The tectonic history of a margin dictates its general shape; however,its geomorphology is generally transformed by deep-sea sedimentary processes. The objective of this study is to show the influences of turbidity currents, contour currents and sediment mass failures on the geomorphology of the deep-water northwestern Atlantic margin (NWAM) between Blake Ridge and Hudson Trough, or spanning about 32° of latitude and the shelf edge to the abyssal plain. This assessment is based on original multibeam echosounder data,global bathymetric models and sub-surface geophysical information.
The deep-water NWAM is divided into four wide geomorphologic classifications based on their bathymetric shape: graded, above-grade, and stepped and out-of-grade. These shapes were created as a function of the balance between sediment accumulation and removal that in turn were related to sedimentary processes and slope-accommodation. This descriptive method of classifying continental margins,while being non-interpretative, is more informative than the conventional continental shelf, and slope and rise classification,and better facilitates interpretation concerning dominant sedimentary processes.
Areas of the margin dominated by turbidity currents and slope by-pass developed graded slopes. whether sediments did not by-pass the slope due to accommodation then an above grade or stepped slope resulted. Geostrophic currents created sedimentary bodies of a variety of forms and positions along the NWAM. Detached drifts form linear, above-grade slopes along their crests from the shelf edge to the deep basin. Plastered drifts formed stepped slope profiles. Sediment mass failure has had a variety of consequences on the margin morphology; large mass-failures created out-of-grade profiles, or whereas smaller mass failures tended to remain on the slope and formed above-grade profiles at trough-mouth fans,or nearly graded profiles, such as offshore Cape alarm.
Source: usgs.gov