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

An edited version of this paper was published by AGU. Copyright 2019 American Geophysical Union.Debate persists concerning the timing and geodynamics of intercontinental collision, style of syncollisional deformation, and development of topography and fold‐and‐thrust belts along the >1,700‐km‐long İzmir‐Ankara‐Erzincan suture zone (İAESZ) in Turkey. Resolving this debate is a necessary precursor to evaluating the integrity of convergent margin models and kinematic, topographic, and biogeographic reconstructions of the Mediterranean domain. Geodynamic models argue either for a synchronous or diachronous collision during either the Late Cretaceous and/or Eocene, followed by Eocene slab breakoff and postcollisional magmatism. We investigate the collision chronology in western Anatolia as recorded in the sedimentary archives of the 90‐km‐long Sarıcakaya Basin perched at shallow structural levels along the İAESZ. Based on new zircon U‐Pb geochronology and depositional environment and sedimentary provenance results, we demonstrate that the Sarıcakaya Basin is an Eocene sedimentary basin with sediment sourced from both the İAESZ and Söğüt Thrust fault to the south and north, respectively, and formed primarily by flexural loading from north‐south shortening along the syncollisional Söğüt Thrust. Our results refine the timing of collision between the Anatolides and Pontide terranes in western Anatolia to Maastrichtian‐Middle Paleocene and Early Eocene crustal shortening and basin formation. Furthermore, we demonstrate contemporaneous collision, deformation, and magmatism across the İAESZ, supporting synchronous collision models. We show that regional postcollisional magmatism can be explained by renewed underthrusting instead of slab breakoff. This new İAESZ chronology provides additional constraints for kinematic, geodynamic, and biogeographic reconstructions of the Mediterranean domain

Additions to the late Eocene Süngülü mammal fauna in Easternmost Anatolia and the Eocene-Oligocene transition at the periphery of Balkanatolia

The Eocene-Oligocene transition marks a period of dramatic global climatic change correlated with pronounced mammalian faunal change. Fossil evidence is indispensable for studying the distribution of taxa through time, and determining how abiotic parameters shaped ancient biodiversity. Here we report ruminant artiodactyls and a new anthropoid primate from Süngülü, a locality in Eastern Anatolia that has yielded a diversified and largely endemic assemblage of rodents. Three taxa of ­ruminants are recognized, the tragulid Iberomeryx parvus Gabunia, 1964, a larger species of Iberomeryx Gabunia, 1964, and a bachitheriid referred to cf. Bachitherium sp. A lower molar is identified as the new eosimiid primate Sungulusimias unayae n. gen., n. sp., which is the first occurrence of Paleogene anthropoids in western Asia. The lower molar of Sungulusimias unayae n. gen., n. sp. is characterized by protoconid and metaconid closely spaced and of similar height and volume, paraconid cuspidate and nearly connate with metaconid, strong mesiobuccal cingulid, and entoconid without strong connection to hypoconulid via the postcristid. The composition of this assemblage together with rodents indicates a probable Latest Eocene age for Süngülü, although an early Oligocene age cannot be completely ruled out. The rodent fauna from Süngülü suggests that endemism persisted at the periphery of Balkanatolia until the latest Eocene while Eastern Anatolia was situated in a strategic corridor for faunal exchanges between eastern Asia, Indo-Pakistan and Europe. During the Eocene-Oligocene transition, Balkanatolia probably functioned as a “holding pen” where various taxa were confined for significant intervals of time before proceeding to colonize Western Europe at the Grande Coupure

Dental anatomy, phylogenetic relationships and paleoecology of Orhaniyeia nauta (Metatheria, Anatoliadelphyidae), a Gondwanan component of the insular Eocene mammal fauna of Balkanatolia (north-central Turkey)

