Day 1: Another one bites the dust

Having already participated in the first, more theoretical part of the Archon geoarchaeology course, I was very curious what would await me in the practical part. Definitely more soils and sediments. Upon my late arrival, I was not disappointed: the task was to examine lacquer peels and to infer from their composition of horizons the kind of soil type on the peel sample. For doing so, the first step was really to determine the different horizons based on the visibly different colours and textures of the soil sample. As we all knew, these differences between the horizons were due to soil forming processes influenced by factors such as climate, organisms/vegetation, parent material, time and relief/drainage (CleOPaTRa in short [the ‘Richard Of York Gave Battle In Vain’ of geology]) and were, naturally, individual for each soil type. After doing so, we ‘measured’ the colour via Munsell as well as the fine -/coarseness of the material in each horizon, which proved to be equally a subjective task. Lastly, we assigned each horizon a number and a letter equivalent to the kind of soil horizon, e.g. the ‘O’ horizon stands for the top layer organic material. After having collected all these data, one should be able to determine the soil type now, which, as turned out in the group discussion of our cases, were mostly podzols, podzols with a layer created by anthropogenic interferences, i.e. an anthrosol, on top of it (fig. 1) and other podzol variations (haarpodzol, for instance).

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Fig. 1: The lacquer peel of a podzol with a thick (plaggic) anthrosol layer on top of it analysed by our group.

However, naturally, there are more soil types than just the mere podzol and its variations. Moreover, one has to consider soils formed by human influence as well, especially when dealing with samples from the beginning of the Holocene and onwards. For exemplifying this, this exercise had the creation of landscape profiles of three archaeological sites on the Northern Isles of Scotland (Netherskail Marwick, Old Scatness, Tofts Ness), which were used during different time periods (Late Neolithic, Bronze Age, Iron Age, Late Norse and Medieval times), as objective. Via various websites, such as www.soils-scotland.gov.uk, we identified the solid geology, soil types, agricultural land classification and archaeological sites and landscapes at said locations and fed our profiles with the data. This exercise should help us to think about and understand the formation of anthrosols in regards of the different ways of lives of people during different time periods. As a method used in geoarchaeology, it also showed us its biases and limitations.

Since especially determining the texture of the material has proven to be difficult, the last exercise aimed to sharpen exactly that – our sense for the texture of the material, accurate to the micrometre. We were given samples of different depths of which we ‘munselled’ the colour and measured the texture again (fig. 2). In addition, we also needed to give indication about the structure of the texture, i.e. slightly silty sand and so on. This kind of analysis required more senses than just the vision: much feeling and tasting was involved (yum!).

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Fig. 2: Samples of different depth. Traces of close examination are visible.

Day 2: Encounters of the clay kind

After the preparatory first day, today revolved around testing our skills in the field. First stop was at Wekeromse Zand. There, we took three coring samples in three different locations. The first point was located next to a field, which has been in agricultural use. Overall, the terrain was quite sandy (drift sand area due to Aeolian processes) and via the ArcGIS Collector app we could see that we are dealing with a podzol region with cover sand at the field to which we were standing next to. The first coring samples were taken in four groups within a distance of about 10 m in between each other. Overall, they showed, moving from the edge of the field towards its middle, a thickening and broadening (plaggic) anthrosol horizon above a podzol (“Stop saying that!”) (figs. 3 – 6). These irregularities might be explained by the undulating landscape character of the field.

 

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Fig. 3: Preparations for taking our coring sample. 

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Fig. 4: Professor Ian Simpson teaching us his coring skills

   

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Fig. 5: Our coring sample showing a podzol with a plaggic anthrosol. 

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Fig. 6: Professor Ian Simpson and Dr. Sjoerd Kluiving contemplating our sample.

Afterwards we moved into a forest on the Wekeromse Zand area, right next to the field. The landscape there was quite different from the one encountered at the field, being very hilly (fig. 7). As our coring samples showed, this was due to accumulated drift sand (“…the Aeolian thing again?”) (fig. 8). The reason why it is drift sand and not a Pleistocene formation is that the sand had a rather greyish, ‘dirty’ colour. If it were originated from a Pleistocene formation, it would have a different, ‘clean’ colour, more yellowish and less greyish (thank Munsell). Moreover, further down the cover of drift sand would probably lay a podzol as well, however it was unreachable for us at that time.

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Fig. 7: Hilly landscape of the forest. 

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Fig. 8: Our coring sample consisting mostly of drift sand and a weak humus.

As a last coring spot at Wekeromse Zand, we walked to the open, sand dune area (fig. 10). There, we looked at a sequence of soil horizons, which was nicely visible at one of the wooded slopes (fig. 9). The cover sand situation was clearly observable as well as the podzol underneath it. We also did a coring in the sand dunes, on whose horizons the difference between drift and Pleistocene sands was noticeably to see: here, the sand had a nicely yellowish tone to its colour.

