recruitment to other areas. The submarine canyons of the northwest Atlantic 

 that fit this characterization are the following: 



Corsair Heezen 



Powell Lydonia 



Gilbert Oceanographer 



Hydrographer Veatch 



Atlantis Block 



Hudson Norfolk 



There are other, smaller canyons and gullies, but they more closely 

 resemble habitats on the continental slope, or have not been studied. 



Submarine Canyon Morphology and Sedimentary Environments 



Submarine canyons on the southern margin of Georges Bank exhibit wide 

 variability in size and shape. Canyon morphology modifies axial current flow 

 that, in turn, is linked directly to variability of sedimentary environments. 

 The largest canyons incise the shelf 13 to 25 km and have 750 to 1,000 m of 

 relief at the shelf break (200 m) . They are characterized by strong currents 

 and heterogenous sedimentary environments that include large areas of gravel, 

 rippled and duned sand, and bioeroded Pleistocene silt and clay outcrops. 

 Medium-size canyons (8 to 18 km length, 320 to 520 m relief) and small canyons 

 (2.5 to 5 km length, 200 to 300 m relief) exhibit proportionally less textural 

 variability and lower energy levels. The smallest canyons are broad 

 embayments of the shelf edge, and sediment texture is similar to the 

 homogeneous silty sand that covers the upper slope. Source areas of sediment 

 for the canyons are the continental shelf and bioerodable Pleistocene silt and 

 clay that veneers canyon walls. 



Erosional processes on the bank margin include (a) sand transport from 

 the shelf edge and canyon rims to the upper slope and canyon walls, 

 respectively; (b) winnowing of fine sediment from sand on the upper slope in 

 the 200 to 300 m depth interval; (c) bioerosion of Pleistocene silt and clay 



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