Stratigraphic Study of Beach Features on the Southwestern Shore of Lake Michigan: New Evidence of Holocene Lake Level Fluctuations

摘要

The study of a beach ridge complex along the southwestern shore of Lake Michigan provides new evidence of long-term trends in water level fluctuations of Lakes Michigan and Huron that are not discernible in the short, 125-year historic record of measured lake level changes. Radiocarbon age control of lake terraces and other beach features provided by dates from buried peat and fossil wood indicates that during the past 2,000 years lake levels were markedly higher and lower than present levels for periods on the order of centuries. This suggests that historically recorded levels, considered high by modern standards, may represent a relatively low cycle on a naturally fluctuating trend. Study results thus have important implications for engineers and hydrologists concerned with planning and construction along the lake shore.