Orogenic extension has been demonstrated to generate lower crustal exhumation observed in metamorphic core complexes. Observations and modelling have shown that orogen parallel extensional domes are challenging to constrain due to the superposition with coeval or subsequent geodynamic processes, such as orogenic thrusting, magmatism, or the evolution of subducted slabs. We utilise outcrop and micro scale observations to structurally quantify the original nappe stack burial and extensional exhumation structures of one such dome in the Macin unit of the European North Dobrogea orogen. The results demonstrate an initial top to NE nappe stacking associated with the previously defined Late Carboniferous - Permian burial metamorphism, which affected a mafic protolith and its sedimentary cover. This burial was followed by Triassic extensional exhumation, retrograde metamorphism, magmatism and top to SE ductile shearing, which created a newly identified major detachment and orogen-parallel extensional dome. The kinematic study is furthermore complemented by a lowtemperature fission track thermochronology performed to discriminate the extensional exhumation from the effects of subsequent thrusting. The thermochronology demonstrates that the Triassic extensional dome was subsequently affected by a Jurassic-Early Cretaceous exhumation, which is a novel quantification of the previously defined Cimmerian thrusting. Our results infer a new interpretation of the Macin unit as a Palaeotethys ophiolitic suture zone, which contains a typical Hercynian metamorphic core-complex of relatively small dimensions. When compared with other similar larger structures observed elsewhere, our results show that smallscale orogen-parallel extensional domes can also develop at high temperatures during or after the main stage of nappe stacking metamorphism.

The Carpathian Region, located at the edge of the East European Platform, presents a unique tectonic setting where major deformation associated with subduction and collision appears to have ceased around 8 million years ago. Yet vertical movements and seismicity continued afterward till the present day, suggesting ongoing crustal deformation and challenging our understanding of intraplate earthquakes and the processes driving these phenomena in an area considered a stable continental interior. In this study, we analyze over two decades of continuous GPS (cGPS) data from 143 permanent stations to estimate both horizontal and vertical crustal motions, constructing the most accurate model of crustal deformation in the region to date. The estimated velocity field indicates a southward drift of the South Carpathians and Moesia relative to Eurasia, with velocities ranging from 0.5 to 2 mm yr(-1). We detect a more complex pattern of vertical uplift and subsidence in the foredeep, challenging a previously held view that this region is solely subsiding. This pattern may reflect localized uplift in response to processes such as the Vrancea Slab break-off beneath the South-East Carpathians. Crustal-scale active faults accommodate the observed differential motion, fragmenting the foreland. Furthermore, using a regularized horizontal velocity vector field, we estimate strain rate variations, maximum shear strain, and dilatation patterns across Romania, which align with observed stress regimes and earthquake mechanisms. This agreement validates our results and indicates an influence of surface plate kinematics on the observed seismicity, in addition to the deep Vrancea Slab dynamics. Our findings provide insights into the causes of crustal deformation at the transition between active collision zones and stable continental platforms, enhancing our understanding of intraplate seismicity in regions traditionally considered tectonically stable.

Abstract The Earth's surface is continuously transformed, with deep and superficial processes contributing to the present-day morphology. Evaluating the contribution of each process and interaction between tectonics, climate, and human activities is difficult, especially in areas with relatively low crustal deformation. With this study, we aim to better understand the tectonic and sub-surface geodynamic processes that result in (small) surface motions in Romania. We are particularly interested in the Eastern Carpathians Bending Zone (Vrancea region), where strong deep earthquakes occur. Furthermore, we are focused on the interaction between the Eurasian, and Aegean tectonic plates. For this purpose, we processed more than 20 years of cGPS data from various networks in Romania (more than 100 stations), using the GipsyX software. To put our results in a broader perspective, we also included similar results published in open-source online literature including countries around Romania. Combining all these solutions we generated a velocitiy horizontal and vertical velocity fields for this extended region. All solutions were converted to the Eurasian tectonic reference plate in the ITRF14 plate rotation model. We find that in general, the horizontal velocity vectors in Romania have small values, ranging from 0.0 mm/yr in the north to 1.5 mm/yr in the south, and notably, the majority of stations indicate a subtle yet significant downward motion of 1.0 -2.0 mm/yr. In contrast, to our expectations, we did not find any significant horizontal and vertical motions in the Vrancea region. The horizontal motions exhibit a strong, generally southward, and gradually increasing trend, starting south of the South Carpathians. The trend is in the direction of the tectonic plates in southeast Europe. It means that the intraplate deformation zone extends to south Romania. The observed patterns contribute to our understanding of intraplate deformation and emphasize the need for continued regional research.Keywords: crustal deformations, GPS, geophysics, tectonics AcknowledgmentsThis paper was carried out within Nucleu Program SOL4RISC, supported by MCI, project no PN23360101, and PNRR- DTEClimate Project nr. 760008/31.12.2023, Component Project Reactive, supported by Romania - National Recovery and Resilience Plan

