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TitreEffects of marine inundation on till composition in permafrost terrain south of Wager Bay, central mainland Nunavut
AuteurRandour, I; McMartin, I; Roy, M
SourceGAC-MAC 2017; Association géologique du Canada-Association minéralogique du Canada, Réunion annuelle, Programme et résumés vol. 40, 2017 p. 323
Année2017
Séries alt.Secteur des sciences de la Terre, Contribution externe 20160448
ÉditeurAssociation géologique du Canada
RéunionGeological Association of Canada-Mineralogical Association of Canada Joint Annual Meeting 2017; Kingston, ON; CA; mai 14-18, 2017
Documentpublication en série
Lang.anglais
Mediapapier; en ligne; numérique
Formatspdf
ProvinceNunavut
SNRC56B; 56C
Sujetséchantillons de till; prospection minière; exploration de dépôts glaciaires; dépôts glaciaires; géochimie des dépôts glaciaires; pergélisol
ProgrammeTehery-Wager Bay de la province de Rae, GEM2 : La géocartographie de l'énergie et des minéraux
LiensOnline - En ligne
Résumé(disponible en anglais seulement)
In northern Canada, systematic till sampling in frost boils is an exploration technique commonly used to find commodities of economic value. Post-depositional alteration can modify the so-called first order sediment, leaving a less suitable sediment for drift prospecting. Below the post-glacial limit of marine invasion, reworking and winnowing processes by waves and currents may remove the fine fraction of till, whereas the incorporation of fine-grained marine sediments may dilute the signature from local bedrock, leaving a completely different material from till collected above the marine limit. A detailed study to evaluate the effects of the post-glacial marine processes on till texture and geochemical composition was initiated in the summer of 2016 at two separate sites in central mainland Nunavut (NTS 56B and NTS 56C) in paired frost boils located on either sides of the well-defined local marine limit. The sampling sites were carefully chosen using airphoto interpretation and ground truthing observations, concentrating on the presence of thick till above and below the marine trimline, and continuous bedrock units along the trimline. The first site is characterized by intensely wave-washed surfaces surrounded by bouldery beaches forming a distinct trimline with unmodified till-covered surfaces above; the second site forms a clear trimline around a small topographic high forming wave-cut notches between intact till above and reworked till below the marine limit. For each site, two frost boils were sampled; one was located immediately below the marine limit and the other directly above. Several samples were collected from each frost boil along a vertical profile at 10-15 cm intervals, down to 95 cm maximum depth. Five small field duplicate samples were also collected near each frost boil at approximately 40 cm depth to measure the local variability. A total of 54 small (~3 kg) samples were collected for this study. Geochemical and textural analyses were performed on the samples to evaluate variations with depth and between sites. The results presented here in detailed profiles from frost boils above and below the marine limit will help assess the impact of marine invasion on till composition in soils affected by cryoturbation.
Résumé(Résumé en langage clair et simple, non publié)
Les plaines côtières au nord-ouest de la Baie d'Hudson ont été envahies par la mer postglaciaire suite à la dernière déglaciation. Ce poster présente les résultats d'une étude sur la composition des sédiments de surface prélevés au-dessus et au-dessous de la limite marine dans des ostioles de toundra. Les résultats vont permettre de caractériser la nature des sédiments de surface potentiellement remaniés par les processus marins et vont aider à l'évaluation des effets de l'invasion marine sur la composition des tills en terrain pergélisolés, qui sont couramment échantillonnés en exploration minérale. Cette étude fait partie d'une thèse de maîtrise amorcée dans le cadre de la composante en géologie de surface de l'activité de GEM 2 Tehery-Wager du Projet Rae.
GEOSCAN ID300222