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991.
Colluvial deposits are commonly found throughout the Serra do Mar escarpment in Brazil. This article discusses predisposing geotechnical and geological factors related to the movement of a colluvium deposit located at km 29 of the Brazilian Federal Highway 116, Rio de Janeiro/RJ (BR-116/RJ). During the highway construction in mid-1976, an excavation of the toe of the slope was implemented, exacerbating preexisting movement. In order to understand the behavior of this deposit, field investigations, monitoring, and laboratory tests, as well as theoretical analyses were carried out. A subsoil survey in the area indicated the presence of a colluvium-filled paleo-thalweg. The site is located in a region with a specific geomorphology that favors significant sources of recharge to groundwater. The highly foliated rock has persistent parallel fractures, with a dip favorable to the groundwater flow in the direction of the slope. Statistical analyses were performed and good correlations were observed for rainfall, movements, groundwater table (GWT) levels, piezometer readings, and the discharge from deep horizontal drains (DHDs). The installation of the DHDs led to a GWT draw-down of 15 m, as well as reductions in movement and artesian pressure. The drains that presented the best performance were those installed in the colluvium-filled paleo-thalweg. Nevertheless, the present number of DHDs installed is not sufficient to permanently lower the GWT and stop the creep movement in the slope which was reactivated during a period of intense rainfall. Stability analysis indicates that a proper slope stability condition may be achieved by reducing the GWT level. 相似文献
992.
993.
994.
David A. Wake Robert C. Nichol Daniel J. Eisenstein Jon Loveday Alastair C. Edge Russell Cannon Ian Smail Donald P. Schneider Ryan Scranton Daniel Carson Nicholas P. Ross Robert J. Brunner Matthew Colless Warrwick J. Couch Scott M. Croom Simon P. Driver José da Ângela Sebastian Jester Roberto de Propris Michael J. Drinkwater Joss Bland-Hawthorn Kevin A. Pimbblet Isaac G. Roseboom Tom Shanks Robert G. Sharp Jon Brinkmann 《Monthly notices of the Royal Astronomical Society》2006,372(2):537-550
995.
Luis Gustavo Ferreira-Oliveira Rosemarie Rohn 《Journal of South American Earth Sciences》2010,29(2):371-380
Conchostracan fossils are abundant and relatively diversified in the Rio do Rasto Formation (Passa Dois Group, Paraná Basin, southern Brazil), but leaiids (‘Leaia pruvosti’ [Reed, F.R.C., 1929. Novos Phyllopodos Fósseis do Brasil. Boletim do Serviço Geológico e Mineralógico do Brasil 34, 2–16]) were previously found at only one locality of the formation in the northern Santa Catarina State. New specimens of the Family Leaiidae, collected from two outcrops in central Paraná State near the top of the formation, stimulated a revision of related taxa. Both the new and the previously known leaiids are herein assigned to Hemicycloleaia mitchelli [Etheridge Jr., R., 1892. On Leaia mitchelli Etheridge. Proceedings of the Linnean Society of New South Wales 7, 307–310] based on the presence of three carinae and subovate shape. This species was originally recorded in the upper Tatarian (Wuchiapingian, Late Permian) of Sydney Basin, eastern Australia and therefore corroborates the interpretation that the leaiid bearing strata of the Rio do Rasto Formation cannot be younger than Permian. H. mitchelli possibly was one of the most widespread, eurytopic and conservative Late Paleozoic conchostracans of Gondwana (although records from Africa, India and Antarctica must still be confirmed) and it was also found in the Tatarian of Russia. The sudden disappearance of leaiids after their apparent success is consistent with the hypothesis about the biotic crisis around the Permo-Triassic boundary. 相似文献
996.
