The Saint-Narcisse morainic complex and early Younger Dryas events on the southeastern margin of the Laurentide Ice Sheet

Abstract

The Saint-Narcisse morainic complex extends over 750 km along the southern margin of the Laurentian Highlands in Québec, north of the St. Lawrence Valley, between the Ottawa and Saguenay Rivers. To the east, the Laurentide Ice Sheet margin was located in the present St. Lawrence Estuary. To the west, the morainic complex is extended 235 km west of the Ottawa River to the Algonquin Highlands, in Ontario. The general outline of the morainic complex comprises large lobes and reentrants, related to major topographic features. In the lower Saint-Maurice River area, the moraine is composed of reworked clay and till and proximal glaciomarine deposits (Yamachiche Diamicton) and melt-out till and ice-marginal outwash (Charette Drift). The Saint-Narcisse Event can be subdivided in several phases: local readvance in low areas, main phase at the origin of the Saint-Narcisse Moraine s.s., melting-out of the marginal ice with compressive structures and large proglacial outwash features, and slow retreat with secondary ridges. The accuracy of the chronological data is limited by several factors: and a floating chronology is proposed. Two landmarks constrain the age and range of duration of the main Saint-Narcisse phase. The main ridge deposition occured after the onset, ca. 12.9 cal ka, of Champlain Sea in the St. Lawrence Valley, and a rapid ice retreat on the southern edge of the Laurentians. It ended before the drawdowm, in the Lake Huron basin, of Glacial Lake Algonquin ca. 12.5 cal ka. The Saint-Narcisse Event is related to the early cold phase of Younger Dryas, as evidenced by other YD ice readvances in Maine, Nova Scotia, and ice cover on the Gaspé Peninsula. It corresponds to a positive change of the budget of the Laurentide Ice Sheet as a result of climate forcing. After a slow ice front retreat during about 900-700 yr, the final phase of YD is marked by the Mars-Batiscan Moraine, located 17 to 70 km north of the Saint-Narcisse Moraine.Le complexe morainique de Saint-Narcisse s’étend sur 750 km le long de la marge méridionale des Laurentides, au Québec, au nord de la vallée du Saint-Laurent, entre l’Outaouais et le Saguenay. Vers l’est, la marge glaciaire était située dans l’estuaire actuel du Saint-Laurent. Vers l’ouest, en Ontario, les formes associées sont suivies dans le massif Algonquin, jusqu’à 235 km de l’Outaouais. Le tracé général du complexe inclut de grands lobes et rentrants liés à la topographie. Dans la basse vallée du Saint-Maurice, la Moraine de Saint-Narcisse est composée de dépôts glaciomarins proximaux, de till et d’argile marine remaniée (Diamicton de Yamachiche) et de till de fusion sur place et de dépôts fluvioglaciaires et juxtaglaciaires (Dépôts de Charette). L’Épisode de Saint-Narcisse est subdivisé en plusieurs phases non nécessairement synchrones sur toute la marge glaciaire: réavancée locale dans les dépressions importantes, phase majeure de stabilisation à l’origine de la Moraine de Saint-Narcisse, fonte sur place indiquée par des structures imbriquées et épandages proglaciaires, puis retra...

Sedimentary imprints of former ice-sheet margins: Insights from an end-Ordovician archive (SW Libya)

“…Based on the late Quaternary record, evidencing glaciotectonic foldand-thrust belts upstream of a proglacial depositional wedge would appear to be a useful criterion for the recognition of ice-marginal wedges (Lønne, 1995;Davies et al, 1997;Occhietti, 2007). Admittedly, well-developed glaciotectonic fold-and-thrust belts may only characterise continental to very shallow glaciomarine settings.…”

“…Changes in the position of the ice-margin related to advance and retreat phases were less than a few tens of kilometres, compared with the at least 2000 km retreat of the end-Ordovician icesheet fronts at the scale of the overall deglaciation (Ghienne et al, 2007b;Le Heron and Craig, 2008;Loi et al, 2010). Considering that the Upper Glaciogenics developed during a fraction of Hirnantian time (≪1 Ma, Ghienne et al, 2014), and based on the size and thickness of the studied ice-marginal wedge and analogies with Quaternary case studies (e.g., Powell and Cooper, 2002;Shaw et al, 2006;Occhietti, 2007;Jakobsson et al, 2012), durations of a few thousands of years can be reasonably estimated for the built-out duration of the Tihemboka sedimentary wedge. Such a duration is almost instantaneous relative to the Ordovician time scale.…”

“…Their recognition in the sedimentary record and that of related ice-sheet margins, at macro-and micro-scales, are crucial to the interpretation of ice-sheet extent or to the understanding of icemarginal oscillations including diachronous ice-front stillstands as well as of links between glacier dynamics and climate (Powell and Cooper, 2002;Occhietti et al, 2011). Preserved glacial landsystems that have contributed to their characterisation in the Quaternary record (Shaw et al, 2000;Boulton et al, 2001;Lajeunesse and Allard, 2002;Ottesen et al, 2005;Boulton and Hagdorn, 2006;Occhietti, 2007;Evans, 2009;Winsemann et al, 2009;Jakobsson et al, 2012) are usually lacking for the identification of pre-Pleistocene ice-marginal systems. This is a severe limitation in our capacity to untangle former ice-sheet extents in deep time and in our capacity to propose sequence stratigraphic scenarios for related recessional ice-front development, whose associated deposits are nevertheless amongst the most abundant in the Earth glacial sedimentary record (Moncrieff and Hambrey, 1990;dos Santos et al, 1996;Von Brunn, 1996;Le Heron et al, 2006;Ghienne et al, 2007b).…”

Long-term base cation weathering rates in forested catchments of the Canadian Shield

“…The maximum and minimum numbers of years since the retreat of the Laurentian Ice Sheet are shown. The Saint-Narcisse morainic complex and the Mars-Batiscan moraine together with the main and late Younger Dryas isochrones of the Laurentide Ice Sheet ice margin are from Occhietti (2007). gradient between the northern temperate subzone of Quebec and the lower boreal subzone, so that the vegetation ranges from deciduous forests dominated by sugar maple (Acer saccharum Marsh.)…”

“…1). The position of each watershed was first located on a geomorphological map containing the isochronous lines for the retreat of the Laurentian Ice Sheet together with the position of the Mars-Batiscan Moraine and the Saint-Narcisse morainic complexes, dated at 11,400 and 12,900 years before present, respectively (Occhietti, 2007). Because only two reference dates were available, an interpolation algorithm could not be used.…”