Articles tagged with: geophysical survey

The Portable Antiquities Scheme

on Wednesday, 27 November 2019. Posted in Archaeology

The Portable Antiquities Scheme (PAS) is a national programme run by the British Museum in partnership with local bodies; in Wiltshire these are Salisbury Museum, Wiltshire Museum, Wiltshire Council and Swindon Museum and Art Gallery. The primary aims of the scheme are to provide a framework by which members of the public can identify and record finds of potential archaeological significance, as well as to encourage awareness of archaeological issues and best archaeological practice. Whilst the scheme is available to everyone, from field walkers to builders, by the nature of their hobby Metal Detectorists find the majority of the archaeological artefacts we record onto our database; and it is our job to help those engaged in the hobby record as much archaeological information as they can, while also minimising disturbance of in situ archaeological remains.

Metal detecting as a hobby is actually highly comparable to fishing and, anecdotally, I have noticed there does seem to be a great deal of overlap between the two groups. Both hobbies are relatively solitary affairs which can require great deals of patience – they both also exploit a resource in our environment, but this is where the similarities begin to end. Whereas fishing is carefully licenced and managed in order to ensure that the exploitation of our river’s fish is sustainable, there is no such monitoring of the archaeological record.

Crucially, and unlike fish, the archaeological record cannot repopulate itself, once a deposit is disturbed and/or artefact removed, the context is lost for good. This is why it is imperative that detectorists behave responsibly as they exploit this resource which, ultimately, belongs to everyone.

Legally speaking, detectorists in England and Wales are only required to report objects which meet the criteria of the Treasure Act 1996, this is a very specifically worded and narrow set of criteria which frequently miss nationally important finds; a recent example has obviously been the Gloucestershire Dog hoard, but more locally this narrow definition has missed a large hoard of Roman pewter, containing a rare and well preserved tank, thankfully reported by the finder. There is more to detecting responsibly than simply making me aware of unusual finds however, and the perception that I would only be interested in nicer finds is something I often run up against.

Hoard: A Hoard of Roman Pewter vessels found by a metal detectorist in North West Wiltshire, unfortunately archaeological assistance was not sought in advance of recovering the hoard. Salisbury Museum/PAS

Unexpected archaeological discovery in Westbury

on Tuesday, 10 September 2019. Posted in Archaeology, Wiltshire Places

Exciting and unexpected archaeological discoveries show how no evaluation process for sites is fool proof. What happens next shows how important cooperation and communication is, particularly for the County Archaeology Service, who are tasked with supporting development AND safeguarding heritage. The critical concept is “significance” – how important are the remains; what is their potential to inform us about the past? Rachel Foster, Assistant County Archaeologist reports:

In 2017 Wessex Archaeology excavated a new housing development north of Bitham Park in Westbury. I had requested this work as a condition of planning permission, based on limited evaluation results. Unexpected discoveries demonstrated the challenges faced by Planning Archaeologists in understanding the significance of archaeological sites based on the results of trial trench evaluation. 

The 2018 National Planning Policy Framework states that local planning authorities should identify and assess the particular significance of any “heritage asset” that may be affected by a proposal. In line with this advice, we often ask for sites to be investigated before the determination of a planning application, so that we have that information. Evaluation usually this consists of geophysical survey followed by trial trench evaluation. The Wiltshire and Swindon Historic Environment Record which contains detail on archaeological sites, buildings and finds, informs our decision making.

Archaeological evaluation can feel like a game of battleships. When geophysical survey goes well, and reveals features that look like potential archaeology, we ask for trenches to be dug and the features investigated by commercial archaeologists.  The aim is to understand the significance of the site by investigating features within the trenches, which is not always so easy:  if geophysical survey has not been carried out or is unsuccessful, then trenches are placed either systematically or randomly across a site and there is potential to miss remains. Today, the trenching is usually a 3-5% sample of the development site but in exceptional circumstances, up to 10% may be carried out.  That sample of trenching should find archaeological remains within a site and provide enough information to understand the importance, extent and significance of any remains.  Results of evaluation will then inform our advice to the planning officer on the impact of the development on archaeological remains. Remains considered to be of national significance are likely to be preserved in situ and not developed, but other remains are likely to be investigate. Early knowledge about archaeology and its potential effect helps the developers manage their risk and adequately budget for excavation costs, as well as post-excavation work and publication.  

