Evidence of Late-Holocene floods in the central Great Plains
- Univ. of Northern Iowa, Cedar Falls, IA (United States). Dept. of Geography
From southwestern Kansas to northeastern Nebraska alluvial studies are revealing stratigraphic and morphological evidence of two brief periods of large-magnitude floods in the central Great Plains during the past 2,500 years. Evidence for these floods consists of deeply-scoured paleochannels, coarse-textured point-bar deposits overlying fine-grained deposits, soils on former floodplains that are buried by alluvium, and fluvial terraces. Wood and bone collagen in several deeply-scoured paleochannels date to about 2,300--2,000 yr B.P. Modest incision and floodplain reconstruction at this time is evident from both maps of fluvial landforms and C-14-dated stratigraphic sections in both large and small basins. Sediments near the base and top of inset gully fills in both trenched and untrenched tributary valleys to Great Plains rivers date to about 2,000 yr B.P. A second episode of large floods in the central Great Plains occurred about 1,300--850 yr B.P. Throughout most valleys a buried soil that developed in alluvium occurs from 50 cm to 1.0 m below terraces. Recently, stratified point-bar deposits beneath a low terrace in a small (9.6 km[sup 2]) basin in east-central Nebraska were exposed and studied. Crossbedded, gravelly sand strata alternative with massive, dark, silty strata. The C-14-dated section indicates that multiple floods occurred between 1,250 and 850 yr B.P. Such widespread evidence of flooding about 2,300--2,000 yr B.P. and again 1,250--850 yr B.P. attests to regional, and probably, global climate changes at these times. Discontinuities in the alluvial record have previously been recognized at 2,000 and 1,200 yr B.P. Furthermore, a discontinuity in the pollen record at 850 yr B.P. has long been recognized.
- OSTI ID:
- 5689121
- Report Number(s):
- CONF-921058--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 24:7; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
Similar Records
Rate estimates for lateral bedrock erosion based on radiocarbon ages, Duck River, Tennessee
A view of late glacial runoff from the lower Mississippi River valley
Related Subjects
580000* -- Geosciences
AGE ESTIMATION
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON 14
CARBON ISOTOPES
CENOZOIC ERA
CLIMATIC CHANGE
DEVELOPED COUNTRIES
DISASTERS
EVEN-EVEN NUCLEI
FLOODS
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOLOGY
GEOMORPHOLOGY
ISOTOPE DATING
ISOTOPES
LIGHT NUCLEI
NORTH AMERICA
NUCLEI
PALEOCLIMATOLOGY
PALEONTOLOGY
QUATERNARY PERIOD
RADIOISOTOPES
STRATIGRAPHY
USA
YEARS LIVING RADIOISOTOPES