ive amounts of sediment from the Blue Nile/Atbara catchment in the Ethiopian Highlands and from the White Nile catchment in tropical East Africa. The authors show that when there was more rainfall in the Ethiopian Highlands, and more water in the Nile flood, there was less sediment. This is the opposite of most rivers. It was caused by changes in the amount of vegetation in the Ethiopian Highlands. The amount of rainfall has changed dramatically over the past 6500 years as a result of global climate change. The authors suggest that the changes in the type of mud brought down the Nile and discharged into the Eastern Mediterranean may have had a significant effect on environmental conditions in the Levantine Basin.

Widespread middle Holocene dune formation in the eastern upper peninsula of Michigan and the relationship to climate and outlet-controlled lake level.

Alan F. Arbogast, et al., Department of Geography, Michigan State University, East Lansing, Michigan 48824-1115, USA. Pages 5558.

Michigan is located in the core of the Great Lakes region and is known for its dramatic glacial and coastal landscapes. Less well known are the prominent dune fields that are scattered throughout both peninsulas of the state. Historically, these dune fields were thought to have formed in a deglacial environment when poorly vegetated former (pro-glacial) lakebeds were deflated by strong winds. One of the largest of these dune fields is the Newberry dune field, which covers extensive parts of the Lake Algonquin lakebed in the eastern upper peninsula of Michigan. This dune field contains numerous parabolic dunes, with northwest orientations that are up to 8 m high. In order to test the age of these dunes, sands at five widely spaced sites were dated via optically stimulated luminescence (OSL) of quartz. The resulting ages establish that eolian sand was last mobilized in the region between ca. 7 and 5.5 ka. Although this interval corresponds to the drier Alti
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Contact: Ann Cairns
acairns@geosociety.org
303-357-1056
Geological Society of America
4-Jan-2002

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