By Neil Hodgson, Karyna Rodriguez and Lauren Found, Searcher
Cyber Punk’s visionary pioneer William Gibson wrote, “The future has arrived. It’s just not evenly distributed yet”. And certainly the future on the Atlantic’s passive margins is not evenly distributed because the future there lies in hybrid systems; gravity-driven clastic turbidite flows that have been modified during and after deposition by coast-parallel contourite currents.
Gravity-driven turbidites were once assumed to be the dominant (even the “only”) process controlling deep water sediment deposition, but in a remarkable metaphor for modern life, it turns out that it’s the actions of unseen cross-currents that gives shape to what is created. Indeed, contourites rarely leave clear fingerprints on the deepwater sediments we see at outcrop, yet they may have significantly altered the composition of the flow such that classic turbidite Bouma sequences are not deposited at all. Removal of the fine sediment fraction of a turbulent flow, thereby increasing net sand of subsequently deposited sediment (building mud and silt drifts at the same time), creation of asymmetric levees in slope systems that lead to channel migration, evolution of depositional topology on the slope and basin floor, and reworking, redistribution laterally of basin floor sediments are all products of the interactions between gravity driven turbidite flows and contour following currents.