849 resultados para Geomorphological subdivision


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The city of Cubatão is a densely populated area with high industrial activity. In the area there are also important linear works as roads, railways, pipelines, aqueducts and lines of transmission of energy. The geological and geomorphological features of the municipality, combined with the human activities, make the site an area heavily prone to the landslides, so a region at high risk. In this work, landslide scars were extracted in aerial photos from 1985 and 1994, years that recorded a high incidence of landslides. Quantitative analysis of the relationship between the occurrence of scars and the forms of tracks were conducted, based on an intensive survey of scars in the region, represented by 2595 extracted scars, with the aim of contributing to a better understanding of the slipping processes in the Serra do Mar paulista and thus to the reduction of risks in the region. Achievements have concluded that the greatest percentage of slides in the region is linked to the strands straitght, followed by convex, which confirms previous studies conducted in the region, in a qualitative way or with a much lower number of scars.

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The coast environments were the first areas the man occupied in Brazil and they present, nowadays, high urbanization indexes. So, it's very important to analyze the environmental quality of those areas. The geomorphologic aspects are valuable for that analysis because they constitute the physical substrate on which such ant anthropic activities are developed. The cartography of geomorphologic features is essential to supply subsidies for the handling of coastal areas. However, the question about what proceedings are adequate to the geomorphologic cartography of recent sedimentation coastal lands is still in discussion by many authors. This article aims to compare two different technical proposals for mapping São Paulo's south coast, a sector that shows a great depositional complexity. The features related to recent sedimentation sectors were mapped because it's considered that they are necessary to understand the morphodynamic and, at the same time, they demonstrate difficulties in geomorphologic cartography standardization. Through the analysis of the produced maps it's possible to notice that the two proposals have positive aspects, but both need adaptations to cartographically demonstrate the geomorphologic complexity of São Paulo's south coast.

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A few examples of supergene ore formation and their interaction with morphogenesis (palaeosurfaces) and weathering mineralogy are discussed. Geomorphological and mineralogical records to characterize palaeosurfaces associate the weathering of primary minerals and their relationship with concentrations of cooper and iron ore deposits in southeastern state of São Paulo, Brazil. We have distinguished two palaeosurfaces generated by several weathering phases and controlled by the geological framework. The first and oldest upper palaeosurfaces (900 - 1000 m a.s.l.), situated in Riberão Branco (Alto do Brancal), were developed on silico-limestones. It is formed by typical iron laterites enriched by secondary products of cooper. The second and younger level palaeosurfaces located in Itapeva (Santa Blandina and Bairro do Sambra). This palaeosurface is formed by copper percolating through the weathered rock (saprolite). Other features can be observed like neo-formed products in laterites. They are classified into two types: clay like silico- cupriferous products (with noticeable amounts of iron) and copper minerals (crysocolla, in their flat slopes). These features allowed the presence of copper ores and their morphogenesis control will help in the exploration and prospecting of supergene ore mineral.

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This paper presents the results of the frst systematic mapping of the paleochannel network on the Taquari megafan (Pantanal, Brazil). We used remote sensing data collected by the ASTER sensor, which captures images with 15 m square pixels. A total of 34 scenes, acquired from 2001-2006, were used in the analysis. These data were processed using a decorrelation stretch technique in order to obtain a better visual identifcation of the paleochannels. The mapping procedure began with the overlay of a 1:50.000 IBGE articulation, in order to systematize the extraction of features and to reduce the subjectivity inherent to visual analysis methods. We mapped a total of 33,205 km of paleochannels. The density of these features is related to the relative ages of distinct geomorphological compartments, known as depositional lobes. The mapped features preserve avulsion events that occurred on the megafan. The results suggest that low-magnitude avulsions occur more frequently than larger events.

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The Nabileque fluvial fan is a Quaternary depositional system located along the southwestern border of the Pantanal, covering an area of approximately 9,100 km 2. It is a peculiar alluvial system because it is not associated with inflow from adjacent plateaus. The Nabileque megafan is formed by the Paraguay River at the exit of the Pantanal wetland, coalescing with the Pilcomayo megafan of the Chaco basin. A geomorphological zonation analysis was performed making use of remote sensing data with field verification. Most of the area is a vast alluvial plain made of Pleistocene deposits, whose surface is marked by the presence of an intricate network of distributary paleochannels. Areas blanketed by Pleistocene deposits are dissected by erosional streams and subject to frequent flooding events. The Paraguay River flows in a meander belt constrained by NE fractures associated with the Transbrasiliano Lineament, but deflects towards the SSE after the Negro River confluence composing the system's peripheral drainage. An abandoned meander belt is preserved within a remarkable N-S incised-valley that is interpreted as the ancient Paraguay River course. Processes of avulsion and river capture are suggested to explain the observed changes of the river course. The Nabileque River is an underfit stream within the incised-valley, cutting paleomeanders and point bars of the previous Paraguay River course.

