Extension et sédimentation au paléozoïque terminal et au Mésozoïque dans le bassin de Majunga (Nord-Ouest de Madagascar) |
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| Authors: | Yolande Razafindrazaka Thogne Randriamananjara Alain Piqu Catherine Thouin Edgard Laville Jacques Malod Jean-Pierre Rhault |
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| Institution: | 1 Département de Géologie, Faculté des Sciences, Université d'Antananarivo, BP 906, Ankatso, Antananarivo, Madagascar;2 Département des Sciences de la Terre, Université de Bretagne occidentale, 29285 Brest Cedex, France;3 Département de Géologie, Université de Caen, 14032 Caen, France |
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| Abstract: | The Majunga Basin is located in the northwestern part of Madagascar with a N45–60°E trending axis. It was filled by almost exclusively continental Karoo Supergroup sediments, which are Permian to Early Jurassic in age, and by younger sequences, mainly marine, that were deposited from the Middle Jurassic to the present.The Karoo Basin geometry is deduced from the analysis of seismic sections. A central northeast trending horst is flanked by two sub-basins. Deposition of the Karoo sequences was controlled by these northeast trending faults. On the contrary, the Middle Jurassic to present sequences witness only a slight tilting of the basement towards the northwest.The development of the Majunga Basin includes, therefore, two successive stages. In the synrift episode, from Permian to Early Jurassic times, the sedimentation was syntectonic, controlled by synsedimentary faulting and the creation of a horst and graben extensive pattern. The postrift episode started during the Middle Jurassic.These two stages of the Majunga Basin development correspond to the geodynamic evolution recorded elsewhere in this part of the Gondwana. |
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