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.

Our Lecture Series for the 2017 Season

Anyone in or visiting the Bamburgh/Belford area during the next five weeks are welcome to attend our  Wednesday evening public archaeology lectures at the Bell View Centre in Belford, Northumberland.

BRPLecture Poster 2017

No booking is required and entry is free, though any donations to the project to cover the cost of renting the venue is gratefully received.

The Bradford Kaims awarded Moray Endowment Fund grant

We are pleased to announce that Tom has been awarded a small grant from the Moray Endowment Fund of £1992 for comparative research into the geoarchaeology of burnt mounds and associated soils, most of which will be undertaken at the Bradford Kaims, with a smaller study being conducted on Allt Thuirnaig burnt mound at Inverewe, in the north-west of Scotland.

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Tom taking micromorphological samples through peat deposits at the Bradford Kaims

The Moray Endowment Fund is an internal funding body of the University of Edinburgh, where Tom is currently undertaking his PhD studying the wider geoarchaeology of burnt mound deposits across Great Britain and Ireland, for which the Bradford Kaims forms a core case study. This funding will allow us to look in great detail at a larger suite of micromorphological samples from the burnt mounds at the Bradford Kaims, and from the fills of some relict streambeds associated directly with the burnt mound use. Thin section micromorphology, a technique in which Tom is becoming well versed, involves the microscopic analyses on in situ sediments and soils, and seeks to better understand what archaeological sediments consist of, where they came from, how they got to where they are now, and the processes that have changed them since they were deposited.

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Thin section micrograph of micromorphological samples through the burnt mound in Trench 6 at the Bradford Kaims

Through this form of study we already know that some of the earlier burnt mounds at the Bradford Kaims were deposited seasonally probably in summer and autumn, and vary widely in their fuel types from small Roundwood charcoal through to grasses and sedges. From this, and with our wider landscape analyses, we are able to better understand the movements and activities of people living around the Bradford Kaims in the Neolithic and Bronze Age, and how they interacted with their environment.

We thank the Moray Endowment Fund for their support, and all of our readers for their continued attention!

 

Bradford Kaims 2015 Interim Report Released

Since the end of the 2016 season we have been working hard to process and assess the material which we extracted from the Bradford Kaims, as well as dispersing to work on our other projects. However, we had a wee bit of catching up to do on the 2015 season, in the form of finalising our interim report. We usually try to get the interim reports done prior to the beginning of the next season, as we managed with our 2013 and 2014 season reports, but time ran away with us this year. However, we can now safely say that the 2015 interim report from the Bradford Kaims is available, open access and on our website!

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Trench 6 under investigation in 2015

I shows the highlights and the less glamorous sides of our 2015 scheme of investigation, and covers all the excavation which took place during out two month season, so please give it a look and let us know what you think!

Evidently it is a slightly slimmed down version of our activities, the full details of which will be presented in our end-of evaluation site monograph. However, it should provide details of our exciting finds, such as the Neolithic timber platform in Trench 6, the timber laid working area in Trench 11, and the stake-built building in Trench 9!

Now, a bit of time off to work on other projects, such as the exciting Blythe Beach work, and then the beginning of the 2016 interim report!

Tom Gardner

Looking back at this seasons work in Trench 1

When we set out at the start of the season we were fairly confident that this would be the last year of excavation in Trench 1. There seemed only a limited number of questions left to be answered and since we had exposed boulder clay and bedrock over the full area of the trench at the end of last season, it’s not as if there was much more to dig. Trench 1 always seems to have more secrets to reveal though, so the appearance of more post-holes and small features, due to slow weathering, and the difficulty of answering one of our last research goals, frustrated us in the end. I can’t say I am sad to have a little more to do next year.

We started the year with two outstanding research goals. The first was to complete the investigation of the corn-drying kiln (a kiln or oven used to dry damp cereal for use or storage) in the north-west corner of the trench and the second was to further investigate the timber defensive rampart leading to St Oswald’s gate and also to see if we could also trace evidence of the rampart along the northern limit of the perimeter of the site. It presence here had long been speculated on but never proved.

