Sunday, 11 August 2013

Investigations at the Ness of Brodgar Days 4 and 5

Ben Chan discusses this week's progress on the site tour
This week has gone by so quickly, but we have managed to collect some great sets of samples, more than we can get made into slides at the moment! The first lot have already been sent off to Earthslides to get made into thin sections. An important lesson from the field - if you get over enthusiastic about collecting blocks of soil that weigh >1kg each, they will not fit in your luggage and will incur hefty postage fees. And lesson 2, blocks of soil wrapped in tissue and tape look very odd on the airport X ray and your bags will likely be searched. I ended up taking about 20 block samples in all, and spent much of my last day in Orkney panicking about how to transport them back.

 Friday was my last day on site, and the day started with a site tour with each supervisor summarising what has been going on in the building/trench that week. A week is just not long enough to get my head around everything going on at the Ness; I think I've just about come to grips with the major buildings and how my midden samples fit in. Luckily I have been working with a great team of archaeologists who have been incredibly helpful with explaining the current thinking for what is going on, and advising on the best areas to sample. Dan Lee and Dave Reay from ORCA deserve a special mention for putting up with my questions and putting multiple holes in their nice sections.
Midden after micromorphology sampling

I hope to return to Orkney at some point when the analysis of the slides is underway so we can discuss how the results fit in with the macrostratigraphy, and get further information on the different contexts. It's easy to get bogged down in the microscopic details with micromorphology, but it is important to remember that we are just looking at a snapshot from the bigger picture. I like to think of it as a two way team process, where fieldwork provides hypotheses that inform the micromorphology sampling strategy, and micromorphology provides information which clarifies what's going on in different contexts, especially helping to resolve finely stratified deposits that are impossible to excavate as true single contexts. The best bit will be seeing all the results come together, then we can get on with the difficult bit - interpretation! What will these midden deposits tell us about the Neolithic people at the Ness?

Friday, 9 August 2013

Investigations at the Ness of Brodgar Days 2 and 3


Planning sampling strategy with Jo

After planning the sampling strategy, the next few days have been spent collecting samples. I decided to focus on two areas of nicely stratified midden for the main sampling, and have collected overlapping sample blocks to provide an overview of the entire sequence. Already it's possible to see some quite ashy areas, so hopefully we will be able to get some nice information on resource use, and hopefully what activities the fuels relate to. We decided on a further 4 areas as secondary sample sets with a smaller number of samples, testing specific hypotheses from the excavations. More on those later this week.

As well as the Orkney students, we also have a team here from Willamette University, Oregon, led by Professor Scott Pike. Professor Pike has a background in geology and expertise in pXRF (portable X-ray fluorescence). In brief this involves using a piece of kit that looks like a ray gun to fire X rays at material, which then reflects the energy back. Different elements reflect the energy in different ways, and can be identified on this basis. His team have been conducting analysis of floor deposits to identify activity areas from chemical signals, which fits in really well with our micromorphology.  Certain elements are associated with human activity, for example phosphorus, and by mapping the concentrations across the floors we can get a good idea of the intensity of activity in different parts of a building. Yesterday Scott and his students took readings from the 2 main sequences of midden deposits I have sampled, with the aim of providing a complementary set of geochemical data that can be linked to the micromorphology observations. This way we can provide both a visual and chemical characterisation of the deposits, and hopefully a more secure interpretation of the formation processes and activities that are represented.

Sample block ready for removal
It's been great working here over the past few days. Perhaps not suprisingly, there have been quite a few familiar faces at the site, and it's been great to catch up with a few people. Professor Mark Edmonds from the University of York is here helping out with excavations and providing his expertise on the lithics (some amazing stuff coming out whilst I've been here, again check out the site blog!), and Dr Ben Chan, who I worked with on the Feeding Stonehenge project, is also here running one of the excavation trenches. I also got to meet a few people who I've only ever spoken to by email, including Dr Roy Towers, the pottery specialist who sent me the samples for the pottery residue pilot study I did last year at York, as a side project to the Feeding Stonehenge analysis. I just wish I was able to spend more time on site this year - one of the great things about fieldwork is getting the chance to spend time with like minded folk who share your excitement about ancient rubbish heaps.

