Geoarchaeology at the Bradford Kaims

Becky Scott – Assistant Supervisor (Geoarcheology) and PhD Candidate, University of Reading

Following on from our blog post about the geophysical survey carried out at the Kaims this year, we have been busy ‘ground-truthing’ the anomalies seen just to the North of Trench 6 – that is, identifying whether the magnetic anomalies seen on the survey are archaeological features or not. Of course, like most endeavors, we have had varying degrees of success! The first few test pits that were dug contained nothing but colluvium (sediment that has been deposited downslope, often known as hill or slope wash) even after digging up to a metre. We then decided to take some cores around the area that showed the magnetic anomalies to the North of Trench 6 using the Dutch auger, which is essentially a long pole about 1 metre long with a T-handle and a screw-like head at the bottom which collects and retains sediment. Dutch augers are particularly useful for hard and wet sediments so worked very well through our silty clay colluvium. After taking a number of cores (with the excellent help of our two Young Archaeologists Club competition winners!) we eventually came up with some lovely layers of charcoal and burnt material, so we set to work digging three more test pits. Two of these test pits were more much more successful, particularly Test Pit 75 which showed a charcoal layer almost 30cm thick (see Figure 1 below).

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Figure 1. SE-facing section of TP75 showing three very distinct layers: Top soil, colluvium and a ~30 cm thick charcoal and stone rich layer.

 Test Pits in the wider landscape

As well as ground-truthing the results of the geophysical survey, we have also been collecting samples for geoarchaeological analysis from some larger test pits dug by our new friend, The Big Digger. For those unfamiliar, geoarchaeology is an approach to archaeology which utilises techniques from the earth and environmental sciences to answer archaeological questions. In real life it mostly involves getting really, really muddy and pondering sediment sequences for long periods of time…

The main aim was to take samples from the colluvium in the wider landscape (identified during coring by Dr. Richard Tipping and Coring Supervisor Anna) for radiocarbon and pOSL (portable Optically Stimulated Luminescence) dating and micromorphology (the study of in-situ soils and sediments in thin section) to provide us with a proxy for human activity in the immediate area (see Figure 2 below). Colluvium results from human activity, particularly agriculture, and therefore can tell us about past agricultural processes in the wider landscape as it represents a period of soil erosion due to ploughing, over-grazing, and the removal of trees. Under gravity these sediments are then transported downslope. Sometimes, if geoarchaeologists are lucky, ancient soils will be preserved underneath the colluvium allowing us to infer a period of stability and identify the environmental conditions before the land was cleared. The nature of the colluviation also gives information about what processes caused it to erode, and how high the energy of its erosion was.

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Figure 2. Students Oda and Daniel taking OSL samples in the extended section of T6 with Anna and Becky, and Director Paul also working hard in the background. Samples for pOSL were taken vertically down the sequence from the section by inserting tubes into the face of the section, removing gently and quickly securing with tape to ensure no light entered the samples. They were then labelled with a sample number and an arrow indicating the end that had not been exposed to light, ready for laboratory analysis.

Figure 2. Students Oda and Daniel taking OSL samples in the extended section of T6 with Anna and Becky, and Director Paul also working hard in the background. Samples for pOSL were taken vertically down the sequence from the section by inserting tubes into the face of the section, removing gently and quickly securing with tape to ensure no light entered the samples. They were then labelled with a sample number and an arrow indicating the end that had not been exposed to light, ready for laboratory analysis.

pOSL will hopefully allow us to identify the rates of erosion in the area, with the radiocarbon dates from the peat below effectively acting as an ‘anchor’ to identify when this erosion (and therefore agricultural clearance) began. Once the thin sections are made, micromorphology will allow us to identify the depositional and post-depositional processes occurring at the microscale.

