Rapid Late Eocene Exhumation of the Sivas Basin (Central Anatolia) Driven by Initial Arabia‐Eurasia Collision

Abstract

Continental collisions exert a profound influence on the configuration and evolution of orogenic systems. The effects of Arabia-Eurasia collision on the geodynamics of the eastern Mediterranean are difficult to unravel, however, because the timing of initial collision (i.e., intercontinental contact) remains controversial. We present the first detrital and bedrock apatite fission track and (U-Th-Sm)/He thermochronology, and detrital zircon U-Pb constraints from the Sivas Basin and eastern Taurides in central Anatolia (Turkey), which provide a detailed record of Cenozoic orogenesis in the hinterland of the Arabia-Eurasia collision zone. Our results indicate rapid middle Eocene burial followed by shortening, rapid cooling (up to~25-45°C/myr), and initiation of the southern Sivas fold-thrust belt (SSFTB) during the late Eocene (~40-34 Ma), consistent with evidence of a coeval basin-wide unconformity. We interpret that rapid late Eocene cooling of the SSFTB reflects exhumation driven by the northward propagation of retroforeland contraction into the Sivas Basin from the middle to late Eocene, and we propose that these events were due to initial soft collision of the thinned Arabian passive margin by~45 Ma. This timing of the inception of collision is supported by a regional compilation of apatite fission track data that indicates rapid cooling and hinterland exhumation throughout central and eastern Anatolia from~45 to 20 Ma, which was synchronous with a widespread magmatic lull from~40 to 20 Ma. The data presented here are compatible with a widely accepted transition to more mature or hard collision at~20 Ma, probably related to the arrival of thick Arabian crust along the Bitlis suture zone. Plain Language SummaryThe continents of Arabia and Eurasia (Europe and Asia) comprise two separate tectonic plates that are currently colliding with each other. We are uncertain when collision started, which makes it difficult to understand how the collision may have triggered other tectonic changes throughout the region. We investigated the onset of collision by collecting rock samples near the boundary between these continents in central Turkey and determining how their temperature has changed through time (thermochronology). Our analyses tell us the rocks cooled down very quickly~40 million years ago, from temperatures greater than~120°C (i.e., several kilometers deep in the Earth) to much lower temperatures similar to Earth's surface. We infer that rapid cooling was due to the onset of tectonic activity and the creation of a mountain chain with high rates of erosion that removed overlying rocks to bring these samples closer to Earth's surface. These new results agree well with several similar studies that show that rock cooling also occurred at the same time throughout the entire region. We conclude that rock cooling was caused by tectonic uplift and erosion triggered by initial collision of the thinned front of the Arabia plate with Turkeỹ 45 million years ago.

Melt equilibration depths as sensors of lithospheric thickness during Eurasia-Arabia collision and the uplift of the Anatolian Plateau

“…Early to middle Miocene foundering of the Bitlis slab could have simultaneously led to extension in the ETK blocks and mantle melting, yet limited the extent of crustal uplift (Göğüş, 2015). Associated lavas investigated here largely occur in basins containing terrestrial sedimentary units; extensional and contractional tectonic settings for these have both been proposed (summarized by Darin et al, 2018). Deposition near sea level is indicated by the local presence of Langhian Stage marine deposits (Poisson et al, 2016), and by the oxygen isotope signatures of lacustrine sediments interbedded with the Gürün basalts (Meijers et al, 2018a).…”

The Pre‐Obduction to Post‐Obduction Evolution of the Sivas Ophiolite (Turkey) and Implications for the Precollisional History of Eastern Anatolia

“…The late Eocene period corresponds to a large‐scale regional inversion and emersion (Figure e), documented both in the Hekimhan and Darende Basins (Booth et al, ; Booth et al, ), as well as in the Sivas Basin (Legeay, ; Pichat, ). This compressional episode is probably related to the initial retrowedge of the Southern Neotethys subduction and incipient Arabia‐Tauride collision (e.g., Darin et al, ; Legeay, ), which was generally assumed to occur during Oligo‐Miocene time (e.g.Dhont et al, , Gürer & van Hinsbergen, ). The progressive isolation of the Sivas Basin during early to middle Eocene conducted to deposition of a thick evaporite layer dated as 37 Ma (Pichat, ).…”

“…During late Eocene to Miocene, the Tauride recorded a compressional stage that propagated from south to north, caused by closure of southern Neotethys and Arabia‐Eastern Tauride collision. This stage is highlighted in Taurides by north verging thrusts representing the retroforeland of this collisional zone (e.g.Darin et al, , Kaymakcı et al, ).…”

Structure and kinematic evolution of the Southern Sivas Fold-Thrust Belt, Sivas Basin, Central Anatolia, Turkey

“…The objectives of this paper are to characterize the structural architecture, kinematic evolution, and active deformation of the western and central sectors of the SSFTB (Figure 1). Our interpretations are principally based on new detailed geologic mapping, structural analyses of bedding attitudes and fault kinematics, and seismotectonic data along the western and central segments of the SSFTB (Figure 2), which are integrated with insights from recent studies of the stratigraphy, geochronology, and thermochronology of the Sivas Basin (Darin et al, 2018;Schleiffarth et al, 2018;Darin, 2019;Legeay et al, 2019aLegeay et al, , 2019b.…”

“…However, there is still significant uncertainty in the tectonic settings of many of these basins (Görür et al, 1998;Gürer and Aldanmaz, 2002;Yılmaz and Yılmaz, 2019). Moreover, the timing and mechanism(s) responsible for widespread deformation, particularly in Central and Eastern Anatolia, are debated and not well understood (e.g., Dirik et al, 1999;Clark and Robertson, 2002;Yılmaz andYılmaz, 2006, 2019;Kaymakci et al, 2010;Okay et al, 2010;Ballato et al, 2018;Darin et al, 2018). Many key aspects of the structural evolution of the Anatolian basins remain unresolved, such as the timing and magnitude of upper plate shortening, the timing of Arabia-Eurasia collision and the switch to tectonic escape, the detailed structural geology of escape, and the magnitude and distribution of intraplate neotectonic strain within the Anatolian microplate, such as that associated with the Central Anatolian fault zone (CAFZ).…”