Self-organization of turbiditic lobe deposits: insights on stacking patterns and flow field evolution from analogue experiments under constant boundary conditions

Depositional patterns of submarine lobes are driven by a combination of allogenic (e.g., climate, tectonics) and autogenic processes (e.g., avulsion, bifurcation). However, the impact of autogenic processes and their influence on the formation and evolution of submarine lobes remain poorly understood. Studying these internal dynamics in the outcrop or in the deep sea is challenging due to natural deposits recording a mixture of autogenic and allogenic signals. To examine the autogenic development of submarine lobes, three series of experiments were conducted under constant boundary conditions in the Eurotank Flume Laboratory. Emphasis was placed on documenting stacking patterns and the evolution of turbidity currents relative to topography. The resulting deposits display three stacking patterns: compensational, aggradational, and retrogradational. The velocity of the turbidity currents (measured in the basin floor beyond the break-of-slope) decreased with each subsequent run, along with the development of backstepping, lateral spreading and thinning upward trend in the basin floor deposits. These depositional patterns are interpreted as a result of successively increasing sediment retention in the channel. These results suggest that autogenic processes in sand-rich turbidite systems create complex sediment stacking patterns, ranging from aggradation to retrogradation. Progradational stacking patterns were not observed in any of the experimental series, which suggests that progradation is likely controlled by allogenic processes. This experimental study, addressing characteristics of autogenically formed lobe deposits, will help with disentanglement of the autogenic “noise” from the external signal record stored in the deposits and enable better assessment of climate and tectonic signals.