Styrian Basin Research Articles

Geoenergy in the Styrian Basin

The Styrian Basin (SB) is the westernmost basin within the Pannonian Basin Complex and is located in SE Austria, where the crustal thickness decreases from more than 40 km to less than 30 km. It can be divided into the West and East Styrian Basin. The pre-Neogene basement includes Penninic and crystalline rocks overlain by Paleozoic rocks. The age of the basin fill ranges from the early to late Miocene. Despite a long hydrocarbon exploration history, only a single sub-economic gas field has been discovered. The lack of commercial deposits is probably due to limited source-rock quality and an unfavourable heat-flow history. In contrast, a significant number of geothermal wells with a cumulative length of >54 km have been drilled in the East SB. The main geothermal reservoirs are fractured Paleozoic carbonates and Miocene (Badenian) sandstones. Geothermal gradients in the SB are typically above 4°C/100 m. The hottest geothermal well (Frutura GT1) produces water with a temperature of 125°C (bottom hole temperature 138°C) from a depth of ∼3.3 km. Utilization of geothermal energy in the SB includes balneology, district and greenhouse heating, production of medical salt, CO 2 and electricity.

The Styrian Basin: an overview with new insights from seismic data

The Neogene Styrian Basin is the westernmost subbasin of the Pannonian Basin System. The last comprehensive studies on the basin were published in the last millennium. This overview of the current understanding of basin evolution is based on the re-interpretation of partly unpublished reflection seismic data and a wealth of sedimentological and stratigraphic studies performed during the last 25 years. Reflection seismic data indicate the presence of a major E to SE dipping detachment horizon within the pre-Neogene basement reflecting high-strain upper crustal extension during the early Miocene syn-rift stage of basin evolution. Fault block rotations caused subsidence in several subbasins, which developed often with marked asymmetric geometry. The maximum basin depth exceeds 4 km (Gnas Basin). Syn-rift deposits include thick alluvial fan and fan delta sediments overlain in the basin center by deeper marine pelitic rocks. Subduction-related magmatic activity commenced during the syn-rift stage and continued into the middle to late Miocene post-rift stage. Syn- and post-rift sediments are separated by the middle Miocene “Styrian Unconformity”. Shallow marine sedimentation, controlled by third- and fourth-order sea-level variations, prevailed during the early post-rift stage. The final stage of basin evolution was characterized by differential surface uplift, erosion, and Pliocene-Pleistocene basaltic magmatism.

The Fischbach Alps: A Geomorphological Record of late Neogene Uplift at the Eastern Margin of the European Alps

Abstract Low-relief surfaces at high elevations are peculiar features of the Eastern Alps that are best explained as relicts of morphological base levels that escaped erosive decay during uplift. To expand our knowledge of such surfaces in the Eastern Alps, the Fischbach Alps at the eastern end of the range are investigated. There, a large number of these elevated low-relief surfaces have been known for some time, but modern mapping is absent and their genesis is not well understood. A combined approach of field mapping, morphometric analysis of a digital elevation model and downstream projection of geomorphic equilibrium sections in river profiles was employed to: (i) create a geomorphological map of the region and (ii) to extract quantitative data from river profiles to infer the amount of uplift and incision. Six discrete levels of low-relief surfaces and relict landscapes are recognized at elevations between ~500 m and ~1600 m. Some of the lower levels are interpreted to relate to the well-known Trahutten, Landscha and Stadelberg levels, known from other parts of Styria, respectively. Mapped low-relief surface levels follow the northward directed topographic gradient in the mountainous region of the Fischbach Alps. The formation of elevated low-relief surfaces is consistent with a Piedmonttreppen model, where successive phases of tectonic uplift and tectonic quiescence led to a succession of incised landscapes and low-relief surfaces. However, the entire region south of the Murztal was also then tilted towards the Styrian Basin by about ~1–2°. Swath profile analysis for the Raab and Weizbach Klamm suggests a minimum of ~400–450 m incision since the formation of the so called Hubenhalt level. This implies that the geomorphic response to tectonic uplift after the formation of the higher Wolscheneck and Koralm relict landscapes led to an estimated incision of up to 1000 m (868±101 m), relative to the base level of today’s Styrian Basin at ~380 m. By comparing published age data to the presented mapping results, the onset for much of the uplift at the eastern end of the Alps is suggested to lie between ~4–7 Ma, before the formation of the Hubenhalt and Trahutten levels. Because the mapped levels correlate well with those in many other regions at similar elevations, a growing body of work now suggests that the underlying uplift event has a large wavelength.

