Lake levels in the Erie Basin of the Laurentian Great Lakes |
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| Authors: | C F M Lewis G D M Cameron T W Anderson Jr" target="_blank">C W HeilJr P L Gareau |
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| Institution: | (1) Geological Survey of Canada Atlantic, Natural Resources Canada, Bedford Institute of Oceanography, Box 1006, Dartmouth, NS, B2Y 4A2, Canada;(2) Geological Survey of Canada, Natural Resources Canada, 601 Booth Street, Ottawa, ON, K1A 0E8, Canada;(3) Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA;(4) GeoInformatics Services, 28 Crichton Park Road, Dartmouth, NS, B3A 2N8, Canada |
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| Abstract: | Water levels in the Lake Erie basin are inferred from glacial lake times to present. An era of early to middle Holocene lowstands
is defined below outlets by a submerged paleo-beach, and truncated reflectors in glaciolacustrine sediment beneath a mud-covered
wave-cut terrace. Also, the glacial clay surface above the paleo-shore level has elevated shear strength because of porewater
drainage during subaerial exposure. Below the paleo-shore where exposure did not occur, clay strength remained normal. Sedimentation
rates were reduced during the lowstands. The distortion of once-level shore zone indicators by differential glacial rebound
was removed by computing original elevations of the indicators using an empirical model of rebound based on observations of
upwarped former lake shorelines. Erie water-level history was inferred from a plot of the original elevations of lake-level
constraints and outlets versus age. The lake history was validated by reference to ~83 water-level indicators, not used as
constraints. During the deglaciation, lake-crossing moraines were likely eroded by fluvial drainage into low-level Lake Ypsilanti
and a subsequent unnamed low lake to produce the Lorain Valley and Pennsylvania Channel. Once inflow from the upper Great
Lakes basins was directed to Ottawa Valley about 10,400 (12,270 cal BP), Erie water levels descended in a dry, evaporative
climate to a closed lowstand during which ostracode δ18O increased ~2‰ above present values. Lake level began to rise 6,000 to 7,000 (6,830 to 7,860 cal) BP in response to increased
atmospheric moisture and later, to northern inflow as the Nipissing Transgression returned upper Great Lakes drainage to Lake
Erie by about 5,200 (6,000 cal) BP. At that time, the lake overflowed the uplifted Lyell–Johnson Sill north (downstream) of
the present Niagara Falls at higher-than-present levels. After recession of the Falls breached this sill about ~3,500 (~3,770 cal)
BP, Lake Erie fell 3–4 m to its present Fort Erie–Buffalo Sill. The extended low-water phase with its isolated sub-basins
could have restricted migration of aquatic fauna. The early to middle Holocene closed-basin response highlights the sensitivity
of Lake Erie to climatic reductions in its water budget. |
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