Past environmental context

A number of authors have provided generic associations between landform, sediment and archaeological and/or environmental features in both terrestrial (Rapp & Hill, Reference Rapp and Hill1998; Howard & Macklin, Reference Howard and Macklin1999; Waddington & Passmore, Reference Waddington and Passmore2006) and marine environments (Ward & Larcombe, Reference Ward and Larcombe2008; Dix & Lambkin, Reference Dix, Lambkin, Oosting and Manders2008; Dix et al., Reference Dix, Lambkin, Rangecroft, Manders, Oosting and Brouwers2009). These associations not only provide a clear geomorphological rationale for identifying areas of archaeological potential (e.g. Gaffney et al., Reference Gaffney, Thomson and Fitch2007; Ward & Larcombe, Reference Ward and Larcombe2008; van Os & Kosian, Reference van Os, Kosian, de Groot and van Os2011; van den Brenk, Reference van den Brenk2012), but can also help identify sites of potential for geological and palaeontological research (see also Knight et al., Reference Knight, McCarron, McCabe and Sutton1999). Antiquarians and archaeologists are used to finding stone artefacts and animal bones within ancient river deposits or at coastlines, either uplifted and now exposed on land, or drowned and located offshore (e.g. Bell et al., Reference Bell, Chisham, Dark, Allen, Rensink and Peeters2006; Bridgland, Reference Bridgland, Gamble and Lawson1996 Bridgland et al., Reference Bridgland, Antoine, Limondin-Lozouet, Santisteban, Westaway and White2006; Howard et al., Reference Howard, Bridgland, Knight, McNabb, Rose, Schreve, Westaway, White and White2007). Equally, they recognise that layers of peat are the remains of the previous land surface in which prehistoric objects and structures can be found. Such associations have formed the basis for provisional interpretations of the archaeological potential of the North Sea (Coles, Reference Coles1998; 2000; Westley et al., Reference Westley, Dix and Quinn2004; Deeben et al., Reference Deeben, Hallewas and Maarleveld2002; Deeben, Reference Deeben2009).

The main area where understanding could be improved is that of the sedimentary history of those deposits in which archaeological remains are typically preserved. As well as the general aspect of improving the chronological control of geological sequences, other aspects include, but are not limited to:

• • improving the definition of the offshore limits of the British and Scandinavian Quaternary ice sheets (e.g. Coles, Reference Coles1998; Carr et al., Reference Carr, Holmes, van der Meer and Rose2006)

• • improving the delineation and description of the variety of post-glacial coastal facies (Ward et al., Reference Ward, Larcombe and Lillie2006) and buried river channels (Fitch et al., Reference Fitch, Thompson and Gaffney2005; Dix & Sturt, Reference Dix and Sturt2011)

• • gaining more evidence on the preservation, age and relative depth of (brackish-water) basal peat that marks the onset of Holocene marine sedimentation in the North Sea (Oele & Schuttenhelm, Reference Oele, Schuttenhelm, Oele, Schuttenhelm and Wiggers1979).

Whilst some work would inevitably include those sedimentary facies that contain archaeological remains, our essential message is to promote work on the Quaternary geology in a broad sense. Indeed we would argue that the identification of contextual deposits is fundamental to identifying these prehistoric assets, and certainly agree with Bell et al. (Reference Bell, Chisham, Dark, Allen, Rensink and Peeters2006) that the most complete and informative sedimentary and palaeoenvironmental sequences are not necessarily associated with archaeological sites themselves. At the same time we applaud the work of Bates et al. (Reference Bates, Bates and Briant2007), which cautions against extrapolating patterns from land to offshore in the absence of any geological investigation, noting that we should anticipate different landscape formation processes and patterns of landscape evolution particularly in those areas of the shallow shelf area formerly occupied by drainage basins during sea-level low stands.

