Summer drought in south and west Wales reveals new archaeological sites

There were more archaeological surprises this year for the Royal Commission’s aerial archaeologist, as  widespread hot weather in June and July parched grasslands and showed ‘cropmarks’ in ripening fields of wheat. 



Figure 1: Right place, right time. Known cropmark of an Iron Age defended enclosure (upper centre) north of Cardigan, photographed from the air as it is harvested. In an hour or two the site will be cropped, and will disappear until the next dry summer (Crown Copyright RCAHMW, 23 July 2014).

Dr Toby Driver explained:  ‘Despite the hot weather, frequent rain showers in many parts of Wales meant that cropmarks and parchmarks did not develop everywhere. Only in the south and west, across Pembrokeshire, Carmarthenshire and Glamorgan did the persistent drought reveal scores of prehistoric and Roman sites. Parchmarks of the Roman road running west of Carmarthen, as far as Wiston in Pembrokeshire, were seen for the first time since 1994 showing just how dry it got in the south-west.’

Dr Driver continued. ‘At the Royal Commission we have to be responsive to changing weather and crop conditions each summer. As the photo of the enclosure north of Cardigan shows, an hour either side of a flight can make the difference between obtaining a permanent record of a cropmark, or missing it completely.’

Figure 2: The Roman road west of Carmarthen, showing as a parched line approaching Whitland for the first time since 1994 (Crown Copyright RCAHMW, 30 July 2014).

Pembrokeshire held the most surprises, which was astonishing given the number of discoveries made across the county in the 2013 summer drought . As the dry summer of 2014 wore on, this coastal landscape yielded yet more unrecorded prehistoric sites. Close by the Rhoscrowther oil refinery in south Pembrokeshire a splendid concentric prehistoric defended enclosure was discovered in a field of ripening wheat. New defended enclosures of Iron Age or Romano-British type and plough-levelled Bronze Age barrows were recorded near Dale, near Broadhaven, and along the north coast near Carreg Sampson chambered tomb, Trefin.

Figure 3: The ghostly outline of a new Iron Age concentric enclosure near Rhoscrowther, south Pembrokeshire (AP_2014_3228, Crown Copyright RCAHMW, 22 July 2014)

AdFigure 4: Spectacular colours accompanied further discoveries of enclosures and hillforts close to Dale in south Pembrokeshire (AP_2014_3294, Crown Copyright RCAHMW, 22 July 2014).

A number of new sites were also discovered in south Wales, and included an unexpected prehistoric enclosure on a rocky headland at Oxwich on Gower, just south-east of the famous Oxwich Castle.



Figure 5. General view of Oxwich Castle, Gower, with cropmarks of the new defended enclosure in the right foreground (Crown Copyright RCAHMW, 23 July 2014).

Work back in the office to catalogue and record these discoveries will continue at the Royal Commission well into the winter months.

See our online gallery of aerial photographs for further images from our collections.

                                                                                                                             Toby Drive

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Castell Grogwynion … Fort of the white … Ceramics?

The Early Mines Research Group supported by Sarahjayne Clements, CBA bursary holder, RCAHMW, and Keith Haylock, PHD Researcher, Geography Department, University of Aberystwyth, excavating Castell Grogwynion Hillfort.

A small excavation was undertaken at the Iron Age hillfort Castell Grogwynion last week in an attempt to identify a potential Iron Age metal working site located on the northern terrace of the fort. Early mines are fairly elusive archaeologically and searching for them has been the focus of over twenty years’ research by the Early Mines Research Group. Evidence of Iron Age metal working is particularly rare in Ceredigion, despite the importance raw materials evidently held for Iron Age material culture.

Aerial Photograph of the Iron Age hillfort, Castell Grogwynion.

The excavation at Castell Grogwynion was the conclusion of a series of surveys conducted on three north Ceredigion hillforts, Castell Grogwynion, Darren Camp and Pen Dinas, for a research project by Keith Haylock at the Institute for Geography and Earth Sciences (IGES), Aberystwth University, in collaboration with The Royal Commission, and with permission from Cadw.