Gravity inversion by second order approximation applied to the Styrian Basin (Austria)

AbstractAn approximative second order gravity inversion scheme by a truncated power series expansion is applied to derive the thickness of the Neogene, mostly clastic, sedimentary section of the Styrian Basins in South–East Austria, which are sub‐basins of the Pannonian Basin System. These sub‐basins with a derived thickness of up to 4 km are of interest for geothermal exploitation because of the increased geothermal gradient and heat flow observed in the Pannonian Basin in general and a geothermal gradient of 4°–5°/100 m measured in some wells in the Styrian Basin. The Styrian Basin also has been an area for hydrocarbon exploration in the past 50 years, with oil and gas show encountered in several exploration wells and one sub‐commercial gas discovery. The Miocene and Plio–Pleistocene volcanism in the Styrian Basin caused by Miocene crustal thinning is discussed in terms of the influence to the gravity inversion taking the aeromagnetic field into account. The volcanism is of relevance for the geothermal prospectivity but poses problems for the single layer‐based gravity inversion scheme. Results are discussed from a computational side comparing observed and calculated gravity fields but also the match with well data is discussed. In terms of gravity inversion methodology, the presented can be viewed as an approximative fast‐track approach.

Assessing uncertainties in landslide susceptibility predictions in a changing environment (Styrian Basin, Austria)

Abstract. The assessment of uncertainties in landslide susceptibility modelling in a changing environment is an important, yet often neglected, task. In an Austrian case study, we investigated the uncertainty cascade in storylines of landslide susceptibility emerging from climate change and parametric landslide model uncertainty. In June 2009, extreme events of heavy thunderstorms occurred in the Styrian Basin, triggering thousands of landslides. Using a storyline approach, we discovered a generally lower landslide susceptibility for the pre-industrial climate, while for the future climate (2071–2100) a potential increase of 35 % in highly susceptible areas (storyline of much heavier rain) may be compensated for by much drier soils (−45 % areas highly susceptible to landsliding). However, the estimated uncertainties in predictions were generally high. While uncertainties related to within-event internal climate model variability were substantially lower than parametric uncertainties in the landslide susceptibility model (ratio of around 0.25), parametric uncertainties were of the same order as the climate scenario uncertainty for the higher warming levels (+3 and +4 K). We suggest that in future uncertainty assessments, an improved availability of event-based landslide inventories and high-resolution soil and precipitation data will help to reduce parametric uncertainties in landslide susceptibility models used to assess the impacts of climate change on landslide hazard and risk.

Porosity, strength, and alteration – Towards a new volcano stability assessment tool using VNIR-SWIR reflectance spectroscopy

Volcano slope stability analysis is a critical component of volcanic hazard assessments and monitoring. However, traditional methods for assessing rock strength require physical samples of rock which may be difficult to obtain or characterize in bulk. Here, visible to shortwave infrared (350–2500 nm; VNIR–SWIR) reflected light spectroscopy on laboratory-tested rock samples from Ruapehu, Ohakuri, Whakaari, and Banks Peninsula (New Zealand), Merapi (Indonesia), Chaos Crags (USA), Styrian Basin (Austria) and La Soufrière de Guadeloupe (Eastern Caribbean) volcanoes was used to design a novel rapid chemometric-based method to estimate uniaxial compressive strength (UCS) and porosity. Our Partial Least Squares Regression models return moderate accuracies for both UCS and porosity, with R2 of 0.43–0.49 and Mean Absolute Percentage Error (MAPE) of 0.2–0.4. When laboratory-measured porosity is included with spectral data, UCS prediction reaches an R2 of 0.82 and MAPE of 0.11. Our models highlight that the observed changes in the UCS are coupled with subtle mineralogical changes due to hydrothermal alteration at wavelengths of 360–438, 532–597, 1405–1455, 2179–2272, 2332–2386, and 2460–2490 nm. These mineralogical changes include mineral replacement, precipitation hydrothermal alteration processes which impact the strength of volcanic rocks, such as mineral replacement, precipitation, and/or silicification. Our approach highlights that spectroscopy can provide a first order assessment of rock strength and/or porosity or be used to complement laboratory porosity-based predictive models. VNIR-SWIR spectroscopy therefore provides an accurate non-destructive way of assessing rock strength and alteration mineralogy, even from remote sensing platforms.

