A Basin Analysis of the Wabigoon Area of Lake Agassiz, a Quaternary Clay Basin in Northwerstern Ontario

Abstract

Cet article est diffusé et préservé par Érudit.Érudit est un consortium interuniversitaire sans but lucratif composé de l'Université de Montréal, l'Université Laval et l'Université du Québec à Montréal. Il a pour mission la promotion et la valorisation de la recherche. www.erudit.org Tous droits réservés © Les Presses de l'Université de Montréal, 1992 Géographie physique et Quaternaire, 1992, vol. 46, n° 3, p. 295-309, 11 ABSTRACT Information from a wide range of sources is integrated in a basin analysis of the Wabigoon Basin, a Quaternary clay basin located on the Canadian Shield in northwestern Ontario. The basin sediments were deposited between 10.9 ka and 9.5 ka, along the margin of the Rainy Lobe of the Laurentide Ice Sheet, which formed the northern boundary of proglacial Lake Agassiz. The basin architecture is dominated by four major elements: end moraines, eskers, kames and a clay plain, all of which overlie irregular bedrock topography. End moraines, eskers and kames are composed mainly of a fining upward sequence of gravels and sands. The geometry of these sedimentary units, and their sedimentary structures indicates they were deposited mainly by high and low-density turbidity currents, on ice-marginal subaqueous outwash fans. Eskers contain a core of coarse gravel and sand deposited within subglacial meltwater conduits, overlain by subaqueous fan sediments deposited at the conduit mouth. Esker ridges were formed during conduit filling events and flanking deposits were formed when a conduit remained in use during icemarginal retreat. Where conduits were shortlived, isolated subaqueous fans (kames) were formed. A depositional model is proposed which relates moraine formation to catastrophic releases of subglacial meltwater and sediment simultaneously along the entire margin of the Rainy Lobe. The clay plain forms a broad blanket of fine-grained, rhythmically-bedded sediment which obscures bedrock topography, and often buries esker and kame deposits. Seismic profiles and overburden drilling reveal deep (50-70 m) bedrock lows beneath the clay plain. These lows, oriented sub-parallel to the ice margin, acted as sediment traps, and were infilled by the deposits of underflows generated at the ice margin.

Moraines and late-glacial stratigraphy in central Lake Superior

“…The subaqueous outwash thins and becomes less reflective away from the moraines. All of these characteristics suggest that the till, outwash, and glacial-lacustrine varves originated in a depositional environment similar to those in which sedimentation occurs at a submerged grounding line, in either lacustrine (e.g., Rust and Romanelli, 1975; Sharpe et al, 2007; Geirsdóttir et al, 2008) or marine (e.g., Lonne et al, 2001) environments. Understanding sedimentary processes and architecture at grounding lines in aqueous environments is important because of the critical role these environments play in the stability of marine ice sheets, such as the West Antarctic ice sheet (e.g., Rignot et al, 2011).…”

“…These are the same as the Washburn and Beaver Bay moraines of Landmesser et al (1982) and the I and II moraines of Breckenridge (2013). Although the bulk of some end moraines in the region may be composed of stratified drift (e.g., Sharpe et al, 2007), the Isle Royale moraines are cored with till, clearly distinguished from stratified outwash. On the distal sides of the moraines, outwash grades into, and interfingers with, till, forming a depositional wedge (see Figs.…”

“…Most of the stratified outwash in the study area occurs to the southwest of the major moraines, but thin outwash is found on bedrock in the northeast part of the study area as well. Because the Marquette readvance was continuously in contact with a series of proglacial lakes (Farrand and Drexler, 1985;Breckenridge, 2013), the stratified outwash is interpreted as subaqueous, deposited in freshwater settings similar to those described elsewhere (e.g., Rust and Romanelli, 1975;Sharpe et al, 2007;Geirsdóttir et al, 2008).…”

Sedimentary architecture and glacial hydrodynamic significance of the stratified Oak Ridges Moraine, southern Ontario, Canada

“…Exceptional meltwater events (floods) formed stratified moraines in northwestern Ontario (Hartman, Sharpe & Cowan 1990; Sharpe et al . 1992) and western Quebec (Harricana, Brennand & Shaw 1996). These flood interpretations are based on landform analysis, sedimentology and stratigraphic context.…”

Geophysical characterization of late-Quaternary glaciofluvial complex and glacial stratigraphy in the Satakunta sandstone area, Köyliö, southwest Finland

“…The ability to resolve structures at depth in saturated, >100-m-thick glacial sediments makes the HRSR method excellent compared to GPR, which has penetration depths limited to 20-40 meters depending on the antenna frequency and electrical conductivity of the materials. The HRSR method with landstreamer has been used during various hydrogeological studies of tunnel valley aquifers in Canada and the United States (Pugin et al, 2004;Ahmad et al, 2009;Pugin et al, 2009;Pugin et al, 2014a), and in esker characterization in Canada (Sharpe et al, 1992;Barnett et al, 1998;Pugin et al, 1999;Cummings and Russell, 2007;Pullan et al, 2007;Tremblay et al, 2010;Cummings et al, 2011), Finland (Maries et al, 2017;Brodic et al, 2018), and the European Alps (Burschil et al, 2018).…”