Tuesday, 6 August 2013

Investigations at the Ness of Brodgar, Day 1

ORCA project officer Dan explains what's going on with middens
Marvelous midden at the Ness of Brodgar - check out those ashy layers!
Earlier this year I was fortunate enough to be awarded 2 small grants from the Society of Antiquaries of Scotland and the Orkney Archaeological Society, to carry out a pilot microarchaeology study at the Ness of Brodgar site in Orkney. The Ness of Brodgar is part of the Heart of Neolithic Orkney World Heritage Site, and excavations are directed by Nick Card of ORCA/UHI. The site is one of the finest examples of Neolithic archaeology in the UK (along with the rest of Orkney!), and the extent of preservation of the buildings and middens provides a rare opportunity to study the subsistence activities of the inhabitants.
The architecture here is some of the most impressive I've ever seen. It's interesting to note that the dates for the Neolithic here go to around 2500BC - roughly the same date that the Great Pyramid of Giza was constructed. We don't always realise that people were doing equally as impressive things closer to home at this time!
Although much of my previous work has been on Near Eastern Neolithic sites, my interest in the British Neolithic has grown since working on the Feeding Stonehenge project for 2 years, and it is very exciting to have the opportunity to apply my methodological expertise at the Ness.
Yesterday was my first day on site, assessing the deposits and planning a sampling strategy alongside fellow micromorphologist Jo Mackenzie. Jo will be working on building floors, looking at variations in their construction, whilst I will be working on the middens, looking at formation processes and activities. Already in the field we can see some ashy layers in both the middens and building hearths - these will be targeted for phytolith analysis, with the aim of identifying different fuel types that were being utilised. The excavation has its own blog which details daily activities and finds which you can read here. More updates on fieldwork and sampling at this amazing site will follow over the next week!

Thursday, 1 August 2013

Micrograph of the Month: Varieties of Gypsum 1

A: gypsum plaster (Tell Brak, building) B. microcrystalline gypsum (Catalhoyuk, midden) C. gypsum rosette (Kamiltepe, building) D. microcrystalline gypsum (Kamiltepe, external area)
This month we have some micrographs showing examples of some different ways you might encounter gypsum in archaeological thin sections, part 1 as there are a few other forms that I don't have photos of yet but will aquire at some point. Gypsum (aka calcium sulphate) often occurs in Near Eastern samples as a post-depositional feature, where the calcium sulphate salt, dissolved in water, precipitates as the water evaporates. The growth of the crystals can often cause a lot of damage to intact deposits, as the growth of the crystals pushes apart the material. The crystals can have a widely variable morphology, as a result of different formation mechanisms. As well as precipitation from water evaporation, the salts can precipitate due to the solution becoming saturated (i.e. there is so much present no more can be held in the solution), and the type of gypsum crystals has been used in environmental studies as an indicator of aridity. 
In micrographs B and D we can see microcrystalline gypsum, where the individual crystals are very small, and have precipitated within void spaces (in B the void is a crack, in D a plant void). In micrograph C we can see an example of a small 'gyspum rose', where the crystals form a rosette pattern. 
Another type which can be seen in last month's blog is called prismatic gypsum, unsuprisingly due to the single crystals being prism shaped. Similar to this is lenticular gypsum, where the crystals are more rounded and 'lens' shaped. According to Cody (1979), lenticular crystals form in the presence of plant organic matter under alkaline conditions. 
Perhaps the most interesting of these images is A, which shows a layer of gypsum plaster in a building at the site of Tell Brak, Syria in cross polarised light (micromorphology studied by Dr Wendy Matthews, University of Reading). It is very similar in appearance to microcrystalline gypsum, but you can see that it has been prepared as a surface - the pale grey-brown in the lower part of the image shows layers of plaster 'wash' over the thicker gypsum surface.

Cody, R.D., 1979. Lenticular gypsum: occurrences in nature and experimental determinations of effects of soluble green plant material on its formation. Journal of Sedimentary Petrology 49: 1015-1028