Doggerland was a landmass occupying an area currently covered by the North Sea until marine inundation took place during the mid-Holocene, ultimately separating the British landmass from the rest of Europe. The Storegga Event, which triggered a tsunami reflected in sediment deposits in the northern North Sea, northeast coastlines of the British Isles and across the North Atlantic, was a major event during this transgressive phase. The spatial extent of the Storegga tsunami however remains unconfirmed as, to date, no direct evidence for the event has been recovered from the southern North Sea. We present evidence of a tsunami deposit in the southern North Sea at the head of a palaeo-river system that has been identified using seismic survey. The evidence, based on lithostratigraphy, geochemical signatures, macro and microfossils and sedimentary ancient DNA (sedaDNA), supported by optical stimulated luminescence (OSL) and radiocarbon dating, suggests that these deposits were a result of the tsunami. Seismic identification of this stratum and analysis of adjacent cores showed diminished traces of the tsunami which was largely removed by subsequent erosional processes. Our results confirm previous modelling of the impact of the tsunami within this area of the southern North Sea, and also indicate that these effects were temporary, localized, and mitigated by the dense woodland and topography of the area. We conclude that clear physical remnants of the wave in these areas are likely to be restricted to now buried, palaeo-inland basins and incised river valley systems.

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Doggerland was a land mass occupying an area currently covered by the North Sea until marine inundation took place during the mid-Holocene, ultimately separating the British land mass from the rest of Europe. The Storegga Slide, which triggered a tsunami reflected in sediment deposits in the Northern North Sea, North East coastlines of the British Isles and across the North Atlantic, was a major event during this transgressive phase.The spatial extent of the Storegga tsunami however remains unconfirmed because to date no direct evidence for the event has been recovered from the southern North Sea. We present evidence that Storegga associated deposits occur in the southern North Sea. Palaeo-river systems have been identified using seismic survey in the southwestern North Sea and sedimentary cores extracted to track the Mid Holocene inundation. At the head of one palaeo-river system near the Outer Dowsing Deep, the Southern River, we observed an abrupt and catastrophic inundation stratum. Based on lithostratigraphic, macro and microfossils and sedimentary ancient DNA (sedaDNA) evidence, supported by optical stimulation luminescence (OSL) and radiocarbon dating, we conclude these deposits were a result of the Storegga event. Seismic identification of this stratum to adjacent cores indicated diminished traces of the tsunami, largely removed by subsequent erosional processes. Our results demonstrate the catastrophic impact of Storegga within this area of the Southern North Sea, but indicate that these effects were temporary and likely localized and mitigated by the dense woodland and topography of the area. We conclude clear physical remnants of the wave are likely to be restricted to inland basins and incised river valley systems.

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The use of metagenomic datasets to support ancient sedimentary DNA (sedaDNA) for paleoecological reconstruction has been demonstrated to be a powerful tool to understand multi-organism responses to climatic shifts and events. Authentication remains integral to the ancient DNA discipline, and this extends to sedaDNA analysis. Furthermore, distinguishing authentic sedaDNA from contamination or modern material also allows for a better understanding of broader questions in sedaDNA research, such as formation processes, source and catchment, and post-depositional processes. Existing tools for the detection of damage signals are designed for single-taxon input, require a priori organism specification, and require a significant number of input sequences to establish a signal. It is therefore often difficult to identify an established cytosine deamination rate consistent with ancient DNA across a sediment sample. In this study, we present MetaDamage, a tool that examines cytosine deamination on a metagenomic (all organisms) scale for multiple previously undetermined taxa and can produce a damage profile based on a few hundred reads. We outline the development and testing of the MetaDamage tool using both authentic sedaDNA sequences and simulated data to demonstrate the resolution in which MetaDamage can identify deamination levels consistent with the presence of ancient DNA. The MetaDamage tool offers a method for the initial assessment of the presence of sedaDNA and a better understanding of key questions of preservation for paleoecological reconstruction.