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The Cycladic Basement (CB) and the overlying Cycladic Blueschist Unit (CBU) are part of the Paleogene Cycladic subduction complex exposed in Miocene metamorphic core complexes in the distended back‐arc of the retreating Hellenic subduction zone of the southern Aegean. While the Cenozoic tectono‐metamorphic evolutions of the CB and the CBU have been the foci of numerous studies, this study presents new laser ablation inductively coupled plasma mass spectrometry bedrock and detrital zircon (DZ) U‐Pb ages that place robust constraints on the presubduction tectonic, magmatic, and paleogeographic evolution of the CB. Zircon U‐Pb ages of crystalline CB are ~306‐330 Ma, demonstrating local plutonism associated with regional voluminous, protracted Carboniferous magmatism related to Paleo‐Tethys subduction. The plutons intruded the CB metasedimentary host‐rock sequence, characterized by distinct Gondwanan DZ U‐Pb provenance, Neoproterozoic to early Paleozoic maximum depositional ages, and synmagmatic, contact metamorphic zircon rims (~300‐330 Ma). DZ U‐Pb dating revealed postmagmatic Permian metasedimentary rocks (~270‐295 Ma) that unconformably overlie the CB and have unimodal DZ spectra that indicate exhumation of the CB prior to Permian deposition within extensional basins, as well as mark the onset of CBU deposition prior to formation of the Pindos rift domain. These U‐Pb results clarify the late Paleozoic‐early Mesozoic evolution of the CB as a peri‐Gondwanan terrane composed of Neoproterozoic and early Paleozoic metasedimentary rocks, intruded by voluminous Carboniferous arc magmatism, and exhumed in the Permian, prior to Triassic rifting and CBU deposition. Additionally, these data provide a chronostratigraphic framework and illuminate subduction‐related juxtaposition within the CB metasedimentary sequence.

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Sikinos and Ios Islands, located in the Southern Cyclades, represent part of a Cenozoic metamorphic core complex system that exposes subduction-related metamorphic rocks in the highly extended back-arc region of the Hellenic subduction zone. These exhumed HP-LT metamorphic units are composed of Mesozoic metasedimentary rocks of the Cycladic Blueschist Unit (CBU) and the Paleozoic Cycladic Basement (CB). The magmatic and stratigraphic evolution of these units, as well as the nature of the contact between the CBU and CB, have remained poorly understood. We used zircon U-Pb dating to determine crystallization ages of the CB on Sikinos and the maximum deposition ages and detrital provenance of the metasedimentary units to reconstruct the Mesozoic to early Cenozoic stratigraphic and tectonic evolution of the CBU on both islands. The results reveal that the CB in Sikinos is composed of Cambrian-Silurian metasedimentary rocks intruded by Carboniferous granites and is overlain by metasedimentary rocks of the CBU with depositional ages spanning from Permo-Triassic to Late Cretaceous. The provenance data from the CBU records a long-lived tectonic evolution from Paleo-Tethys subduction and rifting, to passive margin formation, and to subduction of the Neo-Tethyan Pindos basin. The continuous stratigraphic record and provenance evolution from the CB into the CBU imply a para-autochthonous relationship. On NE Sikinos and Ios, stratigraphic constraints suggest older-over-younger relationships along cryptic-thrusts, supporting premetamorphic or synmetamorphic structural repetition of the CBU by imbrication, likely during subduction underplating.

We present field and geochronologic evidence for a Miocene top-to-SSE detachment system on Santorini, which exhumed the Cycladic Blueschist Unit (CBU) below a package of low-grade Upper Triassic marbles that contain well-preserved Megalodon fossils forming a syncline with metaflysch in the core. White mica bundles from the mylonitic foliation in the CBU yield 40 Ar/ 39 Ar dates of 25-19 Ma and zircon (U-Th)/He dates are 11-8 Ma. A weakly foliated granitic intrusion that crosscuts the CBU is 8.5 Ma based on zircon U-Pb geochronology. Detrital white mica from the metaflysch yields Jurassic to early Palaeogene single grain 40 Ar/ 39 Ar dates, with a dominant Palaeocene signature. Zircon (U-Th)/He dating similarly reveals dispersed ages between 36 and 15 Ma suggesting Miocene metamorphic temperatures were insufficient (<200°C) to completely reset all of the zircon cooling ages. The low-grade rocks of the hangingwall above the newly discovered Miocene low-angle Santorini Detachment System most likely belong to the Pelagonian zone with a Triassic carbonate platform discordantly transgressed by an Eocene flysch deposit.

