Sedimentary Provenance From the Evolving Forearc‐to‐Foreland Central Sakarya Basin, Western Anatolia Reveals Multi‐Phase Intercontinental Collision

• Published in: Geochemistry, geophysics, geosystems : G3 Vol. 23; no. 3
• Main Authors: Mueller, Megan A., Licht, Alexis, Campbell, Clay, Ocakoğlu, Faruk, Akşit, Gui G., Métais, Grégoire, Coster, Pauline M. C., Beard, K. Christopher, Taylor, Michael H.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 01.03.2022; AGU and the Geochemical Society; Wiley
• Subjects: Accretion; Anatolia; Biology; Continents; Cretaceous; Deformation; detrital zircon geochronology; Earth Sciences; Eocene; Evolution; Forearc basins; intercontinental collision; Lithosphere; Mechanics; Neotethys; Passive margins; Petrography; Petrology; Plate tectonics; Sandstone; Sciences of the Universe; Sediment; Sedimentary rocks; Sediments; Subduction; Tectonics; Volcanoes; Zircon; Anatolia
• ISSN: 1525-2027; 1525-2027
• DOI: 10.1029/2021GC010232

Collision between the Pontides and Anatolide‐Tauride Block along the İzmir‐Ankara‐Erzincan suture in Anatolia has been variously estimated from the Late Cretaceous to Eocene. It remains unclear whether this age range results from a protracted, multi‐phase collision or differences between proxies of collision age and/or along strike diachroneity. Here, we leverage the Cretaceous‐Eocene evolution of the forearc‐to‐foreland Central Sakarya Basin system in western Anatolia to determine when and how collision progressed. New detrital zircon (DZ) and sandstone petrography results indicate that the volcanic arc was the main source of sediment to the forearc basin in the Late Cretaceous. The first appearance of Pontide basement‐aged DZs, in concert with exhumation of the accretionary prism and a decrease in regional convergence rates, indicates intercontinental collision initiated no later than 76 Ma. However, this first contractional phase does not produce advanced thick‐skinned deformation and basin partitioning until ca. 54 Ma. We propose three non‐exclusive and widely applicable mechanisms to reconcile the observed ∼20 Myr delay between initial intercontinental collision and thick‐skinned upper plate deformation: slab breakoff, relict basin closure north and south of the İAES, and underthrusting of progressively thicker passive margin lithosphere. These mechanisms highlight the links between upper plate deformation and plate coupling during continental collision. Plain Language Summary Key to understanding the interconnectedness of Earth's systems is unraveling feedbacks between climate, biology, and tectonic plate movements. This can only be resolved within a robust timeframe of tectonic events, including the collision of continents. Yet, the timing of collisions is difficult to determine. We present results from western Turkey where the history of oceanic basin closure and collision from 110 to 40 million years ago (Ma) is preserved in the sedimentary rock record. We identify three phases of oceanic closure (subduction) and continental collision. Subduction was active from at least 110 Ma through 76 Ma when sediment was derived from active volcanoes. At 76 Ma, continental deformation uplifted and eroded older rocks; this is the initial contact between colliding continents. The next phase of collision began at 54 Ma when continental deformation separated the zone of sediment deposition into two basins. The 20‐million‐year collision duration can be explained by three changes to tectonic plate coupling. Together, we conclude that collision age discrepancies are representative of collision mechanics not a function of ill‐fit comparisons between proxies. This long history of collision illuminates how the movement and amalgamation of small continents aided the migration and evolution of species in the Mediterranean. Key Points Multi‐phase intercontinental collision is identified in western Anatolia by sedimentary basin changes Sedimentary provenance change indicate collision was at 76 Ma, but significant thick‐skinned deformation was delayed until 54 Ma The 20 Myr duration of initial collision can be explained by three multi‐stage mechanisms involving changes in plate coupling