Clinoform quantification for assessing the effects of external forcing on continental margin development

The Ebro continental margin is characterized by a complex pattern of well-developed, highly progradational and aggradational, margin-scale clinoforms. Analysis of conventional 3D seismic reflection data combined with quantitative analyses of margin growth rates, slope geometries, incisional features and shelf-edge trajectories through time, provides further insights into the signal imposed by externally driven mechanisms on continental margin stratigraphy. Three phases of construction characterize the Ebro continental margin evolution since the Messinian Salinity Crisis. These phases reflect the changes in the climate/sea-level cyclicity from the Pliocene to the Pleistocene and its effects on sediment supply and sedimentary processes. Nonetheless, morphodynamic feedbacks of the system had a profound effect on the mechanisms of margin growth and sediment distribution. The frequency and amplitude of the progradational pulses of the system follows the trend of climate/sea level as indicated by oxygen isotope records. Generally, major steps of progradation are coeval with pulses towards glacial development. However, the amplitudes of the peaks do not always correlate due to the effects of other variables that are less directly dependent on climate, in particular, modifications of the progradational trends by mass-wasting processes. The increase in sediment supply and accommodation creation during the Pleistocene along with the progradation of the system into deeper water resulted in progressively steeper slope gradients. Consequently, mass-wasting processes became the primary sediment delivery mechanism during the Pleistocene. In addition, cross-shelf incised valleys are not observed throughout the succession, therefore, widely accepted mechanisms of sediment delivery across continental margins and the classic sequence stratigraphic model for margin development are called into question in this system. Quantification of the slope curvature throughout the succession reveal that sigmoidal clinoform profiles correspond to un-modified slopes while exponential geometries result from a modification of the original shape of the slope by erosional processes.