On-site excavation and recording methodologies
Developer-funded archaeology has undoubtedly revolutionised our understandings of the Iron Age and Roman periods of South Yorkshire (Chadwick 2008a; Hodgson 2012). It therefore remains key to improving our knowledge of these periods, but some changes to existing fieldwork and sampling practices would prove highly beneficial and would increase the amount and quality of information recovered from commercial investigations. A series of excavation and recording methodologies are proposed below that are based on extensive experience of investigating cropmark landscapes in the Yorkshire region and Iron Age settlements elsewhere by the author and former colleagues. The intention is not to make life more difficult for archaeological fieldworkers. Instead, it is to maximise the amount of information they can recover, and to make their hard efforts more worthwhile. These techniques are not impractical but informed by developer-funded fieldwork, and they have already been undertaken on specific commercial archaeological sites in the Yorkshire region or elsewhere. They are fully compatible with the needs for cost-effective targeted fieldwork, yet they address specific problems of sampling and artefact recovery highlighted in other research agendas (e.g. Haselgrove et al. 2001: 15).
Aerial photographic and lidar analyses and geophysical survey should be routinely used before any evaluation commences. Magnetometry, the standard geophysical technique for surveying extensive areas, is generally good at detecting ‘negative’ features such as ditches and pits on most geologies (Gaffney and Gater 2003: 123-8). Soil resistance survey is better at detecting buried stone walls (ibid.: 146-7). Magnetometry is thus not infallible, and mistaken interpretations can sometimes impact upon subsequent fieldwork. At Wattle Syke in West Yorkshire, magnetometry survey on Magnesian Limestone produced detailed plots of ditches, pits and circular ring gullies from roundhouses (Webb 2003, 2004). A series of large subrectangular features were interpreted as quarry pits and assigned little significance during evaluation – only one or two were investigated with narrow trenches. When the whole area was subjected to a strip, map and record exercise, however, these were revealed as sunken-floored late Roman-British buildings, some with stone walls and floors (Martin, Richardson and Roberts 2013: 9, 72-3, figs 58, 64, 69, 72). The unexpected buildings added to the costs of the full-scale excavation and interfered with the work schedule. It is possible that soil resistance survey may have identified some of these part-stone structures at an earlier stage. Over suspected complex Romano-British enclosures therefore, soil resistance survey could also be utilised to try and identify features such as stone structures in more detail.
Programmes of trial trenching must balance cost-effective approaches to investigation with the need to adequately sample often large areas, as well as targeting specific features identified through aerial photographic analysis, geophysical survey or analytical earthwork survey. A study focusing on rural assessments concluded however that although trenching evaluations usually recorded the presence and date of archaeological remains, identifying their nature, extent and ‘quality’ was often more problematic (Champion, Shennan and Cuming 1995: 40-50). Evaluation of 2–4% of the total area is often inadequate, and figures of 10–20% are more realistic. Linear trenches are ideal when attempting to intersect features such as ditches and trackways, but they may provide inadequate insights into the interiors of enclosures and the possible presence of pits, postholes and structures. It may be difficult to identify structural features within narrow trenches. Some flexibility in approach is therefore required – standard 1.8–2m wide linear evaluation trenches can be retained for identifying field system ditches and trackways, but for enclosures and suspected buildings it might be preferable to open up wider or squarer trenches instead so that more complex features can be identified, interpreted and their archaeological potential assessed more easily. Strip, map and record approaches ahead of major development schemes are a much better means of assessing and preparing costings for the numbers of features and likely quantities of finds that will be encountered.
When sites are stripped of topsoil prior to excavation, it is often the case (particularly on Sherwood Sandstone sand and gravels) that trenches and open areas might need to be left for a week or more before archaeologists record and excavate them. This allows time for archaeological features to ‘weather out’ and become more obvious through the effects of rain and sunshine. This would also avoid any problems of the initial under-representation of features as occurred during the Pre-Construct Archaeology (Lincoln) investigations at St Wilfried’s Road, Cantley, when less experienced archaeologists oversaw soil stripping (Daley 2007: 6). There are potential Health and Safety issues with this, however, in areas where there is public access, so this might not always be possible (J. Richardson pers. comm); unless individual trenches are surrounded with fencing and have appropriate warning signage in place. There is also a very real problem with commercial units being able to recruit experienced site staff at present, which anecdotal evidence suggests is inevitably impacting upon the ability of some field staff to identify and investigate archaeological deposits and features.
