Biostratigraphy and tectonic significance of lowermost Cretaceous carbonate rocks of the Circum-Rhodope Belt (Chalkidhiki Peninsula and Thrace region, NE Greece)

Abstract The field relationships, biostratigraphic constraints and paleoenvironmental conditions of lowermost Cretaceous platform carbonates from the eastern part of the Vardar Zone and the Circum-Rhodope Belt are studied. Field data confirm the unconformable position of non-deformed and non-metamorphosed limestones over Upper Jurassic back-arc rift-spreading ridge Sithonia ophiolites of the Vardar Zone in the Chalikidiki Peninsula and deformed arc-related greenschists of the Circum-Rhodope Belt in Thrace region. The distinguished microfossil assemblages and foraminiferal morphogroups are compatible with deposition in a shallow-water environment adjacent to the continental margin of Eurasia. The morphogroup characteristics support such interpretation and newly discovered microfossils define the age of the limestones as Berriasian to early Valanginian. The microfossil data conform to available radiometric ages for the Late Jurassic ophiolite crystallization and time equivalent Circum-Rhodope Belt thrust tectonics. Hence, the obtained results provide sedimentary evidence for pre-Berriasian accretion of the eastern Vardar Zone ophiolites to the continental margin and completion of the Circum-Rhodope Belt tectono-metamorphic history. The earliest Cretaceous sedimentation extended along the whole length of the Circum-Rhodope Belt across the north Aegean region implying a region-wide development of a carbonate platform which postdated the imprint of an important tectonic event. The sedimentation seals the Late Jurassic-Early Cretaceous Balkan orogenic event in the internal Hellenides at the Eurasian plate margin. This conclusion has strong implications for the geodynamic evolution of the Alpine Belt of the North Aegean region.