The Northern Dobrogea Orogen is the onshore segment of the southeastern termination of the Trans-European Suture Zone, the most prominent tectonic boundary of Europe, and was affected by multiple superposed deformation episodes in the Paleozoic and Mesozoic. Contrary to the widely held notion that the North Dobrogea Orogen has experienced only very mild and local deformation since the mid-Cretaceous, our (U-Th)/He analyses on apatites from Precambrian, Paleozoic, and Triassic basement and cover rocks indicate a well-defined and widespread episode of cooling/exhumation starting in the late Miocene. The high level of data coherence and the fact that all tectonic units of North Dobrogea have been affected by such episode warrants a geological explanation of supra-regional extent. Miocene cooling/exhumation in Dobrogea can be placed in a larger framework of coeval intraplate compressional deformation affecting a wide area ranging from the Greater Caucasus to the Romanian sector of the Black Sea continental shelf. We propose that the structural inversion of inherited structures in the study area is a distant echo of the Arabia-Eurasia hard collision, which started in the midMiocene some 1200 km away to the southeast. Low-temperature thermochronologic data for the area north of the Bitlis-Puturge suture zone of SE Anatolia indicate that the tectonic stresses related to the Arabian collision were transmitted efficiently in the Eurasian hinterland over large distances, focusing preferentially at rheological discontinuities located as far as the northern shores of the Black Sea. Late Miocene far-field deformation in the hinterland of the Arabia-Eurasia collision zone decreases gradually westward from the rapidly exhuming Greater Caucasus, located in front of the area of maximum indentation, through Crimea, to the Odessa shelf and Dobrogea, where deformation has been significantly less and therefore remained underestimated until now.

We aim to define a mechanism for the formation of outcrop-scale structures associated with the formation of regional asymmetric folds with overturned flanks crosscut by high-angle reverse faults in sediments characterized by contrasting rheological alternances. Although such regional "scale-folds" are often observed, a quantitative analysis of this deformation type is still needed. One place where outcrop-scale structures associated with the formation of regional scale-folds are well-observed is the Marginal Folds unit of the East Carpathians in Europe. Contrasting rheological alternances driving the formation of scale-folds are created by deep-water turbidites, pelagic sediments and more shallow-water deposits. We have combined new field structural observations with existing depth constraints from wells and seismic data to define the deformation history and analyse its relationship with the rheological stratification. Deformation starts with the formation of detachment folds and continues with the formation of regional asymmetric folds by gradual thinning along their flanks and thickening in hinges, accommodated by omission and duplication shears, as well as hinge-collapse structures. As shortening continues and deformation gradually exaggerates the regional scale folds, it undergoes reverse faulting that gradually steepens and truncate the overturned foreland flanks of folds in a forward-breaking sequence. This deformation is followed by out-of-sequence overthrusting and formation of hinterland-dipping duplexes and backthrusting. The result is a dominant sub-vertical position of the observed strata and closely spaced reverse faults that formed gradually during the intense folding. These findings demonstrate a new kinematic and structural genetic type of deformation that can be applied elsewhere for structural or applied studies.

