Tag Archives: Interpretations

The life of a post-hole

with Kim Darmark

Anl_211

Digging post-holes can be rather tedious, non-rewarding work. Cut through, photograph, document the section, take samples and on to the next one. To a certain extent, this has been true at Kvarnbo as well, but a surprising number of the post-hole remains have, on the contrary, been challenging and exciting to investigate. This is due partly to the fact that so many of them have a life history which is possible to reconstruct. It is often possible to follow the events that have taken place through the different constructional elements making up the feature. In quite a few cases, it is possible to see the edges of the original pit, filled with a lighter primary fill, which was deposited in the pit at the moment of its construction. This fill is often lined with stones, creating a solid base for a beam to rest on. Both naturally rounded stones from the surrounding and rugged, fire-cracked blocks of stone have been chosen for this purpose. The primary fill contrasts markedly from a darker secondary fill, which enters into the pit at a considerably later date, when the old supporting beam is removed from the pit. The darkening of the fill represents many years of intensive use of the site, during which large amounts of organic remains have been tossed on site, creating refuse layers, usually referred to as cultural layers. This dark soil only infills the small chamber that is produced by the stones in the stone packing, and is often also rich in finds, which constitutes the other interesting aspect of post-hole investigation at Kvarnbo. Since we sift the soil through sieving net using water, we find every little find, even tiny ribs, scales and vertebrae from fish, which has ended up in the post-hole. The usual finds are bones and pottery, but a few less common items have been found as well, such as pearls, and small copper loops. Almost every feature that has been investigated this season has contained at least a few finds, some of them large amounts, and gives testimony to the richness of the cultural layer once present at the site.

Press this link to see the 3D model of feature 211 during investigation 😉

Traditional Strategy and New Techniques

by Frands Herschend

Strip (off the plough soil), map (the patterns you see) and sample (material from mapped structures) – is an archaeological field strategy applied to settlement remains in agricultural land, where crops have been growing for centuries. Ultimately, the method has become prolific, because of the gradual shift in the use of the cultural landscape. This shift made arable land more important and organized not least by means of roads. Consequently, farms were moved out of the farmland when possible. In Iron Age, on the other hand, arable land was less important, while grassland and meadows contributed substantially to subsistence. Not surprisingly, a rational Iron Age farm situation was in the centre of the farm’s agricultural area. Few roads were needed.

In Kvarnbo, change has been model, and today, the farms at Johannisberg are situated next to and above the arable land in which the Iron Age Kvarnbo hall stood on its small drained hillock.

When the excavations were planned, the strip, map and sample method was the obvious choice. But there are different way of stripping, mapping and sampling, and at Kvarnbo we have introduced a new mapping method in order to develop the general method. The testbed was successful during the test excavations in 2014, and in 2016, this mapping method was developed to become a routine.

Except for a handful of GPS reference points defining some of the test pits before the excavations started (see here), nine main reference points were defined after the top soil was stripped off in the area of over 1000 m2, and complemented with 183 reference points inside of that area. Supported by these, all (georeferenced) exact measurements, plans and sections are based on photographic 3D models. Also, a large scale plan was made with a drone during a 10 minute photo session and its orthographic projection, printed as an overview, has enabled the team to orientate itself on the site.

New techniques

Archaeological documentation goes hand in hand with interpretation. Description dominate fieldwork without excluding interpretation, and in the field, ocular observation is the general mode of perception: either you see something of you don’t. Later on, during the report writing process, interpretation and lab results dominate in order to answer the question: what cultural phenomena have we excavated? The problem in field archaeology is not what one observes, the problem is that which cannot be seen.

Overlapping features in the trench of 2014

In this section from the trial excavations of 2014, one can see archaeological features from Late Iron Age (A12 and A13) been transected by more modern plough furrow (A18).

For instance, looking at plough layer and plough furrows or any other depression, the point is to describe some sort of “ploughing biography” of the field as a part of the its involvement in history. It is easy to see the dark furrows when they cut into the yellow underground, but difficult to detect them at the bottom of the plough layer, and impossible higher up, although they may well exist in soil 20 centimeters or more below the surface. In fact, only by means of close observation of soil sections can one distinguish between ploughed and not ploughed soil.