Geomorphological Survey at the Bradford Kaims

 Anna Finneran, Coring Supervisor and PhD Candidate, University of Durham

In 2017 the Kaims coring team has benefitted from many dry days, and persevered through some soaking days. Here’s a quick update on the accomplishments of Dr. Richard Tipping and field school students this season:

The Bradford Kaims branch of the BRP since 2010 has conducted a landscape-scale interdisciplinary investigation of a large fenland associated with our archaeological sites.  Excavations have uncovered multiple burnt mounds, structural remains, and artefacts.  Human activity spans at least the Mesolithic through the Bronze Age.  The features and material culture represent an industrial area.  Conspicuous in its absence, however, is evidence for domestic activity in the landscape. In contrast, palaeoenvironmental reconstructions present a rich aquatic environment, characterised by two large lakes throughout the Holocene and populated with unique flora and fauna, potentially attractive for long-term habitation.  The landscape surveys this season have sought to look beyond the Neolithic and Bronze Age by incorporating geomorphology, geophysics, soil micromorphology, and excavation to describe both the natural landscape and the human activity throughout the Holocene.

The main aim of the 2017 season in terms of this geomorphological mapping was coring and sediment description at locations known to contain or likely to contain layers of colluvial accumulation (or slopewash). Colluvial accumulation would result from episodes of erosion on slopes descending towards the fenland basin. Geomorphological analyses from previous seasons concluded that no natural sediment erosion occurred on steep slopes around the fenland. Any erosion on gentler slopes may then be ascribed to archaeological, and potentially agricultural, activity.

The coring team conducted coring transects across the landscape, inserting a metal tube (or sediment core) into the soils and sediments of the fenland and its surrounds, to chart the different types and depths of material.  We successfully identified layers of colluvium within layers of peat, representing episodes of agricultural destabilisation of the slopes, at numerous points. Following reconnaissance, five locations were selected for a combination of analyses including soil micromorphology and pOSL analysis (see Becky Scott’s blog in a few days for more detail on this!).

Another aim of the geomorphological investigations in 2017 was working in tandem with Graeme Attwood’s magnetometry survey to define buried anomalies. Coring and sediment description preceded excavation of 1 x 1m test pits over the most promising anomalies. The anomalies to the NW of Trench 6 proved to be burnt mounds, as hoped. However, the anomalies in the form of two parallel lines between Trenches 11 and 9 were found to be ditches for Victorian age drainage pipes.

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Despite our pipe-related set-backs, one lost (but later retrieved) core, and numerous small injuries and sprains, the coring team successfully completed our aims for this season with positive and encouraging results for the future. Next season we hope to continue to investigate the natural landscape and the human impact upon the environment throughout the Holocene, and hopefully use the analyses of colluvial deposits and the dating material provided by the fenland to gain a more in-depth understanding of how people across the Bronze Age and Iron Age influenced their landscape.

Archaeomagnetic Studies at the Bradford Kaims

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Sam Harris, Doctoral Research Student – University of Bradford

Firstly, it is purely coincidental that I study in Bradford (West Yorkshire) and am coming to take samples at the Bradford Kaims. As an archaeomagnetist, and we are pretty few and far between, it is always amazing the variety of sites that you get to see and work on. Having parachuted into the Bradford Kaims trenches for the second time, this site is no exception in its wonder. Placed at the edge of a fen, the variety of soil and sediment types on site is impressive! This offers the perfect opportunity for archaeomagnetic studies.

For those that aren’t quite sure what this odd science (magic) is, you are welcome to peruse my website, which is listed at the end of this blog post, for some answers. Simply put, the Earth has a magnetic field which varies over space and time. A record of the past geomagnetic field can be found in the in situ remains of hearths, furnaces, or other anthropogenically fired features that we as archaeologist excavate on a regular basis. Archaeomagnetic studies seek to improve our knowledge of past geomagnetic field changes through the analysis of this material. Why though, I hear you ask…

This is because we can use the knowledge of geomagnetic fluctuations over time to conduct archaeomagnetic dating and gain an idea of the last time that some fired archaeological features were heated. Having a dating method which directly relates to an anthropogenic activity, rather than to the end of an organism’s carbon absorption for example, is a powerful tool for the archaeologist.

Archaeomagnetic dating was first attempted at the Bradford Kaims in 2011. While the study was successful and the date recovered for a fired hearth feature in Trench 6 (c.4350 cal.BC) was considered accurate given other artefactual dating evidence for the site, newly acquired radiocarbon dating evidence suggests that the calibration methods used for the archaeomagnetic dates produced erroneous results. This was due to the use of an experimental and alternative calibration model from outside the UK, as the current UK calibration model does not stretch back into the Bronze Age or before. This previous study, and others since, have identified the need for further work to be undertaken. This is where me and my PhD come in! My main aim is to improve our understanding of geomagnetic field change during prehistoric periods, but particularly the Neolithic.

