963 resultados para Parana continental flood basalts
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The integration of outcrop and subsurface information, including micropaleontological data, facies and sequence stratigraphic studies, and oxygen isotope analysis, allow us to present a new stratigraphic model for the Cretaceous continental deposits of the Bauru Group, Brazil. Thirty-eight fossil taxa were recovered from these deposits, including 29 species of ostracodes and 9 species of charophytes. Seven of these ostracode species and three subspecies are new and formally described here. The associations of Chara barbosai - Ilyocypris cf. riograndensis, found in the Adamantina Formation, and Amblyochara sp. - Neuquenocypris minor mineira nov. subsp., found in the Marília Formation. Ponte Alta Member, represent two distinct groups that are respectively Turonian-Santonian and Maastrichtian (probably Late Maastrichtian) in age. Therefore, a hiatus, encompassing more than 11 Ma, separates those two formations. From bottom to top, four depositional cycles were recognized in the Bauru Group in western São Paulo: cycles 1 and 2 belong to Caiuá Formation (fluvio-lacustrine and lacustrine deposits in the Presidente Prudente region), cycle 3 to the Santo Anastácio and lower Adamantina Formation (respectively fluvial and lacustrine deposits), and cycle 4 to the upper Adamantina Formation (fluvio-lacustrine facies). An erosional unconformity separates the Caiuá and Santo Anastácio Formations (between cycles 2 and 3). The Marília Formation is a distinct unit from the underlying succession; it does not occur in western São Paulo, but is found in restricted areas of São Paulo, Minas Gerais, Mato Grosso do Sul and Goiás States. During the deposition of the Bauru Group (Aptian? to Maastrichtian) the climate was hot and arid-semiarid. Shallow lakes underwent fluctuations in expansion (wet phases) and contraction (dry phases), as well as variations in salinity. During the deposition of the Adamantina Formation (Turonian-Santonian) there were long, dry periods that caused segmentation of large lakes (due to topographic irregularities in the basaltic substrate) and sometimes exposures of the lake floors; when flooded these lake floors were colonized by extensive meadows of single species of charophytes. Small ephemeral ponds, that were hydrochemically unstable and colonized by multiple species of charophytes, were the depositional sites for the marls and mudstones of Ponte Alta Member (Maastrichtian, Late Maastrichtian?). Our micropaleontological age control, combined with the Late Cretaceous ages of volcanic ashes found in the southeastern Brazil coastal basins, and the stratigraphic position of analcimites from the Jaboticabal-SP region, suggest a Late Coniacian-Santonian age for important magmatic events occurred in the interior of Brazil (north-central São Paulo State, Triângulo Mineiro, and southwestern Goiás State).
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Recent field investigations and geochronological studies of Neoproterozoic rocks in the northwestern part of the Borborema Province, Ceará State, NE Brazil provide important clues pertaining to the nature of convergence between the Borborema Province and the West African-São Luis craton during the assembly of West Gondwana. U-Pb zircon data indicate that the earliest evidence of convergent magmatism along the northwest margin of the Borborema Province occurred around 777 Ma, and was followed by the development of a large continental arc batholith (Santa Quitéria batholith) between ca. 665 and 591 Ma within the central part of Ceará State. These findings, along with supporting geophysical data, suggest that convergence between the Borborema Province and the West African-São Luis craton involved closure of an oceanic realm with subduction polarity to the southeast beneath the northwestern part of the province. Consequently, it seems likely that the Pharusian Ocean was continuous from the Hoggar Province in West Africa into South America during the late Neoproterozoic and additional data suggests that it may have even been connected with the Goianides Ocean of the Brasília Belt farther to the southwest.
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The extension of the Pangaea started in the Upper Triassic and evolved to uplifts, magmatism and development a triple junction during the Mesozoic, and opening the Central Atlantic Ocean. The Brazilian Equatorial Atlantic margin was formed in three Mesozoic extensional events. The first event is recorded by the Calçoene Graben of the Foz do Amazonas Basin. The second event started in the Valangian and is recognized by the enlargement of the Foz do Amazonas Basin, formation of the Marajó and Grajaú basins, and the Gurupi Graben System. The third event commenced in the Albian related to northwestward progression of the rift system, which enlarged the Foz do Amazonas and formed the Potiguar, Ceará, Barreirinhas and Pará-Maranhão basins. At the end of the Lower Cretaceous the movements attenuated in the Marajó Basin and Gurupi Graben System; the extension concentrated in the Foz do Amazonas, Pará-Maranhão and Barreirinhas basins, and evolved to continental rupture of northern South America and western Africa opening of the Equatorial Atlantic Ocean.
