Intermittent behavior of bottom currents: The complexity of channels and moats

Abstract Contourite channels and moats are integral to contourite depositional systems in deepwater sedimentary environments. Many channels and moats worldwide share significant sedimentary and stratigraphic complexity along with time-scale variability. Prominent shifts in morphology translate to shifts in stacking pattern through both space and time. Contourite channels evolve from subtle depressions on a terrace, with a predominantly aggradational sedimentary stacking pattern, to narrow and deep moats in both aggradational and progradational configurations with incision and infill phases. Moreover, shifts in facies distribution reflects evolutionary changes within and along channels and moats. These variations depict a long-term transformation from weaker to stronger bottom currents, punctuated by millennial and sub-millennial periods of intermittent activity. These are driven by diverse oceanographic and tectonic processes that govern bottom current dynamics and sediment supply. We illustrate these concepts based on the Pliocene–Quaternary channels and moats along the northern middle slope of the Gulf of Cádiz (along the southwestern Iberian Peninsula). There, the margin paleo-morphology, in particular the presence of canyons, affects the evolution of channels and moats due to short-term intermittency and variations of the Mediterranean Outflow Water. Our study offers new perspectives on contourite depositional systems; in particular, our understanding of channels and moats and their potential role in CO2 storage—impacting the twenty-first–century energy transition.