Cosmic Ray Exposure (CRE) dating in a wet tropical domain: late Quaternaryfan emplacements in central Sulawesi (Indonesia)

Accurate chronological records are critical for studying the alluvial fan s equences emplaced during local/global climatic changes but, in general, the re are no satisfactory, quantitative dating methods available. In situ-prod uced Be-10 concentrations have been measured in quartz boulders exposed on Sulawesian late Quaternary fan surfaces. These concentrations suggest that the two fan units evidenced by geomorphic study were emplaced during two di stinct major climatic events. The calculated minimum exposure ages imply ab andonment ages of 11 kyr and 120 kyr, for the younger and older units, resp ectively. This study demonstrates that using both the neutron and muon comp onents implicated in the in situ Be-10 production, surficial erosion rates can be estimated and alluvial fans dated. ln particular, it shows that in s itu Be-10 may be used to date fan emplacement during the last 120 kyr under humid tropical conditions, significantly helping to constrain continental palaeoclimatology.