Paleogeographic position of the central Dodecanese Islands, southeastern Greece: The push-pull of Pelagonia

Abstract

The paleogeographic position of the central Dodecanese Islands at the transition between the Aegean and Anatolian plates plays a considerable role in understanding the link between both geologically unique domains. In this study, we investigate the tectonic history of the central Dodecanese Islands and the general correlation with the Aegean and western Anatolian and focus on the poorly studied islands of Kalymnos and Telendos. Three different major tectonic units were mapped on both islands from bottom to top: (1) The Kefala Unit consists of late Paleozoic, fossil-rich limestones, which have been deformed into a SE-vergent fold-and-thrust belt sealed by an up to 200-m-thick wildflysch-type olistostrome with marble and ultramafic blocks on a scale of tens of meters. (2) The Marina Basement Unit consists of a Variscan amphibolite facies basement with garnet mica schists, quartzites, and amphibolites. (3) Verrucano-type formation violet shales and Mesozoic unmetamorphosed limestones form the Marina Cover Unit. Correlation of these units with other units in the Aegean suggests that Kalymnos is paleogeographically located at the southern margin of the Pelagonian domain, and therefore it was in a structurally upper tectonic position during the Paleogene Alpine orogeny. New white mica 40Ar/39Ar ages confirm the Carboniferous deformation of the Marina Basement Unit followed by a weak Triassic thermal event. Single-grain white mica 40Ar/39Ar ages from pressure solution cleavage of the newly defined Telendos Thrust suggest that the Marina Basement Unit was thrusted toward the north on top of the Kefala Unit in the Paleocene. Located at a tectonically upper position, the units exposed in the central Dodecanese escaped subduction and the syn-orogenic, high-pressure metamorphism. However, these units were affected by post-orogenic extension, and the contact between the Marina Basement Unit and the non-metamorphic Marina Cover Unit has been reactivated by the cataclastic top-to-SSW, low-angle Kalymnos Detachment. Zircon (U-Th)/He ages from the Kefala and Marina Basement Units are ca. 30 Ma, which indicates that exhumation and cooling below the Kalymnos Detachment started in the Oligocene. Conjugate brittle high-angle normal fault systems, which resulted in the formation of four major WNW-ESE−trending graben systems on Kalymnos, localized mainly in the Marina Cover Unit and probably rooted in the mechanically linked Kalymnos Detachment. Since Oligo-Miocene deformation in the northern Dodecanese records top-to-NNE extension and the Kalymnos Detachment accommodated top-to-SSW extension, we suggest that back-arc extension in the whole Aegean realm and transition to the Anatolian plate is bivergent.

Antimony’s Significance as a Critical Metal: The Global Perspective and the Greek Deposits

“…The Hellenic hinterland belongs to the Cimmerian orogenic belt, formed in pre-late Jurassic times as a result of the collision between the northward-drifted Cimmerian continental fragments detached from Gondwana and Eurasia [38][39][40][41][42][43][44]. Compression of the Alpine orogenesis, which resulted in the westward stacking of the Hellenides, was followed by the late Eocene-lower Oligocene extension in northern Greece and later on in the central Aegean due to slab rollback and the retreat of the Hellenic Arc (also known as Hellenic Subduction Zone) resulting in the formation of upper-plate detachment faults and the exhumation of metamorphic core complexes (e.g., [45][46][47][48][49][50][51][52][53][54][55][56][57][58]). Various subsequent deformation stages are proposed, e.g., [59][60][61][62][63] until the lower-middle Pleistocene, which marks the beginning of the present-day stress field characterized by extension in most of the central northern Aegean, with the interference of the transcurrent North Anatolian Fault Zone's (NAFZ) shear in the north Aegean Sea and its two regional tectonic structures, i.e., the North Aegean Trough (NAT) and the North Aegean Basin (NAB) (e.g., [41,[64][65][66][67][68][69][70][71]).…”

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

“…During the Late Oligocene and Early Miocene, the upper plate was affected by compression to form the Hellenides thrust belt followed by widespread extension associated with the exhumation of continental metamorphic units below low‐angle detachments that accommodate high displacements due to the rapid southward retreat of the subducting slab (Jolivet & Brun, 2010; Jolivet, Lecomte, et al., 2010; Ring et al., 2010). In this retreating subduction system, the Hellenides thrust belt of the Peloponnese, becomes diachronously overprinted by Oligocene to Miocene extension (Burchfiel et al., 2018; Grasemann et al., 2021; Jolivet & Brun, 2010; Jolivet, Labrousse, et al., 2010; Jolivet, Trotet, et al., 2010; Papanikolaou & Royden, 2007; Skourtsos & Lekkas, 2011; Skourtsos et al., 2012; Tirel et al., 2013).…”

Nappe Imbrication Within the Phyllite‐Quartzite Unit of West Crete: Implications for Sustained High‐Pressure Metamorphism in the Hellenide Subduction Orogen, Greece

“…The age of the high-P overprint is not known but critical for tectonically interpreting high-P metamorphism of continental crust in the Hellenic subduction zone. Recent work by Grasemann et al (2021) on non-high-P rocks of the Pelagonian Unit on nearby Kalymnos Island suggested a first deformation event in the Paleocene. High-P metamorphism at the base of the Afyon Zone in nearby southwestern Turkey, which has an equivalent tectonic position to the Pelagonian Zone, is 70-62 Ma old (Pourteau et al, 2013;Ring & Layer, 2003).…”