Examinando por Autor "Introcaso, Antonio"
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Ítem Acceso Abierto A plastic rheology phenomenological 201 . model that explains the Andes evolution in northern Argentina(Instituto de Fisiografía y Geología. Facultad de Ciencias Exactas, Ingeniería y Agrimensura. Universidad Nacional de Rosario, 27/12/2012) Introcaso, Antonio; Giménez, Mario; Martínez, María Patricia; Ruiz, FranciscoA plastic rheology, partially phenomenological model is presented to explain the isostatically compensated Andean relief formation. This model considers a combination of lithospheric heating with long period relaxation and successive crustal shortenings on a north section of Argentina located at 24°S latitude. The present size of the Andean root –related to the Andes construction– was obtained by inverting regionalized Bouguer anomalies, also consistent with geoid undulations. The relief of 1520 km is balanced both with a thermal root of 70.63 km located at the lithospheric mantle and 2 with an evolutionary crustal root originated by shortenings. A pretended contradiction must be noted: lateral compressive shortenings and side moving tending to squash and to widen the high relief. For better understanding the problem, a linear model is first presented. Then, a nonlinear model of plastic rheology is considered with a stability coefficient depending on width and elevation. We have assumed that isostatic balance keeps on the whole orogenic construction. We also impose an empirical stability relationship. If this relationship does not hold, there will be an extra relief and therefore an extra root that will plastically flow until reaching stability.Ítem Acceso Abierto Alternative gravimetric methodology for isostatic analyses. An example for Bolivian Andes(Instituto de Fisiografía y Geología, 2008-12) Crovetto, Carolina Beatríz; Introcaso, AntonioIn this work we present a new, alternative methodology for performing isostatic studies by means of geoid undulations, excluding the use of measured gravity anomalies. An example on Bolivian Andes is presented as case study. Considering a digital elevation model as input data, a theoretical perfectly isostatically balanced Airy crustal model was constructed for Bolivia. The free-air and the Bouguer anomalies, and the geoid undulations produced by this theoretical model, were directly evaluated by means of three-dimensional integration. The “real” geoid undulations were computed from the EGM96 global geopotential model, and were filtered from long wavelengths by means of a sparse Fourier transform method. The residual “real” geoid undulations were compared with the theoretical geoid undulations for Bolivian Andes, showing a global tendency towards isostatic balance, agreeing with previous results obtained using traditional gravimetry. The free-air and the Bouguer anomalies from the EGM96 residual geoid undulations were also evaluated and then compared with the anomalies produced by the theoretical model. The Bouguer anomalies support definitely the results obtained using the geoid undulations while the free-air anomalies, although less consistently, showed the same global tendency.Ítem Acceso Abierto Anomalous upper mantle beneath the Central Andes : isostasy and Andean uplift(Instituto de Fisiografía y Geología, 2001) Introcaso, AntonioFour theoretical models isostatically compensated were prepared and compared between themselves in order to analyze either the isostatic equilibrium or the probable mechanisms for justifying the Central Andean uplift. They are: Model 1, or Airy Model: in this classical model the isostatic compensation would take place at the maximum Moho depth's level: 61.7 km. Model 2: this model justifies the Andean elevation by means of a combination of lithospherical thermal root and crustal root. In this case, the last one is diminished 5.3 km respect to crustal root's thickness of Model 1. Isostatic compensation takes place here at the bottom of thermal lithosphere: 140 km deep. Model 3: this model explains the elevation by means of a combination of the subsidence that the subducted Nazca Plate could produce, and the crustal root effect, that is 6 km thicker than the first model's root. The isostatic compensation could take place at a depth of 300 km. Model 4: this model involves Models 1, 2 and 3 mechanisms; the isostatic compensation takes place at a depth of 300 km. Crustal shortenings S are sensitive to the upper mantle's heterogeneity, varying from 17% to +18%, h as it is shown by the following values: S = 278 km (Model 1), S = 230 km (Model 2), S = 338 km (Model 3) and h h h S = 288 km (Model 4). h We also demonstrate that the model selected for evaluating the Andean isostatic equilibrium in this zone of the anomalous upper mantle is not critical. The analysis of the two EW gravity sections at 22°S and 24.5°S latitudes favors Model 2 as the most likely, since the crustal thickness found from it is clearly consistent with seismic data available at 24.5°S. Nevertheless, we can admit other gravimetric models.