Roadcut on the eastern wall along highway E22 about 2.4 km northeast of the exit to Gunnebo.
Park in a parking bay about 100 m north of the outcrop. For preservation of the limited amount
of material please refrain from taking any samples!
The roadcut on highway E22 shows a 3 to 5 cm thick sedimentary dike, which is steeply inclined and strikes
almost N-S (cf. fig. 4.6a). It is not possible to track the dike in the surroundings of the outcrop.
The host rock is a granodiorite, which according to a description by Gavelin (1984) belongs to the older
granitoids. The granodiorite is dark and coarse-grained without any visible foliation. Big red alkali feldspar
phenocrysts cause the porphyry fabric. Other main components are white, medium to coarse-grained
plagioclase and fine-grained quartz. The mafic fraction with a percentage of 20 - 25 % is mainly biotite,
which accumulated in cm to dm large round or ovoid mafic enclaves. They may be interpreted as former
drops of a magma mixing phenomenon. Behind the bridge the wall on the opposite side of the road shows
an enriched area of deformed mafic blobs within the rock (cf. fig. 4.6f).
The sedimentary dike contains a lot of detrial components. According to a description by Jacke & Vollbrecht
(2004) rock fragments are mainly from the surrounding granitic rocks. Overall the main part of the dike is
the monomineralic detritus. It contains mainly well-rounded quartz grains (cf. fig. 4.6b-d). Many of them have
zircon, biotite, gas or fluid inclusions. The feldspar grains, in minor frequency, are subangular in shape. Fresh
plagioclases and alkali feldspars often have inclusions of biotite, zircon and rutile. Biotite, zircon, rutile and apatite
grains only occur as minor components. The sedimentary dike is consolidated by a calcite cement and a clay-silt
matrix. Jacke & Vollbrecht (2004) described several stages for the development of this dike (cf. fig. 4.6e).
This and other sedimentary dikes within the Västervik area, as well as others found in Denmark and Finland,
are supposed to be of early Cambrian age and can be related to an extensional environment at that time.
Which consequently means that the Proterozoic surface already must have been eroded to a surface level in
which fissures in granitoids could be filled with sediments.
Bergman, L., 1982. Clastic dikes in the Åland Islands, SW Finland and their origin. In L. Bergman,
R. Tynni & B. Winterhalter (eds.): Paleozoic sediments in the Rapakivi area of the Åland Islands.
- Bull. Geol. Soc. Finland, 317: pp 8 - 32.
Katzung, G. & Obst, K., 1997. The sandstone dike swarm of Vang, Bornholm -8Denmark). - Bulletin of the
Geological Society of Denmark, Vol. 44: pp. 161-171.
Tynni, R.,1982. On Paleozoic microfossils in clastic dikes in the Åland Islands and in the core samples
of Lumparn. In L. Bergman, R. Tynni & B. Winterhalter (eds.): Paleozoic sediments in the Rapakivi area of
the Åland Islands. - Bull. Geol. Soc. Finland, 317: pp 8 - 32.
Jacke, O. & Vollbrecht, A., 2004. Sedimentgänge in proterozoischen Graniten der Västervik-Region
(SE-Schweden), Terra Nostra 2004/01, TSK X: 10. Symposium Tektonik, Struktur- und Kristallingeologie, Aachen,
31.03. - 02.04.2004, Abstr.: 35.