Marcelo Augusto de Oliveira Roberto Dall’Agnol Fernando Jacques Althoff Albano Antonio da Silva Leite 《Journal of South American Earth Sciences》2009,27(2-3):146-160
The Archean sanukitoid Rio Maria Granodiorite yielded zircon ages of ~2.87 Ga and is exposed in large domains of the Rio Maria Granite-Greenstone Terrane, southeastern Amazonian craton. It is intrusive in the greenstone belts of the Andorinhas Supergroup, in the Arco Verde Tonalite and Caracol Tonalitic Complex (older TTGs). Archean potassic leucogranites, younger TTGs and the Paleoproterozoic granites of Jamon Suite are intrusive in the Rio Maria Granodiorite.The more abundant rocks of the Rio Maria Granodiorite have granodioritic composition and display medium to coarse even-grained textures. These rocks show generally a gray color with greenish shades due to strongly saussuritized plagioclase, and weak WNW-ESE striking foliation. The significant geochemical contrasts between the occurrences of Rio Maria Granodiorite in different areas suggest that this unit corresponds in fact to a granodioritic suite of rocks derived from similar but distinct magmas. Mingling processes involving the Rio Maria Granodiorite and similar mafic to intermediate magmas are able to explain the constant occurrence of mafic enclaves in the granodiorite.The associated intermediate rocks occur mainly near Bannach, where mostly quartz diorite and quartz monzodiorite are exposed. The dominant rocks are mesocratic, dark-green rocks, with fine to coarse even-grained texture. The Rio Maria Granodiorite and associated intermediate rocks show similar textural and mineralogical aspects. They follow the calc-alkaline series trend in some diagrams. However, they have high-Mg#, Cr, and Ni conjugate with high contents of large ion lithophile elements (LILEs), typical of sanukitoids series. The patterns of rare earth elements of different rocks are similar, with pronounced enrichment in light rare earth elements (LREEs) and strong to moderate fractionation of heavy rare earth elements (HREEs).Field aspects and petrographic and geochemical characteristics denote that the granodiorites and intermediate rocks have sanukitoid affinity. However, geochemical data suggest that the intermediate rocks and the granodiorites are not related by a fractional crystallization process. It is concluded that the intermediate rocks derived from similar sources to the granodiorites, but probably result from a higher degree of melting, being both cogenetic, but not comagmatic rocks.Mineralogical aspects associated with experimental evidence suggest that the Rio Maria Granodiorite magma was relatively water-enriched (>4 wt.%), explaining the presence of hornblende at the liquidus and the absence of clinopyroxene and orthopyroxene in the studied rocks. The occurrence of well-preserved magmatic epidote crystals, admitting that the Rio Maria Granodiorite was emplaced at shallow crustal levels, points to a rapid ascent of the Rio Maria Granodiorite magma. 相似文献
997.
Chilean Patagonia is one of the most extended fjord regions in the world that covers nearly 240,000 km2 with an extremely complex coastline and topography in one of the least densely populated areas of the country (1–8 inhabitants every 10 km2). In recent years, the area has been undergoing somewhat intense pressure since several commercial projects in hydroelectricity, tourism, and commercial salmon and mytilid cultures have been developed, or are in progress. Concomitantly, several large research programs have been devised to study the physical, chemical, and biological environment of Patagonia, such as the CIMAR FIORDO, and recently COPAS Sur-Austral based at Universidad de Concepcion, that attempts to close the bridge between oceanographic knowledge and its use by society.In this introductory article we summarize the collection of papers comprising this Special Issue of Continental Shelf Research. These papers deal with aspects of regional oceanography and geology, inorganic and organic geochemistry, ecology of pelagic and benthic organisms, and past changes in productivity. 相似文献
998.
Paula Garcia Carvalho do Amaral Paulo César Fonseca Giannini Florence Sylvestre Luiz Carlos Ruiz Pessenda 《第四纪科学杂志》2012,27(2):181-191
This paper provides a paleoenvironmental reconstruction of a Late Quaternary lagoon system in the Jaguaruna region of Santa Catarina state, southern Brazil. Integrated results of bulk sedimentary organic matter characterization (δ13C, δ15N and C/N), microfossil (pollen and diatom) and grain‐size analysis from three shallow cores (~2.5 m depth) allowed us to propose an evolving paleogeographic scenario in this coastal region for the last ca. 5500 cal a BP. The lagoonal system in this area was more extensive during the mid‐Holocene than today, with a gradual and continuous lagoon–sea disconnection until the present. We add to the debate regarding relative sea‐level (RSL) variations for the Brazilian coast during the Holocene and discuss the importance of sedimentary dynamics for interpreting changes in coastal ecosystems. The multi‐proxy analysis suggests that changes in coastal ecosystems could be directly related to local sedimentary processes, which are not necessarily linked to RSL fluctuations and/or to climatic variations. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
999.
Luis O. Pimentel 《Astrophysics and Space Science》1987,132(2):387-391
Exact cosmological solutions in the scalar-tetradic theory A are obtained by the assumption of a power relation between the scalar field and the expansion factor of the Universe. Among them there is an inflationary solution. 相似文献
1000.
Adi Nusser Luiz N. da Costa Enzo Branchini Mariangela Bernardi M.V. Alonso Gary Wegner C. N. A. Willmer P. S. Pellegrini 《Monthly notices of the Royal Astronomical Society》2001,320(3):L21-L24
We present a comparison between the peculiar velocity field measured from the ENEAR all-sky D n – σ catalogue and that derived from the galaxy distribution of the IRAS Point Source Catalog Redshift Survey (PSC z ). The analysis is based on a modal expansion of these data in redshift space by means of spherical harmonics and Bessel functions. The effective smoothing scale of the expansion is almost linear with redshift reaching 1500 km s−1 at 3000 km s−1 . The general flow patterns in the filtered ENEAR and PSC z velocity fields agree well within 6000 km s−1 , assuming a linear biasing relation between the mass and the PSC z galaxies. The comparison allows us to determine the parameter where Ω is the cosmological density parameter and b is the linear biasing factor. A likelihood analysis of the ENEAR and PSC z modes yields in good agreement with values obtained from Tully–Fisher surveys. 相似文献