Four bed-form provinces have been identified on Georges Bank using sidescan sonar and echo-sounding techniques: large sand waves, small sand waves, megaripples, and featureless sea floor. The large sand waves are found on the bank crest where the surface tidal currents are strongest, and are bordered, north and south, by areas of small sand waves and/or megaripples, formed where tidal currents are moderate in strength. Featureless sea floor is found farthest from the bank crest where surface tidal currents are weakest.
Bed-form asymmetry and surface-sediment texture have been used to infer bedload transport paths on the bank. In the large sand-wave area, bed forms converge on linear northwest-striking ridges from both sides implying erosion from the troughs and growth of the ridges. The asymmetry of the small sand waves along the south side of the bank indicates that sand is also transported southward away from the bank. Though the bed-form asymmetry of megaripples could not be determined in this study, the occurrence of megaripples between the sand-wave provinces and areas of featureless sea floor suggests a decreasing effectiveness of sand transport away from the bank crest. This sand transport pattern is further supported by surface-sediment texture which becomes progressively finer both to the north and southwest away from the crest of Georges Bank.
|Title||Bed form distribution and inferred sand transport on Georges Bank|
|Authors||David C. Twichell|
|Publication Subtype||USGS Numbered Series|
|Series Title||Open-File Report|
|Record Source||USGS Publications Warehouse|