Tectonic Evolution of the Eastern Black Sea and Caucasus : An introduction

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The 2014 Earthquake Model of the Middle East: seismogenic sources

The Earthquake Model of Middle East (EMME) project was carried out between 2010 and 2014 to provide a harmonized seismic hazard assessment without country border limitations. The result covers eleven countries: Afghanistan, Armenia, Azerbaijan, Cyprus, Georgia, Iran, Jordan, Lebanon, Pakistan, Syria and Turkey, which span one of the seismically most active regions on Earth in response to complex interactions between four major tectonic plates i.e. Africa, Arabia, India and Eurasia. Destructive earthquakes with great loss of life and property are frequent within this region, as exemplified by the recent events of Izmit (Turkey, 1999), Bam (Iran, 2003), Kashmir (Pakistan, 2005), Van (Turkey, 2011), and Hindu Kush (Afghanistan, 2015). We summarize multidisciplinary data (seismicity, geology, and tectonics) compiled and used to characterize the spatial and temporal distribution of earthquakes over the investigated region. We describe the development process of the model including the delineation of seismogenic sources and the description of methods and parameters of earthquake recurrence models, all representing the current state of knowledge and practice in seismic hazard assessment. The resulting seismogenic source model includes seismic sources defined by geological evidence and active tectonic findings correlated with measured seismicity patterns. A total of 234 area sources fully cross-border-harmonized are combined with 778 seismically active faults along with background-smoothed seismicity. Recorded seismicity (both historical and instrumental) provides the input to estimate rates of earthquakes for area sources and background seismicity while geologic slip-rates are used to characterize fault-specific earthquake recurrences. Ultimately, alternative models of intrinsic uncertainties of data, procedures and models are considered when used for calculation of the seismic hazard. At variance to previous models of the EMME region, we provide a homogeneous seismic source model representing a consistent basis for the next generation of seismic hazard models within the region.Published3465-34966T. Studi di pericolosità sismica e da maremotoJCR Journa

Comparisons of the suture zones along a geotraverse from the Scythian Platform to the Arabian Platform

The area from the Greater Caucasus to the southeast Turkey is characterized and shaped by several major continental blocks. These are Scythian Platform, Pontian–Transcaucasus Continent-Arc System (PTCAS), the Anatolian–Iranian and the Arabian Platforms. The aim of this paper is to define these continental blocks and describe and also compare their boundary relationships along the suture zones. The Scythian Platform displays the evidence of the Hercynian and Alpine orogens. This platform is separated from the PTCAS by the Greater Caucasus Suture Zone. The incipient collision began along this suture zone before middle–late Carboniferous whereas the final collision occurred before Oligocene. The PTCAS can be divided into four structural units: (1) the Georgian Block – northern part of the Pontian–Transcaucasian island-arc, (2) the southern and eastern Black Sea Coast–Adjara–Trialeti Unit, (3) the Artvin–Bolnisi Unit, comprising the northern part of the southern Transcaucasus, and (4) the Imbricated Bayburt–Garabagh Unit. The PTCAS could be separated from the Anatolian–Iranian Platform by the North Anatolian–Lesser Caucasus Suture (NALCS) zone. The initial collision was developed in this suture zone during Senonian–early Eocene and final collision before middle Eocene or Oligocene–Miocene. The Anatolian–Iranian Platform (AIP) is made up of the Tauride Platform and its metamorphic equivalents together with Iranian Platform. It could be separated from the Arabian Platform by the Southeastern Anatolian Suture (SEAS) zone. The collision ended before late Miocene along this suture zone. The southernmost continental block of the geotraverse is the Arabian Platform, which constitutes the northern part of the Arabian–African Plate. This platform includes a sequence from the Precambrian felsic volcanic and clastic rocks to the Campanian–early Maastrichtian flyschoidal clastics. All the suture zones include MORB and SSZ-types ophiolites in different ages. However, the ages of the suture zones and the crustal thicknesses along the suture zones are different, as the age becoming younger, the thickness decreasing from north to south. The emplacements of the ophiolites have similar pattern of a flower structure, reflecting both the north- and south-dipping overthrusts along the suture zones

Geodynamics of the Eurasian and Africa–Arabian collision zone as exemplified by the Black Sea–Caspian Sea region

The lithosphere structure and geological evolution of the Caucasus and adjacent areas is determined by its position in the continental collision zone between the Eurasian and African-Arabian lithosphere plates, where convergence is still on-going at average rate of movement 10–30 mm/per year. The region located in the central part of the collision zone represents the lithosphere fragments collage of the Tethys Ocean and its continental margins. Within this area the system of island arcs, intra- and back arc bsins existed during Neoproterozoic–Early Cenozoic. Supra-subduction, midocean ridges and within plate magmatic activity took place during Paleozoic–Early Cenozoic. In Late Cenozoic closure of the oceanic and backarc basins took place followed by the continent-continent collision, topography inversion and formation of modern structures in the region (Adamia et al., 1981, 2017; Dercourt et al., 1986). During the pre-collision stage there were not two, but three Tethys branches. The third of them is Van-Khoi oceanic branch. Number of palaeo-subduction zones (two or three?) is still debatable within the academic community. One research group (e.g. Sosson et al., 2010; Barrier et al., 2018) admits existence of two subduction zones: Peri-Arabian and Ankara-Erzincan-Sevan-Zangezur zones, whilst another group including the abstract authors refer to the presence of three subduction zones and aside from abovementioned zones consider the presence of the Khoy Ocean and third subduction zone related to one of the Neotethys branches (Adamia et al., 1981, 2017; Dercour et al., 1986; Stampfli, 2001). According to Adamia et al. (1981, 2017), Dercourt et al. (1986), Daralogöz-South Armenian block and Nakhchevan (SAB) in the Late Paleozoic–Mesozoic–Early Cenozoic represent the part of the Iranian but not the Anatolian Microcontinent

