麻豆传媒

A series of shoreface-connected sand ridges occur on Sable Island Bank adjacent to Sable Island, are best developed to its south and southwest and extend as far as 23 km south of the island in water depths up to 45m. In an effort to get a better understanding of the morphological and sedimentological dynamics of the ridge field, a database of new and existing seismic data and regional bathymetric data (from Canadian Hydrographic Service) was compiled to analyse the wavelength, height and symmetry of the sand ridges. The database will also serve as a means of comparison between older bathymetric data, and the newer seismic data. To address the hierarchy of reactivation events within individual sand ridges, seven vibrocores were collected during B.I.O Cruise Hudson-2000-030A in July, 2000. 997, and 5873 bedforms were measured from the Bathymetric and seismic data respectively. The average wavelength of the measured bedforms was 620m +/- 1271.25m, and the average height was found to be 1.04m +/-1.77m. Through comparing the size of the measured bedforms with the classification scheme defined by Amos and King (1984), the bedforms are almost exclusively within the sand ridge/sand ribbon size zone. The measured symmetry of the sand ridges showed no preferred asymmetry. All the vibrocores, regardless of their sample position had thick units of the parallel laminae bound by a basal lag and fining upward sequences at the base, and angled laminae, cross bedding and bioturbated deformation near the top. This sequences is associated with storm generated sheet flew deposits. The traditional understanding of the shoreface-attached sand ridges on Sable Island Bank is that they are migrating in an eastward direction by means of transverse sediment flow. The results from this study have found that the majority of the measured bedforms (sand ridges and sand ribbons), and internal structures from the cores, (thick units of parallel laminae associated with sheet flow) are similar to those formed under longitudinal flow conditions. Multibeam bathymetry images of south Sable Island show a complex network of sand ribbons coming away from Sable Island and into the sand ridges that could be the pathway for longitudinally transported sediments.

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Pages: 119
Supervisor: Ned King