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TitleThe Early Lake Ontario barrier beach: evidence for sea level about 12.8-12.5 cal. ka BP beneath western Lake Ontario in eastern North America
AuthorLewis, C F MORCID logo; Todd, B JORCID logo
SourceBoreas 2018 p. 1-20, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20180103
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®); docx (Microsoft® Word®); html
ProvinceOntario; Quebec
NTS30M; 30N; 31B; 31C; 31D; 31E; 31F; 31G; 40O; 40P; 41A; 41B; 41G; 41H
AreaLake Ontario; Lake Huron; St. Lawrence River; New York State; Lake Champlain; Canada; United States of America
Lat/Long WENS -84.0000 -74.0000 46.0000 43.0000
Subjectssurficial geology/geomorphology; geophysics; geochronology; Nature and Environment; Holocene; barrier beaches; paleo-sea levels; shoreline changes; lakes; water levels; glacial history; glaciation; deglaciation; geophysical surveys; seismic reflection surveys; piston cores; paleodrainage; marine sediments; sands; gravels; muds; glacial deposits; postglacial deposits; isostatic rebound; crustal uplift; erosion; sediment dispersal; paleoclimates; paleohydrology; glacial lakes; bathymetry; flow regimes; lithology; radiometric dating; radiocarbon dating; hydraulic analyses; Early Lake Ontario; Champlain Sea; Laurentide Ice Sheet; Glacial Lake Algonquin; Glacial Lake Agassiz; Lake Ontario Basin; Glacial Lake Iroquois; Duck-Galloo Ridge; marine beach sediments; lacustrine sediments; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; geoscientific sketch maps; geological time charts; seismic reflection profiles; tables; profiles; time series
ProgramClimate Change Geoscience Coastal Infrastructure
Released2018 10 29
AbstractAn overstepped, concave-eastward, barrier beach beneath Holocene mud in western Lake Ontario has been delineated by acoustic and seismic reflection profiles and piston cores, and related to Early Lake Ontario (ELO). The average ELO barrier depth below present mean lake level is 77.4 to 80.6 m, or about -6 to -2.8 m above present sea level. Trend surface analysis of Champlain Sea (Atlantic Ocean) marine limits defined the contemporaneous marine water surface, and projections of this surface pass ~25 m above the outlet sill of the Lake Ontario basin and extend to the ELO palaeo-barrier, a unique sand and gravel deposit beneath western Lake Ontario. ELO was connected to the Champlain Sea above the isostatically rising outlet sill for up to three centuries after about 12.8 cal. ka BP, while the glacio-isostatically depressed St. Lawrence River Valley was inundated by the Atlantic Ocean. During the period of this connection, ELO level was confluent with slowly rising sea level, and the lake constructed a transgressive beach deposit with washover surfaces. ELO remained fresh due to a high flux of meltwater inflow. The marine water level connection stabilized water level in ELO relative to its shore and facilitated shore erosion, sediment supply and barrier construction. Glacio-isostatic uplift of the outlet sill, faster than sea-level rise, lifted ELO above the Champlain Sea about 12.5 cal. ka. Shortly after, a hydrological deficit due mainly to a combination of diverted meltwater inflow and dry climate, well known from regional pollen studies, forced the lake into a lowstand. The lowstand stranded the barrier, which remains as evidence of sea level, the farthest inland in eastern North America north of the Gulf of Mexico at the time. The highest palaeo-washover surface provides a sea-level index point.
Summary(Plain Language Summary, not published)
A distinct deposit of sand and gravel up to 5 m thick beneath mud in western Lake Ontario, Ontario, is concave to the east 75 to 79 m below the lake and 3 to 7 m below present sea level. It is a former barrier beach that was constructed by accumulation of wave-eroded sediment about 12,900 to 12,600 years ago while Early Lake Ontario was supported by the slowly-rising sea. At that time, the Atlantic Ocean had inundated the St. Lawrence River valley and fresh meltwater discharge from upstream glacial lakes prevented salt-water intrusion into the Lake Ontario basin. The beach is a newly recognized marker of paleo-sea level, the farthest west in eastern North America north of the Gulf of Mexico at the time.

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