Sedimentology of the Oak Ridges Moraine, Humber River watershed, southern Ontario: a preliminary report

Abstract

The Oak Ridges Moraine is a 150 km long landform of regional significance for groundwater recharge. It crops out across 16% of the 900 km2 Humber River watershed and its subsurface extent is poorly understood. Six lithofacies form much of the moraine in the study area and are discussed within the context of three sites. Architectural associations studied in outcrop are dominated by broad, shallow channels and scours, filled predominantly with medium sand and gravel facies. At two sites, drill core intersects the complete thickness of the moraine and consists mostly (~60-70%) of two lithofacies; graded fine sand-silt and small-scale cross-laminated fine sand-silt. At one of the two sites, gravel constitutes up to 30% of the moraine thickness. This study suggests that the moraine has been formed in an ice-supported environment by pulsating glaciofluvial flow discharging subaqueously in a glaciolacustrine environment.