Editing Polystrate fossil (section)

====Glacial deposits====
Unfossilized, late [[Pleistocene]] upright trees have been found buried beneath [[glacial deposit]]s within North America along the southern edge of the [[Laurentide Ice Sheet]]. These buried forests were created when the southern edge of the Laurentide Ice Sheet locally dammed valleys. As a result, meltwater lakes filled these valleys and submerged forests within them. Sediments released by the melting of the adjacent ice sheet rapidly filled these lakes, which quickly buried and preserved the submerged forests lying within them. One forest of ''in situ'', 24,000-year-old unfossilized upright trees was exposed by excavations for a quarry near [[Charleston, Illinois]].<ref>Hansel, A.K., R.C. Berg, A.C. Phillips, and V. Gutowski, 1999, ''Glacial Sediments, Landforms, Paleosols, and a 20,000-Year-Old Forest Bed in East-Central Illinois'', Guidebook 26. Illinois State Geological Survey.</ref>  Excavations for a tailings pond about [[Marquette, Michigan]], exposed an ''in situ'' forest of unfossilized trees, which are about 10,000 years old, buried in glacial lake and stream sediments.<ref>Pregitzer, K.S., D.D. Reed, T.J., Bornhorst, D.R. Foster, G.D. Mroz, J.S. Mclachlan, P.E. Laks, D.D. Stokke, P.E. Martin, and S.E. Brown, 2000, ''A buried spruce forest provides evidence at the stand and landscape scale for the effects of environment on vegetation at the Pleistocene/Holocene boundary". Journal of Ecology 88(1):45-53
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Illustrated articles about unfossilized upright trees found within glacial deposits of North America include： (1.) [http://www.museum.state.il.us/muslink/forest/htmls/how_bury.html ''How Do We Know?:Buried Forests'']; (2.) [http://www.admin.mtu.edu/urel/breaking/2000/forest.html ''Researchers Study 10,000-Year-Old Buried Forest'']; and (3.) [http://www.geo.msu.edu/geogmich/chippewa.html ''Glacial Lake Chippewa and Stanley''].
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