The effect of the circulation of polar-sourced dense waters on the deep seafloor is still largely unknown. This paper presents multibeam bathymetric evidence for the existence of present-day contourite drifts on the central Pacific ocean at depths ranging between 4000 and 5000 m, based on the identification of their diagnostic erosive (moats, linear moats, furrows and abyssal sinuous channels) and depositional (plastered, elongated separated and abyssal contourite-fan drifts) contourite morphological features. These contourite drifts display a patchy distribution, sculpted by the secondary flows of the Lower Circumpolar Water (LCPW) and the North Pacific Deep Waters (NPDW), as well as local dynamics of the flow in the form of internal waves and bottom currents modulated by tides, which are capable of accelerating the typically sluggish bottom currents and contribute to the erosion, transport and deposition of sediments. The formation of contourites is also predominantly controlled by the presence of large-scale tectonic and volcanic features (ridges, seamounts and deep elongated valleys), which affect the morphology and distribution of the basins and induce the acceleration of bottom currents. Overall, this study allows to re-assess the effects, distribution and significance of bottom-current controlled sedimentation in abyssal environments, where examples of contourite features are still rather scarce in part because of the technical challenges and their remote location, but also because the effect of bottom currents is not well known in the central oceanic basins and only capable of marginally affecting their sedimentological record. |