At the Bradford Kaims this season, I sampled two features associated with the Bronze Age burnt mounds, both of them interpreted as fire pits containing fired stones, burnt sediments, ash, and charcoal. These features will provide good radiocarbon dating records, alongside the archaeomagnetic signatures for the fired subsoils within and below them.

Thanks to the Bamburgh Research Project’s excellent radiocarbon dating programme at the Bradford Kaims, the fired archaeological features that I can archaeomagnetically study will have independent dates associated with them. By building up a number of well-dated features in this way, a new calibration curve for the UK can be created, with the Bradford Kaims being a central case study in this process. Through the combined use of radiocarbon dating and archaeomagnetic dating on prehistoric sites like the Bradford Kaims, we can gain a more nuanced understanding of their chronologies.

Sam’s website can be viewed at; www.neolithicarchaeomagnetism.weebly.com

Sam’s Twitter can be viewed at; @Archaeomagnetic

More Bronze Age Pottery!

In a previous blog post, we shared our exciting pottery find from Trench 6 at the Kaims site: a single rim fragment of cord-impressed pottery with a tentative Bronze Age date.  In our 4th week of the season, a further 21 fragments turned up in the same area!  The find included two more rim pieces, four with cord impressions, and 17 undecorated fragments of various sizes from (we believe) the lower portion of the vessel.

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Pottery fragments lying in situ in Trench 6 before excavation

After giving the collection a gentle wash, we were surprised to see that on the surface of several of the fragments are what appear to be small finger nail impressions running in horizontal lines in the fired clay.  They don’t appear to be intentional decoration, so they could be marks left by the vessel’s Bronze-Age creator during the forming process.  If after further analysis our suspicions are confirmed, this would be very exciting for us, because this find will be a rare glimpse of an individual person’s fingerprint on this landscape.

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Pottery fragments after washing

When the new pottery was compared with the original fragment, we found that the three rim pieces fit together, along with the remaining two decorated pieces.  This gives us a much more reliable idea of the possible size of the vessel, which might have had a rim as wide as 45cm.  Right now we think we might have the remnants of a very large bowl or jar.

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The 5 decorated pieces that fit together

One fragment revealed another feature of this vessel: a thin, raised band of clay running along the middle of the vessel, right at the bottom of the criss-cross, cord-impressed band of decoration near the rim.

Due to the poor quality of the clay and low firing temperatures, the vessel would not have successfully held liquid, but could have been used for food storage.

Geophysical Survey at the Bradford Kaims Uncovers a Possible Prehistoric Settlement

On the 17th and 18th of June, Graeme Attwood*, from Magnitude Surveys came to the Bradford Kaims to conduct a geophysical survey of the landscape surrounding the site. The survey produced some intriguing results which provided exciting information for future excavations of the wider archaeological landscape.

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Graeme Atwood from Magnitude Surveys performing a geophyiscal survey at the Bradford Kaims using a fluxgate gradiometer.

The geophysical survey conducted at the Kaims used a hand-pulled fluxgate gradiometer, a type of magnetometer, which measures magnetism. Magnetic survey is used in archaeology as it can detect magnetic anomalies in the ground, which may indicate the presence of subsurface archaeological features. The magnetic geophysical survey investigated a total area of approximately 2.3 hectares in order to assess the below ground archaeological potential of the Bradford Kaims, conducted as part of our wider investigation of the landscape. Our investigations integrate excavation, field walking, survey and paleoenvironmental coring to evaluate the extent and nature of human exploitation of this wetland environment.

The magnetometer survey was conducted in five areas across the landscape of the Bradford Kaims, both in the wetland areas that are the focus of our current excavations and of the hills surrounding them. The survey produced a number of magnetic anomalies, suggesting that a wide variety of archaeological features are sitting below the surface.

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Map showing the five areas in which geophysical survey was conducted at the Bradford Kaims

The fifth area investigated in the survey covered our excavations on the South-Side of the wetland. The results indicated an archaeological feature which is thought to be another large burnt mound, one of the features found across this site. We are confident of this interpretation as a small portion of the mound has been excavated in previously seasons. Part of our remit is to test the accuracy and scope of the geophysics by excavating the anomalies. This is working extremely well, giving huge scope for future work.