To date, offshore discoveries of palaeontological and archaeological material have largely been revealed as a by-product of the activities of trawlers (Flemming, 2002; see also Ward & Larcombe, Reference Ward and Larcombe2008) and aggregate dredging, the latter recently aided by the implementation of the Protocol for Reporting Finds of Archaeological Interest (see http://www.wessexarch.co.uk/projects/marine/bmapa/dredged-up). Such finds can be spectacular and promote much scientific, regulatory and public interest, but the dredged material usually remains disassociated from the sedimentary source material and the essential palaeoenvironmental context. Placing such finds into geological, geographical and chronological contexts can be a major challenge (see also Ward et al., Reference Ward, Larcombe and Lillie2006; Ward and Larcombe, Reference Ward and Larcombe2008) because these finds are often only roughly located, having been caught on a track of several miles long or located only to a remote area where dredged material was sourced.

The contextualisation of chance finds is possible, however, as demonstrated by the fortuitous discovery of 28 Palaeolithic handaxes at a wharf in the Netherlands (Firth, Reference Firth, Catsambis, Ford and Hamilton2011). In this particular instance, the gravel came from a licensed marine dredging area in English waters known as Area 240 – some 13 km off Great Yarmouth – lying in water depths of about 25 m. Detailed geophysical survey, vibrocoring and grab sampling recovered worked flints within the area where the handaxes were recovered and achieved a detailed understanding of the chronology and palaeogeographic development of the seabed (Tizzard et al., Reference Tizzard, Baggaley, Firth, Benjamin, Bonsall, Pickard and Fischer2011; Tizzard, 2013). These additional surveys demonstrated that it is possible to obtain reliable knowledge about the provenance of such material to help address key archaeological questions, emphasising the importance of focused geological and stratigraphic investigations. However, this work in Area 240 is so far the exception rather than the rule. Such procedures might only be implemented at other sites if they produced equally important material in areas where it could not be avoided by the developer, prompting investigation to offset or compensate for the likely archaeological impacts.

As well as being directed to chance finds, such studies can be used to test the three-dimensional (3D) stratigraphic models developed from regional sub-bottom geophysical datasets, for example in the central and southern North Sea (Gaffney et al., Reference Gaffney, Thomson and Fitch2007; van Heteren et al., Reference van Heteren, Meekes, Bakker, Gaffney, Fitch, Gearey and Paap2014), Irish Sea and Bristol Channel (Gaffney et al., 2011), and the Thames (Dix & Sturt, Reference Dix and Sturt2011). To be fully utilised by the archaeological community, such models require ground-truthing using cores, with associated dating (e.g. Dix & Sturt, Reference Dix and Sturt2011) and palaeoenvironmental analysis. In doing so, progress is made from simply seeking patterns from massed records towards more targeted collection of samples and mapping data.

The Cultural Heritage Agency of the Netherlands (RCE) is currently working on a so-called Indicative Map of Archaeological Values 4D (IKAW-4D) for the seabed (see: http://www.cultureelerfgoed.nl/archeologie/maritieme-archeologie/programma-maritiem-erfgoed/kennisopbouw/project-ikaw-4d-waddenzee). Focusing on the North Sea, Wadden Sea and Markermeer, an indication is made of the archaeological potential for different areas, related over space and time. This last distinction accounts for the dynamics of the seabed that have an effect on the quantity and quality of what may still exist. A combination of these IKAW-4D maps provides some insight in the use of the seabed from the prehistoric period, when it was still terrestrial, and later when the marine environment was used for transport, war at sea and fishing. Furthermore, a pilot study has focused on the geoarchaeological assessment of a part of the Dogger Bank area of the Dutch continental shelf (Erkens et al., Reference Erkens, Peeters, van Heteren, Marges, Vonhögen-Peeters and de Kleine2013), using lithological and geophysical data.

Holocene marine inundation

The most recent drowning of the UK continental shelf may have occurred at or before c. 9000 BP (Eisma et al., Reference Eisma, Mook, Laban, Nio, Shüttenhelm and van Weering1981; Shennan et al., Reference Shennan, Lambeck, Flather, Horton, McArthur, Innes, Lloyd, Rutherford, Wingfield, Shennan and Andrews2000 Fig. 5c), the significance of which is that in many parts of the southern North Sea, early Holocene and Pleistocene sediments from former shorelines and headlands would have been reworked into the surrounding palaeovalleys and depressions (Streif, Reference Streif2004). In order to fully assess the potential extent of reworking of sediments and archaeological materials during the post-glacial transgression, information is needed on coastal and marine sedimentary processes and the changing regional patterns of sedimentation during this period, which are best obtained using the types of geophysical and geological work described above.

