FINAL WORKSHOP October 25-27, 2017 Kiev, Ukraine

International Research Group Project SOUTH CAUCASUS GEOSCIENCES

The Workshop is organized by:

CNRS, Université Côte d'Azur, UMR Geoazur UNS, Observatoire de la Côte d'Azur, IRD, Sophia Antipolis France

S.I. Subbotin Institute of Geophysics, National Academy of Sciences of Ukraine, Kiev Ukraine INTERNATIONAL RESEARCH GROUP PROJECT

Tethyan evolution and continental collision in SW Caucasus (Georgia and adjacent areas)

Georgia, the westernmost part of the and Transcaucasus-Pontian belts are of North southern Caucasus located at the junction Tethyan origin while Anatolia, Taurus, Iran, of European and Asiatic branches of the Al- and the southern Lesser Caucasus belong to pine-Himalayan orogenic belt represents an the South Tethys. area where the Tethys Ocean was completely The Arabia-Nubian Shield, at the end of closed only in the late Cenozoic as a result of the Proterozoic, experienced basement con prolonged convergence between the Eurasian solidation related to the final stages of the and Africa-Arabian plates. Pan-African cycle of tectogenesis. In contrast During the Neoproterozoic—early Ceno to the southern Lesser Caucasus (Daralagoz), zoic, the territory of Georgia and the adja the Transcaucasus did not undergo this pro cent area of the Black Sea-Caspian Sea region cess because it broke away from the Arabia- were parts of the Tethys Ocean and its north Nubia Shield and, during Cambrian—Devo ern and southern margins. The Prototethys- nian, drifted deep into the Prototethys toward Paleotethys-Tethys was not a single continu the northern (Baltica) continent. ous oceanic plate, but rather developed in During the early—middle Paleozoic in the branches separating continental terranes of wake of northward-migrating Gondwanian different sizes, which rifted and drifted away fragments, the Paleotethyan basin formed, from the Gondwana margin and eventually and, in the Ordovician, along its border with collided with Laurasia. Prior to the final col the Transcaucasus, subduction of oceanic lision in the late Cenozoic, the region hosted crust occurred, accompanied by suprasu- systems of island arc, intra-arc, and back-arc bduction volcanic eruptions. Northward mi basins located between the East European gration of the Transcaucasus throughout the (Baltica) continent and Gondwana. Integra Paleozoic caused narrowing of the Protote tive geological and paleogeographical stud thys and its transformation into an oceanic ies show a collage of several tectonic units back-arc (Dizi) basin. Fragments of paleoce- (terranes) in Georgia and adjoining areas anic crust are found along the southern bor that have distinctive geological histories with der of the Transcaucasus, within accretionary Tethyan, Eurasian, or Gondwanian affinities. complexes of the Lesser Caucasus ophiolite These include the Scythian platform, the Cav- suture, and in the Pontides, also in Iranian casioni (Great Caucasus), the Transcaucasus- Garadagh. During the late Paleozoic—early Pontides, and the Lesser Cavcasioni (Cauca Mesozoic, the oceanic basin separating the sus)—Alborz—West Iran regions. Their posi Africa-Arabian continent from the Taurus- tion between the Africa-Arabian and Eurasi- Anatolian-Iranian platformal domain gradu atic continents provides a reason for grouping ally extended. During this phase, only the them into the Northern Tethyan (Eurasian) Central Iranian terrain separated from Gond and Southern Tethyan (Gondwanian) do wana, drifted northward, and collided with mains. The Scythian platform, Caucasioni, the Eurasian continent in the Late Triassic.

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The Taurus-Anatolian terrane separated from Caucasioni; pre-Late Triassic obduction in Gondwana later, in the Early-Middle Jurassic. the Lesser Caucasus; and pre-Late Jurassic During the Mesozoic—Cenozoic, Daralagoz obduction during which ultrabasic rocks were represented the northwestern most margin of thrust over the continental unit of the Artvin- the Central Iranian platform and was sepa Bolnisi Block of the Somkhet-Garabagh zone. rated from the North Anatolian platform by an The metabasites apparently represent Paleo- oceanic or back-arc basin (Khoy basin), which tethyan fragments. within the modem structure is represented by During the Oligocene, marine Tethyan ba Mesozoic — Cenozoic ophiolites of Urumieh- sins were replaced by euxinic basins, which Khoy (Iran) and Van (Turkey). are considered to represent the beginning The Paleozoic-Eocene evolution of the of syncollisional development between Ara North Tethyan domain was marked by major bian and Eurasian plates in the region. On magmatic events corresponding to the Pacif going collision during Miocene—Quater ic-type and Mediterranean stages of Tethyan nary caused inversion of topography such development. The precollisional magmatic that fold-and-thrust mountain belts of the assemblages reflect a variety of paleotectonic Cavcasioni and Lesser Cavcasioni, and the environments. They are indicative of a west intermontane foreland basins in between Pacific-type oceanic setting in which a ma were formed. In the late Miocene, coeval with ture, Andean-type continental arc developed. molasse deposition in the foreland basins, There were several episodes of oceanic litho subaerial volcanic eruptions occurred, char spheric obduction onto the continental ter- acterized by intensively fractionated magma ranes of the region: the middle-late Paleozoic, of suprasubduction-type calc-alkaline series during which basite-ultrabasite complexes from basalts to rhyolites. were thrust over the island-arc system of the In addition to volcanism, earthquakes indi Transcaucasus and the Main Range zone of cate active tectonics in Georgia. Some of the

36°E 42°E 48°E 54°E

42°N

36°N

]Q mm/vr 95% confidence

Fig. 1. Map showing global positioning system (GPS) velocities with respect to Eurasia and 95 % confidence ellipses for the eastern Black Sea—Caucasus—Caspian region [Vemant et al., 2013]. reo(pU3UHecxiiu xcypiiaA № 4, T. 39, 2017 79 INTERNATIONAL RESEARCH GROUP PROJECT major earthquakes have proven to be devas deformation of the crust and lithosphere of tating; i.e., the Racha earthquake of 29 April the region have taken place via compres 1991, with Ms=6.9, was the strongest ever re sional structures, as well as lateral tectonic corded in Georgia. The fault plane solution escape. The geometry of the topography and data for 130 earthquakes show that the terri tectonic features is largely determined by the tory of Georgia is currently under latitudinal wedge-shaped rigid Arabian block (indentor) compression, longitudinal extension, and an and by the configuration of the oceanic-sub- overall crustal thickening. A complex network oceanic lithosphere (buttresse) of the eastern of faults divides the region into a number of Black Sea and south Caspian Sea, all of which separate blocks. Three principal directions of cause bending of the main morphological and active faults compatible with the dominant, tectonic structures of the region around the near N-S compressional stress produced by strong lithosphere (Fig. 1). northward displacement of the Arabian plate Large-scale intraplate deformation of the can be distinguished: one longitudinal, trend lithosphere of the region as a result of the in ing WNW-ESE or W-E, and two transversal, dentation of Arabian and Indian plates result trending NE-SW and NW-SE. The first group ed in Late Cenozoic shortening and uplift of (WNW-ESE), the so-called «Caucasian» the mountain belts of the region, subsidence strike, is composed of compressional struc acceleration of the Black Sea—South Caspian tures, including reverse faults, thrusts, thrust crust, formation of submeridional, transversal slices, and strongly deformed fault-propa megastructure of the Caspian Sea that evi gation folds. The transversal faults are also dence for interference of lithospheric folding mainly compressional structures, but they contain considerable strike-slip components patterns induced by the Arabian and Indian as well. The tensional nature of submeridional collision with Eurasia [Smit et al., 2013]. faults is associated with intensive Neogene- Acknowledgements. This work was sup Quaternary volcanism in the Transcaucasus. ported by Shota Rustaveli National Science The NE-SW left-lateral strike-slip faults are Foundation (SRNSF), projects № 04-45 (GDRI the main seismoactive structures in the west — International Research Group: South Cau ern Transcaucasus, while right-lateral strike- casus GeoScience (Georgia — Eastern Black slip faults are developed in the southeastern Sea)) and № 217408 (Interactive Geological Transcaucasus. Considerable shortening and Map of Georgia, scale 1:200 000).

References

SmitJ. H. V., Cloetingh S. A. P. L., Burov E., Tesauro M., KarakhanianA.,AvagyanA., ErgintavS., DjamourY., Sokoutis D., Kaban M., 2013. Interference of litho Doerflinger E., RitzJ.-F., 2013. GPS constraints on spheric folding in western Central Asia by simulta continental deformation in the Black Sea, Caucasus neous Indian and Arabian plate indentation. Tecto- and Caspian region: Implications on geodynamics nophysics 602(Spec. is. Topo-Europe III), 176—194. and seismic hazard. Darius Programme (24—25June, https://doi.Org/10.1016/j.tecto.2012.10.032. 2013), Eastern Black Sea and Caucasus, Abstracts VemantP., KingR., ReilingerR., Floyd M„ McCluskyS., Volume: Tbilisi, Georgia, I. Javakhishvili Tbilisi State Hahubia C., Sokhadze G., Elashvili M„ Kadirov F., University, P. 74—75.

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Structural architecture of the eastern Achara-Trialeti fold and thrust belt, Georgia: Implications for kinematic evolution

1Tbilisi State University, M. Nodia Institute of Geophysics, Tbilisi, Georgia 2Université Côte d'Azur, UMR Géoazur, CNRS, Observatoire de la Côte d’Azur, IRD, Sophia Antipolis, France 3Tbilisi State University, Faculty of Exact and Natural Sciences, Tbilisi, Georgia 4Tbilisi State University, A. Janelidze Institute of Geology, Tbilisi, Georgia

We introduce a tectonic model of the east strata. The growth of eastern Achara-Trialeti ern Achara-Trialeti fold and thrust belt (AT- thick-skinned structures at northern part of FTB) based on the recent field data, inter the Lesser Caucasus, formed by basement preted seismic reflection profiles and regional wedge that propagated along detachment balanced cross section from northern part of horizons within the cover generating thin- Lesser Caucasus orogene. Like other collision- skinned structures. The kinematic evolution induced Alpine-type fold-thrust belts (e.g. of south-vergent backthrust zone is related [Naylor, Sinclair, 2008]), the Lesser Caucasus to northward propagating thrust wedge. is a typical doubly-vergent orogenic wedge The main style of deformation within the represented by pro and retro wedges and backthrust zone is a series of fault-propa ATFTB is a constituent part of retro wedge gation folds and are developed in Cretace- [Alania et al., 2017]. ous-Paleogene strata. Frontal part of the The seismic interpretation presented here eastern ATFTB is represented by triangle is further constrained by surface geology and zone [Alania et al., 2016; Sosson et al., 2013, subsurface geology revealed by several well 2016]. penetrations. Fault-related folding theories On base of published information about his were used to constrain the seismic interpre torical and recent earthquake data [Tsereteli et tation and of the regional balanced cross-sec al., 2016; Varazanashvili et al., 2011], absolute tion [Suppe, 1983; Shawetal., 2005]. Seismic ages of deformed volcanic rocks (Pliocene- reflection data reveals presence of basement Quaternary) from southern part of study area structural wedge, south-vergent backthrust, [Lebedev et al., 2007] and syntectonic units north-vergent forethrust and some structural from frontal part of eastern ATFTB [Alania wedges. et al., 2016] we conclude that compressive Stratigraphy in the ATFTB records the deformation started in Middle Miocene and evolution from the extensional Achara- continues today. Trialeti Basin to Kura foreland basin of the Acknowledgments. This work was funded Arabia-Eurasia collision zone. The rocks in by GDRI-IRG (Project #04-45) and Shota volved in the deformation range from Paleo Rustaveli National Science Foundation (SRN- zoic basement rocks to Mesozoic-Neogene SF) (grants YS15_2.1.5_78 and 217942).

References

Alania V., Chabukiani A., Enukidze O., Razmadze A., Structural model of the eastern Achara-Trialeti fold Sosson M., Tsereteli N., Varazanashvili O., 2017. and thrust belt using seismic reflection profiles.

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19th EGU General Assembly, EGU2017, proceed Enukidze O., Sadradze N., Hassig M., 2013. From ings from the conference held 23—28 April, 2017 Greater to Lesser Caucasus: new insights from sur in Vienna, Austria, p. 5064. face and subsurface data along a N-S trending tran sect (Georgia): Thick-skin versus thin-skin tecton Alania V., ChabukianiA., ChagelishviliR., Enukidze O., ics. Darius News (3), 5—7. Gogrichiani K., Razmadze A., Tsereteli N., 2016. Growth structures, piggyback basins and growth Sosson M., Stephenson R., Sheremet Y., Rolland Y., Ada strata of Georgian part of Kura foreland fold and mia Sh., Melkonian R., Kangarli I , Yegorova T., thrust belt: implication for Late Alpine kinematic Avagyan A., Galoyan Gh., Danelian T., Hassig M., evolution. In: M. Sosson, R. Stephenson, Sh. Adamia Meijers M., Muller C., Sahakyan L., Sadradze N., (eds.). Tectonic Evolution of the Eastern Black Sea Alania V., Enukidze O., MosarJ., 2015. The Eastern and Caucasus. Geol. Soc. London Spec. Publ. 428. Black Sea—Caucasus region during Cretaceous: doi: 10.1144/SP428.5. new evidence to constrain its tectonic evolution. Comptes Rendu Geoscience 348,23—32. https://doi. Lebedev V A., Bubnov S. N., Dudauri O. Z., Vashakid- org/10. 1016/j.crte.2015.11.002. ze G. T., 2008. Geochronology of Pliocene Volcanism in the Dzhavakheti Highland (the Lesser Caucasus). Suppe J., 1983. Geometry and kinematics of fault-bend Part 2: Eastern Part of the Dzhavakheti Highland. Re folding. Amer. J. Sci. 283, 684—721. doi: 10.2475/ gional Geological Correlation. Stratigr. Geol. Correl. ajs.283.7.684. 16(is. 5), 553—574. doi: 10.1134/S0869593808050080. TsereteliN., Tibaldi A, Alania V., GventsadseA., Enukid Naylor M., Sinclair H. D., 2008. Pro- vs. retro-foreland ze O., Varazanashvili O., Muller B. I. R., 2016. Ac basins. Basin Research 20(is. 3), 285—303. doi: tive tectonics of central-western Caucasus, Geor 10.1111/j. 1365-2117.2008.00366.x. gia. Tectonophysics 691, 328—344. doi: 10.1016/j. tecto.2016.10.025. ShawJ., Connors C., SuppeJ. (eds.), 2005. Seismic inter pretation of contractional fault-related folds. AAPG Varazanashvili O., Tsereteli N., Tsereteli E., 2011. His Studies in Geology 53, 156 p. torical earthquakes in Georgia (up to 1900): source analysis and catalogue compilation. Tbilisi: Publ. Sosson M., Adamia Sh., Muller C., Rolland Y., Alania V, House. MVP, 77 p.

