3D seismic analysis of slope-confined canyons from the Plio-Pleistocene of the Ebro Continental Margin (Western Mediterranean)

This paper documents the importance of three‐dimensional (3D) seismic data for integrated stratigraphic–morphological analysis of slope systems. Furthermore, it contributes to the general understanding of the evolutionary mechanisms of slope‐confined submarine canyons on continental margins and their significance in a sequence stratigraphic framework. Recently acquired 3D seismic data from the Ebro Continental Margin (Western Mediterranean) have been used to study a series of remarkably well‐imaged submarine canyons in the Plio‐Pleistocene succession. Detailed mapping shows that these canyons are restricted to the slope, and thus can be compared with slope‐confined canyons observed on the present day seabed of many continental margins. The slope‐confined canyons are typically 0.5–2 km wide, 10–15 km long, and incise more than 50 m into the slope units. Their most striking characteristic is an upslope branching geometry in the head region involving up to three orders of bifurcation, with downslope development of a single incisional axis. The submarine canyons are characterized by a nested stacking pattern, undergoing alternating phases of cutting and filling. Limited parts of the upper and middle slope remain outside the canyon system, confined in sharp depositional ridges. The canyons are observed on closely spaced surfaces and exhibit a geometry that allowed the construction and discussion of a local sequence stratigraphic model for their evolution. In general, active incision of the canyons is observed at times throughout almost the entire cycle of base‐level change. However, erosional activity is more significant during the later stages of the relative sea level rise and the entire falling stage, with the timing of maximum erosion observed at the end of the cycle. The minimum erosional activity of the canyons is linked instead to the earliest part of the relative sea level rise.