Sten – Kalmar

I am a block of red and fairly coarse Småland granite from Näs, where Astrid Lindgren was born, in Vimmerby in Kalmar county. Since I'm a loose block that came to Näs with the inland ice, it's not really possible to say exactly where I come from in the solid bedrock, but it's probably not that far away. I look like a very typical Småland granite, of which there is a lot in this part of Småland and in southern Östergötland, and which has an age of about 1800 million years. So that is probably my age as well.

At that time, Sweden and all of Baltica, i.e. the north-eastern part of today's Europe, were becoming part of the supercontinent Columbia which was being formed. All, or almost all, of the Earth's continents were gathered into this supercontinent, although it is not known exactly what it looked like and where all the continents of the time were located. But Sweden was quite certainly close to the edge of this supercontinent, facing the ocean, and along this edge there was a lot of activity. Between about 1810 and 1750 million years ago, magma was pushed up to form granites and related intrusive rocks in a north-south belt that stretched from Blekinge and Småland in the south, up through parts of Östergötland to Värmland, and then into what is now the mountain range (it didn't exist then) all the way up to Lofoten in northern Norway. So I am one of all these granites, about 1800 million years old. Some of the magmas, especially in Småland, flowed out onto the land surface of the time and formed volcanic porphyries, much like the Dala porphyries a hundred million years later.

So in Småland, where I come from, these granites and porphyries are called Småland granites and Småland porphyries, respectively. Then they may have other, even more local names. The granite at Vimmerby and to the north is sometimes called Vinmmerby granite. Closer to the coast, towards Oskarshamn, some of the granites have been quarried as building stone, just as with other rocks along the coasts of Blekinge, Halland and Bohuslän.

In contrast to the gneisses further west, in western Småland and Halland, the rocks in the granite-porphyry belt through eastern Småland are quite well preserved, even though we are about a hundred million years older than the gneisses. But we have been more sheltered and not affected by any major mountainbuilding event with deformation and metamorphism (transformation at high pressure and high temperature) since we were formed. That is why we have retained our youthful appearance, despite our age.

Geologist Åke Johansson
Swedish Museum of Natural History