Soil from the longhouse site in Kvarnbo continues to travel abroad 🙂 Comparing to the first batch of soil sent to travel, in much smaller amounts in terms of weight, but in much larger amounts in terms of numbers. 10 samples, ca 20 gram each, with their own special and necessary permit to leave Åland, are at the present moment already travelling (by ordinary mail service) to Umeå, Sweden, in order to be analyzed in the Environmental Archaeology Laboratory at Umeå University for the geochemical properties. I decided for soil chemistry as this method of analysis can help me to interpret, among other things, which post-holes have been affected by fire and which post-holes have not been affected by fire. As there was quite a number of post-holes documented in the trench of rather modest size, it is reasonable to suggest that several phases of building are represented in the archaeological material. By determining which post-holes have been affected by fire and which haven’t, I am much closer to separating these different phases of construction and determining which post-holes might be related to each other. Another question I am trying to find answer to by means of soil chemistry is, if there are traces that might indicate of metal object(s) having been deposited in the post-holes. Theoretically, the method is suitable for answering this question; however, the possibility of unclear patterns is very real as well….
10 soil-samples for plant-macrofossil analysis were collected from 9 features related to the longhouse at Kvarnbo; and 5 samples – 4 from different post-holes and 1 from the wall construction – will this weekend travel to Uppsala in Sweden, where these will be analysed for plant-macrofossils at the Department of Archaeology and Ancient History, Uppsala University.
In general, plant macrofossil analysis (i.e. looking at the parts of plants preserved in the soil) is used in order to build up a picture of past environments, reconstruct past vegetation and, thereby, gain insight into past landscapes and their development; but this method can also provide important information about the use of structures in archaeology. The purpose of the plant-macrofossil analysis of Kvarnbo material is, however, first and foremost, to find datable material with low own age (for radiocarbon dating) such as, charred seeds – these can remain preserved in soil for a considerable time span and can sometimes be found in the absence of all other organic remains. Yet, using macrofossils for dating of features such as post-holes, it is important that the sample would come from the secondary fill of the post-hole, because only then there is a hope for the fill containing residues from the floor level of the construction and, thereby, be contemporary to the construction. The primary fill is the material that surrounds and supports the post once it has been installed, i.e. it is the backfilled earth connected to the installation of the post, and this fill is therefore not containing structure-contemporary plant-macrofossils (but might contain older material). In any case, post-holes are pretty good traps for macrofossils – after the post is removed from the construction, the hole is normally filled pretty fast again with the material from the surrounding. Inside a house, this fill-after-removing-the-post is often consisting of the floor; therefore, the analysis of the material from the post-hole might provide not only datable material, but also insight into the activities that have been going on in the vicinity of the post-holes.
Although only the very bottom of the post-hole features are preserved at the longhouse site in Kvarnbo, the samples sent to Sweden are all representative in terms of the amount of soil needed in order to run the analysis (every sample contains ca 2 liters of soil), also, all the samples were collected from the uncontaminated contexts meaning that these should not be corrupted by younger material from the subsequent use of the area. Now, it is only to hope that these will contain at least some plant-macrofossils, too (because, you know, these could be empty of such material as well………).
As I hinted yesterday, there are some interesting things going on in trench 2 and today’s excavations focused on finding out exactly what is happening there. It seems that the trench cuts two parallel deep ditches containing layers of both black cultural soil and light sand. The cut of the ditches is not symmetrical, but steeper on one side being exactly the same for both. There are also (other) indications of post-holes within the ditches. We have partially excavated the trench to a depth of -70 cm and still we have not uncovered the bottom of these features. Thus, considering how much has been ploughed away at the site of Sa 14.9 in general (as also indicated by the fact that only the very bottom of the archaeological features in trench 1 has survived), we may well imagine that these ditches in trench 2 have originally been quite deep. Our working hypothesis at the moment is what we see is part of a palisade that has surrounded the site. In this connection it is relevant to note that the ditches are close to the edge of a terrace visible with the naked eye. In the cultural layer, which is intersected by these ditches, we started to find fragments of bones, both burned and unburned, which made us water-sieve some of the material from the very bottom of the cultural layer in search of more finds.
Much happened today: tools were sharpened for better digging, which led to easy clean-up of both trenches. With the help of raised tarpaulin, the sun was shaded and the new levels were photo-documented and new 3D models were produced. Thereafter we were ready to start the investigation of the features in trench 1. The number of features in the trench was counted to 15 in total (!) and each was assigned its individual number. We have decided to investigate the archaeological features at our site using vertical cross-section digging through features rather than single contexts. And the investigations so far prove that we indeed have remnants of a longhouse within trench 1, but also, unfortunately, that very much has been removed through subsequent use of the site. As it seems, only the very bottom of the structures has survived… However, things look differently in trench 2 and there are some interesting aspects that I will develop further tomorrow 😉
Today was all about aerial photography which is constituting a part of the documentation at our site using 3D modelling and photogrammetry. Photogrammetry is a process that produces spatially accurate images from ordinary photographs – with these images being georectified we can produce photographic plans of our site and its stratigraphy and take accurate measurements directly from the photo (!). This method is substantially improving the archaeological documentation during excavations and seems by far the best choice for recording topographical data at an archaeological excavation 😉 I am fortunate that archaeologists at the Uppsala University in Sweden are currently developing the method for practical uses in the field and both professor Frands Herschend and dr. Daniel Löwenborg from Uppsala are on a voluntary basis involved in my project. Today’s photo-shoot using a drone was aimed at creating so-called background to all the other data we are collecting at the site.
