The international structure of a pala and a peat plateau in the Rivière Boniface region, Québec: Interferences on the formation of ice segregation mounds
The internal structure of a 5.7 m high palsa was studied through a pattern of closely spaced drill holes in permafrost along two orthogonal section lines. Holes were also drilled on a 1.3 m high peat plateau along a topographic transect for comparison purposes. The morphology of the palsa closely re...
| Published in: | Géographie physique et Quaternaire |
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| Main Authors: | , |
| Format: | Text |
| Language: | English |
| Published: |
Les Presses de l'Université de Montréal
1999
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| Subjects: | |
| Online Access: | http://id.erudit.org/iderudit/004760ar https://doi.org/10.7202/004760ar |
| Summary: | The internal structure of a 5.7 m high palsa was studied through a pattern of closely spaced drill holes in permafrost along two orthogonal section lines. Holes were also drilled on a 1.3 m high peat plateau along a topographic transect for comparison purposes. The morphology of the palsa closely reflects the shape of the ice-rich core heaved by the growth of thick ice lenses in thick marine clay silts of the Tyrrell Sea. During and since palsa growth, the sand and peat covering was deformed by gelifluction and sliding and was also partly eroded by overland flow and wind. Palsa growth was accompanied by the formation of numerous ice-filled fault planes in the frozen sediments. The peat plateau was heaved to a lower height through the formation of thin ice lenses in an underlying layer of sandy silt only 1.4 m thick; this sediment is believed to be of intertidal origin. Therefore, the local Quaternary geomorphological settings are at the origin of differences in morphology and size between the palsa and the peat plateau. General inferences for the development of palsas and like landforms are made from the findings of the study. La structure interne d'une palse de 5,7 m de haut a été étudiée à la suite d'une série de forages réalisés dans le pergélisol le long de deux profils topographiques orthogonaux. À des fins de comparaison, des forages ont aussi été réalisés sur un plateau palsique haut de seulement 1,3 m le long d'un profil topographique. La morphologie de la palse épouse presque la forme de son noyau de pergélisol riche en glace. La palse a grossi consécutivement à la croissance de lentilles de glace épaisses dans un sédiment de fond marin épais (Mer de Tyrrell) et de texture argilo-silteuse. Pendant la croissance de la palse et subséquemment, la couverture de sable et de tourbe a été déformée à la suite de glissements et par gélifluxion elle fut aussi partiellement érodée par le ruisselement et par le vent. La croissance de la palse est associée à la formation de nombreuses failles remplies de glace ... |
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