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Location of the Storegga Slides and sites where evidence for the Holocene Storegga Slide tsunami has been found. For details of the sites in the United Kingdom, see Fig. 2.
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All currently known sites in the United Kingdom with evidence for the Holocene Storegga Slide tsunami are described. Information on the altitude, distribution, stratigraphical context, age, particle size profile and microfossil characteristics of the deposits is presented. The tsunami involved a greater area than previously described, reaching a co...
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... paper reviews the evidence in the United Kingdom (primarily Scotland) for a widespread coastal flood in the middle Holocene, the origin of which is attributed to a tsunami generated by submarine sliding on the continental slope off the mid-western coast of Norway. The deposits of this tsunami are arguably known in more detail than for any other palaeotsunami in the world, many sites around the coastlines of the North and Norwegian seas having been described in recent years. This paper brings together all known currently available published and unpublished information on the tsunami in the United Kingdom. Some of this is derived from previous studies in which the tsunami had not been recognised, thus requiring re- interpretation. In addition, new information on the event is described. A United Kingdom perspective on this widespread event is given because the evidence at all sites is similar, and enables a consistent study to be made of the nature, distribution, microfossil content and age of the deposits, which in turn allows inferences to be drawn on their value as a synchronous horizon, including determining the pattern of land uplift and the possible sea surface level offshore at the time. Values for sediment run-up from United Kingdom sites permit inferences to be made on tsunami run-up in the area, while the sediments and their distribution provide some limited information on possible effects on the coastline of the time. It is believed that the consistency of the evidence contained at these United Kingdom sites and the inferences which can be drawn from them on the nature of the tsunami will permit detailed comparisons with evidence for the event elsewhere around the coastlines of the NE Atlantic to be made in due course. Locations around the coasts of the NE Atlantic, where evidence for the Holocene Storegga Slide tsunami is believed to have been found, are shown in Fig. 1. In the United Kingdom, the first discovery of such evidence was probably made by Sissons and Smith (1965), who identified a thin (ca 5 cm) but persistent sand horizon lying within estuarine silt and peat in the western Forth valley, eastern Scotland. They traced the layer over 1.5 km from the river towards the valley side and attributed it to localised flooding of the river. However, the subsequent identification of a similar layer in a similar stratigraphical position and dated at ca 6900– 7500 radiocarbon years BP at other sites in eastern Scotland (Smith et al., 1980, 1983; Morrison et al., 1981; Haggart, 1982; Robinson, 1982), indicated that a more widespread event may have occurred. Smith et al. (1985) and Haggart (1988) proposed that a major North Sea storm surge may have been the cause, but the discovery of an extensive area of submarine slides off the mid- western coast of Norway (Bugge, 1983; Bugge et al., 1987; Jansen et al., 1987), including a major Holocene slide then termed the Second Storegga Slide and dated at before 5000 and probably close to 8000 radiocarbon years BP, thus of broadly similar age to the sand layer in Scotland, persuaded Dawson et al. (1988) and later Long et al. (1989a, b) to propose that a tsunami generated by that slide had occurred. The storm surge hypothesis was rejected on the basis of the singularity of the deposit, occurring within largely homogeneous raised Holocene estuarine silts which had accumulated without any other discernable hiatus over more than 2000 radiocarbon years in some areas (e.g. Sissons and Brooks, 1971), and because storm surges do not produce such widespread and continuous deposits (e.g. Tooley, 1985), but normally produce