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TitleMarine geoscience and lakes
AuthorLewis, C F M; Todd, B J; Blasco, S M; Forbes, D L; Cameron, G D M; King, E L
SourceVoyage of Discovery: fifty years of marine research at Canada's Bedford institute of Oceanography; by Nettleship, D N (ed.); Gordon, D C (ed.); Lewis, C F M (ed.); Latrémouille, M P (ed.); 2014 p. 225-230
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20130158
PublisherBedford Institute of Oceanography
File formathtml
ProvinceOntario; Nova Scotia; Manitoba
NTS30L; 30M; 30N; 40I; 40J; 40O; 40P; 41; 42D; 52A; 62I; 62P; 63A; 63B; 63G; 63H; 11F; 11K
AreaGreat Lakes; Lake Erie; Lake Ontario; Lake Simcoe; Lake Superior; Lake Michigan; Lake Huron; Lake Bedford; Lake Banook; Lake Winnipeg
Lat/Long WENS -92.0000 -76.0000 49.5000 41.0000
Lat/Long WENS -61.5000 -60.5000 46.2500 45.7500
Lat/Long WENS -99.5000 -96.0000 54.0000 50.2500
Subjectshydrogeology; surficial geology/geomorphology; geophysics; Nature and Environment; acoustic surveys; acoustic surveys, marine; glacial lakes; seismic surveys, lake; isostatic rebound; deglaciation; seismic risk; seismic surveys; seismic profiles; bathymetry
Illustrationslocation maps; profiles; photographs; models
ProgramOffshore Geoscience, Program management
AbstractStudies of the Great Lakes and Lake Winnipeg were undertaken during the 1990 and 2000 decades using the methods of marine and coastal geoscience. Expeditions were commonly conducted with collaborators to address societal concerns. Lake Ontario sediments and bedrock were surveyed for evidence of recent deformation and earthquake shaking, natural processes that pose concern for safety of nuclear power stations. Popups of surface bedrock were clearly buckled by compressive stress, but were found to relate more to glacial rebound and far-field tectonic stresses than earthquake stress. Glacial lake sediments under postglacial silty clay mud were imaged in most lakes, in places overlying drumlins, tunnel valleys, and moraines. Large shifts in the isotopic composition of fossils in lake sediments revealed new insights into the paleo-hydrology of the deglaciation. Studies in Lake Winnipeg implied that long term progressive lake-level rise resulting from differential glacial rebound of the lake’s northern outlet enhanced shore erosion, a result that countered previous concerns that lake-level regulation for power generation was a cause of shore property losses. Submerged tree stumps and evidence of erosion beneath postglacial lake sediments indicated former low-lake levels in the Laurentian Great Lakes. Although the low water levels were initially thought to have resulted solely from tilting of lake basins by differential glacial rebound, it was discovered that the lakes had also descended metres to tens of metres as a result of intensive early to middle Holocene evaporation, a finding that underlined the susceptibility of large lakes to climate change.
Summary(Plain Language Summary, not published)
The shape and sediments of the Great Lakes of North America, and of Lake Winnipeg, Manitoba, were examined with seismic reflection methods (similar to echo sounding), piston core sampling, and occasionally by submersible viewing. Major findings showed that possible faults and zones of instability beneath Lake Ontario were benign effects of the last glaciation and the dumping of ash during the steamship era. Variations in the isotopic composition of fossils in the sediments of lakes Huron and Michigan were found to result from alternating conditions of isolation and meltwater overflow from northern glacial lakes during late stages of the last deglaciation. When Lake Winnipeg was found to have nearly dried up prior to 4000 years ago, a re-examination and synthesis of evidence of low water levels in the Great Lakes showed that these too had evaporated below their outlets during a past interval of dry climate, proving an example of the sensitivity of these large lakes to climate change.