Abstract

The Alborán Sea basin contains one of the largest Neogene sedimentary accumulations in the western Mediterranean, distributed in several sub-basins separated by structural highs. Depth conversion and isopach maps of interpreted reflection seismic sections attest to the complexity of the basement architecture and basin infill.

Introduction

The Alborán Sea basin is located at the westernmost extreme of the Mediterranean Sea, closed to the Atlantic Ocean in the west at the Gibraltar Strait, and open to the east, where it passes into the Algerian Sea basin (Fig. 1). Its sedimentary sequence, of marine origin, is of Neogene age, the oldest sediments penetrated at well sites on the basin's northern margin being of upper Aquitanian/ lower Burdigalian age (Jurado and Comas, 1992). The sedimentary sequence is interrupted by several unconformities, of which the Messinian is the most prominent. The basin is underlain by thinned continental crust (Hatzfeld, 1976; Banda and Ansorge, 1980) which is the continuation of the metamorphosed Alborán domain units (Balanya and Garciá-Dueñas, 1987) that crop out on the mainlands of southern Spain and NW Morocco as the internal complexes of the Betic and Rif Cordilleras respectively. The thinned continental crust is host to volcanic centres that occur in basins and ridges (Galdeano et ai, 1974), but are present also in wells on the northern basin margin (Jurado and Comas, 1992). The basin is complex structurally, being segmented into sub-basins by prominent ridges that cross the basin.