Tag Archives: Soil chemistry

Results from the geochemical analysis

Finally, the results of the soil analyses are tripping in! In autumn, I sent quite a lot of soil from the longhouse site in Kvarnbo to Sweden to be analysed for plant macrofossils as well as for different geochemical properties of the soil; and, now, I have received the report from Samuel Eriksson from the Environmental Archaeology Laboratory at Umeå University. Samuel analysed 10 samples, ca 20 gram each, for parameters such as MS, MS550, CitP, CitPOI and LOI 😀 (you just got to love the abbreviations instead of lengthy explanations, don’t you!) – In any case, MS stands for magnetic susceptibility of soil, which reflects the presence of magnetic iron-oxide minerals resulting by burning, meaning that fire increases the magnetic susceptibility of soil. MS values are for the “natural” magnetic susceptibility of the soil in the original sample, while MS5500 values stand for the results after heating the original samples at 550 °C in the laboratory. Laboratory-induced heating is executed since the magnetic susceptibility of soil may be naturally high or low without connection to anthropogenic processes and laboratory ignition is kind of reference to the original samples. Simply put – this analysis tries to find out if the site/feature has been affected by fire. CitP and CitPOI are related to phosphates – both the organic and inorganic fractions, where CitPOI gives a reading of the sum of inorganic and organic phosphate. LOI stands for the amount of soil organic matter. Basically, these analyses try to find out if lots of organic waste has been deposited on the site or in a certain feature. And, below, you can see the results:

markkemi

What does these “pillars” say? Well, one of my main questions while sending in the soil for the geochemical analysis was to find out which features have been affected by fire and which haven’t, in order to, among other things, separate different features from one another and find out if the longhouse has been burned or not. And the answer is in the MS values – features connected to the structure of the house interpreted as a feasting hall do not show traces of being burned! However, as you can see, two features deviate from the general MS pattern and can be seen affected by fire and at least in case of one of these features, I do wonder if it represents the bottom of a hearth? These and LOI values will be interesting to relate to plant macrofossile analysis results when I get hold on that report as well.

Continuing soil-travels

soiltravelsSoil 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….