Recognising the absence of such information, Ward & Larcombe (Reference Ward and Larcombe2008) used first principles to infer such transformations, noting in particular the major changes in sedimentation driven by the opening of the Dover Straits and, later, the likely widespread erosion of tidal flat and saltmarsh peat deposits resulting from the strong, new, regional tidal regime in the southern North Sea (Austin, Reference Austin1991; Scourse & Austin, Reference Scourse, Austin and Preece1995; van der Molen & de Swart, Reference van der Molen and de Swart2001a,Reference van der Molen and de Swartb; Dix et al., Reference Dix, Cazenave, Lambkin, Rangecroft, Pater, Oxley, Manders, Oosting and Brouwers2010). Broadly, the detrimental impacts on archaeological preservation in the post-glacial southern North Sea region are likely to have been concentrated:

• • in shallow strongly tidal areas near the Dover Strait during its opening and broadening

• • later, in broad tidally dominated areas of open shelf

• • most recently, in shallow nearshore and coastal areas during storms.

Whilst this might appear to imply a very wide spatial spread of likely disrupted archaeological material, there are areas on the continental shelf which probably have good preservation – the key question is where. The presence of freshwater and salt-marsh peat in cores and some dredges, and indeed the discovery of Mesolithic artefacts within patches of these peats (Louwe Kooijmans, 1970/71; Verhart, Reference Verhart and Fischer1995; Peeters & Momber, Reference Peeters and Momber2014), constitute clear evidence of former coastal environments. Other kinds of depositional settings that were considered most favourable for human occupation or use, including infilling valleys, river deltas and some tidal and back-barrier environments, are also likely to preserve archaeological material relatively well, especially if buried reasonably deep.

The preservation of peat deposits clearly indicates that the sedimentary processes of the late transgression and highstand have not removed all traces of the former land surface. As such, there is a discrepancy between larger scale predictions of preservation and fine-scale patterns in reality: large areas of low potential can contain small pockets of preservation depending on local topography, bathymetry, wave and tidal conditions, inundation and burial history. Thus, it is important to define local palaeogeographies and sedimentary history in order to assess the preservation potential of individual areas (Bates et al., Reference Bates, Bates and Briant2007), especially where these sit close to commercially attractive sand and gravel deposits, offshore construction sites (e.g. windfarms, oil rigs, etc.) or other development activities.

Present environmental context

In the southern North Sea, those present-day natural processes with the greatest impact on sedimentation and hence possible reworking of cultural remains are the tides and, to a lesser extent, storm-associated currents (Southern North Sea Sediment Transport Study, 2002; Ward & Larcombe, Reference Ward and Larcombe2008). Modern sedimentation and tidal patterns were essentially established by around 6000 BP (van der Molen & de Swart, Reference van der Molen and de Swart2001b) and under predicted oceanographic conditions for the next century or so, no further major regional changes in bathymetry are expected. However, local seabed changes, such as the migration of tidal sandbanks (Dyer & Huntley, Reference Dyer and Huntley1999), may influence early and mid-Holocene layers by either exposing them for (short) periods or burying them completely. Although burial is beneficial for preservation, it makes discovery much more difficult. Hence, there is a slight paradox in development activities which can disturb archaeological sites, but which can also provide opportunities for discovery.

In contrast, exposed layers and any cultural material within them are vulnerable to a wide variety of deterioration processes (see Ward et al., Reference Ward, Larcombe and Veth1999). The Mesolithic barbed point dredged up in a lump of peat somewhere between the Leman and Ower Banks (Louwe Kooijmans 1970/71; Verhart, Reference Verhart and Fischer1995) is likely to have originated from an exposed surface in the depressions between these banks rather than having been eroded from the banks themselves. Yet the present alignment of these and other large sand banks in the North Sea may have differed significantly during the Holocene. Consequently, the potential for locating archaeological material cannot be limited to depressions. The study of modern sedimentation and changes in the Late Holocene seabed is of the utmost importance not only for estimating the archaeological research potential (although it may help indicate in which areas we can focus studies of exposed Early Holocene and Pleistocene layers), but also regarding the development of management strategies (see also http://www.machuproject.eu/machu_gis_00.htm).