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Evidence of volcanic eruptions witnessed by prehistoric man in Armenia and Argentina

'institute of Geological Sciences, National Academy of Sciences of Republic of Armenia, Yerevan, Armenia 2Geosciences Montpellier, Montpellier, France 3NancyUniversite, Vandoeuvre-les-Nancy, France 4Institute of Geological Sciences, University of Bern, Bern, Switzerland institute of History, National Academy of Sciences of Republic of Armenia, Yerevan, Armenia 6Instituto de Investigation en Paleobiologia y Geologia Universidad Nacional de Rio Negro, Rio Negro, Argentina

Prehistoric petroglyphs (rock-carvings, cestors witnessed volcanic eruption in Trans rock engravings) are widely spread from caucasia. Europe to the Far East, Central Asia, Africa, There are several direct and indirect tech Australia and Americas. Tens of thousands niques to date petroglyphs. The relative- of petroglyphs have been discovered in the comparative methods based on the analysis Armenian Highland, at elevations ranging in of content, style and carving technique with from 600 to 3300 m a.s.l. Strikingly, two rock- related archaeological monuments give ap art sites, although located thousands km proximate age estimations. The precise dat away from each other (Armenia in Eurasia, ing of petroglyphs is quite difficult, since the and Argentina in South America) exhibit well nature of the material to be dated is rarely pronounced similarities in content and style. suited to apply the whole variety of traditional Geological evidences indicate that both areas physical dating methods. were affected by recent volcanic eruptions. In this contribution we focus on an in In both sites, interpretation of the pictures, direct dating technique, by first dating the as well as historical and archaeological data, main lava-flow surrounding the petroglyphs strongly suggest that the engraved images site. may depict volcanic eruptions. Geochronological dating techniques: cos In the Armenian site, situated on the bank mic ray exposure dating with 3He and Ar/Ar of a small river in Syunik volcanic upland, sev were applied in parallel, along with the clas eral petroglyphs are engraved on ca. 1.5 m sical geological and geomorphological char diameter basalt boulders. The ancient artists acterization. About 35 samples were collected have represented splashing lava fountains for cosmogenic 3He exposure dating, from with volcanic bombs similar to volcanic erup different lava flows. The eruption of Porak vol tion of Strombolian type. Depiction of such cano, situated 11 km NNW from the rock-art geological phenomenon found in Armenia, is site, indicates an age of 28±6 Ka (la). Another unique for the entire region, including East source of lava flow in the Karkar plateau situ ern Turkey, Transcaucasia and Iran. This fact ated about 25 km to the SSE yields younger can be an indication, that our prehistoric an ages of 9.4±1.2 Ka and 5.2±0.4 Ka. Cosmogen-

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ic 3He dating of boulders samples at the site to establish a first time frame for the age of where the Armenian petroglyph was discov these petroglyphs: they were probably carved ered yield exposure ages comprised between between 30 and 5 Ka. In order to obtain more 15 and 30 Ka. A global analysis including the precise age of the engraving, we will carry geological, geomorphological and glaciologi- out further cosmogenic 3He dating and OSL cal data supports the reliability of these new dating (surface age) of basaltic boulders at geochronological data and makes possible the petroglyph site.

New data on the tectonic evolution of the Khoy region, NW Iran

'institute of Geological Sciences, National Academy of Sciences of Republic of Armenia, Yerevan, Armenia 2Geological Survey of Iran, Tehran, Iran 3Université Côte d'Azur, UMR Géoazur, CNRS, Observatoire de la Côte d'Azur, IRD, So phia Antipolis, France 4Nannofossils Biostratigraphy Consulting, Santok, Poland 5Universite' de Lille — Sciences et Technologies, CNRS, UMR 8198 Evo-Eco-Pale'o, Lille, France 6Université de Montpellier INSU-CNRS, Laboratoire Géosciences, Montpellier, France

The Khoy region (NW Iran) is important extended Paleocene detrital deposits cover in the clarification of the structural frame the Campanian-Maastrichtian rocks. The work of the Alpine Belt between the Tau- Eocene formations characterize a basin rides, the Lesser Caucasus and the NW Iran filled with volcanogenic and sedimentary belt. This area is well known for its ophiolit- layers. The Middle and Upper Eocene se ic units. We present here new stratigraphic ries unconformably overlie the ophiolites, and structural data that can be used to their Campanian-Maastrichtian cover and reconstruct the tectonic evolution of this Paleocene deposits. This corresponds to a region and then to establish connections syn-orogenic basin formed after the col between these belts. According to new data lision between Eurasia and the Taurides- from nannoplankton assemblages, the ob- Anatolides-South Armenian microplate. ducted ophiolite of the Khoy complex was The Oligocene-Miocene Qom Formation thrusted over a sheared Campanian olisto- with basal conglomerates unconformably strome and lenses of amphibolite included covers all the earlier formations, includ within the contact. The obduction event ing the Palaeozoic formations, indicating is also marked by erosion of the ophiolitic intense shortening before its deposition. unit and the deposition of conglomerates, Compression deformation is currently on shales, sandstones and siltstones. Poorly going and is manifested by numerous folds,

84 Teo(pu3UHecKuû. xypnoA Ne 4, T. 39, 2017 SOUTH CAUCASUS GEOSCIENCES mainly west-dipping thrusts and reverse location of the tectonic units suggests that faults cutting the Qom Formation, and by th e K hoy recent NW-SE dextral strike-slip faults. Gondwana-related basement was part This illustrates the continuous shortening of the South Armenian Block and that the and uplift (with intense erosion) resulting Khoy allochthonous ophiolites were ob- from the advanced stage of the collision ducted on it from the Amasia-Stepanavan- between Arabia and Eurasia. The structural Sevan-Hakari suture zone.

Reverse and thrust tectonic heritage in the south-east intermountain Ararat depression (Armenia)

institute of Geological Sciences, National Academy of Sciences of Republic of Armenia, Yerevan, Armenia 2University Côte d'Azur, UNS, CNRS, OCA, IRD Geoazur, Valbonne, France 3Université Côte d'Azur, UMR Géoazur, CNRS, Observatoire de la Côte d'Azur, IRD, Sophia Antipolis, France 3Nannofossils Biostratigraphy Consulting, Santok, Poland

The studies of the south-eastern part of the The secondary normal faults, superimposed Ararat basin and neighboring mountain and gravitational slopes processes and selective intermountain depressions of the Republic erosion complicate moreover the overall of Armenia, allow reevaluating of previous structure pattern. These processes continue researches and revealing tectonic processes up to date. developed since the Late Cretaceous conti The thrust and reverse tectonics form and nental collision according to recent geody develop asymmetric, oblique, fold structures, namic concepts. The Ararat basin structural cuestas with structural slops in back-limb and setting and tectonic evolution investigation intensive weathered foreland in fore-limb. is perspective for hydrocarbon traps identi The result of these faults activity is seen in fication. the Paleozoic substratum, newly discovered The thrust and reverse stress regime of the volcanic rocks (OIB type, probably associated study area was dominant during long period with the ophiolites) outcropping from Ararat from collision initiation, influencing farther depression alluvial and lacustrine Quaternary tectonics, complicated by strike-slip faulting. cover.

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Preliminary results of paleomagnetic study of flysch sequences in Eastern Crimea mountains

Institute of Geophysics, National Academy of Sciences of Ukraine, Kiev, Ukraine

The new dating of the Tavric flysch com that elongate ferromagnetic grains are pas plex at the Eastern Crimean Mountains sively rotated during deformation of rocks. [Sherem etetal., 2016] requires independent Palaeomagnetic measurements were car age determination of Crimea flysch sequenc ried out in the laboratory of the Institute of es. It has been proposed to use the paleomag Geophysics of the National Academy of Sci netic method taking into account that recent ences of Ukraine in Kiev. Specimens were paleomagnetic data from Crimea had been stepwise thermally demagnetized using an successfully applied both for tectonics [Qinku MMTD80 oven up to 600 °C. The demagne et al., 2013] and magnetostratigraphy [Gu- tization of specimens (thermal and alternating zhikov et al., 2012; Bakhmutov et al., 2016]. field (AF)) and all measurements were made The key task of our study is to distinguish the inside magnetically shielded rooms to mini paleomagnetic zones of normal and reverse mize the acquisition of present-day viscous polarity and their binding to the geological magnetization. After each heating step, the time scale considering the paleontological magnetic susceptibility (k) at room tempera and lithological markers. But the analysis of ture was measured by a MFK1 Kappabridge new data of micropaleontological complexes to estimate possible mineralogical changes. without additional geological information, Duplicate specimens were subjected to AF taking into account the frequent changes in demagnetization up to 100 mT using a LDA- magnetic polarity in the Jurassic-Early Creta 3Ademagnetizer. Demagnetization steps were ceous time span, shows some difficulty of this adjusted during thermal or AF procedures approach for our study. We have proposed from 10° to 50 °C and 10—20 mT, respec another approach — to distinguish the pri tively. The natural remanent magnetization mary magnetization and calculate paleopoles (NRM) of specimens was measured by JR-6 that are compared with expected reference spin magnetometer. Demagnetization results apparent polar wander path (APWP) of Eur were processed by multicomponent analysis of asia. Thus, we consider the main purpose of demagnetization path [Kirschvink, 1980] us our paleomagnetic studies is the definition of ing Remasoft 3.0 software [Chadima, Hrouda, paleo-latitudes of flysch sequences in Crime 2006]. AMS was measured by MFK-1 Kappa an Mountains. bridge, and magnetic anisotropy parameters The second objective of our research re were calculated with the Anisoft program. lates with study of anisotropy of magnetic During 2015—2016 field expeditions in susceptibility (AMS). Due to the presence Crimean Mountains we have examined 15 of ferromagnetic particles of non-isometric sites, and from 10 of them have collected form, it is assumed that magnetic structure the sandstones and argillites from flysch se was formed under the influence of some fac quence of Tavric(?) series for paleomagnetic tors, such as bottom currents-In structural ap analysis. Results from 7 sites (their location plications, AMS have been used to examine is shown in Fig. 1), mainly of 2015 collection, patterns of strain. An oversimplified view is were taken for further interpretation.

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In general, the samples from different sites After removal of this weak overprint, a second have different magnetic parameters and sta component with unblocking temperatures be bility to thermal and AF demagnetization tween 300 and 400—480 °C was calculated

Crimea |[Geological i:iwa«a map

Demerji Privetnoye Veseloye 3 Zelenogorie Lesnoye Black See 20 km Meganom Feodosiya

Fig. 1. Sites of sampling for paleomagnetic study in Eastern Crimea Mountains. showing no common regularities. So, during from the vector that decays linearly close to next data processing and selection of mag the origin. Several samples have unblocking netization components, some samples were temperature more than 500 °C. Taken into excluded from the data base and were taken account the high increases of susceptibility not suitable for further interpretation due to: above 400 °C we can't extract the more stable 1) weak NRM (<0.001 mA/m); 2) large MAD component decays linearly to the origin. So (>10°) of selection component; 3) unstable the ChRM (characteristic component of rema behavior during demagnetization; 4) strong nent magnetization) direction was calculated inconsistency to the rest of samples in the from the vector that decays linearly to the ori group. Despite the number of samples from gin of the orthogonal vector plots. each site was enough, the Q index of [Van Five sites (numbers 1—5 in the Fig. 1) show derVoo, 1990] could not be satisfied for most the ChRM direction corresponding to normal sites. Many samples show dramatic increase polarity; after correction for fold bedding ele of susceptibility during thermal demagneti ments it becomes more scattered. Palaeomag- zation in the range 300—400 °C. Some of the netic fold test show that all palaeomagnetic samples are characterized by a peak of the groups carry a post-folding remanent magne NRM at different temperatures, which indi tization. This result confirms the Early Cre cates significant changes in magnetic miner taceous remagnetization of sediments from als behavior during heating. other sites in Crimean Mountains reported Usually two NRM components could be by [Qinku et al., 2013]. distinguished during demagnetization. Alow The ChRM-directions of samples from unblocking temperature component, record sites 6 and 7, obtained from both high un ing probably a minor viscous origin, is re blocking temperature and high coercive com moved between 100—200 °C. The directions ponents, show normal and reversed polarities. of this component are scattered, but the mean The correction for folding suggests that the close to the present Earth's magnetic field. magnetization is primary. Site 7 was dated as

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Tithonian-Berriasian boundary, the ChRM- fined by a single stable component. To per directions have normal and reverse polarities form this procedure to our data we have to and confirmed the result of [Guzhikov et al., involve our new results on the collection of 2012] about primary magnetization of Titho- 2016 (mainly collected in western Crimean nian flysch near Feodosiya. Mountains). Now this collection is labora The tectonics implication of our results tory measured. is not clear because of the data shortage. The AMS data show typical sedimentary Meijers et al. (2010) considered the ChRM structure of sediments after bedding correc magnetization is primary and reported the tion. The minimum axis of the AMS ellipsoid Upper Jurassic palaeolatitudes in Crimea, is normal to bedding, while the direction of the which is inconsistent with the paleolatitudes maximum axis is NE-SW for sites 1-5, N-S for obtained in [£inku et al., 2013], which used site 6 and NW-SE for site 7. The directions of age and refernece palaeolatitude curve de maximum axis of AMS tensor will be compared rived from the APWP paths of Eurasia and with structural and tectonophysical data from Gondwana. Comparison of the average the area to define their possible connection. mean palaeomagnetic poles in the Triassic— In the case of the shape of the AMS tensor Upper Jurassic units of Crimea with that ex is related to tectonic deformation, the mea pected for the Eurasian APWP, suggests an surement of AMS in rocks of different ages age as post-Berriasian. For the most cases will allow us to define an upper age limit for the mean remagnetization directions are de- deformations.

References

Guzhikov A. Y., Arkad 'ev V. V., Baraboshkin E. Y., Bagae J. Roy. Astron. Soc. 62(3), 699—718. d ohlO .llll/ va M. I., Piskunov V K., Rud 'kod S. V, Perminov V A., j. 1365246X. 1980.Ш02601 .x. Manikin A. G., 2012. New sedimentological, bio-, and magnetostratigraphic data on the Jurassic- Chadima M., Hrouda F., 2006. Remasoft 3.0 — a user Cretaceous boundary interval of eastern Crimea friendly paleomagnetic data browser and analyzer. (Feodosiya). Stratigi. Geol. Coirel. 20,261—294. doi: Travaux Geophysiques XXVII, 20—21. 10.1134/S0869593812030045. Van der Voo R., 1990. The reliability of paleomag Qinku M. C„ Hisarli Z. M„ Orbay N., Ustadmer T., netic data. Tectonophysics 184, 1—9. https://doi. Hirt A. M., Kravchenko S., Rusakov O., Sayin N., org/10.1016/0040-1951(90)90116-P. 2013. Evidence of Early Cretaceous remagnetization in the Crimean Peninsula: a palaeomagnetic study Meijers M. J. M., Langereis C. G., van Hinsbergen D. J. J., from Mesozoic rocks in the Crimean and Western Kaymakci N., Stephenson R. A., Altmer D., 2010. Pontides, conjugate margins of the Western Black Jurassic-Cretaceous low paleolatitudes from the Sea. Geophys. J. Int. 195(2), 821—843. https//doi. circum-Black Sea region (Crimea and Pontides) due org/10.1093/gji/ggt260. to True Polar Wander. Earth Planet. Sei. Lett. 296, Bakhmutov V., Casellato C. E., Halasova E., Ivanova D., 210—226. doi: 10.1016/j.epsl.2010.04.052. Rehakova D., Wimbledon W. A. P.: 2016. Bio- and magnetostratigraphy of the upper Tithonian — Sheremet Y, SossonM., Müller C., Murovskaya A., Gin- lower Berriasian in southern Ukraine. Abstract tovO., Yegorova T, 2016. Key problems of stratigra JURASSICA XII Conference, 4th IGCP 632 meeting phy in the Eastern Crimea Peninsula: some insights and Workshop of the ICS Berriasian Working Group, from new dating and structural data. In: M. Sosson, April 19th—23rd, P. 20—22. R. Stephenson, Sh. Adamia (Eds.). Tectonic Evolu tion of the Eastern Black Sea and Caucasus. Geol. KirschvinkJ. L., 1980. The least-squars line and plane Soc. London Spec. Publ., 428. http://doi.org/10.1144/ and the analysis of paleomagnetic data. Geophys. SP428.14.

