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TitleUnderstanding the Holocene closed-basin phases (lowstands) of the Laurentian Great Lakes and their significance
AuthorLewis, C F M
SourceGeoscience Canada vol. 43, no. 3, 2016 p. 179-197, https://doi.org/10.12789/geocanj.2016.43.102
Year2016
Alt SeriesEarth Sciences Sector, Contribution Series 20150426
PublisherGeological Association of Canada
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceOntario
NTS30; 31C; 31D; 31E; 31F; 31L; 40; 41; 42B; 42C; 42D; 42E; 42F; 42L; 52A; 52B; 52G; 52H; 52I; 52J
AreaGreat Lakes; Lake Superior; Lake Michigan; Lake Huron; Lake Erie; Lake Ontario; Canada; United States
Lat/Long WENS -94.0000 -76.0000 51.0000 41.0000
Subjectshydrogeology; geochronology; environmental geology; surficial geology/geomorphology; Holocene; basin analysis; surface waters; lakes; water levels; shoreline changes; isostatic rebound; radiometric dating; radiocarbon dating; carbon-14 dates; hydrologic environment; paleoclimatology; paleodrainage; glacial history; glaciation; deglaciation; glacial lakes; postglacial evolution; vegetation; raised beaches; glacial deposits; glaciolacustrine deposits; clays; Glacial Lake Algonquin; Laurentide Ice Sheet; Glacial Lake Iroquois; Glacial Lake Whittlesey; Glacial Lake Wisconsin; Glacial Lake Minong; climate change; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; schematic representations; geoscientific sketch maps; photographs; seismic profiles; correlation sections; histograms; profiles; time series; plots
ProgramLand-based Infrastructure, Climate Change Geoscience
Abstract(Summary)
The Laurentian Great Lakes are a chain of five large water bodies and connecting rivers that constitute the headwaters of the St. Lawrence River. Collectively they form one of the largest reservoirs of surface freshwater on the planet with an aggregate volume of >22,000 km3. Early interpretations of the postglacial lake history implicitly assumed that the Great Lakes always overflowed their outlets. A study of Lake Winnipeg which concluded that lack of water in a dry climate had dried that lake for millennia led to re-evaluation of the Great Lakes water-level history. Using the empirical information of glacio-isostatic rebound derived from 14C-dated and uptilted Great Lake paleo-shorelines, a method of computation was developed to test the paradigm of continuous lake overflow. The method evaluated site and outlet uplift independently, and low-level indicators such as submerged tree stumps rooted beneath the present Great Lakes were found to be lower than the lowest possible corresponding basin outlet. Results confirmed the low-level, closed-basin hydrological status of the early Great Lakes. This status is consistent with paleoclimatic inferences of aridity during the early Holocene before establishment of the present patterns of atmospheric circulation which now bring adequate precipitation to maintain the overflowing lakes. In a sense, the early to middle Holocene phase of dry climate and low water levels is a natural experiment to illustrate the sensitivity of the Great Lakes to climate change in this era of global warming, should their climate shift to one much drier than -present, or future major diversions of their waters be permitted.
Summary(Plain Language Summary, not published)
Early interpretations of the postglacial lake-level history implicitly assumed that the Laurentian Great Lakes always overflowed their outlets. Re-evaluation of these lakes was undertaken after it was found that Lake Winnipeg had dried for millennia. A method of computation was developed to test and disprove the assumption of continuous lake overflow. Site and outlet uplift were evaluated independently, and low-level indicators such as submerged tree stumps rooted beneath the present Great Lakes were found to be lower than the lowest possible corresponding basin outlet. Results confirmed the low-level, closed-basin hydrological status of the early Great Lakes. This status was consistent with paleoclimatic inferences of aridity during the Early Holocene In a sense, the Early to Middle Holocene phase of dry climate and low water levels is a natural experiment to illustrate the sensitivity of the Great Lakes to climate change in this era of global warming, should their climate shift to one much drier than present.
GEOSCAN ID297577