As expected, we also established that the part of the trench 1 that was soaked yesterday meant archaeological features in that part being much better perceived today than the features in the dry part of the trench. Not to mention how much easier it is to dig when the soil is damp. Obtaining and combining a number of hoses into one 125 meters long hose and connecting it to the tap by the churchyard we have now a method to spray the trenches whenever there is a need instead of carrying buckets with water.
As expected, more and more features are being discovered in the trench 1 – more and more dark spots are uncovered and these are marking the archaeological features constituting the key to the site’s history. And with just about 2/3rd of the trench being excavated to our goal-level of 10.90 m a.s.l., there seems to be almost a feature per square. Which is pretty cool, but also scary, because these features will be difficult to interpret in our trench of just 20 squares. The hall-building itself was sized over 400 squares meaning that our trench is covering less than 5 % of its extent… Considering the number of features being uncovered, often on top of each other and/or blending into one another, it is clear that the building and the site have had quite so complicated history. The need to have much larger area open for the future excavations at the site is clear as it is much easier to interpret hustling features when larger area is open to investigation.
Thus, we have loads of dark spots, i.e. archaeological features, but also a “problem” of nice weather 😀 The weather have been just wonderful, but the shining sun is making the soil very dry and dusty meaning that our features are loosing their clarity for the both untrained and trained eye. Therefore, before leaving the site today, we decided to throw water on the southern end of the trench in order to see if the features are better perceived tomorrow morning in comparison to the features on the northern end of the trench. One thing is clear though, it is much easier to dig the soil that has been drenched at some point.
Today was a lot about post holes – not digging these, but showing off 🙂 To discover the post holes at the site of Sa 14.9 was definitely a great thing and it is cool that our investigations at the site receive such a warm reception from the media as well. And there is no question that the post holes in Kvarnbo are the most famous post holes on Åland right now, although, not yet investigated or even properly cleaned… I’ll have to buy both newspapers tomorrow to see how the biggest of our post holes that was the photographers’ favourite look in print!
While most of the staff was investigating the upper plough-layer in trench 2 (apparently, this is quite so different from trench 1), Agneta and Lars Bertil started further investigating the trench with the post holes. Our goal now is to achieve the same level of 10.90 m a.s.l. in the whole trench; this level is also roughly marking the very bottom of the plough zone. During that work more and more discolorations indicating archaeological features were uncovered and more are to be expected as there is a lot of the trench left to be excavated until the goal-level is achieved. Thus, it is clear that our 3 post holes discovered yesterday are clearly not alone to represent the traces of the longhouse meaning also that the hall was not a short-lived building – it has stood at the site for many-many years, the posts have been replaced, new fireplaces built, internal structure changed, etc. All of which was already indicated by the rather wide time-span of metal detector finds.
– and we have found what we came here looking for: post holes! This is both the relief and pleasure. The post holes found in the hall-trench witness that not everything has been ploughed away, furthermore, post holes we have now uncovered coincide with the anomalies observed in the geophysics data that I used as a guideline in placing the trench to start with, i.e. at this location, the anomalies observed in the geophysics data are clearly representing anthropogenic features. The discovery itself went somehow very quick, Rasmus, Lars Bertil, Frands and Aron were shoveling off the upper plough-layer in one moment and then the next moment Rasmus mentions that there is a big stone here that turned out to be part of the post hole; just seconds later Frands casually mentions that we have another post hole, and my worst nightmare that nothing is preserved from this building that once was standing at the site vanished from my mind.
Because of the discovery of post holes in the trench 1, at the site of the hall building, it felt extra festive that Agneta had baked a cake in order to follow one quite so pleasant archaeological custom that I learned while digging in Sweden for SAU, at the site called Påljungshage in 2007 – archaeologists working in Påljungshage had a custom that the person who uncovered the most notable find of the day had to bake a cake for the next day. And as Agneta was “responsible” for both the spike and rivet found in the upper plough-layer of trench 1 in Kvarnbo we might have insinuated a bit too impertinently that she could bake a cake… 🙂 But it surely felt luxurious to have a cake during our afternoon coffee break!
As post holes were located in trench 1 there was no reason to wait any longer to start investigating trench 2 as well – things to proceed very swiftly at our site and I definitely have my volunteers to thank for that!