Revista do Instituto Geológico
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Considerações sobre a representação cartográfica de riscos geológicos
Get PDFGeological hazard maps can be viewed as a particular type of engineering geological map which presents some specific concerns. This paper discusses some aspects related to the scale, the major elements to be represented and the methods and techniques commonly used for the representation of geological hazard maps. This theme is analysed on the basis of some examples of national and international geological hazard maps.Cartas de risco geológico, entendidas como um tipo particular de carta geotécnica, apresentam algumas especificidades. Com base em dados bibliográficos e na análise de exemplos nacionais e internacionais, o presente artigo discute os aspectos referentes às escalas das cartas de risco geológico, os principais elementos cartografados e as técnicas usuais empregadas, além das questões inerentes à durabilidade e ao custo de impressão. Também são apresentadas opiniões quanto à utilização de técnicas computacionais
Vibrotestemunhador leve: construção, utilização e potencialidades
Get PDFUndisturbed or minimally disturbed cores are very hardly obtainable from soft sedimentary deposits, mostly of Quatemary age. On the other hand, details of primary structures must be preserved making possible to reconstruct, as perfect as possible, their sedimentary environments. A very light and cheap vibracorer, suitably used for coring clayey-sandy organic sediments, like bay-bottom, lacustrine or lagoonal deposits, is here described.É bastante difícil obter testemunhos não-perturbados ou com mínima perturbação de depósitos sedimentares moles, principalmente de idade quatemária. Por outro lado, detalhes de estruturas primárias devem ser preservados tornando factível reconstruir, tão perfeitos quanto possível, seus ambientes de sedimentação. Um vibrotestemunhador muito leve e barato, adequadamente usado para sedimentos argilo-arenosos e orgânicos, como depósitos de fundo de baía, lacustres ou lagunares, é aqui descrito
Proposta de metodologia de definição de carta geotécnica básica em regiões tropicais e subtropicais
Get PDFThis paper presents the methodology for the definition of geotechnical maps that is being used in Southern Brazil. The unit is defined considering the superposition of pedology and geology. ln urban regions, a simplified pedological study is performed with geotechnical applications in mind. Once geotechnical units are defined, together with soils layers, field work is performed, involving morphological analysis and soil sampling for laboratory testing.Simple soil tests are performed in the laboratory, appropriate to the required applications. A description of possible typical soil profiles is included in the geotechnical map. ln this way, urban planners, or other professionals, can estimate the type of material to be founded in the geotechnical unit. A knowledge of physical environment, geomechanical and hydraulic behavior, helps the analysis of applications where the soil is loaded by foundations, landslides, borrow pits for pavements, low cost housing, and small dams. This methodology helps to estimate soil layers susceptible to erosion, as well as layers with drainagecharacteristics adequate for landfills.O trabalho apresenta a metodologia de definição de carta geotécnica básica que está sendo usada no Sul do Brasil. A unidade geotécnica é estimada considerando a superposição da pedologia e a geologia. Em zonas urbanas, é feito um estudo pedológico simplificado voltado para a geotecnia. Estimadas as unidades e os horizontes de solos, são realizados trabalhos de campo com vistas a análises morfológicas e retiradas de amostras para ensaios de laboratório. Os ensaios geotécnicos são simples, mas apropriados para as aplicações. Uma descrição dos perfis típicos existentes na unidade e seu comportamento acompanha o mapa geotécnico. Desta maneira, o profissional de planejamento, ou outro usuário, pode ter uma estimativa do tipo de material a ser encontrado na unidade. O conhecimento do meio físico, comportamento geomecânico e hidráulico visam às aplicações onde o solo é solicitado, como nos casos de fundações, escon·egamentos de encostas, jazidas de solos destinados à pavimentação, habitações de baixo custo, pequenos açudes e barragens. Estima também locais ou horizontes suscetíveis à erosão e com drenagens apropriadas para aterros de rejeitos
Carta de erodibilidade da folha de Cosmópolis, São Paulo auxílio ao gerenciamento do meio físico
Get PDFEngineering Geological mapping is an impoltant tool for the planning and managing landn occupation. The susceptibility of the terrain to erosion process is evaluated in engineering geological mapping by means of a Soil Map. This map defines homogeneous land units based on some related aspects (attributes) that influence soil erosion and on the qualitative or quantitative valuation of these attributes. This paper presents the methodology used and the Soil Erosion Map obtained for the Cosmópolis region, northeastern part of the state of São Paulo.A Cartografia Geotécnica constitui-se em importante ferramenta nos projetos sócio-econômicos que visam ao estabelecimento e gerenciamento da ocupação ordenada do meio físico. Como um dos produtos da Cartografia Geotécnica, a Carta de Erodibilidade define diferentes unidades homogéneas dos terrenos com base na avaliação de atributos que condicionam a suscetibilidade à erosão. Os trabalhos de mapeamento foram realizados na escala 1:50.000, na região compreendida pela Folha de Cosmópolis, no nordeste do Estado de São Paulo