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This study aimed at analyzing the geomorphologic dynamics and its relationship to human interference and ownership of relief, towards a systemic approach, through the interpretation, in an integrated manner, of cartographic documents made from techniques of geomorphologic cartography and of land use. By stereoscopic pairs of aerial photographs, it was prepared the Geomorphological Map and the Land Use Map, respectively based on Tricart's (1965) and Ceron and Diniz's (1966) technical procedures. The unit of the research analysis refers to the basin of Tijuco Preto Streamlet (SP) which is located at the Geomorphological Province of São Paulo state Peripheral Depression between latitudes 22°42'17 and 22°51'36 S, and longitudes 47°30'30 and 47°37'03. In general, it was possible to notice that this basin has been experiencing linear erosion processes, where it was mapped many erosion furrows, grooving and creeping, besides several slope breaks. These processes are associated with a conjunction of circumstances, and the anthropic one is mostly represented by sugarcane monoculture and by urbanization, which are crucial agents in activating erosion processes and in direct interfering on the dynamics of river and rain flow at the basin of Tijuco Preto Streamlet.

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This study intends to evaluate the effects of landscape physical elements (rocks and relief) associated with silviculture activities. The study was carried out on a small farm (Fazenda Santa Edwirges) covered by Eucalyptus forested situated in the Paraiba do Sul Basin, Southeast Brazil. The methodology consisted of detailed geological and geomorphological studies at 1:10,000 scale, and laboratory analysis of soil physical properties. The results showed three geologic-geomorphologic associations (ridge escarpment with granitic rocks, steep and gentle hills cut by shear zones and gentle hill with alluvial sediments) present high vulnerability for the development of the physical processes such as accelerated erosion landslides and flooding. In contrast, mountains associated with gneissic rocks present smaller vulnerability and high resilience for the development of the physical processes. The results have showed the importance of considering the interactions among landscape physical for the eucalyptus forest management contributing to a better selection area for eucalyptus cultivation and minimize adverse environment impact in road design.

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Agricultural and mining activities are directly related to changes in natural landscapes. From the perspective of anthropogenic geomorphology supported by general systems theory, this research has developed, in order to identify and analyze changes in the land use, mainly from agriculture and the exploitation of clay, and its implications in the hydro-geomorphological characteristics in the Santa Gertrudes Stream watershed (SP). This area is within the context of the Ceramic Pole Santa Gertrudes (SP), which besides its importance as a supplier of raw material, is characterized as the largest center of international reference in ceramic tiles on the American continent. For this purpose, we made land use and geomorphology maps of two scenarios, corresponding to the years 1962 and 2006, which allowed the identification of changes caused by human activities on the landforms of the area, such as the increase in area of parcels intended for mining activity, which went from 3.1% to occupy 19% of the catchment area of the respective period and that, among other changes, gave rise to new forms of relief as, for example, in levels of pit mining abrupt and smooth. The results indicate that the main features of representative of human changes in relief are represented for opening of large clay mining pits and agricultural activities, which intensified the denudation and sedimentation processes in the Santa Gertrudes Stream watershed.

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The Pantanal wetland is an extensive depositional tract characterized by the presence of fluvial megafans, from which that of the Taquari River is the most extensive and well known. Located on the northern border of the Pantanal, the São Lourenço megafan is a large distributary fluvial system with an area of 16,000 km2, but poorly known regarding its geomorphological and geological features. The Sao Lourenço and the Taquari are coalescent megafans, having the Piquiri interfan meander river in between them. Based on the interpretation of satellite images and field validation, it was possible to identify channel patterns, to interpret depositional and erosional processes, to recognize the phenomena of river avulsion and to map depositional lobes. Three geomorphological zones were recognized on the São Lourenço megafan: 1) abandoned depositional lobes located in the upper/intermediate fan, composed of Pleistocene fluvial deposits and exhibiting distributary paleochannels on their surfaces, which are currently being dissected by tributary channels; 2) an active Holocene confined meander belt formed by fluvial aggradation in a N65E incised-valley; 3) active depositional lobes placed on the distal part of the system, which are the main site of sedimentation and are characterized by frequent avulsion events, channel bifurcation, distributary drainage pattern and the presence of depositional lobated landforms. The active depositional lobes were formed due to an important event of river avulsion that caused the lower portion of the meander belt to be abandoned.