Seismic anisotropy in the mantle of a tectonically inverted extensional basin: A shear-wave splitting and mantle xenolith study on the western Carpathian-Pannonian region

Information on seismic anisotropy in the Earth's mantle can be obtained from (1) shear-wave splitting analyses which allow to distinguish single or multi-layered anisotropy and delay time of the fast and slow polarized wave can indicate its thickness, and (2) studying mantle peridotites where seismic properties can be inferred from lattice preferred orientation of deformed minerals. We provide a detailed shear-wave splitting map of the western part of the Carpathian-Pannonian region (CPR), an extensional basin recently experiencing tectonic inversion, using splitting data. We then compare the results with seismic properties reported from mantle xenoliths to characterize the depth, thickness, and regional differences of the anisotropic layer in the mantle.Mantle anisotropy is different in the northern and the central/southern part of the western CPR. In the northern part, the lack of azimuthal dependence of the fast split S-wave indicates a single anisotropic layer, which agrees with xenolith data from the Nógrád-Gömör volcanic field. Systematic azimuthal variations in several stations in the central areas point to multiple anisotropic layers, which may be explained by two distinct xenolith subgroups described in the Bakony-Balaton Highland. The shallower layer probably has a ‘fossilized’ lithospheric structure, representing former asthenospheric flow, whereas the deeper one reflects structures attributed to present-day convergent tectonics, also observed in the regional NW-SE fast S-wave orientations. In the Styrian Basin at the western rim of the CPR, results are ambiguous as shear-wave splitting data hint at the presence of multiple anisotropic layers. Spatial coherency analysis of the splitting parameters places the center of the anisotropic layer at ~140–150 km depth under the Western Carpathians, which implies a total thickness of ~220–240 km. Thicknesses estimated from seismic properties of xenoliths give lower values, pointing to heterogeneously distributed anisotropy or different orientation of the mineral deformation structures.

Paleovegetation and paleoclimate inferences of the early late Sarmatian palynoflora from the Gleisdorf Fm. at Gratkorn, Styria, Austria

The Gleisdorf Formation (Fm.) deposits in the clay pit at Gratkorn, Styria, Austria, are dated to 12.2–12 Ma, and are of late Middle Miocene age (late Serravallian or Sarmatian). To reconstruct the paleovegetation and estimate the paleoclimate at this important vertebrate site, the palynoflora close to the boundary between the vertebrate-bearing layers of the Gratkorn Fm. and the overlying limnic clay deposits of the Gleisdorf Fm. was investigated. Using the single-grain method, 140 palynomorphs were identified. The palynoflora suggests that the paleovegetation was characterised by well-drained lowland and upland forests, riparian forest, and swamp forests. Depending on the dominating tree species, lowland and upland forests might have had closed or more open canopies. Open habitats included wet meadows and shrublands. In addition, conifers were present in the swampy lowlands and the forested uplands. The most prominent paleoclimatic signatures of the palynoflora indicate a fully humid warm temperate climate, with hot to warm summers and cool winters (Cfa-, Cfb-climate), and a seasonal climate with cool and drier winters and hot to warm and wetter summers (Cwa-, Cwb-climate). Our results align with existing studies bordering the Styrian Basin and support the presence of subtropical to warm-temperate vegetation around Gratkorn during the Sarmatian.

Tiger shark feeding on sirenian – first fossil evidence from the middle Miocene of the Styrian Basin (Austria)

ABSTRACT Based on a shark-bitten partial skeleton of an immature sirenian (Metaxytherium cf. medium) from the middle Miocene of the Styrian Basin (Austria), we report on the oldest predator–prey interaction between tiger sharks and dugongs. The bite mark-bearing ribs and vertebrae are associated with seven teeth of Galeocerdo aduncus, which are otherwise rare in the fossil record of the Styrian Basin. The unique tooth morphology of the genus Galeocerdo is reflected by an unambiguous pattern of bite marks, which is repeatedly detected on one rib fragment. Similar bite marks were reproduced experimentally by using clay instead of bone. The obtained pattern is consistent with the observed bite marks on the sirenian rib fragment, which demonstrates that tiger sharks fed upon the Metaxytherium carcass. Furthermore, we also report on the first record of the angel shark Squatina sp. within the Styrian Basin.