Potential anthropogenic impacts

In addition to understanding the natural context, research is urgently needed to understand and quantify those anthropogenic processes that influence preservation of prehistoric assets. Even where possible, mitigating archaeological impacts in the marine environment can be very expensive. Therefore, it is extremely important to delineate those areas where natural or human processes are most likely to impact archaeological material as well as archaeologically significant palaeoenvironmental contexts. Where prehistoric land surfaces are concerned, ‘archaeological exclusion zones’ can be established in which, for example, aggregate dredging or trawling is excluded. Such an exclusion zone was quickly put in place after the discovery of handaxes within Area 240 and has subsequently been reviewed in the light of targeted archaeological evaluation (see below). Whilst such evaluation methods do provide some test of the value or effectiveness of such zones, more measurable assessments still need to be developed. A preliminary assessment of a range of anthropogenic impacts by Ward & Larcombe (Reference Ward and Larcombe2008) concluded that although a significant proportion of the area of the North Sea shelf is being disturbed, very little of this disturbance is likely to have far-reaching impact on the buried Palaeolithic/early Mesolithic archaeology. However, it should be emphasised that this preliminary conclusion is limited by a paucity of archaeological and palaeoenvironmental data.

Moreover, as noted above, it must also be understood that it is often not just the impact of one anthropogenic process alone that may influence site preservation, but cumulative effects from other natural and human processes like erosion, aggregate extraction and trawling (Ward & Larcombe, Reference Ward and Larcombe2008; Otte, Reference Otte, Manders, Oosting and Brouwers2009). Therefore data and knowledge are needed that assist identification, quantification and distinction of direct and indirect human processes and natural processes, and assess the significance of the combined impacts. Such work should not be driven by models, but rather by question setting and ground truthing. This is by no means a simple task because comparing the impacts between different anthropogenic impacts, which have different spatial, temporal, physical sedimentary and biogeochemical signatures (amongst others), and which themselves are poorly documented in the field, is extremely complex. At present there are few relevant studies being performed which might allow such integration. To begin to resolve this situation calls for careful and intense collaboration between industry (and other stakeholders) and the relevant sciences. With expanding commercial development in the North Sea, the challenge is to minimise the threats and maximise the opportunities for data collection and exchange, monitoring and management of the marine cultural resource. Clearly, a great deal of archaeological and non-archaeological information is required, but is lacking at present.

Who’s asking the questions?

Those with interests in the North Sea marine environment include developers and operators, consultants, regulators, ‘independent’ scientists and other stakeholders. Each of these groups has different aims, perspectives and expectations, with a focus ranging from economic to ecological and to heritage (see also the summary of discussions and drafting groups in Flemming, Reference Flemming2004; Manders et al., Reference Manders, Oosting and Brouwers2009a). The questions that we need to ask and the decisions on how best to manage the marine prehistoric environment need to be determined together. The question of who is asking (and who is providing funding) also has consequences for collaboration (see below). Thus, a first step in developing a practical approach/tools for marine heritage management is the establishment of user requirements and an evidence-based assessment of how these might be met.

Ideally, this should be performed using an ecosystem focus that recognises the human society (past and present) as a central part in the ecosystem, and a need for increased integration across different science disciplines and over a range of scales depending on the question or particular issue of interest (see also Atkins et al., Reference Atkins, Burdon, Elliott and Gregoryc2011). An ecosystems approach can also be useful to predictive modelling for cultural heritage through a better understanding of prehistoric settlement and subsistence systems (e.g. Verhagen & Whitley, Reference Verhagen and Whitley2012). As outlined by Barker (Reference Barker1996), archaeologists (cultural resource management specialists) need to be seen as part of regional planning and management as they were for the REC surveys. Although the ecosystem approach does appear in European management and policy documents (see Atkins et al., Reference Atkins, Burdon, Elliott and Gregoryc2011 and references therein), it is unfortunate that the archaeological heritage was not included within the scope of the recent European Marine Strategy Framework Directive (http://ec.europa.eu/environment/water/marine/directive_en.htm).