discrete aprons of sand, often associated with breaches in barrier systems (e.g. Steers, 1953; Steers et al., 1979). Subsequently, further evidence for the tsunami in eastern Scotland was outlined in accounts by Smith et al. (1992, 1999) and Dawson and Smith (1997, 2000). The differences between tsunami and storm surge deposits have since been illustrated by Reinhart and Bourgeois (1989), Goff et al. (2004) and Tuttle et al. (2004), and are discussed in a number of other publications (e.g. Nelson et al., 1996; A.G. Dawson, 1999). Recent studies have shown that the Holocene Storegga Slide is just one of a series of mega-slides (>2000 km 2 ) that have occurred offshore mid-Norway since the end of the Pliocene, with a frequency of roughly 100,000 years over the last 0.5 Ma (Bryn et al., 2003; Solheim et al., in press). These slides involved the movement of large volumes of glaciomarine sediments at late-glacial to interglacial times within the glacial cycle, by retrogressive failure upslope with blocks failing along stratigraphic horizons interpreted as contourite deposits (Solheim et al., in press). The size and initial acceleration of individual blocks will vary during failure, reflecting stress conditions and the physical properties of sediments, only the largest and fastest being sufficient to initiate a tsunami that could reach the United Kingdom. Originally, three episodes of sliding at Storegga were recognised, two during the Holocene, but further studies (e.g. Haflidason et al., 2001; Bryn et al., 2002, 2003) have emphasised the presence of only one major Holocene slide comprising episodes of movement which cannot at present be separated in time. Consequently, the term Holocene Storegga Slide tsunami is preferred here. Many submarine slide-generated tsunami are known to have involved propagation over a wide area (e.g. A.G. Dawson, 1999), and as accounts of the evidence in Scotland appeared, evidence for the same tsunami was identified elsewhere. From Norway, Svendsen and Mangerud (1990) suggested that deposits of the tsunami could be found in isolation basins in Southern Sunnmøre at Almestadmyra and Skolemyra, and later Bondevik (1996) and Bondevik et al. (1997a, b) expanded these observations, dating the event to between 7000 and 7300 radiocarbon years BP. Farther afield, in NW Iceland at Vestfirdir, Hansom and Briggs (1991) identified a raised beach ridge which they dated from peat beneath as having formed ca 6900 radiocarbon years BP and believed could possibly have accumulated during the tsunami. More recently, evidence for the tsunami has been described from an isolation basin on Suduroy in the Faeroe Islands, where the event is dated at sometime between 7300 and 6400 radiocarbon years BP (Grauert et al., 2001). The early studies of the Holocene Storegga Slide tsunami deposits concerned their age, stratigraphical position and microfossil content, but studies of their sedimentology also developed (e.g. Dawson et al., 1991; Shi, 1995; Bondevik et al., 1997b), while more recently Smith et al. (2000) have modelled the pattern of land uplift in mainland Scotland since the tsunami based upon the altitude of the inner margin of the estuarine surface reached directly before the event. Finally, a number of studies ...
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... In a review of previously reported evidence for the SST in the UK, it was found that the tsunami involved an area much greater than known before, namely, the 600 km long coastal section from Shetland to NE England. Associated deposits show strong consistencies, a sheet of fine or fine to medium sand with coarser material at the base, fining-upward sequences, and a general fining-landward trend [30]. Run-up heights were found to be lower along the open coast compared to inlets and the SST was recognized as a major marker horizon in Holocene coastal sequences already at that time [30]. ...
... Associated deposits show strong consistencies, a sheet of fine or fine to medium sand with coarser material at the base, fining-upward sequences, and a general fining-landward trend [30]. Run-up heights were found to be lower along the open coast compared to inlets and the SST was recognized as a major marker horizon in Holocene coastal sequences already at that time [30]. ...
