Crystalline crust examined along the seismic profile LT-7 is
subdivided into four blocks separated
by distinct vertical fractures. The northeastern block belongs to the East
European Craton (Baltica). Its
three-layer structure is similar to that of the Svecofennian crust farther
to
the northwest. The southeastern
block reveals typical, two-layer Variscan crust. Both central blocks have
a peculiar structure not comparable
with the crust of the Danish and North German areas: two lower layers,
with
velocities identical or close to
that of the cratonic lower and middle layers, are extremely thin, and an
upper layer, 8–11 km thick, shows
surprisingly low velocities. This upper layer probably represents the folded
and weakly metamorphosed
Lower Palaeozoic sequences, although the connection with undeformed epicratonic
cover cannot be
excluded. Significant differentiation of crustal types in different
segments of the Trans-European Suture
Zone favours the concept of tectonostratigraphic terranes which collided
with Baltica.