Detalhes do Documento

Dervent Heights are one of the least studied parts of the Strandja zone in Bulgaria. Our detailed field studies in the area of the villages of GoIiam and Valcha PoIiana show the need of revision of the earlier models for nappe tectonics in this pari of the Alpine orogenic belt. Two major units could be distinguished in the pre-Cenomanian basement - autochthon and allochthon. The autochthon is built by Variscan high-grade metamorphic rocks and not penetrativelly deformed granitoids. They are covered by low-grade Triassic metasediments. The allochthone consist of phyllite formation with early Paleozoic age, as well as the underlying carbonate and detrital metasediments. These metasediments form a mappable unit here designated as carbonate terrigeneous formation. Field data allow to reconsider the position of the abundant dolomites. It was suggested that they are forming the autochthon, but the field relations are consistent with interpreting them as a part of the carbonate-terigeneous formation. All studied rocks record very low-grade Early Alpine metamorphism (T<3OO-350'). The metasediments of the autochthon as well these of the allochthon display evidence for strong synmetamorphic deformations and because of that primary structures are not preserved. The timing of the emplacement of the allochthon is poorly constrained, but judging from the lack of localization of ductile as well as of brittle deformation along the major contacts it could be suggested that the emplacement was pre- to synmetamorphic.