On the origin of the Oak Ridges Moraine

Abstract

Landscape analysis, mapping, sedimentology, shallow geophysics, and borehole data are integrated to better understand the complex landform-sediment geometries 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 (unconformity) consisting of drumlin uplands and a network of deep, steep-walled, interconnected valleys (tunnel channels). The development of the moraine is thought to have occurred in four stages: I, subglacial sedimentation; II, subaqueous fan sedimentation; III, fan to delta sedimentation; IV, ice-marginal sedimentation. The model traces the transition from subglacial to proglacial 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 later stages.

Subglacial and ice‐marginal landforms in south‐central Ontario: implications for ice‐sheet reconfiguration during deglaciation

“…Towards the end of glaciation, increased meltwater production led to the deposition of thick successions of stratified sand, gravel and silt comprising the ORM (Fig. 1) between two ice masses lying to the north and south (Chapman & Putnam 1984;Barnett et al 1998). As ice retreated, high-level lakes formed, dammed against high topography and the receding ice margin until successively lower outlets were exposed permitting drainage of the lakes.…”

Subsurface heterogeneity in the geological and hydraulic properties of the hummocky Paris Moraine, Guelph, Ontario

“…As positive relief features in the landscape, these moraines are often considered important zones for recharge, and some host complex and stratified aquifers that are an important source for nearby urban centres (Sharpe et al 1996Howard et al 1997;Bajc and Shirota 2007;Bajc et al 2014). While several interlobate stratified moraine complexes in southern Ontario have been the focus of comprehensive geological and hydrogeological studies (Barnett et al 1998;Sharpe et al 2004;Bajc et al 2014), end and recessional moraines have generally not received the same attention from the international scientific community (Andersson 1998;Gartner Lee Ltd. 2004;Blackport Hydrogeology Inc. et al 2009;Russell et al 2009Russell et al , 2013.…”

Three-dimensional hydrostratigraphy of the Orangeville Moraine area, southwestern Ontario, Canada

“…Multiple overlapping broad channels infilled with sand, and occasionally gravel (Fig. 12G), may represent distributary channels crossing the fan surface, similar to those observed in proximal to midsubaqueous fans that constitute the Oak Ridges Moraine (Barnett et al 1998). Cross-bedded and planar laminated medium to fine sand, ripple cross-laminated sand to silty sand (Figs.…”

“…Cobble gravel and interbedded gravel and sand fine southward to laminated and ripple cross-laminated sand overlain with rhythmically bedded sand, silt, and clay (Table 2). Following the models of the nearby Waterloo Moraine (Bajc et al 2014) and Oak Ridges Moraine (Paterson and Cheel 1997;Barnett et al 1998), the cobble gravel beds are interpreted as hyperconcentrated density flow deposits (Mulder and Alexander 2001) reflecting a subglacial conduit to ice-proximal setting (Benn and Evans 1998). The horizontally laminated and ripple cross-laminated sand is interpreted as traction deposits from unconfined concentrated flows representing the interchannel zones of a subaqueous fan, while the rhythmically bedded sand and silt record increasing deposition from suspension in more distal subaqueous fan settings.…”

“…Cross-bedded and planar laminated medium to fine sand, ripple cross-laminated sand to silty sand (Figs. 10F-10H), and sand rhythmically bedded with laminated silt and clay (Burt and Webb 2013) reflect increasing deposition from suspension moving towards a distal fan setting (Barnett et al 1998;Delaney 2002).…”