88 Геофизический журнал Ne 4, T. 39, 2017 SOUTH CAUCASUS GEOSCIENCES

Mesozoic geodynamic and paleoenvironmental evolution of the Tethyan realm preserved in the Lesser Caucasus

Université de Lille, CNRS, UMR8198 Evo-Eco-Paleo, Lille, France 2Universite' de Lille, CNRS, Université Littoral Côte d'Opale, Laboratoire d'Océanologie et de Géosciences, Lille, France institute of Geological Sciences, National Academy of Sciences of Republic of Armenia, Yerevan, Armenia 4Université Côte d'Azur, UMR Géoazur, CNRS, Sophia Antipolis, France

In the Lesser Caucasus (Armenia and South-Armenian Block, a Gondwana-derived Karabagh; Fig. 1) can be found remnants of terrain considered as the eastern extension a Tethyan oceanic realm that existed dur of the Tauride-Anatolide plate. The Tethyan ing the Mesozoic between Eurasia and the remains in the Lesser Caucasus are part of

E 44° E 45c 0 10 20 30 km N i A N 41°- Thrust Fault Normal Fault Strike slip Fault Volcanic cone

-N 40° □ □ Pliocene-Quaternary (volcanic and sedimentary rocks) □ □ Oligo-Miocene volcanogenic rocks □ Upper Jurassic, Cretaceous and Tertiary intrusions □ Paleocene-Eocene volcanogenic rocks □ Upper Cretaceous formations Eurasian (mainly sedimentary rocks) Margin □ Middle to Upper Jurassic volcanogenic series I Ophioiites

South Triassic and Jurassic series N 39° Armenian !=□ Paleozoic platform series (Devonian to Permian) Block Proterozoic series (gneisses-amphibolites) E 46c Fig. 1. Geological map of the Lesser Caucasus (after [Sosson et al.( 2010], modified), including the location of the key studied areas: A — Old Sotk Pass; B— Amasia; C — Dali. reo(pu3UHecxiiu JKypHOA № 4, T. 39,2017 89 INTERNATIONAL RESEARCH GROUP PROJECT an over 2,000 km long suture zone, running Fig. 2 synthesizes all available radio- through the northern part of Turkey towards metric and biochronological data from the Iran. As it is often the case, radiolaxites are Lesser Caucasus. It is likely that oceanic here associated with submarine lavas that are floor spreading was taking place during the considered to be part of an ophiolitic com Middle/Late Triassic between the South Ar- plex. Radiolarian biochronology of radiola- menian-Tauride-Anatolide plate and Eurasia. rites, combined with petrographic observa This is suggested by upper Triassic gabbros tions and geochemical analyses of ophiolitic dated in Karabagh [Bogdanovski et al., 1992] lavas, helps us to improve our understanding and an upper Triassic-Iiassic deep-sea sedi of the geodynamic and paleoenvironmental mentary sequence dated in the same area by evolution of this geologically complex region. radiolarians [Knipper et al., 1997]. Based on

Maas 70- Camp 80- Late 3 oil “ g o - Turon Ce no m 100- Alb 110-

120- Cretaceous Apt >• H3 Bar 130- PU Haut Val 140- Ber

150- 05 «-> —1(0 160- Oxf

"O 170- ■G Hath *35 § Aal rc kl 3 Toar 180- ' s Pliens 190- 1Z U Sinem 200- 201,3 [rrrr I Volcaniclastics Rhaet i l Intrusive rocks 210- 209,5 I—-——I (gabbro, tonalité, plagiogranite) 0> G Ophiolitic breccia J Nor 220- •••'1 Flysch Triassii 228,4 F Shallow water limestone 230- Carn

Fig. 2. Synthesis of all known ages (both biochronological and geochronological) for the ophiolitic rocks and their sedimentary cover in the Lesser Caucasus (after [Danelian et al., 2016], modified).

90 reoLake in age; the cherts do not contain the above Sevan (Fig. 1, C), bears a particular geody mentioned limestones and are much darker namic significance. It exposes a thick basaltic in color (more Mn-rich?). sequence that overlies layered dioritic cumu Finally, the microfossil record preserved lates intruded by a small plagiogranite body. in both the uppermost part of the shallow wa Based on igneous mineral chemistry and ter carbonate sequence and overlying flysch bulk rock geochemistry three major basaltic that crop out in the Vedi area (SE of Yerevan; groups were identified; it is likely that they are Fig. 1) establish that the initial stages of ob- separated by thin thrust zones. The contact duction of ophiolites onto the South-Arme- between the diorites and the overlying basalts nian Block took place during the Cenoma is cataclastic and underlined by hydrothermal nian (see [Danelian et al., 2014, 2016]).

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References

Asatryan G., Danelian T., Seyler M., Sahakyan L„ Ga- Danelian T., Asatryan G., Galoyan G., Sahakyan L„ loyan G., Sosson M., Avagyan A., Hubert B., Per Stepanyan J., 2016. Late Jurassic — Early Creta son A., Vantalon S., 2012. Latest Jurassic — Early ceous radiolarian age constraints from the sedimen Cretaceous Radiolarian assemblages constrain epi tary cover of the Amasia ophiolite (NW Armenia), at sodes of submarine volcanic activity in the Tethyan the junction between the Izmir-Ankara-Erzingan and oceanic realm of the Sevan ophiolites (Armenia). In: Sevan-Hakari suture zones. Int. J. Earth Sci. (Geol T. Danelian, S. Gorican (Eds.). Radiolarian biochro Rundsch) 105(1), 67—80. doi:10.1007/s00531-015- nology as a key to tectono-stratigraphic reconstruc 1228-5. tions. Bulletin de la Société Géologique de France 183, 319—330. doi: 10.2113/gssgfbull. 183.4.319. KnipperA. L., Satian M. A., Bragin N. Yu., 1997. Upper Bogdanovski O. G., Zakariadze G. S., Karpenko S. E, Zlo Triassic-Lower Jurassic Volcanogenic and Sedimen bin S. K., Pushhovskaya V. M., Amelin Y. V., 1992. tary Deposits of the Old Zod Pass (Transcaucasia). Sm-Nd age of the gabbroids of a tholeiitic series of Stratigraphy, geological correlation 3, 58—65 (in the ophiolites of the Sevan-Akera zone of the Lesser Russian). Caucasus. Rep. Acad. Sci. Russia 327, 566—569 (in Russian). Sosson M., Rolland Y., Muller C., Danelian T., Melkon- yan R., Kekelia S., Adamia S., Babazadeh V., Kan- Danelian T, Zambetakis-Lekkas A., Galoyan G„ Sos garli T., Avagyan A., Galoyan G., Mosar J., 2010. son M., Asatryan G., Hubert B., Grigoryan A., 2014. Reconstructing Upper Cretaceous (Cenomanian) Subductions, obduction and collision in the Lesser paleoenvironments in Armenia based on Radiolaria Caucasus (Armenia, Azerbaijan, Georgia), new in and benthic Foraminifera; implications for the geo sights. In: M. Sosson, N. Kaymakci, R. Stephenson, dynamic evolution of the Tethyan realm in the Lesser F. Bergerat, V. Starostenko (eds). Sedimentary Basin Caucasus. Palaeogeography, Palaeoclimatology, Pa- Tectonics from the Black Sea and Caucasus to the laeoecology413,123—132. https://doi.Org/10.1016/j. Arabian Platform. Geol. Soc. London Spec. Publ. palaeo.2014.03.011. 340, 329—352.

The obduction process: What extent? What timing? What cause(s)? The study of the northern branch of Neotethys in Anatolia and the Lesser Caucasus (Turkey and Armenia)

departm ent of Earth Sciences, University of Geneva, Geneva, Switzerland 2Université Côte d'Azur, Géoazur, UNS , CNRS, IRD, Observatoire de la Côte d'Azur, Sophia Antipolis, France

Worldwide within mountain ranges the Lesser Caucasus and NE Anatolia are prime presence of slivers of preserved oceanic lith examples of this phenomenon with tectonic osphere known as ophiolites evidence a tec transport (> 150 km) of fragments of oceanic tonic process responsible for their emplace lithosphere towards the south on top of the ment on top of the continental crust called South Armenian Block-Tauride-Anatolide obduction. The first order anomaly inherent Platform along the entire continental marge to this phenomenon is that dense rocks (p>3) (>1000 km) (Fig. 1). The multidisciplinary ap end up on top of less dense rocks (p«2.7). The proach used throughout the study of these driving forces responsible and consequent/ ophiolites yielded clues specifying the evolu accompanying processes for such a tectonic tion of the Northern Neotethys Ocean before oddity remain uncertain. The ophiolites of the and around the time of ophiolite emplace-

92 Teo(pu3UHecKuû. xypnoA Ne 4, T. 39, 2017 SOUTH CAUCASUS GEOSCIENCES

40°E 42°E 44°E 46°E 48°E 50°E Suture zone Ophiolite Former extent Main thrust outcrops of obduction

Eurasian margin Obduction Araks Vedi Sevan Lake Sevan-Akera suture basin и__ ,, ^ contact Plio-quaternary basin and ophiolites

Crystalline basement 10 km Cenozoic thrusts 50 km

Fig. 1. Tectonic map of the Middle East-Caucasus area, showing the main blocks and suture zones, and corre sponding crustal-scale section showing the obduction, after [Hassig et al.r 2013]: EAF — East Anatolian Fault; I AES — Izmir—Ankara—Erzincan Suture; KB — Kirshehir Block; MM — Menderes Massif; NALC — North-East Anatolia—Lesser Caucasus domain (zone of ophiolite obduction); SAB — South Armenian Block; V — volcanic arc of Eurasian margin of Pontides. * position of cross-section (below). Lower panel: Upper-crustal-scale geological section of the NALC showing the geometry of the obduction front propagated towards the south and its rooting into the Sevan Akera suture to the north, below the Eurasian margin (see [Rolland et al., 2012]).

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N Lesser Caucasus-Pontides Northern ,^rc SAB-TAP OlB-type magmatism neotethys E u ra s ia n /U ivlargin v 1

Thrust faults Mantle upwelling

'Amphibolites / Gravity sliding (passive obduction) Clastic sedimentation

90 Ma c - _ __ Gravity sliding (passive obductiojiJ. Normal faults

_85Ma __ _

Fig. 2. Conceptual model of the obduction process in the NALC: a — situation in the Early Cretaceous showing the convergence of SAB—TAP (South Armenian Block—Taurides Anatolides) with the Eurasian margin, the onset of mantle upwelling and heating of the oceanic lithosphere at 115 Ma, b — triggering of obduction, due to the blocking of the northern subduction zone and the increase in buoyancy of the oceanic lithosphere, c— thickening of the continental crust below the obduction, erosion and the onset of passive obduction [Lagabrielle et al., 2013] by gravity sliding of the ophiolites on the flexural basin, d — transition from a contractional to an extensional regime due to renewed subduction. Mantle thinning and withdrawal leads to the exhumation of the continental crust.

ment (90 Ma), consequently the obduction the thinning of the ophiolitic nappe, under event. Our findings strongly suggest common plating of underthrusted continental litho emplacement of all the ophiolites of the study sphere and exhumation of continental crust. area as a thrust sheet of Middle Jurassic oce Thermal rejuvenation is supposed for the anic lithosphere, ~70—80 Ma old at obduc ophiolites of the Caucasus s.l. argued by al tion onset. This would be one of the biggest kaline lavas emplaced on the sea floor prior preserved ophiolite nappe complexes in the to the obduction event during the Late Cre world (outcropping in a mountain range). taceous (117 Ma). The resulting seamounts Numerical modelling validated, firstly; the and/or oceanic plateaus of this magmatism hypothesis that emplacement of such an ophi- would then have blocked the north-dipping olitic nappe is due to particular thermal con subduction zone father north under Eurasia ditions. For old oceanic lithosphere to obduct upon their entree and this until the end of the it needs to be in a thermal state close to that of obduction event. The obduction event on the young oceanic lithosphere (0—40 km thick). South Armenian Block—Tauride—Anatolide Secondly, numerical modelling showed that Platform is synchronous along the Eurasian the progression of obduction over a great dis margin from the Pontides to the Somkheto- tance and current position of the ophiolites Karabakh. Reactivation of the north-dipping far over the continental margin could be ex subduction zone under Eurasia is compat plained by post-compression extension. This ible with traction on the obducted oceanic switch in tectonic regime is responsible for lithosphere responsible for its mantle thin

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ning, continental lithospheric underplating ite-free underthrusted continental margin can and continental crust exhumation. Thus the result from a combination of reheating of the propagation of thin obductions according to oceanic lithosphere and far-field plate kine the «flake tectonics» concept over an eclog- matics (Fig. 2).

References

Hâssig M., Rolland Y, Sosson M., Galoyan G., Sahaky- of large ophiolitic sheets: the New Caledonia ophio- an L, Topuz G., Çelik O. E, Avagyan A., Müller C., lite (SW Pacific) as a case study? Bull. Soc. Géol. 2013. Linking the NE Anatolian and Lesser Cauca Ft. 184, 545—556. doi: 10.2113/gssgfbull. 184.6.545. sus ophiolites: evidence for large scale obduction of oceanic crust and implications for the formation Rolland Y., Perincek D., Kaymakci N., Sosson M., Bar of the Lesser Caucasus-Pontides Arc. Geodin. Acta rier E., Avagyan A., 2012. Evidence for~80—75 Ma 26, 311—330. http://dx.doi.org/10.1080/0985311L2 subduction jump during Anatolide—Tauride—Ar 013.877236. menian block accretion and ~48 Ma Arabia-Eur- asia collision in Lesser Caucasus-East Anatolia. J. Lagabrielle Y, Chauvet A., Ulrich M., Guillot S., 2013. Geodyn. 56-57, 76—85. https://doi.Org/10.1016/j. Passive obduction and gravity-driven emplacement jog.2011.08.006.

Ore-forming processes in basite-ultrabasite complexes of ophiolites of the Lesser Caucasus

Institute of Geology and Geophysics, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan

The basite-ultrabasite complex of ophiol out of ultrabasites at early mantle metamor ites was formed in the result of many-stage phism and is reaccumulation under the hydro- mantle-crust evolution of mantle substance. thermal solutions of gabbro-plagiogranite All this was stipulated by different genesis intrusive. Mercury deposits in ultrabasites processes forming deposits of chromite, gold complex are of hydrothermal type. Deep and mercury Magmatic chromites are connected faults of this belt activation in postcollision with mantle ultrabasite part of ophiolite profile period serve as leading channels of Mio- formed in the process of oceanic crust forma Pliocene acid volcanism and mercury-con- tion accompanied with gabbro and tholeitic vol- tent hydrothermal solutions. Serpentinized canism. Mantle differentiation of ultrabasite peridotites in these processes played the substance in the process of its high-tempera role of a screen. However regeneration of early ture viscous displacement was one of the fac deeper deposits could also occur. Different types tors of chromite isolation. Gold deposits in of ore-forming activity connected with forming of basite-ultrabasites of ophiolites are related ophiolites reflect the complex spatial correlation to autometamorphic process and lay on hydro- between the processes of ore formation, evolu thermal metasomatic processes. Combination tion of ultrabasits and geodynamical regime of of these processes caused extraction of gold the region.