Caves are ideal environments for preserving quantifiable deformational indicators in orogenic areas, as they are conditioned by regional tectonics. The caves and karst of Isverna, developed in the Barremian-Aptian limestones of the Danubian sedimentary nappes (Southern Carpathians, SW Romania), expose formerly undetected evidence of compressional tectonics, overlapping older structures related to décollement and deformation of the underlying Turonian-Senonian tectonic mélange. The Danubian domain (the distal part of the Moesian Platform) was incorporated into the Carpathian Orogen during the Late Cretaceous subduction of the Ceahlău–Severin Ocean and collision with the continental Dacia mega-unit. Subsequent Eocene–Oligocene orogen–parallel extension led to the development of a metamorphic core complex and detachment faults, constructing a complicated arcuate fault system around the Moesian Platform during the Late Miocene strike-slip deformation. The integrated analysis of structural, kinematic, and geomorphological data indicates a connection between the strike-slip deformation and the subsequent shortening, exhumation and surface exposure of Cerna Nappe within the Isverna shear zone. Four main evolutionary stages of the Danubian thin-skinned units in the central Mehedinți Mountains were distinguished from cave and karst geology, and illustrated in a detailed 3D model: i) Initial décollement and mélange deformation during the Alpine nappe stacking; ii) Extensional décollement toward SE; iii) Dextral shearing and WNW-ESE contraction; iv) Karstification and cave development. Most structural and kinematic markers recorded within the limestones of the Cerna Nappe date from stage (iii), whereas older structures were better preserved in the tectonic mélange of the Lainici Nappe. The resulting model could be further integrated into the polyphase tectonic evolution of the Southern Carpathians and their relation with the Moesian Platform. This study demonstrates the utility of caves and karst for constraining the chronology of tectonic deformations in complex structural systems and for reconstructing more refined conceptual 3D models.

The Carpathian belt is one of Europe's major metallogenic provinces, where magmatic ore mineralization is associated with the past subduction environment. The upper crust is mapped for the first time in the Northeast Carpathian Volcanic Arc using magnetotelluric data inversion. The obtained 3-D electrical resistivity model is interpreted in conjunction with geological information and magnetic anomaly data. The model illustrates the deep magmatic plumbing system including kilometer-scale plutonic bodies at a depth of 2-7 km. The model implies that the transport of magma and fluids in the uppermost crust was controlled by pre-existing faults and d & eacute;collement horizons. Present ore mineralization, mined since historical times, can be attributed to an electrically conductive conduit that is mapped from the surface to a depth of about 30 km. It is suggested that this conduit connected a shallow magmatic chamber to a deep source region in the southeast during late Miocene time. An observed northwest deflection of the deep magmatic conduit at a depth of more than 10 km may explain the spatial gap in the distribution of the Miocene volcanic activity along the Eastern Carpathians. The Carpathian Mountains have long been exploited for their metal ore deposits, which have been associated with the subduction of tectonic plates. Studying the natural variations of the regional electric and magnetic fields, we estimate the distribution of subsurface electrical resistivity. Subsurface electrical structures are interpreted as deep magma systems and large plutonic bodies. The interpretation implies that regional volcanic activity has been controlled by faults, large fractures in geologic formations, and detached strata. Specifically, historic mining can be attributed to a large conductive body that can be mapped from surface to about 30 km. Data suggest that this body, which could represent a pathway of magmatic fluids, connects to a deep, southeastern mantle source region. 3-D magnetotelluric survey in northeast Carpathian Mountains elucidates the structure of the Miocene volcanic province New data reveal shallow magmatic-hydrothermal system connected to a deep source region via an inclined conductive conduit Centuries-old mines align with an electrically conductive layer interpreted as a clay alteration related to hydrothermal activity

