Castles and Coprolites

You wait a whole year for a blog post, then two come along at once etc. Following the existential musings of the previous post, I figured I'd better post some fun geoarchaeological stuff. I have been working with a number of colleagues on various projects for the past couple of years, that are loosely related, and fall under the general banner of Human-environment interactions in the Hadrian's Wall Landscape. Regular blog readers will remember in 2021 I talked about the new  excavations at Birdoswald . These have been progressing nicely, and we have uncovered all sorts of amazing finds and environmental material. I have also been working with Dr Eline Van Asperen, and Masters student Damian Rudge, looking at long term changes in the environment, and whether these relate to Roman or earlier activities such as lead mining. In 2022 we were awarded a small grant from the Royal Archaeological Institute  to collect some peat cores with the aid of local volunteer groups. Eline a...

I can't remember if I posted about this earlier in the year, but I was lucky enough to be awarded two student work experience placements as part of the  Newcastle NWE programme , where students complete flexible paid projects within the university. Two of my Environmental Archaeology students have been working for the past few months, digitizing my entire collection of thin section slides. At some point I hope to make these available online as an open access resource for teaching and research. They did a brilliant job! I've only just had a chance to go through all the scans, having been away on fieldwork, busy with exams, then graduation. Here is one of the scans of a thin section from medieval Riga, that I have been working on as part of the Ecology of Crusading project . Combined with the fact I have just moved the lovely Leica DM750P research microscope into my office (kindly purchased by History, Classics and Archaeology ), I can now get working on my mounting backlog of sa...

Something a little bit different for October. This fits in nicely with what I've been up to this week, preparing teaching materials on wood charcoal analysis in archaeology. Although I am not technically a wood specialist, I am wondering if I should pick up a new skill set, as it would actually be very useful as a thin section micromorphologist. This image shows a cross section through an unidentified fragment of wood charcoal in a thin section of sediments from the tower at Cesis Castle, Latvia . There are layers within the sediment that are full of tiny wood charcoal fragments, and actually we see bits of wood a lot when looking at thin sections of ash samples, unsurprisingly. You can see the annual rings quite clearly in this fragment, and it can be identified as a soft wood species (coniferous) due to the lack of pores. Soft woods are a bit more difficult to identify than hard woods (from deciduous trees), as their structure is more simple and less distinctive. In this example ...

Close-ups of decaying waterlogged wood. Upper left showing 1. latewood with secondary cell wall intact 2. earlywood with loss of secondary cell wall. Upper right showing loss of birefringence in areas subject to decay Another fab example of the sorts of things that go on in medieval waterlogged deposits. I posted some pictures of this waterlogged wood a couple of months ago, as well as a nice example of the formation of vivianite in the same deposits . Here we have another example of waterlogged wood, but I've added some close-ups in cross polarised light (XPL). For the non geoarchaeologists in the audience, this is a technique in microscopy where you change the type of light you use to look at a sample, by inserting polarisers on the microscope. Polarised light vibrates only in one direction. On the geological microscope, the lower polariser causes the light to vibrate in an E-W direction, whilst the upper polariser/analyser filters light that is not vibrating in the N-S d...

This month we have a lovely image of a particularly colourful mineral feature called vivianite. Vivianite is an amorphous hydrated ferrous (iron) phosphate, which is blue when oxidised. It has been linked to the decomposition of bone and/or human and animal waste in wet sediments, which fits with what we know about this context. Yes, we are still looking at those waterlogged deposits from medieval Riga ! This is just one example of the many occurrences of vivianite in this layer. The small fragment of wood is also interesting. Unlike the waterlogged wood we looked at a couple of months ago , this fragment has been completely mineralised due to the presence of phosphate in the waterlogged sediment - at first glance I thought it was a bit of bone! You can also see that the pores spaces within the wood have been completely filled with fine sediments, which also indicates waterlogged conditions - the infilling of the voids occurs as fine sediments suspended in water are deposited within...

Here are two examples of waterlogged wood, in deposits from Medieval Riga, currently being analysed as part of the Ecology of Crusading project. It's been almost a year since I started on these slides, which were prepared in December last year - there are so many of them it is taking me quite a while to get through. It's a fascinating set of samples, such a mix of materials with some interesting post-depostional processes going on. In the upper image you can see a fragment of wood preserved entirely through waterlogging, within a mixed deposit containing charred material. This little fragment of wood has been stained orange, which is typical of waterlogging and mineralisation. In the lower image you can see a fragment of wood which has been preserved through a mix of partial burning (as seen by the black colour in the lower part of the wood), whilst the non-charred part has been preserved through waterlogging. Waterlogged deposits are relatively rare - most plant material ...