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The basalts of the Formação Serra Geral in Parana Basin in the Mato Grosso do Sul and Mato Grosso states cover an area of 180,000 km2. They rest on the Botucatu sandstones and they are recovered by the sedimentary rocks of Bauru and Caiuá Groups. The mineralogical composition of these rocks are plagioclase (40%-55%), clinopyroxenes (19%-40%; augite and pigeonite), opaque minerals (2%-10%; magnetite and ilmenite) and olivine (1.5%). Geochemical data show two different types of basalts, named ATi-Pitanga (2.6% < TiO2 < 4.2%; 396 ppm < Sr < 438 ppm) and BTi-Ribeira (1.7% TiO2 <2.4%, 246 ppm < Sr < 286 ppm). In general, ATi-Pitanga have gently higher La/Yb(n) (6,1 ± 1,5ppm) than those BTi-Ribeira (5.6 ± 1,7ppm). The geochemical differences between ATi-Pitanga and BTi-Ribeira probably are related to different degrees of partial melt of a same mantle source, or to different mantle sources. The field relations show that BTi-Ribeira is displaced towards the north-western margin of the Paraná Basin and the thickness of lava flows increases towards the Paraná Graben, suggesting that ATi-Pitaga overlies BTi-Ribeira.
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In the present study were observed changes in morphology of the bed of the lower course of the river Ivaí, made by bathymetric surveys, granulometric analysis and measures the flow velocity. Changes made considerable changes in relation to flow and bad load. The study was conducted in the last 110 km of the river Ivaí, between the municipalities Tapira and Icaraíma - PR. In this section the channel flows with meandering pattern, embedded in sandstone Caiuá and sediment modern of its flood plain. This is the only major river in the state that so far has no modifications, making it an important site for studies of fluvial geomorphology.
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Forecast of biological consequences of climate changes depend on both long-term observations and the establishment of carbon budgets within pelagic ecosystems, including the assessment of biomasses and activities of all players in the global carbon cycle. Approximately 25% of oceanic primary happen over continental shelves, so these are important sites for studies of global carbon dynamics. The Brazilian Continental Shelf (BCS) has sparse and non-systematic in situ information on phytoplankton biomass, making products derived from ocean color remote sensing extremely valuable. This work analyzes chlorophyll concentration (Chl) estimated from four ocean color sensors (CZCS, OCTS, SeaWiFS and MODIS) over the BCS, to compare Chl and annual cycles meridionally. Also, useful complementary ocean color variables are presented. Chl gradients increased from the central region towards north and south, limited by estuarine plumes of Amazon and La Plata rivers, and clear annual Chl cycles appear in most areas. In southern and central areas, annual cycles show strong seasonal variability while interannual and long-term variability are equally important in the remaining areas. This is the first comparative evaluation of the Chl over the BCS and will aid the understanding of its long-term variability; essential initial step for discussions of climate changes.
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After nearly 80 years since the construction of its core, represented today by the city's central area, Londrina, located in the state of Parana, has the appearance of a new city but its features and trends of planning policies depict the bad examples of Brazilian cities. With a booming urban growth, from north to south of the county, the urban interstices represented by big voids in the middle of the city created speculation and the concept of an ideal city slowly disappeared. With a metropolitan appearance and, at the same time, with small town aspects, Londrina stands out as an automobile-oriented city, a fact that has impacted the livelihood of the population, generating environmental impacts for all social classes. This paper discusses how the form of occupation in Londrina, characterized by the sprawl phenomenon and its relation to car preference as a mode of transportation has generated urban environmental impacts. It was concluded that the choice of using cars in Londrina, as well in other medium-sized Brazilian cities studied by the comparative method, has increased and has generated bottlenecks in traffic. As a consequence, there is a constant expropriation of properties for widening roads and at the same time, the presence of various densities and urban voids that form an uneven urban space and an obstacle to efficient urban planning. © 2012 WIT Press.
