5. Marine Archaeology: Submerged Prehistory

5.1. Overview

  1. The data available for the submerged prehistoric assessment includes:
  • Innomar parametric SBP and Sparker 2D UHRS (Ocean Infinity, 2022).
  • Interpretation reports, including:

–           interpretive Report: SSE Scotwind: Geophysical and Environmental Survey E1E. Produced for SSE Renewables (SSER) (Ocean Infinity, 2022);

–           geotechnical investigations, including boreholes and vibrocores, and seismic surveys undertaken by the BGS (Gatliff et al., 1994); and

–           a review of prehistoric archaeological remains within Strategic Environmental Assessment Area 1 (SEA1) (Flemming, 2003).

  • Research papers and publications including:

–           United Kingdom offshore regional report: the geology of the central North Sea (Gatliff et al., 1994);

–           Marr Bank Sheet 56° N - 02° W Quaternary Geology (BGS, 1985); and

–           Offshore Geoindex (BGS, 2014).

5.2. Geology

  1. The geological processes which form a sequence of seabed deposits provide baseline information to provide an understanding of the potential for submerged prehistoric archaeology to be found within the marine archaeology study area. This section therefore describes the seabed geological sequence and seabed topography within the marine archaeology study area, as a foundation for the sections which follow. It has been informed by a characterisation of the results from the site-specific geophysical survey, as described in section 4, and by relevant data and documentary sources.
  2. The marine archaeology study area lies within the north-western North Sea. Bedrock within the marine archaeology study area is varied. In the central part of the marine archaeology study area Palaeocene mudstones, sandstones, and lignite are noted, while to the west and in two central pockets lie Cretaceous chalks. The eastern part of the marine archaeology study area is characterised by siliciclastic, argillaceous and undifferentiated sandstones of the Eocene to Pliocene eras.

5.3. Quaternary Sequence

  1. Seismic data from the marine archaeology study area demonstrates that Quaternary units overlay the bedrock, including both Pleistocene and Holocene deposits (MSDS, 2023). Together these units average 50 m in thickness across the marine archaeology survey area. This is corroborated by the BGS (2014).
  2. The ages of Marine Isotopic Stages (MIS), British conventional terminology for Quaternary stages, and relative climatic regimes are given in Table 5.1   Open ▸ . The ages are given in thousand years (ky) Before Present (BP). The general association of Quaternary stages and their archaeological periods are shown in Table 5.2   Open ▸ . The Quaternary sediment deposit sequence within the marine archaeology survey area is shown in Table 5.3   Open ▸ . It should be noted that the information presented in Table 5.3   Open ▸ is based on modelling and analysis of the SBP data. Future programmes of geotechnical survey can be designed to confirm the presence of identified units in the latest ground model. The methodology for future geotechnical surveys and analysis that occur post-consent will be covered in method statements and appended to the WSI and PAD and agreed by HES prior to any operations.

 

Table 5.1:
Marine Isotopic Stages, Ages, British Terminology, and Relative Climatic Regime (based on Historic England (no date); dates from Lisiecki and Raymo (2005))

Table 5.1:  Marine Isotopic Stages, Ages, British Terminology, and Relative Climatic Regime (based on Historic England (no date); dates from Lisiecki and Raymo (2005))

 

Table 5.2:
Quaternary Stages, the Holocene Epoch, and their Archaeological Associations

Table 5.2: Quaternary Stages, the Holocene Epoch, and their Archaeological Associations

 

  1. As can be seen Table 5.3   Open ▸ , Unit 40 is thought to represent the earliest Quaternary deposit within the marine archaeology survey area and has been tentatively correlated with the Aberdeen Ground Formation which was laid down 2.52 million BP to 500,000 BP (MSDS, 2023). The Aberdeen Ground Formation is an Early to Middle Pleistocene unit with a varied depositional environment. The date range of the formation suggests some contemporaneity with some of the earliest hominid activity in the UK such as in Happisburgh (Westaway, 2011; Historic England, 2023) and Boxgrove (Pope et al., 2020) but it represents low archaeological potential as it predates the earliest evidence of human activity in Scotland.
  2. Unit 30 lies above Unit 40. The facies of Unit 30 indicate deposition in an ice-proximal environment, for example as a glaciolacustrine or glaciofluvial deposit, with evidence of deformation suggesting glaciotectonic actions within the unit (MSDS, 2023). Due to the glacial character of the unit, it is thought to represent low archaeological potential.
  3. Unit 20 lies above Unit 30. Internally the unit is complex, with well-ordered stratigraphy in places, showing evidence of bedding within channel systems but elsewhere in the marine archaeology survey area the unit is chaotic, and evidence of deformation associated with glacial action is noted (MSDS, 2023). The evidence of chaotic facies potentially associated with diamicton deposits are identified particularly along the southern part of the marine archaeology survey area.