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Petrology and geochemistry of basaltic series in Cenozoic volcanic belts of Gaucasus

Institute of Geology and Geophysics, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan

Alpine stage of tectonic-magmatic de cient lithospheric plates of Eurasia and velopment of Caucasus is considered in Afroarabia. As Mesozoic-Cenozoic pe sphere of complete geodynamic process riod is characterized by the manifestation caused by the correlation of Tethys oce anic crust with continental margins of an-

Fig. 2. Normalized multicomponent diagram of the volcanic rock complexes of the Middle Eocene (Talish, Fig. 1. Normalized multicomponent diagram of the Adjara-Trialety and Geychay-Akerin zones): 1 — tole volcanic rock complexes of the Middle Eocene (Yere- itic basalt, middle (16); 2 — sub-alkalinetrekhibasalt, van-Ordubad zone): 1 — toleitic basalt (13); 2 — calc- middle Eocene (17); 3 — alkaline melafonolite, Oligo alkaline basalt (14); 3 — Trakhibasalt (15). cène—Miocene (18).

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Rb K La Nd Hf Ti Yb Co Cr i— t— i— i— i— i— i— i—i— i— i— i— i— i— i— i— i— i— i Ba Sr Ce Sm Eu Tb Lu Ni Rb K La Nd Hf Ti Yb Co Cr Fig. 4. Normalized multicomponent diagram of the vol Hh—i—i—i—i—i—i—i—i—i—i—i—i—i—i—i—h H Ba Sr Ce Sm Eu Tb Lu Ni canic rock complexes of the Late Pliocene - Holocene: 1 — low potassium dolente, Trans-Caucasus rise (21); Fig. 3. Normalized multicomponent diagram of the 2 — trakhiandesibasal, Gegam (22); 3 — trakhiandesi- volcanic rock complexes of the Neogene (Yerevan-Or- basal, Kelbajar (23); 4 — basanite, Kafan, Zangezur su dubadzone): 1— andesidasite (19); 2 — andesite (20). ture zone (24). reo(pu3UHecxiiu JKypHOA № 4, T. 39,2017 97 INTERNATIONAL RESEARCH GROUP PROJECT

Fig. 5. Correlation of rare elements in Mz (a) and KZ (b, c) in basites of the Lesser Caucasus.

At Late Pliocene—Quarternary stage Change of low-potassic low-Ti, deplited volcanism is presented by tholeitic by light REE of Early Cenozoic volcanites by (La/Yb=7.5), subalkaline (La/Yb=40,5) rather enriched light REE and elements with and alkaline (La/Yb=66-j-70) basalts which large ionium radii of Late Cenozoic volcanites are characterized by the increazing accu can be connected with the change of geodin- mulation of Kr Rbr Bar Srr light REEr Ni, amics of the region from the active continental Co, Cr. In formation of them one can observe margins to activized area of completed old- the change of fusion level of magmatic melt ing, accompanied by the rise of fusion front, from mantle for the first (tholeitic basalt, ol transported from depleted abnormal mantle in ivine basanites) to the mantle crustal, inter the sphere of metasomatically overdone up mediate — trachyandesite-basalts (Fig. 5). per mantle in the base of lithospheric plates.

Active geodynamics of the Caucasus

Institute of Geology and Geophysics, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan

We present GPS observations of crustal zone is accommodated by the Greater deformation in the Africa-Arabia-Eurasia Caucasus Fold-and-Thrust Belt (GCFTB) zone of plate interaction, and use these along the southern edge of the Greater observations to constrain broad-scale tec Caucasus Mountains (Fig. 1). tonic processes within the collision zone The eastern GCFTB appears to bifur of the Arabian and Eurasian plates. Within cate west of Baku, with one branch follow this plate tectonics context, we exam ing the accurate geometry of the Greater ine deformation of the Caucasus system Caucasus, turning towards the south and (Lesser and Greater Caucasus and inter traversing the Neftchala Peninsula. Asec- vening Caucasian Isthmus) and show that ond branch (or branches) may extend di most crustal shortening in the collision rectly into the Caspian Sea south of Baku,

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44°N

42°N

40°N

38°N

36°N 40°E 42°E 44°E 46°E 48°E 50°E

Fig. 1. GPS velocities and 95 % confidence ellipses w.r.t. (with respect to) Eurasia for the eastern AR-EU collision zone. likely connecting to the Central Caspian 47—49°E). Parts of this segment of the Seismic Zone (CCSZ). We model defor fault broke in major earthquakes histori mation in terms of a locked thrust fault cally (1191, 1859, 1902) suggesting that that coincides in general with the main significant future earthquakes (M~6-s-7) surface trace of the GCFTB. We consider are likely on the central and western seg two end-member models, each of which ment of the fault. We observe a similar tests the likelihood of one or other of the deformation pattern across the eastern branches being the dominant cause of ob end of the GCFTB along a profile cross served deformation (Fig. 2). ing the Kur Depression and Greater Cau Our models indicate that strain is ac casus Mountains in the vicinity of Baku. tively accumulating on the fault along Along this eastern segment, a branch of the ~200 km segment of the fault west of the fault changes from a NW-SE striking Baku (approximately between longitudes thrust to an N-S oriented strike-slip fault reo(pu3UHecxiiu JKypHOA № 4, T. 39,2017 99 INTERNATIONAL RESEARCH GROUP PROJECT

0 El

® 0

Fig. 2. Plots of transverse (A) and parallel (B-E) components of velocities versus distance along the profilesshown in Fig. 1. (or in multiple splays). Similar deforma that major earthquakes may also occur in tion pattern along the eastern and central eastern Azerbaijan. However, the eastern GCFTB segments raises the possibility segment of the GCFTB has no record of wo reo

Active tectonics and focal mechanisms of earthquakes in the pseudosubduction active zone of the North- and South-Caucasus microplates (within Azerbaijan)

Institute of Geology and Geophysics, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan

The Greater Caucasus was formed dur Within the territory of Azerbaijan the ing the last stage of tectogenesis in a geo tectonic stratification of the Greater Cau dynamic environment of the lateral com casus marginal sea alpine complex is dis pression, peculiar to the zone of pseudo tinguished in the structure of the South subduction between Northern and South ern Slope zone (megazone). Within the ern Caucasian continental microplates. Its megazone different-scale and different- present structure was formed as a result age cover-thrust complexes — Tufan, Sa- of horizontal movements during different rybash, Talachay-Duruja, Zagatala-Dibrar phases and sub-phases of Alpine tecto and Govdagh-Sumgayit—were identified genesis (from late Cimmerian to Walakh- and described. Allocated beneath accre ian). The Greater Caucasus is generally tionary prism of the Southern Slope, the considered as a zone where (along Zangi autochthonous bedding is presented by deformation) the insular arc formations of Mesozoic-Cenozoic complex of the north the Northern edge of the South Caucasian ern Vandam-Gobustan margin (mega microplate thrust under thick Mesozoic- zone) of the South-Caucasus microplate, Cenozoic complex composed of marginal which is in its' turn crushed and lensed sea deposits of Greater Caucasus. The into southward shifted tectonic micro last, in its turn, has been pushed beneath plates gently overlapping the northern the North-Caucasus continental margin flank of Kura flexure along Ganykh-Ay- of the Scythian plate (Epihersinian plat richay-Alat thrust. form) along the Main Caucasus Thrust. Formation of folded-cover structure As a result of the underthrusting, the ac of the Greater Caucasus accretionary cretion prism compressed between the prism is studied within the geodynamic indicated faults, was formed. model of intracontinental C-subduction

Teo(pii3imecKiiü xcypHOA Ns 4, T. 39, 2017 101 INTERNATIONAL RESEARCH GROUP PROJECT

(pseudo-subduction) under pressure of tion of the earth crust, within the structure the advancing northward Arabian plate. of which the earthquake cores are con This concept for the Caspian-Caucasian- fined mainly to an intersection knots of Black Sea region is justified by a number the ruptures with various strike, or to the of researches of the region. The described platitudes of deep tectonic failures and process continues up at the present stage lateral shifts along unstable contacts of of alpine tectogenesis as demonstrated by the substantial complexes with different real-time GPS survey. Monitoring of the competency. distribution of horizontal shift velocity Types of focal mechanisms in general vectors, produced during 1998—2016 by correspond to the understanding of geo GPS geodesic stations in Azerbaijan, in dynamics of the microplates convergent dicates considerable (up to 29 mm/year) borders, where the entire range of focal north-northwestward shifting velocity mechanisms, from normal-fault to up of the southwestern and central parts of thrust, is observed. At the contemporary South-Caucasus microplate, including stage of tectogenesis the maximum seis territories of the southeastern part of Less mic activity is indicated in structures of er Caucasus, Kura depression and Talysh. the northern flank of South-Caucasus mi At the same time, within the microplate's croplate controlled by Ganykh-Ayrichay- northeastern flange confined to Vandam- Alat deep overthrust of the «general Cau Gobustan megazone of Greater Caucasus, casus strike» in the west, and submeridi velocity vectors reduce by 6—13 mm/year, onal right-slip zone of the West-Caspian while further to the north, on a hanging fault in the east of the Azerbaijani part of wall of Kbaad-Zangi deep underthrust, Greater Caucasus. e.g. directly within the boundaries of ac Under lateral compression the small- cretionary prism the velocity becomes as scale blocks that constitute the earth crust low as 0—6 mm/year (2010—2016 data). in this region become reason for the cre In general, the belt's earth crust reduc ation of transpressive deformations, which tion is estimated as 4—10 mm/year. This combine shift movements along limiting phenomenon reflects consecutive accu transversal deformations with compres mulation of elastic deformations within sion structures to include general Cau pseudo-subduction interaction zones casus strike ruptures. Such regime leads between structures of the northern flank to the generation of multiple concentra of South-Caucasus microplate (Vandam- tion areas of the elastic deformations con Gobustan megazone) and the accretion fined to mentioned dislocations and their ary prism of Greater Caucasus. articulation knots. It is just the exceeded The ongoing pseudo-subduction is in ultimate strength of the rocks that causes dicated by unevenly distributed seismici energy discharge and brittle destructions ty by depths (seismic levels of 2—6,8—12, (according to stick-slip mechanism) in 17—22 and 25—45 km): distribution anal such tectonically weakened regions of ysis of the earthquake cores evidences the the southern slope of Azerbaijani part of existence of structural-dynamic interre Greater Caucasus. lation between them and the subvertical At the contemporary stage of tecto and subhorizontal contacts in the earth genesis the maximum seismic activity is crust. Horizontal and vertical seismic zon indicated within northern flank of South- ality is explained from the viewpoint of Caucasus microplate controlled by Gan- block divisibility and tectonic stratifica ykh-Ayrichay-Alat deep overthrust of the

102 Teo(pu3UHecKuû. xypnoA Ne 4, T. 39, 2017 SOUTH CAUCASUS GEOSCIENCES

Legend

Guton ^ I lf rulin' faillis seen on surface Lagodckhi 3 6 4 & • kf ...... buried anti-Caucasian direction __ _ buried Caucasian direction

Earthqmikrs

M > 5.0

Balakan Q ;

Y 15

Suhmeridianal faults: 1 - Khimrikh - Khalatala 2 - Tinovroso - Kadak siHMatmids faults: 3-Bufanygchay- Verkbiyan ^-Mazymgaryshan -Katekh

Faults of North - East trend: Longitudinal faults: 4 - Balakan 13 — Zangi 5 - Katekhchay 14 - Shambul - Ismayilli 6 - Zagatala 15 - Dashuz - Amirvan 7 - Meshlesh &-Talachay- Lalali Earthquake clusters: 9 - Kish I - Balakan 1 0 - Shaki II -Zagatala 11 - Gohmud - Salyakhan III - Shaki

Fig. 1. Allocation of earthquake foci zones of the North-Western Azerbaijan.

«general Caucasus strike» in the west, and tersection knot of the faults with various submeridional right-slip zone of the West- strikes, and is located in the upper part Caspian fault in the east of the Azerbai of Pre-Jurassic basement. Seismic event jani part of Greater Caucasus. This fact is is mainly related to activity of Khimrikh- particularly proved by earthquakes which Khalatala fault with submeridional strike, took place in May and December, 2012 in which in turn led to activation of connect Zagatala, Shaki and Balakan (Fig. 1). ed northeastern Balakan and sublatitudi- Zagatala earthquake. Focal zone of nal Mazymgaryshan-Katekh dislocations. the earthquake is confined to a complex Discharge of seismic energy occurred in intersection knot of different strike faults, most granulated zones confined to the in and is located in Pre-Jurassic basement. tersection knots of these dislocations with The main shock is related with activity faults of the general Caucasus strike. of Zagatala fault with northwestern strike Shaki earthquake. The focal zone of which caused activation of connected dis the earthquake located in the upper part locations. of Pre-Jurassic basement. Seismic event Balakan earthquake. Focal zone of the is connected with activity of subvertical earthquake is confined to a complex in faults with northeastern strike. Discharge

Teo(pu3UHecKiiu JKypHOA № 4, T. 39,2017 103 INTERNATIONAL RESEARCH GROUP PROJECT of seismic energy occurred in most granu slip type movements in the earthquake lated zones confined to the intersection foci. Only in four cases were strictly up knots of these dislocations with faults of thrust and upthrust-overthrust type move the general Caucasus trace. ments established; On the basis of the spatial-temporal - hypocenters of major seismic impacts analysis of the earthquake foci distribu (M=4.5h-5.7) and the absolute majority of tion with M > 3 for the instrumental pe aftershocks are confined to the surface of riod of observations (1902—2013), we es the pre-Jurassic basement or its depths tablished the dynamics of seismic activity (up to 20 km); on the southern slope zone of the Greater - most of hypocenters are confined to a Caucasus the following are defined: sloping strip which subsides in the north - the epicenters spatial distribution ern azimuths, identified with the zone of demonstrates that the above mentioned Ganykh-Ayrichay-Alat deep overthrust events are confined to the transverse and its flakes; (northwestern, northeastern, and sub - in general, the seismic activity of a meridional strike) disjunctive disloca mentioned period is explained by accu tions. However, epicentral zones are of a mulation of lateral compression stresses General Caucasus strike, dislocated along and their later discharge in an under and to the north of the deep upthrust. Both thrust articulation line from the Middle transverse and longitudinal dislocations Kur and Vandam tectonic zones along the are mapped by a complex of seismic and Ganykh-Ayrichay-Alat deep overthrust; electrical reconnaissance methods. They - lateral compression first contributed are characterized as a natural southern ex to the creation of transpressional failures tension of the fault-slip type disjunctive along the displacement planes of vari zones that outcrop in the mountainous area ous-strike transverse dislocations, and where structural-substantial complexes of the energy discharge in most granulated an accretionary zone come to the surface; and weakened areas was confined to the - focal mechanisms of events in the intersection knots of these dislocations separate groups reveal different, mainly between each other and with the deep close-to-vertical, planes of fault and fault- overthrust with its northern rear flakes.

