ABSTRACT

Radiocarbon dating was performed for the extracted organic fractions (cellulose-rich and humic acid fractions of plant fragment; fulvic acid, humic acid and humin fractions of humus substance) and shell from core sediments of the Erhai Lake, SW China. The ¹⁴C dating results reveal that there are considerable differences, but there apparently is a humic acid ≤ humin < fulvic acid fraction sequence of ¹⁴C age increase. The variability in radiocarbon ages of organic fraction of lake sediment suggests that special caution is necessary when radiocarbon ages of bulk sediments are used. The linear correlation between ¹⁴C age of allochthonous terrestrial macrofossil (plant fragment and shell) and depth indicates roughly a constant sedimentation rate of ca. 0.7 mm yr^-1 in central Erhai Lake since 4500 yr BP. The ¹⁴C ages of the autochthonous humic acid fraction are 210∼4800 yr shift from “the true ¹⁴C age” obtained by interpolating the corresponding horizontal level to the above ¹⁴C age-depth correlation. Such age difference may be alternatively attributed to a uniform reservoir effect (most likely ca. 300 yr). The period with large ¹⁴C age shift synchronizes with the period of changes in δ¹³C and ARM intensity and ARM/susceptibility values.