The Storegga slide tsunami (SST) at ca. 8100 ± 100–250 cal BP is known to be the largest tsunami that affected the North Sea during the entire Holocene. Geological traces of tsunami landfall were discovered along the coasts of Norway, Scotland, England, Denmark, the Faroes and Shetland Islands. So far, the German North Sea coast has been considered as being well protected due to the wide continental shelf and predominant shallow water depths, both assumed to dissipate tsunami wave energy significantly, thus hindering SST propagation dynamics. The objective of our research was to clarify if the SST reached the German Bight and if corresponding sediment markers can be found. Our research was based on the in-depth investigation of a 5 m long section of the research core Garding-2 from Eiderstedt Peninsula near Garding in North Frisia known from a previous study. For this, we newly recovered sediment core Garding-2A at exactly the same coring location as core Garding-2. Additionally, high-resolution Direct Push sensing data were collected to gain undisturbed stratigraphic information. Multi-proxy analyses of sediment material (grain size, geochemical, geochronological and microfaunal data) were carried out to reconstruct palaeoenvironmental and palaeogeographical conditions. We identified a high-energy event layer with sedimentological (e.g., erosional unconformity, rip-up clasts, fining-upward), microfaunal (e.g., strongly mixed foraminiferal assemblage) and other features typical of tsunami influence and identical in age with the SST, dated to ca. 8.15 ka cal BP. The event layer was deposited at or maximum ca. 1–1.5 m below the local contemporary relative sea level and several tens of kilometers inland from the coastline within the palaeo-Eider estuarine system beyond the reach of storm surges. Tsunami facies and geochronological data correspond well with SST signatures identified on the nearby island of Rømø. SST candidate deposits identified at Garding represent the southernmost indications of this event in the southeastern North Sea. They give evidence, for the first time, of high-energy tsunami landfall along the German North Sea coast and tsunami impact related to the Storegga slide. SST deposits seem to have been subsequently reworked and redeposited over centuries until the site was affected by the Holocene marine transgression around 7 ka cal BP (7.3–6.5 ka cal BP). Moreover, the transgression initiated energetically and ecologically stable shallow marine conditions within an Eider-related tidal channel, lasting several millennia. It is suggested that the SST was not essentially weakened across the shallow continental shelf of the North Sea, but rather caused tsunami run-up of several meters (Rømø Island) or largely intruded estuarine systems tens of kilometers inland (North Frisia, this study). We, therefore, assume that the southern North Sea coast was generally affected by the SST but sedimentary signals have not yet been identified or have been misinterpreted. Our findings suggest that the German North Sea coast is not protected from tsunami events, as assumed so far, but that tsunamis are also a phenomenon in this region.
... Some water level events were the result of slower, longer-term changes, in response to isostatic and eustatic sea level fluctuations. Others were fast, catastrophic events resulting in sudden sea level rise, such as the Storegga tsunami (c 8150 BP) that would have resulted in some loss of land in what was left of Doggerland (Smith et al 2004;Walker et al 2020). The long-term history of sea level fluctuations at a local scale would have been characterised by a variable combination of these types of events. ...
Hunting and gathering is the longest human adaptation ever to exist. Foraging peoples moved over the planet, encountered every type of habitat, engaged with their environments in flexible and innovative ways, and were witnesses to vast climatic changes. One of the most notable planetary shifts since the Pleistocene is fluctuation in global water levels and its impact on the landscapes it exposed and submerged. This dynamic would have significantly impacted foraging communities across the globe, but neither water fluctuations nor human responses to them were uniform. Rates of water oscillations were variable, including long-term, slow changes, catastrophic events and others that were likely observable on a generational basis. Human adaptations to shifting water levels likely included mobility and changes in subsistence, among others. Further responses, such as the creation and sharing of traditional ecological knowledge about water level events, were likely codified in cultural practices that are not easily discernible in the archaeological record. To address these issues, this paper presents a case study of submerged archaeological sites in the North American Great Lakes, evidence of a hunter-gatherer occupation on a now submerged landscape. Nine-thousand-year-old stone-built hunting sites represent a specific subsistence strategy used during a time of lower water levels, and an archaeologically visible example of traditional ecological knowledge. This project brings together archaeology and virtual reality with indigenous partners and other knowledge holders to explore forager responses to Holocene water levels.
... The submarine landslide triggered at least one tsunami event that impacted the North Atlantic coast. In Scotland, the tsunami impacted around 600 km of coastline, extending several kilometres in land in places [2]. A recent reinterpretation of echosounder survey data of the Storegga slide [3] suggests that the Storegga slide includes two major submarine landslides: the Nyegga slide, which occurred at the end of the last Glacial Maximum around 20,000 years ago, as well as the Storegga slide, with the central section moving around 8150 ± 30 cal. yr BP [4] considered the main contributor to tsunami generation [5]. ...