Geochemical evolution of the lithospheric mantle beneath the Styrian Basin (Western Pannonian Basin)

The Styrian Basin is located at the westernmost part of the Carpathian-Pannonian region, in the transition zone between the Pannonian Basin and the Eastern Alps. The lithospheric mantle beneath the Styrian Basin (SB) was sampled by Plio-Pleistocene alkali basalts, which brought mantle xenoliths to the surface. Mantle xenoliths from the SB are mostly coarse granular, amphibole-bearing spinel lherzolites with microstructures indicating extensive annealing. Three geochemical events were recorded in the SB xenoliths. The initial, ancient partial melting event was followed by an old metasomatism, which formed lithological heterogeneities (e.g. websterite, dunite) occurring as veins, bands and layers. The most recent geochemical event recorded in the SB xenoliths is the migration of a hydrous alkaline melt originating from a nephelinitic melt source. This melt migrated from the asthenosphere, forming melt channels in the lithospheric mantle. Close to the channels, the metasomatic agent caused extensive amphibole and sparse phlogopite formation. This particular pargasite-phlogopite equilibrium mineral assemblage in the spinel facies was not described before in the literature based on our knowledge. The reaction caused significant enrichment in basaltic elements (such as Ti, Fe), K, light rare earth elements and incompatible trace elements such as Zr and Hf. Further from the channels, the metasomatic melt became enriched in volatiles (mainly H2O and CO2) and fluid mobile elements (e.g. U, Pb, Cl and P), but depleted in basaltic elements, K and LREE, which resulted in modal decrease of amphiboles. Previous studies suggested a dehydrating subducted slab beneath the Styrian Basin, however geochemical fingerprints of subducted slab derived fluids were recognized only in one xenolith. Mantle portions with different geochemical characteristics developed in the lithosphere laterally, however metasomatic fingerprints were erased later due to annealing and chemical re-equilibration at ambient mantle conditions. The Neogene evolution of the lithosphere overwrote the previous state of the upper mantle beneath the region, thus the signs of the most recent metasomatism by nephelinitic melts could have been only preserved due to this extensive annealing event.

Miocene syn-rift evolution of the North Croatian Basin (Carpathian–Pannonian Region): new constraints from Mts. Kalnik and Požeška gora volcaniclastic record with regional implications

Mts. Kalnik and Požeska gora volcaniclastic sequences hold valuable information concerning the Miocene syn-rift evolution of the North Croatian Basin, and the evolution of the Carpathian–Pannonian Region and the Central Paratethys. We present volcanological, high-precision geochronological, and compositional data of volcanic glass to constrain their tephrochronology, magmatic provenance, and timing of the initial Central Paratethys flooding of the North Croatian Basin. Based on CA-ID-TIMS U–Pb zircon ages (18.060 ± 0.023 Ma for Mt. Kalnik and 15.345 ± 0.020 Ma for Mt. Požeska gora) and coeval 40Ar/39Ar sanidine ages (18.14 ± 0.38 Ma and 18.25 ± 0.38 Ma for Mt. Kalnik and 15.34 ± 0.32 Ma and 15.43 ± 0.32 Ma for Mt. Požeska gora), Mt. Kalnik rhyolitic massive ignimbrites and Mt. Požeska gora rhyolitic primary volcaniclastic turbidites are coeval with Carpathian–Pannonian Region Miocene post-collisional silicic volcanism, which was caused by lithospheric thinning of the Pannonian Basin. Their affiliation to Carpathian–Pannonian Region magmatic activity is supported by their subduction-related geochemical signatures. Although Mts. Kalnik and Požeska gora volcaniclastics are coeval with the Bukkalja Volcanic Field Csv-2 rhyolitic ignimbrites, North Alpine Foreland Basin, Styrian Basin, Vienna Basin, and Dinaride Lake System bentonites and volcaniclastic deposits, reliable tephrochronological interpretations based on comparison of volcanic glass geochemical composition are not possible due to a lack of data and/or methodological discrepancies. Our new high-precision geochronology data prove that the initial Middle Miocene (Badenian) marine flooding of parts of the North Croatian Basin occurred at least ~ 0.35 Ma (during the NN4 Zone) before the generally accepted ~ 15 Ma maximum flooding age at the basin scale, calibrating the timing of the onset of the widespread “mid-Langhian” Central Paratethys flooding.

