Interpretation of structural and major drainage systems studied and interpreted by means of remote sensing techniques employing SAC-C and LANDSAT TM 5 images. South AméricaRoberto Torra Departamento de Geociencias. Facultad de Ingeniería. Universidad Nacional del Nordeste. Güemes st No 749, H3500CBO. Resistencia, Chaco, Argentina. roberto_torra@arnet.com.ar Abstract A remote sensing study of structural (tectonic assemblage) and network drainage systems of the South American continent was made. We used SAC - C raw scenes and composed .jpg “free mosaickings” of Landsat TM 5 images which were released by the Geological Survey of the United States (USGS) in your servers. We assemble the SAC-C images in graphic design programs. The LANDSAT TM 5 satellite series, which were nine scenes assembled per each digital archive were handled by means of digital image processing software. We determine the main structural lineaments, geological regional units and the principal drainage systems, including Amazonas, Orinoco, Del Plata, Paraguay, Uruguay and Paraná rivers catchments. Both visual and digital interpretations were made always helped by field works. Continental and regional studies are largely improved by using satellite images of these kinds which carry medium spatial resolution sensors. So, it is very useful for make preliminary structural and drainage interpretations helping land-use and land-management projects due to relative low cost and rapid peer review of the relief and structural framework. Introduction During the last four decades satellite imagery appeared (1972) as a primary tool-technique to help many human activities including most types of physical, human and environmental studies. They are strongly related to civil works due to its direct relation with the study of “sites” of medium-to-large humankind activities as civil works projects emplacements among others. Land use, land management, forestation planning, deforestation exploitation, floodings disasters, risk erosion soils, aridification-desertification geo-indicators, large hydraulic works, “continental pipelines”, strategic dams all were embraces as well as the cattle rising and engineering civil works benefits, among others branches. At the east and central zones of South America, the landscape is largelly characterized by widely flat and/or depressed (lowlands) as well as many medium ridges and extensive plateaus especially at the Brazil, Guyane, Suriname and Venezuela countries relief. A conspicuous extensive “forest” named as the Amazonic Jungle and the inter-tropical wrapper robust vegetation jungles (sometimes called as “Jungas” as in the foreland foothill near the orogen semi-low ridges margin to the Andean Cordillera) covers mainly the Colombia, Ecuador, Perú, Bolivia and Argentina adjoining sectors. These very large vegetated areas constitute a special case for satellite imagery application in order to take quick knowledge of the whole region which comprises approximately about of 3,000.0|00 km2 in opposition to the arid morpho-climatic systems and so take advantage about natural resources. Besides, we must take in consideration that the costs and the fast work in perform all classes of cartographies (i.e. today we are making 3D digital cartography based on satellite imageries and ground position systems points spacially located) are now easily realized with satellite imagery. These results are in this way like largely more effective because of their intrinsic thematic properties, captured for the optical Landsat TM 5 sensor series which are due to sun electromagnetic radiation reflection over the different earth surfaces objects, either natural or anthropogenic. In order to overcome a future long time sustainable program of general planning in the natural resources and communication lines among south-american countries we began several laboratory and field cartographic actions. These were in order to carry out a “preliminary” cartography based on satellite digital data, acquired by means of the Landsat 5 thematic mapper sensor and the SAC – C which have on-board the multispectral medium resolution scanner (MMRS) sensors series (175 m spatial resolution). The main goals of these preliminary cartographies were focused to serve us for generate a sketch map in which we able to embedded firsts order structural and tectonic lineaments as well as the main drainage systems. So, we can able to construct a master cartographic tool for most civil engineers works as well as for the future planning civil works and sustainable development of the humankind. These basical and fundamentals actions are certainly valid at the first stages of many engineerical civil projects and human activities, with special importance to prevent hazardous risks and all classes of large landslides movements doing possible to studied and monitored themselves. These actions and documents are always necessary in order to planning and monitoring different human and natural processes and phenomena with special attention at sustainable region and development. Materials and Methods Satellite imagery analyses were carried out to interpreting and sketching-map about of 3,000,000 millions km2 area which are located at the plains and plateaus of South America continent including