Since we want to sample the contents of the different fills in postholes, we make a preliminary section of the first centimeters of the soil until, based on this section, we can dig away the plough soil, that is, the contamination of the prehistoric fill. As a result, we can, for example, conclude that the burnt clay, which represents burnt walls and was abound in the test pits, doesn’t exist in the postholes of the hall (because it was never burnt down).

So far, we have sectioned, described and interpreted c. 230 features of 273 on the c. 1000 m2 of our site. This is time consuming, but the ensuing 3D documentation is fast. On average, therefore, a team of four professional archaeologists and 2-3 amateurs can section, describe, interpret, sift and model 20-25 features per day, and sample soil for chemical and macrofossil analyses. 3D-modelling brings a new better and cheaper standard to strip, map and sample methods.

 

Post-holes

One by one, archaeological features at the Kvarnbo Hall site, mainly post-holes, are being investigated. And there is a number of really pretty ones among these post-holes – several are preserved much better than I expected (about 0,4 m in depth), and every so often, there is a stone packing evident. In at least three cases so far we have post-holes that have been filled with the material from a hearth and thereby filled with finds of bones from many different creatures (including fishes and birds) as well as pieces of pottery. Every  post-hole not yet investigated is therefore like an unopened package, whose contents are still unknown and it is up to us to unwrap the mystery 😀

Post-holes

Week 5 – brief summary

Anläggningar undersöksThis week we had Daniel flying the drone over the cleaned surface, barely beating the rain, and giving us the much needed overview picture of the site. The overview picture confirms what we suspected – features are scattered over a large part of the trench and beyond the boundaries of our investigation. The majority seems to be circular post-hole like features very varying in size. A couple of centrally located features excite us with both their size, placement and relation to each other 😉 Some features can already at this stage be viewed as hearths and are mostly situated in the southernmost part of the trench. Otherwise, the surface is quite obviously dominated by plough furrows, hundreds of them, as well as a couple of long ditches transecting the entire site. We have numbered and individually photographed 246 archaeological features defined so far and have also started to make cross-sections through some of them. Investigating the features will dominate the rest of the excavation. Sadly, that will be done without help from Anton and Peter, both of whom have been with us 4 weeks and have proven themselves to be true troopers of archaeology – their effort was highly appreciated and will be missed. They left together with Jonathan and the remaining, diminished team thus has the fortune to investigate all the features no matter the weather 😀

 

Plow layer as context…

Plogjord som kontext…is the name of a brand new collection of articles by researchers who gathered in Oslo to discuss the scientific potential of soil that has been heavily disturbed by plowing. This is a theme that naturally concerns our project as well. In many countries, the plow layer is not regarded as constituting an ancient monument (sw. Fornlämning) due to the fact that the finds in the layer can no longer be tied to a specific context. This is also the reason why continued plowing of fields with traces of prehistoric settlements is allowed, since the ancient monument is considered to be the destroyed features below plowing depth and not the plow layer itself.

At the same time, the finds from the plowed horizon can, on a more general level, give important scientific information. Christiansen (2016) discusses the plow-related movement of coins from prehistoric hoards and concludes that, even though parts of the hoards can be found over 80 meters from their original position, most of the finds can be found within a few meters, up to 10 meters from where they were originally buried. This is of course also modified according to terrain, mode of cultivation and morphology of objects. For example, large irregular objects are transported more easily by the plow than small, regular pieces.

The effect of repeated plowing on underlying features. From Martens 2016.

The effect of repeated plowing on underlying features. From Martens 2016.

When we decided to manually investigate the plow layer at Kvarnbo through systematic sampling, it was partly based on the idea that we could obtain rough spatial information from finds, which could be related to both the information from the infrared photography showing the contours of the building, and also to the features hopefully to be uncovered at a later stage. Another aspect was the collection of Iron Age finds other than metal, such as pottery, glass, bone, clay daub etc, which would give qualitative information to the site as a whole.

