From obduction to continental collision: new data from Central Greece

Abstract

The aim of this paper is to contribute to deciphering the evolutionary history of the Hellenides by the study of a large sector of the chain located between the front of the ophiolitic units and the external zones classically attributed to the continental margin of Adria. In particular, the tectonic units located in Boeotia – a key area located in Central Greece at the boundary between the Internal and External Hellenides – were studied from structural, stratigraphic and biostratigraphic points of view. Addressing the main debated aspects concerning the origin of the ophiolite nappe(s), the tectonic evolution of the Hellenic orogen was revised with a particular emphasis on the period between obduction and continental collision. New findings were compared with consolidated data concerning the main metamorphic events recorded in the more Internal Hellenides, geochemistry and age of the ophiolites and main stratigraphic constraints obtained in other sectors of the belt. Finally, a new reconstruction of the tectonic evolution of this area was introduced and, in the context of the dispute concerning the origin of the ‘ophiolitic belts’ as a possible record of multiple oceanic basins, we put forward for consideration a ‘single ocean’ tectonic model spanning from Triassic up to Tertiary times, and valid for the whole Hellenic–Albanian sector.

Deciphering the geodynamic evolution of the Dinaric orogen through the study of the ‘overstepping’ Cretaceous successions

“…Along the Dinaric-Hellenic chain, the widespread Lower to Upper Cretaceous sedimentary deposits, comprising clastic sediments to carbonates and shallow-marine to basinal settings, represent the seal of the obduction of the Western Vardar ophiolites above the continental units of Adria (Schmid et al 2008;Chiari et al 2011;Bortolotti et al 2013;Nirta et al 2018). The sedimentation of these deposits is diachronous on both oceanic and continentalderived units giving first-order constraints about the timing of synand post-obduction tectonic events.…”

“…Ophiolite massifs in the Central Dinarides represent dismembered portions of a large ophiolite thrust sheet, associated with an underlying tectono-sedimentary mélange, that was obducted onto the eastern margin of the Adriatic Plate at the Jurassic-Cretaceous transition (Bernoulli & Laubscher, 1972;Schmid et al 2008;Chiari et al 2011;Ferrière et al 2012;Nirta et al 2018). Today, these ophiolite massifs are arranged along two subparallel, meridian-trending belts extending from Greece to the Pannonian Basin: the Eastern Vardar ophiolites (i.e.…”

“…In the internal (eastern) part of the Dinaric-Hellenic orogenic system, the units deformed during the Late Jurassic -Early Cretaceous tectonic phase are unconformably overlain by the widespread Cretaceous transgression successions (Radoičić, 1995;Photiades et al 2007;Fazzuoli et al 2008). These sediments are known throughout the entire Dinaric-Hellenic orogen alternatively as 'overstepping sediments', 'Gosau-type deposits', 'deposits of the Cretaceous transgression', 'post-obduction sedimentary cover' and the 'Mesoautochthonous Complex' (Jacobshagen, 1986;Willingshofer et al 1999;Hrvatović, 2006;Photiades et al 2007;Fazzuoli et al 2008;Schmid et al 2008;Schuller et al 2009;Nirta et al 2018). They are made up of terrestrial, transitional and shallow-marine coarse-grained clastic sedimentary rocks and of marine fine-grained clastic sediments and carbonates.…”

“…During the obduction, the ophiolites and mélange were partly located in shallow-marine environments and formed the substratum for isolated carbonate platforms that underwent subsequent rapid dismantling under an active tectonic regime (Fig. 15a) (Schlagintweit et al 2012;Nirta et al 2018). Carbonate fragments with neritic faunas of Tithonian-Berriasian age characterize the basal clastic member of the Pogari Fm (Jovanović, 1961;Blanchet et al 1970) (Fig.…”

“…The inner part of the obduction-related nappe stack was widely emergent during Early Cretaceous time, as testified by the widespread laterite deposits on top of the ophiolites (Photiades et al 2007;Nirta et al 2018). The serpentinites of the Zlatibor Massif suffered intense erosion in an arid climate, as also testified by the metre-thick silcrete duricrusts at the base of the Mokra Gora succession (Bortolotti et al 1971).…”