Late Quaternary seismic facies of the Gulf of Cadiz Spanish margin: depositional processes influenced by sea-level change and tectonic controls

Seismic facies and Quaternary depositional systems of the Gulf of Cadiz hav e been characterized by means of high-resolution seismic profiles (airguns, Geopulse and ORE 3.5 kHz). A total of 11 Pleistocene and two Holocene sequ ences separated by type-1 or type-2 discontinuities were identified. The ag e of the depositional sequences was determined based on foraminifera ages f rom boreholes and by correlation with seismic profiles of the slope areas w ith uniform deposition and without significant discontinuities. These seism ic units have been mapped throughout the margin, allowing to establish the correlation with eustatic sea-level curves and global climatic trends. The distribution and geometry of the units reveals that most of the sedimentary record was developed during episodes of forced regression. Ten regressive periods, corresponding to 5th-order cycles arranged into 4th-order, were di stinguished. Absolute water depths for the development of coastal deposits in each unit were calculated using depth from present-day sea-level, correc ted for tectonic subsidence in the area. The model for the evolution of the depositional system of the Gulf-of Cadiz continental margin highlights the strong influence of tectonism in the development of depositional bodies, c ontrolling the distribution of deposits generally produced during episodes of sea-level fall. (C) 1999 Elsevier Science B.V. All rights reserved.