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Vegetational History of the Shenandoah Valley, Virginia

By
Alan J. Craig
Alan J. Craig
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Published:
January 01, 1969

Two diagrams show the results of pollen analysis in sediments from Hack and Quarles Ponds, in the southern part of the Shenandoah Valley, Virginia.

The following pollen assemblage zones are distinguished:

  • (1) A basal Pinus-Picea zone, with abundant conifer pollen and relatively large amounts of herb pollen. Two subzones are distinguished: a Sanguisorba-Isoetes subzone, present only at Hack Pond, where the top of the subzone has been dated at 12,720 ± 200 years, and a Quercus-Corylus subzone, with less herb and more deciduous-tree pollen. This zone is believed to represent a period of conifer woodland dominated by spruce.

  • (2) A Quercus zone, with abundant Quercus and very little conifer pollen. Two subzones are distinguished: a lower Tsuga subzone and an upper Carya-Cephalanthus subzone. This zone is believed to represent a period when the vegetation was largely hardwood forest, commencing shortly after 9520 ± 200 years ago.

  • (3) A Quercus-Pinus zone, with much pollen of Quercus and Pinus and substantial amounts of other deciduous-tree pollen. This zone is believed to represent a period of oak-pine forest, the pines being predominantly those species found today in the vicinity of the sites.

The diagrams strongly resemble those from southeastern Virginia and North Carolina, but they differ very markedly from those of sites to the north in the area formerly covered by ice sheets of the Wisconsin glaciation. A time lapse probably occurred between similar vegetational developments in different areas. The results support the conclusions of some previous writers that substantial changes in vegetation occurred at considerable distances from the ice sheets. There is also support for suggestions that the Appalachians constituted a refuge for Picea and Pinus during at least part of Wisconsin time.

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GSA Special Papers

United States Contributions to Quaternary Research; Papers Prepared on the Occasion of the VIII Congress of the International Association for Quaternary Research Paris, France, 1969

Stanley A. Schumm
Stanley A. Schumm
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William C. Bradley
William C. Bradley
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Geological Society of America
Volume
123
ISBN print:
9780813721231
Publication date:
January 01, 1969

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