DETRITAL (U-TH)/HE THERMOCHRONOMETRY IN THE HANGING WALL BASIN OF THE PAROS METAMORPHIC CORE COMPLEX, CENTRAL AEGEAN, GREECE

The Cenozoic tectonic evolution of the central Aegean is dominated by large-magnitude extension and the formation of metamorphic core complexes developed in an intra-arc and back-arc extensional setting. Most of the Cycladic islands expose mainly lower-plate rocks and the pre- and syn-extensional sedimentary upper-plate record is sparsely preserved on a few islands. The island of Paros exposes a stack of upper-plate sediments, originally interpreted as foreland basin deposits, but subsequently reinterpreted as a syn-extensional supradetachment basin. The basin fill, however, most likely records a more complicated tectonic and depositional history as it can be subdivided into a folded, lower turbidite sequence containing Mesozoic limestone olistoliths near its base and a massive conglomeratic upper sequence characterized by lower-plate detritus. This study presents new (U-Th)/He data from both lower plate rocks and upper-plate sediments. The aim is to investigate the exhumation history of the Paros core complex and specifically the depositional environment, depositional age, detrital provenance, and tectonic and thermal evolution of the upper-plate basin fill. Extensive zircon and apatite (U-Th)/He analyses from the lower-plate document uniform rapid footwall exhumation and cooling from >200°C in the Late Miocene (7-9 Ma). Upper-plate detrital (U-Th)/He data show that (1) limestone blocks near the base of the sequence are in fact olistoliths overlying sandstones with younger detrital zircon (U-Th)/He (DZHe) ages; (2) DZHe ages of the turbidite sequence range from 70-20 Ma, consistent with published detrital muscovite ⁴⁰Ar/³⁹Ar ages; (3) DZHe ages from the lower-plate-derived conglomeratic sequence are dominated by Late Miocene DZHe ages, indistinguishable from lower-plate cooling ages, confirming a Late Miocene supradetachment basin environment. The depositional environment for the turbidite sequence remains in question, but the unconformable upper contact and the fundamental changes in clast composition and DZHe ages across this contact suggest a pre-extensional Tertiary origin for the lower basin fill. More multi-mineral (U-Th)/He data are needed to elucidate the provenance and thermal evolution of the sedimentary packages in the upper-plate of the Paros core complex.