Prior to the excavation of enclosures, those areas should be rapidly fieldwalked. During topsoil stripping of the interiors of suspected ‘domestic’ enclosures, machining should proceed cautiously in spits in case there are concentrations or spreads of artefacts, charcoal and burnt stone surviving within the topsoil or subsoil, as may be the case even on previously cultivated sites. If identified during machining, then some topsoil or subsoil could be left in place and intensively sampled by hand and metal detector for artefacts that might otherwise be machined away. Possible middens and artefact spreads might be detected in this way, as was the case at Scrooby Top (Davies et al. 2000). If the initial results proved disappointing the remaining soil could always be machined down to undisturbed natural subsoil as usual. This might be especially productive on sites that might not have been deeply ploughed or where colluvium or alluvium has been deposited above archaeological deposits.
Similarly, where aerial photographic evidence or the results of geophysical surveys suggest the presence of roundhouses within enclosures, then machining should again proceed extremely gingerly, with 0.10–0.15m of topsoil and subsoil left in place above the expected structures. Hand excavation and 3-D plotting of artefacts should then proceed. If results are disappointing, then normal machining can be resumed. Roundhouse ring gullies and all internal features should be 100% excavated, with extensive palaeo-environmental bulk sampling. The interiors of roundhouses should be subjected to phosphate sampling and magnetic susceptibility testing as a matter of routine, and soil aDNA, soil lipid analyses and other geochemical analyses could be attempted where soil conditions are suitable.
Field system ditches need to be adequately sampled, and ideally at least 20% of their lengths needs to be excavated. Whilst most interventions typically produce few finds, occasional large dumps of burnt stone, ceramics and other materials may occur in unpredictable locations (see above). Such sampling should be pragmatic and realistic however – if field system ditches produce little material on initial investigation through hand-dug slots, then additional interventions across ditches can be excavated in controlled spits by machine under close archaeological supervision. The sections can always be cleaned up by hand and recorded.
On both developer-funded commercial excavations and research investigations, at least 20% of the total lengths of enclosure ditches need to be sampled through hand-dug sections. Excavation should focus on ditch corners and terminals by entrances, but instead of limited 1–2m wide hand-excavated sections it would be more productive to employ 2–5m wide sections near enclosure entrances and corners. Again, this maximises artefact and bone recovery, as it was these areas that appear to have formed a focus for deposition during the Iron Age and Romano-British periods, whether this was everyday discard or more ritualised behaviour.
The total 100% excavation of enclosure ditches in controlled spits by machine under archaeological observation should then take place, with particular care taken towards the bottom of ditches, which could always be quickly hand-excavated. This methodology should be adopted as standard practice. It produced very positive results when undertaken during the excavations at Wattle Syke in West Yorkshire in 2007 (Martin, Richardson and Roberts 2013: 11). Much greater quantities of animal bone, pottery and other artefacts were retrieved, large numbers of human neonate burials were found, and unsuspected placed deposits of pottery and animal remains were discovered. A previously undetected enclosure entrance invisible on the stripped surface due to a later re-cut was also identified and recorded.
Pits need to be 50% sampled as an absolute minimum, and if any placed deposits or Associated Bone Groups (ABGs) are encountered than the features need to be fully excavated. Possible placed deposits and ABGs need to be recorded in much more detail, in recorded spits if necessary, with detailed working shots and field drawings at scales of 1: 10 or 1: 5. Some of these can then be included in reports and publications. Suspected graves should be gradually excavated in rough spits as is usual fieldwork practice; but running sections should also be left in and drawn, before the fills are taken down once more. In this way, possible evidence for disturbance or re-visitation of the graves in the form of later re-cuts can be identified, as perhaps happened with the Iron Age inhumation burial at Bilham Farm, Brodsworth (McIntyre 2009). The evidence is much more likely to be visible in these temporary but contiguous sections, rather than in plan. This technique has been successfully used on developer-funded prehistoric excavation sites in Wiltshire and elsewhere, and in practice does not take excavators significantly more time (C. Gibson pers. comm).
When excavating funnel-shaped entrances opening out onto alluvial areas, and/or double-ditched trackways at the base of gentle slopes or those surviving as holloways, some topsoil or subsoil could be left in place during machining, perhaps in strips 10–20m wide and up to 0.15m thick. These topsoil or subsoil strips would then be hand-excavated with greater care in order to find any wheel ruts or animal hoof prints that might survive underneath.
