Experiments on the taphonomy of tephra in peat

Understanding the taphonomy of tephra (volcanic ash) is crucial to the use of tephrochronology in peatlands. This study uses field experiments on a Scottish peatland to investigate the post-depositional movement of tephra in peat. Experiments were designed to investigate the temporal change in tephra profiles over a 24-month study period, the horizontal distribution of tephra and the microscopic distribution of tephra particles within the peat. Tephra concentration profiles show that the majority of tephra shards are retained within the top cm of peat with small numbers penetrating to a maximum of 6 cm depth. This distribution would be reduced as the peat is compressed with subsequent accumulation. Examination of thin sections from the plots indicates that tephra movement may be dependent on the microscopic structure of the peat, especially porosity. These results provide general support to the use of tephrochronology although further work will be required, particularly in other peat types and environments.