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Properties of a 5500-year-old flood-plain in the Loup River Basin, Nebraska
- Source :
-
Geomorphology . Dec2003, Vol. 56 Issue 3/4, p243. 12p. - Publication Year :
- 2003
-
Abstract
- Flood-plain aggradation within the Loup River Basin of central Nebraska was episodic and alternated with incision throughout much of the Holocene. A widespread episode of flood-plain stability, however, occurred about 5700–5100 cal. year BP. The purpose of this paper is to describe the properties of this buried flood-plain at six sites in the basin, to consider why the properties of the buried flood-plain vary from site to site, and to evaluate possible reasons why the Loup River flood-plains stabilized 5500 years ago. Episodic valley-bottom aggradation was common during flood-plain formation at five of the six sites. The radiocarbon ages, particle-size data, and organic-carbon data for the buried flood-plain reveal that valley-bottom aggradation generally slowed between about 5700 and 5100 cal. year BP. Erratic down-profile changes in percentages of sand, clay, and organic matter indicate flood-plain sedimentation and soil formation were often episodic. Sand and clay rarely show a steady fining-upward trend. Organic matter fluctuates with depth; at some sites multiple, incipient A horizons were buried during waning valley-bottom aggradation. At two localities, the buried flood-plain is evident as a clay-rich stratum that must have been deposited in a paleochannel. Flood-plain stabilization between 5700 and 5100 cal. year BP probably occurred in response to the effects of external climate forcing on vegetation and hydrologic changes. Flood-plains of other rivers in the central Great Plains also stabilized at this time, further supporting a climatic explanation for slowing of valley aggradation and formation of a flood-plain at this time. Recognition of buried flood-plains is important to both soil mapping in valleys and to the discovery of cultural resources in valleys. [Copyright &y& Elsevier]
- Subjects :
- *FLOODPLAINS
*WATERSHEDS
Subjects
Details
- Language :
- English
- ISSN :
- 0169555X
- Volume :
- 56
- Issue :
- 3/4
- Database :
- Academic Search Index
- Journal :
- Geomorphology
- Publication Type :
- Academic Journal
- Accession number :
- 11536616
- Full Text :
- https://doi.org/10.1016/S0169-555X(03)00154-5