Event-Based Landslide Modeling in the Styrian Basin, Austria: Accounting for Time-Varying Rainfall and Land Cover

In June 2009 and September 2014, the Styrian Basin in Austria was affected by extreme events of heavy thunderstorms, triggering thousands of landslides. Since the relationship between intense rainfall, land cover/land use (LULC), and landslide occurrences is still not fully understood, our objective was to develop a model design that allows to assess landslide susceptibility specifically for past triggering events. We used generalized additive models (GAM) to link land surface, geology, meteorological, and LULC variables to observed slope failures. Accounting for the temporal variation in landslide triggering, we implemented an innovative spatio-temporal approach for landslide absence sampling. We assessed model performance using k-fold cross-validation in space and time to estimate the area under the receiver operating characteristic curve (AUROC). Furthermore, we analyzed the variable importance and its relationship to landslide occurrence. Our results showed that the models had on average acceptable to outstanding landslide discrimination capabilities (0.81–0.94 mAUROC in space and 0.72–0.95 mAUROC in time). Furthermore, meteorological and LULC variables were of great importance in explaining the landslide events (e.g., five-day rainfall 13.6–17.8% mean decrease in deviance explained), confirming their usefulness in landslide event analysis. Based on the present findings, future studies may assess the potential of this approach for developing future storylines of slope instability based on climate and LULC scenarios.

40AR/39AR GEOCHRONOLOGY USING HIGH SENSITIVITY MASS SPECTROMETRY: EXAMPLES FROM MIDDLE MIOCENE HORIZONS OF THE CENTRAL PARATETHYS

40Ar/39Ar radio-isotopic dating of volcanic tuffs intercalated in sediments can provide high accuracy age control on the deposition of sedimentary rocks. State-of-the-art mass spectrometers such as the ARGUS VI+ are able to acquire highly precise ages for relatively small single grains (~90-250 μm for Miocene samples). Single grain measurement can provide insight into the sometimes complex age distributions within volcanic tuffs. The results show that 40Ar/39Ar ages based on multiple grain fusions will not necessarily reflect eruption ages, which can lead to (slight) overestimation of the depositional age. The paper compares multiple and single grain data from different Miocene tuffs in the Central Paratethys, which plays an important role in the establishment of a geological time frame for this area. The examples come from three middle Miocene tuff horizons that span from the Badenian transgression to the Badenian-Sarmatian Extinction Event. The new ages obtained from the Quellgraben section in the Styrian Basin (14.31±0.27 Ma and 14.03±0.04 Ma) are much younger than the previous dating and together with the new data from the Bernhardsthal-4 well, Vienna Basin (15.12±0.19 Ma) indicate, that the Badenian (Langhian) marine flooding did not reach this area before 15.2 Ma. The new weighted mean age of 12.56±0.10 Ma from the Kamenica nad Hronom section in the Danube Basin dates the transition from marine to terrestrial setting, which is possibly connected with a sea level lowstand at the beginning of the Sarmatian.

A földköpeny reológiai kutatása: mennyiségi Fourier transzformációs infravörös spektrometria alkalmazása egy Persány hegységi xenolit példáján

