| Titre | High-resolution varve sequences record one major late-glacial ice readvance and two drainage events in the eastern Lake Agassiz-Ojibway basin |
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| Auteur | Godbout, P -M; Roy, M; Veillette, J J |
| Source | Quaternary Science Reviews vol. 223, 105942, 2019 p. 1-18, https://doi.org/10.1016/j.quascirev.2019.105942 |
| Image |  |
| Année | 2019 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20190559 |
| Éditeur | Elsevier |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.quascirev.2019.105942 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Ontario; Québec |
| SNRC | 32C; 32D; 32E; 32F; 42A; 42H |
| Lat/Long OENS | -82.0000 -77.0000 50.0000 48.0000 |
| Sujets | evolution du bassin; antecedents glaciaires; glaciation; écoulement glaciaire; déglaciation; marges glaciaires; lacs glaciaires; varves; rythmites; silts; antecedents de sedimentation; paléodrainage;
corrélations stratigraphiques; épaisseur des sediments lacustres; essais d'ignition; analyses granulométriques; diagraphie géophysique; susceptibilité magnétique; Lac glaciaire d'Ojibway; Lac glaciaire d'Agassiz; Calotte glaciaire Laurentide;
sédiments glaciolacustres; géologie des dépôts meubles/géomorphologie; stratigraphie; géochimie; sédimentologie; géophysique; Nature et environnement; Sciences et technologie; Phanérozoïque; Cénozoïque; Quaternaire |
| Illustrations | cartes géolscientiques généralisées; photographies; profils; diagraphies géophysiques; corrélations stratigraphiques |
| Diffusé | 2019 09 24 |
| Résumé | (disponible en anglais seulement)
Lake Ojibway developed at the southern Laurentide Ice Sheet margin during the last deglaciation and covered vast expanses of northeastern Ontario and
northwestern Quebec (Canada). The late-stage history of the lake is complex, presumably marked by a coalescence with Lake Agassiz and by late-glacial ice readvances into the basin shortly before its final drainage ~8200 years ago. However, these
events are poorly defined in the Lake Ojibway varve record. Here we present evidence for the occurrence of one major ice readvance and two distinct drainage events from two varve sequences in northwestern Quebec. The Matagami section contains 231
varves that comprise an interval recording a late-glacial (Cochrane) ice readvance. The La Reine section spans 100 varves and the base of the sequence is characterized by a set of chaotic and coarse-grained (silty) rhythmites that marks the first
lake drainage. These bottom rhythmites are overlain by a set of 65 thick varves, which are in turn capped by a thick silt bed associated with the final drainage of Lake Ojibway. Varve thickness measurements allow the correlation of these sections
with the main Ojibway varve record that spans ~2129 years in the region (where varve 1 represents the start of sedimentation). The Matagami sequence covers varve years 1644-1874 and the onset of the Cochrane readvance occurred in varve year 1817. The
lower part of the La Reine sequence below the bottom chaotic rhythmites was deposited between varve years 1843-1877, while the overlying set of thick varves is correlated to varve years 2065-2129, thus indicating a hiatus of 188 varves. The distinct
thick varves show strong compositional and stratigraphic similarities with the Connaught sequence reported elsewhere in the basin and point to a connection with the late-glacial (Cochrane) ice dynamics, which appear to have played an important role
on the lake evolution. These results indicate that the late-stage history of Lake Ojibway was marked by the already known Cochrane major ice readvance which was followed by two drainage events separated by at least 65 years, consistent with North
Atlantic sediment records that document a two-step drainage of Lake Agassiz-Ojibway. |
| GEOSCAN ID | 321878 |
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