T218 Dunes, Loess, and Dust: Paleo- and Modern Perspectives on Activation, Stratigraphy, and Processes II

Tuesday, 2 November 2010
1:30 PM - 5:30 PM
Room 303

OSL AGES OF COASTAL SAND DUNES ALONG THE NORTHWESTERN SHORE OF LAKE HURON IN LOWER MICHIGAN: IMPLICATIONS FOR SAND SUPPLY AND PALEOWINDS

Paper number: T218-2
Program: Technical Sessions
Time: 1:45 PM – 2:00 PM

Authors

Abstract

Coastal sand dunes are very common in Lower Michigan, especially along Lake Michigan due to prevailing westerlies and high sand supply. These western dunes have been the focus of numerous geomorphic investigations that demonstrate a history for the past 5,000 years. Coastal dunes on Lower Michigan’s shore with Lake Huron are far less common and have yet to be examined. They have the potential to yield important information about regional wind patterns and their response to lake level fluctuations. This study is the first to investigate such dunes and focuses on Manitou Beach in northeastern Lower Michigan. The chronology was reconstructed through optical dating of eolian sands in three dune groups.

The Algonquin group contains low dunes on the Algonquin lake plain that apparently formed about 6 ka, perhaps due to a warmer/drier climate. The extensive Manitou group contains prominent ridges between the shore and a bluff eroded during the Nipissing high lake stand about 5.5 ka. Most ridges apparently formed shortly after the lake regressed and about 4 ka. A large, easterly oriented parabolic dune developed about 2.8 ka on the eastern side of the dune field. The Hammond group consists of a dunes perched on the Nipissing bluff on the west side of the study area. These dunes also formed between about 5 and 4 ka. This study demonstrates that dunes at Manitou Beach are older than those on the northwest coast of Lower Michigan, which formed largely between about 3.5 and 1 ka. This dichotomy is revealing because 1) it suggests activation at Manitou Beach is mostly related to Nipissing bluff erosion and associated high sand supply following that event, and 2) it reflects the overall impact of prevailing westerlies and shore aspect on coastal dune formation in Lower Michigan. This study is also noteworthy because it suggests unusually strong easterly winds apparently occurred around 2.8 ka.