Microfossil and geochemical evidence for the Storegga tsunami at Budle Bay, Northumberland, UK

Evidence for the Storegga tsunami, which was generated by one of the world’s largest submarine slides, is well documented in Scotland, but the southerly extent of tsunami inundation in the UK is far more uncertain. Here, we combine new sedimentological, geochemical, microfossil, and ground-penetrating radar datasets to investigate the origins of two sand beds at Budle Bay, Northumberland. The lower of these two sand deposits is a fine- to medium-grained sand that fines upwards, is dominated by fragmented marine diatom taxa, and is characterised by elevated calcium concentrations. Two radiocarbon dated samples provide minimum age constraints on the timing of the deposition of the lower sand at around 8120–8380 cal yr BP. It is tentatively interpreted as being deposited by the Storegga tsunami. The upper sand bed is generally finer grained than the lower sand, and the calcium concentrations are considerably lower. One hypothesis is that the upper sand was deposited by the 1953 CE storm surge, but additional chronological control is required to test this interpretation. Our findings highlight the challenges associated with differentiating between storm and tsunami deposits and confirm the localised nature of preservation of Storegga tsunami deposits.