Firth (Reference Firth and Flemming2004) argues that there are some commonalities in the fundamental questions that are asked of development-led archaeology, heritage management and the research-orientated community. It is not possible, for example, to undertake development-led, seabed prehistoric archaeology without questioning what might be out there, what it might mean and what ought to be done (Firth, Reference Firth and Flemming2004). Archaeology is pitted against questions of how to proceed and, in the regulator’s assessment, whether the social or economic benefit of a development going ahead outweighs its likely scientific, cultural and environmental impacts. Where a prehistoric land surface or deposit is also valued for other reasons (e.g. as a habitat, a site of geological interest or a source of aggregate), the consideration of special interest (see Archaeological value/significance below) should take into account other public interests in accordance with the guidance offered by English Heritage’s Conservation Principles (English Heritage, 2008).

Recently a research framework for the maritime, marine and coastal archaeology of England has been developed (Adams et al., 2013). It is intended that the research framework will enable long-term strategic planning, inform policy and provide a statement of key research questions for all those involved in the maritime, marine or coastal archaeology of England, from the academic, commercial and voluntary sectors. In the Netherlands, similar questions are raised in the National Research Agenda (NOaA) for many terrestrial areas and for several time periods. A view on submerged areas is currently being developed, building on the North Sea Prehistory Research and Management Framework (NSPRMF; Peeters et al., Reference Peeters, Murphy and Flemming2009) and experience in the context of Maasvlakte 2 (Manders et al., Reference Manders, Otte-Klomp, Peeters and Stassen2008).

Likely ‘threats’ and key uncertainties

In order to consider the likely impacts from any proposed activities, it is of interest to all, but perhaps most especially to the regulator and developer, to establish where cultural heritage might exist and of what nature it might be. A clear understanding of the nature of the threat and its potential magnitude on the underwater cultural heritage is an essential pre-requisite to assessing the risks, as discussed elsewhere by Ward & Larcombe (Reference Ward and Larcombe2008). We have also noted above the need to adopt an ecosystem approach (as outlined by Atkins et al., Reference Atkins, Burdon, Elliott and Gregoryc2011) and to develop predictive frameworks (Verhagen & Whitley, Reference Verhagen and Whitley2012) to develop thinking on such issues. Part of understanding the nature of the threat is to understand the uncertainties, and these are discussed by Roebroeks (Reference Roebroeks2014) and Peeters & Momber (Reference Peeters and Momber2014). In the interim, the increase in development in the waters around the UK has perhaps prompted the increase in the number of guidance and ‘best-practice’ documents for development-led archaeology in the marine and coastal environment. These documents relate specifically to port development, marine aggregate dredging and the offshore renewable energy sector (English Heritage 2006; BMAPA & English Heritage, 2003; COWRIE, 2007; Oxford Archaeology, 2008; Gribble et al., Reference Gribble, Leather and EMU2011) and up-to-date guidance documents could be developed for other development activities such as coastal defence or tourism.

Temporal and spatial scales

Indications are that the submerged North Sea basin represents one of the most extensive but well-preserved early Holocene (Mesolithic) landscapes in Europe (Gaffney et al., Reference Gaffney, Fitch and Smith2009), and the same may be true of the Pleistocene (Palaeolithic) landscape. On land, Lower Palaeolithic lithic and faunal material largely derive from fluvial floodplain sediments, and contextually similar deposits did (and may still) exist in the maritime zone (Hosfield, Reference Hosfield2007; see also Tizzard, 2013; Tizzard et al., 2013). For Mesolithic archaeology, it is possibly coastal peat deposits that are of most interest, not only because they provide a datable proxy but also they contain or preserve beneath archaeological and palaeoenvironmental evidence (Mithen, Reference Mithen and Cunliffe1994; Bailey & Flemming, Reference Bailey and Flemming2008). Thus different archaeological periods may derive from different depositional contexts and these need to be better defined both temporally and spatially (Ward et al., Reference Ward, Larcombe and Lillie2006; Ward & Larcombe, Reference Ward and Larcombe2008; Manders et al., Reference Manders, van Os, Wallinga, Manders, Oosting and Brouwers2010).

