CGRG Bibliography of Canadian Geomorphology
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Author : Douglas, S.; McCarthy, F.; and Blasco,S.
Date : 1997
Title : Seiches in Lake Erie - palynological evidence
Publication : 30th Annual Meeting of the American Association of Stratigraphic Palynologists, Program and Abstracts. Edited by: R.Wicander; S. Damassa; and P.K. Strother.. Swope Center, Marine Biological Laboratories, Woods Hole, Massachusetts September 14 - 19, 1997.
Issue :
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Abstract
Seiches result from wind setups and storm surges and are characterized by high water levels at the downwind end of a body of water. The configuration of Lake Erie with its long axis parallel to major storm tracks across the Great Lakes region, along with a narrowing of the lake at the eastern end, tends to focus strom surges, making seiches relatively common in eastern Lake Erie and a concern for property owners. Palynological evidence at Core 10, in 50 m of water south of Long Point, indicates low rates of sedimentation since ~3,600 y BP. Undulations of the lake bed, and winnowing and deposition around a shipwreck located near the site, indicate current activity and erosion well below wave base. The low percentages of small, light pollen grains such as Ambrosia and the relatively large percentages of more resistant taxa such as Acer saccharum both on and immediately adjacent to the shipwreck indicate the possible reworking of sediments. We hypothesise that strong, episodic bottom currents caused by oscillatory or return flow during seiches interact with the sediments. Strong bottom currents are only recorded in sediments after 3,600 y BP and may result from progradation of Long Point into the deep eastern basin after the Nipissing `Flood', which may act as a focus for such currents. Palynological and sedimentological evidence suggests that Core PTA2, taken from a forested swamp 3 m above the current water level of Lake Erie, became an isolated peat basin after the Nipissing `Flood' water levels receded ~3,600 y BP. A zone of fluctuating aquatic and terrestrial pollen taxa, bracketed by radiocarbon dates, indicates a reintroduction of Lake Erie water to the study site between 3,000 to 2,900 y BP, probably caused by seiches. A series of sand ridges that currently separate the peat basin from Lake Erie suggest that Lake Erie water levels must have been close to 176 m asl in order for the incursion of fresh water to take place at the site, suggesting that the Lyell/Johnson sill continued to control the level of Lake Erie until 2,900 y BP. The switch of controlling sills for Lake Erie to the Fort Erie/Buffalo sill may have therefore taken place at a later date than previously reported.
Bibliography of Canadian Geomorphology