Abstract The Diapir Fold Zone of the Carpathians is the most prolific onshore hydrocarbon area in Romania. Structural complexity, mainly due to the presence of salt, combined with poor seismic quality near and below the salt lead to contrasting structural models in the area. To gain insights into the mid-Miocene tectonic evolution, structural geometries and the effects of penetrative strain, we ran dual décollement scaled sandbox models with layered brittle and ductile materials. Results of two analogue models (20 and 33% shortening) revealed that the onset of the deformation sequence was mainly characterized by layer-parallel shortening. As shortening continued, a foreland-verging sequence of supra-salt detachment folds and sub-salt duplexes evolved. The sub-salt duplexes are located directly below the crests of the detachment folds, as the development of these large wavelength anticlines was related to sub-salt deformation. Salt flow was another controlling factor of the deformation style, as salt accumulated in the anticlinal cores and increased the coupling in the supra-salt synclinal axis. Our results offer insights into the effects of salt on the kinematic evolution of this area, help to predict geometries in areas of poor seismic quality, and highlight the important contribution of penetrative strain on deformation and reservoir quality.

Abstract Oil and gas activities in Romania cover a long time interval from antiquity until the present day. Most importantly, the year 1857 represents the starting point for industrial production in Romania when three world oil firsts were achieved: the first country with a crude oil production formally recorded in domestic and international statistics (275 tons); the first petroleum industrial refinery, located in Ploiești, with a processing capacity of 7.5 tons/day; Bucharest became the first city in the world to have public illumination, using lamp oils. After 1857, the evolution of the oil and gas industry in Romania was controlled by important historical events: World Wars I and II, the communist regime (1945–89), and the post-communist period (1990–today).

Abstract The geological understanding of the opening of the Western Black Sea Basin appears to be quite far from being reasonably resolved. The main faults used in the existing map-view reconstruction schemes are either very poorly defined (West Black Sea fault) or simply nonexistent as interpreted earlier (West Crimean fault) and therefore they need be redefined or replaced by other structural elements. Various kinematic elements and facies boundaries on the conjugate margins of the Western Black Sea (i.e. , the Bulgarian, Romanian and Ukrainian margin in the northwest versus the Turkish margin in the southeast) appear to be a key in constraining the opening geometry of the basin. The along-strike changes in the synrift structural pattern of the Bulgarian-Romanian margin, reflecting contrasting crustal rheologies inherited from prerift deformational phases, do appear to have their counterparts in the offshore part of the conjugate Turkish margin including the Pontides. A correlation of regional 2D reflection seismic and well data, and the critical review of the relevant onshore geology did provide some preliminary corresponding tie-points to constrain the kinematics of the basin opening. If the European margin is fixed in a kinematic reconstruction, the clockwise opening of the rift basin occurred along northwest–southeast trending transform faults around an Euler rotation pole positioned to the southwest of the present Black Sea. The rotational element in the opening of the Western Black Sea Basin, as opposed to the dominantly translational kinematics used in some of the existing kinematic models, is also supported by the broadly triangular shape of oceanic crust imaged in the basin center.

Abstract A regional, long-offset 2D reflection seismic grid that images the basin to a depth of ~30–40 km has been studied across the entire Western Black Sea Basin (WBSB). Mapping the structure and the stratigraphy of the basin on these transects provides valuable insights into the basin dynamics. An approximately 50–150 km wide zone (Turkish margin and Ukrainian sector, respectively) that roughly agrees with the present-day shallow shelf area corresponds to unstretched continental crust having a thickness of 35 km. Normal faults detach at a depth of about 15–20 km, marking the brittle-ductile transition zone. Some of the rift-related normal faults can be shown to be a re-activation of the older structural grain. Basinward, there is a distinct segment of the margin consisting of stretched continental crust and the interpreted Moho reflection located at about 20 km. The width of this zone is fairly uniform in the Bulgarian-Romanian-Ukrainian sector (80–110 km) but is much less on the Turkish side (30 km). In the central part of the basin, we interpret two distinct basement types. In the East, between the Ukraine and Turkey, there is a transparent 7 km thick seismic facies interpreted to consist of oceanic crust. The zone occupied by this crust has a broadly triangular shape. The center of the basin in the Bulgaria-Turkish sector shows a strikingly different seismic facies: rotated fault blocks, fault planes, magmatic intrusions, and large paleo-volcanoes representing extremely stretched continental crust, very much akin to that described in other passive margins (i.e. , offshore Iberia). Assuming plane strain deformation and constant crustal area on the 2D lines during and after the rifting, we calculate approximately 250 km of extension in the eastern part of the WBSB, and progressively smaller values to the west; i.e. , ~110 km at the westernmost seismic line. High extension values also correlate well with the position of the oceanic crust. This systematic variation in stretching values and crustal types is best explained by assuming clockwise rotation of Turkey away from the conjugate margins on the northwest.