EGU22-2701, updated on 27 Mar 2022
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Islands of proglacial lake Ojibway acted as outposts favoring postglacial forest migration in northwestern Québec

Marianne Vogel1,2, Adam A. Ali1, Sébastien Joannin1, Yves Bergeron3, and Hugo Asselin4
Marianne Vogel et al.
  • 1ISEM, Univ Montpellier, CNRS, IRD, Montpellier, France
  • 2IRF, Université du Québec en Abitibi-Témiscamingue (UQAT)
  • 3NSERC-UQAT-UQAM Industrial Research Chair in Sustainable Forest Management
  • 4NSERC, Industrial Chair in Sustainable Forest Management, School of Indigenous Studies, UQAT, Rouyn-Noranda, Canada

At the beginning of the Holocene, the Laurentide Ice Sheet was progressively melting and liberating Canadian landscapes. Proglacial Lake Ojibway formed at the contact of the glacier and covered western Québec and eastern Ontario for approximately 2000 years before flushing into James Bay around 8,200 years ago. Lake Ojibway could have limited the afforestation of newly liberated landscapes but could have also provided migratory outposts on its islands. Indeed, several islands were present on Lake Ojibway which could have been colonized by forests before the drainage of lake Ojibway. We studied lake sediments from a small lake located on a paleo-island of Lake Ojibway in Aiguebelle National Park, in order to test the outpost hypothesis. Radiocarbon dating, XRF analysis and charcoal analysis reveal that organic matter (gyttja) started to accumulate around 9,626 years before today (i.e., 1400 years before Lake Ojibway retreat). The signatures of Ca, Sr and Si indicate that soil erosion declined between 9500 and 9000 years before present, meaning this paleo-island was probably colonized during this interval as vegetation stabilizes the soils. Moreover, K (an indicator of vegetation extension) also suggests that afforestation occurred around 9,250 years before present. Macroscopic charcoal particles reveal that one local fire likely occurred 9239 years before present. Burned conifer needle fragments were found among the fossil charcoals, lending support to the hypothesis of wildfire occurrence. All the studied indicators suggest paleo-island colonization around 9,250 years before present, more than 1,000 years before Lake Ojibway retreat.

How to cite: Vogel, M., Ali, A. A., Joannin, S., Bergeron, Y., and Asselin, H.: Islands of proglacial lake Ojibway acted as outposts favoring postglacial forest migration in northwestern Québec, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2701,, 2022.


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