Turbidity current velocity, grain size and bedforms in turbidite channels and associated depositional systems

For much of their active life turbidite channels are characterised by relatively high velocity turbidity currents and associated mass transport processes. This high-energy phase leaves behind a signature of erosion and down-cutting, coupled with masstransport deposits, coarse- to medium-grained turbidites and deepwater massive sands. Thick to very thick beds are common, typically with lenticular geometries and marked lateral thickness variation, but with little evidence of systematic vertical trends of bed thickness. The late fill and abandonment stage of most channels is characterised by relatively lower velocity turbidity currents and associated emipelagic processes. This low-energy phase results in medium- to fine-grained
turbidites and hemipelagites that are more extensive and continuous laterally and, in some cases, show upward-thinning trends of bed thickness. Channel levee, overbank and open-slope settings generally show still lower-energy currents and a dominance of fine-grained turbidites and hemipelagites.