Active tectonics and focal mechanisms of earthquakes in the pseudosubduction active zone of the North and South Caucasus microplates (within Azerbaijan)

Institute of Geology and Geophysics, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan

The Greater Caucasus was formed during peculiar to the zone of pseudo-subduction be the last stage of the tectogenesis in a geody tween the Northern and Southern Caucasian namic environment of the lateral compression, continental microplates. Its present structure

104 Teo(pu3UHecKuû. xypnoA Ne 4, T. 39, 2017 SOUTH CAUCASUS GEOSCIENCES was formed as a result of horizontal move 17—18 mm/year) north-northwestward shift ments during different phases and sub-phases ing velocity of the southwestern and central of Alpine tectogenesis (from late Cimmerian portions of the South Caucasus microplate, to Valakhian). The Greater Caucasus is gen including the areas of the southeastern part erally considered as a zone (along Zangi de of the Lesser Caucasus, Kura depression and formation) where the insular arc formations Talysh. At the same time, within the micro of the Northern edge of the South Caucasian plate northeastern flange confined to Van microplate thrust under thick Meso-Cenozoic dam-Gobustan megazone of Greater Cau complex composed of marginal sea deposits casus, velocity vectors reduce by 8—12 mm/ of Greater Caucasus. The latter in its turn, year, while further north, on a hanging wall has been pushed beneath the North-Cauca- of the Kbaad-Zangi deep underthrust, e.g. sus continental margin of the Scythian plate directly within the boundaries of the accre along the Main Caucasus Thrust. As a result tionary prism, the velocity becomes as low as of the underthrusting, the accretion prism 0—4 mm/year (2010—2012 data). As a whole compressed between the indicated faults, the Earth's crust contraction within this belt was formed. is estimated equal to 4—10 mm/year. Within the territory of Azerbaijan the tec This phenomenon reflects consecutive tonic stratification of the Greater Caucasus accumulation of elastic deformations within marginal sea alpine complex is distinguished pseudo-subduction interaction zones be in the structure of the Southern Slope zone tween structures of the northern flank of the (megazone). Within the megazone different- South Caucasus microplate (Vandam-Gobust scale and different-age cover thrust com an megazone) and the accretion prism of the plexes — Tfanskiy, Sarybashsky, Talachay- Greater Caucasus. Durudzhinskiy, Zagatala-Dibrar and Govdag- The ongoing pseudo-subduction is indi Sumgayit — were identified and described. cated by unevenly distributed seismicity by Allocated beneath the accretionary prism of depths (at 2—6, 8— 12,17—22 and 25—45 km the Southern Slope, the autochthonous bed depth): distribution analysis of the earth ding is presented by Meso-Cenozoic complex quake foci evidences the existence of struc of the northern Vandam-Gobustan margin tural-dynamic relation between them and the (megazone) of the South-Caucasian micro subvertical and subhorizontal contacts in the plate, which, in its turn, crushed and lensed Earth's crust. Horizontal and vertical seismic into southward shifted tectonic microplates zoning is explained from the viewpoint of gently overlapping the northern flank of Kura block structure and tectonic stratification of flexure along the Ganykh-Ayrichay-Alyat the crust, where the earthquake foci are con thrust. fined mainly to intersection nodes of faults of Formation of the folded-cover structure different strike, or to the planes of deep tec of the Greater Caucasus accretionary prism tonic faults and lateral displacements along is studied within the geodynamic model of unstable contacts of substantial complexes intracontinental S-subduction (pseudo-sub- with different competency. duction) under pressure of the advancing Types of focal mechanisms in general cor northward Arabian Plate. This concept for the respond to the understanding of geodynam South-Caspian-Caucasian-Black Sea region ics at the convergent margins of microplates, is justified by a number of researches of the where the whole range of focal mechanisms, study region. The proposed process continues from normal faults to overthrusts, is observed. up to the present stage of Alpine tectogenesis Under lateral compression the small-scale as it follows from real-time GPS survey [Kad- blocks that constitute the crust in this region irov et al., 2008]. Monitoring of distribution become a reason for creation of transpres- of horizontal shift velocity vectors, produced sive deformations, which combine strike-slip during 1998—2012 by GPS geodetic stations movements along transversal faults limiting in Azerbaijan, indicates considerable (up to the blocks with compression structures to

Teo(pii3imecKiiü xcypHOA Ns 4, T. 39, 2017 105 INTERNATIONAL RESEARCH GROUP PROJECT include general Caucasus strike faults. Such knots of these dislocations with faults of the a regime leads to generation of multiple general Caucasus trace. places of localization of elastic deformations Study of the space-time sequence of the confined to mentioned dislocations and their earthquakes of different magnitudes in each articulation nodes. It is just the exceeded ulti seismic zone allows us to draw the following mate strength of the rocks that causes energy conclusions: discharge and brittle deformations (according - the spatial distribution of foci demon to strike-slip mechanism) in such tectonically strates that the earthquakes are confined weakened regions of the southern slope of to the transverse (NW, NE and ~NS strike) Azerbaijan part of the Greater Caucasus. faults. However, the epicentral zones have a At the contemporary stage of tectogene- general strike similar to that of Greater Cau sis the maximum seismic activity is released casus, dislocated along and to the north of the within the structures at the northern flank deep overthrust. Both transverse and longitu of South Caucasus microplate controlled by dinal dislocations are mapped by seismic and Ganikh-Ayrichay-Alyat deep overthrust of electrical surveys. They represent the south «general Caucasus strike» in the west, and ern extension of the fault zones that outcrop by ~N-S right-slip zone of the West-Caspian in the mountain area where accretion zone fault in the east of the Azerbaijan part of the rock complexes come to the surface; Greater Caucasus. - focal mechanisms of events of separate This fact is particularly proved by the groups reveal different, mainly near vertical, earthquakes which occurred in May and De planes of fault in the earthquake foci. Only cember, 2012 in Zagatala, Sheki and Balakan. in four cases there were determined the over Zagatala earthquake. Focal zone of the thrusts strictly directed upwards; earthquake is confined to a complex inter - the foci of major strong earthquakes section knot of different strike faults, and is (M=4.5-h5.7) and the majority of the after located in the Pre-Jurassic basement. The shocks are confined to the surface of the main seismic event is related with activity of pre-Jurassic basement at the depths down to Zagatala fault of northwestern strike which 20 km; caused activation of connected dislocations. - most of foci are confined to a sloping Balakan earthquake. Focal zone of the strip which subsides in the northern direction, earthquake is confined to a complex intersec identified with the zone of Ganikh-Ayrichay- tion knot of the faults with various strikes, and Alyat deep overthrust and its flakes; is located in the upper part of the Pre-Jurassic - in general, the seismic activity of the men basement. Seismic event is mainly related to tioned period is explained by accumulation activity of Khimrikh-Khalatala fault of ~N-S, of lateral compression stresses and their later strike, which, in turn led to activation of re discharge in the junction zone of the Middle lated N-E Balakan and ~ E-W Mazimgarishan- Kura and Vandam tectonic zones along the Katekh faults. Release of seismic energy oc Ganikh-Ayrichay-Alyat deep overthrust; curred in most granulated zones confined to - lateral compression first contributed to the intersection nodes of these dislocations the creation of transpressional failures along with faults of general Caucasus strike. the displacement planes of various strike Sheki earthquake. The focal zone of the transverse dislocations, and the energy dis earthquake is located in the upper part of the charge in most granulated and weakened Pre-Jurassic basement. Seismic event relates areas was confined to the intersection nodes with activity of subvertical faults of NE strike. of these dislocations between each other and Discharge of seismic energy occurred in most with the deep overthrust with its' northern granulated zones confined to the intersection flakes.

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References

Kadirov E, Mammadov S., Reilinger R., McCIusky S., Philip H., Cistemas A., Gvisiani A., Gorshkov A., 1989. 2008. Some new data on modem tectonic deforma The Caucasus: An actual example of the initial stag tion and active faulting in Azerbaijan (according to es of continental collision. Tectonophysics 161(1-2), Global Positioning System Measurements). Proceed 1—21. doi: 10.1016/0040-1951(89)90297-7. ings Azerbaijan National Academy of Sciences. The Sciences of Earth (1), 82—88.

Paleo- and recent stress regimes of the Crimea Mountains based on micro- and macroscale tectonic analysis and earthquakes focal mechanisms

institute of Geophysics, National Academy of Sciences of Ukraine, Kiev, Ukraine 2Université Côte d'Azur, UMR Géoazur, CNRS, Sophia Antipolis, France 3Aix-Marseille Université, Aix-en-Provence, France

The Crimea Mountains (CM) belongs to entation (trends) of the thrusts and fold axis the northern branch of the Alpine Belt. Being developed in the Eastern CM and its nearest the northwestern continuation of the Great offshore area [Sheremet et al., 2016a, b]. Thus, er Caucasus (GC) and a part of the inverted the westernmost part of the Eastern CM is northern margin of the Black Sea (BS), the characterized by the NW-oriented compres CM region shows the similarities in structural sion, while its eastern part is characterized by development of both the domains, implying NNW-SSE direction of the shortening. Two the common tectonic evolution of the GC — stages of the shortening during the Cenozo Eastern BS area. ic were defined based on the major Middle In the current study, we focus on the Meso- Eocene unconformity: the age-frames of the Cenozoic time-span of tectonic evolution of earliest compression stage is defined as the the CM and the adjacent BS margin in order Paleocene—Middle Eocene time, whereas the to define paleo- and recent stress regimes youngest compression is suggested in the Oli- alternated during its tectonic history, based gocene—Middle Pliocene. on the recent geological field observations, Reverse regime. For the majority of sites the results of structural analysis, the micro- in the CM we obtained the large display of tectonic data and the analysis of focal mecha reverse regimes with trending N-S, NNW- nisms of the earthquakes. Thus, the main pur SSE and NW-SE. According to orientation of pose of our study is to find and investigate the thrust front defined offshore, the NW-SE the correlation between the stress field and orientation of the Oj compressional axis pre the large-scale deformation structures with vails in the CM during the formation of the subsequent determination of major tectonic main compressional structures. It also has a events. point for the NE-SW oriented structures of the The Cenozoic compression. The major southwestern part of the Kerch Peninsula (KP). direction of the shortening during the Ce In the area of Sudak the N-S shortening nozoic was defined in regards of main ori was defined. This N-S and NNE-SSW trend of

Teo(pii3imecKiiü xypnoA Ns 4, T. 39, 2017 107 INTERNATIONAL RESEARCH GROUP PROJECT shortening can be traced in KP where the cor relict slickensides, tectonic breccias and trac responding structures overthrust those, which es of attached marine organisms, confine the were formed under the NW-SE compression. Early Cretaceous depressions within the CM. Moreover, the reverse regimes with Oj trend The corresponding stress fields are character ing NNE-SSW characterize the structures of ized by N-S and NNE-SSW trend of the a3 the Western CM. Thus, the first compression, extensional axis in the Western Crimea and which follows the Cretaceous extension stage, by the NE-SW orientation of the ct3 axis in was the one of, mainly, NW-SE orientation. the Eastern CM. New stratigraphy dating and Strike-slip regime. The analysis of the structural analysis in the Western CM indi structural patterns in the Eastern CM re cate a later extensional stage for the Western veals several faults of NE-SW and NNE-SSW BS (Valanginian-Barremian) [Murovskaya et trends with left-lateral strike-slip movements al., 2014] than for its Eastern part when the along them. These strike-slip faults cut sev latter experienced the loading of the GC ba eral thrusts and displaced laterally the thrust sin since the Middle Jurassic. front in several places. In other cases, there 2. The second type of extensional deforma is a right-lateral displacement along NW-SE tions corresponds to the NW-SE orientation strike-slip faults. These strike-slip faults also of ct3 axis perpendicular to the NE strike of expressed in the youngest deposits of the the compressional structures, which is mani Miocene-Pliocene age. fested in the main scarp of the slope offshore For the westernmost part of CM the strike- the Eastern CM. We relate it with a gravita slip regimes with NE-SW orientation of CTj axis tional effect (sliding) that occurred during were obtained. We consider their relation with the uplifting of the Crimea due to the short the activity along the Western Crimea dex- ening, thus, some structures, formed under tral strike-slip fault. This is confirmed by focal the compression, underwent the extension. mechanisms of the earthquakes occurred at It also finds the support in the orientation recent tectonic stage in the Western Crimean of the Eocene extensional syndepositional Seismic Zone [Gobarenko et al., 2016]. faults. Possibly, they relate with the formation A strike-slip regime with N-S orientation of the piggy back basin on top of the highest of the ctj axis was also detected in the east allochtonous unit northwards. ernmost part of the Eastern CM. We relate Recent regime. Along the northern margin some NNE-SSW-oriented left-lateral strike- of the BS (the Crimea-Caucasus coast), the slip faults during the Miocene-Pliocene, in main structures of shortening are marked by agreement with [Saintot et al., 1999], to the an active Crimea Seismic Zone (CSZ). The latest transtensional regime with E-W orien analyses of the focal mechanisms of 31 strong tation of ct3 axis. Thus, the N-S trend of the earthquakes during 1927—2013 reveals the compression characterizes the youngest tec recent transpression regime in the western tonic stage of the CM evolution resulting in part of the CSZ whereas in its eastern part, a numerous strike-slip faults in the Eastern according to seismicity, gravity field, modes CM and folding of E-W trend in KP. of deformation and the velocity model, it is Normal regime. A large variety of data re possible to suggest the present day compres lated to the normal faulting type regimes were sional regime. The latter demonstrates: 1) the obtained in the CM. Based on the structural reactivation of basement faults that, accord analysis and field observations two types of ing to [Sydorenko et al., 2016], related to the normal regimes have been defined in the area. formation of the Triassic basin, and 2) indi 1. Extensional deformations in regards to cates the underthusting of the East BS highly the rifting stage of the BS during the Cre extended crust under the Scythian Plate con taceous. These normal faults, containing the tinental crust.

108 Teo(pu3UHecKuû. xypnoA Ne 4, T. 39, 2017 SOUTH CAUCASUS GEOSCIENCES

References

Gobarenko V. S., Murovskaya A. V, Yegorova T. P, She- insights from new dating and structural data. In: remet Y., 2016. Collisional processes at the northern M. Sosson, R. Stephenson, Sh. Adamia (Eds.). Tec margin of the Black Sea. Geotectonics 50(4), 07—24. tonic Evolution of the Eastern Black Sea and Cauca doi: 10.1134/S0016852116040026. sus. Geol. Soc. London Spec. Publ., 428. http://doi. org/10.1144/SP428.14. Murovskaya A., Hippolite J.-C., Sheremet Ye., Yegoro va T, Volfman Yu., Kolesnikova Ye., 2014. Deforma Sheremet Y., Sosson M., Ratzov G., Sidorenko G., Ye tion structures and stress field of the south-western gorova T., Gintov O., Murovskaya A. V., 2016b. An Crimeain the context of the evolution of western offshore-onland transect across the north-east Black Sea Basin. Geodinamika (2), 53—68 (in Rus ern Black Sea basin (Crimean margin): evidence sian). of Paleocene to Pliocene two-stage compres sion. Tectonophysics 688, 84—100. doi: 10.1016/j. Saintot A., Angelier J., Chorowicz J., 1999. Mechani tecto.2016.09.015. cal significance of structural patterns identified by remote sensing studies: a multiscale analysis of Sydorenko G., Stephenson R., Yegorova T., Starosten- tectonic structures in Crimea. Tectonophysics 313, ko V., Tolkunov A., Janik T., Majdanski M., Voit- 187—218. doi: 10.1016/S0040-1951(99)00196-1. sitskiy Z., Rusakov O., Omelchenko V., 2016. Geo logical structure of the northern part of the Eastern Sheremet Y, Sosson M., Müller C., Murovskaya A., Gin- Black Sea from regional seismic reflection data in tov O., Yegorova T, 2016a. Key problems of stra cluding the DOBRE-2 CDP profile. Geol. Soc. Lon tigraphy in the Eastern Crimea Peninsula: some don, Spec. Publ. 428. doi: 10.1144/SP428.15.