Within development-led archaeology, the focus is on small scales. However, individual environmental impact assessments do not necessarily present a good mechanism for identifying the regional picture, for which strategic environmental assessments seem to be more appropriate. A more regional view is presented through implementation of the Strategic Environmental Assessment Directive. A broadly comparable Regional Environmental Assessment process is being followed by the aggregate industry and a zone-based process by the offshore renewables industry (wind farms). At present, because of the unknowns, much of this work can only flag up deposits of possible interest and identify zones of possible archaeological potential. The still relatively rare discoveries of archaeological material may help to advance some working hypotheses about the presence and character of submerged prehistoric surfaces and deposits across wide areas of the North Sea. There is also some argument to draw upon and integrate with archaeological work being undertaken in coastal and estuarine areas (e.g. Deeben et al., Reference Deeben, Hallewas and Maarleveld2002) as well as on land (e.g. Chapman & Lillie, Reference Chapman, Lillie and Flemming2004; Hosfield, Reference Hosfield2007). Local knowledge only makes sense in its regional context; regional knowledge needs to be pinned down using local details. However, the absence of local detail should not prevent the development of specific science questions.

In this regard, recent work on the above-mentioned Area 240 and surroundings is particularly noteworthy. Here, a regional approach has been applied to develop specific scientific questions that can be tested by ground-truthing for artefactual evidence. As noted above, the initial discoveries from Area 240 were fortuitous, but they led to detailed geophysical, geotechnical and archaeological investigations that support elements of the Area 240 assemblage being in primary context in the floodplain deposits of a now submerged and buried channel of the River Yare. Following on from this, BMAPA took the initiative in carrying out a study of the entire palaeocatchment of the River Yare from its upper reaches that still form dry land to the lower reaches beneath the southern North Sea. This study, known as the Palaeo-Yare Catchment Assessment, used the intensive investigation of Area 240 to help interpret previous geophysical and geotechnical data across all the other licence areas in the vicinity (Tizzard et al., 2013). At the same time, sediment samples are being dredged in areas of interest to answer key questions about the presence, distribution and character of Palaeolithic remains in the region as well as the possible effects of natural processes and impacts of previous dredging on these. This innovative, industry-led approach provides an indication of how other regional-scale approaches could develop elsewhere, applying an explicit research focus that is concerned with answering archaeological questions as well as understanding geological context.

Archaeological value/significance

The question of significance as a means of selectivity for historic assets is a major area of debate (Darvill, Reference Darvill, Cooper, Firth, Carman and Wheatley1995; Deeben et al., Reference Deeben, Groenewoudt, Hallewas and Willems1999). English Heritage’s Conservation Principles (English Heritage, 2008) provide very useful guidance. These principles consider that the historic environment comprises places of different values (evidential, historic, aesthetic, communal) and significance; the latter is judged from these values as well as the contribution made by evolutional setting and context. However, these principles are perhaps less than easily applied to the marine environment and/or ancient land surfaces of which we have little evidential knowledge.

Recently, a system for selecting prehistoric land surfaces on the basis of their ‘special interest’ in marine aggregate areas has been proposed (Wessex Archaeology, 2008). Using this system, a prehistoric land surface or deposit will be of ‘special interest’ where it is considered capable of making a distinctive contribution in terms of narrative, associations, respect, aesthetics or current relevance. Consideration should also be given to rarity, representativeness, diversity, potential, survival, documentation, grouping, setting and context, associated collections, exceptional nature and age (Wessex Archaeology, 2008). However, for the North Sea, regardless of whether it is based on intrinsic (objectively measurable) or extrinsic (largely subjective) qualities, the determination of land surface or cultural heritage value remains contentious because it involves quantifying often poorly defined attributes of geomorphology or cultural land surface (see also Knight et al., Reference Knight, McCarron, McCabe and Sutton1999). Hence, the present focus on identifying prehistoric assets, and the means and techniques to detect them is well intentioned, but risks leaning too far towards dealing with the symptom (i.e. doing what we can do) rather than encouraging the development of a cure (doing what we should do). The latter begins by asking what is the nature of the deposit, and then from this, what is its significance.

