INCREASE IN RADIOCARBON CONCENTRATION IN TREE RINGS FROM KUJAWY VILLAGE (SE POLAND) AROUND AD 993-994

An increase in atmospheric radiocarbon (C-14) content of about 11.3 parts per thousand in the period AD 993-994 was observed in annual tree rings from Japanese cedar (Cryptomeria japonica) and Hinoki cypress (Chamaecyparis obtusa) (Miyake et al. 2013, 2014). Single-year samples of dendrochronologically dated tree rings (English oak, Quercus robur) from Kujawy, a village near Krakow (SE Poland), spanning the years AD 981-1000, were collected, and their C-14 content was measured using the AMS system in the Leibniz Laboratory. The results clearly show an increase of 6.2 +/- 1.6 parts per thousand in the C-14 concentration in tree rings between AD 993 and 994, with a maximum increase of 10.9 +/- 1.7 parts per thousand between AD 991 and 994.