Chapter 21 Neogene intraplate deformation of the caribbean plate at the beata ridge

Abstract

We have studied all the seismic profiles existing in the Beata ridge area, in addition to Seabeam maps, to determine the tectonics of this structure and its relationships with the adjacent areas. The basis of this work is the multichannel Casis seismic survey carried out by the R/V Nadir in 1992. These seismic lines are migrated and clearly show evidence of compression and transpression. The Presqu'île du Sud d'Hispaniola is an uplifted part of the volcanic igneous province that formed the Caribbean plate during Cretaceous time. This region was initially a part of the thick Beata volcanic plateau that collided with the central part of Hispaniola. A Seabeam map and single-channel seismic lines from the Seacarib 1 cruise show the active collision between the northeastern tip of Beata ridge and the western termination of the Muertos trough. Structural analysis indicates that the Muertos trough is an Eocene feature that has been reactivated in Recent times. The progressive emergence of the Muertos prism and its onland extension results from vertical stacking by thrusting of different parts of the prism. Several compressional structures can be seen on the eastern flank of the Beata ridge. The importance of these structures decreases systematically towards the south. One of these structures, the Taino ridge, was surveyed in detail during the Casis cruise. We describe reverse faults, pop-up and strike-slip faults. These tectonic features are compatible with a NE-SW compressive stress. A detailed site survey of the Aruba Gap was also performed during the Casis cruise. We show again compressional and wrench faults and an increase of the deformation towards the north. In contrast, we found no evidence of any compressional deformation on the western side of the Beata ridge. Here, steep NE-SW scarps shown by Seabeam maps, are predominant. We conclude from this tectonic framework that the Beata ridge has been deformed by compression and strike-slip faulting since the Early Miocene (23 Ma) by a NE-SW-oriented compressive stress. The Beata ridge is progressively uplifted from the south to the north up to the emergence of the Presqu'île du Sud. However, the Beata ridge is a Cretaceous plateau and initial topography must be taken into account. The Beata ridge is placed in the regional tectonic framework and we show that the compression of the ridge is probably connected to the Sinu subduction zone in Colombia. We distinguish between the Colombian and the Venezuelan microplates separated by the Beata compressional zone. The former drifts towards the northeast faster than the latter. From our structural analysis we deduce 0.9 cm/yr of relative motion between the two plates.