Reconstructing the southern Pelagonian domain in the Aegean Sea: Insights from U-Pb detrital zircon analysis, lithostratigraphic and structural study, and zircon (U-Th)/He thermochronology on Amorgos Island (SE Cyclades, Greece) Sofia Laskari a,⇑ , Konstantinos Soukis a , Daniel F. Stockli b , Stylianos Lozios a , Alexandra Zambetakis-Lekkas a a Faculty of Geology and Geoenvironment, National and Kapodistrian University of Athens, Greece b Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, USA article info Article history: Received 19 August 2021 Revised 19 January 2022 Accepted 18 February 2022 Available online 22 February 2022 Handling Editor: A. Festa Keywords: Amorgos Unit detrital zircon U-Pb (U-Th)/He thermochronology Retro-wedge Backthrusting Pelagonian domain abstract In the Attic-Cycladic Crystalline Complex (Aegean Sea, Greece), following early syn-convergence exhuma- tion processes, the extensional tectonics resulted in the extreme denudation of the upper plate, preserved today in a few places. The Cycladic Blueschist Unit (CBU) and the underlying Cycladic Basement and the Basal Units have been exhumed in the footwall of detachment systems, juxtaposed against the Pelagonian-derived hanging wall fragments. Traditional views accept that Amorgos Unit occupies a struc- turally lower position, correlated to the Basal Unit. This study presents lithostratigraphic and structural data, integrated with detrital zircon MDA, provenance analyses, and (U-Th)/He ages, showing a new investigation of the paleogeographic and structural position of Amorgos in the Cycladic archipelago. The low-grade metamorphosed Amorgos Unit presents a tripartite lithostratigraphy: a basal metacon- glomerate, a middle carbonate sequence with shallow-water to pelagic facies, and an Eocene (meta)fly- sch. An HP/LT metabasite huge block is incorporated within the metaconglomerate either by gravitational movements as an isolated olistolith or tectonic processes as a slice during the early deformation stage. Detrital zircon U-Pb analysis on the meta-siliciclastic deposits revealed that the basal metaconglomerate shows a dominant Ediacaran input with Mid-Permian and Precambrian MDAs for the matrix and the high-grade clasts, respectively. The metaflysch shows Paleozoic affinity (e.g., mainly Pelagonian- sourced) and Triassic-Jurassic MDAs. The deformation history of Amorgos includes an early-stage top- to-NW thrusting in the retro-wedge setting of the Late Eocene–Oligocene subduction zone and a late- stage top-to-SE extensional low- and high-angle normal faulting. Zircon (U-Th)/He ages reveal an Early–Mid Miocene (18–14 Ma) exhumation below  200 °C. Similarities on lithostratigraphy, structural inventory, exhumation history, and structural position of Amorgos Unit with the Santorini Detachment System Pelagonian hanging wall imply their close spatial relationship. From all the above, we propose that Amorgos belongs to the upper plate of the CBU and is paleogeographically located at the southern Pelagonian margin. Ó 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. 1. Introduction In the Early Paleozoic, the opening of the Paleotethys was asso- ciated with the detachment of Gondwana-derived terranes (Hunic terranes), eventually involved in the Variscan orogeny during sub- duction of the Paleotethys. Subduction and accretion lasted up to the Ladinian or Norian, when the collision of the Cimmerian ribbon continent with the southern Eurasian margin signified the final closure of Paleotethys (eo-Cimmerian event, Robertson et al., 1991; Stampfli and Borel 2002; Stampfli et al., 2003; Robertson, 2006; Zulauf et al., 2015, 2018). The diachronous Carboniferous to Triassic closure of Paleotethys resulted in widespread magmatic activity, documented in the pre-Apline basement of Rhodope, Pelagonian, the Cycladic domain, and the External Hellenides (e.g., Crete, Kythira, Peloponnese) (Henjes-Kunst and Kreuzer, 1982; Ring et al., 1999; Vavassis et al., 2000; Keay et al., 2001; Xypolias et al., 2006; Anders et al., 2007; Zulauf et al., 2007; Meinhold et al., 2010). The Paleozoic basement was overlain by Permo-Triassic volcano-clastic sequences, viewed as fore-arc, https://doi.org/10.1016/j.gr.2022.02.007 1751-7311/Ó 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: slaskari@geol.uoa.gr (S. Laskari). Gondwana Research 106 (2022) 329–350 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr