Lithospheric drips have been interpreted for various regions around the globe to account for the recycling of the continental lithosphere and rapid plateau uplift. However, the validity of such hypothesis is not well documented in the context of geological, geophysical and petrological observations that are tested against geodynamical models. Here we propose that the folding of the Central Anatolian (Kirsehir) arc led to thickening of the lithosphere and onset of "dripping" of the arc root. Our geodynamic model explains the seismic data showing missing lithosphere and a remnant structure characteristic of a dripping arc root, as well as enigmatic >1 km uplift over the entire plateau, Cappadocia and Galatia volcanism at the southern and northern plateau margins since ~10 Ma, respectively. Models show that arc root removal yields initial surface subsidence that inverts >1 km of uplift as the vertical loading and crustal deformation change during drip evolution.

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Drip tectonics and the enigmatic uplift of the Central Anatolian Plateau.

It is generally agreed that mantle dynamics have played a signiﬁcant role in generating and maintaining the elevated topography of Anatolia during Neogene times. However, there is much debate about the relative importance of subduction zone and asthenospheric processes. Key issues concern onset and cause of regional uplift, thickness of the lithospheric plate, and the presence or absence of temperature and / or compositional anomalies within the convecting mantle. Here, we tackle these interlinked issues by analyzing and modeling two disparate suites of observations. First, a drainage inventory of 1,844 longitudinal river proﬁles is assembled. This geomorphic database is inverted to calculate the 18
variation of Neogene regional uplift through time and space by minimizing the misﬁt between observed and calculated river proﬁles subject to independent calibration. Our results suggest that regional uplift commenced in the east and propagated westward. Secondly, we have assembled a database of geochemical analyses of basaltic rocks. Two di ﬀ erent approaches have been used to quantitatively model this database with a view to determining the depth and degree of asthenospheric melting across Anatolia. Our results suggest 
that melting occurs at depths as shallow as 60 km in the presence of mantle potential temperatures as high as 1390◦
C. There is evidence that potential temperatures are higher in the east, consistent with the pattern of sub-plate shear wave velocity anomalies. Our combined results are consistent with isostatic and admittance analyses and suggest that elevated asthenospheric temperatures beneath thinned Anatolian lithosphere have played a ﬁrst order role in generating and maintaining regional dynamic topography and basaltic magmatism.

Neogene Uplift and Magmatism of Anatolia: Insights From Drainage Analysis and Basaltic Geochemistry

National Science Foundation [EAR-1109336]; Wiess Postdoctoral Research Fellowship at Rice University

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Subduction termination through progressive slab deformation across Eastern Mediterranean subduction zones from updated P-wave tomography beneath Anatolia

We compiled geochronology data from 87 published studies within the Anatolia orogen (32.5°E–44°E) to investigate the spatial and temporal patterns of continental magmatism during the final stages of Neotethys Ocean closure. The number and diversity of studies compiled here collectively provide a thorough characterization of magmatism (>700 ages) in the Anatolia orogen since the Late Cretaceous (ca. 100 Ma). Our new compilation reveals that magmatism was episodic and occurred in three distinct magmatic episodes punctuated by two orogen-wide magmatic lulls. We used regional-scale insights into the timing, location, composition, and evolution of magmatism revealed by our compilation to evaluate the tectonic and geodynamic processes responsible for each widespread magmatic lull, and to test and refine existing geodynamic models for Anatolia. We interpret the first orogen-wide magmatic lull (ca. 72–58 Ma) to have been the result of Maastrichtian to Paleocene collision of the Kırşehir and Anatolide-Tauride blocks with the Pontides arc along the Izmir-Ankara-Erzincan suture zone and synchronous collision of the Bitlis-Pütürge massif with the southern-margin of the Anatolide-Tauride blocks along the Bitlis suture zone. Magmatic quiescence during the second magmatic lull (ca. 40–20 Ma) was variably related to terminal subduction and Arabia slab break off along the Bitlis suture zone in the east, and Cyprus slab flattening due to postcollisional southward retreat of the Cyprus trench in the west, each triggered by middle to late Eocene Arabia collision. Postcollisional Neogene–Quaternary magmatism was most likely caused by lithospheric delamination and slab tearing/rollback in the Eastern and Central Anatolia volcanic provinces, respectively.

Dynamics of episodic Late Cretaceous–Cenozoic magmatism across Central to Eastern Anatolia: New insights from an extensive geochronology compilation