The results look promising so far. Judging from the finds from the initial test pits registered, in the western part of the building, many of the find categories (burned clay, burnt and unburnt bone in particular) seem to be concentrated outside the building itself, while the inside is relatively empty. Maybe this means that there is still a possibility to reconstruct a general picture of the find distribution within and without the house? It is also encouraging to see, that the amount of obviously later finds is not as high as predicted. Certainly the plow layer contains porcelain, modern glass, etc, that cannot be connected to the use of the site during the Iron Age, but there is a chance that a large portion of the finds are to be associated with the building. This is certainly the case with the Iron Age pottery and the glass beads unearthed to date!

Read more about the subject in J. Martens & M. Ravn (eds.). 2016. Pløyejord som kontekst. Oslo.

by Kim Darmark

Talking

Lecturing in the school of Strandnäs. Photos by Kjell Söderlund

Lecturing in the school of Strandnäs. Photo by Kjell Söderlund

Several months have passed by in silence on this channel – but it doesn’t mean that I have been silent otherwise and, especially, regarding the Kvarnbo Hall 😀 The thing is that I have actually talked a lot, and I mean a lot, as for the past 3 month I have had a serious “tour” in the primary schools of Åland talking about the Iron Age on the islands. The gist of my lecture was “walking through” the Iron Age on the Åland Islands, talking about archaeological interpretations and what are these based on, about how archaeologists work. The lecture was intended for the pupils that already have prehistory on their syllabus, and in these parts of the world, it meant mostly fourth graders (i.e. students are around 10 years old), but on some occasions even the 5th and 6th graders were participating. This was the first time for me officially holding lectures for children and I have to admit that it was actually a lot of fun. I never got tired of holding basically the same lecture over and over again as every lecture turned out to be different from previous ones. Reason for this was probably the fact that children ask a lot of and different kind of questions 🙂 It became obvious for me that their attitude towards lectures is so much different from adults as there is no question that children are afraid of asking. And, you know what, none of these questions was actually irrelevant to the topic in general – well, maybe except the questions about my age, which seemed to turn up several times 😀  All in all, it was a really positive experience for me and what I have heard from teachers afterwards, equally enjoyable for pupils. It made me especially happy to hear about a pupil who otherwise was so uninterested in anything that has with school to do, but was after my lecture afire with enthusiasm declaring that this was the best lecture ever. But at the same time, archaeology is very interesting (….it just makes a really bad main career…. but that is totally another story), and I am now certain that I don’t mind having lectures for children even in the future!

In addition to talking about archaeology, I have, of course, also been working with the preparations for the summer’s excavations in Kvarnbo, but more about that in my next post 😉

Little dragon (aka: melted brooch)

Different find categories registered during metal detector surveys at the Kvarnbo Hall site so far show no particular spatial concentration, except for the fragments of bronze (and/or possibly copper). Analysing find distribution, there is clearly an area at the site where most of the finds documented are pieces of bronze clips – the area is situated on the north-eastern side of the longhouse, some 50 m from the corner of the hall building. While I was working in that zone and documenting these fragments, it was, furthermore, pretty obvious that the soil is also hiding significant amounts of iron exactly in the same area. So, either there is a modern metal thingy ploughed apart at that spot, or we could speculate about a prehistoric craft area. On the basis of the metal findings, I am cautious in assigning this area to solely prehistoric activities without further investigations, because among the fragments documented, there is awful lot of pieces that are very thin and have sharp edges, looking fairly recent to me… But, at the same time, there are also fragments that are clearly old: thick droplets, melts and twisted rods of bronze coated with nice patina as well as clips with worn-out round edges. Furthermore, among the finds of this category, there is a melted brooch section definitely of prehistoric origin (it kind of looks like a little dragon 🙂 ). Thus, I am pretty sure that one has engaged in the art of metalcraft at the Kvarnbo Hall site, and assuming that, I would start looking for the craft area in this particular zone “infested” with iron and with a high concentration of the bronze fragments.

Bronsbleckillu