Palaeontological evidence of a Precambrian age of the marbles at the Asenova Krepost Castle (Central Rhodopes, Bulgaria)

The marbles at the Asenova Krepost Castle in the Central Rhodopes lie about 10 km to the south of the town of Asenovgrad. They belong to a lithostratigraphic unit consisting of alternating calc schists, mica schists, marble and amphibolites. Marble surface have been shown to bear marks of palaeontological entities besides the numerous traces of weathering processes, lichens, etc. In several marble sample, examined in this study, specimens of Aspidella terranovica Billing, 1872, Atikokania lawsoni Walcott, 1912, and Chuaria Walcott, 1899, have been identified. These species occur in the Precambrian of North America, and the third one is found also in the Precambrian of Sweden and the Soviet Union. The finds are regarded as conclusive evidence of the Precambrian age of the Asenova Krepost marbles.