Tectonic Evolution of the Izmir Ankara Suture Zone in Northwest Turkey Using Zircon U-Pb Geochronology and Zircon Lu-Hf Isotopic Tracers

Abstract

Detrital zircons from the Late Cretaceous Murdunu-Göynük forearc basin and the Paleogene Saricakaya foreland basin; part of the greater Central Sakarya Basin located along the Sakarya Zone of the Western Pontides were analyzed to better understand the closure history of the Tethyan oceans. In northwest Turkey, the Variscan Orogeny is characterized by abundant 350-300 Ma zircon U-Pb ages and minimally to highly evolved εHf values. In εHf vs. age space no distinct trends are apparent, consistent with a north dipping subduction zone that emplaced plutons into a southward growing, heterogeneous accretionary margin. From 300-250 Ma εHf values trend from highly to minimally evolved, interpreted as crust thinning, a result of slab rollback and rifting of the Intra-Pontide Ocean. The Cimmerian Orogeny is characterized by a decrease in magmatism from 250-230 Ma associated with minimally to moderately evolved εHf evolution, followed by a 230-200 Ma magmatic gap consistent with crustal thickening followed by flat-slab underthrusting of the Karakaya Complex. Zircons with 200-115 Ma U-Pb ages are all but absent, interpreted as a magmatic lull. The Alpine Orogeny in northwest Turkey is characterized by an increase in magmatism from 115-85 Ma, associated with minimally intermediate to moderately evolved εHf evolution of Late Cretaceous Murdunu-Göynük forearc zircons. At 100 Ma, Late Cretaceous zircons only found within Paleogene Saricakaya foreland basin sediments deviate from similar aged εHf evolution in forearc basin sediments and plot in both the juvenile and intermediate domains. Minor zircon U-Pb age peaks and contrasting interbasinal εHf evolution are interpreted to represent onset of Andean-style subduction along the southern margin of the Sakarya Zone at ~115 Ma followed by 100 Ma initiation of intra-oceanic subduction within the İzmir-Ankara Ocean. Epsilon Hf values from zircons with 85-75 Ma U-Pb ages sampled from forearc basin sediments trend from moderately evolved to moderately Table of Contents Introduction……………………………………………………………………………………...1 Regional Geology……………………………………………………………………………….4

Collision Chronology Along the İzmir‐Ankara‐Erzincan Suture Zone: Insights From the Sarıcakaya Basin, Western Anatolia

“…The main depositional environment (DE) is given to the left. To the right of the stratigraphic column, histograms, and kernel density estimates (Botev et al, ) display detrital zircon age distributions from this study and Campbell (). Histograms display all ages in 20‐Myr bins in the right column and only ages <500 Ma in 10‐Myr bins on the left.…”

“…We present the ages of SB volcaniclastic samples in Table and their stratigraphic location in Figure . We also include one volcaniclastic sample from Campbell (). Volcaniclastic layers are massive, gray‐green mudstones predominantly composed of feldspar, which we interpret as weathered pyroclastics (LF3).…”

“…We provide the 2 σ error with and without the 1.3% modelling error (see Text S1 for discussion). 15YP11 is from Campbell (); N 0 is the total number of grains; N is the number of grains used in weighted mean age calculation.…”

“…Within each sample, zircon grains vary from angular to rounded and euhedral to anhedral, and some contain inclusions. The results, plus two detrital samples ( n = 242) from Campbell (), are presented in their stratigraphic position in Figure . The 16SKY04 has a prominent Ypresian peak and minor Jurassic, Triassic, and Carboniferous age peaks.…”

“…Regional geologic map and schematic cross section of the southern Central Sakarya Basin, Sarıcakaya Basin, İzmir‐Ankara‐Erzincan suture zone, and Eskişehir Basin (modified from Aksay et al, ; Duru & Aksay, ; Gedik & Aksay, ; Kasapoğlu et al, ; Şengüler & Izladi, ; Timur & Aksay, ; Turhan, & P. Ustaömer et al, ). İAESZ and Söğüt Thrust detrital zircon sample locations are labeled (including those from Campbell, ); measured sections locations include SB detrital zircon and sandstone petrography samples (M = Mayıslar sections, I = Iğdir sections, K = Kapıkaya sections, and O = Ozanköy sections). The Paleogene volcano‐plutonic unit includes the Nallıhan volcanic rocks and Tavşanlı Zone plutons.…”