The kiln has been a fascinating feature, constructed from fired clay set around laths of timber that would have at one point supported a domed top, fragments of which we find broken and forming a substantial part of the fill of the bowl. It also contained a considerable quantity of charred cereal grain that will help us learn a little more about the diet of the inhabitants. The kiln was likely used to dry damp grain on its way into the fortress for long term storage. This would explain its location close to the entrance at St Oswald’s Gate. At the moment we have a series of potential dates for the kiln based on archaeomagnetic samples. The most likely period of its use is the late Anglo-Saxon period, but a radiocarbon date will be needed to confirm this.

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The kiln at the start of the season (left) and following complete excavation (right)

One aspect that has intrigued us about the kiln for a while is that it underlies the earliest phase of high medieval wall, which is probably 12th century in date. The edge of the rock plateau is close by so when the kiln was in use there must either have been a much thinner stone wall or no defensive feature at all, given that a timber rampart would have been at a severe risk of burning down if right next to a kiln. We know that we have at least two phases of timber defence on the west side and that the kiln cuts and post-dates the latest of these. This summer we have further investigated this, excavating more of the later rubble foundation for a timber sill beam to reveal a series of post-holes beneath it. On the same alignment. The post-holes are spaced about 0.5m apart and, like the sill beam, almost certainly represent the inner face of a box rampart.

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The norther part of the stone rubble rampart foundation excavated to reveal two earlier post-holes that formed an earlier phase of the feature

We have long speculated that the rampart likely continued around the fortress perimeter on the north side and have even seen what appeared to be a linear formed from a stony clay extending in the right place and on the right alignment for this. We began the excavation of a slop through the boulder clay across the trench to try and investigate this idea. We assumed that if the spread was to represent the former fill of a timber rampart then we would have re-deposited boulder clay on a boulder clay surface that had not been disturbed. The theory seemed reasonable but proving it has turned out to be much harder than thought. The boulder clay turns out to be more variable and mixed than we thought from its surface and, not at all surprisingly, hard to dig! By the end of the season we had a number of potential post-holes, a series of enigmatic patches of apparently burnt clay and no clear buried surface. Unable to make firm conclusion just what this evidence means, we will be conducting a limited amount of further excavation next year. Hopefully we will be able to get some secure answers, but if not then at least we will have done everything we could to reveal this last secret.

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Trench 1 looking west with our sondage into the boulder clay marked by the ranging rod. Lots of confusion at the north end but no certainlty about just what we are excavating yet!

 

An Excerpt from the Promontory – Bradford Kaims

Trench 12, 13 & 42 were opened (reopened, in T42’s case) this season for sampling & investigations into the burnt mounds located on the promontory.

T12 is a 2m x 3m trench located on the southern end of the promontory. Shortly after opening the trench, we began to find some really interesting artefacts. In the peat layer, we found a piece of burnt quartz & when we continued down through the peat onto the burnt mound layer, we found more: two pieces of worked flint & two pieces of burnt bone! Quite exciting finds for a trench originally opened up for sampling.

 

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A piece of worked flint from trench 12.

 

Trench 13 is 1m x 2m trench located just off the edge of the promontory, near the waters edge. Like T12, it was opened for sampling & has also produced some really interesting finds! Just below our peat layer, we discovered a layer which consists of shells & sand moulded & formed together. In that layer, we uncovered two pieces of charcoal, nine small (4-10cm sized) pieces of worked wood & one log roughly 1m long. We think the smaller wooden pieces may have been stakes & considering their proximity to the waters edge & the fact that a couple were orientated at a 45° angle, it could indicate fencing.

 

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A piece of worked wood from trench 13.

 

A 2m x 4m portion of trench 42 was reopened for sampling, with the focus being on the burnt mound, the trough & the limestone piece. A 1m x 2m spit was dug out of the north end. We expected the burnt mound material to continue at least a half meter, but we quickly uncovered an interesting mottled orange clay layer only 4-5cm into the burnt mound layer.

 

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The re-opening of trench 42.

