GEOMORPHOLOGY OF A LATE WISCONSIN HARD-BEDDED ICE STREAM LANDSYSTEM, ONTARIO, CANADA REVEALED BY HIGH RESOLUTION LIDAR MAPPING

The ‘age of LiDAR’ is revolutionizing the study of the Earth’s surface. This paper showcases the enhanced utility of 3-D surface visualization models derived from high-resolution LiDAR data sets over traditionally used 2-D models for the purpose of qualitatively discriminating, classifying and mapping subtle hitherto unmapped glacial landforms left behind by the retreat of a hard-bedded paleo-ice stream (Ontario Ice Stream: OIS) within the Laurentide Ice Sheet in Eastern Ontario, Canada. The hard bed consists of flat-lying Paleozoic limestone plains extending as a broad west-east belt immediately south of the Canadian Shield from Lake Huron to the St. Lawrence River Valley. The largest landform is the Dummer Moraine along the Shield-Paleozoic boundary consisting of undulating hummocky topography composed entirely of clast-supported limestone rubble with large detached bedding plane slabs the result of subglacial hydrofracturing and bed-freezing below a thin retreating ice margin along the northern limit of Paleozoic carbonates. Southward dipping limestone bedding plane surfaces, expressed as extensive bare plains, show swaths of parallel linear grooves cut by fast flowing ice entraining subglacial debris dominated by hard Shield lithologies. The southern and lowest part of the hard bed near Lake Ontario was covered by waters of glacial Lake Iroquois a much larger late glacial precursor to Lake Ontario that drained abruptly at about ~13 cal kyr BP though the Hudson River Valley. Seasonal calving of ice bergs from the retreating ice stream margin standing in glacial Lake Iroquois is recorded by swaths of De Geer moraine ridges composed of bulldozed glaciolacustrine clay and identify an annual ice margin retreat rate between 30 and 100 m. A related but subtle landscape element comprises hundreds of linear to curvilinear ice scours up to 3 km long. This paper highlights the growing importance of geoinformatics techniques in the field of glaciology and the understanding of ice sheet beds and reiterates the need for further research into the application of more advanced computer vision techniques.