RomUkrSeis is a controlled source wide-angle reflection and refraction (WARR) profile acquired in August 2014. It is 675 km long, running roughly SW-NE from the Apuseni Mountains in Romania and the Transylvanian Basin, crossing the arc of the Eastern Carpathian orogen and terminating in the East European Craton (EEC) in SW Ukraine. Wellconstrained 2-D ray-tracing P-and partly S-wave velocity models have been constructed along the profile from 348 single-component seismic recorders and eleven shot points. The Eastern Carpathian arc formed in the Cenozoic and have obscured the pre-existing Teisseyre-Tornquist Zone (TTZ), which is a transition zone between the Precambrian EEC and continental terranes accreted to it from the southwest in the Palaeozoic. The TTZ is characterised by low-velocity through its entire crust (6.0-6.3 km/s) and a considerable width (~140 km). It is interpreted as EEC crust stretched during rifting and continental margin formation in the Neoproterozoic and early Palaeozoic. The crust of the TTZ has a structure wherein an upper body of ~40 km width comprising Outer Carpathian (V p 4.9 km/s) and Late Palaeozoic-Mesozoic (V p 5.4 km/s) units to 15 km depth lies above a wider, deeper one of inferred Neoproterozoic-early Palaeozoic strata. The crust of the Transylvanian Basin and Apuseni Mountains is relatively thin (~32 km). A high-velocity body at 4-12 km depth in this area is interpreted as a rootless fragment of an ophiolite complex exposed at the surface in this area. The lower crust beneath the Transylvanian Basin displays higher velocities than adjacent segments. Moho topography is strongly differentiated along the profile, varying from 32 to 50 km. The Moho shape, especially in the area between the Inner and Outer Carpathians, suggests a NE dip and, hence, thrusting of the Tisza-Dacia lowermost crustal and upper mantle units under the TTZ domain which, in turn, could be thrust under the cratonic (EEC) block.
1И нститут гео ф и зи к и им. С.И. С убботина НАН У краины, Киев, У краина 2Д он ецки й национальны й техни ческий университет, П окровск, Украина
The wide-angle reflection and refraction (WARR) TTZ-South transect carried out in 2018 crosses the SW region of Ukraine and the SE region of Poland. The TTZ-South profile targeted the structure of the Earth’s crust and upper mantle of the Trans-European Suture Zone, as well as the southwestern segment of the East European Craton (slope of the Ukrainian Shield). The ~550 km long profile (~230 km in Poland and ~320 km in western Ukraine) is an extension of previously realized projects in Poland, TTZ (1993) and CEL03 (2000). The deep seismic sounding study along the TTZ-South profile using TEXAN and DATA-CUBE seismic stations (320 units) made it possible to obtain high-quality seismic records from eleven shot points (six in Ukraine and five in Poland). This paper presents a smooth P wave velocity model based on first-arrival travel-time inversion using the FAST (First Arrival Seismic Tomography) code. The obtained image represents a preliminary velocity model which, according to the P wave velocities, consists of a sedimentary layer and the crystalline crust that could comprise upper, middle and lower crustal layers. The Moho interface, approximated by the 7.5 km/s isoline, is located at 45—47 km depth in the central part of the profile, shallowing to 40 and 37 km depth in the northern (Radom-Łysogуry Unit, Poland) and southern (Volyno-Podolian Monocline, Ukraine) segments of the profile, respectively. A peculiar feature of the velocity cross-section is a number of high-velocity bodies distinguished in the depth range of 10—35 km. Such high-velocity bodies were detected previously in the crust of the Radom-Łysogуry Unit. These bodies, inferred at depths of 10—35 km, could be allochthonous fragments of what was originally a single mafic body or separate mafic bodies intruded into the crust during the break-up of Rodinia in the Neoproterozoic, which was accompanied by considerable rifting. The manifestations of such magmatism are known in the NE part of the Volyno-Podolian Monocline, where the Vendian trap formation occurs at the surface.
The oil and gas fields of Forecarpathian oil and gas region are compared with the structure of earth’s crust and regional faults. Most of the oil and gas condensate fields are localized in Borislav-Pokutia nappe over Precarpathian Fault zone. The majority of gas fields are located in under thrusting zone of the Sambir fault, which is a gently dipping detachment connected with the Forecarpathian fault and other faults of autochthonous basement. The regional gravity low of Carpathian Foredeep is also limited from northeast by the Sambir fault and from the southwest by the Uzhok fault. The Forecarpathian fault tends to the central part of gravity low. Transverse Tyachev-Nadvorna fault displaces the gravity low and delimits the oil and gas condensate fields. Velocity model along the wide-angle reflection and refraction PANCAKE profile shows a deep (25 km) sedimentary trough under the Carpathian Orogen. The Forecarpathian fault coincides with a jump of the Moho under the trough. Along the RomUkrSeis profile under Carpathian Orogen there were revealed a sedimentary trough as deep as 15 km and a low-velocity domain under the trough. From northeast, the trough is limited by the Forecarpathian fault, which goes up to the keel structure of the Moho discontinuity. Structure of the trough under Carpathian Orogen reflects development of East European Platform margin. The earliest stage of the formation of Baltica paleocontinent passive margin is seen in the structure of the trough’s lower part. Autochthonous basement under Borislav-Pokutsky and Skiba nappes includes a Riphean Massif limited by the Krakovets, Forecarpathian and Uzhok faults. The oil and gas condensate fields are located above the Riphean Massif. The purpose of this article is to analyze the fault system and the structure of the earth’s crust in the Forecarpathian oil and gas region, as well as their relationship with the distribution of oil and gas deposits, taking into account new WARR profiles and other geological and geophysical data.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.