RECONSTRUCTING SUBGLACIAL CONDITIONS THROUGH DETAILED MAPPING AND SPATIAL ANALYSIS OF P-FORMS IN THE AREA OF WHITEFISH FALLS, ONTARIO

The Canadian Shield is a large unconformity surface ornamented with a variety of erosional landforms that provides a rich repository of information regarding past subglacial conditions. Erosional landforms are particularly well exposed in the area of Whitefish Falls, Ontario where ancient quartzites, argillites and diamictites of the Huronian Supergroup have been sculpted into a variety of forms including whalebacks, roche moutonnee and p-forms. P-forms (also called s-forms) are abundant in the Whitefish Falls area and understanding their origin can provide valuable information regarding the roles of debris-rich basal ice, saturated till streams and pressurized, debris-charged subglacial meltwater flows in the formation of glacially eroded surfaces.

Identification and detailed mapping of over 180 p-forms in an approximately 1 km² area south of Whitefish Falls allowed documentation of the characteristic features of these distinctive landforms. A handheld GPS was used to record the location, elevation and relief of p-forms and associated landform elements including scalloped and striated (parallel and chaotic) bedrock surfaces. Information regarding landform scale, long axis orientation and relationship to surrounding topographic features was also recorded in the field. Data were then subject to kernel density analysis to analyze and visualize the spatial distribution of the p-forms and to identify possible relationships between p-forms and other glacial landforms in the area such as roches moutonnees and whalebacks.

The juxtaposition of parallel and chaotically oriented striae with curved, sculpted bedrock forms within many of the p-forms suggests that abrasion by debris-rich basal ice, saturated till and subglacial meltwater all contributed to the formation of these complex landforms. Digital elevation model analysis of the study area indicates a strong topographic control on p-form genesis with most being concentrated on the upglacier side of bedrock highs where meltwater and saturated till streams may have been concentrated. The close association of the distribution of p-forms with that of roches moutonnee suggests that both features formed under similar conditions, possibly below thin, fast moving ice lubricated with abundant subglacial meltwater.