The tectonics of the Strandja Massif: late-Variscan and mid-Mesozoic deformation and metamorphism in the northern Aegean

Abstract

The Strandja Massif is a mid-Mesozoic orogenic belt in the Balkans build on a late-Variscan basement of gneisses, migmatites and granites. New single-zircon evaporation ages from the gneisses and granites indicate that the high-grade metamorphism and plutonism is Early Permian in age (~271 Ma). The late-Variscan basement was unconformably overlain by a continental to shallow marine sequence of Early Triassic±Mid-Jurassic age. During the Late Jurassic±Early Cretaceous (Oxfordian±Barremian) the lower Mesozoic cover and the basement were penetratively deformed and regionally metamorphosed in greenschist facies possibly due to a continental collision. An Rb±Sr biotite whole-rock age from a metagranite dates the regional metamorphism as Late Jurassic (155 Ma). Deformation involved north-vergent thrust imbrication of the basement and the emplacement of allochthonous deep marine Triassic series over the Jurassic metasediments. The metamorphic rocks of the Strandja Massif are unconformably overlain by the Cenomanian shallow marine sandstones. During the Senonian, the northern half of the Strandja Massif formed a basement to an intra-arc basin and to a magmatic arc generated above the northward-subducting Tethyan oceanic lithosphere.The Srednogorie arc closed during the early Tertiary through renewed northward thrusting of the Strandja Massif.

Analysis of Secular Ground Motions in Istanbul from a Long-Term InSAR Time-Series (1992–2017)

“…These units are covered by the Eocene sedimentary sequence of the Thrace basin [36]. The Paleozoic metamorphic basement of the study area consists in the east in a thick turbiditic sandstone-shale sequence of the Carboniferous age, while the Eocene cover is made of limestone, marl, and claystone units, which are transgressive on Çatalca metamorphic units in the west (Figure 2).…”

Petrostratigraphic evolution of the Thrace Basin (Bulgaria, Greece, Turkey) within the context of Eocene-Oligocene post-collisional evolution of the Vardar-İzmir-Ankara suture zone

“…The Vardarİzmir-Ankara subduction/accretion wedge associated with the closure of a branch of the Neotethys and the more northern Biga subduction/accretion wedge (Çetmi mélange) -whether or not associated with the westward continuation of the Intra-Pontide suture (Okay, Satır, Tüysüz, Akyüz, & Chen, 2001;Okay et al, 2008;Okay & Tüysüz, 1999) -are the obvious source-area candidates for the detritus forming the Ypresian-Bartonian succession. An important southern provenance is also shown by palaeocurrent trends and palaeoslope orientation as shown by slump features and olistoliths.…”

Preface

“…This was due to the inspirational leader of the exploration division of the TPAO, the late Ozan Sungurlu, who was deeply interested in the geology of the country. For 10 years Aral spent all his summer months doing geological mapping: two years were spent in the Menderes Massif and the Lycian Nappes (Okay, 1989c(Okay, , 2001, five summer months in northwest Turkey, mainly mapping the Triassic accretionary complexes (the Karakaya Complex) (Okay, Siyako, & Bürkan, 1991;Siyako, Bürkan, & Okay 1989), two seasons in the Strandja Massif in Thrace (Okay, Satır, Tüysüz, Akyüz, & Chen, 2001) and one in the Pulur Massif in the Eastern Pontides (Okay, 1996;Okay, Şahintürk, & Yakar, 1997). While mapping in north-west Turkey, Aral recognised that Mesozoic sedimentary rock assemblages between İzmir and Balıkesir, which were regarded as part of the Pontides, had in fact Tauride affinities.…”