This study presents the analysis of Upper Triassic sediments from five locations in North Dobrogea (Romania) and the Black Sea. Microfacies analyses on thin sections from the Frecăţei log reveal a shallowing trend and likely an increase in energy upward into the section. The oldest part of the log is characterised by deposition of mudstones transitioning to wackestones, with an increase of bivalves. Similar wackestones are observed in the Izvoarele and Rândunica logs, i.e. microfacies with abundant bivalves, some foraminifera and echinoderms. The offshore boreholes 816 and 817 Lebăda Vest (core CM 9 and CM 31) seem to have been deposited in a basinal or distal marine shelf environment indicated by the presence of mudstones with rare bioclasts. In contrast, sample CM 10 from borehole 816 LV is a micritised grainstone suggesting a deposition in a shallower, higher energy environment. Scanning electron microscope observations reveal a moderate diagenetic alteration in all studied samples, mainly due to dissolution. Two calcareous nannofossil species: Prinsiosphaera triassica triassica and Eoconusphaera zlambachensis were commonly observed in sample F of the Frecăţei log, allowing for assignment of the sediments to the Rhaetian age. Two coccoliths were also observed in sample F of Frecăţei log and sample CM 9 of the borehole 816 LV indicating the presence of coccolithophorids within the study region. This discovery constitutes the first confirmed record of well-preserved, determinable Upper Triassic calcareous nannofossils in the Palaeo-Tethys Ocean.

The Ţicău area (NW Romania) is part of the collisional zone between the Tisza and Dacia mega‐units. Imaging of Ţicău area's subsurface geological structure will contribute to the understanding of the processes, which controlled its tectonic evolution. Analysis of outcrops provides accurate information for the building of kinematic sections used to explain the small‐scale deformations of sedimentary formations, such as those developed south of the Ţicău mountains. Imaging of large‐scale deformations requires analysis of data recorded and/or measured over a wider area. We use Seismic Interferometry by cross‐correlation on ambient noise recorded along with a line located north of the Ţicău mountains. The passive seismic section obtained after virtual body‐wave reflections processing displays folded and faulted Paleogene formations, which are in good agreement with the observations on outcrops found to the south of the Ţicău mountains. The active‐source data recorded along with the same line are too noisy for interpretation.

We present new sedimentological, petrographical, palaeontological and detrital zircon U–Pb data on late Oligocene–early Miocene sedimentary rocks of the thin‐skinned thrust belt of East Carpathians. These data were acquired to reconstruct the sedimentary routing system for two compositionally different turbidite fans made of the regionally extensive Kliwa and Fusaru formations. On the eastern margin of the Moldavides foreland basin, large low‐gradient river systems draining the East European Platform provided well‐sorted quartz‐rich sand forming deltas on wide shallow shelves and thick Kliwa submarine fans. Due to the westward subduction of a thinned continental plate, the western basin margin was characterized by short, steep‐gradient routing systems where sediment transport to deep water was mainly through hyperpycnal flows. The Getic and Bucovinian nappes of the East Carpathians and the exhumed Cretaceous–Early Palaeogene orogenic wedge fed Fusaru fans with poorly sorted lithic sand. The Fusaru fans trend northwards in the foredeep basin having an elongate depocentre, interfingering and then overlapping on the distal part of the Kliwa depositional system due to the eastward advance of the Carpathian fold‐and‐thrust belt. A smaller sediment input is supplied by southern continental areas (i.e. Moesian Platform, North Dobrogea and potentially the Balkans). In general, the sandstone interfingering between distinct basin floor fan systems is less well documented because the facies would be similar and there are not many systems that have a distinct sediment provenance like Kliwa and Fusaru systems. This case study improves the understanding of regional palaeogeography and sedimentary routing systems and provides observations relevant here or elsewhere on the interfingering turbidite fan systems.

Situated at the junction between the Eastern Carpathians Mountains, the Pannonian and the Transylvanian basins, the Baia Mare region (Romania) has a complex geological history that witnessed the interaction among the three main tectonic provinces. Here, we report results from new seismic reflection measurements that provide modern information about the subsurface geological structure. The integrated analysis of the newly acquired and vintage seismic reflection data from the study area reveals details about the architecture of the Palaeogene and the Neogene deposits at the contact between the northeastern Pannonian and northwestern Transylvanian basins. In particular, it unveils a fault zone that most probably controlled the tectonic evolution of the eastern Pannonian and Transylvanian basins. A better understanding of the crustal structure and tectonic features in the study area is a first step into evaluating the geothermal potential of the region.

