Análise do relevo da Amazônia Central com o emprego de modelo digital de elevação e geometria fractal

Abstract

The central region of the Amazon is located within the largest drainage basin in the world. In the basins of the Uatumã and Urubu rivers in this region, the landscape have drainages with long straight stretches, abrupt inflections, course changes evidenced by abandoned meanders, and basin asymmetries, and smooth variations of the landscape dissection and roughness patterns, which are morphological features suggestive of the action of modern tectonic activity. Geologically, the study area is covered by Tertiary sediments that are cut by normal faults and joints. To identify the influence of surface and subsurface geological structures on relief, we applied geomorphometric techniques on the digital elevation model from SRTM. These techniques have been separated into two groups: 1) basin asymmetry, isobase and river sinuosity were used for reveal the genesis of relief forms, and 2) fractal geometry, drainage density and semivariogram were used to verify the spatial distribution of the roughness, dissection and elevation. Furthermore, the trend-surfaces were also observed by elevation (semivariograma), roughness (self-affine fractal geometry) and drainage density anisotropy (self-similarity fractal geometry). The results of the first group permited the delineation of nine geomorphological domains that exhibit preferential migration paths and a potential relationship to block tilting. The comparison of the boundaries of these domains with geological and geophysical data suggests that these boundaries are likely related to subsurface faults that would have controlled the generation of younger faults and the relief modelling of the region. This interpretation is confirmed by the correspondence between subsurface and surface faults and the boundaries and shapes of the domains, the change in the sinuosity of rivers when crossing boundaries, and the effects of a high concentration of seismic activity along one of the limits on the region. Other geomorphological data also indicate structural control of the relief. There is a relationship between the orientation and approximation of the isobase map lines and the high-angle normal faults mapped in the floodplains of the main rivers. For the second group of variables, the results reveal the spatial coincidence between domains, defined by the analysis of roughness (fractal dimension) and elevation (semivariogram), and subsurface geological structures. This is the case in the area of Silves, where the undulating relief exhibits drainage with annular and radial patterns, coinciding with faults and folds previously mapped by seismic surveys. Another example of such influence is the combination of high magnetic with low dissection pattern mapped by drainage density. In addition to the spatial distribution, trends of these geomorphometric variables were compared among themselves and also with geological information. The results indicate that the predominant directions of the major anisotropy axis is NNE-SSW and NE-SW for the interfluve regions, and NW-SE to the alluvial plains. The ...

A Assimetria De Bacias Hidrográficas E Influências Litoestruturais Na Geomorfologia Do Rio Formoso, To

“…Trabalhos como aqueles de Cox (1994), Salamuni (1998), Ibanez (2012) e Revilla (2012), por focarem a análise morfométrica e geomórfica de bacias hidrográficas e sua coligação com implicações lito-estruturais, têm se destacado por sua utilidade na compreensão do nível de atividade tectônica em diversas regiões, possibilitando fazer inferências sobre as causas dos ajustes longitudinais e laterais em sistemas fluviais (HOLBROOK; SCHUMM, 1999;IBGE, 2009). Neste sentido, Suguio (2010) expõe várias possibilidades de investigação por meio da interpretação geomorfológica, dando destaque ao estudo instrumentalizado (pela morfometria) da rede de drenagem e geoformas correlatas.…”

As gravuras rupestres da bacia do baixo rio Urubu: levantamento e análise gráfica do sítio Caretas, Itacoatiara - Estado do Amazonas. Uma proposta de contextualização

“…Resumindo, a área de estudo é coberta por sedimentos terciários seccionados por falhas normais e juntas que revelam a influência sobre o relevo de estruturas geológicas em subsuperfície como também em superfície (Ibanez, 2012).…”

“…Falhas normais sin-sedimentares em relação à Formação Alter do Chão (FAC) foram observadas em cortes ao longo da rodovia que liga as cidades de Manaus e Itacoatiara (Ibanez, 2012;Silva, 2005 (Tricart, 1985;Müller, 1985). Durante esse período o Amazonas incidiu profundos canais e voltou a sedimentar somente depois do aumento do nível do mar a partir de ̴ 7.000 AP.…”