Abstract Tectonic rejuvenation has been widely described in ancient rifting areas of intraplate settings, despite extensive active tectonics being discontinued long ago. Various models have been invoked to justify such tectonic rejuvenation, suggesting that the long-term deformation in intraplate interiors may be more complex than once supposed. Inherited weakness zones, e.g., pre-existing faults are stress concentrators. However, not all weakness zones in plate interiors show tectonic rejuvenation and recognizing intraplate fault reactivation remains puzzling. Bedrock channels play an essential role in tectonically unstable landscapes and therefore they may unveil which pre-existing structures have been rejuvenated. Here we explore the Cinzas Catchment in order to investigate the interactions between tectonic rejuvenation, bedrock inheritance and geomorphic river signatures in an important Brazilian rifting feature, the Ponta Grossa Arch. We perform a geomorphic analysis combined with fieldwork, dating techniques and existing data to evaluate whether the geomorphic responses of the major rivers show perturbations related to the bedrock inheritance and post-rift rejuvenation. We also show that the interactions between river signatures and the bedrock fault zones are responses to post-rifting rejuvenation coupled with bedrock inheritance. This post-rifting rejuvenation is consistent with a mosaic of superimposed mechanisms which have been invoked by previous studies.

Abstract The Santos Basin, with an area of about 350.000 km 2 , is the largest salt basin of the South Atlantic, and due to its high economic hydrocarbon potential, it is a recurrent theme in scientific studies. The salt structures over the region present great importance for hydrocarbon accumulation and the geological/geophysical studies are performed from seismic reflection data, which requires time and efforts for acquisition and data processing. We identify salt structures using a new workflow based on inversion of residual gravity anomalies, where we use the Moho and basement depths obtained from gravity inversion, followed by the calculation of the gravity residual anomaly, assumed to be representative of the salt structures. This workflow is tested for a geological profile in the Santos Basin, and the results are evaluated along a 2D seismic section tied to well markers. The geometry of the stratified salt obtained from gravity inversion correlates with the seismic interpretation, with the advantage of estimating the entire salt package, including halite and stratified salt. With only seismic data, sometimes the stratified salt can be misinterpreted as sediments. The procedure can be applied to identify salt in sedimentary basins where seismic data is unavailable or of low quality.

Abstract: Seismic is one of the main methods used for the identification of structures and stratigraphic studies in sedimentary basins. In the Santos Basin, numerous 2D and 3D seismic surveys are being conducted in order to get a better image of the geological section to depths beyond the base of salt layer. Crustal modelling studies that make joint interpretation of seismic and gravity data are found in the literature, however there are few studies that relate gravity anomalies directly to salt structures. This work aims to associate gravity anomalies with salt structures from seismic and gravimetric interpretation. For studies aimed to model the crustal structure from gravity field data, the knowledge of two major discontinuities is required, the basement and the Moho. Such interfaces are often not easily seen by seismic and so, during this study, they were found by different methods involving analysis of gravity anomalies. The other interfaces involving density contrasts were analyzed based on seismic interpretation. The results showed that the obtained seismic geological interpretations may provide additional information when compared to gravity anomaly data. In all the modelled profiles, some geological information of the Santos Basin that are not visible in the seismic, could be interpreted according to the geological model and the adjustment of gravity anomaly curves. As a final conclusion of this work, it is suggested that the combined analysis of the two cited geophysical methods, can provide important information about the crustal structure and to assist in modelling the salt layer.