New techniques and application

At present, there is some focus on the use of remote sensing and high-resolution geophysical techniques for the delineation of submerged and buried land surfaces, with highly visible results (e.g. Gupta et al., Reference Gupta, Collier, Palmer-Felgate, Dickinson, Bushe and Humber2004; Gaffney et al., Reference Gaffney, Thomson and Fitch2007, 2011; Dix & Sturt, Reference Dix and Sturt2011; van Heteren et al., Reference van Heteren, Meekes, Bakker, Gaffney, Fitch, Gearey and Paap2014). These have rapidly increased our potential to interpret spatial context in buried and marine land surfaces. Should any submerged archaeological sites be discovered, the models produced from the application of these techniques will also be useful for yielding quantitative information with which to monitor and manage sites. Future archaeological surveys are likely to contain a similar range of remote geophysical technologies, and may include the use of remotely operated vehicles capable of sampling and excavating sediments around potential or known submerged sites (e.g. Webster, Reference Webster and Ballard2008). Use of such technologies, together with the more familiar direct sampling techniques of marine vibrocoring and drilling, will together assist ground-truthing of geophysical interpretations and predictive models (e.g. Gaffney et al., Reference Gaffney, Thomson and Fitch2007; Dix & Lambkin, Reference Dix, Lambkin, Oosting and Manders2008; Dix et al., Reference Dix, Lambkin, Rangecroft, Manders, Oosting and Brouwers2009; Dix & Sturt, Reference Dix and Sturt2011; van Os & Kosian, Reference van Os, Kosian, de Groot and van Os2011; van den Brenk, Reference van den Brenk2012).

Geophysical data should, wherever possible, be augmented by geotechnical data such as sediment logs. Whilst each core samples a tiny part of the seafloor and sub-bottom sediments, skilful choice of sampling location using sub-bottom geophysics allows sampling of key strata and, critically, of the stratigraphic boundaries. Recent advances in dating of marine sediments using optically stimulated luminescence (OSL) dating (Stokes et al., Reference Stokes, Ingram, Aitken, Sirocko, Anderson and Leuschner2003) and amino-acid racemisation (AAR) dating (Penkman et al., Reference Penkman, Kaufman, Maddy and Collins2008) accompanied by intensive palaeoenvironmental analysis can provide the critical data on palaeoenvironmental character and archaeological meaning with which to test and supplement the geophysically derived models. A recent example is the work of Dix & Sturt (Reference Dix and Sturt2011) in which extensive sampling and analysis of 30 long (< 6 m) vibrocores for palaeo-secular variation (PSV), electron spin resonance (ESR), AAR, OSL and radiocarbon dating was used to build up a chronological picture and long-term evolutionary development of the submerged landscapes of the Outer Thames Estuary back to the early Middle Pleistocene (> 420 ky BP).

OSL dating of the submerged Holocene seabed can also be a useful tool to investigate and monitor erosion and sedimentation, and to determine how much undisturbed original sediment is present (Manders et al., Reference Manders, van Os, Wallinga, Manders, Oosting and Brouwers2009b). With the further advent of new technologies applicable to marine sedimentary ecosystems, such as DNA analysis (e.g. Cooper et al., Reference Cooper, Rambaut, Macaulay, Willerslev, Hansen and Stringer2001; Willerslev et al., Reference Willerslev, Hansen, Brand, Binladen, Gilbert, Shapiro, Wiuf, Gilichinsky and Cooper2003), it would be sensible to consider the establishment of protocols for storing samples in a way that allows these techniques to be used in the future and/or making existing samples (e.g. commercial cores, records, etc.) available more easily and for a wider range of purposes.