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Fig. 9: Dr. Sjoerd Kluiving explaining the different horizons visible at the slope.               

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Fig. 10: One can see why people prefer this open, sandy landscape.

 Now it was time to leave the Wekeromse Zand and to move on to our second and last stop, the low lands of the Western Netherlands at Amstelveen. A quick look on the ArcGIS collector app showed, we were on a gleysol area. The difference between the high- and lowlands of the Netherlands was nicely visible by the sluice next to which we took our last two coring samples for the day. The first was taken in the lowlands at around -2 m under NAP, whereas the second was even lower, at -4 m NAP. Overall, they both showed rather humid conditions with nice smelling peat layers. In comparison, however, the ‘lower’ sample was ‘less worked’ by human activity than the upper one, the disturbed layer being much thinner, for instance. During the coring of the lower sample we decided to get deeper to the bottom of the soil. This was a fascinating as well as equally dirty endeavour, as it produced nice clay coring samples, which were, at the same time, very wet and liquid. The fascinating thing about these clay samples was now that, the deeper we got, the older they became (we were at around 10000 ago at one point). They were of varying blue/grey colour and consistency too. In some horizons we even found some clams (sometimes smaller clams in bigger clams), which could have been used as in situ data for dating.

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Fig. 11: Dr. Sjoerd Kluiving taking a coring sample at the higher point of the low lands.

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Fig. 12: The clay core samples from the lower spot of the low lands.

Day 3: I know what you did 10000 years ago – hidden stories in thin sections

The morning of the third and last day we spent with what the next step of any geoarchaeological investigation would be: the microscopic examination of the micromorphology on thin sections taken as a sample from an archaeological site, in this case from the three sites of day 1. We examined the samples for different criteria such as microstructure, the composition of the coarse as well as fine minerals, organic material, anthropic inclusions and pedofeatures. The composition of the thin sections is, naturally, directly influenced by the CleOPaTRa factors as well as anthropogenic activities. The impact of the latter component was especially nice visible since the people lived in different ways during the different time periods. On these grounds, it was visible, for instance, how the amount and quality of the pedofeatures changes considerably when comparing the features of the Neolithic site Tofts Ness with the Iron Age site Old Scatness. A considerable rise in the amount of excremental pedofeatures at the latter site is clearly visible, indicating either a cesspit or the use of manure as fertilizer for the fields. A nice addition to the examination process was the scrutiny of the thin sections under polarised light, which showed the coarse and fine material in an eerie, spacey reversed colour scheme. As hypnotising as these light effects might have been, they made it possible to discern different details on the components, entailing criteria such as structure as well as colours.

After this fascinating view into the micro – verse of micromorphology, it was our turn to show what we have learned during these past days and how we would incorporate geoarchaeology in our own research. Each of us chose our own topic, presenting new research themes such as crysols, identity, and geoarchaeology in the setting of a maritime cultural landscape as well as others such as landscape formation processes and land use over time in the context of a reciprocal relationship between landscape and people. The course was concluded with a quick synthesis of the course and a reflection of the newly learned information as well as aspects.

A few words at the end – what did actually stick to my short term memory student brain?

Overall, I found the course quite enjoyable, the kind of knowledge that was communicated not only useful, but also offering new perspectives for future research methods in archaeology. The atmosphere in the group was harmonious and interested too, which created nice working conditions and made working on the group assignments pleasant. Personally, I think learning how to be able to distinguish and explain soil horizons and formations is important for our understanding of how the archaeological record is deposited and preserved within the ground. Apart from that, the geoarchaeological information provides us with empirical data that can give us a clear notion about land use in the past as well as anthropogenic alterations of the landscape and, naturally, how these choices by past humans were influenced by the soil types and formation processes in the past. Especially the clay coring during the second day at Amstelveen had a bit the overtone of time travel: not only were the samples of deeper depths incredibly old, finding actual clams within them really showed how this whole area was once part of the North Sea. Considering the other field exercises, I think they all showed what vital information geoarchaeology has to offer in terms of reconstructing the past landscape people lived in, much of the information being even online available for free. Because of these low costs and the readily accessible information, it should not be too difficult to create preparatory landscape profiles for sites investigated by a project. Based on this, I believe it might be actually of advantage to use some of the geoarchaeological methods more often as a tool in the general archaeology toolbox.

 

When looking at the presentations of my fellow students, I think it is safe to say they equally enjoyed the course. All of them showed how the incorporation of geoarchaeology can contribute and broaden their own research interests and were in one way or another connected to their interests. Also, I have seldom seen a group of people looking at and touching completely mesmerized and fascinated some old as the hills wet clay ´, contemplating about how the texture and colour changes over time. This is passion as far as it gets without becoming obscene and I am glad I was a part of it. 9/10 recommend this Archon course!