Facies and sequence analysis of Nova Scotian Slope muds: turbidite vs ‘hemipelagic’ deposition

Summary Five fine-grained mud facies were identified in piston-cores obtained from the Nova Scotian Slope. The sedimentary structures of the muds indicated deposition under varying bottom-current conditions and rates of sediment supply. Two facies associations were recognized using Markov sequence analysis: (a) turbidite and (b) non-turbidite associations. The problems of recognizing turbidite, contourite and hemipelagic deposits in fine-grained sequences are discussed in the context of low-concentration, low-velocity flows. The dynamics of unconfined flows indicates that turbidity currents become unstable and are deflected by Coriolis to near contour-parallel flow. Dilution and deceleration of the flow may produce a transition to hemipelagic-type deposition. Transitions of this type within individual flows make recognition of discrete turbidite, contourite or hemipelagic processes very difficult in parts of the geological record.