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| Author(s): |
Denise Silva de Moura
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto Astronômico e Geofísico (IAG/SBD) |
| Defense date: | 2024-08-08 |
| Examining board members: |
Carlos Alberto Moreno Chaves;
Gabriel Negrucci Dragone;
Sérgio Luiz Fontes;
Walter Eugênio de Medeiros;
Marcelo Peres Rocha
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| Advisor: | Yara Regina Marangoni; Carlos Alberto Moreno Chaves |
| Abstract | |
In the southeastern region of the South American platform, there are a variety of geological features, such as cratons, orogenic belts, suture zones, and magmatic events, including a magmatic province. To study these structures, especially under the Paraná, Chaco-Paraná, and Pantanal basins, two complementary geophysical methods were used: gravimetry and surface wave tomography. Initially, a new complete Bouguer anomaly map for the area was developed by combining land gravity data with a regional model. Subsequently, the gravitational influence of known masses was calculated, and after removing these components from the Bouguer anomaly, a residual anomaly map was obtained. Based on this residual and three 2D forward models, a review of the geometry of the Paranapanema block and the Luiz Alves craton was presented, along with a new delimitation of the influence region of the Ponta Grossa dike swarm. Additionally, two independent S-wave velocity models were calculated, derived from ambient seismic noise and earthquakes, which enabled the imaging of the crust and lithospheric mantle structure under the study region, respectively. In the lithospheric mantle, high velocities were identified in the region of the Paraná basin and the São Francisco, Amazonian, and Luiz Alves cratons, whereas low velocities were identified under the Pantanal basin, which may be associated with possible lithospheric thinning. A strong contrast of seismic velocities, separating the eastern edge of the Pantanal basin from the Paraná basin, coinciding with the West Paraná Suture, was imaged by our model. A Moho depth map derived from seismic velocities was also estimated, which shows a good correlation with previous results, but with a thicker crust (~43 km) under the central Chaco-Paraná basin than previously estimated by earlier studies. This thicker crust, along with its counterpart in the Paraná basin, shows an excellent correlation with the surface-mapped area of the magmatic floods that form the Paraná Magmatic Province (PMP), suggesting that magmatic processes were important not only in the Paraná basin but also in the Chaco-Paraná basin. This study, therefore, suggests that the identified thickening may indicate underplating in the region. Finally, with a joint interpretation of the two studies, the residual Bouguer anomaly was recalculated using the same methodology as in the first study but with the Moho depth map derived from the second one. With this new result, it was possible to validate the underplating hypothesis with gravity data and present possible models of thickness and density contrast of this excess mass under the PMP. (AU) | |
| FAPESP's process: | 18/19562-2 - Study of physical and structural properties in the region of the Pantanal, Paraná and Chaco-Paraná basins using joint inversion of gravimetric observations and surface waves velocity |
| Grantee: | Denise Silva de Moura |
| Support Opportunities: | Scholarships in Brazil - Doctorate |