This study presents detrital zircon U‐Pb analyses of 23 samples of the Cycladic Blueschist Unit (CBU) from Kea, Kythnos, and Serifos islands, as well as the Lavrion Peninsula of SE Attica. The maximum depositional ages (MDA) and age distributions of detrital zircon U‐Pb dates are used to correlate metasediments between the islands considered herein and infer their provenance. Two distinct detrital zircon U‐Pb age distributions are found in CBU metasediments: “Proterozoic,” comprised of >40% Neoproterozoic zircons with Triassic‐Early Jurassic maximum depositional ages and “Paleozoic,” containing >30% Paleozoic zircons and yielding Late Jurassic‐Cretaceous MDAs. Proterozoic affinity metasediments are rift margin deposits derived from the northern Gondwanan margin. Paleozoic metasediments are flysch sediments most probably sourced from the Internal Hellenides. This metamorphosed flysch forms a distinct marker horizon found in a similar structural position in Lavrion, Kythnos, and Serifos. Based on lithologic correlation, sediment provenance, and MDA estimates, the CBU of Kythnos is correlative to the Lavrion Schists of Attica. On the islands of Serifos and Kythnos and within the Lavrion Schists only young‐on‐old relationships exist between rocks based on MDA estimates.

Exhumed high‐pressure/low‐temperature (HP/LT) metamorphic rocks provide insights into deep (∼20–70 km) subduction interface dynamics. On Syros Island (Cyclades, Greece), the Cycladic Blueschist Unit preserves blueschist‐to‐eclogite facies oceanic‐ and continental‐affinity rocks that record the structural and thermal evolution linked to Eocene subduction. Despite decades of research, the metamorphic and deformation history (P‐T‐D) and timing of subduction and exhumation are matters of ongoing discussion. We suggest that Syros comprises three coherent tectonic slices and that each slice underwent subduction, underplating, and syn‐subduction return flow along similar P‐T trajectories, but at progressively younger times. Subduction and exhumation are distinguished by lineations and ductile fold axis orientations, and are kinematically consistent with previous studies that document top‐to‐the‐S‐SW shear (prograde‐to‐peak subduction), top‐to‐the‐NE shear (blueschist facies exhumation), and then E‐W coaxial stretching (greenschist facies exhumation). Amphibole zonations record cooling during decompression, indicating return flow above a cold slab. Multi‐mineral Rb‐Sr isochrons and compiled metamorphic geochronology show that the three slices record distinct stages of peak subduction (53–52, ∼50, and 45 Ma) that young with structural depth. Retrograde blueschist and greenschist facies fabrics span ∼50–40 and ∼43–20 Ma, respectively, and also young with structural depth. Synthesized data sets support a revised tectonic framework for Syros, involving subduction of structurally distinct coherent slices and simultaneous return flow of previously accreted tectonic slices in the subduction channel shear zone. Distributed, ductile, dominantly coaxial return flow in an Eocene‐Oligocene subduction channel proceeded at rates of ∼1.5–5 mm/yr and accommodated ∼80% of the total exhumation of this HP/LT complex.

The geological, geomorphic conditions of a mountainous environment along with precipitation and human activities influence landslide occurrences. In many cases, their relation to landslide events is not well defined. The scope of the present study is to identify the influence of physical and anthropogenic factors in landslide activity. The study area is a mountainous part of the northern Peloponnesus in southern Greece. The existing landslides, lithology, slope angle, rainfall, two types of road network (highway-provincial roads and rural roads) along with land use of the study area are taken into consideration. Each physical and anthropogenic factor is further divided into sub-categories. Statistical analysis of landslide frequency and density, as well as frequency and density ratios, are applied and combined with a geographic information system (GIS) to evaluate the collected data and determine the relationship between physical and anthropogenic factors and landslide activity. The results prove that Plio-Pleistocene fine-grained sediments and flysch, relatively steep slopes (15 • -30 • ) and a rise in the amount of rainfall increase landslide frequency and density. Additionally, Plio-Pleistocene fine-grained sediments and flysch, as well as schist chert formations, moderate (5 • -15 • ) and relatively steep slopes (15 • -30 • ), along with the amount of rainfall of >700 mm are strongly associated with landslide occurrences. The frequency and magnitude of landslides increase in close proximity to roads. Their maximum values are observed within the 50 m buffer zone. This corresponds to a 100 m wide zone along with any type of road corridors, increasing landslide occurrences. In addition, a buffer zone of 75 m or 150 m wide zone along highway and provincial roads, as well as a buffer zone of 100 m or 200 m wide zones along rural roads, are strongly correlated with landslide events. The extensive cultivated land of the study area is strongly related to landslide activity. By contrast, urban areas are poorly related to landslides, because most of them are located in the northern coastal part of the study area where landslides are limited. The results provide information on physical and anthropogenic factors characterizing landslide events in the study area. The applied methodology rapidly estimates areas prone to landslides and it may be utilized for landslide hazard assessment mapping as well as for new and existing land use planning projects.