rss_2.0Austrian Journal of Earth Sciences FeedSciendo RSS Feed for Austrian Journal of Earth Sciences Journal of Earth Sciences 's Cover regional scale Cretaceous transform fault zone at the northern Austroalpine margin: Geology of the western Ammergau Alps, Bavaria<abstract> <title style='display:none'>Abstract</title> <p>We reinvestigated parts of the northern Austroalpine margin and provided structural and kinematic field data in order to interpret the kinematic relationship between the Cenoman-Randschuppe (CRS) marginal slice, Falkensteinzug (FSZ), Tannheim- and Karwendel thrust sheets occurring in a narrow strip at the northern front of the northwestern Northern Calcareous Alps (NCA). As a consequence, we propose a revised model for the tectonic evolution of the northern Austroalpine margin. As thrusting propagates from SSE to NNW (Cretaceous orogeny), the Karwendel thrust sheet (including its frontal part, the FSZ) was emplaced onto the Tannheim thrust sheet in the Albian, deduced from (i) upper-footwall deposits, the youngest sediments below the Karwendel thrust (Tannheim- and Losenstein Fms.), and (ii) thrust-sheet-top deposits unconformably overlying the deeply eroded northern Karwendel thrust sheet (Branderfleck Fm.). The future CRS marginal slice was, at that time, part of the foreland of this Early Cretaceous Alpine orogenic wedge. Pervasive overprint by sinistral shear within the CRS marginal slice and northern Tannheim thrust sheet suggests sinistral W-E striking transform faults cutting across this foreland, decoupling CRS marginal slice and FSZ from the main body of the NCA and enabling an independent evolution of the CRS marginal slice from the Early Cretaceous onwards. Subsequent Late Cretaceous and younger shortening leads to successive incorporation of Arosa zone, Rhenodanubian Flysch (RDF) and Helvetic units into the Alpine nappe stack; the Tannheim thrust representing the basal thrust of the NCA. Growth strata within thrust-sheet-top deposits (Branderfleck-Fm.) give evidence for refolding of thrust sheet boundaries. In a typical thin-skinned fold-and-thrust belt, deformation should cease towards the thrust front, whereas within the NCA it increases. An Austroalpine thrust front controlled by E-trending transform faults could cause an increase in deformation towards the most external NCA and explain the absence of the Arosa zone between Allgäu and Vienna. Such faults would most probably also cut out Lower Austroalpine units. Therefore, RDF and CRS marginal slice are juxtaposed; the latter found in the tectonic position of the Arosa zone. The presence of transform faults underlines the strong imprint of the opening of the North Atlantic Ocean on the depositional setting and tectonic evolution of the NCA.</p> </abstract>ARTICLE2022-07-28T00:00:00.000+00:00The Rigelj Formation, a new lithostratigraphic unit of the Lower Permian in the Karavanke Mountains (Slovenia/Austria)<abstract> <title style='display:none'>Abstract</title> <p>The Rigelj Formation is a new lithostratigraphic unit of the Lower Permian Rattendorf Group in the Karavanke Mountains. The Formation is up to 105 m thick and mainly composed of siliciclastic and fossiliferous carbonate sediments that are entirely of shallow-marine setting. Conglomerates are interpreted as shoreface deposits, sandstones as deposits of the upper to lower shoreface, and fossiliferous siltstones as offshore deposits. Fossiliferous limestones were deposited in a shallow, open-marine shelf environment of moderate to low energy (wackestone, floatstone) and strong water turbulence (packstone, rudstone). The siliciclastic and carbonate lithotypes form some well-developed backstepping cycles starting with conglomerates, overlain by sandstones, siltstones and fossiliferous limestones that formed in an open shelf environment without siliciclastic influx. Similar sedimentary cycles are developed in the Grenzland Formation of the Carnic Alps.</p> <p>The fusulinid fauna indicates that the Rigelj Formation ranges in age from the late Asselian to the middle Sakmarian. In the western Karavanke Mountains and near Trögern, the Lower Permian lithostratigraphic succession is very similar to the succession in the Carnic Alps with Tarvis Breccia resting on the Trogkofel Limestone and the Goggau Limestone. Unlike this, in the central part of the Karavanke Mountains (Dovžanova Soteska–Mt. Pleschiwetz/Plešivec area) the Rigelj Formation is erosively overlain by the Tarvis Breccia. The stronger diversification of the sedimentary environments within the Karavanke-Carnic Alps in the Lower Permian after the uniform sedimentation in the Upper Carboniferous can be attributed to block-faulting.