A New Geological Map of the Island of Syros (Aegean Sea, Greece) by Mark Keiter,Chris Ballhaus,Frank Tomaschek Summary
The Island of Syros (Cyclades, Greece) is a prime locality for the study of processes active in deep levels of orogens and is world famous for its exceptionally well preserved blueschist- to eclogite-facies lithologies. Syros Island was completely remapped at a scale of 1:25,000. Detailed lithostratigraphical observations and area-wide, closely spaced structural measurements allowed a much more detailed depiction of the highly variable lithological assemblage, as well as of the complex structural evolution. Lithostratigraphical indications, such as the distribution of Mn-mineralization and sequential repetition of characteristic marker successions, suggest that the whole-rock pile of the Cycladic Blueschist Unit on Syros, including meta-ophiolites and metasediments, retains numerous primary depositional features. Magmatic activity in an Upper Cretaceous backarc environment was likely to be contemporaneous with the deposition of the sedimentary protoliths comprising the main lithological succession on Syros. The structural evolution of the Cycladic Blueschist Unit on Syros comprises multiphase isoclinal intrafolial folding and ductile thrusting, regarded as essentially burial related and terminating close to peak metamorphic conditions, either prograde or very early on the retrograde path. Especially in areas where blueschist- to eclogite-facies metamorphism is undisturbed, high-pressure fabrics are well preserved. The retrograde evolution was accompanied by heterogeneously distributed, weakly developed extensional tectonics and episodical, contractional deformation, followed by intense brittle transpressional and transtensional tectonics, disrupting the rock sequence since Miocene to subrecent times.