Downcurrent variation in submarine channel‐fill architecture from the shelf to upper slope

The transition between the shelf and the upper slope is often considered an area of sediment bypass, where steeper gradients increase flow velocities and maintain particles in suspension. In addition to transferring sediments into deeper basins, upper-slope areas can also host channelised submarine deposits. Such upper-slope channel networks are often complicated, showing dendritic patterns of relatively small-scale channels. Subsurface datasets typically lack the resolution to resolve the complexities of these portions of the slope profile. Outcrop analogues can provide the required resolution and are crucial for understanding the architecture of ancient turbidite systems in upper-slope settings. During the late Tortonian, the Taza-Guercif Basin recorded the transition from a mixed carbonate-siliciclastic shelf to deepmarine conditions, marked by marlstone deposition. This study documents the lower Melloulou Formation, in which turbidite sandstones fill channels incised into these marls. Mapping at a 1:5000 scale along with a total measured thickness of ~1100 m from 27 stratigraphic logs documented over fifty channel-fill bodies from well-exposed outcrops, allowing both the possibility to investigate these features in a downslope perspective and their relationship with the shelf. Key depositional/erosional features, internal architecture, stacking patterns and aspect ratios define four depositional styles for these channel fills: (i) isolated, (ii) laterally migrating, (iii) stepped and (iv) vertically offset. Four preferential channel pathways evolving from shallowwater areas down the slope profile are recognised, each characterised by variation in channel-fill style along the stratigraphy. Slope gradient, structural controls on the slope profile, inherited shelf paleotopography and downslope variations in flow parameters governed sedimentation. Reconstruction of the temporal evolution of the upper slope enables the development of a conceptual model for the downslope sediment-routing framework, linking these pathways to intra-reef gullies (sharms) on the shelf. This model highlights the possible physical continuity between slope sand bodies and more proximal, permeable units, such as shelf and fluvial deposits, thereby increasing the risk of upslope stratigraphic trap leakage.