Pollen diagram from the Nebraska Sandhills and the age of the dunes |
| |
| Authors: | HE Wright JC Almendinger J Grüger |
| |
| Institution: | 1. Limnological Research Center, University of Minnesota, Minneapolis, Minnesota 55455, USA;2. Abteilung für Palynologie der Universität, Unterekarspüle 2, D-34 Göttingen, West Germany |
| |
| Abstract: | Radiocarbon dates of organic alluvium beneath as much as 40 m of dune sand along the Dismal River have led to the suggestion that the Nebraska Sandhills date from the Holocene rather than the last glacial period. On the other hand, the basal layers of lake and marsh deposits in interdune depressions at three localities date in the range of 9000 to 12,000 yr B.P., implying a pre-Holocene age for the sand dunes. A pollen diagram for one of these sites, Swan Lake, indicates prairie vegetation throughout the last 9000 yr, with no suggestion that the landscape was barren enough to permit the shaping of the massive dunes characterizing the area. Sand was not transported across the site during the Holocene, either during the marsh phase, which lasted until 3700 yr B.P., or during the subsequent lake phase. The sand that buries the alluvium along the Dismal River may represent only local eolian activity, or it may indicate that the younger of the two main dune series identified by H. T. U. Smith (1965, Journal of Geology73, 557–578) is Holocene in age, and the older one Late Wisconsin in age. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
