923 resultados para Geology -- Victoria -- Bacchus Marsh Region


Relevância:

30.00% 30.00%

Publicador:

Resumo:

The marsh deer is the largest neotropical cervid with morphological and ecological adaptations to wetlands and riparian habitats. Historically, this now endangered species occupied habitats along the major river basins in South America, ranging from southern Amazonia into northern Argentina to the Parana river delta. This particularly close association with wetlands makes marsh deer an excellent species for studying the effects of Pleistocene climatic changes on their demographic and phylogeographic patterns. We examined mitochondrial DNA variation in 127 marsh deer from 4 areas distributed throughout the Rio de]a Plata basin. We found 17 haplotypes in marsh deer from Brazil, Bolivia and Argentina that differed by 1-8 substitutions in a 601 bp fragment of mitochondrial control region sequence, and 486 bp of cytochrome b revealed only 3 variable sites that defined 4 haplotypes. Phylogeny and distribution of control region haplotypes suggest that populations close to the Pantanal area in central Brazil underwent a rapid population expansion and that this occurred approximately 28,000-25,000 years BP. Paleoclimatic data from this period suggests that there was a dramatic increase for precipitation in the medium latitudes in South America and these conditions may have fostered marsh deer's population growth.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Habitat fragmentation and diseases have resulted in a decline of the marsh deer (Blastocerus (dichotomus) throughout its South American range. Our objectives were to determine whether marsh deer intended for translocation from a region of the Rio Parana Basin had been infected previously by foot-and-mouth disease virus (FMDV) and whether they were carrying virus We captured marsh deer from June to October 1998 and collected blood from 108 animals and esophageal-pharyngeal fluid from 53 Serum was tested for antibodies against three FMDV serotypes (O, A, and C) by liquid-phase-blocking sandwich enzyme-linked immunosorbent assay (ELISA) Esophageal-pharyngeal fluid was tested for FMDV RNA by reverse transcription polymerase chain reaction (RT-PCR) and inoculation into three successive baby hamster kidney (BHK-21) cell subcultures, followed by RT-PCR of cultures We detected low log(10) titers (range 1 0-1 5) to FM DV subtype A(24) Cruzeiro in 19 of 108 sampled marsh deer, but failed to isolate FMDV or detect FMDV RNA in any samples we conclude that marsh deer from our study site were unlikely to carry FMDV, however, as a preventive measure, the 19 animals with titers for FMDV were not sent to FMDV-free Brazilian states

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The chromosomic constitution of the Marsh Deer (Blastocerus dichotomus) was studied in 18 males and 18 females, mainly from the Tiete river basin in Sao Paulo State, Brazil. The species diploid number was determined to be 66 chromosomes and the fundamental number (FN), 74. The X and the Y were the largest and the smallest chromosome, respectively. Large amounts of the constitutive heterochromatin marked by the C band were located in the centromeric region of all the acrocentric chromosomes. The first chromosome pair was not marked and the second and third pairs showed weak centromeric markings. The X chromosome showed two strong telomeric markings while the Y was C band negative. Chromosomes four and five were the NOR carriers. Polymorphism for this band was observed in pair four. The results of this study are in agreement with other reports in the literature, in spite of the different origin of the animals.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Structural, geochemical, and isotope studies were carried out on the gold deposits of the Pontes e Lacerda region (Mato Grosso state, Brazil), where rocks of the Aguapei and Rondoniano mobile belts (southwestern Amazonian craton) occur. The orebodies are hosted in metavolcanic, gneiss-granite, quartzite, tonalite, and granite units. Tectonics involve oblique overthrusting (from northeast to southwest), which led to the formation of recumbent folds and thrusts (pathways for the mineralizing fluids), upright folds, and faults with dominant strike-slip component. These unconformities represent potential sites for mineralization. During geological mapping, it was observed that the orebodies consist of quartz, pyrite, and gold, and that the hydrothermal alteration zone contains quartz, sericite, pyrite (altered to limonite), and magnetite (altered to hematite). Chalcopyrite, galena, and sphalerite occur only in the Onça deposit. Chemical analysis of sulfides indicates high contents of Bi, Se, and Te in sulfides and gold, suggesting plutonic involvement in the origin of hydrothermal solutions. K-Ar dating of hydrothermal sericites from gold veins yielded ages in the range from 960 to 840 Ma, which may indicate the age of original crystallization of sericite. Pb-Pb dating in galenas yielded model ages in the range from 1000 to 800 Ma for the Onça deposit, which is in agreement with K-Ar ages. Pb-isotopic ratios indicate high U/Pb and low Th/Pb for the upper-crustal Pb source before incorporation in galena crystals. The Pontes e Lacerda gold deposits yielded ages correlated to the Aguapei event and probably were formed during a Proterozoic contractional tectonic period in the southwestern part of the Amazon craton, which may characterize an important metallogenic epoch in the Pontes e Lacerda region.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Balancing power production and environmental conservation can be problematic. The objective of this study was to investigate the abundance of marsh deer in the Paraná River Basin, above the Sergio Motta (Porto Primavera) Dam, before and after the impact of the dam closure. A fixed-wing, flat window aircraft was used to survey study transects. Observations were recorded based on the distance sampling line transect method, assuming that the detection probability decreases with increased distance. The abundance of marsh deer in the survey region prior to flooding was estimated to be 974 individuals (CV = 0.23). The overall abundance dropped from 974 to 444 (CV = 0.26) individuals after flooding, an overall reduction of 54%. This reduction can be attributed to the direct impact of the flooding process, but it was likely exacerbated by indirect effects, such as increased disease, hunting, and reduction in food availability. Prior to flooding, the marsh deer was distributed widely throughout the dam's catchment area; however, the marsh deer habitat was almost completely destroyed by the flooding process. This situation highlights the need to implement management strategies that ensure the survival of the remaining fragmented population.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Subduction zones are one of the most characteristic features of planet Earth. Convergent plate junctions exert enormous influence on the formation and recycling of continental crust, and they are also responsible for major mineral resources and earthquakes, which are of crucial importance for society. A subduction-related geologic unit containing high-pressure rocks occurs in the Barragan area (Valle del Cauca Department) on the western flank of the Central Cordillera of the Colombian Andes. Blueschists and amphibolites, serpentinized meta-ultramafic rocks, graphite-chlorite-muscovite-quartz schists, protocataclasites, and graphite-chlorite-andalusite-andesine-garnet-muscovite +/- titanite schists are exposed in this region. In spite of the petrotectonic importance of blueschists, the high-pressure metamorphism of the Central Cordillera of Colombia has been rarely studied. New geochemical data indicate that protoliths of the blueschist- and amphibolite-facies rocks possessed normal mid-ocean ridge basalt bulk compositions. Ar-40/Ar-39 geochronology for a metapelite rock associated with the blueschists shows a plateau age of similar to 120 million years. We suggest that high-P/T conditions were present from similar to 150 to 125 Ma, depending on the model of generation and exhumation considered.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

