Subcontinental Geologic Mapping using the MMRS Sensor (SAC-C Satellite Mission-Matutine Constellation). - An example of central regions of South America  Roberto Torra Departamento de Geociencias. Facultad de Ingeniería Universidad Nacional del Nordeste. Güemes st. No. 749. H3500CBO, Resistencia, Chaco, Argentina. E-mail: roberto_torra@arnet.com.ar This paper is focused in describing and interpreting the main geologic features of about 500.000 km2 located at the central South America region. The study is mainly based on the use of remote sensing low resolution -thought with a large area coverage- satelital data and techniques. The study area comprises a fair rectangle outlined between 22º 45’ 00’’ - 33º 30’ 00’’ south latitude and 54º 30’ 00’’ - 62º 30’ 00’’ west longitude. It embraces the northeastern sector of Argentina, the west of Uruguay, the south, west and east of Paraguay and some neighbouring small sectors of Brazil. The study was carried with handling SAC - C Satellite Mission images named as path 224/000, 225/000, 226/000 and 227/000 (orbits) which belong to the multispectral medium resolution sensor (MMRS), a 125 meters optical-pixel resolution instrument. Digital image processing was used to handle the BSQ data. Therefore we were able to create the scene compositions, mosaicking and cutting the study area. The final composicion used was 4/5/3 which adapted perfectly to predominant conditions on the wet seasson (automn). Anywere we used too a 3/4/5 composicion in order to compare with the 4/5/3 and so extrapolate some very well known trainning areas of wide cobertures. These cobertures were perfectly checked at the field. Clouded areas were minus than 5 in percentage on the entire mosaick (small sectors at the extreme north and south of the builded mosaick). Main large crustal lineaments, not previously mentioned and never properly understood, were carefully detected and draw. The keys used for mapping lineaments were shadows and highlights and change of coberture which implies an abrupt variation in the tone-area and lithology. The analysis of the main physics features as river drainage, low ranges, extense plains, large lagoons models, immense wetland masses models, deltas models, curvilines scarpments models, several extense faulting lineaments models. The present of some volcanic aparatous dome-model of Quaternary age were used too as a tool for interpretation. The outlined physics characteristics correspond to an extensional faulting system arrangement, which could be properly relationed to a subcontinental active partially simetrical immense rift system. The assemblage of delimited fault systems may be brokening the crustal surficial rock segments all along more than 2,000 km in a north-south direction. The pattern shows too a fracturing model of giant semi-circular rupture (colapse and sliping faults) to the east, at the Brazilian and Argentinian territories. To the west it seems to be a little bit more straight faults. Oblique system faults also may be recognized, specially at Paraguay and Argentine regions. The recent vulcanism activity phenomena are surprisingly well developed at the Paraguay pampas (west). Near Argentina borders they appears as a “dome” model in Paraguay, to pass through Paleozoic and Mesozoic units. Many Pliocene-Quaternary aparatous volcanic appears at the proximity and into them of the Argentinian “Pampas Ranges”. Some domes are very well fractured which is easy to improve with directional filters. It is proposed that this rift system could be extend to the Amazonas river and finish at their mouth. In this case of very extended territories contextual consideration, the rift system analized turn on to a very complex system run into very different stages of develops. Apart from the imagery study, this conclusion is supported by more than ten years of field work as well as many sismic and wells register check data (Torra, 2001). Reference cited TORRA, R. (2001) Sedimentología de la Formación Ituzaingó (Mioceno medio), en los sectores norte y oeste de la Mesopotamia, Argentina. Unpublished Doctoral Thesis. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Instituto de Estratigrafía y Geología Sedimentaria Global (IESGLO). Universidad Nacional de Tucumán. II Volumes. 417 p. |