Using a special portable X-ray Fluorescence (pXRF) ‘gun’ Keith can find out what metals are present in the soils of the hillfort, with the aim of finding high concentrations of prehistoric metal working evidence. This equipment has revolutionised non-destructive archaeological identification of early mine areas, through the detection of metal slag and smelting activities.

Keith Haylock, operating pXRF survey.

The results of the Geophysical Survey taken in 2012. Areas of interest are highlighted with red, 1 = the area excavated.

Out of the three hillforts surveyed only Castell Grogwynion, in English “The fort of the white pebbles”, demonstrated high lead readings, which were focused on the terrace. Geophysical survey in 2012 by ArchaeoPhysica LTD further confirmed this concentration.

To test the nature and date of the lead concentration, Dr Simon Timberlake and the Early Mines Research Group, carried out a limited excavation on the terrace at Castell Grogwynion in early October.

The Early Mines Research Group excavating.

Some of the seventeenth or eighteenth-century pottery recovered at Castell Grogwynion.

Rather than an Iron Age smelting site, far more recent evidence of seventeenth or eighteenth-century lazy-bed cultivation was discovered with lead-glazed pottery and other domestic rubbish tipped into the soil. These findings confirmed that a nearby platform and cultivation terraces within the hillfort, first identified by Louise Barker during the new Royal Commission survey, were indeed the remains of a post-medieval upland cottage settlement.

Post Excavation Analysis.

Post medieval cottage settlements are fairly common in the Welsh landscape, however the structural evidence is rarely accompanied by any artifactual remains. Although Iron Age finds were limited to a single sling shot, it was exciting to discover the sheer quantity of pottery uncovered through the excavation, surprising in such a remote location. Further scanning the pottery with the XRF gun revealed the cause of the initial high metallic reading: the glazing of the pottery contained an unusually high lead content.  The leaching of the lead glaze into the soil was hypothesised to have been the most likely cause of the high metallic readings. The discovery of this pottery demonstrated the importance of XRF for archaeological survey ― it can detect vital and less structural remains including spoil heaps and rubbish dumps, where the most significant artifactual data is often recovered.

All in all it was great to be part of this excavation and watch the story of the Iron Age hillfort unfold and exciting to be part of such important research into the varied uses of new and powerful forms of archaeological remote sensing.
 

Kimberly Briscoe and Sarahjayne CBA Community Bursary Holders, RCAHMW, Castell Grogwynion.

By Kimberly Briscoe, Community Archaeology Placement Holder.


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Welsh drought brings Roman and Iron Age aerial discoveries across the country

Figure 1. A tip-off from a Roman expert studying coin finds in central Wales led to this stunning discovery of a previously unrecorded Roman fort complex, showing as fading cropmarks in fields of wheat near Brecon, Powys (Crown Copyright RCAHMW, 1st August 2013).

The long spell of hot summer weather across Wales has left aerial archaeologists reflecting on some of their most significant discoveries since 2006. A previously unrecorded Roman fort, a Roman marching camp and scores of Iron Age farmsteads and forts have been discovered by the Royal Commission as parched grassland and ripening fields of wheat showed the locations of long-lost monuments. Aerial surveys over Cardiff and Pembroke Castles revealed parchmarks of lost buildings inside these well-visited attractions, while discoveries were made from Wrexham to Pwllheli, and from Haverfordwest to Chepstow.

Aerial archaeologist Dr Toby Driver from the Royal Commission carefully targeted reconnaissance flights in a light aircraft to where the drought conditions were most severe across the length and breadth of Wales. When cropmarks show in drought conditions, the Royal Commission’s aerial survey programme only has a few weeks to record the sites before rain or harvest removes them.

By far the most significant discoveries for Wales have been from the Roman period with a major Roman fort complex discovered near Brecon, and a Roman marching camp discovered near Caerwent Roman town. The Roman fort near Brecon is a rare discovery for Wales and was made following a tip-off from Roman scholar Dr Jeffrey L. Davies, who has worked with Toby on the Abermagwr Roman villa excavations. Toby explained:

‘Jeffrey Davies noticed an anomaly in Roman coin finds near Brecon, reported under the Portable Antiquities Scheme (PAS). He had a hunch that the coins, of the Emperor Claudius, could indicate a lost early Roman fort, and passed a grid reference to me the day before a flight into central Wales. I couldn’t believe my eyes when the pilot and I approached the location and saw fading cropmarks of a major Roman fort complex, lost beneath fields and a road for nearly 2,000 years.’

