Drift Sediment

Drift sediment is material deposited as a mounded or sheet-like body, a sediment drift, by persistent along-slope bottom currents rather than by downslope gravity flows. The deposits, called contourites, are reworked and sorted by the current, producing fine-grained, often bioturbated beds with grain size that tracks current strength. Drifts grow on continental rises and slopes where deep thermohaline currents run along the contours, building features kilometers thick over millions of years, such as the drifts of the Atlantic margins. They differ from turbidites, which are downslope event deposits. Drift sediment archives the long-term history of deep-ocean circulation.