Paleo- and recent stress regimes of the Crimea Mountains based on micro- and macroscale tectonic analysis and earthquakes focal mechanisms

©A. Murovskaya1, Ye. Sheremet2, M. Sosson2, O. Gintov1, T. Yegorova1, 2017

institute of Geophysics, National Academy of Sciences of Ukraine, Kiev, Ukraine 2Universite Cote d'Azur, UMR Geoazur, CNRS, Sophia Antipolis, France

The Crimea Mountains (CM) belongs to nisms of the earthquakes. Thus, the main pur the northern branch of the Alpine Belt. Being pose of our study is to find and investigate the northwestern continuation of the Great the correlation between the stress field and er Caucasus (GC) and a part of the inverted the large-scale deformation structures with northern margin of the Black Sea (BS), the subsequent determination of major tectonic CM region shows the similarities in structural events. development of both the domains, implying The Cenozoic compression. The major the common tectonic evolution of the GC — direction of the shortening during the Ce Eastern BS area. nozoic was defined in regards of main ori In the current study, we focus on the Meso- entation (trends) of the thrusts and fold axis Cenozoic time-span of tectonic evolution of developed in the Eastern CM and its nearest the CM and the adjacent BS margin in order offshore area [Sheremet et al., 2016a, b]. Thus, to define paleo- and recent stress regimes the westernmost part of the Eastern CM is alternated during its tectonic history, based characterized by the NW-oriented compres on the recent geological field observations, sion, while its eastern part is characterized by the results of structural analysis, the micro- NNW-SSE direction of the shortening. Two tectonic data and the analysis of focal mecha stages of the shortening during the Cenozo-

Teo(pu3unecKuü xypnoA Ns 4, T. 39, 2017 109 INTERNATIONAL RESEARCH GROUP PROJECT ic were defined based on the major Middle some NNE-SSW-oriented left-lateral strike- Eocene unconformity: the age-frames of the slip faults during the Miocene-Pliocene, in earliest compression stage is defined as the agreement with [Saintot et al., 1999], to the Paleocene—Middle Eocene time, whereas the latest transtensional regime with E-W orien youngest compression is suggested in the Oli- tation of ct3 axis. Thus, the N-S trend of the gocene—Middle Pliocene. compression characterizes the youngest tec Reverse regime. For the majority of sites tonic stage of the CM evolution resulting in in the CM we obtained the large display of a numerous strike-slip faults in the Eastern reverse regimes with Oj trending N-S, NNW- CM and folding of E-W trend in KP. SSE and NW-SE. According to orientation of Normal regime. A large variety of data re the thrust front defined offshore, the NW-SE lated to the normal faulting type regimes were orientation of the CTj compressional axis pre obtained in the CM. Based on the structural vails in the CM during the formation of the analysis and field observations two types of main compressional structures. It also has a normal regimes have been defined in the area. point for the NE-SW oriented structures of 1. Extensional deformations in regards to the southwestern part of the Kerch Peninsula the rifting stage of the BS during the Cre (KP). taceous. These normal faults, containing the In the area of Sudak the N-S shortening relict slickensides, tectonic breccias and trac was defined. This N-S and NNE-SSW trend of es of attached marine organisms, confine the shortening can be traced in KP where the cor Early Cretaceous depressions within the CM. responding structures overthrust those, which The corresponding stress fields are character were formed under the NW-SE compression. ized by N-S and NNE-SSW trend of the cr3 Moreover, the reverse regimes with Oj trend extensional axis in the Western Crimea and ing NNE-SSW characterize the structures of by the NE-SW orientation of the o3 axis in the Western CM. Thus, the first compression, the Eastern CM. New stratigraphy dating and which follows the Cretaceous extension stage, structural analysis in the Western CM indi was the one of, mainly, NW-SE orientation. cate a later extensional stage for the Western Strike-slip regime. The analysis of the BS (Valanginian-Barremian) [Murovskaya et structural patterns in the Eastern CM re al., 2014] than for its Eastern part when the veals several faults of NE-SW and NNE-SSW latter experienced the loading of the GC ba trends with left-lateral strike-slip movements sin since the Middle Jurassic. along them. These strike-slip faults cut sev 2. The second type of extensional deforma eral thrusts and displaced laterally the thrust tions corresponds to the NW-SE orientation front in several places. In other cases, there of ct3 axis perpendicular to the NE strike of is a right-lateral displacement along NW-SE the compressional structures, which is mani strike-slip faults. These strike-slip faults also fested in the main scarp of the slope offshore expressed in the youngest deposits of the the Eastern CM. We relate it with a gravita Miocene-Pliocene age. tional effect (sliding) that occurred during For the westernmost part of CM the strike- the uplifting of the Crimea due to the short slip regimes with NE-SW orientation of Oj ening, thus, some structures, formed under axis were obtained. We consider their relation the compression, underwent the extension. with the activity along the Western Crimea It also finds the support in the orientation dextral strike-slip fault. This is confirmed of the Eocene extensional syndepositional by focal mechanisms of the earthguakes oc faults. Possibly, they relate with the formation curred at recent tectonic stage in the West of the piggy back basin on top of the highest ern Crimean Seismic Zone [Gobarenko et al., allochtonous unit northwards. 2016]. Recent regime. Along the northern margin A strike-slip regime with N-S orientation of the BS (the Crimea-Caucasus coast), the of the <7j axis was also detected in the east main structures of shortening are marked by ernmost part of the Eastern CM. We relate an active Crimea Seismic Zone (CSZ). The

n o Teo(pu3UHecKuû. xypnoA Ne 4, T. 39, 2017 SOUTH CAUCASUS GEOSCIENCES analyses of the focal mechanisms of 31 strong sional regime. The latter demonstrates: 1) the earthquakes during 1927—2013 reveals the reactivation of basement faults that, accord recent transpression regime in the western ing to [Sydorenko et al., 2016], related to the part of the CSZ whereas in its eastern part, formation of the Triassic basin, and 2) indi according to seismicity, gravity field, modes cates the underthusting of the East BS highly of deformation and the velocity model, it is extended crust under the Scythian Plate con possible to suggest the present day compres- tinental crust.

References

Gobarenko V. S„ Murovskaya A. V, Yegorova T. P, She- from new dating and structural data. In: M. Sosson, remet Y., 2016. Collisional processes at the northern R. Stephenson, Sh. Adamia (Eds.). Tectonic Evolu margin of the Black Sea. Geotectonics 50(4), 07—24. tion of the Eastern Black Sea and Caucasus. Geol. doi: 10.1134/S0016852116040026. Soc. London Spec. Publ., 428. http://doi.org/10.1144/ SP428.14. Murovskaya A., Hippolite J.-C., Sheremet Ye., Yegoro va T, Volfman Yu., Kolesnikova Ye., 2014. Deforma Sheremet Y, Sosson M., Ratzov G., Sidorenko G., Yego tion structures and stress field of the south-western rova T, Gintov O., Murovskaya A. V., 2016b. An off- Crimeain the context of the evolution of western shore-onland transect across the north-eastern Black Black Sea Basin. Geodinamika (2), 53—68 (in Rus Sea basin (Crimean margin): evidence of Paleocene sian). to Pliocene two-stage compression. Tectonophy Saintot A., Angelier J., Chorowicz J., 1999. Mechanical sics 688, 84—100. doi: 10.1016/j.tecto.2016.09.015. significance of structural patterns identified by re Sydorenko G., Stephenson R„ Yegorova T, Starostenko V, mote sensing studies: a multiscale analysis of tectonic Tolkunov A., Janik T, Majdanski M„ Voitsitskiy Z„ structures in Crimea. Tectonophysics 313,187—218. doi: 10.1016/S0040-1951(99)00196-1. RusakovO., Omelchenko V., 2016. Geological struc ture of the northern part of the Eastern Black Sea Sheremet Y, Sosson M., Müller C., Murovskaya A., Gin- from regional seismic reflection data including the tovO., Yegorova T, 2016a. Key problems of stratigra DOBRE-2 CDP profile. Geol. Soc. London, Spec. Publ. phy in the Eastern Crimea Peninsula: some insights 428. doi: 10.1144/SP428.15.

Magmatism and ore formation on the example of Upper Cretaceous Bertakari and Bneli Khevi Ore deposits, Bolnisi ore district, Georgia

1Tbilisi State University, M. Nodia Institute of Geophysics, Tbilisi, Georgia 2Tbilisi State University, A. Janelidze Institute of Geology, Tbilisi, Georgia

Magmatic evolution is an important event lisional primarily subaerial volcanic eruptions in the formation and development of the geo followed by formation of volcanic highlands logical structure of Southern Georgia, where and plateaus occurred in the region. several reliably dated volcanogenic and The Artvin-Bolnisi unit forms the north volcanogenic-sedimentary formations are western part of the Lesser Caucasus and established. The region represents a modem represents an island arc domain of so-called analogue of continental collision zone, where the Somkheto-Karabakh Island Arc or Bai- subduction-related volcanic activity lasted burt-Garabagh-Kapan belt. It was formed from Paleozoic to the end of Paleogene. After mainly during the Jurassic-Eocene time in the period of dormancy in the Early-Middle terval on the southern margin of the Eurasian Miocene, starting from the Late Miocene and plate by north-dipping subduction of the up to the end of the Pleistocene, syn-postcol- Neotethys Ocean and subsequent collision

Teo(pu3unecKuü xypnoA Ns 4, T. 39, 2017 111 INTERNATIONAL RESEARCH GROUP PROJECT

Ma Age Formation Thickness Lithology Description

Limestones, maris, interlayers of Tetritscaro 200-300 m K2t epiclastic deposits 72,1 Extrusive, coarse-grained, medium-grained and fine-grained volcanoclastic rocks of Shorsholeti 150-350 m \ A l \ A A A A A A A A A A A A A A A A calc-alkanne and sub-alkaline andesite- VVVVVVVVVVVVVVVVVV V basaltic composition; K2sh interlayers of limestones, marls and ?î epiclastic deposits

A • A • A .A .A •A -A •A •A A A V V V V A A A. A. A A A A A Extrusive, coarse-grained, medium-grained A • A • A •A •A .A ■ A •A -A and fine-qrained volcanoclastic rocks of Gasandami 150-600 m V V V V calc-alkaltne dacite-rhyolitic composition; A A A A A A A A A interlayers of limestones, marls and K2gs A • A • A •A •A •A ■ A •A -A / A A A epiclastic deposits V \ A A A A A A A A A A • A • A A ■A ■A • A •A •A

AAAAAAAAAAAAAAAAAA vvvvvvvvvvvvvvvvvvv

A A A A A A A A A A AAA A A A A A vvvvvvvvvvvvvvvvvvv Extrusive, coarse-grained, medium-grained and fine-grained volcanoclastic rocks of c Tandzia 150-700 m A A A À A A A A A A A Â A A A A A A calc-alkaline andesite-basaltic composition^ .2 K2tn vvvvvvvvvvvvvvvvvv rare interlayers of limestones, marls and '30 - ► ...... epiclastic deposits a A A A A A A AAA. Î/5V

Extrusive, coarse-grained, medium-grained Mashavera 250-1000 m and fine-grained volcanoclastic rocks of calc-alkanne dacite-rhyolitic composition; K2ms interlayers of carbonate and epiclastic deposits

89,8

AAAAAAA .AA Extrusive, coarse-grained and fine-grained vvvvvvvvvvvvvvvvvvv volcanoclastic rocks of andesite-basaltic lUUUUUiiinAU A A A A A A A A A A A A A A A A A A composition; Didgverdi 250-750 m VVVVVVVVVVVVVVVVVVV interlayers of limestones, marls and iimuiAUiiiiUii epiclastic deposits K2dg A A A A A A A A A A A A A A A A A VVVVVVVVVVVVVVVVVV

Extrusive, medium-grained and fine-grained volcanoclastic rocks of dacite-rhyolitic composition; interlayers of limestones and epiclastic deposits

Conglomerates, gritstones, sandstones, limestones and fine-grained volcanoclastic 100,5 rocks

Fig. 1. Lithostratigraphic column of the Upper Cretaceous deposits of the Bolnisi ore district, modified by [Adamia etal., 2016]. of the Anatolia-Iranian continental plate. graphic relationships and are subdivided into The Artvin-Bolnisi tectonic unit, includ several formations due to their composition. ing the Bolnisi ore district, was developing Volcanics are attributed to calc-alkaline-sub- as a relatively uplifted island-arc type unit alkaline series. Depositional environment of with suprasubduction magmatic events. Vol- the Upper Cretaceous volcanic formations canogenic complexes are characterized by varies from shallow-marine to subaerial set variable lateral and vertical regional strati tings. Mafic to intermediate volcanic rocks

112 reo

Fig. 2. Types of hydrothermal breccias: a — hydrothermal breccia, Bneli Khevi outcrop; b — pseudobreccia, Bneli Khevi outcrop; c — hydrothermal breccia, Bertakari, Kldovani Ubani, core image BK 822,228—231 m; d — pseu dobreccia, Bertakari, Kldovani Ubani, core image BK 875,260—263 m. are in subordinate amount. Felsic formations (phreatic, phreatomagmatic and hydrother (Mashavera and Gasandami) are the major mal) within Bertakari and Bneli Khevi. hosts of numerous ore deposits (Madneuli, It is noteworthy the recognition of hydro- Sakdrisi, Bertakari, Bneli Khevi etc.) within thermal breccias with jigsaw-fit clast textures the ore field (Fig. 1). (Fig. 2, a, b) and pseudobreccias (Fig. 2, c, d) The common consent of the researchers in the mentioned above deposits [Gelashvili exists about the genetic link of the Bolnisi ore et al., 2015; Lavoie, 2015]. Pseudobreccias are field gold-polymetallic ore-forming proces resulted from diffusive/selective alteration of ses with the late Cretaceous suprasubduc- intrusive, subvolcanic or volcaniclastic rocks. tion magmatism. The latter is related to the Development of jigsaw-fit clast textures in north-dipping subduction zone of the Lesser breccias is induced by hydraulic brecciation Caucasus which conditioned island-arc type [Casetal.,2011]. volcanic activity and mineralization of the The deposits are hosted by Gasandami for late Cretaceous Tethys and its northern ac mation that is represented by following lithofac- tive margin. es types: felsic volcanic lapilli tuffs, ignimbrites, Campanian nannoplankton fossils have pumice tuffs and reccias and rhyodacitic dome. been discovered in hydrothermally slightly The existence of epigenetic hydrothermal altered rocks (pelitic tuffs, tuff-argillites, tuff- breccia bodies is the common feature of ma sandstones) of Bertakari area. ny geodynamic setting types, especially of The peculiarities of magmatic activity island-arcs, and is the substantial part of the and geodynamic development of the region long-lasting history of magmatic-hydrother stipulated synchronous formation of signifi mal activity [Howard et al., 2015]. cant base and precious metals deposits of the Acknowledgements. This work was suppor Bolnisi ore district. ted by Rustaveli National Science Foundation Within the Bolnisi ore district, Bertakari (SRNSF), projects № 04-45 (GDRI — Interna and Bneli Khevi deposits host lithofacies and tional Research Group: South Caucasus Geo- spatial distribution of associated mineraliza Science (Georgia — Eastern Black Sea)) and tion that has been studied. The outcrops and YS-2016-14 (Late Mezosoic — Ealy Cenozoic drill cores visual observations as well as thin Suprasubduction Magmatism Evolution and section microscopy has revealed the link of Geodynamics: Constraints from Southern the mineralization to various types of breccias Georgia).

