Lake Superior represents an important component of the aquatic ecosystem in North America. Along its south shore, ongoing lake-level rise, accelerated erosion, and wetland loss are major environmental concerns to coastal communities. A better prediction of the future of this shore requires placing the instrumental lake-level records in a geological context. However, our knowledge of the late-Holocene history of the world's largest freshwater body remains fragmentary. Here we present a sedimentary record of late-Holocene relative lake-level changes by dating transgressive basal peats resting directly on a sandy substrate along a bathymetric gradient in Bark Bay Slough, Wisconsin. Our record shows a moderate lake-level rise at 1.4±0.2. mm/yr from about 2200 to 1250. cal. yr. BP as a result of relatively slow differential uplift of Bark Bay relative to the controlling outlet at Port Huron. The rise accelerated to 2.3±0.2. mm/yr at about 1250. cal. yr. BP when Sault Ste. Marie emerged as the controlling outlet, thereby separating Superior from Lakes Michigan-Huron and giving rise to the modern hydrographic regime of the upper Great Lakes. The timing of this event in our record is about 1000 yr later than that estimated in most previous studies, but our data complement and confirm the younger age of lake separation inferred using a different methodology. Our results not only provide pertinent information for hydrological regulation, navigation operation, and infrastructural design in the upper Great Lakes, but also provide insight into freshwater wetland succession on flooded coasts.
Bibliographical noteFunding Information:
Funding was provided by the National Science Foundation (to S. M. Colman, Grant no. OCE-0623607 ) and fieldwork was supported by the National Lacustrine Core Facility (LacCore) . We thank Dr. E.D. Reavie for providing logistic support and A. Lingwall and M. Du for their assistance during the field work. G.A. Milne acknowledges funding support from the Natural Sciences and Engineering Research Council of Canada and the Canada Research Chairs Program . Our gratitude is also extended to Mike Lewis and two anonymous reviewers for their constructive comments on the manuscript. This is a contribution to the PALSEA PAGES/IMAGES/WUN working group.
Copyright 2013 Elsevier B.V., All rights reserved.
- Basal peats
- Glacial isostatic adjustment
- Lake level
- Lake Superior
- Lakes Michigan-Huron
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