Ítem Acceso Abierto Auscultamiento de estructuras geológicas en la cuenca chacoparanense a partir de la aplicación de métodos potenciales(Asociación Geológica Argentina, 2005-04) Gimenez, Mario E.; Martínez, Patricia M.; Ruíz, Francisco; Introcaso, AntonioSe presenta en el área de la cuenca Chacopampeana, noroeste de Argentina, un análisis preliminar geológico - geofísico, basado en los métodos potenciales.El área de estudio se ubica hacia el noreste de la ciudad de Santiago del Estero y parte noroeste de la provincia de Chaco, entre los 25° y 27° S de latitud y 61° a 63° O de longitud. Se relevaron aproximadamente 1.000 nuevos puntos gravimétricos, que fueron agregados a la base de datos del Instituto de Física de Rosario, Universidad Nacional de Rosario y del Instituto Geofísico Sismológico Volponi, Universidad Nacional de San Juan. Con los datos obtenidos se preparó una carta de anomalías de Bouguer. La carta de anomalías, fue filtrada y procesada para separar efectos gravimétricos y se confeccionó un modelo cortical para una sección A-A´. El modelo cortical, indica la presencia de una estructura ubicada en la corteza superior. Este modelo justifica la residual de Bouguer.El área de estudio, posee características geológicas adecuadas de presencia de hidrocarburos, pero hasta el momento no se han descubierto estructuras geológicas de interés económico. En el presente estudio, mostramos una anomalía de Bouguer positiva, sin evidencias superficiales que podría interpretarse como una estructura geológica con potencial económico.Ítem Acceso Abierto Geodesia física(Instituto de Fisiografía y Geología, 2006-06) Introcaso, AntonioÍtem Acceso Abierto Geoid undulations chart of the San Luis range (Argentina). Geophysical application(Instituto de Fisiografía y Geología, 2008-12) Cornaglia, Laura L.; Introcaso, AntonioIn this work we show that it is possible to define the isostatic state of a geological structure using a geoid undulations chart. We have built: (1) a detailed geoid undulations chart of the San Luis range area using (a) the global geopotential model EIGEN CG03C for long wavelength free-air gravity anomalies and geoid undulations, and (b) observed residual free-air gravity anomalies and the equivalent sources method for short wavelength geoid undulations, and (2) a theoretical undulations chart of San Luis range area, involving effects from an isostatically compensated model. By comparing charts (1) and (2) we have found agreement between them, thus indicating the San Luis range is rather well isostatically balanced.Ítem Acceso Abierto A stretching model to explain the salado basin (Argentina)(Instituto de Fisiografía y Geología, 2007) Crovetto, Carolina Beatríz; Novara, Iván L.; Introcaso, AntonioSalado Basin, placed in Buenos Aires province, Argentina, is one of the most studiedsedimentary basins of the area because it curiously presents a significative positive residual Bouguer anomaly.Several models were proposed to explain this gravimetric anomaly in the last 50 years. Recently, some worksincorporated geoid undulations, revealing also a positive geoid anomaly over the basin. In this work, wepropose a stretching model in perfect Airy isostatic balance to study the Salado Basin. We make a three-dimensional study of the basin's balance from gravity anomalies and geoid undulations, finding a strongoverbalance on it.Ítem Acceso Abierto Study of the Claromecó Basin from gravity, magnetic and geoid undulation charts(Instituto de Fisiografía y Geología. Facultad de Ciencias Exactas, Ingeniería y Agrimensura. Universidad Nacional de Rosario, 2011-07-01) Ruiz, Francisco; Introcaso, AntonioIn this work we analyze crustal characteristics of Claromeco intermontane basin using gravity and magnetic anomalies, and local geoid undulations. They are: i) isostatic compensation (based on Airy hypothesis), related to stretching; ii) old sediments filling the basin, covering more than 12 km, with a density contrast value of -100 kg m (super -3) , resulting to be well balanced by an antiroot filled with upper mantle materials. A crustal model is proposed justifying both observed Bouguer anomalies and local geoid undulations. A chart of isobath contours is built using a quadratic equation involving sediments' thickness and local geoid undulation. Magnetic basement depth Z T and Curie point depth Z B are obtained using spectral analysis on a total field magnetic anomaly chart. Results show that Z T reaches a maximum value of 12 km, whereas Z B attains a minimum value below the Claromeco basin. The basin puts aside two different depth domains of the Curie isothermal surface: at the southwestern zone of the Ventania ranges Z B is about 25 km, while northeast of these mountains Z B is about 30 km.