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The intricate basins (Kura and Rioni) located between the Greater and the Lesser Caucasus are the site of several hydrocarbon fields. In eastern Georgia, the Samgori field in the western end of the vast Kura basin extends into Azerbaijan. It is the largest hydrocarbon discovery in Georgia, with a cumulative production of more than 250MbO. In western Georgia in the western and southern Rioni, only small size fields have been discovered (East Chaladidi, Supsa or Shromisubani, a few MbOE produced).The ingredients of the petroleum system belong to the Tertiary : source rocks from the Maikop formation, siliciclastics and volcanoclastics reservoirs, shaly intervals as cap rocks, and Neogene structures linked to the structuration of the Greater and Lesser Caucasus fold belts.The Mesozoic series in the Kura basin constitute a speculative hydrocarbon target to be explored in the future although at greater depth below the Tertiary folds. In the Kartli sub-basin at the western end of the Kura basin, there is only scattered and often over-matured Mesozoic series to look for source, reservoir and cap rocks analogs.In the Rioni basin, less mature Mesozoic series crop out, offering a possible evaluation of all the geologic elements and processes essential to an hydrocarbon accumulation. A preliminary investigation of the Mesozoic series revealed several organic rich horizons, reservoirs and cap rocks in the pre Cretaceous series. This leads to propose a schematic pre-Cretaceous paleogeography constituting the base for defining possible petroleum systems. Preliminary organic geochemical analyses of organic-rich horizons lead to identify several layers having fair to moderate hydrocarbon potential for oil and gas. Based on this preliminary result, information derived from bibliography and published seismic lines, and 1D modeling with Petromod software lead to propose new potential plays in the Rioni basin.This speculative study requires new biostratigraphic studies to confirm the ages of the various identified organic rich horizons, some of them being possibly new to refine the modelings. More detailed fieldwork should focus on reservoir quality and distribution. Eventually, analysis of reprocessed seismic data will permit to confirm new petroleum thematics.

International audience; The SW-Gissar range (westernmost part of the Tien Shan) consists of a succession of anticlines andsynclines forming a relief between the Amu Darya and Afghan-Tajik basins. Recent fieldwork has beenperformed to study the development and the architecture of a vast Middle-Upper Jurassic carbonate platform. The studied carbonate series crops out along cliffs overlying Lower to Middle Jurassic continental then marine deposits. Carbonate thickness reaches 500 m in the central and southern Gissar and thins up northwards, near the paleo-border of the Amu Darya Basin. The goal of this study was to build a highresolution stratigraphic framework for these deposits, based on chemo-and lithostratigraphic correlations between seven sections. It was associated with a detailed microfacies analysis in order to establish the spatial and temporal evolution of the palaeoenvironments in this poorly known area. Two major sequences were recognized, (1) Callovian in age, and (2) possibly Oxfordian to Lower Tithonian. The reconstruction of the deposition profile indicates that the Gissar was a gently dipping ramp during the Callovian major sequence. Dark mudstones with entire bivalve and brachiopod shells and oncoids-rich float-to rudstones predominated below and around the storm wavebase. Oobioclastic grainstones were deposited in the permanently agitated shallow water zone, while patch and pinnacle reefs built up distally at the inner-mid ramp transition and in the mid ramp. Small shallow water siliciclastic deltas developed close to the emerged lands located in the north. The Callovian sequence is subdivided into seven fourth-order transgressive-regressive sequences. The transition between the two major sequences is marked by a significant change in the carbonate sedimentary system associated with a positive shift in the bulk carbon isotope values. It could record a major climatic change coeval with the Middle-Late Jurassic Transition. Further, it is hypothesized that a sedimentary hiatus exists, possibly caused by the exposure of the platform. The Upper Jurassic major sequence is mostly composed of peritidal deposits, showing rapid vertical and lateral transitions, depicting a more complex architecture. The series consists in numerous meterthick alternations of pellets/algal pack-to grainstone, ‘microbial oncoid’ floatstone, ooid grainstones and mudstones. These deposits could have accumulated in a vast, mostly aggrading lagoon protected by a barrier reef. Basinwards, close to the Uzbek-Turkmen border, Middle Oxfordian organic-rich algal/microbial carbonates are intercalated within the platform carbonates and could have formed in small stratified and partly isolated intra-shelf depressions. Lastly, a general aridification of the basin could be responsible for the observed increase in gypsum characterizing the upper part of the carbonate platform (Late Oxfordian? to Tithonian?). The numerous oscillations in carbon isotopes evidenced in these evaporite-rich carbonates may be the consequence of high frequency exposure of the platform preceding the deposits of massive evaporite during the Tithonian. This study allows a better understanding of the paleoenvironmental evolution of the northern Tethys during the Middle and Upper Jurassic. Our results will be compared with other Peri-Tethyan Jurassic platforms in order to understand the carbonate platform response to large-scale climatic and tectonic changes occurring at this period.

