The early Cretaceous and younger opening of the Black Sea has obliterated much of the older record of Tethyan subduction below southeastern Europe. The earlier Mesozoic evolution was dominated by opening and closure of Tethyan oceans between Gondwana and Laurasia with their consumption, at least in part, accommodated along the southern Eurasian margin. Crimea (Ukraine), a peninsula in the northern Black Sea, represents the northernmost region of southeastern Europe that exposes a record of a pre-Cretaceous Tethyan active margin. To shed new light on the paleosubduction zone configuration of the southeastern European margin in the Jurassic, we report 40Ar/39Ar isotope dating on 10 samples and whole rock geochemistry on 31 samples from supposedly Jurassic magmatic rocks from the Crimean peninsula. The samples can be subdivided into two age groups: middle Jurassic (~172-158Ma) and uppermost Jurassic to lowermost Cretaceous (~151-142Ma), that both have a subduction-related geochemical signature. The ages of the younger group are in conflict with previously assigned biostratigraphic ages of the units under- and overlying the volcanic complex. This might suggest a scenario where the latter were juxtaposed by faulting. We argue that the Crimean volcanics represent a fragment of a volcanic arc overlying the southeastern European continental margin. These data therefore provide evidence for Jurassic northwards subduction below the Eurasian margin, preceding the opening of the Black Sea as a back-arc basin. We argue that the corresponding Jurassic trench was already positioned south of the Turkish Pontides and the Caucasus belt, implying a very shallow slab angle in the Jurassic.
Bibliographical noteFunding Information:
The geochemistry data are part of the MSc thesis of BV, the research was carried out at VU University Amsterdam. We would like to thank Françoise Chalot-Prat for her help with inspection of the thin sections. Roel van Elzas is thanked for his help in the mineral-separation lab. The authors would like to thank a number of people for their help in the field and for discussion: Vladimir Bakhmutov, Sergei Bolotov, Tommy McCann, Françoise Chalot-Prat, Martijn Deenen, Wout Krijgsman, Yann Rolland, Oleg Rusakov and Stephen Vincent. The manuscript benefited from the comments of two anonymous reviewers. DJJvH acknowledges StatoilHydro for financial support (SPlates Model project). MJMM acknowledges the Netherlands Research Centre for Integrated Solid Earth Sciences (ISES) and the Netherlands Organization for Scientific Research (NWO) for financial support. The sampling campaigns in 2002 and 2004 were partly funded by the Middle East Basins Evolution (MEBE) program.
Copyright 2011 Elsevier B.V., All rights reserved.
- 40Ar/39Ar dating
- Arc volcanism
- Black Sea region
- X-ray fluorescence analysis