Structural framework and Mesozoic–Cenozoic evolution of Ponta Grossa Arch, Paraná Basin, southern Brazil     

Michael Strugale  Sidnei Pires Rostirolla  Fernando Mancini  Carlos Vieira Portela Filho  Francisco Jos Fonseca Ferreira  Rafael Corrêa de Freitas 《Journal of South American Earth Sciences》2007,24(2-4):203-227

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A preliminary case study of potential ceramic raw materials in the Aileu area of Timor Leste     

J.V. Lisboa  J.M.F. Carvalho  A. Oliveira  C. Carvalho  J. Grade 《Journal of Asian Earth Sciences》2007,29(5-6):593-603

The newly independent country of Timor Leste is located in the eastern half of Timor Island (Indonesian archipelago). Geological studies of the country’s mineral resources and extractive activities are practically non-existent. There is evidence of the exploitation of ceramic raw materials at outcrop level and two small brick kilns, nowadays inactive, in the Dili and Aileu areas. Near Aileu, there are light-coloured silt-rich deposits, interpreted as overbank deposits, interbedded with ancient river terraces (post-Pliocene) overlying metamorphic bedrock. These sediments are the subject of this study, which encompassed geological mapping and preliminary characterisation. Tectonically, the area is a graben, preserving alluvium and colluvium deposits. Five channel samples representative of the silt-rich deposits were collected. Semi-quantitative mineralogical analysis shows that the samples are made of illite, quartz and kaolinite clays, with accessory illite/vermiculite interstratified minerals and K-feldspar. The chemical data show agreement with the estimated mineralogical composition. The grain size distribution points to a silt-dominated assemblage. Most samples have a satisfactory extrudability but deficient moulding properties. After firing, the sampled raw materials form a final product with possible ceramic capability for whiteware production.  相似文献   

A new algorithm to estimate sky condition based on 5 minutes-averaged values of clearness index and relative optical air mass     

H. F. Assunção  J. F. Escobedo  A. P. Oliveira 《Theoretical and Applied Climatology》2007,90(3-4):235-248

Summary This work describes a new algorithm to characterize sky condition in intervals of 5 min using four categories of sun exposition: apparent sun with cloud reflection effects; apparent sun without cloud effects; sun partially concealed by clouds; and sun totally concealed by clouds. The algorithm can also be applied to estimate hourly and daily sky condition in terms of the traditional three categories: clear, partially cloudy and cloudy day. It identifies sky conditions within a confidence interval of 95% by minimizing local climate and measurement effects. This is accomplished by using a logistic cumulative probability function to characterize clear sky and Weibull cumulative probability function to represent cloudy sky. Both probability functions are derived from frequency distributions of clearness index, based on 5 minutes-averaged values of global solar irradiance observed at the surface during a period of 6 years in Botucatu, Southeastern of Brazil. The relative sunshine estimated from the new algorithm is statistically comparable to the one derived from Campbell-Stocks sunshine recorder for both daily and monthly values. The new method indicates that the highest frequency of clear sky days occurs in Botucatu during winter (66%) and the lowest during the summer (38%). Partially cloudy condition is the dominant feature during all months of the year.  相似文献   

Mock 2dF and SDSS galaxy redshift surveys   总被引：1，自引：0，他引：1  

Shaun Cole  Steve Hatton  David H. Weinberg  & Carlos S. Frenk 《Monthly notices of the Royal Astronomical Society》1998,300(4):945-966

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Dynamical studies of cluster pairs in the Magellanic Clouds     

M. R. de Oliveira  H. Dottori  & E. Bica 《Monthly notices of the Royal Astronomical Society》1998,295(4):921-932

We performed N -body simulations of star cluster encounters with Hernquist's TREECODE in a CRAY YMP-2E computer under different initial conditions (relative positions and velocities, cluster sizes, masses and concentration degrees). The total number of particles per simulation ranged from 1024 to 20480. These models are compared with a series of isodensity maps of cluster pairs in the Magellanic Clouds. Evidence is found that during the interactions, transient morphological effects such as an expanded halo, isophotal deformation and isophotal twisting can occur as a result of tidal effects and dynamical friction. The simulations also show that different outcomes are possible depending on the initial parameters: (i) long-standing changes of concentration degree can occur after the collision; (ii) one member can disaggregate; or (iii) the pair can coalesce into a single cluster with a distinct structure compared with the original ones. These simulations can reproduce a wide range of morphological structures in observed cluster pairs.  相似文献   

Are the Venezuelan fault systems part of the southern Caribbean plate boundary?     

Carlos Schubert 《International Journal of Earth Sciences》1981,70(2):542-551

Three major fault systems have been recognized in Venezuela: the Oca, Boconó, and El Pilar fault zones. The Boconó-El Pilar system is an active, Late Pleistocene-Holocene fault system, which extends for over 1300 km between the Venezuela-Colombia border, through the Venezuelan Andes and along the northern Venezuelan coast, to the east of Trinidad. Recent tectonic evidence suggests that until the Late Tertiary or Early Quaternary, the Caribbean Plate-South America Plate boundary included the El Pilar and Oca fault systems. Since then, it has included the Boconó fault system. Right-lateral offset along these fault systems is not sufficient to derive the Caribbean Plate from Pacific crust; alternatively, the Caribbean Plate may have been a part of the South America Plate until comparatively recent geologic-time.