International audienceTwo new specimens of the anatoliadelphyid metatherian Orhaniyeia nauta are described from the middle Eocene Uzunçarşıdere Formation in the Orhaniye Basin, north-central Turkey. These specimens augment our knowledge of the dentition of this taxon, revealing that P3 and p3 of Orhaniyeia resemble those of its sister taxon Anatoliadelphys in being enlarged and highly inflated, suggesting that both taxa consumed a durophagous diet. The ancestral dental morphology of anatoliadelphyids likely approximated that of Orhaniyeia nauta, whereas the dentition of Anatoliadelphys is autapomorphous. A phylogenetic analysis incorporating the new data for Orhaniyeia reconstructs anatoliadelphyids as nested among a diverse, but generally poorly documented, assemblage of early Paleogene bunodont Gondwanan marsupials that are typically allied with polydolopimorphians. Alternative phylogenetic reconstructions based on Anatoliadelphys alone have suggested either peradectid or protodidelphid affinities for anatoliadelphyids, but these hypotheses are not supported by the new data from Orhaniyeia. Anatoliadelphyids likely colonized Balkanatolia from the south (Africa/Arabia), even though there is no current fossil record indicating that this Gondwanan bunodont marsupial clade ever inhabited Africa/Arabia. The durophagous diet of Orhaniyeia was probably eclectic, but with an emphasis on gastropods. A similar dietary reconstruction has been proposed for the Australian Miocene marsupial Malleodectes, the dentition of which is remarkably convergent with that of Orhaniyeia. Orhaniyeia and Anatoliadelphys appear to have exploited distinct ecological niches, because the autapomorphous dentition of Anatoliadelphys includes multiple specializations for enhanced carnivory. The colonization of Balkanatolia by anatoliadelphyids instigated a small endemic radiation, a pattern that was replicated by multiple other Balkanatolian mammal clades

The surface response to Cenozoic drip tectonics in central Anatolia

International audienceLithospheric dripping is commonly invoked to reconcile the rapid surface uplift of orogenic plateaus. Rapid surface uplift results in the development or strengthening of pre-existing orographic barriers, which motivates changes in climate and intensifies precipitation gradients across front ranges. In turn, focused precipitation increases erosion rates and generates relief. Thus, understanding when, where, and how quickly lithospheric dripping events occurred within the broader Central Anatolian Plateau has important implications for the development of topography through time, which directly influences speciation, basin architecture, and the distribution of natural resources. Here, we propose that the present-day physiography of the broader Central Anatolian Plateau is in part a result of a ~10,000 km2 lithospheric foundering event from 37–35 Ma along the Izmir-Ankara-Erzincan suture zone in the Çankiri basin region, and a more recent ~40,000 km2 event that occurred within the Konya basin region of the more southerly Tauride Block.In detail, marine sedimentation within the Çankiri basin transitions to purely terrestrial deposition from 42–37 Ma, defined by a ~1 km thick section of interfingering fluvial and evaporite-bearing lacustrine deposits until 32 Ma. Shortly after 32 Ma the Çankiri basin was structurally inverted. A basin-wide unconformity bevels structurally inverted terrestrial sequences above which multi-meter, thick and gnarled Miocene evaporite sequences are present. West of the Çankiri basin, Miocene adakite-like magmatism initiated within the Galatean Volcanic Province as contractional deformation transitioned to strike-slip tectonics. Furthermore, we observe a rapid decrease in detrital zircon εHf values at ~37 Ma followed by a rapid increase at ~35 Ma, which we interpret as additional evidence for the rapid growth and removal of a lithospheric welt. Further south, previously published full-waveform tomography suggests the Konya basin region of the Tauride Block (i.e., the Central Anatolian Plateau strictly speaking), is underlain by a region of anomalously fast seismic velocities at ~40 km depth, above which a semi-rigid, fault-bound, ~1km high, low-relief, internally drained, diamond-shaped depression is present – broadly consistent with lithospheric dripping analogs from the Bolivian Altiplano

