Textural and geochemical characteristics of the Ajali Sandstone,Anambra Basin,SE Nigeria: Implication for its provenance     

Moshood Niyi Tijani  Matthew Essien Nton  Ryuji Kitagawa 《Comptes Rendus Geoscience》2010,342(2):136-150

This study presents the mineralogical, textural and geochemical characteristics of the regional Maastrichtian Ajali Sandstone in Anambra Basin, SE Nigeria. The intent is to highlight possible constraints on the chemical weathering conditions of the source materials on one hand, and to infer the provenance on the other hand. The investigation approach involved field studies and collection of samples from 12 different outcrop locations, followed by laboratory studies involving grain-size analysis (GSA), major and trace elements analyses using the X-ray fluorescence (XRF) method as well as thin section petrography. Field studies show that the sandstones are friable at all locations and range in color from white in freshly cut stone, to reddish brown on weathering. In addition, the sandstone units are cross-bedded and show graded bedding exemplified by fining upward sequence. Textural examination indicates that the sandstones range from fine to medium sands, constituting about 76 to 99% sand fraction, with graphic mean grain size of 0.23 to 0.53 mm. Standard deviation (sorting) ranges from 0.56 to 1.24 Ø and implies moderately well sorted sediments. Inferred from the textural indices, the depo-environmental discrimination of the Ajali Sandstone revealed a fluvial/river system-dominated sedimentary process. The sandstones are quartz arenite with quartz greater than 90% and less than 5% K-feldspar which indicate a predominant basement source as also revealed by the heavy mineral assemblages. In addition, major elemental oxides shows SiO₂ content greater than 96% for the fresh Ajali Sandstone samples with extreme depletion of mobile oxides such as Na₂O, CaO and the ferromagnesian minerals through weathering and sedimentary processes. Provenance and tectonic setting discrimination using geochemical data and compositional maturity revealed typical felsic igneous-dominated cratonic environment while inter-elemental ratios (such as Zr/Cr, Y/Ni, Th/Sc, La/Sc and La/Co) and ternary plots (e.g. Th–Sc–Zr; La-Th–Sc and Th-Co-Zr) reflect passive continental margin setting for the Ajali Sandstone. Consequently, the source area is constrained to the Precambrian basement rock units of Adamawa-Oban massif areas to the east of the Anambra Basin and the adjacent Abakaliki Anticlinorium.  相似文献   

川东南庙高寺—二里场地区嘉陵江组层序地层与沉积相     

李文茂  李国蓉  张天操  李弢  金小燕  周大志 《海相油气地质》2010,15(2):36-44

下三叠统嘉陵江组可划分为2个三级层序,对应嘉一—嘉二、嘉三—嘉五两大地质时期。根据岩心和测井解释进一步识别出了6个四级层序和15个五级层序。这两个三级层序都由海侵体系域和高位体系域构成,沉积相都经历了由开阔环境向局限环境的转变。因此嘉陵江组含开阔台地和半局限—局限台地两大沉积相,同时可识别出6种亚相及20种微相。四级、五级层序在广大的台地区具有可比性,纵向上滩体位置变化不明显。嘉二1和嘉四1这两个时期处于特殊的海平面升降旋回阶段,台内滩相较发育;嘉一到嘉二期和嘉三、嘉四到嘉五期,经历了由开阔台地相的石灰岩沉积到局限台地相的膏岩、白云岩沉积两次大的相变,构成两轮沉积旋回。  相似文献   

基于长度贝叶斯生物量估算法的北部湾带鱼资源评估   总被引：1，自引：0，他引：1  

张曼  王雪辉  王淼娣  杜飞雁  孙典荣  王亮根  王跃中  许柳雄  邱永松 《海洋学报》2022,44(1):11-21

带鱼是南海西北部北部湾主要经济鱼类种群之一,估算其种群参数和评估其资源状况对北部湾渔业资源管理具有重要意义.本文利用2006-2016年北部湾带鱼(Trichiurus haumela)的生物学数据,通过长度贝叶斯生物量估算法(Length-based Bayesian Biomass Estimation Metho...  相似文献   

Bright spectroscopic binaries: III. Binary systems with orbital periods of P > 500 days     

Dennis Jack  Missael Alejandro Hernández Huerta  Faiber Danilo Rosas-Portilla  Klaus-Peter Schröder 《Astronomische Nachrichten》2024,345(1):e230123

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Modelling and interpreting the dependence of clustering on the spectral energy distributions of galaxies     

Lan Wang  Cheng Li  Guinevere Kauffmann  Gabriella De Lucia 《Monthly notices of the Royal Astronomical Society》2007,377(4):1419-1430

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Accurate extragalactic distances and dark energy: anchoring the distance scale with rotational parallaxes     

Rob P. Olling 《Monthly notices of the Royal Astronomical Society》2007,378(4):1385-1399

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Erratum: The donor stars of cataclysmic variables     

《Monthly notices of the Royal Astronomical Society》2007,382(4):1982-1984

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The RAVE survey: constraining the local Galactic escape speed     

Martin C. Smith  Gregory R. Ruchti  Amina Helmi  Rosemary F. G. Wyse  J. P. Fulbright  K. C. Freeman  J. F. Navarro  G. M. Seabroke  M. Steinmetz  M. Williams  O. Bienaymé  J. Binney  J. Bland-Hawthorn  W. Dehnen  B. K. Gibson  G. Gilmore  E. K. Grebel  U. Munari  Q. A. Parker  R.-D. Scholz  A. Siebert  F. G. Watson  T. Zwitter 《Monthly notices of the Royal Astronomical Society》2007,379(2):755-772

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The mass distribution in early-type disc galaxies: declining rotation curves and correlations with optical properties     

E. Noordermeer  J. M. van der Hulst  R. Sancisi  R. S. Swaters  T. S. van Albada 《Monthly notices of the Royal Astronomical Society》2007,376(4):1513-1546

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Empirical distributions of galactic λ spin parameters from the Sloan Digital Sky Survey     

X. Hernandez  Changbom Park  B. Cervantes-Sodi  Yun-Young Choi 《Monthly notices of the Royal Astronomical Society》2007,375(1):163-170

Using simple dimensional arguments for both spiral and elliptical galaxies, we present formulae to derive an estimate of the halo spin parameter λ for any real galaxy, in terms of common observational parameters. This allows a rough estimate of λ, which we apply to a large volume-limited sample of galaxies taken from the Sloan Digital Sky Survey data base. The large numbers involved (11 597) allow the derivation of reliable λ distributions, as signal adds up significantly in spite of the errors in the inferences for particular galaxies. We find that if the observed distribution of λ is modelled with a lognormal function, as often done for this distribution in dark matter haloes that appear in cosmological simulations, we obtain parameters  λ₀= 0.04 ± 0.005  and  σ_λ= 0.51 ± 0.05  , interestingly consistent with values derived from simulations. For spirals, we find a good correlation between empirical values of λ and visually assigned Hubble types, highlighting the potential of this physical parameter as an objective classification tool.  相似文献