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Results from the fifth area of survey showing magnetic anomaly 5a which has been interpreted as a burnt mound

The most exciting results, however come from the investigations of the wider landscape. The third area of magnetometry survey on Hoppenwood Bank near our area of excavation revealed positive magnetic anomalies with a strong archaeological character. Two large circular features; one measuring 13m in diameter, the other 14.5m in diameter, were identified. These circular features are similar to the magnetic anomalies produced by round houses. This suggests we may have identified a prehistoric, possibly Iron-Age settlement, at the Kaims! Within the large outer ring of what we think may be round houses, a series of smaller sub-circular anomalies were also identified. These features are between 0.75m and 2m in diameter, possibly produced by pits and post-holes which may indicate an internal structure to the large circular features which strengthens are interpretation that these may be roundhouses. The evidence that we may have discovered a settlement becomes more convincing when we consider the series of positive anomalies that have been found across the south-eastern portion of the third area. These anomalies are thought to be produced by the presence of pits and similar cut features, suggesting human activity in this area, strengthening the argument for the presence of a settlement. Settlement activity of this type is very rare in Northumberland and very exciting.

Results from the third area of survey showing the circular magnetic anomalies; 3a and 3b that have been interpreted as possible Iron-Age round houses.

This enthralling discovery has put all of the Kaims team in high spirits and we are planning to excavate the area of the settlement, next season. The geophysical anomalies identified in this survey have opened up the possibility of an exciting future for excavation of the Bradford Kaims!

*Afterword from Paul Gething: Graeme Attwood was a regular at the BRP for almost a decade. He came as a young student, became a staff member and eventually went on to run T1 in the Castle. He left the BRP to do postgrad work in Geophysics. He has returned often to visit and occasionally to do small scale work in Bamburgh and at the Kaims. He recently started his own geophysics company in Bradford, which is thriving. He went far above and beyond what we reasonably expected of him on a furiously hot few days. I have always admired his work ethic, but he surprised me with just how much he can do. It was a great pleasure to welcome Graeme back to the BRP and fantastic to work with him again and I look forward to working with him again in the future. I also look forward to seeing his business go from strength to strength.

Amazing pottery from the Bradford Kaims

Last week we had a JCB at the Bradford Kaims to extend Trench 6. When cleaning this new extension, Project Officer Tom Gardner found one of the most exciting finds this site has ever seen: a large fragment of Bronze Age pottery. After giving it a wash, we discovered that the pottery was decorated with cord impressions making a criss-cross shape on its outer surface. The sherd is part of the pot’s rim, and thumb imprints can be seen where its creator was shaping it.

Although twisted cord impressions are common in Neolithic pottery, this sherd was found in a context that is likely contemporaneous with Bronze Age radiocarbon dates. Neolithic pottery is also extremely rare in the North East of England which led us to conclude that it was in fact Bronze Age.

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Project Manager Rachel Brewer is currently doing an archaeological pottery drawing from the sherd to gauge how large the pot could have been, then it will be sent to our finds department for further analysis!

Watch this space.

The Bamburgh Bird: Unique 8th century Anglo-Saxon decorative metal work discovered at Bamburgh Castle

Near the end of last summer’s excavation season we made a marvellous new find of national significance; a beautifully decorated copper alloy bird mount. The decorated fragment is small, 23mm by 12mm, but decorated with an intricate zoomorphic representation of a bird, characteristic of early medieval North European art. The star find has since been undergoing careful conservation to reveal an intricately decorated artefact that is a window into the art of a lost era of early medieval royal society.

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Our first view of the conseved find (Karen Barker, Conservator)

Initial comments from a number of experts has suggested that the bird mount is unique, with no direct parallels and likely to be 8th century in date. It is fascinating that the new image appears to hark back in time to the bird of prey motifs of the 6th and 7th centuries AD and could represent a descendant of these earlier styles just as ‘the later 8th century York helmet, is an update of the form known from the earlier Sutton Hoo, Staffordshire and Wollaston helmets’.

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The bird is a realtively thin copper allow piece undecorated on the back anmd likely to have been mounted onto a larger artefact.