 

Since the weather has turned more amiable for excavations to continue in our other trenches, we have taken a break from our work on the promontory, but plan on returning to it to as soon as feasible.

Introduction to Environmental Processing

In this video Thomas Fox, Environmental Assistant Supervisor, discusses the process of environmental sampling and what we can learn from it.

 

Stay tuned for further videos and updates here and on our YouTube Channel as the season progresses!

Another week in the Finds Department

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The Windmill during a brief respite from the rain.

Good morning from the post-excavation department! We have had a busy few weeks processing some intriguing finds including a possible iron stylus, a worked stone bead, several bits of unidentified burnt clay discs, and a potential lead pendant, to name a few.

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Finds Illustration

Environmental supervisor Thomas Fox has kept our students engaged at the flot tank processing environmental samples from last year while Post-ex supervisor Jeff Aldrich has been taking advantage of the poor weather to give students the a chance to illustrate and process our finds.

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Students Katie and Kelly sorting environmental flotation samples.

The students have also had the opportunity to learn a bit of post-excavation from Bradford Kaims processing finds, including a plethora of worked wooden stakes and the resultant paperwork led by trench supervisor Becky Brummet. Because of its distance from civilisation, it is a separate process at each site: the Castle and the Kaims.

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Students Joe and Rachel filling out timber recording sheets.

With the sun shining and the winds calmer, the students and staff will have ample time in the trenches to find us some new artefacts, hopefully further fleshing out the story of Bamburgh Castle.

Gearing up for BRP 2015: Bradford Kaims North

Today we introduce you to the awesome staff of Bradford Kaims North! Returning Project Officer Tom Gardner will be assisted by Alex Wood, Sophie Black, and Franzi Le. We are looking forward to another awesome season of progress at the Kaims!


Tom Gardner

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“I’m originally from Glasgow, but have been living in Edinburgh for the last five years studying for my undergrad in archaeology, now my MSc by research, and from September, my PhD in the environmental archaeology and geoarchaeology of burnt mounds!

When I am not at the Kaims, I spend a lot of my time processing samples from the Kaims, writing about the Kaims, talking about the Kaims, or thinking about the Kaims. Occasionally I sleep, and that time is really for me. I am joking (hopefully); I mountaineer, canoe and kayak, drink ale, sit in coffee shops, read books, canvas for political movements, and despair over the state of the country.

I first attended the BRP in 2012 as a student, in 2013 as an Assistant Supervisor at the Bradford Kaims, before assuming my current role as Project Officer for the north side of the Kaims in 2014. This season I have an extensive programme of work planned for Trench 6 at the Kaims, and a series of smaller excavations in the surrounding area! These focus upon our platform features, doing a bit of sampling for my PhD, and having a laugh with the team again; postgraduate life can be lonely!

Looking forward to you all joining us!”


Alex Wood

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“I am one of the Assistant Supervisors for the Bradford Kaims this season. I went to the University of Edinburgh to study Archaeology MA (Hons) and graduated this time last year. My primary archaeological interests lie in Mesolithic Britain and experimental archaeology. This will be my first season with the Bamburgh Research Project, although I have visited the Braford Kaims excavation in the past and the site was the inspiration for my undergraduate dissertation on the preservation of archaeological wood. Since graduating I have been training to be a teacher but archaeology has pulled me back into its warm (and muddy) embrace! I have recently taken up wood carving, so when not excavating I will probably be found in a corner whittling a spoon, slowly burying myself in a pile of wood shavings…

I am thoroughly looking forward to joining the Braford Kaims’ excellent team and seeing what organic finds will be uncovered this season!”


 Sophia Black

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“I am from Bulgaria and I moved to Scotland in 2011 to study Classical Archaeology in the University of Aberdeen. I first worked with the project as a student in 2014 and absolutely loved the Bradford Kaims! I am very excited to come back this year and continue working on the site. When I’m not at the Kaims or at Bamburgh, I divide my time between uni, work and Criminal Minds. I am very much looking forward to coming back, working with all the great people I met last year, and also meeting new faces!”

