Environmental magnetism in sediment cores from southwestern Ohio as a proxy for climate change during the late Quaternary.

by Scott A. Bagocius
Senior Independent Study
The College of Wooster
(2002)

Funded by the Keck Geology Consortium

 

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Above is a glacier traveling through a mountain valley. Photo taken in Alberta, Canada.

 

Throughout the Quaternary Period, the past two million years of Earth's history, there have been as many as 20 ice ages This averages to be one ice age every 100,000 years. During these past glacial maximums, 30% of the world was covered in ice compared to a mere 10% today. The reasons for these reoccurring Ice Ages are uncertain. However, changes in climate are thought play a major role in the formation and destruction of glaciers. One big question concerning glacial geologists is how climate controls glaciation. Further study is many sciences are needed for this question to be accurately answered. A good start to solving this enigma is by examining the patterns of ancient glacial movement. Ohio and its surrounding states are among the best areas to study the advance and retreat patterns of the last glaciation. This area of the United States is a great record holder of the recent transition from glacial to interglacial stages due to the abundance of detailed sedimentation left by glaciation. Most recently, the Laurentide Ice Sheet entered Ohio around 22,000 years ago reaching its greatest point south around 20,000 years ago (Eckberg et al., 1993). Then, 15,000 years ago, the ice sheet began to retreat (Eckberg et al., 1993).

 

 

As ice sheets flow over an area, they scrape and gouge the land they flow on. This results in the accumulating sediment and debris within a glacier. By studying the formation and samples found in the deposits left after a glacier melts, geologists can put together a chronological history of a glacier's movement through time.Within sediment, lies organic material which in some way has found itself in the basin. This organic material can be used to radiocarbon date in order to determine the ages of the layers containing organic material. Once a date is found for the material, it is implied that the sediment apove the material is younger and sediment below it is older. This holds true as long as the sediment remains undisturbed from its orginal depsotion.

 

The Keck Ohio Project 2001 was conducted in and around Dayton, Ohio. The purpose of the project was to obtain sediment cores throughout an area to date the Laurentide Ice Sheet's retreat. Eight undergraduates (Scott Bagocius, Louisa I. Bradtmiller, Joel Byersdorf, Lisa King, Jessica McDonough, Margretta Meyer, Monica Kaitz, and Kimberly H. Sunderlin) and three professors, Greg Wiles, Thomas Lowell and Donald Pair, all from various regions of the U.S., took part in the research lasting about a month from July to August. The first week of the project was conducted in Alberta, Canada studying the geomorphological aspects of modern glaciers. By seeing an active glaical settings, it enables a better understanding for the upcoming research to be done with glacial sediment cores in Ohio.

 

 After our return from Canada, the next three weeks were spent obtaining 10 cores from sites north of the Dayton Area and conducting preliminary analyses on them at the University of Dayton in their Keck Laboratory. Preliminary analyses of each core consisted of grain-size, magnetic susceptibility, loss-on-ignition, locating macros for radiocarbon dating, and a physical description.

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 Location map with the 10 cored sites relative to Indiana and Ohio.

 

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Picture of a bog site. Notice the heavy vegetation on the outskirts of the increasingly lighter vegetation towards the middle of the bog.

 

 After the initial analyses at the University of Dayton, each of the eight undergraduate students were given a core to take back to their home insitution to conduct further reasearch on. Geochemistry, varve analysis, pollen content, diatom analyses and environmental magnetism are a few of the fields the students have choosen to pursue.

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 Picture of Keck participants in the action of pulling and extruding sediment cores.


 My personal project is to look more closely into the environmental magnetism of my core. By analyzing the magnetic properties of the sediment at given increments throughout the core, various environmental changes will be inferred. Different envornmental conditions allow for different magnetic properties within sediment. By measuring these magnetic properties, the results can be compared to known values and thus be interpreted with an environmental condition. I will be conducting ARM, IRM, and more in-depth magnetic susceptibility measurements with my core. These measurements will be used to determine between differing magnetic mineralogy as well as factors involving sediment deposition.

 

References Cited:

Eckberg, M.P., Lowell, T.V., & Stuckenrath, R., 1993. Later Wisconsin glacial advance and retreat patterns in southwestern Ohio, U.S.A. Boreas. 22: 189-204.

Lowell, T.V. & Stuckenrath, R., 1990. Late Wisconsin advance and retreat pattern in the Miami Sublobe, Laurentide Ice Sheet. Annals of Glaciology. 14: 172-175.

Lowell, T.V., Savage, K.M., Brockman, C.S., & Stuckenrath, R., 1990. Radiocarbon analyses from Cincinnati, Ohio, and their implications for glacial stratigraphic interpretations. Quaternary Research. 34: 1-11.

Other Relative References:

Dekkers, M.J., 1997. Environmental magnetism: an introduction. Geologie en Mijnbouw 76: 163-182.

Shane, L.C.K., 1987. Late-glacial vegetional and climatic history of the Allegheny Plateau and the Till Plains of Ohio and Indiana, U.S.A. Boreas. 16: 1-20.

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.

 

Useful Links:

University of Wisconsin's Laurentide Ice Sheet Project Webpage

Ice Age National Scientific Preserve homepage

Glacial Geology and Geomorphology homepage

Environmetnal Magnetism Lab Home Page School of Geography & Geosciences, University of St Andrews