Fire history of Patagonia: clima te versus human cause
Get PDFHuman society's concern about future environmental changes in response to both natural forcings, such as climate, and ever increasing human impact can only be addressed if the interaction between the natural and man-made forcings are fully understood. One parameter that lends itself for such analysis is fire. The historical record is toa short and ambiguous to provide data adequate to discriminate between natural and man-induced changes in fire frequencies. Paleoenvironmental records, inclusive of both the historic and the prehistoric past, can provide an appropriate data set with which to address this question. These data include paleoclimate reconstructions, pollen, and charcoal records from dated sediment sections, and information on past human impact derived from historical and archaeological evidence. The Patagonian region is well suited for such a study because of its climatic diversity, its wide range of ecosystems, and the adaptation of its ecosystems to fire. Records from latitudes 36º to 55ºS suggest that although prehistoric human activities may have amplified extent of fires, climate played the central role. Changes in patterns of climate variability were particularly important. Whenever variability was high, during the late glacial and the late Holocene, fires were abundant. Late glacial variability is probably related to fluctuations in the extent of Antarctic sea-ice which in turn influences the latitudinal position of the westerly stormtracks; late Holocene variability, on the other hand, is related to the influence of El Niño/Southern Oscillatio
Editorial
Get PDFThis volume contains three invited contributions to the Congress Paleoclimas e Evolução Quaternária da América do Sul, promoted and executed by the Associação Brasileira de Estudos do Quaternário - ABEQUA, with the support of the Fundação de Amparo à Pesquisa do Estado de São Paulo - FAPESP, Instituto Geológico-SMA and Instituto Oceanográfico - USP, from July 5 to 8, 1993, in São Paulo - Brasil. Irion et al. deal with the sedimentary history of Amazonia. Markgraf and Anderson with fire ecology in Patagonia. Heusser gives a general treatment of the paleoecology of southemmost South America. ABEQUA presents its best thanks to the authors for the readiness and generosity in accepting the invitation and presenting the papers.
Probabilidade de ocorrência de totais pluviais máximos horários, em Campinas - São Paulo
Get PDFThis paper deals with the fit of gamma, Erlang, lognormal and extreme value distributions to empirical frequency distributions of hourly maximum rainfall for summer months, including the normal for an annual sample. As a result are also presented the annual and summer months climatic behaviour for Campinas - state of São Paulo, BrasilNeste trabalho será discutida e avaliada a adequação das distribuições gama, de Erlang, lognormal e de valores extremos, às amostras de totais pluviais máximos horários, dos meses de verão, incluindo-se à normal para urna amostra anual Ainda, como resultante dessa análise, será apresentada urna caracterização do comportamento anual e dos meses de verão, em Campinas, SP, com relação a esse tipo de evento climático
Densidade de drenagem e sua relação com fatores geomorfopedológicos na área do alto rio Pardo, SP e MG
Get PDFDrainage density is one of the main parameters of morphometric analysis in hydrographic basins, corresponding to the average length of channels in the basin per unit of area. The spacial distribution of drainage density values in the upper course of Pardo river area, in the northeast of the state of São Paulo and southern Minas Gerais, was obtained measuring channel lengths in quadratic cells, covering all the area. An important spacial correlation was observed between anomalies of high drainage density and the distribution of main structures reactivated in the Mesozoic - Cenozoic, which suggests an increase of erosive processes controlled by neotectonics. The main anomalies of rarefaction of drainage were observed on sedimentary areas of the Parana Basin. A lower correlation was obtained with the soils, where is observed a general trend to high density drainage anomalous zones in podzolic soils and low to intermediate in latosols. The results indicate that the study of this morphometric parameter represents an important tool for the preliminary definition of areas, which may provide structural and tectonic evidence in field works with more probability of success.A densidade de drenagem é um dos principais parâmetros na análise morfométrica de bacias hidrográficas, correspondendo ao comprimento médio de canais de uma bacia por unidade de área. A distribuição espacial dos valores da densidade de drenagem na região do alto rio Pardo - situada entre a porção nordeste do Estado de São Paulo e sul de Minas Gerais - foi obtida