Scilly Isles, UK: optical dating of a possible tsunami deposit from the 1755 Lisbon earthquake

We present the results of optical dating of quartz from marine and aeolian deposits on St. Agnes Island, Scilly Isles, UK. The single-aliquot regenerative-dose protocol was used to estimate the equivalent dose in these samples. Proposed tsunami-laid deposits at Big Pool provided ages of 230 +/- 40 and 380 +/- 60 years; both are consistent with an expected age of 244 years. An OSL age of 6 +/- 3 years was obtained on a modern sub-aqueous beach deposit. These results suggest that the OSL signal in the tsunami-laid quartz was completely reset before deposition, and that these sediments can be dated accurately by optical dating techniques. Sand dunes at Bergecooth, 250 m south of Big Pool, were also dated using OSL. These ages indicate phases of aeolian activity at similar to 300 a and 1000 a in the Scilly Isles. (C) 2000 Elsevier Science Ltd. All rights reserved.