Reconstructing the Late Glacial Environmental History of Brown's Lake Bog

by Clint Bailey

 

My Senior Independent Study, beginning in the fall of 2002, is an attempt to reconstruct the environmental history of Brown's Lake Bog, an area 20 miles south of Wooster, Ohio. Research for this project began in the summer of 2002 as part of the Keck Ohio research experience for undergraduate Geology students.

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Figure 1. Working at Brown's Lake Bog

Brown's Lake Bog is a glacial relict bog created during the last glacial period in Ohio approximately 16,000 years ago. The site is owned by the Ohio Department of Natural Resources (ODNR) and managed by the Nature Conservancy. There is widespread interest in the history of this bog among Biologists and Geologists as well as local high schools which use the unique setting as a place for study. In 1966 the area was named a National Natural Landmark for its natural preservation and unique ecology.

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Figures 2 and 3. Driving the coring apparatus into the ground and extracting the sediment

The environmental history of Brown's Lake Bog is expressed in the sediment that has filled the basin since the last glacial period in Ohio. Two sediment cores were collected this summer from Brown's Lake Bog, each approximately 10 meters in length. Several abrupt changes within the sediment cores indicate significant environmental changes on a local, regional, or even global scale. Interpreting and understanding these changes in the sediment and environment is the ultimate goal of this project.

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Figure 4. One meter of sediment ready for analysis

Four types of material make up the cores from Brown's Lake Bog: peat, gyttja, silt, and diamicton. These sediments are a classic deglacial sequence representing the changes from glacial (diamicton) to lake (silt) to the rise in vegetation (peat and gyttja) at the Holocene transition.

 

Peat is a fiberous organic substance made of vegetation in various states of decomposition.
Interval: 3 to 9.2m

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Gyttja is a dark organic material similar to peat, but less fiberous and more compact.
Interval: 9.2 to 9.8m

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Silt is a medium brown to grey fine grain sediment, silt is refered to as mottled when it shows certain textures of discoloration.
Interval: 9.8 to 12.3m

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Diamicton is composed of silt, sand, and larger pebbles. Diamicton in a glacial environment is refered to as till.
Interval: 12.3 to 12.35m

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The sediments from Brown's Lake Bog represent environmental change since the last glacial period in Ohio. The variety in the materials shown above indicate that Brown's Lake Bog has been a vaslty different depositional environment over this time. Several studies such as Shane and Anderson (1993) have isolated as many as four significant periods of climate and biological change in northeast Ohio and throughout the Midwest. The challenge of this study is to compare the information yielded from sediments at Brown's Lake Bog to these other studies.

References:

Shane, L.C.K. and Anderson, K.H. (1993). Intensity, gradients and reversals in late glacial environmental change in east-central North America. Quaternary Science Reviews, 12, 307-320.

Yu, Z. and Wright Jr., H.E. (2001). Response of interior North America to abrupt climate oscillations in the North Atlantic region during the last deglaciation. Earth-Science Reviews, 52, 333-369.

Links:

An article about Keck Ohio from the University of Cincinnati.

Pictures from the Keck Ohio group and our trip to the Canadian Rockies.