Thermotectonic constraints on the geodynamic evolution of the Pindos fold‐and‐thrust‐belt by low‐temperature (U–Th)/He thermochronometry

• Published in: Geological journal (Chichester, England) Vol. 56; no. 10; pp. 5311 - 5328
• Main Authors: Athanassas, Constantin D., Papanikolaou, Dimitrios I., Falkowski, Sarah, Papanikolaou, Ioannis D., Ntokos, Dimitrios
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.10.2021; Wiley Subscription Services, Inc
• Subjects: Age; Apatite; Bedrock; Belts; Cenozoic; Cooling; crustal cooling; Echoes; Evolution; exhumation; Heating; Hellenic arc; Isotopes; Minerals; Miocene; orogenic uplift; Orogeny; Peloponnese; Segments; Temperature; Thermal analysis; thermal modelling; Thickening; Uplift; Zircon
• ISSN: 0072-1050; 1099-1034
• DOI: 10.1002/gj.4240

This study presents new thermochronometric data to constrain the cooling history of the Pindos fold‐and‐thrust‐belt (PFTB) on the NW Peloponnese, and the timing of nappe stacking in the external Hellenides in western Greece. Low‐temperature thermochronology was performed on apatite and zircon minerals extracted from basal exposures of the PFBT in Mt. Erymanthos (NW Peloponnese) using the (U‐Th)/He system. Three bedrock samples collected from a profile across the strike of the PFBT returned thermochronometric ages for the apatite (AHe) between 15 and 9 Ma, while for the zircon (ZHe) the ages are interpreted as unreset (or partially reset). The AHe ages are interpreted as cooling ages related to the Cenozoic geodynamic evolution of the PFTB. Thermal models generated in this research demonstrate two phases of geodynamic evolution of the PFBT during the Cenozoic: an early one associated with the heating of the fold‐and‐thrust belt during 40–20 Ma and a later one associated with fast cooling from 20 Ma onwards. Heating is attributed to the structural thickening of the PFTB while cooling is associated with enhanced uplift and exhumation, which became widespread in Erymanthos by 9 Ma. The initiation of cooling on Mt. Erymanthos echoes the substantial geometric remodelling that underwent the Hellenic arc during the Middle Miocene, associated with slab rollback and arc extension, and is connected to the underplating of the internal segments of the external platform (Gavrovo‐Tripolis unit) by the external metamorphic segments (Mani and Arna units). The current inverse thermal modelling offers the first continuous description of the geodynamic evolution of the most prominent fold‐and‐thrust belt of the Hellenides, from the oceanic stage through basin inversion to uplift and orogen decay. Low‐temperature thermochronology was performed on basal exposures of the Pindos nappe in Mt. Erymanthos (Er), NW Peloponnese, Greece, using the (U–Th)/He system on zircon and apatite. Thermochronometric ages for the apatite range between 15 and 9 Ma. By the Middle‐Late Miocene, the motion of the nappe ceased and became subject to uplift and erosion, resulting in the exhumation of its deeper structural levels. The crustal thickness beneath the Pindos nappe (Pi) was doubled by the duplication of the external carbonate platform after the Mani (Ma) segment underplated the Ionian and the Gavrovo‐Tripolis segments. The Arna unit was tectonically detached from the base of the platform and wedged between the Mani and Gavrovo (Ga)‐Tripolis (Tr) segments.