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This investigation aimed to study the relative growth, morphological sexual maturity and fecundity of the swimming crab Achelous spinicarpus in a tropical region, on the south-eastern continental shelf of Brazil (25°S). Biometry of all specimens was conducted, including measurements of the cephalothorax, cheliped, abdomen and gonopods. Relative growth was described based on the equation for allometry (y = axb), and size at sexual maturity was determined from inflections in relations involving the cheliped, gonopods (males), and abdomen (females), as dependent variables, related to the cephalothorax width (independent variable). Fecundity was estimated by the gravimetric method. The relations of the length of the chelar propodus and carpal spine to the carapace width without the lateral spines (CW) showed positive allometry in both sexes, with a significant variation in the constant 'b' for males between the developmental stages (juvenile and adult) and the size at maturity estimated at 37 mm CW. In females, the abdomen was most appropriate for the estimate of morphological maturity, which occurred at a smaller size (32 mm CW), with a change in the growth pattern between the stages, passing from isometric (juveniles) to positive allometric (adults). The gonopods also showed different growth rates between developmental stages, in synchrony with the variables of the cheliped. Mean fecundity for the species was 53,984 eggs, with a positive correlation between the number of eggs exteriorized and the size of the female; the equations allowed interconversion between these variables, due to the adjustment of the power function (r2 ≥ 86%). © 2012 Marine Biological Association of the United Kingdom.
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Nezumia aequalis and Coelorinchus mediterraneus are abundant species on the upper and lower continental slopes, respectively, in the Mediterranean Sea. A study on the reproductive strategy of the two species was conducted on the Catalan margin (NW Mediterranean). The reproductive cycle of both species was investigated using visual analyses of gonads and histological screening. The shallower species, N. aequalis, showed continuous reproduction with a peak of spawning females in winter months. In contrast, the deeper-living species, C. mediterraneus, showed semi-continuous reproduction with a regression period during the spring. Juveniles of N. aequalis were present in all seasons, but most abundant in the spring. Only two juveniles of C. mediterraneus were found. Both species had asynchronous oocyte development. The average fecundity of N. aequalis was 10,630 oocytes per individual, lower than known for the same species in the Atlantic Ocean. The fecundity of C. mediterraneus was measured for the first time in this study, with an average of 7693 oocytes per individual. Males of both species appear to have semi-cystic spermatogenesis. © 2013 Elsevier Ltd.
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The area between São Paulo and Porto Alegre in southeastern Brazil plays a key area to understand and quantify the evolution of the South Atlantic passive continental margin (SAPCM) in Brazil. In this contribution, we present new thermochronological data attained by fission-track and (U-Th-Sm)/He analysis on apatites and zircons from metamorphic, sedimentary and intrusive rocks. The zircon fission-track ages range between 108.4 (15.0) and 539.9 (68.4). Ma, the zircon (U-Th-Sm)/He ages between 72.9 (5.8) and 525.1(2.4). Ma, whereas the apatite fission-track ages range between 40.0 (5.3) and 134.7 (8.0). Ma, and the apatite (U-Th-Sm)/He ages between 32.1 (1.5) and 93.0 (2.5). Ma. The spatial distribution of these ages shows three distinct blocks with a different evolution cut by old fracture zones. While the central block exhibits an old stable block, the Northern and especially the Southern block underwent complex post-rift exhumation. The sample of the Northern block shows two distinct cooling phases in the Upper Cretaceous and the Paleogene to Neogene. After sedimentation of the Permian sandstones the samples of the Central block were never heated up over 100. °C with a following moderate to fast cooling phase in Cretaceous to Eocene time and a fast cooling between Oligocene to Miocene. The five thermal models obtained in the Southern block indicate a complex evolution with three cooling phases. The exhumation events of the three blocks correspond with the Paraná-Etendekka event, the alkaline intrusions due to the Trinidad hotspot, and the evolution of the continental rift basins in SE Brazil and are, therefore, most likely to be the major force for the post-rift evolution of the passive continental margin in SE Brazil, which therefore corresponds to the three main phases of the Andean orogeny. © 2013 Elsevier B.V.