The upper continental slope offshore Romania is a complex area hosting turbidite deposits, multiple types and ages of deep-seated faults, gas hydrates, gas-escape features, and numerous Mass Transport Deposits (MTDs). Multi-scale seismic data sets (2D-high-resolution and near-bottom very high-resolution) were used to study the interaction between such disparate geological features and determine their impact on slope stability. At least five main paleo-valleys have been identified in the north of the Viteaz (Danube) canyon/valley. The most recent channelized systems linked to these valleys formed over a basal layer of MTDs. These MTDs are associated with an unconformity corresponding to the Base Neoeuxinian Sequence Boundary formed during the last major sea-level fall. This erosional surface shows scarp alignments that coincide with underlying faults. We argue that gravity-driven fault reactivation, with possible upward gas/fluid migration along these faults, is a determinant factor controlling sedimentary instabilities. Numerous MTDs are also observed during channel-levees building and reveal local sediment instabilities related to localized erosional process in the canyon. Finally, MTDs recorded within the upper draping unit, suggest that sediment instability also occurred during recent sea level highstand. Sediment pulse, seismicity, and gas hydrates dynamics can also play a determinant role in sediment instability throughout the sediment record.

Summary The Romanian Seismic Catalogue has been contaminated in the last period with events from anthropic sources, especially in the regions with active quarry activities. In this paper, we chose as the study area the Targu-Jiu zone, located in Southern Carpathians, where the National Seismic Network (RSN) recorded both crustal events and quarry blasts. For discrimination purposes, the events recorded in a 10-km radius circle around each quarry will be analysed through several methods, to properly identify the quarry blasts. Thus, statistical methods are used, as well as the cross-correlation technique for the recordings of Gura Zlata (GZR) seismic station. In the first stage, a statistical analysis of the events recorded in the quarries area is performed, based on depth intervals, magnitude, working hours and days of the week. The spectrogram analyses are investigated with the DTK-GPMCC and DTK-DIVA extended CTBTO NDC-in-a-box packages developed by the CEA-DASE. The events identified on the seismic recordings are used as templates for the cross-correlation method applied to the events recorded by the GZR for the 2010–2020 time interval.

Romanian seismicity is mainly confined to the Eastern Carpathians Arc bend (ECAB), where strong subcrustal earthquakes (magnitude up to 7.9) are generated in a narrow lithospheric body descending into the mantle. The seismic activity in the overlying crust is spread over a larger area, located mostly toward the outer side of the ECAB. It is significantly smaller than subcrustal seismicity, raising controversies about possible upper mantle-crust coupling. A significant earthquake sequence took place in the foreland of the ECAB triggered on 22 November 2014 by a mainshock of magnitude 5.7 (the greatest instrumentally recorded earthquake in this region) located in the lower crust. The mainshock triggered a significant increase in the number of small-magnitude events spread over an unusually large area in the ECAB. The paper's goal is to compute the source parameters of the earthquakes that occurred during the aforementioned sequence, by empirical application of Green's function and spectral ratio techniques. Fault plane solutions are determined using multiple methods and seismicity evolution at regional scale is investigated. Our results highlight a still active deformation regime at the edge of the EE Craton, while the source parameters reveal a complex fracture of the mainshock and a very high-stress drop.

Geothermal energy is known as a renewable source that has little effect on environment, since no burning process is involved in the producing of thermal and electric energy. Geothermal water is considered an environmentally friendly energy source which is valuable especially in polluted areas. Our study area, the Baia Mare region, is located in the northwestern part of Romania, a region known as one of the most polluted environment in Romania due to its long-lasting local mining and metallurgical activities. Additional quantities of CO2 emissions resulted from the use of various, relatively cheap, heating sources by the local population. The main goals of our study are to evaluate the subsurface geothermal potential of the Baia Mare area and to identify promising geothermal exploitation sites. Heat flow values in this area are among the highest in Romania. We therefore plan to combine geological, geophysical, geochemical and hydrogeological data (geo-data) in order to provide a geoscientific solution for increasing the geothermal energy production in this part of Romania. Our research program contains surface geological mapping, geophysical surveys (active and passive seismic, magnetic, magnetotelluric and geothermal), geochemical analysis, hydrogeological surveys, modeling of geo-data and joint interpretation of geo-data. An initial 3D geothermal model will be built using existent geo-data. This model will help us to identify subsurface structures which show high potential for geothermal exploration. Interpretation of existent active seismic data collected during previous hydrocarbon exploration will provide information about the subsurface structural geology. The results of the new interpretation will be compared and correlated with the existent geological maps and sections for the study area. The magnetic data available in the public domain will be used to identify subsurface igneous bodies. The temperature data available from previous measurements will be used to build temperature-versus-depth distributions. These results will be analysed within a larger geodynamic framework. A pilot site will be selected after the analysis of the initial 3D geothermal model on which we plan to collect and record new geo-data. Data processing, inversion and modeling will be performed in order to create the final geothermal model with locations of promising exploitation wells.

