A Day of Day of Archaeology (and Snails)

I become quite self-conscious when the time comes to write my own Day of Archaeology contribution. Most of what I did yesterday was to carefully read through the posts that were being submitted to this site, adding new tags or assigning them to categories where necessary, and pressing the button marked ‘publish’. If you’re reading this, the chances are you’ve been reading other posts too, and have a fair sense of what the site is about. I love doing this, I learn quite a lot about the world of archaeology in a day (and subsequent days when I catch up on posts I didn’t catch at the time), and it makes me feel very connected to a group of people worldwide who are doing really interesting jobs. As with last year, I’m full of gratitude for everyone who posted, or commented on posts.

I did squeeze in a little bit of other work. I spent part of the morning processing a very small sample I took from a site on the Somerset Levels here in England. Archaeologists will often take samples of the dirt they’re digging to be sieved through fine mesh (mine went through 0.1mm today – but 0.5 or 0.25 are more usual). This is to look for tiny artefacts, or biological evidence such as fish bones or seeds. My tiny sample accompanies a much larger sample (c. 40 litres) that will be processed later. I just wanted to get a head start to help the other archaeologists on site know what they were dealing with.

Sorting the sample under a microscope

In this case, the sample was all about the snails, which happens to be my main ‘specialist’ interest in archaeology. The site was an intertidal saltmarsh from the end of the Neolithic until the land was drained in the late Medieval period, but must have been dry land before that as we know the sea level was much lower. Unfortunately, the dry land soil appears to have been eroded by the sea. My sample is important because it comes from underneath the first estuarine layer, in a  patch where the old soil was protected by disturbed bedrock.

Some of the snails in the sample

The image above shows some of the snails from the sample at x20 magnification. Even the few in the picture tell quite nice story. The large one at the top and the one at the right of the middle row are a species called Pomatias elegans. This is definitely a land snail, and essentially a snail that likes a warm wet climate, and lives in disturbed ground in lightly shaded conditions. It didn’t arrive in Britain very quickly after the last ice age, so I know the sample is unlikely to be immediately post-glacial. Nowadays it is declining in Britain – it still lives in Somerset, although not on the site I’m working on, and it seems to have been more common in the more humid climate of the Mesolithic. The round snail on the middle left and bottom left (the one on the middle left is the bottom side of the shell) are a species called Discus rotundatus which is a very common species in shaded places today. Like Pomatias elegans, it was quite late to arrive after the last ice age, with evidence from several studies suggesting it became common and replaces a close relative found in cold climates called Discus ruderatus around 8500 years ago. The tall, thin snail at the top left and in the centre of the middle row are a species called Clausilia bidentata which tends to live up trees and on logs (it can also be found on walls). The snail at the bottom right is a juvenile of quite a common species called Cepaea (probably Cepaea hortensis, but I haven’t looked closely enough to be sure yet). European (and east coast American) readers might recognise this shell as large-ish yellow shell, often with brown bands. The colour comes from a layer of protein called the periostracum, which usually deteriorates when the shell is buried – although the brown bands are often preserved.

My hunch then is that the context this sample comes from datesfrom before the site was inundated by the sea, most likely the Mesolithic or early Neolithic, and that the environment at the time was shaded, possibly woodland. I will be able to say more when the larger sample is processed – hopefully containing seeds, small mammal bones and maybe flint microliths, but looking at this small sample now allows me to tell the archaeologists who will be on the site next week that this context might contain some of the site’s earliest finds.