Free and non-crystalline Fe-oxides to total iron concentration ratios correlated with 14C ages of three forest soils in central Taiwan

Three forest soils (Paleudult (Pedon 1), Dystrochrept (Pedon 2), and Hapludult (Pedon 3)), located on elevations ranging from 625 to 2350 m in central Taiwan, were selected to investigate the correlation between different iron forms (i.e., free Fe-oxides (Fed), noncrystalline Fe-oxides (Feo), total Fe (Fet)) and 14C ages as well as their vertical distribution within diagnostic soil horizons. The 14C ages increased with increasing depth in each pedon. The percentage of the total (Fet) extracted by dithionite (Fed) increased with the 14C age of the alkaline insoluble organic (humin) fraction of the soil horizons, as did the difference between Fed and Feo (assuming crystalline Fe-oxides form). Total amounts of Fe (Fet), however, were not related to the 14C ages of different soil horizons. Statistical analysis indicates the R2 of Fed/Fet and (Fed-Feo)/Fet ratios to 14C ages are 0.938 and 0.926 (Pedon 1, n = 6), 0.892 and 0.756 (Pedon 2, n = 4), and 0.914 and 0.910 (Pedon 3, n = 5), respectively. The data presented in this study suggesting that the ratios of different forms of iron oxides are highly correlated with the age of soil horizons may be useful as relative age indicators in other areas. [PUBLICATION ABSTRACT]