14C Tephrochronology with Different Fractions of Paleosol Humic Matter at Procida Island, Italy

Abstract

14C apparent ages along with delta-13C values for three different fractions of humic matter (HM) isolated from a suite of four paleosols (PAs) interbedded within tephra are reported. The dated HM fractions were: 1) HA, the easily released humic acids; 2) HAtot, the bulk of humic acids; 3) RES, the insoluble HM. The 14C sequence dated from 13,000-25,000 BP, in agreement with stratigraphy and previous data. Age differences up to 2540 +/- 430 were statistically significant among fractions; their order of magnitude being independent from C content and depth. All the PAs showed a common pattern of among-fraction age variation, 14C agingltrending from RES to HA101 through HA. As the HM fractions exhibited quite comparable delta-13C values (delta-13C = -25.4 +/- 0.2 per mil), it is inferred that the primitive organic matter (OM) input to PAs was dominantly supplied by vegetation of C-3 photosynthetic pathway which underwent complete decomposition during diagenesis.