T14 Innovative Techniques and Applications for Detrital Thermo- and Geochronologic Data

Sunday, 31 October 2010
8:00 AM - 12:00 PM
Room 207

DETRITAL (U-TH)/HE THERMOCHRONOMETRIC EVALUATION OF THE PAROS SUPRADETACHMENT BASIN, CENTRAL CYCLADES, GREECE

Paper number: T14-2
Program: Technical Sessions
Time: 8:20 AM – 8:35 AM

Authors

Abstract

We present a new detrital thermochronometric evaluation of sedimentary rocks on the island of Paros, Central Cyclades, Greece, which identifies the existence of a Miocene supradetachment basin and refines the timing of tectonic events in the Aegean region. The Cyclades Islands are situated in an actively extending back-arc in the Aegean Sea. Large-magnitude, NE-SW extension started in Eocene time due to Alpine orogenic collapse and rollback of the African slab. A system of regional scale, low-angle normal faults has extensively reworked the original Alpine nappe stack and exhumed Cordilleran-type metamorphic core complexes, juxtaposing middle to late Cenozoic sedimentary rocks against high-grade metamorphic rocks. The island of Paros exposes an unusually complete sedimentary succession that was initially interpreted as foreland basin-type molasse. However, detrital (U-Th)/He zircon (DZHe) data show that the sedimentary rocks of Paros were deposited in a supradetachment basin and preserve the multi-stage tectono-metamorphic history of the Aegean Sea during Miocene sedimentation.

DZHe data from the basal sedimentary unit have a wide spread in ages from 8 – 121 Ma. These ages reflect long-term, upper-plate sediment recycling during Mesozoic – Cenozoic tectonism in the Aegean region. Corresponding detrital (U-Th)/He apatite ages from the basal unit exhibit well-clustered Miocene ages from 7 – 13 Ma, which indicate rapid extensional exhumation of footwall rocks. DZHe ages from the overlying fanglomerate sequence range from 7 – 113 Ma, but the dominant age population (7 – 13 Ma) is nearly indistinguishable from the ZHe population derived from the Paros footwall (7 – 11 Ma). Some fanglomerate DZHe ages are similar to 40Ar/39Ar cooling ages of footwall clasts, further suggesting very short lag times before deposition. The youngest DZHe ages (7 - 8 Ma) establish the minimum depositional ages and indicate that the entire sedimentary succession developed coevally with Miocene core-complex unroofing. In summary, unreset upper-plate DZHe ages from the Paros supradetachment basin preserve age signals from all major Aegean tectonic episodes: Cretaceous HP-LT metamorphism from 70 – 100 Ma, the Eocene onset of African slab subduction from 35 – 50 Ma, and crustal-scale Miocene extension from 7 – 25 Ma.