... As such, they have the potential to inform present day coastal management [7]. Deposits have been found in Norway [8][9][10], Scotland [2,[11][12][13], the Shetland Islands [2,6], the Faroe Islands [14], and Greenland [15]. Studies of palaeotsunami deposits are an important aid in extending the long-term record and recurrence interval of highmagnitude events. ...
... As such, they have the potential to inform present day coastal management [7]. Deposits have been found in Norway [8][9][10], Scotland [2,[11][12][13], the Shetland Islands [2,6], the Faroe Islands [14], and Greenland [15]. Studies of palaeotsunami deposits are an important aid in extending the long-term record and recurrence interval of highmagnitude events. ...
A submarine landslide on the edge of the Norwegian shelf that occurred around 8150 ± 30 cal. years BP triggered a major ocean-wide tsunami, the deposits of which are recorded around the North Atlantic, including Scotland. Ground-penetrating radar (GPR) was used here to investigate tsunami sediments within estuaries on the coast of northeastern Scotland where the tsunami waves were funnelled inland. Around the Dornoch Firth, the tsunami deposits are up to 1.6 m thickness, which is exceptionally thick for tsunami deposits and about twice the thickness of the 2004 IOT or 2011 Tohoku-oki tsunami deposits. The exceptional thickness is attributed to a high sediment supply within the Dornoch Firth. At Ardmore, the tsunami appears to have overtopped a beach ridge with a thick sand layer deposited inland at Dounie and partly infilled a valley. Later, fluvial activity eroded the tsunami sediments locally, removing the sand layer. At Creich, on the north side of the Dornoch Firth, the sand layer varies in thickness; mapping of the sand layer with GPR shows lateral thickness changes of over 1 m attributed to a combination of infilling an underlying topography, differential compaction, and later reworking by tidal inlets. Interpretation of the GPR profiles at Wick suggests that there has been a miscorrelation of Holocene stratigraphy based on boreholes. Changes in the stratigraphy of spits at Ardmore are attributed to the balance between sediment supply and sea-level change with washovers dominating a spit formed during the early Holocene transgression, while spits formed during the subsequent mid-Holocene high-stand are dominated by progradation.
... By ca. 8 ka, North Sea coastal areas were impacted by the so-called Storegga tsunami (e.g. Smith et al., 2004), for which local erosion, depositional and contained proxy information has been recently investigated (Nyland et al., 2021;Blankholm, 2020;Gaffney et al., 2020;Larcombe and Ward, 2018). We do not regard our IM112 or IM012 results to majorly change assessment of tsunami impact (depositional, taphonomical or archaeological) in southern parts of the North Sea, other than reducing the size of Dogger Island at time of impact. ...
... 5,6, Norway e.g. ref. 7, Shetland 6,8 , and the Faroe Islands 9 . Currents in the Storegga tsunami must also have disturbed the seabed and reworked offshore sediments, but to what extent? ...
The 8200-year BP cooling event is reconstructed in part from sediments in the Norwegian and North Seas. Here we show that these sediments have been reworked by the Storegga tsunami – dated to the coldest decades of the 8.2 ka event. We simulate the maximum tsunami flow velocity to be 2–5 m/s on the shelf offshore western Norway and in the shallower North Sea, and up to about 1 m/s down to a water depth of 1000 m. We re-investigate sediment core MD95-2011 and found the cold-water foraminifera in the 8.2 ka layer to be re-deposited and 11,000 years of age. Oxygen isotopes of the recycled foraminifera might have led to an interpretation of a too large and dramatic climate cooling. Our simulations imply that large parts of the sea floor in the Norwegian and North Seas probably were reworked by currents during the Storegga tsunami.
... Despite an apparent scarcity of tsunamis in the shallow North Sea basin, the Shetland Islands have become an important field laboratory in which to study tsunami deposits since the early 1990s (Smith 1993;Bondevik et al. 2003Bondevik et al. , 2005Dawson et al. 2006Dawson et al. , 2020bCosta et al. 2015;Cascalho et al. 2016;Buck & Bristow 2020), with summaries of the findings presented in Smith et al. (2004Smith et al. ( , 2019, Long (2015), Costa et al. (2021) and Bondevik (2022). The original studies on Shetland have played a substantial role in the advancement of tsunami sedimentology and wider tsunami geoscience. ...
