The Caledonian deformation of the Brabant Massif and the Rügen
Early Palaeozoic has been
compared by structural analysis including strain determinations, X-ray
texture analysis, illite crystallinity
and vitrinite reflectivity. Both areas have experienced weak internal
deformation under anchimetamorphic
to very low-grade metamorphic conditions. The deformation of the Brabant
Massif
is characterized by (a) a
pronounced diagenetic foliation which resulted from compaction and weak
extensional tectonics; (b) tilting
or weak folding of the Cambrian strata around the Cambrian/Ordovician
boundary without internal deformation;
(c) a main phase of Caledonian deformation in the Lower Devonian which
was
associated with open
folding and an axial-plane pressure solution cleavage; (d) bending of
Caledonian structures from northwest–southeast to northeast–southwest.
The internal deformation appears homogeneous with decreasing
strain values towards upper structural levels. The strain ellipsoid is
predominantly prolate with the main axis
of extension parallel to the bedding–cleavage intersection lineation.
It
is interpreted as the result of superposition
of compaction, tectonic shortening and volume loss through pressure solution.
The Rügen Early
Palaeozoic is less deformed and less metamorphosed under anchizonal conditions.
While the upper structural
level is almost undeformed, towards the deeper structural levels a spaced
and
then a continuous slaty
cleavage is developed which is successively crenulated by a fracture cleavage.
The internal deformation
appears inhomogeneous due to several thrust zones with somewhat higher
strain
values. Outside the thrust
zones strain values increase towards lower structural levels, but not
significantly. The strain ellipsoid is prolate
with a strongly varying orientation of the X-axis. The structural inventory
of
both areas is comparable
with other fold-and-thrust belts. While the Rügen Palaeozoic represents
an
imbricated thrust-fan of an upper
structural level with discrete thrusts and inhomogeneous strain, the Brabant
Massif represents a deeper
structural level dominated by folding and more homogeneous internal deformation.