Large-scale sediment bodies and superimposed bedforms on the continental shelf close to the Strait of Gibraltar: interplay of complex oceanographic conditions and physiographic constraints



A previously unknown field of large-scale sedimentary bodies has been mapped and studied on the continental shelf off the Cape Trafalgar near the Strait of Gibraltar with particular emphasis on the relationship between large-scale sediment bodies and the superimposed bedforms. This study is based on a grid of 975 km of high-resolution seismic profiles collected at water depths ranging between 15 and 60 m.

High variability of large-scale sedimentary bodies is attributed to the complex interaction of hydrodynamic agents. The most prominent sedimentary features are sand banks and ridges that indicate long-term southwest and southward-directed sediment transport patterns, possibly due to the interplay of two dominant current systems flowing southward and westward. These sediment bodies evolve laterally to distinct external geometries, such as sand shoals in shallow water and sand sheets in the vicinity of larger sand banks that indicate moderate current velocities. In addition, pre-existing physiography is considered to play a role in the generation of certain sediment bodies, developed over inclined surfaces or confined laterally by elevations.

Relationships between superimposed bedforms (mostly very large dunes) and underlying sediment bodies vary across the study area. Most superimposed bedforms occur over the complex mosaic of sediment banks and sheets, suggesting the interaction of several high-energy currents with different directions, such as tidal and/or wind-driven currents. Copyright © 2010 John Wiley & Sons, Ltd.