Conjugate volcanic passive margins in the austral segment of the South Atlantic – Architecture and development

Chauvet, François; Sapin, François; Geoffroy, Laurent; Ringenbach, Jean‐Claude; Ferry, Jean-Noël

doi:10.1016/j.earscirev.2020.103461

Cited by 46 publications

(54 citation statements)

References 180 publications

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“…z LAB,pres in the center of the margin profiles is, however, similar for both margins (100-110 km), representing typical values for cooled oceanic lithosphere (e.g., Richards et al, 2020). The observed asymmetry is in agreement with a study of Chauvet et al (2021), who relate the asymmetry of conjugate SDR sequences in the Austral Segment to variations in the thermal structure.…”

Section: Salado/southwest African Marginsupporting

confidence: 86%

“…The gray‐scale background plot shows topography. Dark‐red polygons depict extension of Seaward Dipping Reflectors and Large Igneous Provinces (Chauvet et al., 2021; Coffin et al., 2006; McDermott et al., 2018). South American passive margin—(a)crystalline crustal thickness for COT and inner extension area and (b) estimated stretching factors.…”

Section: Methodsmentioning

confidence: 99%

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Modeling Lithospheric Thickness Along the Conjugate South Atlantic Passive Margins Implies Asymmetric Rift Initiation

et al. 2022

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The lithospheric architecture of passive margins is crucial for understanding the tectonic processes that caused the breakup of Gondwana. We highlight the evolution of the South Atlantic passive margins by a simple thermal lithosphere‐asthenosphere boundary (LAB) model based on onset and cessation of rifting, crustal thickness, and stretching factors. We simulate lithospheric thinning and select the LAB as the T = 1,330°C isotherm, which is calculated by 1D advection and diffusion. Stretching factors and margin geometry are adjusted to state‐of‐the‐art data sets, giving a thermal LAB model that is especially designed for the continental margins of the South Atlantic. Our LAB model shows distinct variations along the passive margins that are not imaged by global LAB models, indicating different rifting mechanisms. For example, we model up to 200 km deep lithosphere in the South American Santos Basin and shallow lithosphere less than 60 km in the Namibe Basin offshore Africa. These two conjugate basins reflect a strong asymmetry in LAB depth that resembles variations in margin width. In a Gondwana reconstruction, we discuss these patterns together with seismic velocity perturbations for the Central and Austral Segments of the margins. The shallow lithosphere in the Namibe Basin correlates with signatures of the Angola Dome, attributed to epeirogenic uplift in the Neogene, suggesting an additional component of post‐breakup lithospheric thinning.

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Section: Salado/southwest African Marginsupporting

confidence: 86%

Section: Methodsmentioning

confidence: 99%

Modeling Lithospheric Thickness Along the Conjugate South Atlantic Passive Margins Implies Asymmetric Rift Initiation

et al. 2022

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“…The final architecture of rifted margins is expected to be a consequence of both tectonic stretching and magmatic extension. Observed wide volcanic margins in the southern South Atlantic (Chauvet et al., 2021; Clerc et al., 2018) suggest that tectonic stretching might be dominating at these margins.…”

Section: Discussionmentioning

confidence: 99%

Magmatism at Passive Margins: Effects of Depth‐Dependent Wide Rifting and Lithospheric Counterflow

Lü

Huismans

2022

JGR Solid Earth

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Rifted passive margins exhibit a large variety in the timing, distribution, and amount of magmatism. The factors controlling magmatism during rifted margin formation, remain, however, incompletely understood, partly owing to the complex rifting styles. In this study, we use 2‐Dimensional numerical models to investigate the effects of depth‐dependent wide rifting and lithospheric counterflow on magmatism during rifted margin formation. Results show that a strong crust promotes narrow margins with a sharp transition to normal thickness oceanic crust whereas a weak crust promotes depth‐dependent wide rifting, with preferential removal of mantle lithosphere, leading to formation of wide margins with over‐thickened (>18 km) igneous crust in the distal margin. Counterflow of depleted lithospheric mantle, in contrast, may delay syn‐rift magmatism, and result in exhumed a‐magmatic continental mantle at narrow margins. The combination of wide rifting and lithospheric counterflow results in magma‐poor wide margins, with in some cases a transition to excess magmatic activity at breakup. Our models provide an explanation for the contrasting magmatic productivity at narrow and wide rifted margins, such as observed in the Lofoten‐Vesterålen, Newfoundland, Kwanza Basin, and Orange Basin margins.

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“…High resolution seismic reflection data have been widely used as a powerful tool for the analysis of basinal and crustal scale structures by both academic and industry practitioners (Chauvet et al., 2020; Gans et al., 1985; Lymer et al., 2019; Sapin et al., 2021; Unruh et al., 2008). In particular, increasing amounts of high‐quality, dee p 2D/3D seismic reflection data and deep drilling on passive margins provides unprecedented imaging of deep crustal levels (Clerc et al., 2015; Deng, McClay, & Bilal, 2020; Deng, Ren, et al., 2020; Muñoz‐Barrera et al., 2021; Sapin et al., 2021) together with insights into the composition and structure of crystalline basement that often appears acoustically transparent due to low impedance contrast and seismic wave attenuation at depth (Allmendinger et al., 1987; Brown, 1991; Fazlikhani et al., 2017; Lenhart et al., 2019; Phillips et al., 2016).…”

Section: Introductionmentioning

confidence: 99%

“…In particular, increasing amounts of high‐quality, dee p 2D/3D seismic reflection data and deep drilling on passive margins provides unprecedented imaging of deep crustal levels (Clerc et al., 2015; Deng, McClay, & Bilal, 2020; Deng, Ren, et al., 2020; Muñoz‐Barrera et al., 2021; Sapin et al., 2021) together with insights into the composition and structure of crystalline basement that often appears acoustically transparent due to low impedance contrast and seismic wave attenuation at depth (Allmendinger et al., 1987; Brown, 1991; Fazlikhani et al., 2017; Lenhart et al., 2019; Phillips et al., 2016). For instance, recent work using deep seismic reflection data in extensional terranes shows extensive igneous intrusion in the upper and lower crusts (Phillips et al., 2018; Wrona et al., 2019), inherited basement fabrics (Collanega et al., 2019; Fazlikhani et al., 2017; Osagiede et al., 2020; Phillips et al., 2016), and typically‐layered lower crust bounded at the base by a high‐amplitude Moho reflection and overlain by transparent upper crust with elevated geotherms (Allmendinger et al., 1987; Chauvet et al., 2020; Deng et al., 2020; Dong et al., 2020; Miller et al., 2005).…”

Section: Introductionmentioning

confidence: 99%

Low‐Angle Normal Faults on the NW Shelf of Australia: Implications for Late Paleozoic Rifting

Deng

McClay

Belgarde³

2022

Tectonics

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Late Paleozoic rifting of the NW Shelf of Australia formed a wide basin that fundamentally controlled the Mesozoic continental rifting and passive margin development; however, structural style associated with this extensional process remains poorly constrained. Here, we integrate high‐resolution seismic data with well data from the proximal domain of the NW Shelf to show that the Mermaid fault system in the eastern Dampier Sub‐basin is a large‐scale (∼80 km long), low‐angle (5–20°) normal fault with up to 10 km offset formed during the Late Paleozoic rifting. In its northern and southern domains, the Mermaid fault has a planar geometry with characteristic extensional structures. In its central domain, seaward‐dipping, domino‐style normal faults in the upper crust extend downward into a highly reflective seismic zone that arches upward to form an elliptical dome. Growth strata in the hangingwall half‐graben and footwall basement reflections indicate that the Mermaid fault initiated as a high‐angle normal fault and was rotated by footwall exhumation during extension. Intrabasement deformation along and below the Mermaid fault is characterized by moderate‐ to high‐amplitude, semi‐continuous seismic reflectors that are distinct from transparent reflection character in the overlying basement unit. Comparison of the Mermaid fault system to well‐studied detachment faults in metamorphic core complex settings reveals striking similarities. We therefore suggest that the Mermaid fault developed as part of a nascent metamorphic core complex with a warm to hot footwall that enabled middle‐lower crustal flow during the Late Paleozoic continental rifting, likely induced by southward subduction of the Paleo‐Tethys Ocean.

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Conjugate volcanic passive margins in the austral segment of the South Atlantic – Architecture and development

Cited by 46 publications

References 180 publications

Modeling Lithospheric Thickness Along the Conjugate South Atlantic Passive Margins Implies Asymmetric Rift Initiation

Modeling Lithospheric Thickness Along the Conjugate South Atlantic Passive Margins Implies Asymmetric Rift Initiation

Magmatism at Passive Margins: Effects of Depth‐Dependent Wide Rifting and Lithospheric Counterflow

Low‐Angle Normal Faults on the NW Shelf of Australia: Implications for Late Paleozoic Rifting

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