Raft tectonics in the Kwanza Basin, Angola

Duval, B.C.; Cramez, Carlos; Jackson, Martin P. A.

doi:10.1016/0264-8172(92)90050-o

Cited by 261 publications

(168 citation statements)

References 10 publications

Supporting

Mentioning

163

Contrasting

Unclassified

Order By: Relevance

“…Walgenwitz et al, 1992), either by the increase of sedimentation that induced an increased sedimentary load (e.g. Duval et al, 1992). Most likely, the multiple reactivations of gravitational tectonics during the Oligocene to Present are a response of the interplay of increased continental erosion driven by climate change and associated increased sedimentary load (Séranne, 1999) and of tectonic uplift (Lavier et al, 2001).…”

Section: Discussionmentioning

confidence: 99%

South Atlantic continental margins of Africa: A comparison of the tectonic vs climate interplay on the evolution of equatorial west Africa and SW Africa margins

Séranne¹,

Anka²

2005

Journal of African Earth Sciences

135

106

View full text Add to dashboard Cite

Africa displays a variety of continental margin structures, tectonic styles and sedimentary records. The comparative review of two representative segments: the equatorial western Africa and the SW Africa margins, helps in analysing the main controlling factors on the development of these margins. Early Cretaceous active rifting south of the Walvis Ridge resulted in the formation of the SW Africa volcanic margin that displays thick and wide intermediate igneous crust, adjacent to a thick unstretched continental crust. The non-volcanic mode of rifting north of the Walvis ridge, led to the formation of the equatorial western Africa margin, characterised by a wide zone of crustal stretching and thinning, and thick, extensive, synrift basins. Contrasting lithologies of the early post-rift (salt vs shale) determined the style of gravitational deformation, whilst periods of activity of the decollements were controlled by sedimentation rates. Regressive erosion across the prominent shoulder uplift of SW Africa accounts for high clastic sedimentation rate during Late Cretaceous to Eocene, while dominant carbonate production on equatorial western Africa shelf suggests very little erosion of a low hinterland. The early Oligocene long-term climate change had contrasted response in both margins. Emplacement of the voluminous terrigenous Congo deep-sea fan reflects increased erosion in equatorial Africa, under the influence of wet climate, whereas establishment of an arid climate over SW Africa induced a drastic decrease of denudation rate, and thus reduced sedimentation on the margin. Neogene emplacement of the African superswell beneath southern Africa was responsible for renewed onshore uplift on both margins, but it accelerated erosion only in the Congo catchment, due to wetter climatic conditions. Neogene high sedimentation rate reactivated gravitational tectonics that had remained quiescent since late Cretaceous.

show abstract

Section: Discussionmentioning

confidence: 99%

South Atlantic continental margins of Africa: A comparison of the tectonic vs climate interplay on the evolution of equatorial west Africa and SW Africa margins

Séranne¹,

Anka²

2005

Journal of African Earth Sciences

135

106

View full text Add to dashboard Cite

show abstract

“…One hypothesis is that the Aptian salt basins formed before Pangea broke up and sea-¯oor spreading began (Evans, 1978;Ojeda, 1982;Guardado, Gambo & Lucchesi, 1989;Duval, Cramez & Jackson, 1992;Davison, 1999). We refer to this scenario as``pre-breakup salt''.…”

Section: Aptian Salt Tectonicsmentioning

confidence: 99%

Role of subaerial volcanic rocks and mantle plumes in creation of South Atlantic margins: implications for salt tectonics and source rocks

Jackson¹,

Cramez

Fonck

2000

Marine and Petroleum Geology

Self Cite

175

147

View full text Add to dashboard Cite

Seaward-dipping re¯ectors (SDRs) represent¯ood basalts rapidly extruded during either rifting or initially subaerial sea-¯oor spreading. Evaporites can form on this basaltic proto-oceanic crust, as in the Afar Triangle today. Evidence for SDRs in South Atlantic deep-water regions comes from proximity to the uniquely large ParanaÂ ±Etendeka volcanic province onshore, the Tristan and Gough hot spots, drilled volcanic rocks, and seismic pro®les showing SDR provinces more than 100 km wide, as much as 7 km thick, and thousands of kilometers long. SDRs are clearest adjoining the Aptian salt basins. However, we speculate that SDRs are also present but seismically obscured below the salt basins. We argue that the conjugate Aptian salt basins are post-breakup, not pre-breakup; they were separated from the start by a mid-oceanic ridge; distal salt accumulated on proto-oceanic crust, not rift basins. This hypothesis is supported by: seismic stratigraphy and structure; magnetic anomalies; plate reconstructions; and hydrothermal potash evaporites. An important implication for exploration is that thick basalts, rather than rift-age source rocks, may underlie distal parts of the salt basins. 7

show abstract

“…For example, in sedimentary basins, salt can accommodate block rotations of overlying sedimentary strata (Fig. 6a), as described by Duval et al (1992) and Weijermars et al (1993).…”

Section: Folds Developed Above Normal Shear Zonesmentioning

confidence: 99%

“…Diapiric mobilisation of a buoyant ductile layer within denser overlying ductile layers during horizontal extension. (a) Interpretation of migrated seismic reflection profile from the Kwanza Basin, Angola (modified after Duval et al, 1992) where the positions of salt diapirs (black) within sedimentary rocks are controlled by normal faults. Diapiric emplacement of salt has aided rollover and rotation of hanging-wall strata.…”

Section: Extensional Forced Foldsmentioning

confidence: 99%

Mechanisms for folding of high-grade rocks in extensional tectonic settings

Harris

Koyi

Fossen

2002

Earth-Science Reviews

View full text Add to dashboard Cite

This review of structures developed in extensional high-grade terrains, combined with results of centrifuge analogue modelling, illustrates the range of fold styles and mechanisms for folding of amphibolite to granulite facies rocks during rifting or the collapse of a thrust-thickened orogen. Several extensional fold mechanisms (such as folding within detachment shear zones) are similar to those in contractional settings. The metamorphic P -T -t path, and not fold style or mode of formation, is therefore required to determine the tectonic setting in which some folds developed. Other mechanisms such as rollover above and folding between listric normal shear zones, and folding due to isostatic adjustments during crustal thinning, are unique to extensional tectonic settings. Several mechanisms for folding during crustal extension produce structures that could easily be misinterpreted as implying regional contraction and hence lead to errors in their tectonic interpretation. It is shown that isoclinal recumbent folds refolded by open, upright folds may develop during regional extension in the deep crust. Folds with a thrust sense of asymmetry can develop due to high shear strains within an extensional detachment, or from enhanced back-rotation of layers between normal shear zones. During back-rotation folding, layers rotated into the shortening field undergo further buckle folding, and all may rotate towards orthogonality to the maximum shortening direction. This mechanism explains the presence of many transposed folds, folds with axial planar pegmatites and folds with opposite vergence in extensional terrains. Examples of folds in high-grade rocks interpreted as forming during regional extension included in this paper are from the Grenville Province of Canada, Norwegian

show abstract

Raft tectonics in the Kwanza Basin, Angola

Cited by 261 publications

References 10 publications

South Atlantic continental margins of Africa: A comparison of the tectonic vs climate interplay on the evolution of equatorial west Africa and SW Africa margins

South Atlantic continental margins of Africa: A comparison of the tectonic vs climate interplay on the evolution of equatorial west Africa and SW Africa margins

Role of subaerial volcanic rocks and mantle plumes in creation of South Atlantic margins: implications for salt tectonics and source rocks

Mechanisms for folding of high-grade rocks in extensional tectonic settings

Contact Info

Product

Resources

About