Walking on the roof of the Cyclades: a field guide to Anafi Island (Cyclades, Greece)

Konstantinos Soukis, Stylianos Lozios, and Panagiotis Voudouris

This paper describes a four-day excursion on Anafi Island (Greece), which is located at the southeast part of the Cyclades. Anafi is one of the few Cycladic islands where the upper plate of the Attic-Cycladic complex and the nappe-stacking edifice that preceded the Oligo-Miocene extension is very well preserved, despite the strong impact of the late Miocene extensional collapse. The nappe stack is formed by a series of thrust sheets which include from bottom to top: a very low-grade to non-metamorphosed parautochthonous flysch of partly Eocene age; greenschist-facies schistose metabasites; massive to platy amphibolites with sparse lenses of metasediments; medium to upper amphibolite facies metasediments and ophiolitic rocks, both intruded by intermediate intrusives; coarse grained-marbles closely associated with mainly felsic intrusive rocks. Mineral composition, geochemical and geochronological data reveal that all the intrusive rocks come from the same magma source and they are associated with a late Cretaceous (~85-80Ma) volcanic arc setting.

The nappe pile is cut by a series of brittle low-angle normal faults with a top to the SSW sense of shear that acted during the late Miocene. A supra-detachment basin is developed where a more than 250m thick sequence comprising mainly clastic sediment was deposited. Early syn-extensional deposits exhibit a strong and complex deformation whereas the upper part is almost undeformed. Late Miocene deformation was accompanied by massive fluid infiltration and ore deposition (silver and iron) along upper structural levels. This was probably related to some deeper (?Late Miocene) intrusion and not with the recent volcanic arc. Mining activity was quite important during the ancient and modern times but ceased before the 2nd world war.

A four-day excursion covers all aspects of the complicated Anafi geology. The first day is concentrated around Chora in order to get a first view of the Anafi lithologies. The second day is focused on the western part of the island where the main detachment and supra-detachment deposits can be observed. The third day follows the southeastern coastline all the way to Kalamos hill and the main subject is thrusts and low-angle normal faults. Finally, the fourth day follows the road to the north with main focus on the granitoid rocks, the mining sites around Vigla hill and the Theologos beds.

Open source: