Émersion des terres et développement des sols bien drainés au lac Guillaume-Delisle, Québec subarctique
In the Lake Guillaume-Delisle area, alluvial fans of various ages and elevations were deposited throughout the Holocene over raised beach deposits, which allowed the studying of a subarctic soil chronosequence. The temporal framework is based on 38 14C dates obtained from buried organic soil horizon...
| Published in: | Géographie physique et Quaternaire |
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| Main Authors: | , , |
| Format: | Text |
| Language: | French |
| Published: |
Les Presses de l'Université de Montréal
2006
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| Subjects: | |
| Online Access: | https://doi.org/10.7202/016827ar http://id.erudit.org/iderudit/016827ar |
| Summary: | In the Lake Guillaume-Delisle area, alluvial fans of various ages and elevations were deposited throughout the Holocene over raised beach deposits, which allowed the studying of a subarctic soil chronosequence. The temporal framework is based on 38 14C dates obtained from buried organic soil horizons, and on an update of the Lake Guillaume-Delisle emersion curve. Postglacial uplift due to glacio-isostatic rebound occurred at a mean rate of 5.6 m/century from 8500 to 4500 cal. yr BP, and of 1.2 m/century after 4500 cal. yr BP. Soil morphology and chemistry showed that well-drained sandy soil and paleosoil development, when not influenced by late-lying snowpatches and snowmelt, is characterized by B horizons having a dominant accumulation product of amorphous material composed mainly of humified organic matter combined with Al and Fe (podzolisation). However, pedogenic development is weak and would take about 12 400 years to reach the minimum values of (Fep+Alp) ≥0,4% required for meeting the criteria of a Bf horizon in the Canadian system of soil classification, according to a linear function. Although theoretical, this value indicates that conditions required for Podzol formation are hard to reach in subarctic soils with low vegetation and thin snow cover. Dans la région du lac Guillaume-Delisle, au Québec subarctique, des cônes de déjection d’âge et d’altitude variables se sont déposés tout au cours de l’Holocène sur des plages soulevées, offrant ainsi la possibilité d’étudier une chronoséquence holocène de sols. Le cadre temporel a été établi par la datation radiocarbone de 38 horizons organiques enfouis et la mise à jour de la courbe d’émersion des terres pour la région. L’émersion se serait effectuée selon un taux moyen de 5,6 m/siècle entre 8500 et 4500 années cal. BP et de 1,2 m/siècle après 4500 années cal. BP. Les analyses morphologiques et chimiques ont montré que les sols et paléosols subarctiques sableux, bien drainés et soustraits à l’influence des combes à neige, sont formés principalement par ... |
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