The find, excavated by Harry Francis, was recovered from a cobbled surface revealed at the base of a narrow trench that was excavated to identify the next occupation surface at the southern part of Trench 3.  This was revealed as a well constructed surface just centimetres below the well dated 9th century metal working building. At this time there were a number of smaller kingdoms and Northumbria was one of these. The palace fortress of Bamburgh was one of the most important places in Northumbria at that time and we have evidence of metal working, probably associated with the production of arms and armour for the warriors of the royal court in our excavation. In summer 2017 we will continue our investigations of the find spot and we hope to discover if it represents an earlier period of metal working or some other activity. At the moment our investigation of this horizon is at such an early stage we are unsure if the find came from within a building or from a yard surface or path where it may have been dropped. We are very much looking forward to getting back on site and continuing our excavations.

Francis Armstrong and his son Will, owners of Bamburgh Castle have commented that ‘the Bird is a spectacular discovery. It is a beautiful artefact and we are proud that it has been found here at Bamburgh. Finds like this help us to connect with the Castle’s history and it is wonderful when we get the opportunity to display these ancient wonders so our visitors can enjoy them close up. We are grateful for the work the BRP do here at the Castle and we have a great time working with them unearthing the stories that Bamburgh Castle has to tell’.

Research into the new find is ongoing and we aim to have a short publication ready later this year. The bird will be on display at the castle, open 10.00am to 5pm until 29th October, with many other fascinating finds including pattern welded swords and intricately decorated gold work. You can also come and chat to the archaeologists on site when visiting the castle between June 11th and July 15th.

Pottery Making at the Bradford Kaims – Videos

This blog presents the video interviews from our open archaeology day which focused on prehistoric pottery.

The first shows Rachel Brewer, Assistant Supervisor, discussing the process she went through – first to prepare the clay and then to produce fired ceramics. The second presents some thoughts about the day from two of our students, Ewan and Ian.

 

Thank you for watching!

Stay tuned for more of our experimental sessions – coming soon!

Week 3 in the Post-Excavation Department

 

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The Windmill – home to the Post-excavation Department.

 

Good morning from the Post-excavation Department! We have had a busy few weeks with a steady flow of students coming through eager to learn. Taking into account the better weather and the remarkable finds from the trenches, there is plenty to keep us busy!

 

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Thomas Fox, Environmental Assistant Supervisor, teaching students Katie and Weston.

 

With the amount of new finds, we are able to guide students through the initial processing stages: identifying, recording, and bagging the find. Archaeology at its core is about understanding the past from physical remains, so it is highly important to encourage diligent record keeping.

 

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Students Eden and Steffi finds washing.

 

With the new finds processed, the students are then given the opportunity to move to the next tasks: cleaning, sorting, and illustrating the finds. This allows them the chance to walk through the entire post-excavation process and therefore improve their critical thinking skills and encourage thought on the historic use of the artefact.

 

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Finds Supervisor, Jeff Aldrich, examining some of the finds from the Bradford Kaims.

 

Bradford Kaims has been updating their records to reflect the past several years of work. The finds have all been processed, it’s simply a matter of digitising and correlating the artefacts to their locations in three dimensions. Once the locations are correlated, we can store the finds for future study.

With three weeks down and new students ready to learn about archaeology, we’re getting things moving here at the Project and look forward to the next five weeks!

Trench 6 Update – Bradford Kaims

 

Trench 6 remains our largest and longest running trench to date at the Bradford Kaims. Each new context we uncover adds to the complexity and variety of information about prehistoric human activity in the area. Here, we highlight just two of the exciting features currently under excavation.

 

THE TROUGH

Over the past couple of weeks, we have uncovered our wooden trough in the northwest corner of the trench. After two years of sitting under tarp, the trough has now been fully excavated and cleaned, with its contents removed down to a beautiful clay base. The trough is made of a hollowed out oak tree and fills with crystal clear water, so may have been used as a well; however, within its fill, fire cracked stones have been found which means that this water was probably being heated.

 

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The trough being fully excavated after half-sectioning.

 

BUILDING A

Earlier in the season we uncovered a suspiciously rectangular-shaped dark fill in the northern side of Trench 6. Upon beginning excavation last week we found a series of four large postholes down one side as well as postholes in each corner. We believe that the colossal postholes suggest that this structure was a building. Lying within the structure is an oblong patch of burnt material, which could possibly be a fire pit. From this pit, we have removed a large pointed post, which could have been one of the posts supporting the structure.