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Northern Pleistocene Valley Trains

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About the Northern Pleistocene Valley Trains

The Northern Pleistocene Valley Trains are a portion of the Mississippi Alluvial Plain, located in the east of the region, consisting of several discontinuous pieces from Western Tennessee and eastern Arkansas south into Mississippi.

This region was formed as deposits from glacial outwash from the Ohio and Mississippi rivers; these deposits consist mostly of coarse sand and gravel, and were lain down on around 54% of the entire Mississippi alluvial plain, but in most places they have been eroded by channel migration and/or covered with more recent sediments. In this region, however, the older (10,000-20,000 years ago) deposits are at the surface, and soils are formed on them. This region is nearly level, and the surface is at or only slightly above that of neighboring floodplains with newer soils. The landscape here is structured differently from that of the surroundings: there is a pattern of branching and braided channels, reflecting the easily-erodible nature of glacial outwash. Like neighboring regions, stream gradients here are also low. Soils here tend to be well-drained due to its coarse texture.

This area was originally covered mostly in bottomland hardwood forests, with dominant trees including Nuttall's oak (Quercus texana), willow oak (Quercus phellos), swamp chestnut oak (Quercus michauxii), water hickory (Carya aquatica), American sweetgum (Liquidambar styraciflua), sugarberry (Celtis laevigata), American elm (Ulmus americana), and green ash (Fraxinus pennsylvanica). The wettest sites supported some bald cypress (Taxodium distichum) and water tupelo (Nyssa aquatica), but overall, there were fewer of the tree species preferring more extensive flooding. There were also some forested canebreaks with scattered deciduous trees growing amonst giant cane (Arundinaria gigantea).

This region has been extensively channelized, although some of the original drainage pattern is still evident in places. It is now used primarily for cropland, mostly soybeans, with some cotton, as well as corn, wheat, rice, and sorghum. There is also commercial catfish farming. Some forest remains.

Most of this region is entirely surrounded by the Northern Holocene Meander Belts, which has more poorly-drained soils formed on more recent sediments, and a less-branching drainage pattern. However, in the east, a few areas directly border the higher, more rugged Bluff Hills of the Mississippi Valley Loess Plains, or where the bluffs are absent, the Loess Plains directly. The Loess Plains are slightly higher in elevation and have fine-textured, nutrient-rich soils.

References

1. Griffith, G.E.; Omernik, J.M.; and Azevedo, S.H. "Ecoregions of Tennessee (Poster)", U.S. Geological Survey, Reston, VA (1998) Web.