Classification of seafloor geology using multibeam sonar data from the Scotian Shelf

We describe a method for classifying multibeam sonar data, and illustrate the method using data collected with a Simrad EM1000 sonar on the Scotian Shelf, Canada. The method involves comparing various attributes of the bathymetry and backscatter with typical examples of specified seafloor types and computing their statistical degree of similarity. Sediment ponds are identified as areas of low echo amplitude and low topographic gradient and curvature. Ridges and troughs are identified by fitting a paraboloid to patches of the bathymetry.

Once the sediments, ridges and troughs are located, we are able to use the database to extract orientations and other characteristics of these features. For example, the orientation of the topography can be computed from the paraboloid surface, and rose diagrams of the ridge and trough orientations reflect the fabric of up-turned Cambro-Ordovician sedimentary beds outcropping in this area. The unconsolidated sediments ponded within small basins have low topographic gradients with consistent tilts towards the southeast (mean 133°), which we interpret as due to offshore transport of Holocene sediments, possibly in response to storms.