"Bottom current-controlled sedimentary processes. Case study in the Gulf of Cadiz middle slope" by Marga Garcia, Institut Andalús de Ciències de la Terra (IACT), will be held at room Sala d'Actes of Institut de Ciencies del Mar (ICM - www.icm.csic.es).
Bottom currents are presently regarded as a key process in building and shaping continental margins and basins, as they are responsible for the deposit of a wide range of sedimentary bodies, generically known as Contourites, but also for generating important erosive features that have been identifie d in oceans all around the world. Since the first studies on contourites during the 50’s a long way has been covered in their research, with the aid of technological advances on the seafloor exploration. Today, research on contourites is reaching a mature stage, especially in terms of their identification at a large scale, but there are still controversies especially regarding facies models and classifications and the relationship with the oceanographic processes that originate them. High-latitude regions, in particular, are the source area for the most important deep-water masses, that interact with the seafloor and develop some of the better studied contourite systems.. In polar margins contourite geomorphological and sedimentary features reveal key information about related glacial and glaciomarine processes that interact with their development. The talk will focus on the general geomorphological and sedimentary characteristics of contourite features by showing different examples of well-studied systems.
As a particular example, a morpho-sedimentary study of the central-north middle slope of the Gulf of Cadiz will be presented. Here, the Diego Cao channel separates the Bartolomeu Dias and Faro sheeted drift plateaus to the north of the Guadalquivir Bank margin uplift. A striking linear series of circular depressions occur parallel to the channel on the Bartolomeu Dias sheeted drift (western channel flank), while a remarkable amphitheater-shaped escarpment affects the channel eastern flank. Their morphological and high- and medium-resolution stratigraphic analysis allows inferring their origin as the result of a complex interplay between oceanographic (bottom currents), mass-wasting and tectonic processes. All features seem to have a common origin, related to an especially active tectonic phase during the Mid-Pleistocene, probably related to adjustments of the deep structural features. Since then, the action of the bottom currents and the local influence of structural processes have shaped the present-day topography. The Diego Cao channel is re-interpreted as a contourite moat associated to a complex mounded, separated drift that includes the circular depressions. They result from contourite deposition over the erosional surface originated by widespread mass-wasting events during the Mid-Pleistocene.