Closing the Gap Between the Geologic and Historical Records in the Laurentian Great Lakes by Providing the Most Detailed Account of Paleo Lake Level, Ranging from Decades to Five Millennia.

John W Johnston, University of Waterloo, Waterloo, ON, Canada, Kenneth E Lepper, North Dakota Univ, Fargo, ND, United States, Erin Argyilan, Indiana University, Geosciences, Gary, IN, United States, Douglas A Wilcox, SUNY-The College at Brockport, Environmental Science and Biology, Brockport, NY, United States, Steve J Baedke, James Madison University, Department of Geology and Environmental Science, Harrisonburg, United States and Todd A Thompson, Indiana Geological Survey, Indiana University, Bloomington, IN, United States

Contact First Author: John W Johnston; jwjohnston@uwaterloo.ca

Previously Published Material: A portion was recently published in a scientific journal: Johnston. J.W., Thompson, T.A., and Wilcox, D.A. (2014) Paleohydrographic reconstructions from strandplains of beach ridges in the Laurentian Great Lakes, in Martini, I. P., and Wanless, H. R., eds., Sedimentary Coastal Zones from High to Low Latitudes: Similarities and Differences: Geological Society, London, Special Publications, 388, 213-228. http://dx.doi.org/10.1144/SP388.22

Abstract ID#: 35993

 

English Abstract:
The current temporal and spatial context of water-level change, drivers of change, and possible future scenarios of the Laurentian Great Lakes is controversial. Paleohydrographs are being constructed from measured subsurface elevations of paleo-swash zones and modelled ages in strandplains of beach ridges that are preserved in embayments along the margins of the lakes. More than 800 elevations and 200 ages have been collected from 15 strandplains to construct site-specific strandplain paleohydrographs. Paleo shoreline elevations from whole strandplains or sets of correlative paleo-beaches within strandplains are then used to establish an outlet paleohydrograph for each lake. Adjusting strandplain paleohydrograph elevations to account for glacial isostatic adjustment (GIA) and refining age models help define the outlet paleohydrograph. This iterative approach helps identify common basin-wide water-level patterns and changes in outlet location or conveyance. Systematic patterns of elevation and geomorphic/sedimentologic properties in individual, groups and sets of beach ridges in strandplains suggest that long-term patterns of water-level change and sediment supply occurred on decadal, centennial, and millennial scales. Current data from strandplains of Lake Huron are being compared to data from Lake Michigan (Baedke & Thompson 2000) to produce an outlet paleohydrograph representative of this large hydraulically connected lake. Comparison with the outlet paleohydrograph of Lake Superior (Johnston et al. 2012) will help to decipher a more accurate understanding of GIA, water-level fluctuations, and outlet conveyance. These refinements are expected to complement the instrumental lake-level record back through time. The extended record can then be used to augment knowledge of natural (climate-driven) fluctuations and, thereby, to contribute to the effective management of the largest fresh, surface-water system in the world.
Back to: Hydroclimatic Processes in the Laurentian Great Lakes