a partir da medição de comprimentos de canais em celas quadráticas que recobriram toda área. Observou-se uma significativa correlação espacial das anomalias de alta densidade de drenagem com a distribuição das principais estruturas reativadas no Mesozóico-Cenozóico, sugerindo uma retomada erosiva das formas de relevo, devido à neotectônica. As principais anomalias de rarefação de drenagem foram observadas nos terrenos sedimentares da Bacia do Paraná. Uma menor correlação foi obtida com os solos, podendo-se observar uma tendência geral de concentração de zonas anômalas de alta densidade de drenagem nos solos podzólicos e baixa a intermediária nos latossolos. Os resultados indicam que o estudo desta variável morfométrica representa uma importante ferramenta na definição preliminar de áreas, nas quais se podem buscar evidências estruturais e tectônicas de campo com maior probabilidade de êxito
Quaternary paleoecology of Fuego-Patagonia
Get PDFThe paleoecology of Quaternary events in Fuego-Patagonia derives from biogenic deposits emplaced before, during, and following the last glacial maximum. Paleoecological data center on the palynology of stratigraphic sections of (1) biogenic beds in a proglacial delta of finite and infinite age at Lago Fagnano, and of (2) selected sites of radiocarbondated, late-glacial and postglacial, mire/lacustrine deposits at Puerto Harberton, Lago Fagnano, and Bahía Inútil in Fuegia and at Punta Arenas and Torres del Paine in Patagonia. Events embrace noteworthy sequences involving vegetation and climate, atmospheric circulation, fire, human presence, land-sea level relations, and volcanism. Data from peaty horizons in the Pleistocene delta at Lago Fagnano, dated at about 40000 and >;58000 yr BP, indicate treeless steppe/tundra under a cold, dry, interstadial climate. Younger deposits, formed following the last glacial maximum dated at >; 16590 in the Estrecho de Magallanes and >;14640 yr BP in Canal Beagle, show climatically variable, late-glacial episodes of woodland - steppe/tundra interaction. In the warmer early Holocene, progressive development of closed forest replacing open woodland and steppe, is a general feature of the vegetation; evident after 5000 yr BP, under a cool-temperate, more humid climate, are the increased presence of closed forest and the spread of mires on the landscape. Apparent from the Holocene vegetation pattern is the greater frequency/intensity of cyclonic storms of the prevailing westerlies crossing Fuego-Patagonia after 5000 yr BP. Charcoal, in addition to fossil pollen in the records, is ascribed to Paleoindian burning, as purposely practiced during hunting to congregate game. On Isla Grande de Tierra del Fuego, where volcanic activity and lightning are not considered to be causal agents of fire, burning attributed to Paleoindian hunters is traceable from late-glacial charcoal remains as earlyas 13280 yr BP. Fires in Fuego-Patagonia, judged from the frequency of charcoal, wete commonplace in the early Holocene and later more occasional, possiby reflecting changes in size and routes of migration in human populations.The paleoecology of Quaternary events in Fuego-Patagonia derives from biogenic deposits emplaced before, during, and following the last glacial maximum. Paleoecological data center on the palynology of stratigraphic sections of (1) biogenic beds in a proglacial delta of finite and infinite age at Lago Fagnano, and of (2) selected sites of radiocarbondated, late-glacial and postglacial, mire/lacustrine deposits at Puerto Harberton, Lago Fagnano, and Bahía Inútil in Fuegia and at Punta Arenas and Torres delPaine in Patagonia. Events embrace noteworthy sequences involving vegetation and climate,atmospheric circulation, fire, human presence, land-sea level relations,.and volcanism. Data from peaty horizons in the Pleistücene delta at Lago Fagnano, dated at about 40000 and>58000 yr BP, indicate treeless steppe/tundra under a cold, dry, interstadial c1imate. Younger deposits, formed following the last glacial maximum dated at > 16590 in the Estrecho de Magallanes and >14640yr BP in Canal Beagle,show c1imaticallyvariable, lateglacial episodes of woodland - steppe/tundra interaction. In the warmer early Holocene, progressive development of c10sedforest replacing open woodland and steppe, is a general feature of the vegetation; evident after 5000 yr BP, under a cool-temperate, more humid c1imate, are the increased presence of c10sedforest and the spread of mires on the landscape. Apparent from the Holocene vegetationpattern is the greater frequency/intensity of cyc10nic storms of the prevailing westerlies crossing Fuego-Patagonia after 5000 yr BP. Charcoal, in addition to fossil pollen in the records, is ascribed to Paleoindian,burning, as purposely practiced during hunting to congregate game. On Isla Grande de Tierra deI Fuego, where volcanic activity and lightning are not considered to be causal agents of fire, burning attributed to Paleoindian'hunters is traceable from late-glacial charcoal remains as earlyas 13280yr BP. Fires in Fuego-Patagonia, judged from the frequency of charcoal, wete commonplace in the early Holocene and later more occasional, possiby reflecting changes in size and routes of migration in human population