Papers by Natasha Stanton
We have processed the EMAG2v3 observed full field magnetic anomaly (Meyer et al., 2017) using the... more We have processed the EMAG2v3 observed full field magnetic anomaly (Meyer et al., 2017) using the magnetic potential transformation to make a pseudo-gravity anomaly map for the South Atlantic between 15° S and 40° S. A pseudo-gravity transformation attempts to remove the dipolar complexity of a magnetic anomaly and produce the equivalent gravity anomaly assuming a constant ratio of magnetization to density contrast. We assume that magnetization is induced. Our South Atlantic study area encompasses the major bathymetric features of the Rio Grande Rise (RGR) and Walvis Ridge (WR), as well as the Brazilian and African rifted margins.On the Brazilian continental margin, there are high positive pseudo-gravity anomalies on the São Paulo Plateau (SPP) in the Santos Basin, as well as on the Florianópolis Ridge (FR). The distal Campos Basin also shows high positive pseudo-gravity anomaly. The southern Pelotas Brazilian rifted margin shows negative pseudo-gravity anomaly becoming positive oceanward on the Torres High. In the oceanic domain the Rio Grande Rise (RGR) shows three units of high positive pseudogravity anomalies. Although the RGR presents high amplitude pseudo-gravity anomalies, they are not homogeneous. The Eastern RGR has the most intense and linear N-S anomaly, while its Central unit has a circular pseudo-gravity anomaly and is more constrained in area. The Western RGR has a lower amplitude pseudo-gravity anomaly. The C34 magnetic anomaly region, separating the Eastern and Central RGR, shows a negative pseudo-gravity anomaly. Negative pseudo-gravity anomalies indicate that the assumption of entirely induced magnetization used in the pseudo gravity transformation is invalid and that significant long wavelength remnant magnetization exists. This may indicate heterogeneity of the magnetized layer as well as the effects of magnetic field reversals.On the African plate, very strong positive pseudo-gravity anomalies occur on the inner WR and the SW African continental margin. The positive pseudo-gravity anomalies of the WR and the beginning of the outer SW trending WR “tail” create a very strong continuous positive pseudo-gravity anomaly. Together with the South African rifted margin, it forms a strong positive anomaly with a “7” shape. Westwards of the C34 magnetic anomaly there are no significant large amplitude pseudo-gravity anomalies.The map of the pseudo-gravity has been restored using the GPlates reconstruction software. At 110 Ma, the SPP is near the inner WR and both show high amplitude positive pseudo-gravity anomalies. At 110 Ma, the FR is close to the most distal portion of the inner WR, both showing positive pseudo-gravity anomalies. At 85 Ma, the Central RGR, the western extremity of the inner WR and the start of the WR “tail” show conjugate positive pseudo-gravity anomalies. After the C34 anomaly, seen as an intense negative pseudo-gravity anomaly, the Eastern RGR and its conjugate WR “tail” both show positive pseudo-gravity anomalies and separate at ~ 65 Ma. The pseudo-gravity anomaly map indicates that the RGR and WR comprise distinct units which are correlated across the ocean and which correspond to the multiple oceanic ridge jumps reported in Graça et al. (2019).
Oecologia Australis, Jan 8, 2010
Journal of South American Earth Sciences
Second EAGE Conference on Pre-Salt Reservoir, 2021
84th EAGE Annual Conference & Exhibition
Journal of Structural Geology, Sep 1, 2017
The Ararauama Lagoon Fault System composes one of the most prominent set of lineaments of the SE ... more The Ararauama Lagoon Fault System composes one of the most prominent set of lineaments of the SE Brazilian continental margin. It is located onshore in a key tectonic domain, where the basement inheritance rule is not followed. This fault system is characterized by ENE-WSW silicified tectonic breccias and cataclasites showing evidences of recurrent tectonic reactivations. Based on field work, microtectonic, kinematic and dynamic analysis, we reconstructed the paleostresses in the region and propose a sequence of three brittle deformational phases accountable for these reactivations: 1) NE-SW dextral transcurrence; 2) NNW-SSE dextral oblique extension that evolved to NNW-SSE "pure" extension; 3) ENE-WSW dextral oblique extension. These phases are reasonably correlated with the tectonic events responsible for the onset and evolution of the SE onshore rift basins, between the Neocretaceous and Holocene. However, based on petrographic studies and supported by regional geological correlations, we assume that the origin of this fault system is older, related to the Early Cretaceous South Atlantic rifting. This study provides significant information about one of the main structural trends of the SE Brazilian continental margin and the tectonic events that controlled its segmentation, since the Gondwana rifting, and compartmentalization of its onshore sedimentary deposits during the Cenozoic.
