Évolution paléogéographique de la marge nord-ouest de l'Afrique du Cambrien à la fin du Carbonifère (du Maroc au Libéria)

1991 ◽  
Vol 28 (7) ◽  
pp. 1121-1130 ◽  
Author(s):  
Michel Villeneuve ◽  
Jean-Jacques Cornée
Keyword(s):  
West African ◽  
The West ◽  
Lower Paleozoic ◽  
West African Craton ◽  
Middle Cambrian ◽  
Early Devonian ◽  
Middle Ordovician ◽  
The North ◽  
Marine Platform ◽  
General Regression

Paleogeographic reconstructions of Paleozoic time are presented for the northwest margin of the West-African Craton. An extensional regime and a marine transgression were dominant during the Early Cambrian. During the Middle Cambrian, the Rokélides orogen was responsible for the sea regression to the south, while the proto-Atlantic opening was active to the north of the Reguibat shield. A large stable marine platform was present during Early and Middle Ordovician. A general regression and the formation of the West-African Inlandsis took place during the Late Ordovician. During Silurian time, this sea transgressed over most of the African platform. Incipient Hercynian deformations during the Early Devonian produced horsts and grabens in Morocco. At the end of the Devonian and the beginning of the Carboniferous, the sea was restricted to isolated basins and tectonic trenches. Collision between West Africa and North America during the Late Carboniferous transformed the Lower Paleozoic margin into an Hercynian orogenic belt, whose structure is controlled by the presence of crustal blocks, generated as early as the Cambrian, and probably reflecting, in turn, older Panafrican zones of weakness. [Translated by the Journal]

Paleomagnetism of some late Precambrian and lower Paleozoic sediments from L'Adrar de Mauritanie, West Africa

1978 ◽  
Vol 15 (2) ◽  
pp. 253-262 ◽  
Author(s):  
W. A. Morris ◽  
C. M. Carmichael
Keyword(s):  
West Africa ◽  
Early Phase ◽  
Late Phase ◽  
West African ◽  
Sedimentary Sequence ◽  
Chemical Cleaning ◽  
The West ◽  
Lower Paleozoic ◽  
West African Craton ◽  
Late Precambrian

Palaeomagnetic results are reported from three formations from the late Precambrian to lower Paleozoic sedimentary sequence of L'Adrar de Mauritanie, on the West African Craton. Each of the formations recorded complex magnetizations, the sequence of which could only be resolved after detailed thermal and chemical cleaning. Most of these complexities have arisen from post depositional hematite coating on both magnetic and non-magnetic grains. Formation I2 with a probable age of 1020 Ma records an early, presumably original remanence directed along D = 034°, I = +60° (α95 = 6°) and a later remanence D = 336°, I = +37° (α95 = 11°). Specimens from formations CO8 and CO10 (Cambro–Ordovician boundary) record a common late phase remanence at D = 128°, I = +24° (α95 = 8°). The CO10 early phase remanence is D = 033°, I = +61° (α95 = 7°), whereas the poorly isolated early phase remanence of CO8 approximates D = 060°, I = +51° (α95 = 20°).

Données nouvelles sur le protérozoïque inférieur du domaine nord-armoricain (France): age et signification

1980 ◽  
Vol 17 (4) ◽  
pp. 532-538 ◽  
Author(s):  
Bernard Auvray ◽  
René Charlot ◽  
Philippe Vidal
Keyword(s):  
West African ◽  
The Other ◽  
The West ◽  
West African Craton ◽  
Northern Margin ◽  
The North ◽  
Upper Proterozoic ◽  
Lower Proterozoic ◽  
Proterozoic Basement ◽  
Armorican Massif

Orthogneisses from the Tregor area of the North Armorican Massif have been dated using the U/Pb method on zircons. Ages of between 1.8 and 2.0 Ga have been obtained, thus significantly extending the known size of the Lower Proterozoic basement in this area. It is argued that the presence of such a substantial area of basement is a further argument for an Upper Proterozoic (Brioverian) south-dipping subduction zone which was located to the north of the Armorican Massif. On the other hand, the similarities between the North Armorican block and the northern margin of the West African craton during the Proterozoic are emphasized.

Detrital pyrope garnets from the El Kseibat area, Algeria: A glimpse into the lithospheric mantle beneath the north-eastern edge of the West African Craton

2012 ◽  
Vol 63 ◽  
pp. 1-11 ◽  
Author(s):  
Mohammed Kahoui ◽  
Felix V. Kaminsky ◽  
William L. Griffin ◽  
Elena Belousova ◽  
Yamina Mahdjoub ◽  
...  
Keyword(s):  
Lithospheric Mantle ◽  
West African ◽  
The West ◽  
West African Craton ◽  
The North ◽  
North Eastern ◽  
Eastern Edge

Étude géologique du socle ante-mésozoique au nord du Massif Armoricain: limites et structures de la Domnonée

1975 ◽  
Vol 279 (1288) ◽  
pp. 123-135 ◽  
Keyword(s):  
Seismic Data ◽  
Lower Cambrian ◽  
The South ◽  
The West ◽  
Middle Cambrian ◽  
Middle Ordovician ◽  
Fundamental Structure ◽  
The North ◽  
Caledonian Orogeny

The study of samples taken on the bottom of the sea north of the Massif Armoricain, and the geological, magnetic, gravimetric and seismic data collected on land and at sea, confirms that this region is characterized by: (1) a series of horsts where fragments of Pentevrian and Cadomian orogenies outcrops; (2) gullies, or synclines, of Palaeozoic terrain. The separation of the horsts is the result of tectonic shearing which developed during the Ordovician, Carboniferous and Triassic ages. The Cadomian chain, which constituted the fundamental structure of the region, was broken up very early and is no longer recognizable. In the west, traces of this chain seem to have lasted until the Llanvirnian. In the east, the uplands, which were probably less harsh, were levelled before the start of the lower Cambrian age. A general upwarp of the eastern part between the middle Cambrian and the middle Ordovician could correspond to a reaction to the Caledonian orogeny. The northern part of the Alassif Armoricain had little part in the Hercynian paroxysm, however, this period witnessed an important tangential tectonism, the horsts riding over the edges of the synclines. The western formations show more marked structures than the eastern formations. The area which has been studied largely corresponds to the Domnonean domain, a puzzle of horsts and grabens. The Domnonea is itself a large horst, limited to the north by thick Palaeozoic sequences and to the south by the central Armorican zone and the Mancellian domain.

