SI2015-B-1: “Glacial and post-glacial geomorphic evolution of Sable Island and the surrounding Sable Island Bank – Today’s Seabed” – E.L. King, A. Ruffman, M. Li, and K. Webb

Mapping the seabed topography around Sable Island started with British hydrographers Des Barres (1776), Bayfield (1853) and Orelebar (1859). All were lead-line, celestial navigation surveys. The first rigorous sonar hydrography was by Canadian Hydrographic Service (CHS) 1961 and 1963 from CSS Kapuskasing though these surveys kept to the offshore.

With early petroleum exploration, detailed sonar survey work began; an early contractor entrenched the term “Sand Waves” but sand migration was not understood. A commercial gas find prompted 1981-82 CHS surveys (CSS Baffin) producing three charts close to the Island. Further exploration and development necessitated challenging surveys of the East and West Bars. Detailed contour charts (1 and 2 m intervals) were produced at five and 19-year spans, towards serial comparison for evaluating bedform migration.

With growth of engineering seabed infrastructure and need for sediment dynamics understanding, the GSC and CHS conducted multibeam sonar bathymetry (CSS F.G. Creed, 1996 to 2001) covering small, selected sites and some repeat coverage to establish temporal change. These and the early CHS spot depths were quality controlled, and a mosaic produced, culminating in a striking colour-shaded Sable Island Bank bathymetry map presented here. Analysis of the detailed maps and sand cores with unique age-dating helped quantify sand migration.

Drifting sand is the quintessential realm of Sable Island and its environs yet imaging the seabed is but one component toward understanding the forming processes. How it came to be is a question also addressed by imaging geologic strata below the seabed, topics for future presentation.