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961.
根据最新区域地质调查的代表剖面,在分析研究下二叠统开心岭群、上二叠统乌丽群的岩性组合特征、沉积类型、古生物面貌的基础上,将二叠系建立5个岩石地层单位和相应的5个生物地层单位,代表栖霞期—长兴期地层层序与生物序列;区内生物性质属特提斯动物群和华夏植物群;青南乌丽与藏北双湖及昌都妥坝属同一含煤建造,成煤期为龙潭中期—长兴期。 相似文献
962.
963.
L. Monaco M. Bellazzini F. R. Ferraro E. Pancino 《Monthly notices of the Royal Astronomical Society》2005,356(4):1396-1402
We present an analysis of the density profile in the central region of the Sagittarius dwarf spheroidal galaxy. A strong density enhancement of Sgr stars is observed. The position of the peak of the detected cusp is indistinguishable from the centre of M54. The photometric properties of the cusp are fully compatible with those observed in the nuclei of dwarf elliptical galaxies, indicating that the Sgr dSph would appear as a nucleated galaxy independently of the presence of M54 at its centre. 相似文献
964.
965.
I. D. Karachentsev O. G. Kashibadze D. I. Makarov R. B. Tully 《Monthly notices of the Royal Astronomical Society》2009,393(4):1265-1274
We use updated data on distances and velocities of galaxies in the proximity of the Local Group (LG) in order to establish properties of the local Hubble flow. For 30 neighbouring galaxies with distances 0.7 < D LG < 3.0 Mpc, the local flow is characterized by the Hubble parameter H loc = (78 ± 2) km s−1 Mpc−1 , the mean-square peculiar velocity σv = 25 km s−1 , corrected for errors of radial velocity measurements (∼4 km s−1 ) and distance measurements (∼10 km s−1 ) , as well as the radius of the zero-velocity surface R 0 = (0.96 ± 0.03) Mpc. The minimum value for σv is achieved when the barycentre of the LG is located at the distance Dc = (0.55 ± 0.05) D M31 towards Andromeda galaxy (M31) corresponding to the Milky Way (MW)-to-M31 mass ratio M MW / M M31 ≃ 4/5 . In the reference frame of the 30 galaxies at 0.7–3.0 Mpc, the LG barycentre has a small peculiar velocity ∼(24 ± 4) km s−1 towards the Sculptor constellation. The derived value of R 0 corresponds to the total mass M T (LG) = (1.9 ± 0.2) 1012 M⊙ with Ωm = 0.24 and a topologically flat universe, a value in good agreement with the sum of virial mass estimates for the MW and M31. 相似文献
966.
四川西部松潘—甘孜地区广泛分布一套三叠系黑色砂板岩层系,由于其岩性单调、古生物化石贫乏,给该区地层划分、对比带来极大困难。因此,从锶同位素地层学基本原理出发,对甘孜北部西康群新都桥组中薄层状灰岩样品进行了锶同位素组成测定。结果表明,6件样品的N(87Sr)/N(86Sr)分别为0.708688、0.708659、0.708907、0.708223、0.708341、0.708266,平均为0.708514。表明该地层的碳酸盐岩样品可能遭受了不同程度的成岩蚀变,多数样品的锶同位素组成偏离同时代的全球海水锶同位素组成。 相似文献
967.
中国盐湖锂资源非常丰富,但由于镁锂比高、镁锂性质相似而使得二者难以分离,锂资源开发利用成本较高。本文采用组贡献法对LiCl·2Al(OH)3·2H2O的标准生成吉布斯自由能进行了估算,在热力学计算的基础上绘制了298.15K时Li+-Al3+-Cl--H2O体系和Li+-Mg2+-Al3+-Cl--H2O系的电位-pH(φ-pH)图。计算结果表明,通过调控体系的pH,可使溶液中的Li+与Al形成沉淀而Mg2+仍留在溶液中,从而实现溶液中的镁锂分离。在理论计算的基础上进行了镁锂分离的验证实验,实验结果与热力学计算结果基本吻合,镁锂分离效果良好。 相似文献
968.
ABSTRACT. Eight relict rock-slope failures (RSFs) on Skiddaw Group terrain in the Lake District, northwest England, are described. Five of the failures are rockslides, one is a product of slope deformation, and two are compound features with evidence for sliding and deformation in different sectors. As none appears to have been overrun and modified by glacier ice it is concluded that they all post-date the Last Glacial Maximum (LGM ; c. 21 ± 3 cal. ka bp ). Slope stress readjustments resulting from glacial and deglacial influences are considered to have weakened the slopes, and application of the term paraglacial is appropriate. Permafrost aggradation and degradation, seismic activity and fluvial erosion are among processes that may have contributed to failure at certain sites. The failures are significant as potential debris sources during future ice advances, contributing to valley widening and cirque enlargement and, possibly, for acting as sites of cirque initiation. Previously, Skiddaw Group rocks have been regarded as homogeneous and of limited resistance to the weathering and erosion associated with Quaternary glacial, periglacial and fluvial processes. These characteristics and processes have been used to explain the steep smooth slopes and rounded hills that dominate Skiddaw Group terrain. Rock-slope failure has also helped shape this terrain and should be incorporated in future interpretations of landscape development. 相似文献
969.
C. R. Twidale 《Australian Journal of Earth Sciences》2013,60(2):131-147
Slopes are the fundamental unit of the physiographic landscape. Yet the reasons for variations in their morphology and inferred mode of development are not well understood. The problem is complex, but the slope budget, which results primarily from the interplay of climatically induced factors and structure is significant: where the erosion of the upper slope elements surpasses that on the lower, parallel retreat prevails, but when the reverse is the case, slope decline is dominant. Complications are introduced by such factors as climatic change and fluctuations of baselevel, both local and general. But structural factors can and do override all others. A knowledge of geomorphic history, and of processes and their effectiveness under various circumstances, in advance of that usually at our disposal at present is necessary before slopes can satisfactorily be analysed. It appears unlikely that there is a universal law of slope development.. 相似文献
970.