Patterns of bottom current flow deduced from dune asymmetries over the Gulf of Cadiz shelf (southwest Spain)

The analysis of dune-like morphologies on the Gulf of Cadiz continental she lf, using high-resolution seismic reflection profiles and sediment samples, reveals a well-defined distribution pattern controlled by the area's hydro dynamics. These bedforms are considered to be modern features from the Holo cene, and therefore they provide information about the bottom circulatory p atterns established over the continental shelf. Most of the submarine dunes have been identified over a shallow physiographic feature named the Barbat e High. The current flows that generate the bedform fields can be attribute d to a complex interaction of several hydrodynamic agents, in which the pro cess of current direction reversal related to the tidal cycle in the Strait s of Gibraltar seems to be involved. Eastward-oriented submarine dunes loca ted on the onshore zones of the inner shelf are generated by the Atlantic i nflow, which over these shallow zones is mainly orientated towards the east during high-tide conditions in the Straits of Gibraltar. Bedforms oriented westwards and west-northwestwards in the offshore zones indicate that a pr eviously undescribed flow occurs on the Gulf of Cadiz continental shelf. Th is flow is attributed to the influence of ebb tidal currents, which move pr eferentially towards the west over these zones. As a result of this complex bottom flow pattern, a clockwise sand transport pattern over the Barbate H igh is established. (C) 2000 Elsevier Science B.V. All rights reserved.