Ice-Flow Chronology and Palimpsest, Long-Distance Dispersal of Indicator Clasts, North of the St. Lawrence River Valley, Quebec

Abstract

An ice flow model, based on the distribution of distinctive Proterozoic erratics from the Lake Mistassini and Monts Otish sedimentary basins, and on the mapping of relict striations in a 230 000 km2 area located predominantly in Grenville Province, Québec, is presented to reconstruct the evolution of a large part of the Labrador Sector of the Laurentide Ice Sheet during the Wisconsinan. The results, were added to those of similar surveys carried out in the Abitibi region, and further north. Striated surfaces and indicator clasts from an early northwestward flow, overprinted by those from a widespread southeastward flow, and lastly by those from deglaciation flows toward the southwest, south, and southeast, revealed a complex sequence of events. The northwestward flow originated from a NE‑SW, early Wisconsinan, ice divide located in the Québec highlands, south of Lake Mistassini, that migrated to a position north of the lake, at the Last Glacial Maximum, to give rise to the widespread, southeastward ice flow, that left traces over a large part of Grenville Province. Deglaciation triggered a clockwise shift in ice-flow south of Lake Mistassini, and a counterclockwise shift, north of it. Inception of the northwestward flowing glacier probably results from the coalescence of ice caps formed at the highest elevations along a narrow fringe, north of and parallel to the St. Lawrence River Valley, and expansion toward the northwest suggests a similarity with the windward growth model of ice sheet expansion. The ice flow model has implications for mineral exploration methods based on the sampling of glacial sediments.Une séquence d’écoulements glaciaires est proposée pour expliquer l’évolution d’une grande partie du secteur du Labrador de la calotte laurentidienne au cours du Wisconsinien, à partir de la répartition d’erratiques distinctifs provenant des roches protérozoïques des bassins sédimentaires du lac Mistassini et des monts Otish, et de celle de stries glaciaires anciennes dans une région d’environ 230 000 km2, dont la majeure partie est située dans la province de Grenville, au Québec. Ces nouvelles données ont été ajoutées à celles provenant de levés semblables menés antérieurement en Abitibi, et plus loin au nord. Les surfaces striées et les indicateurs lithologiques de transport glaciaire, associés au premier écoulement vers le nord-ouest, recoupés par ceux d’un écoulement majeur vers le sud-est, et ensuite par ceux d’écoulements vers le sud-ouest, le sud et le sud-est, lors de la déglaciation du territoire, témoignent d’une suite complexe d’évènements glaciaires. Le mouvement initial, vers le nord-ouest, résulte d’une zone de partage des glaces d’orientation NE‑SO, située dans les hautes terres du Québec, au sud du lac Mistassini, laquelle se déplaça au nord du lac Mistassini au Pléniglaciaire, pour former l’écoulement vers le sud-est, dont les traces couvrent une grande partie de la province de Grenville. Lors de la dernière déglaciation des ajustements dans le sens d’écoulement des glaces ont engendré des ro...

Glacial and nonglacial events in the eastern James Bay lowlands, Canada

“…Some sections also show evidence for two late-glacial tills. Overall, this provenance change and associated changes in ice-flow directions are in agreement with the ice-flow sequence documented from extensive measurements of striations on rock outcrops in the adjacent Shield region, which is thought to reflect the evolution of the center of outflow of the Labrador-Quebec sector (Veillette et al 1999;Veillette 2004).…”

“…This contrasts significantly with nearby erosional and depositional records. Ice-flow movements documented from striations measured from multifaceted rock outcrops of the nearby Canadian Shield and tracing of glacial lithological indicators of long-distance transport indicate important displacements of the Labrador-Quebec ice divide (e.g., Prest 1963;Veillette and Pomares 1991;Parent et al 1995;Veillette 1995;Veillette et al 1999;Veillette 2004), which presumably record events spanning the ice dome buildup in the early phases of the last glacial cycle to the late stages of the last deglaciation. Furthermore, glacial sequences in the central and northern HBL that show strong similarities with the James Bay stratigraphy record important variations in ice-flow movements that also support a highly dynamic LIS (Nielsen et al 1986;Thorleifson et al 1993).…”

Constraining soil mineral weathering 87Sr/86Sr for calcium apportionment studies of a deciduous forest growing on soils developed from granitoid igneous rocks

“…The study site is situated approximately five kilometers west of a contact zone with anorthosite-orthopyroxene granitoids and southeast of a series of banded granitic gneisses, charnockite gneiss, orthopyroxene granitoids (charnockite, mangerite, jotunite and syenite) and sparse areas of marble (Figure 1). Glacial advance from the north (Veillette, 2004) resulted in a mixing of minerals and rock fragments sampled from the surrounding felsic rocks containing minerals such as quartz, muscovite, plagioclase, Kfeldspar, hornblende and biotite, and marbles containing calcite (Peck et al, 2005 (Barton and Doig, 1977). This age is similar to the U-Pb zircon age of the Morin Anorthosite dated at 1155 ± 3 Ma (Doig, 1991 Rb decay.…”

Principal component analysis of the geochemistry of soil developed on till in Northern Ireland

“…This technique has its roots in mineral prospecting where geochemistry is used to establish the provenance and dispersal pattern of valuable mineral deposits that have underwent transport by ice during glaciation (e.g. Aario & Peuraniemi, 1992;Kauranne, 1958;Klassen, 2001;Klassen & Thompson, 1993;McClenaghan, Thorleifson, & DiLabio, 2000;Parent, Paradis, & Doiron, 1996;Peuraniemi, Aario, & Pulkkinen, 1997;Sarala, Rossi, Peuraniemi, & Ojala, 2007;Veillette, 2004). The geochemical signature of the till is inherited from the bedrock parent material which allows till provenance to be established (Boston, Evans, & Ó 'Cofaigh, 2010).…”