It is lively debated how eclogites find their way from deep to mid-crustal levels during exhumation. Different exhumation models for high-pressure and ultrahigh-pressure rocks were suggested in previous studies, based mainly on field observations and less on microstructural studies on the exhumed rocks. The development and improvement of electron microscopy techniques allows it, to focus interest on direct investigations of microstructures and crystallographic properties in eclogites. In this case, it is of importance to study the applicability of crystallographic measurements on eclogites for exhumation processes and to unravel which processes affect eclogite textures. Previous studies suggested a strong relationship between deformation and lattice preferred orientation (LPO) in omphacite but it is still unclear if the deformation is related to the exhumation of eclogites. This study is focused on the questions which processes affect omphacite LPO and if textural investigations of omphacite are applicable for studying eclogite exhumation. Therefore, eclogites from two examples in the Alps and in the Caledonides were collected systematically and investigated with respect to omphacite LPO by using the electron backscattered diffraction (EBSD) technique. Omphacite textures of the Tauern Window (Austria) and the Western Gneiss Region (Norway) were studied to compare lattice preferred orientation with field observations and suggested exhumation models from previous studies. The interpretation of omphacite textures, regarding the deformation regime is mainly based on numerical simulations in previous studies. Omphacite LPO patterns of the Eclogite Zone are clearly independent from any kind of exhumation process. The textures were generated during omphacite growth on the prograde path of eclogite development until metamorphic peak conditions. Field observations in the Eclogite Zone show that kinematics in garnet mica schist, surrounding the eclogites, strongly indicate an extrusion wedge geometry. Stretching lineations show top-N thrusting at the base and a top-S normal faulting with a sinistral shear component at the top of the Eclogite Zone. The different shear sense on both sides of the unit does not affect the omphacite textures in any way. The omphacite lattice preferred orientation patterns of the Western Gneiss Region can not be connected with any exhumation model. The textures were probably generated during the metamorphic peak and reflect the change from subduction to exhumation. Eclogite Zone and Western Gneiss Region differ significantly in size and especially in metamorphic conditions. While the Eclogite Zone is characterized by constant P-T conditions (600-650°C, 20-25 kbar), the Western Gneiss Region contains a wide P-T range from high- to ultrahigh pressure conditions (400-800°C, 20-35 kbar). In contrast to this, the omphacite textures of both units are very similar. This means that omphacite LPO is independent from P-T conditions and therefore from burial depth. Further, in both units, omphacite LPO is independent from grain and subgrain size as well as from any shape preferred orientation (SPO) on grain and subgrain scale. Overall, omphacite lattice preferred orientation are generated on the prograde part of omphacite development. Therefore, textural investigations on omphacite LPO are not applicable to study eclogite exhumation.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The island of Cyprus was a major producer of copper and stood at the heart of east Mediterranean trade networks during the Late Bronze Age. It may also have been the source of the Red Lustrous Wheelmade Ware that has been found in mortuary contexts in Egypt and the Levant, and in Hittite temple assemblages in Anatolia. Neutron Activation Analysis (NAA) has enabled the source area of this special ceramic to be located in a geologically highly localised and geochemically distinctive area of western Cyprus. This discovery offers a new perspective on the spatial organisation of Cypriot economies in the production and exchange of elite goods around the eastern Mediterranean at this time.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Lastarria volcano (Chile) is located at the North-West margin of the `Lazufre' ground inflation signal (37x45 km²), constantly uplifting at a rate of ~2.5 cm/year since 1996 (Pritchard and Simons 2002; Froger et al. 2007). The Lastarria volcano has the double interest to be superimposed on a second, smaller-scale inflation signal and to be the only degassing area of the Lazufre signal. In this project, we compared daily SO2 burdens recorded by AURA's OMI mission for 2005-2010 with Ground Surface Displacements (GSD) calculated from the Advanced Synthetic Aperture Radar (ASAR) images for 2003-2010. We found a constant maximum displacement rate of 2.44 cm/year for the period 2003-2007 and 0.80- 0.95 cm/year for the period 2007-2010. Total SO2 emitted is 67.0 kT for the period 2005-2010, but detection of weak SO2 degassing signals in the Andes remains challenging owing to increased noise in the South Atlantic radiation Anomaly region.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

This paper is a report of a geological survey made of an area of approximately fifty square miles lying Northeast of Whitehall, Montana, in the region of the Golden Sun­light Mine. The survey was made by a field party consisting of twenty-three members of the senior class of the Montana School of Mines.