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

Abstract

NTUA)" has been corrected to "National Technical University of Athens (NTUA)" in the Acknowledgements section and has been added to the Funding Information section.] 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.

Transition From Late‐Miocene Syn‐Orogenic Extension to Plio‐Pleistocene Corinth Rifting in the Southern Hellenides, Northern Peloponnese, Greece

“…Although the timing of exhumation of the HP-LT PQ Unit is well constrained in the southern Peloponnese by Ar/Ar cooling ages on phengite (26-16 Ma;Jolivet, Trotet, et al, 2010) and zircon fission track ages (14-10 Ma; Marsellos et al, 2010), the timing of PQ Unit exhumation in the Northern Peloponnese is poorly dated. Recent apatite-He data on the Pindos flysch within the Hellenides fold and thrust belt document a phase of uplift between 14 and 9 Ma, at Mount Erymanthos, west of the study area (Athanassas et al, 2021) (Figure 1). Today the PQ Unit is exposed in a series of NNW-SSE-aligned metamorphic windows that can be traced southward across the Peloponnese and eastward into Crete.…”

“…The second stage of exhumation of the PQ Unit can be explained by underplating and duplexing at depth within the subduction prism (Figure 14) (Athanassas et al, 2021;Jolivet et al, 1994;Marsellos et al, 2010;Menant et al, 2019Menant et al, , 2021Ring et al, 2022). Antiformal stacking of mid-upper crustal imbricates of the Apulian margin triggers vertical tectonic uplift within the supra subduction prism (Jamieson & Beaumont, 1988, 1989Platt, 1986).…”

“…Ring et al (2022) date a late extensional phase as younger than 12-11 Ma in Crete, and Grasemann et al (2019) have demonstrated that the PQ Unit in central Crete was exhumed above the brittleductile transition at 15 Ma. Its timing in the Northern Peloponnese is so far unconstrained, but is likely to have started later, during the Late Miocene (Athanassas et al, 2021). Further, low temperature thermochronological analyses are needed in the Northern Peloponnese to constrain this exhumation history.…”