Brazil, Argentina, Venezuela, Colombia, Guyana, Suriname, French Guyana, Bolivia, Paraguay and Uruguay. According to Drury (1987) and Sabins (1997), we focused in the employed of optical Landsat TM 5 sensors scenes named as the thematic mapper optical sensor (a special on-board satellite scanner) and some new ones Argentinian’s SAC – C multispectral medium resolution scanner (MMRS) in order to make some comparisons, either spatial, temporal, seasonal, multispectral and radiometric resolutions. The SAC – C orbits employed were 222/000, 223/000, 224/000, 225/000, 226/000, 227/000, 228/000, 229/000, 230/000 and 231/000 all acquired on fall and autumn season on 2000 and 2001. The multispectral medium resolution scanner has a “standard” spatial resolution of 175 meters and its spectral resolution bands include channel 1, 2, 3, 4, 5 being 1, 2, 3 visual spectra and 4-5 near infra-red spectra, somewhat similar to the Landsat sensor. After digital image composition was generated and histogram matching and directional and non-directional filtering was performed, then we made a mosaick with a 4/5/3 enhanced composition. Classical digital image processing software were employed to handle the raw archives of the SAC - C satellite as well as many Landsat TM 5 scenes. Many images observed in the Glo Vis® project (USGS) were studied to complement our analyses of the structural and drainage continent. The images of the Glo Vis servers are resized to 240 and 1000 meters. However, four this class of studies they were fully applicable and very useful. For each orbit-point they are a complete set of composed scenes from different dates which serve us for several critical comparisons. The created sketch-map mosaick was not geo-referenced because the objective of the work.Previously, we made the histogram matching and the feathered processes. We used the five/seven bands that carry the Landsat/SAC – C satellites in order to make several masters datasets in two combinations: 3/4/5 and 4/5/3. So, we create the false-colored images, the unsupervised and supervised classifications and then, we also used it for other transformations as the called as Principal Components Analysis (PCA). Some of these actions were useful for later geomorphological and health-forest interpretations. It necessary to mention that field recognition was made out in several selected field-points to check out interpretations, with special attention to the railroad crossing places. We finally used this temathic-planimetric preliminary cartography for structural and drainage visual analysis and interpretation as well as to outline lowland areas (recurrent floodable sectors) and many active geomorphic elements (i.e. large distal alluvial fans present at the foothill of the Andean foreland areas. Herein, it is include the drainage network system which is basic for any planning of medium-to-large projects as well as a fundamental quantification of the forest and vegetated scarce wrapper area. Results Visual interpretation led us to determine several major structural lineaments directions. This is classical in the specialized literature so we will not describe now these structures. On the contrary, our study, outstandingly, led us to determine several initial and pre-initial rifting system style assemblage models (relatively modern earth elements), all of these corresponding to very well exposed extensional-rotational fracturing model (stretching earth crustal thickness). So, we can appoint the Paraná river rift basin as a typical model. The Paraná river rift basin system, the Paraguay river rift system and the Uruguay river micro-rift initial breaking cortical processes were outlined. The Orinoco rifting framework, the Guyana-Suriname rifting system as well as the Amazonic large rift basin were delimited. These structures have several strikes due a response to the re-accommodation of the South American microplates. The study of these microplates is in progress at present time using satellite imagery. Model of drainage system depends on the scale of observation. In our case, at the plains areas (60 in percentage of the plains) they are classical dendritic-form models due to isotropic condition in the soils. The rivers controlled by rifting are lineal. Conclusions In this study, based on interpretation of satellite data, we were able to determine relation between drainage and tectonic assemblages at regional-continental scales. It was possible to determine first and second order structural basin lineaments as the rift model and detect several initial breaking continental processes as the micro-rift initial system of the Uruguay and Guyana-Suriname regions. All of these tectonic structures are related to cortical stretching processes of the lithospherical bed. The SAC – C images employing the multispectral medium resolution scanner system (MMRS) proved to be a suitable tool to continental and regional studies in spite of their size pixel in the standard mode (175 m). Many interpretations were possible made trough the help of Landsat TM 5 images which were a better spatial resolution in the thematic mapper sensor (30 m). So, more detailed studies require a more sophisticated hardware and software as well as satellite imagery of very high spatial resolution. References
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