Outcrop is located at the east coast of Skälö. Approach via road from Västrum to Skälö,
follow the road to the harbor of Baggeholmen.
This location has two outcrops. At first some flecky gneisses (a) with a premetamorphic ductile shear zone.
They are located along the road at the harbor and extend in east direction to the coast. There, in sharp contact
to the flecky gneisses, some metatuffites (b) with excellent preserved graded bedding are exposed. A wall west of
the flecky gneisses show some reddish metaquartzites, with channel pattern, of the Västervik Formation.
The flecky gneisses are characterized as a medium gray colored, homogeneous or slightly bedded metasediment
with dark gray spots (cf. fig. 4.18a). These spots cause a slight relief on the weathered surface.
On careful observation a zonation of the flecks can be detected: A dark core (melanosome) surrounded
by a lighter rim (leucosome). According Farrenkopf (2000), the dark core consists of xenocrysts of
quartz, biotite and muscovite within an extremely fine-grained matrix consisting of serizite. It is
surrounded by a light rim of quartz-serizite-sillimanite minerals. The main components of the matrix are
quartz, microcline, serizite, muscovite and biotite.
The spots vary from round to elongated, even mylonitic stretched where the rock was involved in an ductile
shear zone (cf. 4.18b-c). These different forms are used as a norm to define the degree of deformation.
The flecky gneisses demonstrate an excellent example of synkinematic metamorphism. Due to the elongation
of the flecks in NW-SE direction Westra et al. 1969 concluded that they where formed in the F2 stress-field.
Farrenkopf (2000) has noticed high-grade metamorphic minerals such as sillimanite, andalusite and additional
cordierite in the Mg-rich layers. Based on detailed microfabric studies he concluded, that the flecky
gneisses have partly been involved in a ductile mylonitic shear zone close to the peak temperature
of metamorphism (650°C), followed by a retrograde overprinting of minerals and texture under K-rich
fluids and static conditions.
The metatuffites adjacent to the flecky gneisses are brown to gray in color and fine- to coarse-grained
with preserved graded bedding. Quartz intruded the layered tuffites concordant and led to formation of
the so-called fir tree fabrics (cf. fig. 4.18e-f).
Dahl, O., 1972: Some Aspects on the Evolution of Fleck Gneisses in the Västervik Area. - GFF 94: pp 69 - 82.
Loberg, B., 1963: The Formation of a Flecky Gneiss and Similar Phenomena in Relation to the Migmatite and
Vein Gneiss Problem. - GFF 85: pp 3 - 109.
Russell, R.V., 1969: Porphyroblastic Differentiation in Fleck Gneiss from Västervik. - GFF 91: pp 217 - 282.