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

Abstract

Marine and continental records indicate that the Laurentide Ice Sheet (LIS) was highly dynamic throughout the last glacial cycle, with significant reorganizations of its ice divide system. The extensive depositional record of the Hudson Bay lowlands (HBL) is particularly important for the study of ice sheet dynamics because this region was once located near two important ice domes of the LIS. However, important stratigraphic issues remain in the HBL, notably regarding the chronology of nonglacial units and the direction and extent of the ice-flow events recognized. Here we focus on the northeastern sector of the LIS by documenting the provenance of tills and dating nonglacial deposits in sedimentary sequences east of James Bay. Our investigations indicate that the regional stratigraphy comprises at least five distinct tills and an important unit of glaciolacustrine rhythmites. This glacial sequence lies on massive lacustrine clay and fluvial sand containing abundant organic debris and wood fragments. The clast lithology and matrix geochemistry of tills show significant variations that are consistent with the ice-flow movements deduced from clast fabric measurements. Taken together, the till compositional and fabric data suggest an early westward ice flow, followed by a counterclockwise shift to a west-southwest, southwest, and then south-southeast ice flows. Luminescence dating of waterlaid sediments outlines a complex and fragmentary stratigraphic record, which comprises two distinct nonglacial units belonging to the last and penultimate interglaciations. These results and stratigraphic considerations indicate that the documented ice-flow rearrangements likely occurred during the last glacial cycle.Résumé : Les données géologiques marines et continentales indiquent que l'inlandsis Laurentidien était très dynamique durant le dernier cycle glaciaire et qu'il a été marqué par d'importantes modifications de la géométrie de ses lignes de partage des glaces. Les nombreux enregistrements sédimentaires des basses terres de la baie d'Hudson sont particulièrement importants pour l'étude de la dynamique des inlandsis puisque cette région a déjà été située à proximité de deux grands dômes de glace de l'inlandsis. Toutefois, il reste des questions stratigraphiques significatives dans les basses terres de la baie d'Hudson, notamment en ce qui concerne la chronologie des unités non glaciaires ainsi que la direction et l'étendue des écoulements glaciaires reconnus. Nous ciblons ici le secteur nord-est de l'inlandsis Laurentidien en documentant la provenance des tills et en datant les dépôts non glaciaires dans les séquences sédimentaires à l'est de la baie James. Nos recherches indiquent que la stratigraphie régionale comporte au moins cinq tills distincts et une unité importante de rythmites glacio-lacustres. Cette séquence glaciaire repose sur une argile lacustre massive et du sable fluviatile contenant d'abondants débris organiques et fragments de bois. La lithologie des clastes et la géochimie de la matrice des tills montre...

Constraining the Late Pleistocene history of the Laurentide Ice Sheet by dating the Missinaibi Formation, Hudson Bay Lowlands, Canada

“…Deposits dating to MIS 5 are situated along the Nottaway and Nelson Rivers, and have been described by Allard et al (2012), Dubé-Loubert et al (2013) and Roy (1998) (Fig. 4).…”

“…Despite these issues, previous attempts to constrain the age of the Missinaibi Formation have resulted in the recognition of at least one MIS 5 (ca. 130,000 to 71,000 yr BP) site via U-Th and OSL dating (Allard et al, 2012;Dubé-Loubert et al, 2013), which is correlative to the penultimate interglacial period. Given the substantial glacial retreat during the MIS 5 period (Andrews and Dyke, 2007;NEEM community members, 2013), such deposits can be expected.…”

“…Bajc et al, 2009;Bajc et al, 2015;Rémillard et al, 2013), and for which the western extent is unknown, and (3) a strong agreement between low RSL during MIS 3 and the lack of marine deposits in the Missinaibi Formation. Future iterations of relevant Earth system models should include land-based information of the layout and configuration of previous ice sheets, along with results from till correlations (Dubé-Loubert et al, 2013;Kaszycki et al, 2008;Nguyen, 2014), geomorphic evidence of ice flow regimes (Kleman et al, 2010;Veillette et al, 1999) and models of ice volume (Peltier et al, 2015).…”

“…Andrews et al, 1983;Nielsen et al, 1986;Shilts, 1982;Wyatt, 1989) are not included in this compilation because they were incorporated and resided within the glacier for an unknown amount of time where racemization may have ceased or slowed down (Barnett, 1992). -Loubert et al, 2013).…”

“…Fréchette and de Vernal, 2013;Karrow et al, 2001), is not preserved in the non-glacial sediments of the HBL at sites presented here. Instead, OSL data from the Nottaway River, and one TL age from the Nelson River correspond to the latter part of the MIS 5 interglaciation (Allard et al, 2012;Dubé-Loubert et al, 2013;Roy, 1998).…”