Roman Geophysics in South Wales

Dr Tim Young, Teaching Associate

Each spring I train a small group of Cardiff students in the art and science of geophysics using a real research project. Over 260 students have now passed through the course. We have developed projects that have not just investigated archaeological ‘sites’ but the broader landscapes containing them. Landscapes will contain features of many ages, but our particular focus has been the Roman period: a legionary fortress and its surrounding settlement, an auxiliary fort, an industrial centre, a major town, two villas and three other rural farmsteads, all within 35km of Cardiff. 

Between 2000 and 2004 that focus was Caergwanaf, where I was drawn by historical accounts of a slag dump that proved to be enormous, in excess of 10,000 tonnes, placing the smelting into the same league as the largest Roman smelting sites of SE England. Further excitement followed, as the ditches of a previously unknown Roman fort were discovered to the west of the dump. Excavation in 2002 and 2004 by teams from Cardiff showed that the fort was constructed in c.AD75 – 85, with the iron smelting starting around the time the fort was abandoned a decade later and lasting into the early third century. 

We had to take a year away from Caergwanaf in 2001 as Foot and Mouth Disease prohibited access to agricultural land. Instead, we addressed the Roman villa at Ely, set below the Caerau hillfort in a complex multi-period landscape.  

From 2006 to 2011 our focus switched to the Caerleon fortress. Most of what was then known came from development work and the open areas both within and outside the walls remained virtually uninvestigated. The first year of the project looked at Priory Field in the southwest corner of the fortress, identifying both the fortress granaries and a storehouse, later excavated in a joint Cardiff-UCL project (2007 to 2010). Later, still within the fortress, survey revealed an enormous metalworking building, and then then civilian buildings with horticultural plots behind lining the road outside the west gate of the fortress. The most unexpected discoveries were to the southwest of the fortress where a large area of formal buildings was discovered running down the slope towards a quay. This area was investigated through excavations in 2010 and 2011, but much remains unknown about the purpose of this monumental section of the canabae. 

In 2008 and from 2012 to 2014 our research moved to Caerwent, initially ‘tidying-up’ the plans of the Edwardian excavations, but it was a swathe of land over 1.2km long outside the town to the south and west that was our main focus. Caerwent had long been known to have a slightly irregular street system but the survey demonstrated that settlement had originated within an acute road junction, with the nascent settlement developing streets that were arcuate, meeting both the roads orthogonally. With time, however, the town condensed along just one of the roads with its defences cutting the lines of the early streets. 

Since 2015, our interest has been in the Vale of Glamorgan. This work is starting to define the nature of Roman rural settlement there, with its enclosed farmsteads, ‘infields’, droveways and unenclosed areas, together with demonstrating the importance of water supplies. At Ffynnon y Brychau two rectangular enclosures lie to the south of a spring, with curvilinear features around, as well as a post-medieval stone-walled sheep fold, cut by a 19^th century quarry. In the Caermead area a similar story was observed: rectangular enclosures form one of the earlier elements of the settlements, with each sited close to a spring. The springs are even more directly related with curvilinear banked enclosures with internal ditches of uncertain age. The Roman farmsteads are similar in their early phases but have a spectrum of subsequent development, becoming strongly differentiated in the later Roman period. 

Those 260 geophysical beginners achieved a remarkable amount and advanced beyond all expectation the understanding of South Wales in the Roman period. Each site examined produced an exciting revision of understanding and extension of the ‘archaeological site’ beyond that which was previously recognised. The project has fostered the realisation of just how important geophysics is for looking into the apparent gaps in the distribution of archaeological evidence.