British Archaeology - September/October 2011
plain, and in this direction also lies Wroxeter Roman town, on the eastern side of the river Severn.
A Roman road has long been described as running north-west from the Severn at Wroxeter, before heading west and south-west to Caersws in Wales (Margary route 64 – see box on page 20). Three historic parishes met in the area where this road crossed the Portway at Sharpstone Hill. This was the focus of our investigations, where parts of a 400m length of road were visible as a ridge running through the fields.
Initial removal of the overburden in a 150m wide zone, showed that although some of the route had been badly eroded, other parts had been deeply buried beneath colluvium, soil washed down from higher levels. We selected six areas for detailed hand excavation. This revealed that gullies and rows of stakeholes defined the edges of some (but not all) road phases. We traced parallel shallow ditches on either side of the latest phase road, as well as pits and possible field ditches. The few artefacts (a scatter of coins and Roman pottery from the latest phase, high up in the sequence) seemingly confirmed the evidence from a second century AD settlement at nearby Meole Brace, north of Sharpstone Hill (to which the road was heading), that this was all Roman.
Amongst the areas excavated by hand, one particular section of road had survived remarkably intact within a natural depression. There we recorded four phases of metalled road surface lying beneath a post-Roman trackway. They were constructed on consolidated earth and pebble cores, and cambered for drainage purposes. Beneath them all was a brushwood foundation.
The quality of this preservation allowed us to design an ambitious plan. With scientific techniques rarely used in Roman archaeology, we hoped to increase understanding of the road’s history and its environmental context, and to explain the curious and apparently illogical dog-legged route that the Roman road was believed to follow. Having previously used OSL dating successfully on the ditch and rampart of the early medieval Wat’s Dyke at Gobowen in Shropshire, we thought that this approach might help us with
Vertical section through the roads, with surfaces distinguished by colour. Scientific dating strongly suggests most are pre-Roman (see text). The raw OSL dates are 371–11BC (1), 191BC–AD149 (2), 321–1BC (3), 511BC–269AD (4), 191BC–189AD (5), 611–371BC (6), 261–1BC (7) and 61BC–AD119 (8). Three radiocarbon results date the brushwood: 360–40BC, 180BC–AD60 and 60BC–AD30
Section through all the road surfaces
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the road. Perhaps we could distinguish between a first century military structure, and succeeding phases during the second to fourth centuries, and enhance interpretation of the Wroxeter hinterland and the development of the Meole Brace settlement.
Samples were therefore taken vertically throughout the sequence, so that OSL dating of the sediments could be attempted by Jean-Luc Schwenninger and David Peat. In addition samples of the brushwood foundations, and of charcoal from pits, were sent for radiocarbon dating. Ben Gearey investigated the pre-road environmental context, and we asked Richard Macphail to examine the micromorphology of the road sequence and the inter-related colluvial deposits. Peter Marshall has completed the scientific analyses through Bayesian modelling of the combined radiocarbon and OSL dating in relation to the stratigraphic sequence, refining the chronology of the main events.
All this has delivered an unambiguous iron age date for construction of the road’s first three phases, starting around 200bc, with only the possibility of the uppermost metalled surface being Roman. However, even this is much more likely to have been constructed during the late iron age, and the route’s origins might have been very much earlier.
The presence of charcoal, burnt sand and stones suggests that the original ground surface was cleared of vegetation by fire. Micromorphological analysis revealed dung beetles and churning of wet mud with calcitic dung (faecal spherulites), showing initial use of the route as a track for livestock. The area around the site was apparently open grassland that was probably created or at least maintained by grazing.
A 4.5m wide layer of elder brushwood was laid over this mud. It may have been an attempt to consolidate a route over a zone that became wet, and the unbroken state of the branches suggests that earth was quickly placed over the top. This deposit showed similar micromorphological characteristics
to that below the brushwood, and we have therefore interpreted it as redeposited material used as the foundation (together with the brushwood) for the first road construction. The road surface was in two layers: gravel and small stones in a matrix of silty sand beneath, and river cobbles compacted into this above. This created an all-weather roadway of hard material, some 5m wide embanked about 50cm above the surrounding ground surface in the centre, with both deposits carefully cambered down on either side to help with drainage. The downhill southern side had been kerbed by a gully which contained a row of holes for stakes, the line of a possible hurdle fence.
The river cobbles that had been used for each of the road surfaces were not of local origin, and must have been imported some distance, perhaps from the Severn itself over 3km away, presumably easier than quarrying the hard gritstone of the hill. Marshall’s Bayesian modelling suggests that at 95% probability the original iron age droveway was created around 200–5bc. Successive road constructions followed at 125bc–ad35, 110bc–ad70 and 105bc–ad105, with an 82% probability that this last phase was also iron age rather than Roman. The radiocarbon dating for one pit found beneath the line of the road, and for other pits surrounding it, are bronze age (three combined with the micromorphological evidence for animal dung and trampling, is that it may have been a marker post. The road’s origins might thus lie in a bronze age droveway that extended over the hill, within a landscape already identified as containing occupation and funerary remains from the period. What are the implications of this analysis?
Evidence for well engineered and carefully surveyed roads reaching back through the iron age into the bronze age, naturally raises questions about the nature of the society that planned them. Why were such roads necessary? Clearly simple tracks are sufficient for humans and animals, so
This pattern of construction was followed in successive phases, so that in time the road grew to over a metre high and over 7m wide, a substantial carriageway to accommodate vehicle traffic. The final phase, of late iron age or possibly Roman conquest date, appears to represent repair for wheel ruts rather than a full road rebuilding.
dates with maximum range of 1740–1120bc derived from oak, ash, birch, alder and hazel charcoal). The pit beneath the road was found at the point where the three historic parishes met, and had been dug to accommodate a substantial post about 70cm across. The interpretation we place upon this,
Interpretation of the road’s history
purpose-built roads in Britain would have been predominantly for the benefit of wheeled traffic. Who were the specialists with the skill and knowledge to design and project manage such enterprises? How was this knowledge invested in new generations, and how were such “professionals”
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