Environmental Archaeology Crash Course: Flotation

Environmental Supervisor and archaeobotanist Alice Wolff gives us some insight into her work on site:

Today’s blog is going to be a more in-depth look at the environmental archaeology activities here at Bamburgh. Last weekend, we had three open-day sessions where members of the public helped us process some samples through flotation. In this blog, I’m going to break down what exactly we did and what it helps us learn about the site!

A wooden tank labeled “HMS Floaty McFloatface."

What is flotation?

Flotation is a method of processing bulk soil samples using water. Essentially, the different materials in the sample (such as the soil, the rocks/bones/artefacts, and the charred material) have different densities. When you put the whole sample in water, the soil and the artefacts sink while the charred material floats. This allows us to extract fragile and hard-to-see objects such as charred seeds or fish bones that are essential to our understanding of diet and environment at the site but are nearly impossible to excavate in the trench.

Flotation at Bamburgh

After recording pertinent information about the sample – i.e. where it came from in the trench, its volume and weight, what the soil looks like – we dump it into a 500µm mesh that lines the flotation tank.

Two students with their hands in the flot tank.

Next, we raise the water level until it covers the sample completely. We then shut off the water and gently massage the dirt with our hands.

Two pairs of hands submerged in muddy water in a flot tank.

Once most of the soil has fallen through the mesh to the bottom of the tank, we turn on the water again and let it flow through the spout, catching any floating material in a 250µm mesh bag.

A stream of muddy water flowing into a white bag held in place with clips.

In order to conserve water, we use two settling tanks and a pump. This allows us to recycle water and avoid flooding the castle at the same time!

Two students at the flot tank in front of two black bins filled with muddy water.

Once flotation is finished, the heavy fraction of the sample (the bones/rocks/artefacts) is dried in trays while the light fraction bag is hung up on a line indoors out of direct sunlight to dry slowly. After drying, both fractions are sieved, sorted, recorded, and stored in our archive for future researchers to look at! The heavy fraction can be picked over by students, but the light fraction requires the use of a microscope to separate out and identify the charred seeds.

The members of the public only spent a few hours in enviro, but our students spend at least one full day per week doing flotation and/or sorting. On particularly sunny days, enviro is a welcome break from the trench! After spending so much time carefully studying the various materials we find in samples, students return to the trench with a better understanding of what they are digging up and why environmental samples are so important for filling in the picture.

 

Festival of Archaeology Update/Youth Takeover III

Our second day of environmental archaeology tutorials as part of the Festival of Archaeology went well, without the intermittent monsoons of yesterday! We will have a step-by-step guide to environmental processing later in the week to explain just what we were doing.

Tomorrow (22 July) is both the Youth Takeover celebration as well as A Day in Archaeology. Click here to read about a day in the life of people in various archaeological roles as well as some behind the scenes info about how digs work!


Below is another Youth Takeover post, where Nathalie (21, left) talks about making archaeology more accessible.

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Accessing Archaeology

As a student in ancient history and history, I had only come across archaeology in lectures and readings, but have had little opportunity to actually study it apart from the most introductory modules. Archaeology provides so much evidence that is vital to our understanding of the past, but can be overlooked when just looking at documentary evidence. I think that it is extremely important to include archaeological study in any study of the past, particularly as it provides a much needed different perspective, often a multidisciplinary view.

I have always been interested in archaeology, visiting sites throughout my childhood, in particular spending hours wandering around the British Museum. Even now I still drag my parents and reluctant sister to numerous obscure sites (some turning out to be rather big adventures) wherever we go. More and more through my degree, I have come to realise that it was archaeology that truly moved me. I have been taking any module I could that was related, which was surprisingly difficult as my university still doesn’t actually have a proper archaeology department. Through the opportunities that field schools have provided, I am starting to build up some experience in the field that I was missing in the classroom. However it worries me that this is something that is not always possible for many financially.

Field schools can sometimes be prohibitively expensive, especially as a student. This could prevent many people of every demographic getting vital experience due to socioeconomic circumstance rather than their ability. This is compounded by the fact that many archaeology jobs are not well paid, making it difficult to even support yourself, let alone pay back the multitude of loans needed to get the degrees in the subject you love so dearly. I myself plan to pursue a masters in archaeology, but I feel so absolutely lucky that I am able to do this, as many don’t have these opportunities.