Variscan deformation at the northern border of the West African Craton, eastern Anti-Atlas, Morocco: compression of a mosaic of tilted blocks

2007 ◽  
Vol 178 (5) ◽  
pp. 343-352 ◽  
Author(s):  
Youssef Raddi ◽  
Lahssen Baidder ◽  
Mohamed Tahiri ◽  
André Michard
Keyword(s):  
Regional Scale ◽  
West African ◽  
Passive Margin ◽  
Fold Belt ◽  
The West ◽  
West African Craton ◽  
Margin Setting ◽  
The North ◽  
Atlas Mountains ◽  
Northern Border

Abstract North of the Saharan cratonic domain, the Anti-Atlas mountains correspond to the foreland, external fold belt of the Variscan orogen which extends in the Meseta block to the north, and Mauritanides to the southwest. The Anti-Atlas was uplifted during the Mesozoic-Cenozoic, and display several basement culminations (“boutonnières”) amidst the folded Palaeozoic cover. Recent studies in western Anti-Atlas emphasized the basement implication in the shortening process (thick skinned structure). Hereafter we investigate the cover-basement relations in eastern Anti-Atlas south of the Ougnat culmination, based on mapping at scale 1:50,000. The Palaeozoic sequence is much thinner than in the west, and the décollement levels are less important. Flexural slip folds are concentrated along the faults (en échelon folds) and within some rhombic domains crushed between major faults (e.g. Angal-Gherghiz Lozenge), whereas other areas are monoclinal. The main shortening direction deduced from the fold axes trend is directed ~N045°E as in the Ougarta range further to SE. At a regional scale, this shortening direction interferes with a N-S trending one. A sketch map of the top of the basement makes visible a mosaic of S- to SE-ward tilted blocks. The faults between these blocks are inherited from paleofaults which formed during extensional events during the Cambrian, late Ordovician, and (mainly) Middle-Late Devonian. The paleofault array is indicative of a proximal passive margin setting at the northern border of the metacratonic domain. The fault inversion and their dominant strike-slip throw occurred during a late Variscan (Stephanian-Permian) compression event, postdating the NNW-SSE collision of the Meseta block.

The magmatic evolution at the Moroccan outboard of the West African craton between the Late Neoproterozoic and the Early Palaeozoic

2008 ◽  
Vol 297 (1) ◽  
pp. 329-343 ◽  
Author(s):  
H. Ezzouhairi ◽  
M. L. Ribeiro ◽  
N. Ait Ayad ◽  
M. E. Moreira ◽  
A. Charif ◽  
...  
Keyword(s):  
West African ◽  
Magmatic Evolution ◽  
The West ◽  
West African Craton ◽  
Late Neoproterozoic ◽  
Early Palaeozoic

Paleomagnetism of the ~860 Ma Manso dyke swarm, West Africa: implications for the assembly of Rodinia

2021 ◽  
Author(s):  
Paul Yves Jean Antonio ◽  
Lenka Baratoux ◽  
Ricardo Ivan Ferreira Trindade ◽  
Sonia Rousse ◽  
Anani Ayite ◽  
...  
Keyword(s):  
West Africa ◽  
West African ◽  
Dyke Swarm ◽  
Jigsaw Puzzle ◽  
The West ◽  
West African Craton ◽  
Contact Test ◽  
Fine Grained ◽  
Paleomagnetic Pole ◽  
Coarse To Fine

<p>The West African Craton (WAC) is one of the major cratons in the Rodinia jigsaw puzzle (~1000–750 Ma). In the Rodinian models, the position of West Africa is mainly constrained by the assumption that it had been a partner of Amazonia since the Paleoproterozoic. Unfortunately, no paleomagnetic data are available for these cratons when the Rodina supercontinent is considered tectonically stable (~1000-750 Ma). Thus, every new reliable paleomagnetic pole for the West African Craton during the Neoproterozoic times is of paramount importance to constrain its position and testing the Rodinia models. In this study we present a combined paleomagnetic and geochronological investigation for the Manso dyke swarm in the Leo-Man Shield, southern West Africa (Ghana). The ~860 Ma emplacement age for the NNW-trending Manso dykes is thus well-constrained by two new U-Pb apatite ages of 857.2 ± 8.5 Ma and 855 ± 16 Ma, in agreement with baddeleyite data. Remanence of these coarse-to-fine grained dolerite dykes is carried by stable single to pseudo-single domain (SD-PSD) magnetite. A positive baked-contact test, associated to a positive reversal test (Class-C), support the primary remanence obtained for these dykes (13 sites). Moreover, our new paleomagnetic dataset satisfy all the seven R-criteria (R=7). The ~860 Ma Manso pole can thus be considered as the first key Tonian paleomagnetic pole for West Africa. We propose that the West Africa-Baltica-Amazonia-Congo-São Francisco were associated in a long-lived WABAMGO juxtaposition (~1100–800 Ma).</p><p><strong>Keywords:</strong> West Africa, Neoproterozoic, Tonian, Rodinia, paleomagnetism.</p><p> </p>

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