Abstract:Hyperextended margins are very heterogeneous along the entire length of the margin, so the definition of tectonic domains made exclusively from 2D seismic sections presents serious limitations. In this work we present an approach of the 3D crustal-scale structure of the West Iberia margin (WIM) by modelling eight lithospheric sections, using seismic, wells and gravity data. The continuous nature of gravity data allowed us to propose a new map of tectonic domains within the WIM. Maps of total horizontal (THD) a… Show more
“…Namely, the boundary between the OMZ and SPZ, which can be inferred to run north of Vila Franca de Xira, links in the offshore with a major NW–SE lineament observed on gravity (Figure 3) and would define the southern limit of the Galicia Bank. This is consistent with the observations of Granado et al (2021) who already suggested that the limit between the northern and central sectors of the WIM follows a NW–SE orientation. This offshore extension of the SPZ–OMZ boundary links with the outermost reach of Profile B, at the boundary between the hyperextended and strongly rifted domains.…”
Section: Discussionsupporting
confidence: 93%
“…The total horizontal derivative of the upward continuation of the Bouguer anomaly has been calculated as strong gravitational gradients are interpreted to mark the proximal and distal domains (Fernandez et al, 2020; Granado et al, 2021) (Figure 3). Details on the seismic and gravity data used as well as interpretation workflow followed in this study can be found in the Supporting Information.…”
Section: Methodsmentioning
confidence: 99%
“…Whereas most models of evolution of the Iberian Margin are based on a relatively simplified bi‐dimensional view of the margin, the underlying heterogeneity of the margin has been made evident by multiple authors (e.g. Granado et al, 2021; Sutra & Manatschal, 2012; Welford et al, 2010). Some have attempted to account for this variability by understanding the impact of pre‐rift inherited continental structure (Buiter & Torsvik, 2014; Chenin et al, 2015; Manatschal et al, 2015; Nirrengarten et al, 2018).…”
The passive margin of Western Iberia (WIM) developed during the Mesozoic over the pre-existing Variscan Orogen. In the present study we use integrated interpretation and modelling to understand the distribution of Variscan basement provinces in the offshore of Iberia. The NW-SE trending fabric of the Variscan Orogen can be recognized in the WIM, and different Variscan basement provinces behaved differently during extension. Furthermore, major Variscan structures reactivated in extension, compartmentalizing rifting and having a major impact on the final architecture of the WIM.
“…Namely, the boundary between the OMZ and SPZ, which can be inferred to run north of Vila Franca de Xira, links in the offshore with a major NW–SE lineament observed on gravity (Figure 3) and would define the southern limit of the Galicia Bank. This is consistent with the observations of Granado et al (2021) who already suggested that the limit between the northern and central sectors of the WIM follows a NW–SE orientation. This offshore extension of the SPZ–OMZ boundary links with the outermost reach of Profile B, at the boundary between the hyperextended and strongly rifted domains.…”
Section: Discussionsupporting
confidence: 93%
“…The total horizontal derivative of the upward continuation of the Bouguer anomaly has been calculated as strong gravitational gradients are interpreted to mark the proximal and distal domains (Fernandez et al, 2020; Granado et al, 2021) (Figure 3). Details on the seismic and gravity data used as well as interpretation workflow followed in this study can be found in the Supporting Information.…”
Section: Methodsmentioning
confidence: 99%
“…Whereas most models of evolution of the Iberian Margin are based on a relatively simplified bi‐dimensional view of the margin, the underlying heterogeneity of the margin has been made evident by multiple authors (e.g. Granado et al, 2021; Sutra & Manatschal, 2012; Welford et al, 2010). Some have attempted to account for this variability by understanding the impact of pre‐rift inherited continental structure (Buiter & Torsvik, 2014; Chenin et al, 2015; Manatschal et al, 2015; Nirrengarten et al, 2018).…”
The passive margin of Western Iberia (WIM) developed during the Mesozoic over the pre-existing Variscan Orogen. In the present study we use integrated interpretation and modelling to understand the distribution of Variscan basement provinces in the offshore of Iberia. The NW-SE trending fabric of the Variscan Orogen can be recognized in the WIM, and different Variscan basement provinces behaved differently during extension. Furthermore, major Variscan structures reactivated in extension, compartmentalizing rifting and having a major impact on the final architecture of the WIM.
“…In the NE Atlantic, a similar marine MT acquisition campaign in the Porcupine Basin or Rockall Trough could settle long-standing debate on the existence of serpentinization (Reston, 2009). Finally, a calibration MT survey along exhumed mantle zone of the Western Iberian Margin (Granado et al, 2021) could broaden the scope of our research to magma-poor passive margins.…”
Abstract. An analysis of two decades (2003–2022) of seismicity recorded by the Spanish and Portuguese seismic networks along the West Iberian passive margin has resulted in a better understanding of the distribution of moderate seismic activity in this intraplate submarine area. The study provides a precise trend of specific alignments inferred from the density maps of seismicity, giving an accurate depiction of event distribution along two wide stripes that extend 700 km long through the ocean floor in a WNW-ESE direction. These bands are parallel to the Africa-Eurasia plate boundary but are distinctly separated from its related seismicity by approximately 300 km and 700 km, respectively. This is a sufficient distance to be considered as intraplate activity. When trying to relate this seismicity to structural and geophysical features, a conclusive picture doesn't emerge. The earthquakes occur indiscriminately across thinned continental, hyperextended, and exhumed mantle rift domains. They fade out in the proximity of undisputed oceanic crust, but some events extend beyond. The hypocentral depths signal a considerable amount of events nucleating in the upper mantle. The focal mechanisms, although scarce, are predominantly strike-slip. Considering these observations, hypothesis ranging from subduction initiation, development of strained corridors or local structures of the margin, have been discussed in order to explain this relatively anomalous seismicity. However, some of them do not portray convincing arguments, while others are too unspecific. None of them are flawless, suggesting that several factors may be at play. Despite being one of the most probed passive margins in the world, the present geodynamical status of the West Iberian Margin manifested in its modern seismicity remains unknown. Interpreting this data within a global tectonic plate framework, together with the potential addition of seafloor seismometers, may provide the key to understanding this activity along one of the most archetypical margins of the Atlantic Ocean.
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