The Northwest African slope apron: a modern analogue for deep-water systems with complex seafloor topography

Abstract

The Northwest African slope apron is an interesting modern analogue for deep-water systems with complex seafloor topography. A sediment process map of the Northwest African continental margin illustrates the relative roles of different sedimentary processes acting across the entire margin. Fine-grained pelagic and hemipelagic sedimentation is dominant across a large area of the margin, and is considered to result from background sedimentary processes. Alongslope bottom currents smooth and mould the seafloor sediments, and produce bedforms such as erosional furrows, sediment waves and contourite drifts. Downslope gravity flows (debris avalanches, debris flows and turbidity currents) are infrequent but important events on the margin, and are the dominant processes shaping the morphology of the slope and rise. The overall distribution of sedimentary facies and morphological elements on the Northwest African margin is characteristic of a fine-grained clastic slope apron. However, the presence of numerous volcanic islands and seamounts along the margin leads to a more complex distribution of sedimentary facies than is accounted for by slope apron models. In particular, the distribution and thickness of turbidite sands are controlled by the location of the break-of-slope, which is itself controlled by the pre-existing submarine topography.