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Sponge spicules are siliceous microfossils that are especially useful for analysis of sandy fluvio-lacustrine sediments. Sponge spicules in a long sediment core (~550 cm below surface), consisting of fine sand, sandy silt, and organic-rich mud, recovered from the floodplain of the Nabileque River, southern Pantanal, Brazil (S20°16′38. 3″/W57°33′00. 0″), form the basis of a novel paleoenvironmental interpretation for this region. Optically stimulated luminescence dates constrain the timing of deposition to the middle-late Holocene and all spicules identified are typical of the Brazilian cerrado biome. The base of the section is dominated by Oncosclera navicella Carter 1881, Metaniaspinata Carter 1881, and Corvospongilla seckti Bonetto and Ezcurra de Drago 1966, which indicate a lotic to semi-lotic environment strongly influenced by an actively meandering river channel at ~6. 7-5. 7 ka BP. The appearance of Heterorotula fistula Volkmer-Ribeiro and Motta 1995, Dosilia pydanieli Volkmer-Ribeiro 1992 and Radiospongilla amazonensis Volkmer-Ribeiro and Maciel 1983 at ~340 cm downcore suggests a reduction in flowing water and a more stable lentic environment, consistent with deposition in an oxbow lake. This oxbow lake environment existed during an interval of regional aridity between ~4. 5 and 3. 9 ka BP. Spicules, as well as phytoliths and diatoms, are highly variable moving up-section, with species from both lotic and lentic ecosystems present. Above ~193 cm, the total abundance of spicules declines, consistent with wetter climate conditions and development of an underfit river similar to the modern floodplain. Results support hypotheses related to migration of the Paraguay River inferred from geomorphological studies and add a key southern-region dataset to the emerging Holocene database of paleoenvironmental records from the Pantanal wetlands. © 2012 Springer Science+Business Media Dordrecht.

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Neomeris (Lamouroux, 1816) is an extant taxon, the origin of which can be tracked back into Early Cretaceous times. The introduction of a new mid-Cretaceous species from Brazil, i.e., Neomeris srivastavai n. sp., offers the opportunity to review the subdivision of the genus into three subgenera, to complete the catalogue of the fossil calcareous algae of Brazil, and to point out the huge stratigraphic gap and lack of documentation between the first occurrence of the dasycladacean model of reproduction, i.e., choristospory, and the oldest record so far known of an undescribed fossil Neomeris (from Portugal). © Springer-Verlag Berlin Heidelberg 2012.

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Despite important progress on Amazonian floodplain research, the flooded forest of the Negro River igapó has been little investigated. In particular, no study has previously focused the linkage between fluvial geomorphology and the floristic variation across the course of the river. In this paper we describe and interpret relations between igapó forest, fluvial geomorphology and the spatial evolution of the igapó forest through the Holocene. Therefore, we investigate the effect of geomorphological units of the floodplain and channel patterns on tree diversity, composition and structural parameters of the late-successional igapó forest. Our results show that sites sharing almost identical flooding regime, exhibit variable tree assemblages, species richness and structural parameters such as basal area, tree density and tree heights, indicating a trend in which the geomorphologic styles seem to partially control the organization of igapó's tree communities. This can be also explained by the high variability of well-developed geomorphologic units in short distances and concentrated in small areas. In this dynamic the inputs from the species pool of tributary rivers play a crucial role, but also the depositional and erosional processes associated with the evolution of the floodplain during the Holocene may control floristic and structural components of the igapó forests. These results suggest that a comprehensive approach integrating floristic and geomorphologic methods is needed to understand the distribution of the complex vegetation patterns in complex floodplains such as the igapó of the Negro River. This combination of approaches may introduce a better comprehension of the temporal and spatial evolutionary analysis and a logic rationale to understand the vegetation distribution and variability in function of major landforms, soil distributions and hydrology. Thus, by integrating the past into macroecological analyses will sharpen our understanding of the underlying forces for contemporary floristic patterns along the inundation forests of the Negro River. © 2013 Elsevier Ltd.

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Pós-graduação em Agronomia (Agricultura) - FCA

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

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)