Abstract
We present a multi-proxy study of environmental conditions during and after the recessional phases of pro-glacial Lake Algonquin in the vicinity of the North Bay outlet, Great Lakes Basin. Data presented comes from a new sedimentary profile obtained from the Balsam Creek kettle lake c. 34 km north-east of the city of North Bay. This site lies close to the north-east margin of the maximum extent of the post-Algonquin lake sequence, which drained through the Ottawa-Mattawa valley system. Our data are presented against a Bayesian age-depth model, supporting and extending regional understanding of vegetation succession in this part of north-east Ontario. The core profile provides a minimum age for the formation of the glacial outwash delta in which the kettle is set, as well as tentative timing for the Payette (post-Algonquin) lake phase. We highlight two discrete intervals during the Early Holocene, with modelled mean ages of: 8475–8040 cal. BP (332–316 cm) and 7645 cal. BP (286 cm), when climatic aridity affected the growth of vegetation within the kettle vicinity. Association with volcanic activity is posited. Cryptotephra dating to 7660–7430 cal. BP (mean age: 7580 cal. BP) is chronologically and geochemically assigned to the Mazama climactic eruption, while an earlier ash accumulation 8710–7865 cal. BP is tentatively sourced to an unknown eruption also in the Cascades region of Oregon. Outside of these periods, the Balsam Creek sequence shows considerable habitat stability and a character akin to that seen at more southerly latitudes. On this evidence we propose that access to reliable resources within kettle features could have aided the initial colonisation of northern Ontario’s environmentally dynamic early post-glacial landscape.
Highlights
The sequence of pro-glacial lakes that formed in front of the decaying Laurentide ice-sheet have been a subject of study since the late nineteenth century (Spencer 1891) when the evidence for continental glaciation became widely accepted, and supported by the documentation of tilted shorelines in all of the Great Lakes basins
For this study we considered that the location could provide a valuable point of reference within the dynamic Early-Mid Holocene inter-lacustrine deglacial environments that existed between Lake Barlow expanding to the north, and the post-Algonquin lakes to the west and south of the delta
These dates attest that the depositional sequence recovered from the Balsam Creek kettle lake tracks vegetation succession from soon after local deglaciation
Summary
The sequence of pro-glacial lakes that formed in front of the decaying Laurentide ice-sheet have been a subject of study since the late nineteenth century (Spencer 1891) when the evidence for continental glaciation became widely accepted, and supported by the documentation of tilted shorelines in all of the Great Lakes basins. North Bay was given notable attention because of its proximity to the Lake Algonquin outlet It would be the completion of country-wide coverage by aerial photographs after the Second World War that proved crucial to the reconnaissance mapping by Boissonneau (1968) of the soils and geomorphic features of the large area from Lake Superior to the Quebec border and from Lake Huron north to latitude 48°30’.
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