768 The Leading Edge July 2012 SPECIAL SECTION: M e d i t e r r a n e a n r e g i o n Recent shale tectonics and basin evolution of the NW Alboran Sea T his contribution is intended to show some of the most recent, eventually active, shale structures developed in the northwestern margin of the Alboran Sea in the western Mediterranean. Most marine geophysical data used for this study are from surveys conducted by ConocoPhillips in 2000 and 2001 in the Alboran Sea. his company explored the western sector of this basin, both in Spanish and Moroccan waters. It acquired a comprehensive data set, including a complete mosaic of sea-floor multibeam bathymetry with the associated sub-bottom high-resolution profiles, and a dense network of 2D multichannel seismic reflection profiles. hese surveys provide a significant amount of new marine geophysical data, which increase the previous knowledge of the structure and characteristics of the westernmost Mediterranean region. We focus our research on the most recent structures in the NW Alboran Sea (Figures 1 and 2). In particular, we illustrate the shallow structure of some shale diapirs developed in this basin, documenting also how shale and mud-rich sediments have been recently extruded to form active mud volcanoes that can be seen on the sea floor. his contribution completes our reconstruction of the shale tectonic processes in the area (Soto et al., 2010), because it focuses on the processes that occurred since the Messinian event (i.e., during the last 5.1 Ma). During the Pliocene-to-Quaternary period (P-Q), several important JUAN I. SOTO, University of Granada FERMIN FERNÁNDEZ-IBÁÑEZ, GeoMechanics International ASRAR R. TALUKDER, CSIRO Earth Science and Resource Engineering sedimentary processes occurred in this margin, accompanying the most recent uplift of the nearby Betic mountain ranges. P-Q basin subsidence in the Alboran Sea was accompanied by margin uplift and erosion. Introduction he Alboran Sea Basin, in the westernmost Mediterranean, has been formed since the early Miocene by severe lithosphere thinning and subsidence in a context of plate convergence between the African and Eurasian plates (e.g., Comas et al., 1999). he arcuate mountain belt formed by the Betics (southern Iberia) and Rif (northern Africa) chains, collectively known as the Gibraltar Arc, surrounds this basin and represents the westernmost termination of the Alpine orogen in the Mediter- ranean (Figure 1 and 2). he Gibraltar Arc involves different crustal domains: (1) the fold and thrust belt of the external Betics and Rif; (2) the Flysch Units comprising sediments that originally occupied an intermediate trough over a prob- able oceanic crust; and (3) the Alboran Domain, formed by a thrust-stack of three metamorphic complexes, which con- stitutes the Internal Zones and the floor of the Alboran Sea Basin. he Alboran Sea itself has three main sub-basins (Figure 2): the West Alboran Basin (WAB), the East Alboran Basin Figure 1. Topography of the westernmost Mediterranean. AB = Algerian Basin. Downloaded 12 Oct 2012 to 84.79.196.80. Redistribution subject to SEG license or copyright; see Terms of Use at http://segdl.org/