Colin D. Pilmer

This project involves the analysis of high resolution shallow seismic reflection profiles collected on the south flank of Sable Island Bank. The objective of this study is to gain an understanding of the genesis and sediment distribution of Sable Island Bank during late Quaternary times.

Six units were identified using the three seismic records. The units are labelled A to F where A is the lowermost unit and F is the uppermost unit. The two lowermost units are present over the whole survey area and are probably glacial in origin however more data are required to verify this. Unit B doesn't contain any internal reflectors but lens-shaped internal reflectors are present in unit A near the shelf edge. These features are interpreted as shelf edge deltas associated with the influx of sediment during the Wisconsinan glaciation.

Unit C is composed of sand and gravel and is present from the northern portion of the survey to the shelf edge. It has horizontal, wavy, inclined and crescentic internal reflectors and it's contact with unit B below is unconformable. Unit C is interpreted as an outwash plain deposit which formed when the Wisconsinan ice sheet retreated approximately 16,000 y B.P.

Unit D is present south of the shelf edge and has horizontal and x or v-shaped internal reflectors. Unit D is interpreted as having been deposited in a marine environment which was sheltered by the remnant Wisconsinan ice. Although the lithology of Unit D can not be determined from the borehole data, interpretation of this acoustic unit suggests that it is fine-grained and derived from the glacial outwash plain. This marine environment transgressed the outwash plain environment as sea level was rising during this time.

Unit E is present only in the northern portion of the survey and is composed of fine sand with the occasional occurrence of silty layers and medium and coarse sand layers. The lower contact of unit E is planar and conformable whereas it's upper contact is unconformable. Unit E is interpreted as an extensive dune system which was later submerged by the rising sea level. Unit E is composed of the reworked sediments of units C and D.

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Pages: 82
Supervisor: Ron Boyd