... However, there is an increasing concentration of finer particles and organic matter in the upper part of sublayer 3, possibly reflecting the waning stage between two waves, a pattern that has been found in other tsunami deposits of shallow coastal lakes as well (Bondevik et al. 1997;Bondevik 2022). The low concentration and poor preservation of pollen in the basal sand compared with all other facies of the core are in agreement with observations from tsunami deposits in the region (Smith et al. 2004) and elsewhere (Chagu e-Goff et al. 2012). ...
Tsunami deposits around the North Sea basin are needed to assess the long-term hazard of tsunamis. Here, we present sedimentary evidence of the youngest tsunami on the Shetland Islands from Loch Flugarth, a coastal lake on northern Mainland. Three gravity cores show organic-rich background sedimentation with many sub-centimetre-scale sand layers, reflecting recurring storm overwash and a sediment source limited to the active beach and uppermost subtidal zone. A basal 13-cm-thick sand layer, dated to 426-787 cal. a CE based on 14 C, 137 Cs and Bayesian age-depth modelling, was found in all cores. High-resolution grain-size analysis identified four normally graded or massive sublayers with inversely graded traction carpets at the base of two sublayers. A thin organic-rich 'mud' drape and a 'mud' cap cover the two uppermost sublayers, which also contain small rip-up clasts. Grain-size distributions show a difference between the basal sand layer and the coarser and better sorted storm layers above. Multivariate statistical analysis of X-ray fluorescence core scanning data also distinguishes both sand units: Zr, Fe and Ti dominate the thick basal sand, while the thin storm layers are high in K and Si. Enriched Zr and Ti in the basal sand layer, in combination with increased magnetic susceptibility, may be related to higher heavy mineral content reflecting an additional marine sediment source below the storm-wave base that is activated by a tsunami. Based on reinterpretation of chronological data from two different published sites and the chronostratigraphy of the present study, the tsunami seems to date to c. 1400 cal. a BP. Although the source of the tsunami remains unclear, the lack of evidence for this event outside of the Shetland Islands suggests that it had a local source and was smaller than the older Storegga tsunami (8.15 cal. ka BP), which affected most of the North Sea basin.
... cal ka BP (Bondevik et al. 2012); the Garth tsunami at c. 5.500 cal ka BP; and the Dury Voe event at c. 1.500 cal ka BP (Bondevik et al. 2005), although Engel et al. (2023) suggest a slightly younger age for the Dury Voe event of c. 1.400 cal ka BP. Deposits from the tsunamis have been found in Norway (Bondevik et al. 1997a, b;Bondevik and Svendsen 1998), mainland Scotland (Smith et al. 1992(Smith et al. , 2004Dawson and Smith 1997;Long et al. 2016), the Shetland Islands (Smith et al. 2004;Bondevik et al. 2005), the Faroe Islands (Grauert et al. 2001) and Greenland (Wagner et al. 2007). ...
... cal ka BP (Bondevik et al. 2012); the Garth tsunami at c. 5.500 cal ka BP; and the Dury Voe event at c. 1.500 cal ka BP (Bondevik et al. 2005), although Engel et al. (2023) suggest a slightly younger age for the Dury Voe event of c. 1.400 cal ka BP. Deposits from the tsunamis have been found in Norway (Bondevik et al. 1997a, b;Bondevik and Svendsen 1998), mainland Scotland (Smith et al. 1992(Smith et al. , 2004Dawson and Smith 1997;Long et al. 2016), the Shetland Islands (Smith et al. 2004;Bondevik et al. 2005), the Faroe Islands (Grauert et al. 2001) and Greenland (Wagner et al. 2007). ...