Геофизический журнал Ns 4, T. 39,2017 113 INTERNATIONAL RESEARCH GROUP PROJECT

References

Adamia S., Moritz R., Shubitidze J., Natsvlishvili M., polymetallic ore composition material in Bektakari Tchokhonelidze M., 2015. Epithermal and porphyry deposit. Bolnisi ore district: Proc. of Sci. Conf. on Recent Geological Problems of Georgia, publisher deposits of the Lessser Caucasus (Georgia and Ar «Technical University», 23—24 April, 2015. P. 35—39 menia). Unpublished fieldguide book for the 13th (in Georgian). SGA Biennial meeting, Nancy, 53 p. Howard N., Andrew F., Brookes D., 2015. Genetic clas Cas R., Giordano G., Balsamo E, Esposito A., Lo sification of breccias, http://www.academia.edu/ Mastro S., 2011. Hydrothermal Breccia Textures 9593848/GENETIC_CLASSIFICATION_OF_BREC- and Processes: Lisca Bianca Islet, Panarea Vol CIAS. cano, Aeolian Islands, Italy. 2011. Economic Geol ogy 106(3), 437—450. http://dx.doi.org/10.2113/ Lavoie J., 2015. Genetic constraints of the Late-Creta- econgeo. 106.3.437. ceous Epithermal Beqtakari prospect, Bolnisi Min ing District, Lesser Caucasus, Georgia. University Gelashvili N„ Tsertsvadze B„ Kvantaliani G„ Gelas- of Geneva, Department of Earth Sciences, Master hvili A., 2015. The first information about gold- of Geology Thesis, P. 1—82.

Paleogene sedimentary development and tectonic conditions of shagap piggyback basin (Armenia)

institute of Geological Sciences, National Academy of Sciences of Republic of Armenia, Yerevan, Armenia 2Université Côte d'Azur, UMR Géoazur, CNRS, Sophia Antipolis, France 3 Université de Montpellier II, UMR Géosciences, CNRS, Montpellier, France

Shagap syncline is elongated asymmetric Trachyandesite dikes and sills (ALIO-14 — basin presented by Paleogene deposition of N 39° 57.296', E 44° 51.195') were injected into about 1.5 km thicknesses. Sedimentation took Lower Paleocene—Lower and Middle Eocene place after collision of Eurasian plate and sedimentary rocks. South Armenian M icrocontinent (SAM). In Shoshonite series trachyandesites nor Middle Eocene—Oligocene time piggyback malised by chondrites have mobile elements basin by slope deposition and turbidite accu enrichment (Rb, Ba and Th) with negative mulation, controlled by gravitational process HFSE (Nb, Ta) anomalies. The (La/Sm)CN ratio es, was formed. Lithologically different type yield 6.84 value but the (La/Yb)^ ratio is 38.17, of deposition in this partly isolated basin is suggesting the presence of residual material the result of constant input of terrigenous ma from the deep magmatic source. Neodymium terial, volcanism and palaeoclimate changes. and strontium isotopes yield low eNd(14 5Ma^ Discocyclina-Nummulitic limestones and high 87Sr/86Sr(-14 5Ma^ ratios, respectively (packstone/grainstone) without micrite and -0.4 and 0.7054. Initial Pb/Pb isotopic ratios cement evidence shallow marine slope en yield 207Pb/204Pb(i) — 15,67; 208Pb/204Pb(i) — vironment where regular flow was available. 39.05, suggesting EM2, slab-component con Nummulite and red algae (Lithothamnion) tribution and crustal contamination. limestones show relatively low light sea en The obtained U-Pb zircon age for trachy vironment {oligophotic zone). Coralline built andesites is 14.5+0.2 Ma, which is coincident with nummulitides were formed in-situ indi with magmatism reactivation in the Middle- cating accumulation in a shallow condition Upper Miocene, after Arabian-Eurasian plates with intense light (photic zone). collision in the Upper Eocene-Oligocene.

114 Геофизический журнал Ne 4, T. 39, 2017 SOUTH CAUCASUS GEOSCIENCES

Tectonic evolution of the Crimean Mountains since the Triassic: Insight from the new dating and on-and-offshore structural data (macro- and microscale), In general tectonic context of the Greater Caucasus-Black Sea domain

^niversite Cote d'Azur, UMR Geoazur, CNRS, Sophia Antipolis, France institute of Geophysics, National Academy of Sciences of Ukraine, Kiev, Ukraine

The Crimea, being a part of the Black of the Triassic Trough (Basin) within the Sea-Greater Caucasus system (BS-GC), southern margin of Laurasia in the fore/ owes its origin to the subduction of the back-arc position. The normal faults in the Neotethys beneath the Eurasian margin basement which have been formed during which is the main geodynamical process this period in consequence will be reacti that had a significant influence on the de vated during the following BS rifting stage velopment of the Crimea and changed the and the Cenozoic shortening [Sydorenko tectonic conditions during its geological etal., 2016[). history. The enigmatic Cimmerian deforma Two main tectonic stages were record tions, in addition to other well-known ed in BS-GC region concerning the sub stated versions, one can suggest a slab duction of the Neotethys and its closure: shallowing during the Early Jurassic that 1) the opening of the BS and the GC ba could result in compression (accretion) of sins in a back-arc position, starting from basin sediments. the Early-Middle Jurassic and then after The extensional stage, in the Crimea during the Early to mid-Cretaceous and in region, was followed by the development the Paleocene-Eocene times; 2) the con of the GC back-arc Basin in the Early- tinental collision between the Eurasian Middle Jurassic and capped by back-arc margin with the Taurides-Anatolides and magmatism of the Middle Jurassic related the South Armenian Microplate (TASAM) to the subduction (40Ar/39Ar dating and and then with Arabian plate. This colli the geochemical analysis of magmatic sion triggered the shortening of the BS rocks, according to [Meijers et al., 2010]) Basins, thus, the inversion structures have in both future mountain systems. been described all around the Black Sea The Jurassic period is characterized by (Pontides-Balkanides orogens, Romanian wide distribution of massive carbonated shelf and the area of Odessa Shelf— platforms and reef limestones on top of the Crimea—Greater Caucasus). deformed basinal deposits of the Triassic- The presence of two flysch units of dif Middle Jurassic age (the carbonate build ferent ages (Tauric Gp and Cretaceous ba up are known in the GC, and evidential sin deposits) that are outcropping in the from the seismic data on the Shatskiy CM reveals a period of subsidence. That Ridge). These carbonated facies, much of allows the conclusion about the formation them are platform, continued through the

Teo(pii3imecKiiu xcypHOA Ns 4, T. 39, 2017 115 INTERNATIONAL RESEARCH GROUP PROJECT entire Late Jurassic-Berriasian time span riod of a low rate compression (Middle (till the Hauterivian) in the central CM. Eocene), the inversion since the Latest The olistoliths origin of large carbonated Eocene has been renewed. Probably, Plateaus in the Crimea is not confirmed this second period of shortening in the during the field observations. Crimea could be explained by initial col During the Early Cretaceous the BS lision of the Arabian plate with Eurasia basin (a back-arc basin, north of the since they coincide in time. The very ex subduction zone of Neotethys beneath tended (sub-oceanic) crust, created dur Eurasia) was initiated by rifting and then, ing the Cretaceous by the latest period of a probable spreading center produced shortening (latest Eocene-Miocene time the oceanization of this basin [Sosson et span) have been already cold enough and, al., 2016]. Subduction of the spreading therefore, mechanically stronger in or center of the north branch of Neotethys der to affect the continental margins and formed an asthenospheric window. It produce the compressional deformations. could produce heating and, as the result, The Shatskiy Ridge plays as indenter in the weakening of the strong lithosphere the underthrusting of the Eastern BC mar of Eurasia. This process should initiate gin. Thus, the CM have been occurred as the rifting of the Eastern BS during the a result of a thin skin tectonic offshore and Early Cretaceous, and then, as mentioned both thick- and thin-skin tectonic on land by [Stephenson, Schellart, 2010]), the roll [Sheremet et al., 2016a]. back of the slab should favor the opening In the Latest Miocene the Messinian of this small oceanic basin probably dur sea level drop, recorded in the significant ing the time limit between Early and Late erosion surface offshore, against the back Cretaceous. ground of continuing shortening, most The inversion of the North Eastern likely triggered the mud volcano activity BS margin is also the result of the evolu that at present is the distinctive feature of tion of the Neotethys subduction zone. the BS topography. During the Latest Cretaceous—Middle The current stage of the CM is char Eocene period (74—40 Ma), collision be acterized by the seismicity of magnitude tween a continental microplate (TASAM) 4—6 located in lower crust and upper with the Eurasia initiated in the Lesser mantle at depth between 30 and 38 km Caucasus and then continued westward showing, mainly a north dipping plan during the Eocene. The inversion of the of its distribution in the Eastern CM CM commenced during the Paleocene [Gobarenko et al., 2016]. The reverse [Sheremet et al., 2016a, b]. Thus, we faults in the basement, as well as strike suggest that the collisional process to slip faults, reactivated by the inversion of the south of the Eastern BS initiated the the BS (Alushta-Simferopol fault, Western compression in the CM by reactivation Crimea dextral strike-slip fault), should of the Late Triassic-Early Jurassic normal be responsible for the main seismic activ faults in the basement. Then, after a pe- ity in Crimea.

References

Gobarenko V S., Murovskaya A. V., Yegorova T. P., Meijers M. J. M., Vrouwe B., Van Hinsbergen D. J. J., Sheremet Y., 2016. Collisional processes at the north Kuiper K. F., Wijbrans J., Davies G. R., Stephenson ern margin of the Black Sea. Geotectonics 50(4), R. A., Kaymakci N., Matenco L., Saintot A., 2010. 07—24. doi: 10.1134/S0016852116040026. Jurassic arc volcanism on Crimea (Ukraine): impli

116 Teo(pu3imecKiiü. xypnoA Ne 4, T. 39, 2017 SOUTH CAUCASUS GEOSCIENCES

cations for the paleo-subduction zone configuration Adamia S., Melkonian R., Kangarli T, Yegorova T, of the Black Sea region. Lithos 119(3), 412—426. doi: Avagyan A., Galoyan G., Danelian T, Hassig M., 10.1016/j.lithos.2010.07.017. Müller C., Sahakyan L., Sadradze L., Sadradze N., Alania V, Enukidze O., MosarJ., 2016. The eastern Sheremet Y, Sosson M., Müller C., MurovskayaA., Gin- Black Sea-Caucasus region during the Cretaceous: tovO., Yegorova T, 2016a. Key problems of stratigra New evidence to constrain its tectonic evolution. C. phy in the Eastern Crimea Peninsula: some insights R. Geosci. 348, 23—32. http://dx.doi.Org/10.1016/j. from new dating and structural data. In: M. Sosson, crte.2015.11.002. R. Stephenson, Sh. Adamia (Eds.). Tectonic Evolution of the Eastern Black Sea and Caucasus. Geol. Soc. Stephenson R., Schellart W. P., 2010. The Black Sea back- London Spec. Publ., 428. http://doi.org/10.1144/ arc basin: insights to its origin from geodynamic SP428.14. models of modem analogues. Geol. Soc. London Spec. Publ. 340(1), 11—21. Sheremet Y, Sosson M., Ratzov G., Sidorenko G., Yego rova T, GintovO., MurovskayaA. V, 2016b. An off- Sydorenko G., Stephenson R., Yegorova T, Starostenko V, shore-onland transect across the north-eastern Black Tolkunov A., Janik T, Majdanski M., Voitsitskiy Z., Sea basin (Crimean margin): evidence of Paleocene Rusakov O., Omelchenko V., 2016. Geological struc to Pliocene two-stage compression. Tectonophysics ture of the northern part of the Eastern Black Sea 688, 84— 100. doi: 10.1016/j.tecto.2016.09.015. from regional seismic reflection data including the DOBRE-2 CDP profile. Geol. Soc. London Spec. Sosson M., Stephenson R., Sheremet Y, Rolland Y, Publ. 428, doi: 10.1144/SP428.15.

The highlights and the contribution of International Research Group (IRG) «South Caucasus Geosciences» (France, Armenia, Azerbaijan, Georgia and Ukraine)

Université Côte d'Azur, UMR Géoazur, CNRS, Sophia Antipolis, France 2Javakhishvili Tbilisi State University, Tbilisi, Georgia institute of Geology and Geophysics, National Academy of Sciences of Azerbaijan, Baku, Azerbaijan institute of Geological Sciences, National Academy of Sciences of Republic of Armenia, Yerevan, Armenia institute of Geophysics, National Academy of Sciences of Ukraine, Kiev, Ukraine 6Université de Lille, CNRS, UMR Evo-Eco-Paleo, Lille, France 7 Université de Montpellier II, UMR Géosciences, CNRS, Montpellier, France

Initiated in collaboration within the frame of the Academy of Science of Ukraine, became work of proj ects funded by the European prog one of the partners of IRG in 2014. rammes INTAS, Erasmus Mundus and PICs, With a support of Middle East Basins LLA programmes of the CNRS/INSU, three Evolution and DARIUS programmes (con French laboratories (Geosciences of Mont sortium of oil companies, Univ. Pierre et pellier, Geoazur of Nice Sophia Antipolis and Marie Curie Paris VI, and CNRS/INSU) this Evo-Eco-Paleo of Lille), and Institutes of Aca IRG aimed at solving the Earth Sciences demies of Sciences and Universities of Armenia, questions, mainly in resources and hazard Azerbaijan, Georgia an International Research fields, in the Caucasus-Eastern Black Sea Group (IRG: GDRI de CNRS/INSU) «South Domain (CEBSD) that has a high potential Caucasus Geosciences» were founded in 2010. in research since this part of the Alpine belt Ukraine, presented by Institute of Geophysics evolved during the long-lived subduction of Геофизический журнал Ns 4, T. 39, 2017 117 INTERNATIONAL RESEARCH GROUP PROJECT the Neotethys ocean due to its closure (see oped in these tectonic settings; 3) the rela for a review e.g. [Sosson et al.r 2010, 2016]). tion in time and the continuity of structures The main issues to solve in the eastern between the eastern Black Sea, the Greater Black Sea and Caucasus realm in this geo Caucasus, the Lesser Caucasus and those of dynamic context are: 1) the time-space evo the Taurides-Anatolides, Pontides belt and of lution of geodynamic processes (subduction, the NW Iran as well.

km 300 45ÖN Eurasia

Scythian Platform

45°N

35°N Arabian Platform

35°N A rabia

30ÛE 35ÖE 40°E 45°E 50°E

Crimea-Greater Caucasus mountain belt European margin (Pontides, Somkheto-Karabakh) with magmatic arc Lesser Caucasus units (including! ophiolites) Sakarya accreted terrane Taurides-Anatolides/South Armenian accreted terranes, with ophiolites (olive) Iran accreted terrane (Eo-Cimmerian) Melamorphic massifs Taurides-Anatolides including allochthonous nappes and obducted ophiolites

Fig. 1. Tectonic map of the Black Sea-Caucasus domain and surrounding areas, modified from [Sosson et al., 2016,2017], showing the main field locations of IRG studies. obduction, collision) responsible for the clo An integral part of the project, exchange sure of the northern and southern branches of of scientists, apart from the important role Neotethys; 2) the timing of deformation and of joint research, favored to the development the evolution of the back-arc basins devel- of its international level, giving the birth to a

118 reo

References

Sosson M., Rolland Y, Danelian T, Muller C., S. A. Adamia (Eds.) Tectonic Evolution of the Eastern Melkonyan R., Adamia S., Kangarli T, Avagyan A., Black Sea and Caucasus. Geol. Soc. London Spec. Galoyan G., 2010. Subductions, obduction and col Publ. 428, https://doi.org/10.1144/SP428.16. lision in the Lesser Caucasus (Armenia Azerbaijan, Georgia), new insights. In: M. Sosson, N. Kaymakci, Sosson M„ Stephenson R., Sheremet Y, Rolland Y, R. Stephenson, E Bergarat, V. Starostenko (Eds.). Adamia Sh., Melkonian R„ Kangarli T, Yegorova T, Sedimentary Basin Tectonics from the Black Sea and Avagyan A., Galoyan Gh„ Danelian T, Hässig M„ Caucasus to the Arabian Platform. Geol. Soc. London Meijers M., Müller C„ Sahakyan L, Sadradze N., Spec. Publ. 340, 329—352. Alania V, Enukidze O., MosarJ., 2016. The Eastern Black Sea—Caucasus region during Cretaceous: Sosson M„ Stephenson R., Adamia Sh., 2017. Tectonic new evidence to constrain its tectonic evolution. Evolution of the Eastern Black Sea and Caucasus: Comptes Rendu Géoscience 348,23—32. https://doi. an introduction. In: M. Sosson, R. A. Stephenson, org/10. 1016/j.crte.2015.11.002.