A felsőköpenyből származó xenolitok kőzettani és geokémiai vizsgálatával közvetlen ismeretekhez juthatunk a litoszféra fizikai és kémiai állapotáról. Ezen információk birtokában kiszámíthatók a xenolitok által jellemzett köpenylitoszféra legfontosabb geofizikai tulajdonságai (pl. szeizmikus hullámsebesség, fajlagos vezetőképesség, effektív viszkozitás). Ezek a fizikai jellemzők meghatározók a geofizikai mérések eredményének értelmezésében, és így a kutatott régió geodinamikai fejlődésének megértésében. Jelen tanulmányban azt mutatjuk be, hogy akár nyomnyi mennyiségű „víz” (helyesebben szerkezeti hidroxil) jelenléte a földköpeny névlegesen vízmentes ásványaiban (röviden NAM elegyrészek az angol „Nominally Anhydrous Minerals” kifejezés alapján) milyen kiemelkedő jelentőséggel bír a litoszféra fizikai viszonyaira és hogyan reagál a rendszer kémiai összetételére. A felsőköpeny geokémiai és geodinamikai kutatásában alkalmazott spektrometriai technikák közül a Fourier transzformációs infravörös spektrometria (FTIR) a NAM elegyrészek szerkezeti hidroxil-tartalmának tanulmányozásával a kőzetek fizikai viselkedéséről (pl. olvadási hőmérséklet, deformálhatóság, fajlagos vezetőképesség stb.) és bizonyos kémiai tulajdonságairól (H-tartalom) ad képet. Kísérleti kőzettani eredmények alapján a H+ töltéskompenzáló kationként vakanciákba önállóan, vagy csatolt helyettesítést létrehozva más kationokkal (pl. Al3+ vagy Ti4+) együtt tud a NAM elegyrészekbe beépülni. A vakanciák esetében a H+ valamelyik koordináló oxigénhez csatlakozva OH- (szerkezeti hidroxil) gyököt hoz létre. Ritkán a H+ önállóan, intersticiális helyzetben vagy Li+- és Na+-hoz csatlakozva szerkezeti hidroxil formájában is előfordulhat a rácsközi térben. A beépülés jellege függ a rendszer összetételétől (pl. Ti-tartalom), az oxigén, H2O és SiO2 aktivitásától, az oxigén fugacitástól és a nyomástól. A beépülés módján kívül a NAM elegyrész pontos szerkezeti hidroxil tartalmát is meg lehet határozni mikro-FTIR spektrometriával. A szerkezeti hidroxil koncentrációt konvencionálisan molekuláris víz egyenértékben és ppm tömegrészben vagy mol %-ban fejezzük ki. A nem poláros mikro-FTIR módszer térnyerése az utóbbi időben jelentős áttörést hozott, hiszen a kis szemcseméretű (<0,7 mm) természetes és kísérleti kőzetek ásványainak elemzésére is lehetőség nyílt, amelyre a tradicionálisan megbízhatónak gondolt poláros mikro-FTIR módszer nem adott módot. Tanulmányunk egyik célja, hogy részletes áttekintést adjunk a mikro-FTIR alkalmazásáról a NAM szerkezeti hidroxil tartalmának vizsgálatához.A nem poláros mikro-FTIR módszert ma már világszerte alkalmazzák, a Kárpát-Pannon régió felsőköpeny kutatásában is nagy szerepet kap. Alkalmazását a Persány-hegységi Vulkáni Terület felső-köpeny xenolitjain mutatjuk be, összehasonlítva korábbi munkákkal a Kárpát-Pannon régióból, kiemelve az eredmények felhasználhatóságát a geofizikai adatok értelmezéséhez és így a Kárpát-Pannon régió geodinamikájának jobb megértéséhez. A persány-hegységi xenolitra kapott geofizikai eredmények (szeizmikus hullámterjedési sebesség, fajlagos vezetőképesség) és effektív viszkozitás nagy hasonlóságot mutat a Stájer-medence xenolitjaival, ami a két terület hasonló geodinamikai helyzetének köszönhető. A Nógrád-Gömör vulkáni terület xenolitjai eltérő jellemvonásokat mutatnak.

Amfibol-gazdag harzburgit xenolit fluidumzárvány vizsgálata a Stájer-medencéből

A Stájer-medence a Kárpát-Pannon régió nyugati szélén helyezkedik el, a Pannon-medence és a Keleti-Alpok közötti átmeneti zónában. A Stájer-medencében plio-pleisztocén alkáli bazaltok mintázták meg a medence alatti litoszféraköpenyt. A köpeny eredetű xenolitok közül ritkaságnak számító, modális metaszomatózison átesett, flogopit- és apatit-tartalmú amfibol-gazdag peridotitok is előkerültek. Jelen munkában egy ilyen, gazdagodott xenolit komplex fluidumzárvány vizsgálatát mutatjuk be. Fluidumzárványokat ortopiroxénben és amfibolban azonosítottunk. Utóbbi ásványban ritkán őrződnek meg köpenyfluidumok zárványai, ezért vizsgálatuk egyedi lehetőséget nyújt a köpenyben vándorló fluidumok megismerésére. Az elsődleges és álmásodlagos zárványok összetételét petrográfiai elemzések után mikrotermometriai és Raman-mikrospektroszkópiai mérések segítségével határoztuk meg.
 Az ortopiroxének zárványainak folyadék fázisában a nagy sűrűségű (~1 g/cm3) CO2 a domináns komponens (>95 mol. %), ami mellett H2O-t (<3,5 mol. %) és N2-t (<0,2 mol. %) is kimutattunk. A fluidumzárványokban azonosított szilárd fázisok leányásványok, magnezitből és anhidritből állnak. Amfibolok zárványaiban szintén CO2 a leggyakoribb komponens (>98 mol. %), ami mellett H2O-t (<1,2 mol. %), N2-t (<0,1 mol. %) és a vízben oldott SO42--t azonosítottunk. A szilárd fázisok különböző karbonátokból (magnezit, Na-tartalmú dawsonit, nahkolit és nátrit) és szulfátokból (anhidrit, Na-tartalmú thenardit-burkeit) álló ásványegyüttest alkotnak. A klór-mentes, Na+ és SO42--tartalmú fluidösszetétel egyedinek tekinthető köpenykörülmények között. A fluidum forrása egy illó-gazdag olvadék lehetett, amelyben az amfibol (valamint alárendelten flogopit és apatit) kristályosodása során feldúsultak az illók (C-O-N-S), Na+, HCO3- és SO42-, amelyek csapdázódtak a keletkező amfibolban.

