Correlation of Historical and Sedimentological Records from Goshorn Lake, a Small Lake in a Coastal Dune Complex of Lake Michigan
Prof. Suzanne DeVries-Zimmerman, Dr. Graham Peaslee and Dr. Edward Hansen
Sand in lakes near coastal dunes has been used as a proxy for aeolian activity. It is important to use a sampling strategy maximizing the probability of encountering aeolian sand and minimizing the probability of encountering sand transported by fluvial processes or washed/slumped into the lake from the shores. To test this, lake sediments were collected from Goshorn Lake in Allegan County, Michigan. This lake abuts a Lake Michigan dune complex at one end, has a stream entering at the opposite end, and is subject to anthropogenic disturbances along its banks. Aerial photographs, building records, and a published oral history of the lake were used to reconstruct aeolian activity and anthropogenic disturbance over the last 76 years. This history was compared to sand concentration as a function of depth obtained by textural analysis of 12 Glew cores collected across the lake basin. 137Cs analyses were used to identify the 1963 bomb peak as a temporal reference point. The least amount of sand occurs in the cores furthest from the dunes, closest to the stream. A few sand peaks, <20%, are present. Cores collected closer to the dunes are characterized by multiple sand peaks, between 20–80% sand in the lower to middle portion of the core. In the upper core portions, the upward decrease in sand begins before 1963, consistent with aerial photographs showing a decrease in dune activity after 1938. One Glew core recorded a spike in sand after 1963. Historical records suggest this can be correlated with major construction at that location and time period. Small sand peaks near the stream inlet may reflect fluvial flux increases while sand peaks near the lake margins can reflect increases in sand resulting from shoreline disturbances. Therefore, the majority of the sand in the lake sediments appears to be aeolian.
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