Archaeology in the future needs to become more open to people from all backgrounds, but we as a field especially need to address socioeconomic diversity. We must do all we can to promote low-cost or free field schools and scholarships (which is difficult to provide because of competition and lack of funding, I know, I know), or even push for restructuring of the wage system both to allow professional archaeologists to pay back loans and also make it a more viable long-term career prospect. If we don’t make this change now for the future of archaeology, it will continue to be a field closed off to many.

Festival of Archaeology: Day 1/Round-up: Week 5

Today is the first day of our free Festival of Archaeology programme at the Castle. Participants get to spend a half-day with Environmental Supervisor Alice Wolff processing soil samples, sorting the residue (artefacts and gravel), and examining the flot (the charred seeds skimmed off the top of the soaking sample). This programme was made possible by the Mick Aston Archaeology Fund through the Council for British Archaeology.

Here are some pictures of the environmental samples being floated!

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Round-up: Week 5

This week we took down the Porch, the area in between the latrine pits, as well as the area south of the porch that abuts the entrance ramp sondage. We were able to mattock the area, which tickled everyone because everyone loves a mattock.

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When we first extended the sondage (mini-trench) near the entrance ramp, there were two large flat stones just a few centimetres down; the one in the centre of the sondage is visible in the top left corner of the photo. This of course was not nearly enough evidence to say anything meaningful…until we had a bit of rain. The rain revealed something peculiar: three areas drying at different rates. The right of the main stone was light brown, the area in front of the stone was light brownish yellow, and the left side of the stones out of frame was dark brown, and all retaining water differently. We call this “differential drying.” Usually when a patch of earth doesn’t dry as quickly as others that means that something is happening under the surface, like stone that has affected the drainage path of the water or clay is acting as a shallow bowl. We thought that we might possibly have a linear feature, but the constant cycle of rain and bright, drying sunshine kept revealing and obscuring it over the past week. We sometimes wondered whether it was a mass hallucination.

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As we worked outside of the sondage near its northwestern corner, suddenly more stones appeared at roughly the same angle of the boundaries of the weird light yellow patch. They formed a little channel that we are carefully chasing as it heads toward the eastern latrine pit. The only artefacts found associated with this linear feature were some fragments of copper.

On the western side of the trench, we reach the edge of excavation from BHT and our re-dig from many years ago and began taking down the midden deposit. Here is the cutest little section ever excavated:

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We finally bottomed out the western latrine pit! We reached our re-excavation horizon, as well as BHT’s initial attempt to fully excavate it. We were so excited to reach unexcavated soil perhaps holding some Iron Age material…but the excitement was not long-lived, as it turns out BHT stopped only 15cm above the bedrock. Oh well!

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Lastly, the weird northwest corner of the trench continues to gift us more mysteries. The Roman glass bangle fragment (hyperlink) came from this area, which had been quartered and each quadrant excavated individually. It’s remained damp through the sunniest days, as usual.

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Calendar of Upcoming Events

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We’ve got so many cool events in conjunction with the Council for British Archaeology’s Festival of Archaeology coming up and wanted to drop you all a breakdown of the next week!

17 July – Ask an Archaeologist Day

Send us all your burning archaeology questions on here, on Facebook, or on Twitter using the hashtag #AskAnArchaeologist. If you’re using Twitter, please make sure your account is unlocked so we can see your questions! Tweet your questions to @BRParchaeology to reach us, but don’t be surprised if you get some answers from other archaeologists…we’re very talkative. This initiative is to get people from all walks of life into the conversation about archaeology! We hope to help connect interested non-experts with archaeology, museum, and heritage professionals in a more accessible way. We love sharing our work (which is our passion), and this is a great way to give people some insight into what we do.

 

20-21 July – Festival of Archaeology FREE Environmental Archaeology Experience at Bamburgh Castle

Our very own archaeobotanist Alice Wolff will be running half-day tutorials both Saturday and Sunday on how we process environmental samples! Come spend a morning or afternoon with us and get a behind the scenes look at some of the great work our team is doing to better tell the story of Bamburgh. These two days of programming are supported by the Mick Aston Archaeology Fund.

Sign up here! It is completely FREE. Sunday still has some slots open, but Saturday is booking quickly, so what are you waiting for?

