Macrofabrics and quartz microstructures confirm glacial origin of Sunnybrook drift in the Lake Ontario basin

Macrofabric studies and scanning electron microscopic (SEM) analysis of sand grains in Sunnybrook diamicton confirm that it consists of lodgment and/or deformation till. Formation of Sunnybrook drift included deposition of glaciolacustrine mud and grounding of early Wisconsin ice, followed by rainout of glaciolacustrine sediments. Macrofabric and quartz microtexture analyses support a model of deposition of the middle member (Sunnybrook diamicton, unit b) as lodgment and/or deformation till. Macrofabrics show generally bimodal, and occasionally trimodal, orientations that in the lower part of the unit indicate progressive change in direction of ice movements: first westward to northwestward, and latger (in the middle and top of the unit) to the northwest. Quartz-grain microtextures show extensive crushing effects compatible with deposition by grounded active ice, as determined at other continental locales including Antarctica, Fenno-Scandia, northern Ontario, and Wellsch Valley, Saskatchewan.