Ai. Okay et al., The tectonics of the Strandja Massif: late-Variscan and mid-Mesozoic deformation and metamorphism in the northern Aegean, INT J E SCI, 90(2), 2001, pp. 217-233
The Strandja Massif is a mid-Mesozoic oro genic belt in the Balkans build o
n a late-Variscan basement of gneisses, migmatites and granites. New single
-zircon evaporation ages from the gneisses and granites indicate that the h
igh-grade metamorphism and plutonism is Early Permian in age (similar to 27
1 Ma). The late-Variscan basement was unconformably overlain by a continent
al to shallow marine sequence of Early Triassic-Mid-Jurassic age. During th
e Late Jurassic-Early Cretaceous (Oxfordian-Barremian) the lower Mesozoic c
over and the basement were penetratively deformed and regionally metamorpho
sed in greenschist facies possibly due to a continental collision. An Rb-Sr
biotite whole-rock age from a metagranite dates the regional metamorphism
as Late Jurassic (155 Ma). Deformation involved north-vergent thrust imbric
ation of the basement and the emplacement of allochthonous deep marine Tria
ssic series over the Jurassic metasediments, The metamorphic rocks of the S
trandja Massif are unconformably overlain by the Cenomanian shallow marine
sand stones. During the Senonian, the northern half of the Strandja Massif
formed a basement to an intra-arc basin and to a magmatic are generated abo
ve the northward-subducting Tethyan oceanic lithosphere. The Srednogorie ar
e closed during the early Tertiary through renewed northward thrusting of t
he Strandja Massif.