On the origin of the Oak Ridges Moraine

Landscape analysis, mapping, sedimentology, shallow geophysics, and borehol e data are integrated to better understand the complex landform-sediment ge ometries and event sequences of the Oak Ridges Moraine, southern Ontario. A model for the origin of the Oak Ridges Moraine is based on the recognition that the moraine is built on a high-relief, erosional surface (unconformit y) consisting of drumlin uplands and a network of deep, steep-walled, inter connected valleys (tunnel channels). The development of the moraine is thou ght to have occurred in four stages: I, subglacial sedimentation; II, subaq ueous fan sedimentation; III, fan to delta sedimentation; IV, ice-marginal sedimentation. The model traces the transition from subglacial to proglacia l conditions during moraine formation and examines the order and timing of sedimentation. It is thought that the early stages of moraine construction are better exposed in the east; in the west, these stages are buried by lat er stages.