1. Introduction

The processes responsible for recycling of lithospheric material back into the mantle are usually described in terms of subduction. The contribution of other processes such as lithospheric delamination (in the sense of) or convective removal continues to be controversial. Both delamination and subduction models have been proposed to explain the formation of many of the Neogene extensional basins located along the Alpine convergent zone between Africa and Eurasia. This study focuses on the Alboran Sea and the surrounding regions, located at the westernmost limit of this zone (Figure 1a). A variety of models have been proposed to explain the synchronous extension and contraction that occurred in the Alboran region and its surroundings during the Early Miocene despite the continued convergence of Africa and Iberia. Presently, delamination (in the sense of) or convective removal models are gaining popularity, but subduction models are also still being proposed.	Previous tomography studies that have imaged mantle structure beneath the western Mediterranean have found a pronounced high-velocity anomaly located beneath the Alboran Sea and southern Spain. However, the possible depth and lateral extent of the anomaly were not well defined with results interpreted both in terms of a subduction and delamination models . Blanco and Spakman used both local and teleseismic events extracted from the International Seismological Centre’s (ISC) catalog up to 1986. Seber et al. used more recent data (1989-1994) from the new Moroccan national network but did not use any local events or readings from Spanish stations. In this tomographic study, we take advantage of the expansion of seismic networks in Spain and Morocco and the large volume of new data that have been collected since these earlier studies and use all available data (author's picks made from Moroccan and Spanish waveforms merged with Spanish, Moroccan, ISC, and U.S. Geological Survey (USGS) bu1letins from 1964 to 1998) to investigate and accurately map the velocity structure of the region. The resulting velocity model is carefully evaluated using not only the standard synthetic tests and examination of the resolution matrix but also bootstrap resampling of the travel time data and shifting of model block boundaries to eliminate the dependence of the derived model on a particular parameterization. The implications of our results for previously proposed models are discussed and synthesized with observations from other recent studies into a model for the Neogene evolution of the Alboran Sea region.

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