Radiocarbon dating pedogenic carbonates
Radiocarbon dating of SOM provides minimum ages of SOM for the length of soil formation [10,11,12,13,14,15].
Radiocarbon ages of the SOM are controlled by the rate of carbon cycling in soils, reflecting the input rates and mean residence time (MRT) of gradually accumulating SOC (the carbon of soil humus) rather than the age of the soils [4,16,17].
Two of these pendants were selected for stable carbon (δ plants with temporary dominances of the latter.
Three radiocarbon ages between 43 and 35 ka BP indicate that the pendants formed almost entirely during the Upper Pleistocene with high growth rates of 4.1 to 9.7 mm / 1000 a.
All sampled soils were classified as Fine-silty, mixed, frigid Pachic Hapludolls (Haplic Chernozem).
The radiocarbon age (C date, y BP) of SOC was highly variable: in the native grassland field, it varied from post-bomb (A-horizon) to 8011 ± 54 y BP (C-horizon); in the continuous fallow, it varied from 1569 ± 41 y BP (Ap-horizon) to 11,380 ± 180 y BP (C1-horizon); and in the cropland, it varied from 1055 ± 38 y BP (Ap-horizon) to 11,805 ± 68 y BP (Ck-horizon).
Conversion of native grasslands to agricultural sites has resulted in remarkable changes in soil carbon at depth, but its impact on soil diagnostic horizons is unknown.
This study was conducted to radiocarbon date the soil organic carbon (SOC) and quantify pedogenic carbonates in the Russian Chernozem at depth at three sites: a native grassland field (not cultivated for at least 300 years), an adjacent 50-year continuous fallow field in the V. Alekhin Central-Chernozem Biosphere State Reserve in the Kursk region of Russia (UNESCO—MAB Biosphere Reserve), and a cropland in the Experimental Station of the Kursk Institute of Agronomy and Soil Erosion Control.
Here, we study up to 18 cm long pedogenic carbonate pendants which occur in highly calcaric soils near the Early Bronze Age site of Tell Chuera in north-eastern Syria.
An increase in the activity of carbon exchange processes, and, hence, the rejuvenation of radiocarbon dates, indicate the input of young SOM to the soils, while more ancient dates indicate a decrease in recent SOM.
The presence of soil carbonates (disseminated and concretions) can also impact the C ages of carbonates that were younger than the ages of deposits in which they formed .
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