FORMATION HISTORY AND OCEANOGRAPHIC CONTROL OF LATE HOLOCENE DEPOCENTERS IN THE NORTHERN GULF OF CADIZ, SOUTHERN SPAIN

Interplay between sediment supplied by several river systems, complex ocean currents and sea level have changed the depositional architecture of transgressive and highstand sediment depocenters (“mudbelts”) on the continental shelf in the northern Gulf of Cadiz (southern Spain). Previous investigations relied almost exclusively on subbottom echosounder data. With such a high demand of facies identification as a response to environmental changes during the late Holocene, this study utilizes an extensive seismo-acoustic data set and marine sediment cores to determine the formation history of confined shelf mud depocenters produced from the Guadalquivir River and surrounding sources. Through correlation of these data sets, volume estimates, transport pathways, centers of deposition and growth structure will be illustrated.

Sediment samples are analyzed for magnetic susceptibility, porosity, density, XRF element distribution scanning, grain size, and age. The combination of these basic approaches will lead to detailed insight of decadal through centennial changes in runoff and oceanographic forcing mechanisms.

The size of the study area is mainly confined to the northeastern area of the Gulf of Cadiz in water depths ranging from 15 to 200 m. Preliminary results depict a sediment rich environment with sediment thickness up to 20 m close to the Guadalquivir River prodelta at water depths of 15 to 50 m. Further from the prodelta, hard sub-bottom structures are covered by a 2 m thick sediment drape or more with up to 22 m of sediment filling between them. Close to the shelf edge, the internal reflection horizons pinch out. Preliminary interpretation of the seismo-acoustic data indicate evidence of an erosional boundary within the strata and areas containing alluvial paleo channels. An initial sediment budget estimate links continental discharge, sediment storage on the shelf and material export into the open ocean.

This project is a collaboration between Coastal Carolina University, MARUM/University of Bremen, and University of Granada as part of the CADISED (Cadiz Shelf Sediment Depocenters) project.