Abstract:

The Aegean region of Greece hosts a series of crustal-scale extensional detachment systems that have accommodated the southward retreating Hellenic subduction zone. Extension has overprinted and dissected the Alpine nappe pile and locally exhumed Cordilleran-type metamorphic core complexes. On the island of Paros, a low-angle extensional detachment fault separates metamorphic footwall rocks from an unmetamorphosed sedimentary succession of the hanging wall. Basement orthogneisses were extensionally sheared in the footwall of the detachment until after 16. Ma (zircon U-Pb age of a slightly deformed granite), but pervasive ductile deformation had ceased by 7. Ma (zircon U-Pb age of an undeformed rhyolite dike that intrudes gneisses). Apatite and zircon (U-Th)/He ages from the gneisses confirm a period of cooling at rates >. 100. °C/Ma from 16 to 7. Ma. In the upper-plate, the basal sedimentary unit yields reset detrital apatite (U-Th)/He (DAHe) ages from 17 to 7. Ma and detrital zircon (U-Th)/He (DZHe) ages ranging from 270 to 18. Ma. DAHe ages from the stratigraphically higher fanglomerate units are reset to 10-7. Ma. The DZHe data have a primary thermal signature of 12-7. Ma, but preserve ages up to 113. Ma. The uppermost conglomerates exhibit completely reset DAHe ages of 15-9. Ma and reset DZHe ages from 10 to 8. Ma, with DZHe ages up to 104. Ma. Reset DAHe ages indicate late exposure of the footwall and constrain the depositional age of most sedimentary rocks on Paros to be from 14 to 7. Ma. Unreset DZHe ages preserve thermal signatures from the major Mesozoic-Tertiary tectonic events in the Aegean Region: [1] Cretaceous Pelagonian-type metamorphism; [2] Eocene peak HP metamorphism; and [3] Miocene Barrovian overprinting. Preservation of these signatures indicates long-term upper-plate recycling prior to syn-extensional deposition. The Paros supradetachment basin represents a classic inverted unroofing sequence deposited during progressive core complex exhumation in the Middle to Late Miocene. © 2012 Elsevier B.V.