GLACIAL GEOMORPHOLOGY FEATURES OBSERVED ON LIDAR IMAGERY, HALIFAX, NOVA SCOTIA, CANADA

Spectacular images of glacial geomorphology features, especially drumlins and flutings, are evident in the ‘bare-earth' model of the LiDAR survey in the Halifax metropolitan area. Subtle variations in drumlin orientations and shape are clearly defined on the LiDAR imagery. The image also allows for identification of previously unmapped features that can be used to interpret the glacial history. Drumlins in the area are constructed of a red till that is predominantly composed of material derived many tens of km's from the study area, possibly resulting from an ice-stream event. Later glacial events deposited tills of locally derived material that apparently did not significantly modify the drumlins' shape. Because they have different geochemical and geotechnical properties, identifying these sometimes subtle landforms is useful for planning and development purposes.

Drumlins and flutings are located primarily over metasedimentary bedrock and are mostly absent over granitic terrain. Topography does not vary significantly over the area. Down-ice of one zone of drumlin-free granitic bedrock is an area of landforms transverse to ice-flow. Geomorphologically these landforms can be compared to hummocky-active ice moraine in Finland, or Rogen moraine formed along the boundary of sliding to non-sliding ice in northern Canada. The distribution of these landforms in the study area suggests that bedrock type, possibly related to subglacial drainage, strongly influenced glacial dynamics, including the routing of ice-streams and locations of predominantly cold-based patches of ice. Along the margins of the ice-streaming zone that overlies granitic rock, the surface appears to be ice-molded and striated.

The LiDAR image allows for identification of other previously unmapped glacial features including eskers and small drumlins. The imagery also allows the author to make general estimates of till thickness (veneer vs. blanket), aided by depth-to-bedrock measurements in a well-log database. Because the new LiDAR based maps are more detailed, they include previously unmapped alluvium, lacustrine deposits and wetlands, and anthropogenic deposits.