The geophysical survey results at Bitham Park didn’t show much other than a few lines representing ridge and furrow remains across parts of the site and a few other possible linear features. This image gives an example of the greyscale plot of the geophysical survey results (magnetromotry).

© Wessex Archaeology

Geophysical survey isn’t always reliable, so I asked for trial trench evaluation prior to determination of the planning application: in some cases, later ridge and furrow can hide earlier remains. As the geophysical survey indicated, there were remains of medieval/post-medieval ridge and furrow cultivation; however, my assessment that there might be more archaeology was correct.  Archaeological features were discovered across several trenches, mostly concentrated in the western part of the site. They included ditches, gullies and pits containing small, worn pottery fragments from the early/middle Iron Age and Romano-British periods (150BC onwards). Nevertheless, the significance and extent of the remains could not be fully understood, so I asked for a second stage of evaluation to provide more data. The extra information would help me define an area for archaeological mitigation – the full excavation of important features.  The results confirmed prolonged and intensive agricultural use from the medieval period (1066- 1540). This had truncated and displaced features and artefacts from the earlier Iron Age and Romano-British periods; however, theses features included and arrangement of post holes representing a possible structure (see trench locations of two evaluation stages below).

© Wessex Archaeology

On the basis of the two evaluations I asked for an area of excavation within the vicinty of where the most significant archaeological features were recorded, in the western part of the site and along a north-south trajectory.

In advance of the housing development an initial area was stripped with contingency and here’s an aerial view of the site below, can you spot anything interesting?

© Wessex Archaeology and Thomson Environmental Consultants

Celebrating 5 years with the Wiltshire Archaeology Service

on Monday, 02 October 2017. Posted in Archaeology

At the end of August I celebrated five years with the archaeology team here at the History Centre in Chippenham.  I thought this a suitable milestone in which to reflect on some of the most exciting discoveries in the central part of Wiltshire (the area I cover), discovered through the advice we give on planning applications.

The Government set out its requirements for the planning system in the National Planning Policy Framework in 2012.  Section 12 deals with conserving and enhancing the historic environment.  The advice we give on planning applications follows this guidance which needs to be relevant, proportionate and necessary. It is important to understand the significance of heritage assets impacted by development, which is why we ask for a proportionate level of investigation to be undertaken prior to determining applications.  Various stages of investigation are carried out. To begin with an archaeological Desk Based Assessment (DBA) pulls together existing information, using as a baseline the Historic Environment Record and other sources where available such as historic maps, aerial photographs, field surveys and site assessment.  The DBA helps to establish the potential for archaeological remains to be present within a development site. Sometimes, there is little existing information available because there have been few investigations within the area.  In such cases geophysical survey is a useful method for revealing unknown archaeological remains within a site.  We get greyscale plots and interpretation plans to help understand what potentially is of archaeological origin. In most cases we ask for trial trench evaluation following geophysical survey. Trial trenching enables us to understand the significance of the archaeological remains which will be impacted by development.  Depending on the heritage asset’s significance (to use NPPF terminology) we may ask for a site to be preserved in situ i.e. not impacted by development, or preserved by record i.e. it gets excavated, the remains assessed and then reported and/or published. The following examples show previously unknown settlements which have been found through such methods.

Westbury
Trial trench evaluation followed a geophysical survey in 2015 which discovered a number of features dating to the Romano-British period including a number of trackways and ditches. The site has yet to be developed.

