Don't leave me hanging: Where is the hanging wall in the western Cyclades (Greece)?

Miocene crustal extension in the Aegean region formed major low-angle detachment systems, typically with the Cycladic Blueschist Unit (CBU) in the footwall and the Pelagonian Unit (PU) and ophiolitic remnants in the hanging wall. Although the CBU footwall is well-documented, data regarding the PU hanging wall of the West Cycladic Detachment System (WCDS) is limited due to erosion. This study presents new geological and geochronological data from two previously unexplored uninhabited islands, Makronisos and Agios Georgios, to better define the location and character of the hanging wall of the WCDS. Makronisos is structurally part of the footwall of the WCDS and belongs to the Lower Cycladic Nappe of the CBU. It displays intense top-to-SSW shear strain localized within marble ultramylonites. New 40Ar/39Ar white mica dating confirms a Miocene deformation history, which is consistent with the exhumation of the CBU along the WCDS. In contrast, Agios Georgios represents a hanging wall remnant. It consists of granitoid orthogneiss, amphibolites, and metasediments that underwent upper greenschist to amphibolite facies metamorphism. U-Pb zircon dating indicates a Late Triassic magmatic protolith age, whereas 40Ar/39Ar and (U-Th)/He data reveal a Late Cretaceous-Paleogene metamorphic overprint and cooling to shallow crustal levels by c. 20 Ma. Agios Georgios correlates with the Vari Unit on Syros, extending the known range of Pelagonian metamorphic rocks further west. Comparing the Miocene cooling of the CBU footwall with the Paleogene cooling of the PU hanging wall suggests a total displacement of 20-30 km along the WCDS between 20 and 8 Ma, indicating a slip rate of 1.5-2.5 mm/yr.