The structure of the lower crust at the Argentine continental margin, South Atlantic at 44°S

Schnabel, M.; Franke, Dieter; Engels, M.; Hinz, K.; Neben, S.; Damm, Volkmar; Grassmann, Stefan; Pelliza, Hugo; Santos, Paulo Ricardo dos

doi:10.1016/j.tecto.2008.01.019

Cited by 54 publications

(85 citation statements)

References 30 publications

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“…On the South American margin, Schnabel et al (2008) identified HVLC underlying SDRs along a traverse of the Argentina margin at latitude 44 • S ( Fig. 1 line 2).…”

Section: Existing Profiles and Interpretationmentioning

confidence: 97%

“…The presence of HVLC bodies along the South Atlantic rifted margins is well established from seismic and gravity studies (e.g., Bauer et al, 2000;Blaich et al, 2011;Franke, 2013;Franke et al, 2010;Maystrenko et al, 2013;Schnabel et al, 2008), but they have not yet been studied for areal extent and rifting process determination. That is the purpose of the study reported here.…”

Section: K Becker Et Al: Asymmetry Of High-velocity Lower Crust On mentioning

confidence: 99%

“…3). Schnabel et al (2008) tested the velocity depth ambiguity for a similar data set on the Argentine margin (line 2) which has a comparable acquisition and processing procedure as compared to lines 1 and 3. Variations of the weighting parameter had no significant influence on the depth of the Moho.…”

Section: Seismic Velocitymentioning

confidence: 99%

“…Previously, the HVLC was interpreted as a combination of magmatic underplating and heavily intruded crust (Schnabel et al, 2008;Hirsch et al, 2009). A low-velocity gradient above the HVLC on line 2 suggests intruded continental crust above the HVLC.…”

Section: Origin Of the Hvlc Bodiesmentioning

confidence: 99%

“…A low-velocity gradient above the HVLC on line 2 suggests intruded continental crust above the HVLC. Densities exceeding normal crustal values argue for intruded continental crust above the HVLC in the central lines 2, 6 and 7 (Schinkel, 2006;Hirsch et al, 2009;Schnabel et al, 2008), which implies the HVLC being intruded crust.…”

Section: Origin Of the Hvlc Bodiesmentioning

confidence: 99%

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Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup

et al. 2014

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Abstract. High-velocity lower crust (HVLC) and seawarddipping reflector (SDR) sequences are typical features of volcanic rifted margins. However, the nature and origin of HVLC is under discussion. Here we provide a comprehensive analysis of deep crustal structures in the southern segment of the South Atlantic and an assessment of HVLC along the margins. Two new seismic refraction lines off South America fill a gap in the data coverage and together with five existing velocity models allow for a detailed investigation of the lower crustal properties on both margins. An important finding is the major asymmetry in volumes of HVLC on the conjugate margins. The seismic refraction lines across the South African margin reveal cross-sectional areas of HVLC 4 times larger than at the South American margin, a finding that is opposite to the asymmetric distribution of the flood basalts in the Paraná-Etendeka Large Igneous Province. Also, the position of the HVLC with respect to the SDR sequences varies consistently along both margins. Close to the Falkland-Agulhas Fracture Zone in the south, a small body of HVLC is not accompanied by SDRs. In the central portion of both margins, the HVLC is below the inner SDR wedges while in the northern area, closer to the Rio Grande Rise-Walvis Ridge, large volumes of HVLC extend far seaward of the inner SDRs.This challenges the concept of a simple extrusive/intrusive relationship between SDR sequences and HVLC, and it provides evidence for formation of the HVLC at different times during the rifting and breakup process. We suggest that the drastically different HVLC volumes are caused by asymmetric rifting in a simple-shear-dominated extension.

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“…On the South American margin, Schnabel et al (2008) identified HVLC underlying SDRs along a traverse of the Argentina margin at latitude 44 • S ( Fig. 1 line 2).…”

Section: Existing Profiles and Interpretationmentioning

confidence: 97%

Section: K Becker Et Al: Asymmetry Of High-velocity Lower Crust On mentioning

confidence: 99%

Section: Seismic Velocitymentioning

confidence: 99%

Section: Origin Of the Hvlc Bodiesmentioning

confidence: 99%

Section: Origin Of the Hvlc Bodiesmentioning

confidence: 99%

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Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup

et al. 2014

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Fault‐controlled lithospheric detachment of the volcanic southern South Atlantic rift

Becker

Tanner

Franke

et al. 2016

Geochem Geophys Geosyst

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We present structural models of two exemplary conjugate seismic lines of the southernmost South Atlantic margins to examine their initial evolution, especially the seaward-dipping reflectors (SDRs). Modeling illustrates the different structure and inclination angles of the SDRs, which therefore require different subsidence histories. Since typical symmetrical subsidence models are not applicable, we suggest a model with a westward-dipping detachment fault that offsets the SDRs on the South American margin and we speculate on passively subsided SDRs on the South African margin. We propose a simple-shear rifting mechanism to explain the initial break-up of the South Atlantic.

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Reconstruction of the East Africa and Antarctica continental margins

et al. 2016

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The Early Jurassic separation of Antarctica from Africa plays an important role in our understanding of the dispersal of Gondwana and Pangea. Previous reconstruction models contain overlaps and gaps in the restored margins that reflect difficulties in accurately delineating the continent‐ocean‐boundary (COB) and determining the amount and distribution of extended continental crust. This study focuses on the evolution of the African margin adjacent to the Mozambique Basin and the conjugate Antarctic margin near the Riiser‐Larsen Sea. Satellite‐derived gravity data have been used to trace the orientations and landward limits of fracture zones. A 3‐D gravity inversion has produced a crustal thickness model that reliably quantifies the extent and amount of stretched crust. Crustal thicknesses together with fracture zone terminations reveal COBs that are significantly closer to the African and Antarctic coasts than previously recognized. Correlation of fracture zone azimuths and identified COBs suggests Antarctica began drifting away from Africa at approximately 171 Ma in a roughly SSE direction. An areal‐balancing method has been used to restore the crust to a uniform prerift thickness so as to perform a nonrigid reconstruction for both nonvolcanic and volcanic margins. Both margins reveal a trend of increasing extension from east to west. Our results suggest Africa underwent extension of 60–120 km, while Antarctic crust was stretched by 105–180 km. Various models tested to determine the direction of extension during rifting suggest that Antarctica moved away from Africa in a WNW‐ESE direction during the period between 184 and 171 Ma prior to the onset of seafloor spreading.

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The structure of the lower crust at the Argentine continental margin, South Atlantic at 44°S

Cited by 54 publications

References 30 publications

Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup

Asymmetry of high-velocity lower crust on the South Atlantic rifted margins and implications for the interplay of magmatism and tectonics in continental breakup

Fault‐controlled lithospheric detachment of the volcanic southern South Atlantic rift

Reconstruction of the East Africa and Antarctica continental margins

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