Two metasedimentary complexes are exposed in the Sudetes Mountains
of
Poland, Germany
and the Czech Republic. Succession I comprises pelites and greywackes of
Neoproterozoic–Cambrian age,
deformed and metamorphosed prior to intrusion by S-type porphyritic granites
at
515–480 Ma. Succession
II comprises a sandstone–mudstone–chert sequence and
turbidite sequence of Ordovician–early
Carboniferous age accompanied by bimodal volcanogenic rocks. Both
successions were intruded by late- to
post-orogenic granitoid intrusions at 340–300 Ma. The sedimentary
rocks of succession II show increasing
maturity until mid–late Devonian times. Inversion of the basins,
commencing in late Devonian–early
Carboniferous times, was reflected in the emplacement of turbidites
and olistostromes, concurrent with the
uplift of a metamorphic core complex of succession I rocks. The
original stratigraphic order of the successions
was maintained, thus crustal imbrication was not significant. Instead,
extensional faulting became
important, followed by transpression on almost orthogonal fault zones,
resulting in the presently observed
juxtaposition of crustal blocks. The Palaeozoic sequences developed in
mainly ensialic basins on Cadomian
and older basement, parts of which became strongly reworked (2.6 to 0.54
Ga
zircon inheritance ages) and
incorporated into the Palaeozoic structures. The orogen developed either
on the
rifted margin of peri-Gondwana
or on a rifted-away fragment of pre-Baltica. The Sudetic section of the
Variscan Orogen is of
broadly Alpine style, with significant basement involvement, but apparently
without evidence for long-lived
subduction of wide oceans or the accretion of numerous exotic terranes.
The origin and early radiation of terrestrial vertebrates