AGE AND MODE OF THE MIDDLE MIOCENE MARINE FLOODING OF THE PANNONIAN BASIN—CONSTRAINTS FROM CENTRAL SERBIA

The timing and mode of the marine flooding of the southern margin of the Pannonian basin in SE Europe is still a matter of debate. In central Serbia, integrated bio-magnetostratigraphic data and quantified high-resolution records are completely missing. Here, we provide paleoenvironmental and paleoecological constraints from the Slanci section located near Belgrade that has an excellent preservation of micro-fauna and flora, i.e., planktonic and benthic foraminifera and calcareous nannoplankton. We integrate their quantified records with sedimentological, natural gamma radioactivity and magnetic susceptibility logs and include the non-quantified records of mollusks, corals, and ostracods to reconstruct the regional depositional history. The section shows upper bathyal to outer shelf depositional settings and alternating nutrient bottom conditions. The shallowing upwards trend marked by increasing terrestrial input, attributes it to the early Highstand Systems Tract of the first marine third order sequence in this part of the Pannonian Basin. We infer that the marine flooding in central Serbia took place at an age of ∼ 14 Ma, slightly predating the Langhian/Serravallian boundary (13.82 Ma) and the Badenian Salinity Crisis (∼ 13.8–13.4 Ma) in the Central Paratethys. Our results support an eastwards directed, tectonically forced, flooding of the southern Pannonian Basin. This major paleoenvironmental turnover was forced by syn-rift tectonics in the Pannonian Basin system, which started in the late early Miocene in the Styrian Basin (SE Austria) and ended more than 3 Myr later in the late middle Miocene in the Morava depression (E Serbia).

Depositional constraints and diagenetic pathways controlling petrophysics of Middle Miocene shallow-water carbonate reservoirs (Leitha limestones), Central Paratethys, Austria-Hungary

Middle Miocene shallow-water limestones, the so-called Leitha limestones, comprise a widespread Middle Miocene lithological unit of the Central Paratethys Sea. It includes mainly limestones composed of corallinacean algae and other fossil debris and were deposited in shoals of various basins such as the Vienna, Eisenstadt-Sopron and Styrian basins of Austria where they form potential hydrocarbon reservoir rocks. Petrophysical parameters including porosity, permeability, density, P-wave velocity and magnetic susceptibility measurements were performed and evaluated. The sampled sites of Mannersdorf and Wöllersdorf quarries and drill-hole Bruckneudorf are located in the Vienna Basin and share the same principal limestones depositional facies that is massive, closely-packed rudstone facies. This facies has low porosities below 10%, low permeability lower than 1.2 mD except one samples at 68.5 mD, high bulk density of dry samples up to 2.64 g/cm3 and high P-wave velocity up to 6761 m/s. In Mannersdorf, a second facies type of soft porous coarse-grained rudstone shows significantly higher porosity (up to 47%), higher permeability up to 124.3 mD, lower bulk density of dry samples less than 1.8 g/cm3 and lower P-wave velocity less than 2798 m/s. This latter facies retains primary porosity and secondary porosity enhanced by dissolution. In contrast, the former facies type suffered intensive cementation, which destroyed the primary porosity, and in some cases, subsequent later dissolution and karstification enhanced secondary porosity partly.Kummer (Austria) and Fertőrákos (Hungary) quarries are located within the Eisenstadt-Sopron Basin. The well-sorted grainstone facies has high porosity up to 50%, extremely high permeability up to 31238 mD, low bulk density of dry samples less than 1.71 g/cm3 and low P-wave velocity less than 3219 m/s. The poorly-sorted massive rudstone facies recorded only in Kummer quarry is less porous (porosities range from 22 to 31%) and less permeable. The role of dissolution predominates in these limestones besides compaction and pressure solution in the massive rudstone facies. Limestones from the Rosenberg quarry of the Styrian Basin show two facies types: (1) wackestone to packstone facies with lower porosity (up to 16.4%) and lower permeability ranges from 0.16 to 0.91 mD, compared to (2) the packstone facies with higher porosity (21%) and higher permeability of 1.83 mD. The influence of diagenesis on both facies is similar, represented by early marine cementation followed by partial dissolution and finally meteoric blocky cementation.The depositional influence on petrophysics of Leitha limestones, for instance, packing, sorting and grain size represents the basis for the differences in facies types in the same locality and among various localities. This depositional influence controls the subsequent stepwise diagenetic evolution the facies. Local depositional environments and their spatial evolution play a significant role on reservoir properties such as, at Mannersdorf the two facies types are varied due to the primary depositional characteristics and hence, the diagenetic evolution. Diagenetic pathways are principally similar in the different localities and basins; however, different stages of diagenesis are recorded due to different burial and exhumation histories.

