Holocene aeolian morphogenetic phases in Southern Italy: Problems in ~(14)C age determinations using terrestrial gastropods

摘要

Radiocarbon age determination is one of the most important methods for dating Holocene events. In particular, it has been used to reconstruct the sequence of aeolian morphogenetic phases along the Apulia and Basilicata coasts (Southern Italy). In these areas, three main Holocene morphogenetic phases have been recognized using radiocarbon data obtained from sub-fossil terrestrial gastropods, archaeological data and OSL analyses: those of the Middle Holocene period, of the Greek-Roman time and of the Middle Ages. Sub-fossil terrestrial gastropods have been considered suitable indicators in the detecting Holocene climate-environmental changes. However, it is well-known that they could show problems as chronological indicators mainly due to aging effects induced by: (ⅰ) micro-particles of calcite/aragonite in the shell structure, derived from the local substratum and (ⅱ) a variation of CO_2 content in the plants eaten. In order to verify these hypotheses, living terrestrial gastropods were collected from coastal areas and analysed using AMS. The results indicate that many living gastropods gave ages of 1500 years older than those expected, thus confirming the aging effect. As ~(14)C ages of Middle and Late Holocene aeolian morphogenetic phases, obtained from terrestrial gastropods, seem to be confirmed by archaeological data and OSL analyses. The aim of this work is to verify if the age anomalies obtained from modern gastropods could be extended to the entire Holocene period.