Melksham
Trial trench evaluation followed a geophysical survey in 2014 which confirmed the presence of a Romano-British settlement. The site is currently being excavated, more detail to follow.

 

At another site in Melksham, a geophysical survey identified a number of features and the trial trench evaluation confirmed remains dating to the prehistoric, Roman, medieval and post-medieval periods. The site has yet to be developed.

Trowbridge
Geophysical survey across a large proposed development site highlighted two sites of particular interest.  Trial trench evaluation confirmed a concentration of early Romano-British ditched enclosures associated with trackways and pits and posthole features which appear to represent settlement remains. The relationship between the two sites is of interest. More ephemeral prehistoric activity was represented in other parts of the site which the geophysical survey did not pick up.

Barbury Castle: Fine Views and Fortifications

on Monday, 31 July 2017. Posted in Archaeology, Wiltshire Places

Iron Age hillforts must be one of the most visited types of archaeological sites in the country.  Recently I have been up to Barbury Castle a couple of times and have been reminded how impressive and commanding this site is, not just because of its massive ramparts, but also its good state of preservation and all of the other archaeological features you can see from here.  It is one of the most impressive of the 35 hillforts we have in the Wiltshire and Swindon area, with panoramic views that take in the Marlborough Downs and the Vale of Pewsey.

Barbury Castle from north west. Aerial photo from 1991. Wiltshire Council

Barbury is located between Wroughton and Swindon and the County boundary, as well as parish boundaries, run through the middle of the hillfort.  The hillfort was built in the Iron Age, probably around 700 BC and is likely to have been continuously used until the Roman invasion in the mid 1st century AD.  It was one of a string of hillforts built close to the line of the Ridgeway, considered to be an ancient long distance routeway.  Three other hillforts, Liddington, Uffington and Martinsell are all intervisible with Barbury.  It is the most developed and most impressive of the Ridgeway hillforts, having double ramparts on the south side and triple on the north side (possibly an unfinished circuit).  In places the banks or ramparts stand over 3 metres in height even now and in the Iron Age would have been topped with wooden palisades and defensive towers.  Located at 262 metres above sea level Barbury was built on the highest point of the local area, a beneficial defensive position with commanding views of the landscapes below.

The ramparts at Barbury enclose an area of about 5 hectares and there were two original entrances that survive today at the east and west sides.  Unfortunately there has been little modern archaeological investigation to tell us details of the lives lived at Barbury.  However, the results of a geophysical survey carried out by English Heritage in 1998 indicate that the interior is littered with hundreds of pits (probably for grain storage) and other features, some of which are the remains of huts or roundhouses.

The interior of the hillfort as well as the ramparts have suffered some damage in the 1940s from the activities of American troops and the Home Guard who were based at the nearby Wroughton Airfield during the war and used Barbury as a training ground.  The original hillfort entrances were unfortunately widened by American troops in order to get their trucks into the interior.  Fortunately, we have a measured survey drawn in 1884 by General Augustus Pitt Rivers, the first ever Inspector of Ancient Monuments, to show how they would have been.

Army basing and the Saxons

on Monday, 08 August 2016. Posted in Archaeology

Archaeological works on the areas for new housing that are part of the Army Basing Project have been going on for some time now. Two of the areas are for new housing at Bulford and Tidworth.  All of the areas both inside and outside the camps have revealed interesting archaeological remains, from periods from the Prehistoric to World War 2. I thought I’d talk about the Saxon cemetery finds from two of the sites for this blog. Both of the sites were excavated by Wessex Archaeology. Due to the subject matter, there are photographs of human skeletons in this blog article.