 

22 July – A Day in Archaeology

Have you spent some time with us on the dig as a student? Volunteered on any dig recently? Share your story in the week leading up to A Day in Archaeology by uploading a blog post or video telling us what your typical day looked like. Check out the posts so far this year, or dive into the archives. We’ll be posting about the most mysterious member of our team…me…the Outreach Officer! So stay tuned to the website above for what a typical day looks like in a public-facing role at a field school!

 

Meet the Team: Environmental

This season we are really refocusing on environmental archaeology to better tell the loooooong story of the site. Archaeobotanist Alice is analysing all the data from our soil samples, so here’s a bit about her background in her own words.

Alice Wolff, Environmental Archaeologist

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Like a lot of the team here, I decided to be an archaeologist when I was six and haven’t changed my mind since! I’ve been digging in England since 2013 and doing environmental archaeology since 2014, but only joined the BRP in 2018. Prior to joining the BRP I received my BA in Medieval Studies from Smith College and my MPhil in Archaeology from the University of Cambridge. When I’m not in the field I am a rising second-year PhD student in Medieval Studies at Cornell University where I study human responses to climate change in the first millennium AD. At the BRP I spend most of my time running the flotation tank and looking at charred plants under a microscope.

YAC Attack Day 2 and The Riddle

Today was part 2 of our weekend of YAC-tivities. For part one, click here.

We had some participants from the York chapter of the Council for British Archaeology’s Young Archaeologists’ Club. Like yesterday, everyone got a chance to work with Alice on environmental processing and analysis. We’ll hear more from Alice about her work here with the BRP and why it’s so important next week. Once again, we’d like to thank the Mick Aston Archaeology Fund for helping us deliver this weekend of programming.

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We also wanted to reveal the answer to The Riddle. Did you miss it? Click that link and have a read and a think. We’ll wait.

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Okay. Are you ready for the solution?

The solution to all three versions of the riddle is a “coat of mail.” What’s so fascinating about these poetic little riddles is that they provide us with so many words associated with the craft of weaving. Linking the tiny loops of metal involves weaving them in and out of each other, rather than weaving weft and warp stretched across a loom. Just like a garment, your mail could be mended, extending its lifetime maybe even from parent to child. The elevation of handicrafts to poem-worthy status is a common feature of Anglo-Saxon riddles, giving us such a lovely but brief glimpse into everyday life.

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This is actually part of a corroded coat of mail from the 7th-century burial at Sutton Hoo.

 

YAC Attack! Day 1/Round-up: Week 3

Today’s YAC attack is by some of the members of the Flodden chapter of the Council for British Archaeology’s Young Archaeologists’ Club! We were so excited to have them on site with us, and they brought a lot of energy and enthusiasm. That’s why archaeological education and community archaeology are so much fun for us here at the BRP. Through the generous support of the Mick Aston Archaeology Fund, we were able to host these future archaeologists and really give them a day in the life of an archaeologist at Bamburgh Castle.

We had our young archaeologists rotate through a few of our daily activities, with special emphasis on the environmental work of Alice Wolff. They learned to process environmental samples through flotation, sorting, and analysis. But we didn’t just help them with the technical stuff, we really wanted to explain WHY we are looking so carefully at the palaeoenvironment. We can learn a lot looking at how past communities subsisted through times of plenty and times of scarcity, and Bamburgh Castle’s long history of occupation makes it a great candidate for exploring long-term cycles of environmental stasis and change. We broke them up into teams, and their team names did not disappoint!

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Team Ducky McPlatypusface running the flotation tank, gently letting the water break down clumps of soil to release any charred seeds that would float to the top.

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Team Artichoke looking at the heavy fraction produced via flotation, as well as some small finds that were in the sample.

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Describing the soil before processing via the flotation tank.

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Analysing some seeds under the microscope.

Both teams spent time with Alice (above), but also got to work with Tom Fox on some finds washing and Tom Howe and Kelly Tapager in the trench.

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Finds washing and intro to zooarch with Tom Fox.


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Excavating The Porch with Tom Howe.


Round-up:

This week had some up-and-down weather, and it was quite windy atop our perch in the West Ward. Regardless, we made some great progress throughout the trench.

The western wall just north of the BHT mortar mixer and the section adjacent to said mortar mixer now are some lovely sections, which our students cleaned and planned. On the way down, we found an interesting flattened aluminum cylinder that launched a day-long research dive you can read about here. Here we are taking an environmental sample:img_20190706_153042

The cobbles in the southeast corner of the trench lay mostly untouched this week, but the sondage near the entrance ramp to the trench was extended and it approaches the cobbles to the south at a fair clip.