Resumen: El método sísmico es uno de los muchos usados para la identificación de estructuras y en estudios estratigráficos en cuencas sedimentarías. En la cuenca de Santos, numerosos estudios sísmicos han sido llevados a cabo con el propósito de obtener una mejor imagen de la sección geológica a profundidades más allá de la base de la capa de sal. En la literatura, se encuentran estudios de modelado de la corteza que hacen interpretación conjunta de datos sísmicos y de gravedad, sin embargo, hay pocos estudios que relacionan directamente anomalías de gravedad a estructuras de sal. Este trabajo busca asociar anomalías de gravedad con estructuras de sal interpretadas a partir de datos sísmicos y gravimétricos. Para los estudios encaminados a modelar la corteza a partir de datos de campo de gravedad de la corteza, se requiere el conocimiento de las dos mayores discontinuidades, basamento y Moho. Estas interfaces a menudo no son fáciles de ver mediante sísmica y por esto durante este estudio, ellas fueron encontradas por diferentes métodos envolviendo análisis de anomalías de gravedad. Las otras interfaces que involucran contrastes de densidad se analizaron mediante interpretación sísmica. Los resultados mostraron que las interpretaciones sísmicas y geológicas obtenidas podrían proporcionar información adicional al compararlas con los datos de anomalía de gravedad. En todos los perfiles modelados, alguna información geológica de la cuenca de Santos que no es visible en la sísmica, podría ser interpretada de acuerdo a el modelo geológico y al ajuste de las curvas de anomalía de gravedad. Como una conclusión final de este trabajo, es sugerido que el análisis combinado de los dos métodos geofísicos citados, puede proveer información importante acerca de la estructura de la corteza y ayudar en el modelado de la capa de sal.

Este trabalho visa estimar e analisar a variação dos elementos do campo de gravidade na região do Aqüífero Guarani em um período de dois anos e três meses - abril de 2002 a julho de 2004 - usando os dados da missão GRACE. Esta variação engloba todas as mudanças de gravidade que são causadas por variações na distribuição de massa da superfície da Terra e pela deformação da Terra Sólida em resposta a estas variações de massa, estimadas pelos coeficientes de Stokes fornecidos pela missão GRACE. As soluções foram obtidas somente a partir de perturbações de órbita de satélites independentemente de dados de gravidade na superfície oceânica e continental. As soluções mensais do campo gravitacional da Terra fornecidas pela missão GRACE, considerando o grau e a ordem máximos de expansão dos elementos do campo de gravidade em harmônicos esféricos de 150 (fevereiro de 2003 a julho de 2004) e 120 (abril, agosto e novembro de 2002), foram processadas e forneceram valores de altura geoidal e anomalia ar-livre para cada conjunto destas soluções mensais, juntamente com os erros associados. Uma inversão linear 3-D da altura geoidal residual foi realizada para obter a distribuição de densidades tridimensional associada a estas variações, verificando-se assim a viabilidade do uso dos dados do GRACE na investigação da variação das massas de água no Aqüífero Guarani. A partir da anomalia ar-livre e dos dados de um modelo topográfico digital da região obteve-se também a anomalia Bouguer em um perfil representativo do aqüífero, a fim de estimar a correspondente variação da massa de água na região analisada.

This work estimates the variation of the gravity field elements in a period of two years and three months - April 2002 to July 2004 - using the GRACE mission data in the Guarani aquifer region; these changes are the sum of all the gravity changes that are caused by variations from mass distribution of the Earth's surface and by the deformation of the solid Earth in response to these mass variations. The solutions have been calculated only from the disturbances of the satellite orbits and do not depend on the gravity data available in the oceanic and continental areas. The calculations of the Earth's gravity field monthly solutions by using the GRACE mission data, considering the spherical harmonics, i.e., the Stokes coefficients, for the global gravity field, up to degree and order 150 (February/2003 to July/2004) and 120 (April, August and November 2002), have been transformed in geoidal height and free-air anomaly grids, with the respective associated errors. A linear 3-D inversion using the residual geoid height supplied the three dimensional density distribution, showing that the use of the GRACE data in investigation of the water mass variability in Guarani aquifer is feasible. A Bouguer anomaly profile, calculated by using the GRACE free-air anomaly and a digital topographic model data, was used in order to estimate the water mass variation in the Guarani aquifer region.