The surface response to Cenozoic drip tectonics in central Anatolia

International audienceLithospheric dripping is commonly invoked to reconcile the rapid surface uplift of orogenic plateaus. Rapid surface uplift results in the development or strengthening of pre-existing orographic barriers, which motivates changes in climate and intensifies precipitation gradients across front ranges. In turn, focused precipitation increases erosion rates and generates relief. Thus, understanding when, where, and how quickly lithospheric dripping events occurred within the broader Central Anatolian Plateau has important implications for the development of topography through time, which directly influences speciation, basin architecture, and the distribution of natural resources. Here, we propose that the present-day physiography of the broader Central Anatolian Plateau is in part a result of a ~10,000 km2 lithospheric foundering event from 37–35 Ma along the Izmir-Ankara-Erzincan suture zone in the Çankiri basin region, and a more recent ~40,000 km2 event that occurred within the Konya basin region of the more southerly Tauride Block.In detail, marine sedimentation within the Çankiri basin transitions to purely terrestrial deposition from 42–37 Ma, defined by a ~1 km thick section of interfingering fluvial and evaporite-bearing lacustrine deposits until 32 Ma. Shortly after 32 Ma the Çankiri basin was structurally inverted. A basin-wide unconformity bevels structurally inverted terrestrial sequences above which multi-meter, thick and gnarled Miocene evaporite sequences are present. West of the Çankiri basin, Miocene adakite-like magmatism initiated within the Galatean Volcanic Province as contractional deformation transitioned to strike-slip tectonics. Furthermore, we observe a rapid decrease in detrital zircon εHf values at ~37 Ma followed by a rapid increase at ~35 Ma, which we interpret as additional evidence for the rapid growth and removal of a lithospheric welt. Further south, previously published full-waveform tomography suggests the Konya basin region of the Tauride Block (i.e., the Central Anatolian Plateau strictly speaking), is underlain by a region of anomalously fast seismic velocities at ~40 km depth, above which a semi-rigid, fault-bound, ~1km high, low-relief, internally drained, diamond-shaped depression is present – broadly consistent with lithospheric dripping analogs from the Bolivian Altiplano

Correction: Eocene metatherians from Anatolia illuminate the assembly of an island fauna during Deep Time.

[This corrects the article DOI: 10.1371/journal.pone.0206181.]

The Geodynamic Implications of Passive Margin Subduction in Northwest Turkey

International audienceThe number of subduction zones that facilitated the northward translation of the Anatolide-Tauride continental terrane derived from Gondwana to the southern margin of Eurasia at the longitude of western Turkey is debated. We hypothesized that if two north dipping subduction zones facilitated incipient collision in western Turkey, a late Cretaceous arc would have formed within the Neotethys and along the southern margin of Eurasia. To determine if an island arc formed within the Neotethys we investigated the sedimentary record of the Central Sakarya basin, which was deposited along the southern margin of Eurasia from 85 to 45 million years ago. Detrital zircon deposited within the lower levels of the Central Sakarya basin (the Değirmenözü Formation) are associated with south to north-directed paleocurrents and exhibit a unimodal late Cretaceous age peak sourced from isotopically juvenile mantle melts. Zircon maximum depositional ages from the Değirmenözü Formation cluster between 95 and 90 Ma and are 5–10 Myr older than biostratigraphic depositional ages. Between 95 and 80 Ma, a 12-unit shift from mantle to crustal derived εHf values occurs in the overlying Yenipazar Formation. We explain the absence of Paleozoic, Eurasian-sourced detrital zircon, the rapid shift from mantle to crustal derived εHf values, and lag time in terms of passive margin subduction within an isolated intra-oceanic subduction zone, whose island arc was reworked from south to north into the Central Sakarya basin during incipient collision. Thus, widely outcropping late Cretaceous plutonic rocks within Eurasia must have belonged to an additional convergent margin

Rapid colonization and diversification of a large-bodied mammalian herbivore clade in an insular context: New embrithopods from the Eocene of Balkanatolia

International audienceEmbrithopoda is an extinct clade of herbivorous placental mammals belonging to the afrotherian subclade Paenungulata. Early in their evolutionary history embrithopods colonized the insular terrane of Balkanatolia, presumably via dispersal across the Tethyan marine barrier that separated Africa from Eurasia during the early Cenozoic. Here we report new embrithopods from the early Eocene locality of Çamili Mezra, Çiçekdaği Basin, central Anatolia which document the early co-occurrence of two sympatric taxa of embrithopods, including Crivadiatherium sevketseni sp. nov. and Crivadiatherium sahini sp. nov. The genus Crivadiatherium, otherwise known only from the late Eocene of Romania, is reported for the first time in Anatolia. Hypsamasia seni from the middle Eocene of north-central Anatolia is interpreted as a nomen dubium. Embrithopod specimens previously described as Palaeoamasia sp. nov. from the Eocene-Oligocene transition of the Boyabat Basin in northern Anatolia are identified as a new genus and species, Axainamasia sandersi. The embrithopod fauna of Çamili Mezra indicates that this clade experienced at least a modest adaptive radiation after successfully colonizing Balkanatolia. The Balkanatolian record of embrithopod evolution contrasts with the evolutionary history of this clade in its native Africa, where sympatric embrithopod taxa have never been documented

Sedimentary provenance from the evolving forearc‐to‐foreland Central Sakarya Basin, western Anatolia reveals multi‐phase intercontinental collision

International audienceCollision 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 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 detrital zircons, 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