The Istria basin, situated in the NW Black Sea, is composed of Mesozoic to Cenozoic successions. The opening of the Western Black Sea, including the Istria basin, initiated in the late Early Cretaceous. Rifting and expansion continued in the Late Cretaceous, while in the Late Paleogene a compressional regime settled. In the Middle Eocene, the Western Black Sea basin margin inverted, due to the collision of Pontides and Taurides belts (Okay and Tüysüz, 1999; Dinu et al., 2005). The continuing compression shaped this basin until the Middle Miocene (Ionescu et al., 2002).Tens of wells for hydrocarbon exploration were drilled in the Istria basin (Romanian offshore) since the 70’s. In this study, we have interpreted the acquired core reports containing litho- and biostratigraphic data. Based on identified calcareous nannofossil biozones, a continuous deposition was found in the Cenomanian-Maastrichtian interval. Lithologically, the Upper Cretaceous is composed of carbonatic rocks, such as limestones and marlstones, with intercalations of calcareous sandstones. The Eocene deposits are unconformably lying on Upper Cretaceous ones. Lithologically, the Eocene is characterized by alternating calcareous and siliciclastic sandstones. Biostratigraphy on planktonic and benthic foraminifers, as well as calcareous nannofossils, indicate a late Early Eocene to Middle Eocene age (i.e., late Ypresian to Bartonian).The observed large thickness variation, from W towards E in the Istria Basin, is a consequence of various tectonic settings. The western part (i.e., the Sinoe area) is situated in the hanging-wall of an inverted normal fault filled with Early Eocene deposits and was inverted by high angle thrust fault during the Late Eocene-Oligocene interval. In the E (i.e., the Lebǎda area), there is an uplifted normal fault foot-wall, showing a reduced thickness in comparison with the W (Munteanu et al., 2011). The erosion level increased eastward, removing the entire Upper Eocene and the top of the Middle Eocene. This feature may be linked to a large sea level drop towards the Eocene top, with subaerial erosion and development of large-scale canyons system at the self to slope transition, like the Plio-Quaternary Viteaz Canyon of the NW Black Sea.The financial support for this paper was provided by the Romanian Ministry of Research and Innovation, through the Programme Development of the National System of Research – Institutional Performance, Project of Excellence for Rivers-Deltas-Sea Systems No. 8PFE/2018.ReferencesDinu, C., Wong, H.K., Țambrea, D., Mațenco, L., 2005. Stratigraphic and structural characteristics of the Romanian Black Sea shelf. Tectonophysics, 410, 417-435.Ionescu, G., Sisman, M., Cataraiani, R., 2002. Source and reservoir rocks and trapping mechanism on the Romanian Black Sea shelf. In: Dinu, C., Mocanu, V. (Eds.) Geology and Tectonics of the Romanian Black Sea Shelf and its Hydrocarbon Potential. BGF Special Volume, 2, 67–83.Munteanu, I., Maţenco, L., Dinu, C., Cloetingh, S., 2011. Kinematics of back-arc inversion of the western Black Sea basin. Tectonics, 30, TC5004.Okay, A.I., Tüysüz, O., 1999. Tethyan sutures of northern Turkey. Geological Society, London, Special Publications, 156, 475-515.