A regional gravity study of the West African rift system in Nigeria and Cameroon and its tectonic interpretation

Fairhead, J. D.; Okereke, C.S.

doi:10.1016/0040-1951(87)90084-9

Cited by 125 publications

(84 citation statements)

References 29 publications

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“…Evidence from the Precambrian basement indicates -1 km of uplift at the onset of volcanism, with deformation along N70~ normal and ENE-WSW strike-slip faults (Moreau et al 1987). Seismic refraction data (Stuart et al 1985) and documentation of gravity lows (Fairhead and Okereke 1987;Poudjom Djomani et al 1997) indicate that the Cameroon Line has lithosphere and crust thicknesses of ~80-120 and -20-30 km, respectively. The crust along the Cameroon Line is -10 km thinner compared with the crust in surrounding areas, whereas the lithosphere is as much as ~40 km thinner (Poudjom Djomani et al 1997).…”

Section: Geological Frameworkmentioning

confidence: 94%

The 1999 and 2000 eruptions of Mount Cameroon: eruption behaviour and petrochemistry of lava

et al. 2003

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Mount Cameroon (4,095 m high and with a volume of -1,200 km 3) is one of the most active volcanoes in Africa, having erupted seven times in the last 100 years. This stratovolcano of basanite and hawaiite lavas has an elliptical shape, with over a hundred cones around its flanks and summit region aligned parallel to its NE-SW-trending long axis. The 1999 (28 March-22 April) eruption was restricted to two sites: -2,650 m (site 1) and -1,500 m (site 2). Similarly, in the eruption in 2000 (28 May-19 June), activity occurred at two sites: -4,095 m (site 1) and ~3,300 m (site 2). During both eruptions, the higher vents were more explosive, with strombolian activity, while the lower vents were more effusive. Accordingly, most of the lava (-8x107 m 3 in 1999 and -6x106 m 3 in 2000) was emitted from the lower sites. The 1999-2000 lavas are predominantly basanites with low Ni (5-79 ppm), Cr (40-161 ppm) and mg numbers (34--40). Olivine (Fo77_85 , phenocrysts and Editorial responsibility: J. McPhie

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Section: Geological Frameworkmentioning

confidence: 94%

The 1999 and 2000 eruptions of Mount Cameroon: eruption behaviour and petrochemistry of lava

et al. 2003

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“…Pernambuco lineament in Brazil [e.g., Burke et al, 1971;Browne and Fairhead, 1983;Dorbath et al, 1986;Fairhead and Okereke, 1987;Fairhead and Binks, 1991].…”

Section: 1002/2014jb011580mentioning

confidence: 99%

Lithospheric instability and the source of the Cameroon Volcanic Line: Evidence from Rayleigh wave phase velocity tomography

et al. 2015

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The Cameroon Volcanic Line (CVL) is a 1800 km long volcanic chain, extending SW-NE from the Gulf of Guinea into Central Africa, that lacks the typical age progression exhibited by hot spot-related volcanic tracks. This study investigates the upper mantle seismic structure beneath the CVL and surrounding regions to constrain the origin of volcanic lines that are poorly described by the classic plume model. Rayleigh wave phase velocities are measured at periods from 20 to 182 s following the two-plane wave methodology, using data from the Cameroon Seismic Experiment, which consists of 32 broadband stations deployed between 2005 and 2007. These phase velocities are then inverted to build a model of shear wave velocity structure in the upper mantle beneath the CVL. Results show that phase velocities beneath the CVL are reduced at all periods, with average velocities beneath the CVL deviating more than -2% from the regional average and +4% beneath the Congo Craton. This distinction is observed for all periods but is less pronounced for the longest periods measured. Inversion for shear wave velocity structure indicates a tabular low velocity anomaly directly beneath the CVL at depths of 50 to at least 200 km and a sharp vertical boundary with faster velocities beneath the Congo Craton. These observations demonstrate widespread infiltration or erosion of the continental lithosphere beneath the CVL, most likely caused by mantle upwelling associated with edge-flow convection driven by the Congo Craton or by lithospheric instabilities that develop due to the nearby edge of the African continent.

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“…Most of the structures in the study area show vertical/subvertical dips in the sedimentary terrain than in the Basement Complex region. The deep seated structures in the sedimentary terrain were presumed to be controlled by the continental extension of the transform faults associated with Proto-Atlantic equatorial shear zone (Fairhead and Okereke, 1987). The continued movement of some basement blocks along the weak zones would have resulted in fracturing and the formation of faults, fold and stratigraphic features in the overlying sediments.…”

Section: Resultsmentioning

confidence: 99%

Evidence of basement controlled faulting of cretaceous strata in the Middle Benue Trough, Nigeria from lineament analysis of gravity data

Awoyemi¹,

Hammed²,

Falade³

et al. 2017

Ife Journal of Science

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The Bouguer anomaly map of part of the Middle Benue Trough, Nigeria, was used to investigate the genetic relationship between the basement and intra-sedimentary structures in the study area. This was with a view to establishing the evidence of possible basement controlled faulting of the Cretaceous strata. Regional-residual separation of the anomalies was carried out to produce the gravity maps associated with crustal masses at deep and intermediate depth layers. The derived maps were further processed to produce Horizontal Gradient Magnitude (HGM) maps that were used to infer deep seated structures and structures existing at intermediate depth layer of the study area. HGM maxima of the anomaly at various altitudes of upward continuation were used to highlight the locations and dip directions of subsurface structures as controlled from deep to shallow zones. The results of this study showed that the structures at different depth layers dominantly trend in the same direction (N-S, NNE-SSW and NE-SW) and that the deep seated faults reflect structurally in the overlying sedimentary column. It was therefore concluded that basement faulting might have influenced the structures in the overlying sedimentary rocks.

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A regional gravity study of the West African rift system in Nigeria and Cameroon and its tectonic interpretation

Cited by 125 publications

References 29 publications

The 1999 and 2000 eruptions of Mount Cameroon: eruption behaviour and petrochemistry of lava

The 1999 and 2000 eruptions of Mount Cameroon: eruption behaviour and petrochemistry of lava

Lithospheric instability and the source of the Cameroon Volcanic Line: Evidence from Rayleigh wave phase velocity tomography

Evidence of basement controlled faulting of cretaceous strata in the Middle Benue Trough, Nigeria from lineament analysis of gravity data

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