Far-field tectonic effects of the Arabia\u2013Eurasia collision and the inception of the North Anatolian Fault system

none6siNew thermochronological data show that rapid Middle Miocene exhumation occurred synchronously along the Bitlis suture zone and in the southeastern Black Sea region, arguably as a far-field effect of the Arabia–Eurasia indentation. Collision-related strain focused preferentially along the rheological boundary between the multideformed continental lithosphere of northeastern Anatolia and the strong (quasi)oceanic lithosphere of the eastern Black Sea. Deformation in the southeastern Black Sea region ceased in late Middle Miocene time, when coherent westward motion of Anatolia and the corresponding activation of the North and East Anatolian Fault systems mechanically decoupled portions of the foreland from the Arabia–Eurasia collision zone.mixedAlbino, I.; Cavazza, W.; Zattin, M.; Okay, A.I.; Adamia, S.; Sadradze, N.,Albino, I.; Cavazza, W.; Zattin, M.; Okay, A.I.; Adamia, S.; Sadradze, N.

Quaternary Collision-Zone Magmatism of the Greater Caucasus

The Greater Caucasus mountains (Cavcasioni) mark the northern margin of the Arabia–Eurasia collision zone. Magmatism in the central part of the Greater Caucasus began in the Pleistocene, up to ~25 Myr after initial collision. This paper presents bulk-rock and Sr–Nd–Pb isotope geochemistry from 39 Quaternary volcanic rock samples (<450 Ka) recovered from the Mt. Kazbek (Kasbegui) region of the Greater Caucasus, Georgia, to assess the sources and magmatic evolution of these lavas and the possible triggers for melting in the context of their regional tectonics. Compositions are dominantly calc-alkaline basaltic andesite to dacite (57–67 wt % SiO2). Although the lavas were erupted through thick continental crust, there is little evidence for extensive modification by crustal contamination. Trace element and isotopic systematics indicate that the lavas have supra-subduction zone signatures, most likely reflecting derivation from a lithospheric source that had been modified by melts and/or fluids from material subducted before and during the collisional event. Mass-balance modelling of the Sr–Nd isotope data indicates that the lavas require significant input from a subducted slab, with deep-sourced fluids fluxing the slab into the source region. In contrast with published data from Lesser Caucasus magmatism, data from the Mt. Kazbek region suggest that a compositionally distinct sediment source resides beneath the Greater Caucasus, producing characteristic trace element and Pb isotopic signatures. Two distinct compositional groups and therefore primary liquids can be discerned from the various volcanic centres, both derived from light rare-earth element enriched sources, but with distinct differences in Th/Yb and Dy/Yb ratios and Pb isotopes. Rare-earth element modelling of the lava sources is consistent with 3–4% melting starting in the garnet peridotite and continuing into the spinel facies or, potentially, sited in the garnet-spinel transition zone. Small-scale convection related to mantle upwelling provides a plausible mechanism for Greater Caucasus magmatism and explains the random aspect to the distribution of magmatism across the Arabia–Eurasia collision zone

Progressive orocline formation in the Eastern Pontides–Lesser Caucasus

International audienceThe Eastern Pontides–Lesser Caucasus fold–thrust belt displays a peculiar northwards arc-shaped geometry that was defined as an orocline in earlier studies. The Lesser Caucasus was affected by two main tectonic events that could have caused orocline formation: (1) Paleocene–Eocene collision of the South Armenian Block with Eurasia; and (2) Oligocene–Miocene Arabia–Eurasia collision. We tested the hypothesis that the Lesser Caucasus is an orocline and aimed to time the formation of this orocline. To determine the vertical axis rotations, 37 sites were sampled for palaeomagnetism in rocks of Upper Cretaceous–Miocene age in Georgia and Armenia. In addition, we compiled a review of c. 100 available datasets. A strike test was applied to the remaining datasets, which were divided into four chronological sub-sets, leading us to conclude that the Eastern Pontides–Lesser Caucasus fold–thrust belt forms a progressive orocline. We concluded that: (1) some pre-existing curvature must have been present before the Late Cretaceous; (2) the orocline acquired part of its curvature after the Paleocene and before the Middle Eocene as a result of South Armenian Block–Eurasia collision; and (3) about 50% of the curvature formed after the Eocene and probably before the Late Miocene, probably as a result of Arabia–Eurasia collision

The eastern Black Sea-Caucasus region during the Cretaceous : New evidence to constrain its tectonic evolution

Acknowledgments This paper has been written in tribute to my colleague and friend Jean-François Stéphan, who much motivated this work and followed it step by step. Speaking personally as the primary author, Jean-François supported and enriched my scientific work over my whole career. We spent years as office neighbors in Geoazur, and I thus had the great privilege to discuss science with Jean-François almost every day. I will never forget the great colleague and the even greater friend he was for me. These works were supported by the “Groupement De Recherche International” Géosciences Sud Caucase of the CNRS\INSU and also by the MEBE and DARIUS Programs. The authors would like to thank the two reviewers of this paper, Invited Associate Editor Bernard Mercier de Lépinay, and Associate Editor Isabelle Manighetti, who significantly improved the synopsis and the English writing of the paper.Peer reviewedPublisher PD