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International audience; New GPS measurements in Chiapas (Mexico), Guatemala and El Salvador are used to constrain the fault kinematics in the North America (NA), Caribbean (CA) and Cocos (CO) plates triple junction area. The regional GPS velocity field is first analysed in terms of strain partitioning across the major volcano-tectonic structures, using elastic half-space modelling, then inverted through a block model. We show the dominant role of the Motagua Fault with respect to the Polochic Fault in the accommodation of the present-day deformation associated with the NA and CA relative motion. The NA/CA motion decreases from 18-22 mm yr−1 in eastern Guatemala to 14-20 mm yr−1 in central Guatemala (assuming a uniform locking depth of 14-28 km), down to a few millimetres per year in western Guatemala. As a consequence, the western tip of the CA Plate deforms internally, with ≃9 mm yr−1 of east-west extension (≃5 mm yr−1 across the Guatemala city graben alone). Up to 15 mm yr−1 of dextral motion can be accommodated across the volcanic arc in El Salvador and southeastern Guatemala. The arc seems to mark the northern boundary of an independent forearc sliver (AR), pinned to the NA plate. The inversion of the velocity field shows that a four-block (NA, CA, CO and AR) model, that combines relative block rotations with elastic deformation at the block boundaries, can account for most of the GPS observations and constrain the overall kinematics of the active structures. This regional modelling also evidences lateral variations of coupling at the CO subduction interface, with a fairly high-coupling (≃0.6) offshore Chiapas and low-coupling (≃0.25) offshore Guatemala and El Salvador.

International audience; Orogens formed by a combination of subduction and accretion are featured by a short-lived collisional history. They preserve crustal geometries acquired prior to the collisional event. These geometries comprise obducted oceanic crust sequences that may propagate somewhat far away from the suture zone, preserved accretionary prism and subduction channel at the interplate boundary. The cessation of deformation is ascribed to rapid jump of the subduction zone at the passive margin rim of the opposite side of the accreted block. Geological investigation and 40Ar/39Ar dating on the main tectonic boundaries of the Anatolide-Tauride-Armenian (ATA) block in Eastern Turkey, Armenia and Georgia provide temporal constraints of subduction and accretion on both sides of this small continental block, and final collisional history of Eurasian and Arabian plates. On the northern side, 40Ar/39Ar ages give insights for the subduction and collage from the Middle to Upper Cretaceous (95-80 Ma). To the south, younger magmatic and metamorphic ages exhibit subduction of Neotethys and accretion of the Bitlis-Pütürge block during the Upper Cretaceous (74-71 Ma). These data are interpreted as a subduction jump from the northern to the southern boundary of the ATA continental block at 80-75 Ma. Similar back-arc type geochemistry of obducted ophiolites in the two subduction-accretion domains point to a similar intra-oceanic evolution prior to accretion, featured by slab steepening and roll-back as for the current Mediterranean domain. Final closure of Neotethys and initiation of collision with Arabian Plate occurred in the Middle-Upper Eocene as featured by the development of a Himalayan-type thrust sheet exhuming amphibolite facies rocks in its hanging-wall at c. 48 Ma.

We produce a map of the stress pattern in and around Taiwan based on 200 earthquake focal mechanism solutions. These solutions were determined by using data from Taiwan Telemetered Seismographic Network, microearthquake surveys and WWSSN. The stresses are derived through a minimization of angles between the slip vector and the shear stress on each nodal plane considered as a fault, employing appropriate weighting factors. The whole set of focal mechanisms is divided into several groups, mainly according to apparent clustering of the event locations. The results show that the direction of maximum principal stress in Taiwan area is nearly horizontal and SE-NW on average. This is in good agreement with the direction of relative motion between the Philippine Sea plate and the Eurasian plate. In western Taiwan, the fan-shaped distribution of the maximum principal stress is consistent with the direction of Philippine Sea-Eurasian plate convergence through a simple model of viscous material indented by a rigid wedge. In the northeastern part of Taiwan, a nearly horizontal minimum principal stress oriented N–S is found for shallow depths; it occurs in a region of low seismic velocities, probably related to the back-arc activity of the Okinawa Trough. Down-dip compressional and down-dip extensional stresses have been identified in different depth ranges within the subducting slab of the Philippine Sea plate in the northern Taiwan; this may reflect the slab characteristics in this area. A complex stress pattern prevails in the Hualien area, at the junction between the Ryukyu subduction system and the Taiwan collision zone.

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International audience; ¾• present the results of ma.•netic fabric analysis obtained on samples of marine clays from sedimentary sequences in Norttzwestem Greece and Taiwan, in regions which have been submitted to large scale compressional events. •Ihe lithol • of the sediments is mainly composed of unmetamorphosed marls, siltstones and sandstones. These formations are folded and faulted at different scales. •ihe