Abstract
Abstract. Progress in the understanding and dating of the sedimentary record of the Alboran Basin allows us to propose a model of its tectonic evolution since the Pliocene. After a period of extension, the Alboran Basin underwent a progressive tectonic inversion starting around 9–7.5 Ma. The Alboran Ridge is a NE–SW transpressive structure accommodating the shortening in the basin. We mapped its southwestern termination, a Pliocene rhombic structure exhibiting series of folds and thrusts. The active Al-Idrissi Fault zone (AIF) is a Pleistocene strike-slip structure trending NNE–SSW. The AIF crosses the Alboran Ridge and connects to the transtensive Nekor Basin and the Nekor Fault to the south. In the Moroccan shelf and at the edge of a submerged volcano we dated the inception of the local subsidence at 1.81–1.12 Ma. The subsidence marks the propagation of the AIF toward the Nekor Basin. Pliocene thrusts and folds and Quaternary transtension appear at first sight to act at different tectonic periods but reflect the long-term evolution of a transpressive system. Despite the constant direction of Africa–Eurasia convergence since 6 Ma, along the southern margin of the Alboran Basin, the Pliocene–Quaternary compression evolves from transpressive to transtensive along the AIF and the Nekor Basin. This system reflects the logical evolution of the deformation of the Alboran Basin under the indentation of the African lithosphere.
Highlights
The Pliocene–Quaternary tectonics of the Alboran Basin and its margins show the superposition of transpressive and transtensive structures that have been attributed to different mechanisms including changes in far-field stress, slab rollback and mantle delamination (Calvert et al, 2000; Gutscher et al, 2002; Martínez-García et al, 2013, 2017; Petit et al, 2015; Thurner et al, 2014)
Based on the seismic stratigraphic interpretation of our database and on a regional synthesis of structural data, we propose that the structural evolution of the Alboran Basin and its southern margin reflects a Pleistocene change in tectonic style
The Pliocene–Quaternary sedimentary sequence of the southern Alboran margin has been divided into three Pliocene (Pl1, Pl2 and Pl3) and four Quaternary
Summary
The Pliocene–Quaternary tectonics of the Alboran Basin and its margins show the superposition of transpressive and transtensive structures that have been attributed to different mechanisms including changes in far-field stress, slab rollback and mantle delamination (Calvert et al, 2000; Gutscher et al, 2002; Martínez-García et al, 2013, 2017; Petit et al, 2015; Thurner et al, 2014). GPS velocities define an Alboran tectonic domain in between the African and Iberian rigid blocks (Fig. 1) (Neres et al, 2016; Palano et al, 2013, 2015). Based on the seismicity (Fig. 2), a present-day diffuse plate boundary between Africa and Eurasia was proposed in the Alboran Basin and the Betic–Rif belt (Bird, 2003; Neres et al, 2016; Palano et al, 2015). M. Lafosse et al.: Pliocene-Quaternary tectonics of the Alboran Basin
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