Seismic refraction observations in the Transkei Basin and adjacent areas

Chetty, Paramesh; Green, R. W. E.

doi:10.1007/bf00310110

Cited by 31 publications

(15 citation statements)

References 20 publications

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“…In general, three totally different theories have been proposed to explain its development history. Tucholke et al (1981) suggested a continental provenance of the MozR based on a comparison of 1-D seismic refraction data from Hales & Nation (1973) and Chetty & Green (1977) with seismic refraction data from the Agulhas Plateau that was interpreted to be a continental fragment of South Africa. Dredge samples presented by Raillard (1990), Mougenot et al (1991), and Hartnady et al (1992) supported a continental origin of the MozR.…”

Section: G E O L O G I C a L A N D T E C T O N I C B A C Kg Ro U N Dmentioning

confidence: 99%

“…1) as Early Cretaceous, support the postulated timeframe of emplacement. A more than 22 km thick crust was identified for the MozR during a 1-D seismic refraction study (Hales & Nation 1973;Chetty & Green 1977). Chetty & Green (1977) concluded that the over-thickened crust lacks characteristic velocities of the continental basement and therefore a basement of continental crust was not strongly supported.…”

Section: G E O L O G I C a L A N D T E C T O N I C B A C Kg Ro U N Dmentioning

confidence: 99%

“…A more than 22 km thick crust was identified for the MozR during a 1-D seismic refraction study (Hales & Nation 1973;Chetty & Green 1977). Chetty & Green (1977) concluded that the over-thickened crust lacks characteristic velocities of the continental basement and therefore a basement of continental crust was not strongly supported. The interpretation of 2-D seismic refraction data showed that the MozR is characterized by over-thickened (16-22 km), seismically homogeneous, lower crustal units making up between half to two-thirds of the crustal column with P-wave velocities of more than 7.0 km s −1 (Gohl et al 2011).…”

Section: G E O L O G I C a L A N D T E C T O N I C B A C Kg Ro U N Dmentioning

confidence: 99%

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The Mozambique Ridge: a document of massive multistage magmatism

et al. 2016

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S U M M A R YThe Mozambique Ridge, a prominent basement high in the southwestern Indian Ocean, consists of four major geomorphological segments associated with numerous phases of volcanic activity in the Lower Cretaceous. The nature and origin of the Mozambique Ridge have been intensely debated with one hypothesis suggesting a Large Igneous Province origin. High-resolution seismic reflection data reveal a large number of extrusion centres with a random distribution throughout the southern Mozambique Ridge and the nearby Transkei Rise. Intrabasement reflections emerge from the extrusion centres and are interpreted to represent massive lava flow sequences. Such lava flow sequences are characteristic of eruptions leading to the formation of continental and oceanic flood basalt provinces, hence supporting a Large Igneous Province origin of the Mozambique Ridge. We observe evidence for widespread post-sedimentary magmatic activity that we correlate with a southward propagation of the East African Rift System. Based on our volumetric analysis of the southern Mozambique Ridge we infer a rapid sequential emplacement between ∼131 and ∼125 Ma, which is similar to the short formation periods of other Large Igneous Provinces like the Agulhas Plateau.

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Section: G E O L O G I C a L A N D T E C T O N I C B A C Kg Ro U N Dmentioning

confidence: 99%

Section: G E O L O G I C a L A N D T E C T O N I C B A C Kg Ro U N Dmentioning

confidence: 99%

Section: G E O L O G I C a L A N D T E C T O N I C B A C Kg Ro U N Dmentioning

confidence: 99%

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The Mozambique Ridge: a document of massive multistage magmatism

et al. 2016

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“…Hales & Nation (1973) reported that despite its depth to the Moho of about 22 km, the ridge is in isostatic equilibrium with the surrounding deep ocean basins, and thus proposed an oceanic origin for the Mozambique Ridge. Hints on a continental affinity of the ridge were provided by the interpretation of seismic refraction data as being representative for regional continental crust (Chetty & Green 1977). However, the data used in that study only have a maximum penetration depth of up to 5 km and Chetty & Green (1977) concluded that a basement of continental crust is not strongly supported from their point of view.…”

Section: Introductionmentioning

confidence: 99%

“…Hints on a continental affinity of the ridge were provided by the interpretation of seismic refraction data as being representative for regional continental crust (Chetty & Green 1977). However, the data used in that study only have a maximum penetration depth of up to 5 km and Chetty & Green (1977) concluded that a basement of continental crust is not strongly supported from their point of view. First direct samples from the basement of the Mozambique Ridge were taken during DSDP Leg 25, Site 249, on the central part of the ridge (Simpson et al 1974).…”

Section: Introductionmentioning

confidence: 99%

Advanced insights into magmatism and volcanism of the Mozambique Ridge and Mozambique Basin in the view of new potential field data

König¹,

Jokat

2010

Geophysical Journal International

123

106

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S U M M A R YA new plate tectonic model is presented which describes the emplacement of the Mozambique Ridge off southeast Africa as the result of long lasting volcanic activity (140-122 Ma) during the initial opening between Africa and Antarctica. Thus, an oceanic origin for the Mozambique Ridge is proposed. This model is based on a new and systematic high resolution magnetic anomaly data set acquired across the Mozambique Ridge and throughout the Mozambique Basin.Data from the Mozambique Basin allow the identification of Mesozoic magnetic anomalies from M0r to M26 (124.61-155.3 Ma) with previously unmatched accuracy. Small-scale fracture zones are recognized by offsets of magnetic anomalies in the westernmost part of the basin. Additionally, a bend in the major fracture zones 'F' and 'E' between M17r and M18n (142.84-144.04 Ma) and a recognized sinusoidal change in spreading direction with an amplitude of about 15 • indicate that the basin experienced several small scale changes in spreading direction through time. A maximum change in spreading direction to almost 0 • at around M11n (135.69 Ma) is followed by a short lived increase in spreading half rate from 23.5 km Ma −1 to about 27.5 km Ma −1 in the time frame from M10r to . We propose that this is related to the initial opening of the South Atlantic Ocean represented by the onset of seafloor spreading between the Falkland Plateau and Africa in the conjugate Georgia and Natal basins.Across the Mozambique Ridge, high amplitude magnetic anomalies at major structural boundaries suggest that the different plateaus of the ridge were formed at different times. A simple 2-D gravity and magnetic model for the ridge supports the hypothesis of multiple volcanic episodes which formed the ridge though long lasting volcanic activity between about 140 and 122 Ma. Together with new and verified rotation parameters from the Mozambique Basin and its conjugate, the Riiser-Larsen Sea, Antarctica, a series of plate tectonic reconstructions are presented which demonstrate when and how the different parts of the ridge evolved through time.

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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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Seismic refraction observations in the Transkei Basin and adjacent areas

Cited by 31 publications

References 20 publications

The Mozambique Ridge: a document of massive multistage magmatism

The Mozambique Ridge: a document of massive multistage magmatism

Advanced insights into magmatism and volcanism of the Mozambique Ridge and Mozambique Basin in the view of new potential field data

Reconstruction of the East Africa and Antarctica continental margins

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