Other discoveries were made near Caerwent Roman town in south Wales, famously the market town of the Celtic Silures. Toby explained: ‘Close to Caerwent we discovered only the second Roman marching camp in Monmouthshire. These were overnight camps built by Roman soldiers on campaign in hostile territory. Because the campaigns against the tenacious Silures were documented by Roman historians, we expect more camps in south-east Wales than we currently know about. This new camp between Caerwent and Chepstow seems to show a small expeditionary force on manoeuvres, perhaps in the years around AD 50. West of Caerwent we found a remarkable ‘native’ Iron Age settlement. Given the decades of aerial survey in the region around Caerwent, these surprise discoveries show the continuing need for aerial archaeology in Wales.’

Figure 2. A rare discovery: only the second Roman marching camp in Monmouthshire, found between Caerwent and Chepstow, provides new evidence for the famous Roman campaigns against the Silures of south-east Wales. The characteristic ‘playing card’ shape of the camp shows as a cropmark in a ripening field of wheat, and an adjacent field of parched grass (Crown Copyright RCAHMW, 22nd July 2013).

Other discoveries made in the drought include one of the largest and most complex Iron Age defended farms in Pembrokeshire, on Conkland Hill, Wiston, as well as scores of newly recorded Iron Age farms and forts across south Pembrokeshire and in the Vale of Glamorgan, with two discovered close to the well-known Roman villa at Caermead, Llantwit Major. The archival work for the Royal Commission now begins, to catalogue and map the many discoveries and make the information more widely available to the public on its online database www.coflein.gov.uk


Learn more about aerial archaeology in Wales from the recent Royal Commission publication ‘Cymru Hanesyddol o'r Awyr / Historic Wales From the Air’ (RCAHMW 2012, £19.95) Dr Toby Driver, RCAHMW

How ‘cropmarks’  show lost archaeological sites

‘Cropmarks’ are revealed when grass and arable crops are put under drought stress, and they respond to subtle differences in moisture in the subsoil. Where crops are growing over the buried ditches of lost hillforts or prehistoric farms dark green lines form in fields; conversely buried stonework of lost buildings or old roads form yellow lines in grass and crops. These cropmarks can be seen most clearly from the air, but have to be photographed in a short time window before rain or harvest makes them disappear.
 

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Ffair Haf Penparcau, 13 Gorffennaf 2013

Bryngaer Pen Dinas, Aberystwyth.

Fel rhan o ddigwyddiadau Gŵyl Archaeoleg Prydain eleni, bydd y Comisiwn Brenhinol yn mynychu ffair haf Ysgol Llwyn yr Eos ar Ddydd Sadwrn, 13 Gorffennaf, yr un diwrnod ag y bydd Dr Toby Driver yn arwain taith gerdded i Ben Dinas, y gaer o Oes yr Haearn. Mae’r ysgol ger y Neuadd Goffa, Penparcau, lle bydd y daith yn gorffen. Trefnwyd y ffair i ddathlu pen-blwydd yr ysgol gynradd, Ysgol Llwyn yr Eos, yn drigain oed ac fe fydd gweithgareddau rhwng canol dydd a 9 o’r gloch y nos. Bydd y digwyddiadau’n cynnwys arddangosiadau gan y grŵp ail-greu hanesyddol Normannis, sioe gŵn, dawns stryd, paffio ac ymarfer paffio, corau, a llawer mwy. Bydd y Comisiwn Brenhinol yn cynnal amrywiaeth o weithgareddau cyffrous i’r plant drwy gydol y dydd, gan gynnwys gweithgaredd difyr iawn wedi’i seilio ar gopïau o’r mapiau modern a hanesyddol o Aberystwyth sydd ym meddiant y Comisiwn a chwilen symudol raglenadwy o’r enw Bee-Bot! Dewch atom yn llu i ddarganfod mwy.

I gael rhagor o wybodaeth cysylltwch â Nicola Roberts, Ffôn: 01970 621248, neu Fforwm Cymunedol Penparcau, Ffôn: 01970 611099.

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