This is maybe like clay, but really compressed and dead material. Hence a clean horizontal cut, so you don't introduce more air into the soil.
I think this is first layer of stones.
When you are at a good height you start stacking or mounting the 'stubbe' or stabb, as in stabbur. Pole in English.
We fix it as they would have built it. That is sort of work the firm I work for does.