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In fluvial systems, the relationship between a dominant variable (e.g. flood pulse) and its dependent ones (e.g. riparian vegetation) is called connectivity. This paper analyzes the connectivity elements and processes controlling riparian vegetation for a reach of the upper Paraná River (Brazil) and estimates the future changes in channel-vegetation relationship as a consequence of the managing of a large dam. The studied reach is situated 30km downstream from the Porto Primavera Dam (construction finished in 1999). Through aerial photography (1:25,000, 1996), RGB-CBERS satellite imagery and a previous field botany survey it was possible to elaborate a map with the five major morpho-vegetation units: 1) Tree-dominated natural levee, 2) Shrubby upper floodplain, 3) Shrub-herbaceous mid floodplain, 4) Grass-herbaceous lower floodplain and 5) Shrub-herbaceous flood runoff channel units. By use of a detailed topographic survey and statistical tools each morpho-vegetation type was analyzed according to its connectivity parameters (frequency, recurrence, permanence, seasonality, potamophase, limnophase and FCQ index) in the pre- and post-dam closure periods of the historical series. Data showed that most of the morpho-vegetation units were predicted to present changes in connectivity parameters values after dam closing and the new regime could affect, in different intensity, the river ecology and particularly the riparian vegetation. The methods used in this study can be useful for dam impact studies in other South American tropical rivers. © 2012 Elsevier Ltd.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Pós-graduação em Educação - FFC
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Preface This study was prepared for the Government of Jamaica following the significant physical damage and economic losses that the country sustained as a result of flood rains associated with the development of Hurricane Michelle. The Planning Institute of Jamaica (PIOJ) submitted a request for assistance in undertaking a social, environmental and economic impact assessment to the Economic Commission for Latin America and the Caribbean (ECLAC) on 14 November 2001. ECLAC responded with haste and modified its work plan to accommodate the request. A request for training in the use of the ECLAC Methodology to be delivered to personnel in Jamaica was deferred until the first quarter of 2002, as it was impossible to mount such an initiative at such short notice. This appraisal considers the consequences of the three instances of heavy rainfall that brought on the severe flooding and loss of property and livelihoods. The study was prepared by three members of the ECLAC Natural Disaster Damage Assessment Team over a period of one week in order to comply with the request that it be presented to the Prime Minister on 3 December 2001. The team has endeavoured to complete a workload that would take two weeks with a team of 15 members working assiduously with data already prepared in preliminary form by the national emergency stakeholders. There is need for training in disaster assessment as evidenced by the data collected by the Jamaican officials engaged in the exercise. Their efforts in the future will be more focused and productive after they have received training in the use of the ECLAC Methodology. This study undertakes a sectoral analysis leading to an overall assessment of the damage. It appraises the macroeconomic and social effects and proposes some guidelines for action including mitigating actions subsequent to the devastation caused by the weather system. The team is grateful for the efforts of the Office of Disaster Preparedness and Emergency Management (ODPEM), the associated government ministries and agencies, the Statistical Institute of Jamaica (STATIN), the Planning Institute of Jamaica and the Inter American Development Bank (IDB) for assistance rendered to the team. Indeed, it is the recommendation of the team that STATIN is poised to play a pivotal role in any disaster damage assessment and should be taken on board in that regard. The direct and indirect damages have been assessed in accordance with the methodology developed by ECLAC (1). The results presented are based on the mission's estimates. The study incorporates the information made available to the team and evidence collected in interviews and visits to affected locations. It is estimated that the magnitude of the losses exceeds the country's capacity to address reparations and mitigation without serious dislocation of its development trajectory. The government may wish to approach the international community for assistance in this regard. This appraisal is therefore designed to provide the government and the international community with guidelines for setting national and regional priorities in rehabilitation and reconstruction or resettlement programmes. A purely economic conception of the problem would be limited. A more integrated approach would have a human face and consider the alleviation of human suffering in the affected areas while attending to the economic and fiscal fallout of the disaster. Questions of improved physical planning, watershed management, early warning, emergency response and structural preparedness for evacuation and sheltering the vulnerable population are seen as important considerations for the post disaster phase. Special attention and priority should be placed on including sustainability and increased governance criteria in making social and productive investments, and on allocating resources to the reinforcing and retrofitting of vulnerable infrastructure, basic lifelines and services as part of the reconstruction and rehabilitation strategy. The Jamaican society and government face the opportunity of undertaking action with the benefit of revised paradigms, embarking on institutional, legal and structural reforms to reduce economic, social and environmental vulnerability. The history of flood devastation in the very areas of Portland and St. Mary shows a recurrence of flooding. Accounts of flooding from the earliest recorded accounts pertaining to 1837 are available. Recurrences in 1937, 1940, 1943 and 2001 indicate an ever-present probability of recurrence of similar events. The Government may wish to consider the probable consequences of a part of its population living in flood plains and address its position vis-à¶is land use and the probability of yet another recurrence of flood rains. (1) ECLAC/IDNDR, Manual for estimating the Socio-Economic Effects of Natural Disasters, May,1999.