南天山南缘的塔里木微板块之塔里木北缘古生代活动陆缘,主要由中酸性陆相火山岩组成.地球化学特征显示:该岩石富碱、富钾,其中酸性火山岩稀土总量高,轻重稀土分异不明显,负Eu异常明显,稀土分布曲线呈显著"V"字形态,明显富集Rb,Th,K亏损Ba,相对富集Ce,Sm,而相对亏损Ta.地球化学特征表明该火山岩形成于板内伸展环境.通过锆石U-Pb测年获得(296.2±6.1)Ma的年龄数据,时代为早二叠世.综合南天山已有研究成果,小提坎里克组火山岩与分布于托什干河上游一带的早二叠世高钾钙碱性的巴雷公花岗岩属同源岩浆的产物,在早二叠世时,西南天山已演变为一个统一的区域伸展背景.由此可以推断,南天山晚古生代碰撞造山的峰期在早二叠世之前已结束,南天山古洋盆在早二叠世之前已经闭合.  相似文献