... We carried out GPR surveys in the Shetland Islands to characterize the deposits created by these tsunamis. Initial surveys were undertaken in areas where deposits have been described by Bondevik et al. (2003Bondevik et al. ( , 2005, Smith et al. (2004) and Dawson et al. (2020) to establish the reflection characteristics of tsunami deposits in areas with ground truth. Once the signature of the tsunami deposits within the GPR data had been identified, we used GPR to explore a prospective site where there is no previous record of tsunami deposits. ...
We use ground-penetrating radar (GPR) to investigate the geometry, inland extent, and continuity of sand layers interpreted as tsunami deposits in the Shetland Islands, UK. Four sites where sand layers within peat deposits are recorded in previous studies provide ground-truth. In addition, we describe survey results from one site where deposits are not exposed, to test the potential of GPR to identify candidate tsunami deposits in areas that are not well documented. Sand layers can be clearly imaged at all five locations because they are interbedded with peat and the contrast in lithology gives a good reflection on GPR profiles, even very thin sand layers, less than 1 cm in thickness, that are beneath the theoretical resolution of the GPR. 2-D and 3-D surveys show that tsunami deposits appear to drape a buried topography. Most sand layers form continuous reflections although some gaps are attributed to later erosion, most likely by streams. Sand layers have been traced up to 150 m inland and 10 m above the present shoreline which is consistent with data from boreholes. If a similar sized event occurred today it would have a devastating impact on the Shetland Islands.
... The wave spread across the Norwegian-Greenland sea (Haflidason et al., 2005;Bondevik et al., 2005;Harbitz, 1992), affecting a region of 95,000 km 2 (Bondevik et al., 2005). Many tsunami deposits from the Storegga slide-generated wave have been found across the region, including Scotland (Smith et al., 2004;Tooley & Smith, 2005;Dawson & Smith, 2000;Long et al., 1989;Dawson et al., 1988;Long et al., 2016), northern England (Boomer et al., 2007), Norway (Svendsen & Mangerud, 1990;Bondevik et al., 2003;Vasskog et al., 2013), Faroe Islands (Grauert et al., 2001), and Greenland (Wagner et al., 2007). Run-up heights are estimated to be over 30 m in some locations, particularly where the tsunami wave propagated large distances along Norwegian fjords (Vasskog et al., 2013). ...
Tsunamis are a major hazard along many of the world's coastlines. To understand the impact of these events, a sufficiently long record of previous events is needed, which can be provided by their sedimentary deposits. A number of past events have left extensive sedimentary deposits that can be used to understand the hydrodynamics of the tsunami. The ca 8.15 ka Storegga submarine slide was a large, tsunamigenic mass movement off the coast of Norway. The resulting tsunami had estimated run‐up heights of around 10 to 20 m on the Norwegian coast, over 30 m in Shetland, and 3 to 6 m on the Scottish mainland coast. New cores were taken from the Ythan Valley in North‐East Scotland, where Storegga tsunami deposits have previously been found. High resolution sedimentary analyses of the cores, combined with statistical (changepoint) analysis, shows signatures of multiple waves. Moreover, detailed CT scans of the erosional basal surface reveal sole marks called skim marks. Taken in conjunction with the grain‐size and sedimentary fabric characteristics of the tsunami deposits, this indicates that the flow exhibited a high‐concentration basal component, with an initial semi‐cohesive phase, and that deposition was dominantly capacity‐driven. A multiple wave hypothesis is tested by creating a high resolution numerical model (metrescale) of the wave inundation, coupled to a previously published regional model. The inundation model confirms that multiple waves passed over the site in agreement with the sedimentological analysis. The sensitivity of the model to the reconstructed palaeocoastal geomorphology is quantitatively explored. It is concluded that local palaeogeomorphological reconstruction is key to understanding the hydrodynamics of a tsunami wave group in relation to its sedimentary deposit. Combining sedimentological data with high resolution inundation modelling is a powerful tool to help interpret the sedimentary record of tsunami events and hence to improve knowledge of their risks.