Trabajos de Geologia, 2010
EGU General Assembly Conference Abstracts, Apr 1, 2013
AGU Fall Meeting Abstracts, Dec 1, 2012
The morphology of the South Atlantic Ridge is analyzed focusing on its large scale segmentation. ... more The morphology of the South Atlantic Ridge is analyzed focusing on its large scale segmentation. Variation of the axial topography was correlated to Mantle Bouguer Anomaly in a way to infer the mantle processes governing the observed morphology. We observed three main topographic domains along the ridge axis, which are approximately around 10oS, 20oS and 35oS. The first and the third domain exhibit shallower and smoother ridge topography, while the central one displays a deeper and segmented morphology. We noticed at least 20 tectonic segments, mainly defined by the continuity of the fracture zones towards the continental margins. Bathymetric and gravity correlation along the ridge axis showed that some segments are inflated with a high in the middle of the segment and lacking rift valley. This seems to be the result of focused and intense magmatism, especially near the Ascension and Tristan da Cunha regions. On the other hand, the central part of the South Atlantic is apparently dominated by a widespread and discontinuous magmatism.
This study investigates the rifting architecture and tectonic evolution of Santos Basin at Southe... more This study investigates the rifting architecture and tectonic evolution of Santos Basin at Southeastern Brazilian Margin, based on integrated geophysical data. A high resolution aeromagnetic grid is correlated with gravity anomalies and published seismic lines, in order to provide a regional view of the Santos Basin. We calculate the magnetic basement using the power spectrum analysis, which enabled us to constrain the basement geometry at the proximal and necking domains at Santos Basin. Our results suggest a tectono-structural transition from proximal to distal parts of the margin. Each domain is characterized by intrinsic rifting structures, where continental inheritance seems to predominate at the proximal domain while towards the distal margin, increasing oceanic parallel structures can be observed, suggesting the predominance of mantle dynamics on rifting evolution. We propose that the northern Santos Basin consists of an intensely deformed zone where rifting evolved under oblique extension adjacent to a transform plate boundary.
Journal of South American Earth Sciences
Brazilian Journal of Geophysics
The SEMA (South East Magnetic Anomaly) is a high amplitude magnetic lineament in the most distal ... more The SEMA (South East Magnetic Anomaly) is a high amplitude magnetic lineament in the most distal part of the Campos Rifted Margin in Southeast Brazil. It runs continuously from south to north along 85 km reaching 500 nT in deep waters. The aim of this paper is to investigate the structure, stratigraphy and nature of the SEMA, and to discuss its significance for the evolution of the margin. Based on seismic, magnetic and gravity analysis, we interpret the SEMA as a volcanic outer high. Its formation was prior to the salt migration oceanwards, probably earlier to the breakup, constraining a time-relative formation in the Late Aptian - Early Albian. It is bounded by a basinward dipping, large-scale fault that created a huge depocenter continentwards. The Volcanic Outer High of the SEMA marks the transition to a distinct tectonostratigraphic compartment and salt domain, characterized by intense halokinesis, significant thinning and modification of the pre-salt sequences, and increasing ...
The study of rifted margins shall involve the investigation of the preexistent lithosphere, which... more The study of rifted margins shall involve the investigation of the preexistent lithosphere, which rheological and mechanical behavior under extension is complex since it is the product of numerous tectonic events. In order to understand such complexity, we need to know the initial pre-rift composition of the continental crust and lithosphere. It has been shown that compositional inheritance influences the distribution or localization of deformation, the ocean-continent transition structure (OCT) and magmatism. Variations in lithosphere rheology result in different styles of depth-dependent extension (Huisman and Beaumont, 2011) and margin geometry. In this study we investigate the Campos Rifted Margin architecture on the Southeastern Brazilian Margin, with the aim of exploring the role of Precambrian/Eo-Paleozoic basement inheritance and early magmatism on basin evolution. We present a new compilation of aeromagnetic data, integrated with seismic interpretation and crustal thickness...
EGU General Assembly Conference Abstracts, Apr 1, 2019
EGU General Assembly Conference Abstracts, Apr 1, 2019
Meso-Cenozoic Brazilian Offshore Magmatism, 2022
Uploads
Papers by Natasha Stanton