The central Anatolian plateau in Turkey is a region with a long history of subduction, continental collision, accretion of continental fragments, and slab tearing and/or breakoff and tectonic escape. Central Anatolia is currently characterized as a nascent plateau with widespread Neogene volcanism and predominantly transtensional deformation. To elucidate the present-day crustal and upper mantle structure of this region, teleseismic receiver functions were calculated from 500 seismic events recorded on 92 temporary and permanent broadband seismic stations. Overall, we see a good correlation between crustal thickness and elevation throughout central Anatolia, indicating that the crust may be well compensated throughout the region. We observe the thickest crust beneath the Taurus Mountains (>40 km); it thins rapidly to the south in the Adana Basin and Arabian plate and to the northwest across the Inner Tauride suture beneath the Tuz Gölü Basin and Kırşehir block. Within the Central Anatolian Volcanic Province, we observe several low seismic velocity layers ranging from 15 to 25 km depth that spatially correlate with the Neogene volcanism in the region, and may represent crustal magma reservoirs. Beneath the central Taurus Mountains, we observe a positive amplitude, subhorizontal receiver function arrival below the Anatolian continental Moho at ~50–80 km that we interpret as the gently dipping Moho of the subducting African lithosphere abruptly ending near the northernmost extent of the central Taurus Mountains. We suggest that the uplift of the central Taurus Mountains (~2 km since 8 Ma), which are capped by flat-lying carbonates of late Miocene marine units, can be explained by an isostatic uplift during the late Miocene–Pliocene followed by slab breakoff and subsequent rebound coeval with the onset of faster uplift rates during the late Pliocene–early Pleistocene. The Moho signature of the subducting African lithosphere terminates near the southernmost extent of the Central Anatolian Volcanic Province, where geochemical signatures in the Quaternary volcanics indicate that asthenospheric material is rising to shallow mantle depths. INTRODUCTION Central Anatolia displays a typical plateau-like morphology that appears similar to other collision-related plateaus but on a smaller scale. Elevation increases in the interior of the central Anatolian plateau to the north and the Taurus Mountains to the south (Fig. 1). The crustal architecture of the central Anatolian plateau comprises the amalgamation of continental fragments that coalesced during the closure of the Neo-Tethyan Ocean system between AfricaArabia and Eurasia and records both subduction and collisional-related processes (Şengör and Yılmaz, 1981). To the east of the central Anatolian plateau, compression related to the Arabia-Eurasia continental collision dominates the formation and development of tectonic structures, while regional extension due to the rollback of the African slab has dominated the west since the Miocene (Bozkurt, 2001; Ring et al., 2010). These processes have led to the development of the Anatolian plate, which has been extruding westward since the Miocene as a result of African slab rollback and Arabia-Eurasia collision (Şengör et al., 1985; Reilinger et al., 2006). Thanks to the expansion of seismic station coverage in Turkey, a number of regional-scale studies of the eastern Mediterranean have provided researchers with a broad understanding of the seismic structure of the Anatolian system (e.g., Biryol et al., 2011; Mutlu and Karabulut, 2011; Salaün et al., 2012; Fichtner et al., 2013; Vanacore et al., 2013; Delph et al., 2015; Govers and Fichtner, 2016). Smaller scale regional studies have also been performed using temporary seismic deployments to investigate the seismic structure of this system in higher detail, such as the North Anatolian Fault Experiment (Beck and Zandt, 2005) and the Eastern Turkey Seismic Experiment (Sandvol et al., 2003). This has resulted in dense seismic station coverage throughout most of Turkey, when combined with the extensive backbone network of the Kandilli Observatory and Earthquake Research Institute (KOERI). However, until recently seismic station coverage and associated studies investigating central Anatolia have been largely neglected due to its relative stability and assumed low potential of large-magnitude earthquakes. GEOSPHERE GEOSPHERE; v. 13, no. 6 doi:10.1130/GES01509.1 8 figures; 1 supplemental file CORRESPONDENCE: bizhan .abgarmi@metu .edu.tr CITATION: Abgarmi, B., Delph, J.R., Ozacar, A.A., Beck, S.L., Zandt, G., Sandvol, E., Turkelli, N., and Biryol, C.B., 2017, Structure of the crust and African slab beneath the central Anatolian plateau from receiver functions: New insights on isostatic compensation and slab dynamics: Geosphere, v. 13, no. 6, p. 1774–1787, doi:10.1130/GES01509.1. Received 4 February 2017 Revision received 16 August 2017 Accepted 27 September 2017 Published online 27 October 2017 For permission to copy, contact Copyright Permissions, GSA, or editing@geosociety.org. © 2017 Geological Society of America THEMED ISSUE: Mantle to Surface Dynamics during the Transition from Subduction to Collision to Tectonic Escape: Results from the Continental Dynamics–Central Anatolian Tectonics (CD-CAT) Project

Structure of the crust and African slab beneath the central Anatolian plateau from receiver functions: New insights on isostatic compensation and slab dynamics

Widespread mafic volcanism, elevated crustal temperatures, and plateau-type topography in Central Anatolia, Turkey, could collectively be the result of lithospheric delamination, mantle upwelling, and tectonic escape. We use results from 40Ar/39Ar geochronology, basalt geochemistry, and a passive-source broadband seismic experiment obtained in a collaborative international effort (Continental Dynamics-Central Anatolia Tectonics) to investigate the upper mantle structure and evolution of melting conditions over an ∼2400 km2 area south and west of Hasan volcano. New 40Ar/39Ar dates for the basalts mostly cluster between 0.2 and 0.6 Ma, but some scoria cones are as old as 2.5 Ma. Basalts are dominantly Mg-rich (Mg# = 62–71), moderately alkaline (normative Ne < 5 wt %), and, based on major and trace element signatures, derived from a peridotitic source. Covariations between radiogenic isotope and trace element signatures reveal contributions from a subduction-related component and intraplate-like mantle asthenosphere, as well as from ambient upper mantle. Central Anatolian basalts reflect maximum mantle potential temperatures of <1350°C and an average pressure of melt equilibration of 1.4 GPa, which are cooler and shallower than for basalts from Eastern and Western Anatolia. When considered in light of regionally slow upper mantle shear wave velocities, the mantle lithosphere may be thin and infiltrated by melts, or largely absent. An absence of secular changes in melting conditions suggests little to no lithospheric thinning over the past ∼1 Ma, despite evidence for lithospheric extension. Hasan basalts appear to be generated by decompression melting in response to the rollback of the Cyprean slab.

W. Kirk Schleiffarth

Papers

Shallow melting of MORB‐like mantle under hot continental lithosphere, Central Anatolia