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Les mouvements verticaux de la marge passive nord du golfe d'Aden (Dhofar) : causes profondes et superficielles

Abstract : « Margin » is a current word used defining the boundary of the continental crust. The breakup of the continental lithosphere in an extensive domain leads to the formation of two passive margins separated by an oceanic crust. These margins are rather common since they make most of the boundaries of the continental crust surrounding today's oceans. Moreover, they represent the ultimate step of the rift evolution: they keep the history of the deformation caused by the streching of the lithosphere. Therefore, the study of their structure and formation is needed to improve our understanding of lithospheric extension. Despite the large amount of available data along the passive margins and the increasing complexity of the models, some questions about the source of the margin vertical motions during the rifting have not been enterely answered yet. The eastern area of the gulf of Aden is a perfect laboratory where study passive margins. This young non-volcanic margin (oligo-miocene rifting) does not contain evaporites. Moreover, one can follow continuously evolution of a margin from its proximal part up to the oceanic dorsale. As the proximal part of the margin appears directly onland, it has been possible to carry out a sedimentologic study and to set-up a temporary network of seismic stations in 2003. In the frame of this Ph.D. thesis, the vertical motions of the northern margin of the Gulf of Aden have been studied by using two complementary approaches. The sedimentologic study on field allows us to get a complete history of the different vertical motions associated to the rifting. It reveals a burgidalian to langhian uplift step (~1My) that occurred during the oceanisation and/or during the first time of the ocean-continent transition. It shows an estimated intensity of about 700 m at least. A second uplift with a lower intensity (about few hundreds of meters) started at Pliocene and continues until today. The determination of the deep structure of the margin (from lithospheric to asthenospheric) has been performed by a teleseismic tomographic study. The deployment of 11 seismic stations from march 2003 to march 2004 enabled to record 284 teleseisms. Their analysis has revealed two main anomalies under dhofari margin: (1) a slow crustal anomaly, bounded to the 20 first km, linked to thick sediment deposits of Salalah bassin, (2) a slow asthenospheric anomaly located between 170 and 200 km depth approximately. By using model developed by Goes et al (2000), we demonstrated that this slow velocity might be linked to partial fusion phenomena. This area of light materials might be the source of the observed uplift in the sedimentary suite. However, the seismic imaging does not permit to evaluate the age of this mantellic material anomaly under the north margin of Dhofar. To widen the study to neighbouring zones and a complementary geologic and geophysic analysis are necessary to totally correlating or not these two observations.
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Contributor : Agnès Pointu <>
Submitted on : Sunday, August 22, 2010 - 1:18:28 PM
Last modification on : Wednesday, December 9, 2020 - 3:16:25 PM
Long-term archiving on: : Thursday, December 1, 2016 - 8:25:54 PM


  • HAL Id : tel-00510853, version 1


Agnès Pointu. Les mouvements verticaux de la marge passive nord du golfe d'Aden (Dhofar) : causes profondes et superficielles. Sciences de la Terre. Université Pierre et Marie Curie - Paris VI, 2007. Français. ⟨tel-00510853⟩



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