Published online by Cambridge University Press: 02 October 2018
Measurements of the radiocarbon (14C) and tritium (3H) activity in a 5.8-m-long ice core from the Saarhalle, Dachstein-Mammoth Cave allowed a substantial revision of previous opinions concerning the age of the ice block, and provide useful experience that may be applied to future 14C dating of cave ice deposits. The stepped combustion technique results in a remarkably older radiocarbon age for the 800°C than for the 400°C fractions of the carbonaceous matter from ice layer samples. The highest tritium activity (37.2±1.2 TU) can be linked to the period of anthropogenically increased tritium activity of atmospheric precipitation at the mid-1960s, providing a well-dated radiochemical reference horizon. Compared the 3H-based extrapolated ages of two shallow samples to the expected atmospheric signal an average 14C reservoir bias of ~1500 BP was obtained for the insoluble organic fraction combusted at 400°C. The conventional 14C age measured for the 400°C fraction of the deeper samples has been corrected with the average reservoir bias. The median calibrated age of the deepest analyzed sample of the ice profile is ~1830 cal BC and a linear extrapolation to the bottom ice layer gave 2590 cal BC, making the Saarhalle ice block among the oldest dated cave ice deposits known in the Alpine domain.
Selected Papers from the 2nd Radiocarbon in the Environment Conference, Debrecen,Hungary, 3–7 July 2017