Fieldwork staff should have much greater on-site training in taphonomic processes and the recognition of stratigraphic interfaces, particularly on the often-difficult soils and geologies encountered within South Yorkshire. The physical traces of ditch re-cutting episodes need to be identified and recorded in greater detail than at present (Chadwick 1999, 2008a). Examination of section drawings in both unpublished client reports and published monographs and journal articles suggests that in some instances excavators simply did not recognise recuts from differences in the profiles of ditches, or that they drew layer interfaces that were highly unlikely to have been present due to a lack of understanding of how silting and slumping takes place.
The notion of ‘small ﬁnds’ or ‘special finds’ is deeply embedded in field archaeology but is problematic and is rather a redundant hangover from antiquarian traditions. It privileges certain materials over others from the same context, based on contemporary perceptions of ‘value’. Why should a corroded and illegible Roman coin have greater status than a sherd of samian that could potentially be quite closely dated to 25–50 years? If a contextual bag-number system is adopted (q.v. Collis 2001: 84-6; Cumberpatch and Dunkley 1996: 7), then objects can still be bagged separately on-site for specialist conservation if required, but a separate special find numbering system is not required. The analysis and publication of finds could also be less determined by modern categories but instead by their contextual associations (Chadwick 2012: 303; Haselgrove et al. 2001: 15).
Artefact, animal bone, human bone and other specialists should be more closely involved with project planning, excavation and initial post-excavation analyses from the early stages and should visit or be present on larger projects to inform and manage appropriate sampling strategies. Field units should also ensure that small numbers of site staff are sent on training courses in the identification and excavation of artefacts and human and animal remains, although these personnel should not be used by units as substitutes for experienced specialists who will undertake the post-excavation work. Curators should ensure that those involved in archaeological work closely follow appropriate management guidelines for historic environment research.
Many excavation staff in field units are still not adequately trained to recognise the archaeological deposits most likely to produce productive results and may only sample features that ‘look interesting’. Consequently, although concentrations of carbonised grain or waterlogged plant material may be identified, smaller ‘background’ quantities of palaeo-environmental evidence can be missed. On larger projects in particular, on-site finds specialists should be present to inform and monitor the sampling process, and to take more specialist samples for pollen and soil micromorphology analyses. This is also relevant where waterlogged deposits may be encountered, where there may not be adequate expertise amongst site staff, or existing resources to deal with the material.
For larger excavations, curators, consultants, field units and clients must give more serious thought to the possibility of on-site processing of samples before such major projects commence, and the water sources, flotation tanks, silt traps and drying facilities that are required for this. Adequate storage space needs to be assigned beforehand, and field units may find it necessary to rent additional commercial storage space for this. All soil samples should be routinely tested for the presence of hammerscale using magnets (A. Burgess pers. comm.) – some but not all units currently do this. This is a relatively quick technique that has greatly expanded the evidence for Iron Age and Romano-British iron working within South Yorkshire.
Post-excavation and publication
More comprehensive and rigorous post-excavation analyses and data presentation have many practical and financial implications that must be taken into consideration. These include the provision of the necessary contextual data to specialists, along with sufficient resources and time to undertake such work; and closer co-operation between specialists and technical staff in the field units to produce plans, drawings and full stratigraphic matrices. Wherever possible, specialists should be involved with a project from start to finish rather than being allocated specific time slots to carry out analysis of whatever class of data is involved. For larger projects at least, this should involve participation in project planning and the development of sampling strategies before fieldwork commences, regular visits to the site during excavation, assessment of the material recovered and round table dialogues with the director/project manager, supervisor staff and other specialists concerning the research potential offered by the assemblage. The basic identification, cataloguing, spot dating and the selection of material for scientific or other analysis should follow this, and only then full analysis of the data garnered during assessment to examine whatever research questions have been identified as critical. This work might include detailed examinations of distributions across the site, cross-context links, links between different artefact classes and other similar analyses.
It is only after all these stages have occurred that final specialist reports should be prepared. What still happens in practice, however, is that external specialists are often just sent the material to be examined with little or no accompanying stratigraphic and contextual data, and there is usually little or no opportunity to consult with fieldwork staff and the other specialists involved. Such approaches need to change if we are to develop more effective holistic approaches to archaeology.