Life in the fluvial hinterland of the late Sarmatian Sea (middle Miocene): a rare terrestrial fossil site in the Styrian Basin (Austria)

AbstractThis paper describes the section and fossil content of a former gravel pit in the Eastern Styrian Basin (SE Austria), which exposes sediments of a fluvial system, ranging from within channel to overbank environments. A predominately terrestrial gastropod fauna of 15 species so far, was recovered from a palaeosol formed in a moist and vegetated, floodplain or abandoned channel. Up-section, a shallow freshwater pond/lake developed within the floodplain, settled by fishes, molluscs and ostracods. By integrating regional geological and biostratigraphical data derived from the terrestrial gastropod fauna as well as from the other recovered biota, these strata are of late middle Miocene (late Sarmatian s.str.) age. Hence, this fossil site provides a rare insight into the terrestrial habitats in the hinterland of the Sarmatian Sea and their biota, which are otherwise barely known in Central Europe.

Fluid‐Enhanced Annealing in the Subcontinental Lithospheric Mantle Beneath the Westernmost Margin of the Carpathian‐Pannonian Extensional Basin System

AbstractMantle xenoliths from the Styrian Basin Volcanic Field (Western Pannonian Basin, Austria) are mostly coarse granular amphibole‐bearing spinel lherzolites with microstructures attesting for extensive annealing. Olivine and pyroxene CPO (crystal‐preferred orientation) preserve nevertheless the record of coeval deformation during a preannealing tectonic event. Olivine shows transitional CPO symmetry from [010]‐fiber to orthogonal type. In most samples with [010]‐fiber olivine CPO symmetry, the [001] axes of the pyroxenes are also dispersed in the foliation plane. This CPO patterns are consistent with lithospheric deformation accommodated by dislocation creep in a transpressional tectonic regime. The lithospheric mantle deformed most probably during the transpressional phase after the Penninic slab breakoff in the Eastern Alps. The calculated seismic properties of the xenoliths indicate that a significant portion of shear wave splitting delay times in the Styrian Basin (0.5 s out of approximately 1.3 s) may originate in a highly annealed subcontinental lithospheric mantle. Hydroxyl content in olivine is correlated to the degree of annealing, with higher concentrations in the more annealed textures. Based on the correlation between microstructures and hydroxyl content in olivine, we propose that annealing was triggered by percolation of hydrous fluids/melts in the shallow subcontinental lithospheric mantle. A possible source of these fluids/melts is the dehydration of the subducted Penninic slab beneath the Styrian Basin. The studied xenoliths did not record the latest large‐scale geodynamic events in the region—the Miocene extension then tectonic inversion of the Pannonian Basin.

Sarmatian wetlands at the NW margin of the Pannonian Basin system (Gratkorn, Styrian Basin, Austria, late middle Miocene). Part 1. The leaf record

Sarmatian wetlands at the NW margin of the Pannonian Basin system (Gratkorn, Styrian Basin, Austria, late middle Miocene). Part 1. The leaf record