As the old saying goes: the field of geoarchaeology is as clear as mud. Literally. After spending some time digging into geoarchaeological research questions and tools during the ‘Geoarchaeology course’ at the VU, it became clear to me that every archaeological project is in need of a solid geological base. Sherds, pots, bones and ruins are – almost – worthless without a proper evaluation of the context in which they were found. And if we did not find any archaeological artefacts, can we actually see how the landscape would have looked like in the past? And how?

Figure 1 – Part of the geo(archaeo)logists’s toolkit

 

Ice ages, field cultivation and manure

If we were to take a trip from Utrecht, the middle of the Netherlands in any direction – west, east, north or south – the landscape would not change very dramatically. However, if we were to dig a bit deeper into the past of the Netherlands, we would find remnants of a past landscape that was very different from what it is today. By looking at the formation of soils, the size of the sand grains, the colour of the different layers in the ground, there is a bulk of information that will tell us about the thick masses of land ice that would occupy the north of the Netherlands for example. Not only would a reconstruction of the landscape in the past be very useful in creating a context in which we can place our flint tools and bell beakers, it also raises more archaeological questions.

One of the main questions which come up when investigating a past landscape is how people have lived in the past? What kind of areas did they prefer? Nowadays, the Dutch live in safely a land that is partially below sea level, because it is protected by dikes, dunes and the delta works. These are all (partially) man-made structures which prevent the Dutch from having wet socks. However, apart from some sand dunes, the rest of these structures were not present in the past. We assume that past populations might wanted to have dry feet and sought a higher place to settle. With geoarchaeology such assumptions can actually be tested.

From macro to micro

The geoarchaeological toolkit comprises of a large range of tools to describe and investigate the soils and sediments. These tools range comprise of large scale investigations of the soil through coring up to 7 meter deep and creating a deep profile of the sedimentation and/or soil formation. By describing the colour, texture, structure and more, the way of deposition and soil type can be determined. These information can lead to e.g. the reconstruction of the past landscape, how much energy was needed to deposit sediments and most importantly to archaeologists: if the landscape was altered by human interference. Analysis also takes place onto a much smaller scale: thin sections of profile sections can be analysed macroscopically. Within these thin sections, inclusions of organic matter, types of grains and organisation structure can tell us about the ways humans modified the soil, type of manure and more.

 

Figure 2 Example of a thin section magnification.

 

 Figure 3 Good example of a carbic podzol profile, a natural occurring soiltype in the Netherlands

 

Applications within archaeology

Apart from habitation and how the landscape in the past must have looked like, soils and sediments also have an impact upon your own body. Yes, your stomach might be affected if you have been trying to distinguish silt from clay by tasting it – and especially when you are trying to determine the texture of an anthroposol (a soil type which has been altered by human interference) that might have been fertilized with human manure. However, I am talking in particular about teeth here. Certain elemental ratios from the soil end up into our diet. In the case of strontium, these elements substitute for calcium in our teeth and can provide a useful tool to archaeology. The strontium ratios depend mostly upon the bedrock, the soil and sediment types, hydrology and rainfall and represent the combination of all of these factors within the area where you grew up. At least, in the past this was the case (nowadays we hardly eat locally produced food). Again, soils and sediments from another good application from the geoarchaeological toolbox!

All in all, this toolbox creates opportunities for the geoarchaeologists to further their knowledge on the context of archaeological sites and material. With these tools, the mud surrounding the archaeological material becomes more clear and can provide the necessary context archaeologists long for. Apart from contextualising archaeological material and sites, it also creates awareness of the area I am surrounded in. I am now aware that every colour, particle size and composition – just to name a few - can be used to recreate a past landscape. The ground below my feet has never been this interesting.

Figure 4 Determining the texture of material from the archaeological site of Tofts Ness, Scotland.