 

Table 5.3:
Quaternary Sequence of Deposits in the Marine Archaeology Survey Area

Table 5.3: Quaternary Sequence of Deposits in the Marine Archaeology Survey Area

 

  1. Together, both Unit 30 and Unit 20 are correlated with the Marr Bank Formation, laid down during the Devensian Glaciation (122,000 - 10,000 BP, MIS 5-1). A BGS core (BGS BH74/07) taken 20 km to the north-east of the Array gave a date of 17,734 +/- 480 BP (minimum age) for the deposit (Stoker et al., 1985). The date falls within the Dimlington Stadial (circa 22,000 - 13,000 BP). While the location and extent of the Scottish Ice Sheet is debated, the evidence from Units 20 and 30 indicate complex glacial environments with likely oscillations in the ice sheet (Ballantyne and Small, 2019). The evidence from Units 20 and 30 indicates subglacial, supraglacial, and outwash deposits. Proximity to the ice created a resource-poor polar desert, except perhaps on unglaciated coastlines where fish and marine mammals could have survived (Westley, et al., 2013). Furthermore, the UK is also thought to have been uninhabited during the Dimlington Stadial (Jacobi and Higham, 2009). Therefore, these units are thought to represent low archaeological potential.
  2. Unit 10 overlies Unit 20 and is correlated with the Forth Formation. The formation originated in the Lateglacial and Holocene periods and can be divided into two members; the Largo Bay and St Andrew’s Bay Members. It is not certain which members are represented by Unit 10 within the Array, but the upper deposits represent modern marine sediments. It is possible that the channels that appear have been formed in an outwash plain setting that has been discussed for the Marr Bank Formation were later filled by Forth Formation sediments. Therefore, sea levels are of relevance to the understanding of the potential depositional environment.

5.4. Sea Level Data

  1. The Largo Bay Member of the Forth Formation is thought to have been deposited during the Lateglacial Interstadial, a relatively warm period that occurred towards the end of the last glaciation in Britain (13,000–11,000 BP). Although sea levels were likely regressing on the east coast during this period, deposits within the inner estuaries in eastern Scotland provide evidence of raised marine deposits during this period (Peacock, 1999; Holloway et al., 2002; Stoker et al., 2008). This demonstrates the likelihood that the marine archaeology study area experienced marine to glaciomarine conditions and was therefore uninhabited during this period.
  2. Colder conditions were re-established during the Loch Lomond Stadial (circa 11,000–10,000 BP), creating a now-submerged shoreline, termed the Main Lateglacial Shoreline (Stoker et al., 2008). Deposition of the St Andrews Bay Member of the Forth Formation is thought to have begun during this period and continued throughout the Holocene (Stoker et al., 2008). The deposit represents shallow marine or estuarine environments; the estuarine elements indicate broad archaeological and palaeoenvironmental potential associated with the Forth Formation that spans the late Upper Palaeolithic and Mesolithic.
  3. To the south-east of North Berwick (120.38 km to the south of the Array), the Main Lateglacial Shoreline was encountered at a depth of between -27 m and -18 m Ordnance Datum (OD). The Array lies between -63.82 m and -88.66 m Lowest Astronomical Tide (LAT), (approximately between -61.6 m and -86.4 m OD) and so is likely to have been submerged during the St Andrews Bay depositional period and therefore suggests very limited potential for archaeological remains. Additionally, the glacial conditions of the region during this period would have been unfavourable for human habitation.
  4. The marine archaeology study area fluctuated between glacial and marine conditions during the Devensian and Holocene periods. While the area may have seen periods of sub-aerial exposure (e.g. during active phases as a glacial outwash plain), such environments are not associated with human activity; conversely, any archaeological material may have been at least reworked, if not obliterated during periods of ice sheet expansion.