Chronology of subduction and collision along the İzmir-Ankara suture in Western Anatolia: records from the Central Sakarya Basin

Abstract

Western Anatolia is a complex assemblage of terranes, including the Sakarya Terrane and the Tauride-Anatolide Platform that collided during the late Cretaceous and Palaeogene (80-25 Ma) after the closure of the Izmir-Ankara Ocean. Determining the precise timing at which this ocean closed is particularly important to test kinematic reconstructions and geodynamic models of the Mediterranean region, and the chronology of suturing and its mechanisms remain controversial. Here, we document the Cretaceous-Eocene sedimentary history of the Central Sakarya Basin, along the northern margin of the Neotethys Ocean, via various approaches including biostratigraphy, geochronology, and sedimentology. Two high-resolution sections from the Central Sakarya Basin show that pelagic carbonate sedimentation shifted to rapid siliciclastic deposition in the early Campanian (~79.6 Ma), interpreted to be a result of the build-up of the accretionary prism at the southern margin of the Sakarya Terrane. Rapid onset of deltaic progradation and an increase in accumulation rates in the late Danian (~61 Ma), as well as a local angular unconformity are attributed to the onset of collision between the Sakarya Terrane and the Tauride-Anatolide Platform. Thus, our results indicate that though deformation of the subduction margin in Western Anatolia started as early as the Campanian, the closure of the İzmir-Ankara Ocean was only achieved by the early Palaeocene.

Major Late Cretaceous Mass Flows in Central Turkey Recording the Disruption of the Mesozoic Continental Margin

“…The Alcı volcaniclastic sequence has a similar age as the widespread Campanian‐Maastrichtian fore‐arc turbidites, the Haymana formation, which crops out in the Haymana and Bağlum regions, and in the central Sakarya Basin (Figures and ; Ünalan et al, ; Özcan & Özkan‐Altıner, ; Ocakoğlu et al, ). To test the correlation of the Alcı and Haymana formations and to establish the age of arc magmatism, we dated detrital zircons from two sandstone samples from the Haymana formation, 20 and 50 km south and southwest of the Alcı region, respectively (Figure ).…”

“…The basement of the Sakarya Zone is mostly made up of Triassic subduction–accretion complexes of deformed turbidites and basalts, called the Karakaya Complex. The Karakaya Complex is unconformably overlain by a 2‐km‐thick Jurassic‐Cretaceous sedimentary and volcanic sequence, which is well exposed in the central Sakarya Basin in northwest Turkey (Figure ; Altıner et al, ; Ocakoğlu et al, ).…”

“…Autochthonous Cenomanian–Turonian sequences are known from the central Sakarya Basin and from the Haymana region (Figure ; Yilmaz, ; Okay & Altıner, ; Ocakoğlu et al, ), where they are represented by a less than 100‐m‐thick sequence of pelagic limestone, marl, and shale.…”

İzmir‐Ankara Suture as a Triassic to Cretaceous Plate Boundary—Data From Central Anatolia

“…The sedimentary sequence of the Central Sakarya Basin crops out in the hangingwall of the Nallıhan‐Sarıcakaya thrust north of Nallıhan (Figures 2 and 4). The stratigraphy of the Central Sakarya Basin is well known and extends from the Early Jurassic to Paleocene (Figure 2, Altıner et al, 1991; Altınlı, 1976; Ocakoğlu et al, 2019; Saner, 1980). It starts with Lower Jurassic conglomerates and sandstones, which rest unconformably over the Upper Karakaya Complex or over the Carboniferous granites.…”

“…The Albian‐Cenomanian is represented by deep marine volcaniclastic sandstones and limestones, which are overlain by Turonian to Santonian pelagic limestones. An abrupt change occurs in the Campanian, when pelagic carbonate sedimentation is succeeded by the deposition of thick clastic turbidites with tuff horizons (Ocakoğlu et al, 2019). The turbidites form a regressive sequence and pass up into Paleocene molassic sandstones and conglomerates (Figure 2).…”