Dendrogeomorphology of the Tana Dunes, Alaska

Ryan McAllister

Department of Geology, The College of Wooster

Wooster, Ohio

Disclaimer: This material is based upon work supported by a National Science Foundation grant. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.

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This past summer I was able to travel to Alaska supported by a grant from the National Science Foundation, Research Experience for Undergraduates (REU) program to conduct research for my Independent Study. Along on this trip north was my adviser. Greg Wiles, The College of Wooster, and his colleague Gordon Jacoby and Nicole Davi of Lamont-Doherty Earth Observatory. We spent three weeks working at six field site within the Wrangell-St. Elias National Park and Preserve. The sites included five glacier forefields and the subject of my Independent Study, the Tana Dunes.

The Tana Dunes are located between the Chugach and Wrangell Mountains, approximately 30 miles south of McCarthy. The overall dune type is parabolic with barchan dunes superimposed on it.

This dune system has been progressively migrating through a forest killing the trees as it advances. These dead trees are left standing throughout the dune. Currently the dunes are advancing along the northwest leading edge as well as laterally along the western edge. However, there are portions of the dune which have been stabilized in the past and areas that are currently stable. These past periods of stabilization can be identified by a paleosol. Stratigraphy of the dune suggests a possible Late Wisconsin deglacial event is responsible for the original deposition of the sediment. The primary controlling mechanism for the reactivation of the dunes is thought to be climate conditions associated with the Little Ice Age (1200-late 1800’s AD.). Dynamic processes such as fluvial erosion may also have contributed to the reactivation of the dunes.

My independent study will investigate the mechanism(s) responsible for reactivating the dunes. The dead white spruce trees within the dune will be used to help reconstruct the story of dune migration. I will be using tree-ring analysis to extract geomorphological information from cores and discs to date the dead trees. I will crossdate the dead trees and create a several hundred year chronology for the dunes of dune activity.

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