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Zusammenfassung Drei wichtige Bruchsysteme sind in Venezuela festgestellt worden: die Oca, Boconé und El Pilar Bruchzonen. Das Boconó-El-Pilar-System ist ein aktives, Spätpleistozänes-Holozänes System, daß sich über mehr als 1300 km erstreckt, von der venezolanischkolumbianischen Grenze, durch die venezolanischen Anden und längs der nördlichen venezolanischen Küste, bis östlich von Trinidad. Rezente tektonische Daten lassen andeuten, daß bis zum Spättertiär oder Frühquartär, die Grenze zwischen der Karibischen Platte und der Südamerika-Platte die El Pilar- und Oca-Bruchsysteme einschloß. Später hat sie das Boconó-Bruchsystem eingeschlossen. Rechtsinnige Blattverschiebung an diesen Bruchsystemen ist nicht groß genug, um die Karibische Platte als ein Stück pazifischer Kruste zu betrachten; oder aber, die Karibische Platte war mit der Südamerika-Platte vereinigt bis zu einem relativ jungen geologischen Alter.

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Resumen Se han establecido tres sistemas mayores de fallamiento en Venezuela: las zonas de falla de Oca, Boconó y El Pilar. El sistema de Boconó-El Pilar es un sistema de falla activo pleistoceno-holoceno, el cual se extiende por más de 1300 km entre la frontera colombo-venezolana, a traves de los Andes venezolanos y a lo largo de la costa norte de Venezuela, hasta más al este de Trinidad. Evidencias tectónicas recientes sugieren que hasta el Terciario Tardio o Cuatemario Temprano, el límite entre las Plaças del Caribe y de América del Sur incluía los sistemas de falla de Oca y El Pilar. Desde entonces incluye al sistema de falla de Boconó. El desplazamiento de rumbo hacia la derecha a lo largo de estos sistemas de fallamiento no es suficiente para derivar la Plaça del Caribe de la corteza pacifica; alternativamente, la Placa del Caribe puede haber sido parte de la Placa de América del Sur hasta una época geológica relativamente reciente.

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Dedicated to the memory of John D. Weaver.  相似文献   

Late Pleistocene glaciation of Páramo de La Culata,north-central Venezuelan Andes     

Dr. Carlos Schubert  Mr. Sam Valastro 《International Journal of Earth Sciences》1974,63(2):516-538

Late Pleistocene glacial features in the Páramo de La Culata region, north-central Venezuelan Andes, include: 1. depositional features: morainic till and fluvio-glacial deposits (terrace gravels); 2. sculptured features: glaciated valleys, cirques, horns, and arêtes; and 3. erosional features: striation and grooving, polished rock, roches moutonnées and whaleback forms, and erratic boulders. Two main levels of moraines were found, an older one at 2600 m elevation, and a younger one between 3000 and 3500 m. The difference in age is reflected by the higher degree of weathering, erosion, and vegetation cover of the lower level, as compared with the higher level. Radiocarbon dating, and a comparison and correlation of these glacial features with those of adjacent regions, indicates that the lower morainic level (2600 m) is probably the result of the main glacial advance of the Late Wisconsin Glaciation. The main morainic level (3000 to 3500 m) was probably formed by the latest Wisconsin glacial advance. The Late Pleistocene snow-line depression reached approximately 1200 m below the present snow-line (i. e., down to approximately 3500 m).  相似文献   

Geochemistry of actinolitic hornblendes from tonalitic rocks,Northern Portugal     

Carlos A.E De Albuquerque 《Geochimica et cosmochimica acta》1974,38(5):789-803

Chemical analyses are given for actinolitic hornblendes of tonalitic rocks from the Hercynian belt of Northern Portugal. The distribution of elements between amphibole and co-existing biotite is studied. The composition of the amphiboles is analysed in the light of experimental data on amphiboles and the physical conditions of crystallization inferred from the study of the biotite and rock series. The data on the biotites lead to the definition of a temperature of 800°C for the crystallization of actinolitic hornblendes with Mg/(Mg + Fe) ratios of 0·72-0·61 at pressures of about 3 Kb and fO₂ defined by FMQ.  相似文献   

The significance of giant seismites in the Plio‐Pleistocene Baza palaeo‐lake (S Spain)     

Pedro Alfaro  Luis Gibert  Massimo Moretti  Francisco J. García‐Tortosa  Carlos Sanz de Galdeano  Jesús Galindo‐Zaldívar  Ángel C. López‐Garrido 《地学学报》2010,22(3):172-179

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Climate‐driven cyclicity in an Early Cretaceous synrift lacustrine series (Aguilón sub‐basin,NE Spain)     

Ana R. Soria  Arsenio Muñoz  Carlos L. Liesa  Aránzazu Luzón  Alfonso Meléndez  M. Nieves Meléndez 《地学学报》2012,24(5):407-416

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