Геофизический журнал Ns 4, T. 39, 2017 119 INTERNATIONAL RESEARCH GROUP PROJECT

Deep crustal structure of the transition zone of the Scythian Plate and the East European Platform (DOBRE-5 profile): consequences of the Alpine Tectonic evolution

©V. Starostenko1, M. Sosson 2, L. Farfulyak1, O. Gintov1, T. Yegorova 1, A M urovskaya 1, Ye. Sherem et2, O. Legostaeva 1, 2017

institute of Geophysics, National Academy of Sciences of Ukraine, Kiev, Ukraine 2Université Côte d'Azur, UMR Géoazur, CNRS, Sophia Antipolis, France

In 2011 an international team carried out phases of evolution: Mesozoic extension and the DOBRE-5 WARR (wide-angle reflection Cenozoic compression. and refraction) seismic profile [Starostenko In the current presentation we propose an et al., 2015]. Its major part runs in the W-E interpretation of the DOBRE-5 seismic model direction through the Scythian Plate in the and show the development of the TZ between northwestern shelf of the Black Sea (BS) and the EEP and SP during the Alpine orogenesis the plain Crimea. The velocity section on the in the frames of the Crimean-BS evolution. profile indicates a seismic boundary inclined Mesozoic extension. The red dashed line eastwards with a low angle. The boundary is on Fig. 1 shows the projection of the transi traced at the depth of ~2 km near the Zmeinyj tional zone (TZ) between EEP and SP on the Island then it goes below the northwestern DOBRE-5 profile; the zone itself is located to shelf (Karkinit Trough) and beneath the plain the north and has a ~W-E strike. According Crimea, and plunges to a depth of 47 km at to the interpretation, the Paleozoic-Mesozoic the transition to the Kerch Peninsula. This basement of the SP is displaced by the gen zone is interpreted as a transition zone (TZ) tly dipping normal fault, reaching the Moho between the Eastern European platform (EEP) boundary: the thickness of the Paleozoic-Me and the SP, naimely on the seismic profile we sozoic deposits is twice thicker on the footwall the projection of this zone [Starostenko et al., than on the hanging wall of this fault. 2015] . We suppose, that this listric fault (outlined A geodynamic interpretation of this tec by 1 in Fig. 1) plays an active role (also?) tonic zone, proposed by Farfulyak [2015], during the Cretaceous rifting. It is found the considers it as the Paleozoic North Crimean support in presence of a high-velocity body suture of Yudin [2008], formed as a result of (HVLC in Fig. 1) detected in the lower crust the closure of the Paleotethys ocean during in the area of Karkinit Trough. Such HVLC the Paleozoic-Triassic time span. bodies are very typical for the rift zones. New results, obtained in the framework Cenozoic compression. The Paleozoic-Me of our IRG project in regards to the northern sozoic basement of the SP (the Central Crime margin of the BS: 1) The new onshore struc an uplift) includes the layers of increased tural data in the Crimean Mountains (CM) velocities (FP=6.22^6.3 km/s) at the depth of [Murovskaya et al., 2014; Sheremet et al., 4—15 km (See Fig. 1), which we interpret as 2016b] and 2) the new structural offshore data the parts (blocks) of the pre-Riphean base (Sorokin Trough and Kertch Taman Trough) ment, involved in the thrusting. The age of the [Sheremet et al., 2016a; Sydorenko et al., compression postdates the Mesozoic, since 2016] allowed us to identify the structures the Mesozoic strata is affected by thrusts. developed in the CM and the northern mar Several detachments of gentle dipping gin of the BS in the context of two generalized at the depths of 15 and 7 km (denoted by 2

120 Teo(pu3UHecKuû. xypnoA Ne 4, T. 39, 2017 SOUTH CAUCASUS GEOSCIENCES

Fig. 1. Interpreted seismic model on the DOBRE-5 profile. and 3 in Fig. 1) we relate with the Cenozoic section (See Fig. 1) we distinguished sev compression that most likely was released eral normal faults that affected the middle in two-stages: 1) during the Paleocene-Early Miocene-Quaternary sediments, which we Eocene, revealed by the recent structural associate with the continuing loading of the and geological studies, onshore and offshore western BS. In regards to the Eastern BS, here [Sheremet et al.r 2016a, b; Sydorenko et al.r we observe the uplifting of the CM due to 2016] and 2) in the latest Eocene — Pliocene the collisional processes [Murovskaya et al., which is also evident on many seismic profiles 2014; Gobarenko et al., 2016]. from the western and northwestern shelf of Detailed interpretation of the DOBRE-5 the BS [Khriachtchevskaia et al.r 2010; Mo- profile allowed clearing up the long tectonic rosanu, 2012; Dinu et al.r 2005; M unteanu et evolution of the EEP with the formation of al., 2013; Sheremet et al., 2016a; Sydorenko the TZ to the SP during the closure of the Pa- etal., 2016]. leotethys Ocean that imprints the Cretaceous In the upper part of the interpreted cross extension and the Cenozoic compression.

References

Gobarenko V. S., Murovskaya A. V, Yegorova T. R, Farfulyak L. V., 2015. The nature of the inclined seis Sheremet Y, 2016. Collisional processes at the north mic boundary in the Earth's crust of the Scythian ern margin of the Black Sea. Geotectonics 50(4), microplate along the DOBRE-5 profile. Geophysical 07—24. doi: 10.1134/S0016852116040026. Journal 37(6), 23—39 (in Russian).

Dinu C , Wong H. K., Tambrea D., Matenco L., 2005. Khriachtchevskaia O., Stovba S., Stephenson R., 2010. Stratigraphic and structural characteristics of the Cretaceous-Neogene tectonic evolution of the Romanian Black Sea shelf. Tectonophysics 410, northen margin of the Black Sea from seismic re 417—435. doi: 10.1016/j.tecto.2005.04.012. flection data and tectonic subsidence analysis. In:

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M. Sosson, N. Kaymakci, R. A. Stephenson, F. Berger sus. Geol. Soc. London Spec. Publ. 428. http://doi. at, V Starostenko (Eds.). Sedimentary Basin Tecton org/10.1144/SP428.14. ics from the Black Sea and Caucasus to the Arabian Platform. Geol. Soc. London Spec. Publ. Vol. 340, Sheremet Y, Sosson M., Ratzov G., Sydorenko G., Voits- P. 37—157. itskiy Z., Yegorova T, Gintov O., Murovskaya A., 2016b. An offshore-onland transect across the north-eastern Black Sea basin (Crimean margin): ev Morosanu /., 2012. The hydrocarbon potential of the idence of Paleocene to Pliocene two-stage compres Romanian Black Sea continental plateau. Romanian sion. Tectonophysics 688, 84—100. doi: 10.1016/j. Journal of Earth Sciences 86(is. 2), 91—109. tecto.2016.09.015. Munteanu I., Willingshofer E., Sokoutis D., Matenco L., Starostenko V. I., Janik T, Yegorova T, Farfuliak L., Dinu C., Cloetingh S., 2013. Transfer of deformation Czuba W, Sroda P, Thybo H„ Artemieva I., Sos in back-arc basins with a laterally variable rheology: son M., Volfman Yu., Kolomiyets K., Lysynchuk D., Constraints from analogue modelling of the Bal- Omelchenko V, GrynD., GuterchA., KomminahoK., kanides—Western Black Sea inversion. Tectonophys- Legostaeva O., Tiira T, Tolkunov A., 2015. Seismic ics 602, 223—236. doi: 10.1016/j.tecto.2013.03.009. model of the crust and upper mantle in the Scythian Platform: the DOBRE-5 profile across the northwest Murovskaya A., Hippolite J.-C., Sheremet Ye., Yegoro- ern Black Sea and the 676 Crimean Peninsula. Geo- va T, Volfman Yu., Kolesnikova Ye., 2014. Deforma phys. J. Int. 201, 406—428. doi:10.1093/gji/ggv018. tion structures and stress field of the south-western Sydorenko G., Stephenson R., Yegorova T, Starosten Crimea in the context of the evolution of western ko V, Tolkunov A., Janik T, Majdanski M„ Voitsits- Black Sea Basin. Geodinamika (2), 53—68 (in Rus kiyZ., RusakovO., Omelchenko V., 2016. Geological sian). structure of the northern part of the Eastern Black Sea from regional seismic reflection data including Sheremet Y, Sosson M„ Müller C„ Murovskaya A., the DOBRE-2 CDP profile. Geol. Soc. London Spec. Gintov O. B., Yegorova T., 2016a. Key problems of Publ. 428. doi: 10.1144/SP428.15. stratigraphy in the Eastern Crimea Peninsula: some insights from new dating and structural data. In: Yudin V. V., 2008. Geodynamics of the Black Sea—Cas M. Sosson, R. Stephenson, Sh. Adamia (Eds.). Tec pian Region. Kiev: UkrGGRI Publ., 117 p. (in Rus tonic Evolution of the Eastern Black Sea and Cauca sian).

Intraplate orogenesis

School of Geosciences, Geology and Petroleum Geology, Meston Building, King's College, University of Aberdeen, Aberdeen, UK

Plate tectonics has it that major orogens previously severely thinned and often signif form at plate boundaries, specifically in re icantly intruded and infiltrated continental sponse to collision of continental lithos lithosphere but, nevertheless, continental pheric plates with other continental lithos lithosphere that was not breached or broken pheric plates or island arc terranes and so in a plate tectonic sense to produce a new on. A multitude of schematic diagrams have lithospheric plate boundary at which new been published in the last 50 years showing oceanic lithosphere is accreted. Although black-coloured oceanic crust being sub there are semantics involved, this cannot ducted under white-coloured continents, count as orogenesis at a plate boundary: it continental fragments, other pieces of oce is, accordingly, «intraplate orogenesis». It anic crust, often with subduction polarity seems likely to me that much of the large- flipped from one panel to another. Lately, scale compressional deformation recorded abundant evidence, and a theoretical basis in the Alpine-Tethys belt might qualify as for it, has been published showing that many «intraplate orogenesis» in this regard and orogenic belts involve extreme shortening of that many (if not all?) ophiolite complexes

122 Геофизический журнал Ne 4, T. 39, 2017 SOUTH CAUCASUS GEOSCIENCES ubiquitous in this belt do not represent ob- erature published during the last years that ducted crust of oceanic lithospheric affin supports this model and try to demonstrate ity but rather remnants of highly deformed, some of the as yet not fully explored impli infiltrated and magmatised crust of conti cations of such a model for the geodynamics nental lithospheric affinity. I'll review the lit of «intraplate orogenesis».

Seismicity and crustal structure of the Southern Crimea and adjacent Northern Black Sea from local seismic tomography

'institute of Geophysics, National Academy of Sciences of Ukraine, Kiev, Ukraine 2School of Geosciences, Geology and Petroleum Geology, Meston Building, King's College, University of Aberdeen, Aberdeen, UK 3Université Côte d'Azur, UMR Géoazur, CNRS, Sophia Antipolis, France

The Greater Caucasus and the Crimea based on seismic surveys (active and passive) Mountains constitute a fold-and-thrust belt in the study area. that formed near the southern margin of Eur The distribution of determined hypocen asia as a result of Cenozoic collision between tres indicates three main seismicity subzones: Eurasia and the Africa—Arabian Plate. The 1) the Kerch-Taman subzone, which dips north Main Caucasus Thrust (MCT), which marks ward at an angle of ~30° to a depth of 90 km; the southern boundary of the Greater Cauca 2) the South Coast (or Yalta-Alushta) subzone, sus orogen, can be traced westward along the which dips to the southeast at an angle of ~18° northern margin of the Black Sea and coin with earthquake foci dominantly at depths of cides at depth with a zone of seismicity called 10—25 km; 3) the Sevastopol subzone, which the Crimea Seismic Zone (CSZ). is orthogonal to the South Coast subzone and The CSZ is characterized by earthquakes confines it from the west, characterised by dif of A4=3+5 with foci in the crust and uppermost fuse seismicity to a depth of ~40 km. mantle with abundant weak seismicity (M<3). The new local tomographic results docu The latter was used to recover the velocity ment significant P- and S-wave velocity het structure of the crust of southern Crimea erogeneities in the depth range 10—30 km. Peninsula and adjacent northern Black Sea Stable solutions have been obtained for employing local seismic tomographic tech depths of 15, 20 and 25 km. A distinctive fea niques. Events were recorded during 1970— ture of the crust of Crimea Mountains (west 2013 by nine stations on the Crimea peninsula ern Crimea) is the presence of a high-velocity (Crimea Seismic Network; CSN) and by one (6.7—6.8 km/s) domain of complex configura station (Anapa) on the Caucasus coast of the tion, comprising a number of separate bodies. eastern Black Sea. Data for the tomographic It is separated from the more eastern Crimea modelling, earthquake hypocentres, were and Kerch peninsula by a linear low-velocity relocated for the P- and S-wave arrivals at zone of ~N-S strike (in the Sudak area) in all permanent stations of CSN. Earthquake terpreted as a manifestation of a weakened relocation was done via error minimisation crustal zone, possibly associated with the starting with a ID reference velocity model Feodosiya Fault expressed at the surface,

Геофизический журнал Ns 4, T. 39, 2017 123 INTERNATIONAL RESEARCH GROUP PROJECT which, in turn, could be linked to a collinear geometries are involved. The relocated hy- Proterozoic N-S trending fault zone in the pocentres in combination with the tomogra Ukrainian Shield. From other side, it could phy models show that there is a change of be indication of a normal fault zone related underthrusting polarity in the western Crimea to the Early Cretaceous rifting and opening Mountains crust compared to eastern Crimea. of the East Black Sea Basin. To the east of this This may be a reflection of structural inheri low-velocity zone the crustal structure lacks tance and reactivation during compression of notable velocity anomalies. the same deeper structures that earlier con Preliminary interpretation of velocity trolled formation of the mid-Black Sea Rise anomalies suggests that complex 3D crustal during Black Sea extension.

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