Geophysical and geotechnical surveys tend to be very expensive and it has proved effective to use data that has already been acquired by industry. Mapping work in the southern North Sea (Gaffney et al., Reference Gaffney, Thomson and Fitch2007) and the Irish Sea and Bristol Channel (Gaffney et al., 2011) demonstrate very successfully the use of oil-industry shallow-seismic data in mapping the Holocene and post-glacial deposits around the UK. The scope for re-using such industry data, for archaeological and other purposes, has been greatly aided in recent years by the acquisition of geophysical data in digital form, which is now industry standard. In the UK, there has been progress recently to achieve far greater integration of archaeological objectives within non-archaeological surveys, as encouraged by the Aggregate Levy Sustainability Fund (ALSF, see also Bicket, 2011) and as demonstrated by the Regional Environmental Characterisation programme outlined above. Furthermore, networks are being created to facilitate exchange of information about new survey results and planned surveys for the future. Again, in the UK, the Marine Data and Information Network (MEDIN, http://www.oceannet.org/) is acting as a focus for discussion about marine data exchange, and events such as the Conference on Shipping Hydrology (CoSH) are intended to encourage co-ordination and collaboration in directing survey effort. Similar discussion on data exchange and availability has developed in the Netherlands, largely due to the MACHU project.

Opportunities for collaboration

The wide range of interested parties noted above means that there is a wealth of opportunities for collaboration within the individual countries and also across national boundaries. On major schemes, the state may itself be a developer or at least a partner in the development. Just as for local developers, the obligation on the state to similarly consider the environmental consequences of its overarching decisions about development has been formalised in recent years through the Strategic Environmental Assessment (SEA) Directive. The mutual interests of the state, whole industries, individual developers, contractors and academics in addressing archaeological questions is resulting in considerable progress with respect to North Sea prehistory. The most visible vehicle for such advance has been the ALSF, which, from 2002 to 2011, saw the injection of millions of pounds into data acquisition and research relevant to prehistory in the North Sea.

The ALSF has built on a range of current investigations undertaken by the marine aggregate industry, and whilst there has no doubt been a great volume of new data, some would argue that this data acquisition is perhaps leading scientific thinking on the archaeological issues. There are ongoing opportunities to take stock here and develop an overarching strategy, such as that specifically addressing the Palaeolithic (Westley et al., Reference Westley, Bailey, Davies, Firth, Flemming, Gaffney, Gibbard, Ransley, Sturt, Dix, Adams and Blue2013) and Mesolithic (Bell et al., Reference Bell, Warren, Cobb, Fitch, Long, Momber, Schulting, Spikens, Ransley, Sturt, Dix, Adams and Blue2013) (see also Bicket, 2011). Similarly, broad research themes have been outlined in the NSPRMF (Peeters et al., Reference Peeters, Murphy and Flemming2009).

In the UK, equally important archaeologically orientated work has been generated by other industry sectors: coastal erosion and flood risk have motivated extensive regional investigations of archaeological material, including early prehistoric sites, at the coast (http://www.english-heritage.org.uk/professional/advice/advice-by-topic/marine-planning/shoreline-management-plans/rapid-coastal-zone-assessments/), oil and gas licensing proposals have resulted in several reports on prehistoric archaeology in support of Strategic Environmental Assessments (SEAs) (e.g. Flemming, 2002; Wickham-Jones and Dawson, 2006), offshore windfarm proposals have prompted extensive reviews of geophysical datasets and their construction is being accompanied by geoarchaeological investigations of deeply buried sequences (see COWRIE, 2007; Oxford Archaeology, 2008; Gribble et al., Reference Gribble, Leather and EMU2011), port proposals and other coastal developments fringing the North Sea are also being accompanied by geophysical and geoarchaeological studies (Manders et al., Reference Manders, Otte-Klomp, Peeters and Stassen2008), and various research-driven projects are adding to this mix.

Similarly, there is a wide range of efforts currently underway to produce maps of the sea floor, primarily for marine management and conservation purposes (e.g. van den Brenk, Reference van den Brenk2012; see also www.machuproject.eu). Integration of geological, sediment dynamics and archaeological disciplines provides the best opportunity to develop tools, such as predictive maps of archaeological potential and risk, which serve the needs of managers of the marine archaeological heritage (Deeben et al., Reference Deeben, Hallewas and Maarleveld2002; Ward & Larcombe, Reference Ward and Larcombe2008; Deeben, Reference Deeben2009).

Overall it is clear that any regional archaeological framework can and must be undertaken in collaboration with other bodies, bearing in mind the need to balance the assessment of archaeological value and management with other contemporary management issues such as nature conservancy. As such, there is increasingly a need to take a broader, multi-disciplinary approach to deal with problems created by human activities and develop decision support systems to help manage these.