麻豆传媒

B. Sc. Honours Thesis

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Acoustic and sample data have been collected in a 600 km2 area of the innermost Scotian Shelf along the Eastern Shore just east of Halifax. In addition sediment distribution has been mapped and rates of coastal change determined along the 40 km long coastline. Surface-towed sparker, V-fin, and 3.5 KHz reflection seismic records along with sediment samples show surficial material to consist of post-glacial sediment, glacial till, and bedrock. Sediment in the area occurs in patches, forms a thin veneer over bedrock, and fills depressions between bathymetric highs. The maximum thickness of sediments ranges up to 50 milliseconds (two-way travel time) or approximately 20 metres, in the offshore areas. Relict glacial till deposits are up to 30 msec. thick; some have drumlin-like forms.

An average annual rate of cliff retreat of .81 metres per year was recorded from six stations along the shore. Comparison of 1945 and 1974 air photos reveals an average annual retreat rate of .71 metres per year. This coastal retreat results in approximately two million cubic metres of unconsolidated sediment being supplied through erosion to the coastal zone. The geological evolution of the study area is interpreted as being strongly influenced by the Holocene transgression in water depths of less than 50 m. During transgression, coastal erosion of till cliffs may have been as rapid as at present, thus supplying large amounts of sediment to the nearshore area. Where glacial till was protected during the marine transgression by barrier beaches the till was covered by lagoonal sediments and was consequently preserved from nearshore erosion.

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Pages: 69
Supervisor:聽 D. J. W. Piper