Rosas, F. M., Duarte, J. C., Terrinha, P., Valadares, V. and Matias, L. (2009) Morphotectonic characterization of major bathymetric lineaments in Gulf of Cadiz (Africa–Iberia plate boundary): Insights from analogue modelling experiments. Marine Geology, 261 (1-4). pp. 33-47. DOI 10.1016/j.margeo.2008.08.002.

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Abstract

New high-resolution multi-beam bathymetry data allowed the recognition of several bathymetric lineaments (ca. 100 km long, trending WNW–ESE) in seafloor sediments of the Gulf of Cadiz, offshore SW Iberia. The interpretation of multi-channel (MCS) profiles crosscutting these lineaments showed that they are controlled by underlying deep seated faults, which have endured a polyphase reactivation history. To get insights on the Recent tectonic evolution of these structures, we performed two sets of analogue modelling experiments, assuming: 1) right-lateral strike-slip basement faulting and coupled passive shearing affecting an overlying soft cover; and 2) low-angle transpressive deformation along a narrow shear band overlying the fault. Our results show a good correlation between the experimentally obtained structural patterns and the natural morphotectonic lineaments, allowing the use of some of the observed natural features as strain gauges. Based on this, we conclude that the study lineaments correspond to the bathymetric expression of ongoing dextral wrenching reactivation of WNW–ESE pre-existing faults, and we estimate the age of this tectonic reactivation as being ca. 1.8 Ma (i.e. form late Pliocene to Present day). These characteristics agree with the most recent kinematic models derived from geodetic observations, indicating that Present day convergence between Nubia and Iberia is subparallel to the newly identified lineaments and occurs at a 4 mm/yr rate.

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