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Les interactions " tectonique et sédimentation " entre le front du prisme de la Barbade et le delta de l'Orénoque

Abstract : This manuscript summarises the research work performed during this thesis, which composed of several parts. The first part, consist of an interpretation of seismic data available documenting the Southern zone of the Prism of Barbados. The second part, consist of an analysis of the deformation (structural study and kinematics) and the last part contains the analysis of the underlying structures.
The approach used in this work attempts to analyse geological structures developed underwater and strongly dependent on sedimentation. These structures are formed in compressive and extensive domaines. We tried to define the genetic bonds between the nature and the architecture of the deposits and the geometry and the development of the structures, from data interpretation gathered at the time of CARAMBA survey, of the profiles of surveys VEN and AN, and two drillings located on the platform.
The sismostratigraphic analysis enabled us to identify seven seismic units which were located on the platform and in the southern part of the prism of Barbados, and to understand the chronology of the events and the kinematics of deformation. The nature of the deposits (seismic facies), their distribution, and their migration in the course of time appears closely associated with deformation. The development of a network of channels, shale-diapirism, and the localization of the erosion zones constituted other elements to specify the tectono-sedimentary evolution. This permited to identifie deux zones (1 & 2) from seismic facies analysis. Essentially, the majority of the erosion zones were identified in zone 1. These erosion zones are connected to the activation of the internal structures (very strong faults offset). The "chaotic" deposits (mud flows, slips in mass) which mark out fault 5, take part in erosion and feed sedimentation in north. The distribution of the channels is induced by the slopes hydrodynamism (foresets) of the Orenoque delta, and then is controled by the progressive deformation of acretionary prism. From structural study, we proposed that the deformation migrates towards southwest, at a rate of 0.7cm /yr after Pleistocene. In addition, we are noted that structures profonds are independent of the surface structures. According to the focal mechanisms, the underlying structures are opposed to those analyzed on the surface. The thickness of the continental crust tends to abroad towards the SE at the same time as the thickness of sedimentary cover tends to be reduced. The activity of the faults of the cretaceous platform played an important part in space creation for the sedimentary cover.
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Crelia Padron de Carillo. Les interactions " tectonique et sédimentation " entre le front du prisme de la Barbade et le delta de l'Orénoque. Sciences de la Terre. Université Joseph-Fourier - Grenoble I, 2007. Français. ⟨tel-00289762⟩

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