... Deposits from this tsunami have been extensively mapped onshore in Scotland (e.g. Dawson et al., 1988;Smith et al., 2004), Norway (e.g. Bondevik et al., 1997), Shetland (Bondevik et al., 2003;Smith et al., 2004), and the Faroe Islands (Grauert et al., 2001). ...
... Dawson et al., 1988;Smith et al., 2004), Norway (e.g. Bondevik et al., 1997), Shetland (Bondevik et al., 2003;Smith et al., 2004), and the Faroe Islands (Grauert et al., 2001). Most likely, currents in the Storegga tsunami must also have disturbed the seabed and reworked offshore sediments, but to what extent? ...
Since the end of the last ice age, no cold snap rivals the one dated to 8200 years ago. Its oceanic response has been reconstructed in part from sediments in the Norwegian Sea and North Sea. Here we show that these sediments have been reworked by currents generated by the Storegga tsunami, dated to the coldest decades of the 8.2 ka event. From a new simulation of the Storegga tsunami we calculated the maximum flow velocity to be 2–5 m/s on the shelf offshore western Norway and in the shallower parts of the North Sea, and up to about 1 m/s down to a water depth of 1000 m. We re-investigated sediment core MD95-2011, from which a large and abrupt 8.2 ka cooling had been inferred, and found the cold-water foraminifera to be re-deposited and 11,000 years of age. Oxygen isotopes of the recycled foraminifera and the content of sand grains, thought to be dropped from ice bergs, might have led to an interpretation of a too large and dramatic climate cooling. Our simulations imply that large parts of the sea floor in the North Sea and Norwegian Sea might have been reworked by currents during the Storegga tsunami.
... Bondevik et al., 1997). The low concentration and poor preservation of pollen in Unit VIIb compared to all other facies of the core is a common observation made in tsunami deposits of the region (e.g.,Smith et al., 2004) and elsewhere (e.g.,Chagué-Goff et al., 2012). ...
To assess the long-term hazard of tsunamis, particularly in regions with a short and fragmented historical record, sedimentary deposits of tsunamis are an essential tool. In the North Sea region, evidence of tsunamis is scarce. The Shetland Islands are an exception, as they contain abundant deposits of the Storegga tsunami (c. 8150 cal. a BP), and additionally more fragmented evidence of younger tsunami events c. 5500 and c. 1500 cal. a BP. Sediments of the youngest tsunami (the "Dury Voe" event) have only been found at two sites so far, marked by thin landward ning and landward thinning sand sheets which are vertically con ned by peat. Here, we present sedimentary evidence for the youngest Shetland tsunami from the small coastal lake of Loch Flugarth, northern Mainland. Three gravity cores of up to 91.7 cm length were taken behind the barrier separating the lake from a shallow marine embayment. The cores show organic-rich background deposition with many sub-cm-scale sand layers, re ecting recurring storm overwash and a sediment source limited to the active beach and uppermost subtidal zone. A basal 13 cm-thick sand layer, dated to 426-787 cal. a CE based on 14 C, 137 Cs and Bayesian age-depth modelling, was found in all three cores. High-resolution grain-size analysis identi ed four normally graded sublayers with inversely graded traction carpets in the lower part of two sublayers. An organic-rich 'mud' drape and 'mud' cap cover the upper two sublayers, which also contain small rip-up clasts. Grain-size distributions show a difference between the basal sand layer and the coarser and better sorted thin storm layers. Principal component analysis of X-ray uorescence core scanning data also distinguishes both sand units: Zr, Fe and Ti dominate the basal sand, while the thin storm layers are high in K and Si. The enrichment of the basal sand layer in Zr and Ti, in combination with increased magnetic susceptibility, may be related to higher heavy mineral content in the basal sand re ecting the additional marine sediment source of a tsunami deposit below the storm-wave base. Based on reinterpretation of chronological data from the two published sites and the chronostratigraphy of the present study, the Dury Voe tsunami seems to be slightly younger, i.e., closer to 1400 cal. a BP. Although the source of the tsunami remains unclear, the lack of evidence for this event outside of the Shetlands suggests that it was smaller than the older Storegga tsunami, which affected most of the North Sea basin.
