Radiocarbon dating of buried soils-- Humate fractionation, delta C-13 correction and paleoclimatic signals: Geoarchaeological implications in the central Great Plains
- Univ. of Kansas, Lawrence, KS (United States). Dept. of Geography
- Kansas State Univ., Manhattan, KS (United States). Dept. of Geography
Due to perceived uncertainties associated with humate-derived C-14 ages from buried soils, samples were collected and dated from buried A horizons developed in alluvium and loess within the Kansas River basin of Kansas, Nebraska, and Colorado. Soils range in age from c. 30ka to latest Holocene. Samples were split, sent to two laboratories (SMU and Pittsburgh), and fractionated. Ages were determined from three fractions: total bulk, base-soluble (humic acid), and residue (humins). For individual samples, a significant age difference exists among the three fractions, with very little interlaboratory variation. No apparent relationship exists among the three fractions dated; the residual fraction is not consistently the oldest as anticipated, and the total humate fraction is not the youngest. Percent variation among fractions may be a depth/age function for soils within a given profile of sequence. Delta C-13 values derived from the different fractions indicate more negative values for the total humate fraction. Percent variation in delta C-13 values among the three fractions seems unrelated to age or depth. A strong paleoclimatic signal is contained within the temporal record of delta C-13 values derived from soils dating c. 36-1ka. Warm-season (C4-type) grasses were apparently more important in the middle Holocene period of aridity (Altithermal). Change from a cooler environment of the latest Pleistocene to the relatively warmer conditions of the earliest Holocene is recorded in the humates distributed within the A horizon of the Brady geosol. Humates from the Gilman Canyon Formation geosol dating c. 36-20ka exhibit delta C-13 values indicating an initial warm-season grass environment which subsequently evolved into a cool-season grass environment.
- OSTI ID:
- 5769017
- Report Number(s):
- CONF-921058-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COLORADO
PALEOCLIMATOLOGY
KANSAS
NEBRASKA
SOILS
ISOTOPE DATING
CARBON 13
DEPTH
GRAMINEAE
HUMIC ACIDS
INTERLABORATORY COMPARISONS
VARIATIONS
AGE ESTIMATION
CARBON ISOTOPES
DEVELOPED COUNTRIES
DIMENSIONS
EVEN-ODD NUCLEI
ISOTOPES
LIGHT NUCLEI
LILIOPSIDA
MAGNOLIOPHYTA
NORTH AMERICA
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PALEONTOLOGY
PLANTS
STABLE ISOTOPES
USA
580000* - Geosciences