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TitleEvidence of extreme lake level lowstand in the Georgian Bay Lake Basin
AuthorBlasco, S M; Lewis, C F MORCID logo; Harmes, R A; McCarthy, F M G
SourcePast, present, and future, 50th Conference on Great Lakes research, Book of abstracts; 2007 p. 12-13
Alt SeriesEarth Sciences Sector, Contribution Series 20070271
PublisherInternational Association for Great Lakes Research
Meeting50th Great Lakes conference; University Park, PA; US; May 28 - June 1, 2007
NTS41A; 41H
AreaGeorgian Bay; Lake Huron
Lat/Long WENS-82.0000 -80.0000 46.0000 44.0000
Subjectshydrogeology; geophysics; hydrographs; hydrologic budget; hydrography; drainage patterns; drainage systems; flow regimes; biostratigraphy; basins; basin analysis; glacial deposits; water levels; geophysical surveys; bathymetry; Holocene; sedimentation; paleoenvironment; limnology; Great Lakes Basin; Cenozoic; Quaternary
ProgramEnhancing resilience in a changing climate
AbstractInterpretation of integrated geophysical, geological and biostratigraphic data from the Georgian Bay lake basin indicates lake levels were at least 50m lower than today prior to 7500 BP. Evidence for extreme low stand includes beach ridges at -53 m and significant basin wide erosion of lakebed proglacial and postglacial sediments with channelization of the surface of these eroded sediments below 80m water depths. The water plane that existed across the basin at extreme lowstand is reconstructed by adjusting for differential isostatic rebound. The distribution of incised channels indicates lowstand water flow was to the northeast, exiting over the Dallas sill and out the North Bay outlet. Subsequent Holocene sediment deposition is not controlled by basin bathymetry. The eroded channels are preferentially infilled with Holocene sediments while the deepest waters of Georgian Bay lack Holocene sediment accumulation. The Holocene sediment distribution pattern across the basin would suggest extreme lowstand was associated with dynamic shallow water conditions that controlled deposition. Since 7500BP and the rise in lake level from extreme lowstand, the lakebed has been stable with little recent sediment accumulation.

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