@article {6177, title = {The Role of Deep-Water Sedimentary Processes in Shaping a Continental Margin: The Northwest Atlantic}, volume = {393}, year = {2017}, month = {November 1}, pages = {245-259}, publisher = {Elsevier}, abstract = {

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, spanning about 32\° of latitude and the shelf edge to the abyssal plain. This assessment is based on new multibeam echosounder data, global bathymetric models and sub-surface geophysical information.

The deep-water NWAM is divided into four broad geomorphologic classifications based on their bathymetric shape: graded, above-grade, 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, 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. If 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, whereas smaller mass failures tended to remain on the slope

}, keywords = {contourites, deep-water, geomorphology, geostrophic current, mass-transport deposits, mtd, northwest atlantic margin, turbidites}, doi = {http://dx.doi.org/10.1016/j.margeo.2017.08.018}, url = {http://www.sciencedirect.com/science/article/pii/S0025322717304073}, author = {David C Mosher and Campbell, D.C. and James V. Gardner and J.D. Chaytor and M. Rebesco} } @article {5924, title = {Bathymetric Terrain Model of the Atlantic Margin for Marine Geological Investigations, Version 2.0}, volume = {Version 2}, year = {2016}, month = {February 23}, pages = {17}, institution = {U.S. Geological Survey (USGS)}, address = {Woods Hole, MA}, abstract = {

A bathymetric terrain model of the Atlantic Margin covering almost 725,000 square kilometers of seafloor from the New England Seamounts in the north, to the Blake Basin in the south is compiled from existing multibeam bathymetry data for marine geological investigations. Although other terrain models of the same area are extant, they are produced from either satellite-derived bathymetry at coarse resolution (ETOPO1), or use older bathymetry data collected using a combination of single beam, and multibeam sonars (Coastal Relief Model). The new multibeam data used to produce this terrain model have been edited using hydrographic data processing software to maximize the quality, usability, and cartographic presentation of the combined 100-meter resolution grid. The final grid provides the largest, high resolution, seamless terrain model of the Atlantic Margin.

}, author = {B.D. Andrews and J.D. Chaytor and ten Brink, U.S and D. S. Brothers and James V. Gardner and Elizabeth Lobecker and Brian R Calder} } @article {5922, title = {Geomorphology of the Northwest Atlantic Continental Margin: The Role of Deep Sea Sedimentation Processes}, year = {2016}, month = {December 12-16}, pages = {San Francisco, CA}, abstract = {

Deep-sea sedimentation processes impart a fundamental control on the morphology of the western North Atlantic continental margin from Blake Spur to Hudson Strait. This fact is illustrated by the variable patterns of cross-margin gradients that are based on extensive new multibeam echo-sounder data in concert with subbottom profiler and seismic reflection data. Most of the continental margin has a steep (\>3o) upper slope down to 1500 to 2500 m and then a gradual middle and lower slope with a general concave upward shape There is a constant
interplay of deep sea sedimentation processes, but the general morphology is dictated by the dominant one. Erosion by off-shelf sediment transport in turbidity currents creating channels, gullies and canyons creates the steep upper slope. These gullies and canyons amalgamate to form singular channels that are conduits to the abyssal plain. This process results in a general seaward flattening of gradients, producing a concave-upward continuous, curvilinear slope profile. Comparatively, sediment mass failure produces steeper upper slopes due to head scarp development and a wedging architecture to the lower slope as deposits thin in the\ downslope direction. This process results in either a two-segment slope, and/or a significant downslope gradient change where MTDs pinch out.

Large sediment bodies deposited by contour-following currents are developed all along the margin. Blake Ridge, Sackville Spur, and Hamilton Spur are large detached drifts on disparate parts of the margin. Along their crests, they form a linear profile from the shelf to abyssal plain. Deeper portions of the US continental margin are dominated by the Chesapeake Drift and Hatteras Outer Ridge; both plastered elongate mounded drifts. Farther north, particularly on the Grand Banks margin, are plastered and separated drifts. These drifts tend to form bathymetric steps in profile, where they onlap the margin. Stacked drifts create several steps. Turbidites of the abyssal plain onlap the lowermost drift creating a significant gradient change at this juncture. Understanding the geomorphological consequences of deep sea sedimentation processes is important to extended continental shelf mapping, for example, in which gradient change is a critical metric.

}, author = {David C Mosher and Campbell, D.C. and James V. Gardner and J.D. Chaytor and Piper, D.J.W. and M. Rebesco} } @article {5271, title = {Bathymetric terrain model of the Atlantic margin for marine geological investigations.}, year = {2013}, pages = {11}, chapter = {U.S. Geological Survey Open-File Report}, author = {B.D. Andrews} }