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In the northwest corner of the trench, that weird section we always go on about, we’ve decided to divide it into quarters. We excavated the southeast quadrant and then took an environmental sample of the northwest quadrant which included a large patch of charcoal smears and orange clay.

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The environmental department has a new serif tank (link to twitter) we’ve named HMS FloatyMcFloatface. We’re telling everyone that we planned to name it after David Attenborough but took a popular vote and Floaty won as a write-in. Too soon? Too soon.

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In terms of finds, we might have been a little spoiled the past two weeks, so we aren’t too worried that we’ve mostly been finding vast quantities of animal bones. Finds supervisors Tom Fox has been using these animal bones to run sessions on zooarchaeology identification. We sat in on a few between tours and it was a great refresher for the basics, but also completely changed the way the rest of us non-zooarch-experts look at the animal bones that comprise the majority of our bulk finds.

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We also have two metal…somethings. The copper alloy object may be a strap-end that’s now clogged with soil. The lead object looks like a thin, rectangular piece of lead was rolled up to create a cylinder, or possibly rolled upon itself to give a spiral cross-section.

The Festival of Archaeology is just under a month away!

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This is your big, bold reminder to come join us at Bamburgh Castle on 20th or 21st July.

Our free trench-side activities will focus on environmental archaeology, under the guidance of environmental supervisor Alice Wolff. Participants can join one of our half-day sessions for hands-on experience in recording, sorting, and analysing soil samples. Sign up here!

Three dark-haired women stand around a square tank of muddy water.

Environmental Supervisor Alice works alongside two students on a brisk day.

Now you might be thinking, “What are soil samples, and what could they possibly tell us?” Environmental sampling is a process by which archaeologists can collect and study the fills or even floor surfaces of archaeological features; these fills include the soil that is inside rubbish pits, postholes, and even buildings. The samples are carefully collected and then processed with a sieve and running water known as a flotation tank. The sample is suspended by a small mesh and water is pumped from beneath it. The water separates the silt from the small rock fragments, allowing the tiny grains of silt to sink through the mesh. The small rocks and any artifacts will rest in the mesh, while charred seeds and sometimes even the shells of small molluscs (like tiny snails) will float to the top and can be skimmed off into another fine mesh. You end up with three resulting products: pure silt, rocks and artifacts, and the skimmed material known as “flot.” This flot can be analysed under a microscope to identify the seeds and molluscs. Seeds tell us all about the domesticated and wild plants consumed by a community on a site, while small molluscs can actually tell us about the climate because certain species only survive in very particular temperature ranges. The rocks and artifacts will be dried and sorted to get a clearer picture of what the area sampled was used for. And the silt? Mostly clogs up our water jets, to be honest. It’s a good bit of fun, but when you join us, be sure to wear something that you won’t mind getting a little muddy, as well as sturdy footwear!

The Festival of Archaeology is a celebration of archaeology where everyone is welcome to listen, learn, and get their hands dirty! It is a Council for British Archaeology initiative, and this year the focus is on the intersection of archaeology and scientific technology. We’re able to run our event during the festival this year due to a grant from the Mick Aston Archaeology Fund. We hope to see you there!

Join the Bamburgh Research Project as part of the Festival of Archaeology

The Bamburgh Research Project (BRP) will hosting a weekend of free activities as part of the Council for British Archaeology’s annual Festival of Archaeology.

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Join the BRP on the 20th or 21st of July to explore 2000 years of activity at Bamburgh Castle on their annual excavation within the West Ward of Bamburgh Castle, Northumberland.

The BRP have been excavating through 2,000 years of occupation at Bamburgh Castle. As we excavate, we undertake environmental sampling of the different archaeological layers. These are processed on the trench-side where bones, seeds, charred remains and small artefacts (including coins, gold-filigree decoration and beads) are recovered.

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As part of the Festival of Archaeology the BRP are hosting four half-day sessions where members of the public can work with our Environmental Supervisor to process our samples and record the material we recover. This will include specialist training with a flotation tank, tuition in recording the processed material and identification of archaeobotanic material in our on-site lab funded by the Mick Aston Archaeology Fund.

To book your place simply visit the Festival website and follow the instructions: sign-up to the BRP Festival event

 

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.