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STT-01 General contributions to tectonics and structural geology
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The tiburon and barracuda ridges linked with a recent N-S American plates convergence : Results from the Antiplac Marine survey
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Francine Benard, IFP (France)
Eric Deville, IFP (France)
Martin Patriat, Ifremer (France)
Eliane Le Drezen, Ifremer (France)
Benoit Loubrieu, Ifremer (France)
Estelle Thereau, Ifremer (France)
Marie Umber, Ifremer (France)
Walter Roest, Ifremer (France)
Roland Vially, IFP (France)
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The region situated between 14° and 17°20 N of latitude and 59°50 and 54°40 in longitude, east of the Barbados Accretionary Prism is classically described as the locus of diffuse deformation between the North and South American Plates. Marine geophysical data (multibeam and seismic lines) have been acquired in 2007 during the ANTIPLAC survey (UNCLOS project).
The seismic lines confirm the existence of deep sedimentary basins to the northern flank of the Barracuda Ridge and to the north of the Tiburon Ridge. The ages of the series expand from Late Cretaceous to Recent Time (see DSDP/OCP legs 78A, 110, 156, 171A, mainly the 543 and 672 wells). Seismic lines show that these structures result from different processes : folding involving the oceanic crust for the Barracuda ridge and mainly faulting at the Tiburon Ridge.
Numerous polyphased faults with tectonic inversion associated can be observed on the seismic lines. Correlatively, bathymetric scarps that can be observed straight above the structures testify for presently still active tectonic movements. These elements were gathered for reconstructing a map of the oceanic crust in this region.
The comparison between the structural arrangement of the oceanic crust obtained from this map and the main transform faults scheme deduced from magnetic anomalies shows that transform faults have been systematically reactivated and that they strongly impinge the texture of the region.
The occurrence of a widely distributed angular unconformity dated as Late Piocene-Pleistocene from the DSDP/ODP wells suggest the major deformation phase occurred at that time.
The Barracuda and Tiburon Ridges thus appear as structures inherited from the oceanic crust formation, i.e. highs linked with transform fault generation (megamullion for the Tiburon Ridge?), but their strong elevation at present time is largely due to the important reactivation due to the N-S convergence between the South and North American Plates.
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