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TitleSediment transport and development of banner banks and sandwaves in an extreme tidal system: upper Bay of Fundy, Canada
AuthorLi, M Z; Shaw, J; Todd, B J; Kostylev, V E; Wu, Y
SourceContinental Shelf Research vol. 83, 2014 p. 86-107,
Alt SeriesEarth Sciences Sector, Contribution Series 20130085
Mediapaper; on-line; digital
File formatpdf; html
ProvinceEastern offshore region; Nova Scotia
NTS21H/01; 21H/02; 21H/07; 21H/08
AreaBay of Fundy; Minas Channel; Minas Passage; Cape Split; Scots Bay
Lat/Long WENS -64.7500 -64.3333 45.5000 45.0000
Subjectsmarine geology; geophysics; surficial geology/geomorphology; marine sediments; sediment transport; bedforms; morphology; sand waves; banks; dunes; tides; sediment reworking; tidal environments; tidal currents; flow regimes; marine deposits; sands; gravels; geophysical surveys; acoustic surveys, marine; sonar surveys; models; grab samples; photogeology; banner banks; multibeam bathymetry; groundtruthing surveys; barchan dunes
Illustrationsgeophysical images; location maps; photographs; cross-sections; tables; sonograms; profiles; models; time series
ProgramRenewable Energies, Environmental Geoscience
ProgramOffshore Geoscience
ProgramClean Energy Fund
AbstractMultibeam sonar mapping and geophysical and geological groundtruth surveys were coupled with tidal current and sediment transport model calculations to investigate the sediment transport and formation processes of the complex seabed features off the Cape Split headland in the upper Bay of Fundy. The Cape Split banner bank, composed of coarse to very coarse sand, is a southwest-northeast oriented, large tear-drop shaped sand body with superimposed sand waves that show wavelengths from 15 to 525 m and heights from 0.5 to 19 m. Isolated and chains of barchan dunes occur on top of a shadow bank to the southeast of the banner bank. The barchan dunes are composed of well-sorted medium sand and are oriented northwest-southeast. Their mean height and width are 1.5 and 55 m, respectively. A gravel bank, with an elongated elliptical shape and west-east orientation, lies in the Minas Passage erosional trough east of the headland to form the counterpart to the sandy Cape Split banner bank. The southern face is featureless but the northern face is covered by gravel megaripples.
Tidal model predictions and sediment transport calculations show that the formation of the banner bank and the gravel bank are due to the development of the transient counter-clockwise and clockwise tidal eddies respectively to the west and east of the headland. The formation of barchan dunes is controlled by the nearly unidirectional flow regime in outer Scots Bay. Sand waves on the flanks of the Cape Split banner bank show opposite asymmetry and the barchan dunes are asymmetric to the northeast. The tidal current and sediment transport predictions corroborate bedform asymmetry to show that sand wave migration and net sediment transport is to southwest on the northern flank of the banner bank but to northeast on the southern bank. Long-term migration of the Scots Bay barchan dunes is to the northeast. Spring-condition tidal currents can cause frequent mobilization and high-stage transport over the banner bank and barchan dunes. Strong currents in Minas Passage can cause infrequent low-stage transport over the megarippled northern face but are not high enough to mobilize the coarser gravels on the southern face of the gravel bank.
Summary(Plain Language Summary, not published)
Distribution and stability of seabed substrates and features are crucial issues for the site selection and device design for tidal energy development in the Bay of Fundy. Multibeam bathymetric mapping and geological survey results were coupled with tidal current and sediment transport model calculations to investigate the geomorphology, processes and mobility of banks and their associated large bedforms around the headland of Cape Split, upper Bay of Fundy. The main recognized seabed features are a banner bank with superimposed sand waves, a barchan dune field, and a gravel bank in the deep trough east of the headland. Tidal current and sediment transport predictions indicate that the strong tidal currents can cause frequent mobilization and high transport over the banner bank and the barchan dunes. The gravels on the gravel bank are only mobilized infrequently under low-transport conditions.