The site for service family accommodation at Bulford had been evaluated by geophysical survey and trenched evaluation early on. When one of the trenches revealed nearly 17 possible grave cuts, we knew that we had a previously unknown cemetery. The graves in that trench were mostly aligned east-west and were laid out rather than crouched, so we knew that they were likely to be Christian, or at least from the period when Christianity was starting to have an influence. One of the graves was sampled at that point and a radio-carbon date told us that this was a mid-Saxon burial, around about the time when people were starting to convert to Christianity in this part of England. As the cemetery was in an area where houses were planned, it was agreed that the whole cemetery would be excavated. We expected there to be around 50-70 burials. However, when the area was stripped, as part of a bigger area, it became clear that there were a few more than that (just over 160 in the end)!

Aerial shot of the site with topsoil removed

This picture shows the cemetery after the topsoil has been stripped off. It was taken from a drone. In amongst lots of other features are the regularly laid out groups of graves. Typically, we ended up with far more than we thought originally, as the evaluation trenches had sat neatly between some of the rows! The excavation has finished and so now all the post-excavation work is ongoing. We’ll know more about the dates of the burials, the people themselves and how they were related to each other after that is finished.

Not long after the Bulford cemetery was started, work on a small area of excavation at a site in Tidworth started. This was a planning permission that was much older, so the evaluation had been done more than 10 years ago. Based on the results of that work, we were expecting some Roman-British remains (which we did find). However, more of a surprise was that we started to find burials that looked a lot like the ones at Bulford. The excavation area was extended and revealed (eventually) just under 60 burials. Initial radio-carbon dates suggested that these were also mid-Saxon in date. The burial methods were similar to Bulford (although the cemetery was not so carefully laid out) and there were also similar items buried with some of them.

Archaeologists 'Floored' by New Discovery

on Wednesday, 04 May 2016. Posted in Archaeology

In the archaeology service most new archaeological discoveries tend to be through our advice on planning applications.  If a proposed development has the potential to impact heritage assets and in particular those with archaeological interest (as referred to in the National Planning Policy Framework), then we advise planning officers that a programme of archaeological investigation needs to be carried out in order to determine the significance of heritage assets affected by the proposals.  Since I joined the archaeology service in August 2012 there have been some really exciting discoveries through development management, an overwhelming amount dating to the Romano British period.  To name some of the top sites over the last few years that date to this period, we've had a Roman villa in Devizes, a roadside settlement near Beanacre, a high status farmstead outside Chippenham, two farmsteads on the outskirts of Trowbridge...the list goes on.  In fact I have been surprised at just the amount of activity going on during this period in our county. Maybe it's not surprising considering we have some major Roman roads running through (see map below) including the main routes from London to Bath; from Silchester to Dorchester (Port Way); from Lincoln to Exeter (Fosse Way) and from Winchester to Charterhouse (Mendips). The two towns of Cunetio (Mildenhall) and Sorviodunum (Salisbury) lay at important junctions of the strategic road network and other towns of Durocornovium (Wanborough) and Verlucio (Calne) are also known to lie along the road network.

Taken from 'The History of Ancient Wiltshire' Vol 2 by Richard Colt Hoare

Many of you no doubt have read recently in the newspapers or heard on the radio that there has been a major new Roman discovery in the Deverills.  We got a call from Luke Irwin who explained that whilst constructing an electricity cable to one of his outbuildings his workmen stumbled upon some kind of tiled floor surface and the tiles appeared to be quite small and colourful.  He ordered the workmen to stop digging and that is when he contacted us. Of course my initial reaction was that of incredible excitement tempered by the realism, "what are the chances", people often tend to over exaggerate the significance of archaeological discoveries in their gardens. Despite my cynicism I quickly arranged to visit the site the following day with the County Archaeologist, Melanie Pomeroy-Kellinger. Upon our arrival Luke explained that one of his workmen was interested in archaeology so had meticulously cleaned the floor.  When we peered down the cable trench both our mouths must have dropped open and I think we both said at the same time "I don't believe it, you have got a Roman mosaic!!!”  There was no arguing with the clearly distinctive Roman mosaic pattern, a common geometric border pattern known as guilloche.

[12  >>  

logos1

Accredited Archive Service