Abstract
Abstract. The Pelagonian zone, situated between the External Hellenides/Cyclades to the west and the Axios/Vardar/Almopias zone (AVAZ) and the Rhodope to the east, was involved in late Early Cretaceous and in Late Cretaceous–Eocene orogenic events whose duration and extent are still controversial. This paper constrains their late thermal imprints. New and previously published zircon (ZFT) and apatite (AFT) fission-track ages show cooling below 240 °C of the metamorphic western AVAZ imbricates between 102 and 93–90 Ma, of northern Pelagonia between 86 and 68 Ma, of the eastern AVAZ at 80 Ma and of the western Rhodope at 72 Ma. At the regional scale, this heterogeneous cooling is coeval with subsidence of Late Cretaceous marine basin(s) that unconformably covered the Early Cretaceous (130–110 Ma) thrust system from 100 Ma. Thrusting resumed at 70 Ma in the AVAZ and migrated across Pelagonia to reach the External Hellenides at 40–38 Ma. Renewed thrusting in Pelagonia is attested at 68 Ma by abrupt and rapid cooling below 240 °C and erosion of the gneissic rocks. ZFT and AFT in western and eastern Pelagonia, respectively, testify at ~40 Ma to the latest thermal imprint related to thrusting. Central-eastern Pelagonia cooled rapidly and uniformly from 240 to 80 °C between 24 and 16 Ma in the footwall of a major extensional fault. Extension started even earlier, at ~33 Ma in the western AVAZ. Post-7 Ma rapid cooling is inferred from inverse modeling of AFT lengths. It occurred while E–W normal faults were cutting Pliocene-to-recent sediment.
Highlights
The NW–SE trending Pelagonian zone in northern Greece (Fig. 1a, Schermer et al, 1990; Kilias et al, 2010; Schenker et al, 2014) is tectonically overlain by imbricates of a Late Triassic–Middle Jurassic passive margin to the northeast (e.g., Bernoulli and Laubscher, 1972)
New and previously published zircon (ZFT) and apatite (AFT) fission-track ages show cooling below 240 ◦C of the metamorphic western Axios/Vardar/Almopias zone (AVAZ) imbricates between 102 and 93–90 Ma, of northern Pelagonia between 86 and 68 Ma, of the eastern AVAZ at 80 Ma and of the western Rhodope at 72 Ma
Our study identified four major cooling events: (i) variable in time and space, post-collisional cooling affecting Pelagonia, AVAZ and western Rhodope from 102 to ca. 68 Ma as shown by ZFT ages and subsidence of marine basins over the Pelagonian and AVAZ units; (ii) fast cooling and erosion at ca. 68 Ma attested by ZFT ages and increased coarse detritus shed from Pelagonia to the western AVAZ basins; (iii) fast cooling below 240 ◦C from 24 to 16 Ma in the footwall of a normal fault in central-eastern Pelagonia; (iv) fast cooling after 7 Ma below ca. 80 ◦C coeval with E–W to NE–SW trending normal fault zones in central-eastern Pelagonia
Summary
The NW–SE trending Pelagonian zone in northern Greece (Fig. 1a, Schermer et al, 1990; Kilias et al, 2010; Schenker et al, 2014) is tectonically overlain by imbricates of a Late Triassic–Middle Jurassic passive margin (the Axios/Vardar/Almopias zone, AVAZ) to the northeast (e.g., Bernoulli and Laubscher, 1972). The Pelagonian zone experienced two thrust events, one during the late Early Cretaceous and the during the Eocene (Godfriaux et al, 1988; Schermer, 1993; Schenker et al, 2014) followed by Miocene extension (e.g., Schermer et al, 1990; Lecassin et al, 2007; Coutand et al, 2014) This history imprinted a complex distribution of low-temperature thermochronometric data, which comprise: zircon fission track (ZFT), zircon (U-Th) / He (ZHe), apatite fission track (AFT) and apatite (U-Th) / He (AHe) (Most, 2003; Vamvaka et al, 2010; Coutand et al, 2014). Integrated into a geological and structural frame, these widely distributed low-temperature
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