Franzi Le
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“I am from Germany and very lucky to have learned about this project on-line in 2013! The first year I attended as a student. In 2014 I returned as staff but unfortunately only for the last two weeks because of my university’s termtime. I am doing a BA in Archaeology and Cultural Heritage Conservation in Bamberg. This year I am especially looking forward to the season since I found a way to spend at least four weeks with this amazing project. I am excited to get more involved and to find new interesting evidence at the Kaims!”


This year’s digging season will start on Monday the 8th of June, so stay tuned for more blog entries, tweets and video footage of the intriguing finds at Bamburgh Castle and the Bradford Kaims! We can’t wait to get started!

Archaeological Science at Bradford Kaims – Phytoliths: Part Two

The Results.

The full results of the phytolith work will be published over the next few years, and are already informing our excavation strategies for the coming season (if you want to know more details, you can email Tom). However, we can give some of the highlights here.

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Phytolith concentration per spit in each deposit – results in concentration per gram AIF.

The phytolith record from Mound 1 in trench 6 at the Kaims were relatively well preserved for British samples (very little phytoliths have ever been processed from British soils, and we are the first to use these records successfully at burnt mound sites). The most striking results of our analysis is the high level of morphological and concentrational variation from different areas of the mound, horizontally across various sub-mounds, and vertically throughout these deposits. The concentrations indicate that each of the sub-mounds are deposited as distinct entities, with a consistent intensity of deposition. This implies that there is a tangible depositional sequence which starts in the south of the mound and circles round the hearth to end with the latest deposits at the north. However, the phytolith morphologies vary hugely within these distinct sub-mounds, indicating that the individual events which comprise these depositional episodes vary in character, but not intensity.

The Interpretation.

Further than these general points on depositional sequences, which actually go quite some way to furthering our understandings of how these mounds came into being and the morphologies they represent themselves in, the phytolith information can help us make some interpretations of fuel use, resource use, and burnt mound function.

The phytolith morphologies present suggest that the majority of the fuel burnt was dicotyledonous plants, and the predominance of ‘platey’ phytoliths indicates that the fuel was wood. However, in most areas, this record is accompanied by a significant level of monocotyledonous phytoliths, which represent grass phytoliths being caught up in the bark of trees prior to their firing. This suggests that the wood was not de-barked before burning. However, in some few areas the dicot level is astronomical, suggesting that the trees may have been debarked prior to firing.

The presence of varying levels of sponge spicules and siliceous diatoms within the phytolith record indicate the presence of freshwater impregnation of the deposits. However, as these two indicators are never concurrent, this points away from recurrent flooding and towards anthropogenic factors introducing water into the deposits. We know that burnt mounds are always associated with water sources, as their primary function seems to focus upon the production of hot water using heated stones. One of our current hypotheses to explain the fluctuating levels of sponge and algae within the phytolith record is that these may be being introduced through this avenue, where stones are placed in a trough of water, and then later deposited in the mound with adhering sponge and algae phytoliths.

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Sponge Spicule from mound 6080.

These are all still tentative hypotheses and will be formalised with the forthcoming thin section results before publication. However, these new avenues of research indicate the importance of testing old hypotheses with new scientific techniques, and have gone quite some way to informing our investigations about resource use, function, variation, and depositional sequences within the burnt mounds in trench 6 at the Kaims.

The Future.

This research is ongoing, and as such still has some distance to go before they have been fully rationalised. The next step in the process is to assess the thin section results which were taken in tandem with the phytolith samples, and then to compare the records together. But already this speedy off-season sample processing and post-ex has given us a new series of excavation strategies for our upcoming 2015 season (which you can still sign up for!). For the first time, we know that the term ‘burnt mound’ is inherently flawed! The phytolith record has shown that in fact these deposits comprise a series of individual sub-mounds as discrete entities, which in turn show enough variation in their morphologies to point towards individual events of varying character. A ‘burnt mound’, is actually a series of ‘burnt mounds’, likely deposited in episodic sequence, but with varying functions contributing to their deposition. We, at the BRP, are one step closer to cracking this enigmatic site type!

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The various sub-mounds comprising Mound 1 at the Bradford Kaims.