</p> </abstract>ARTICLE2022-07-07T00:00:00.000+00:00Stratigraphic architecture of a mixed clastic-carbonate succession and Sr/Sr-based chronostratigraphy along the margin of a synorogenic extensional basin (Hochmoos Formation, upper Santonian, Northern Calcareous Alps)<abstract> <title style='display:none'>Abstract</title> <p>The Gosau Group (Turonian to Ypresian) of the Eastern Alps is a synorogenic wedge-top succession that accumulated in active depocenters in an oblique-convergent plate tectonic setting. Due to high morphological differentiation of depocenters by tectonism, the Gosau Group displays a wide range of facies as well as marked facies heteropy and thickness variations over short lateral distances. In the area of the locations Gosau and Russbach, the Hochmoos Formation along the SE basin margin near Gosauschmied comprises coastal to shallow-marine deposits and small rudist bioconstructions and was investigated by way of field mapping, profile descriptions, microfacies analysis, isotope measurements and assessment of fossil content.</p> <p>Strontium isotope ratios (<sup>87</sup>Sr/<sup>86</sup>Sr) from 0.707485 (oldest) to 0.707549 (youngest) indicate a latest Santonian age, with the youngest parts of the Hochmoos Formation possibly extending into the Campanian. On the west side of the study area, the succession of lithologies and fossil content record transgression of a fan-delta to marginal-marine environment (lowstand to transgressive systems tract), followed by shallow neritic deposition (part of the transgressive systems tract) and, finally, by progradational stacking of limestone beds in the highstand systems tract, culminating in growth of rudist thickets in an inner shelf and partially protected ‘lagoonal’ milieu. Eventually, at the inception of the following falling stage systems tract, input of large clasts of Dachstein Limestone, quartz and chert record a recurrence of the subaqueous part of a fan-delta. On the east side of the study area, a preponderance of rudist-clastic limestones over a few rudist biostromes preserved <italic>in situ</italic> indicate a normal-marine environment punctuated by high-energy events, such as storms or tsunami. The scarcity of benthic foraminifera and the presence of only isolated specimens of colonial corals underscore a habitat with a calcarenitic substrate frequently shifted by currents. Several lines of evidence indicate that the western part of the study area was more proximal relative to the eastern one. With a maximum thickness of 68 m, the Hochmoos Formation at Gosauschmied is slightly thicker and more distal than outcrops located nearer to the basin margin and farther towards the SE (Schmiedsippl, Katzhofgraben), but significantly thinner than the nearly 300 m at Gosau Pass-Gschütt, or the thickness of 170 m observed in the area of Rigaus-Abtenau farther in the West. These thickness variations are interpreted as a result of extensional syndepositional tectonism. At Gosauschmied, the vertical arrangement of facies records a cycle of relative sea-level change that may have been tectonically enhanced.</p> </abstract>ARTICLE2022-06-21T00:00:00.000+00:00From shallow into deep sea: Sedimentary facies and U-Pb zircon ages in the early Paleozoic Noric Group at Veitsch (Eastern Greywacke Zone, Austria)<abstract> <title style='display:none'>Abstract</title> <p>The low-grade metamorphic early Paleozoic basement of the Veitsch area presents a wide variety of sedimentary facies domains. The first domain consists of thick metadacites of Middle Ordovician age (Blasseneck Porphyroid), overlain by fine-grained metaclastics of the Rad Formation (Late Ordovician to Silurian) and Devonian limestones and calcitic marbles (Kaiserstein and Kaskögerl Formation, respectively). Rhyolitic to dacitic magmatism initiated at ca. 479 Ma (LAMC-ICP-MS U-Pb zircon data) and lasted until ca. 444 Ma. The second domain comprises metaclastics of the Stocker Formation (Early Ordovician to Silurian), characterized by thin volcanics and volcaniclastics of andesitic and rhyolitic composition. U-Pb zircon data give Middle Ordovician age (463 Ma – 468 Ma). The third domain, exposed northwest of Veitsch, consists of thick metadacites (Blasseneck Porphyroid, ca. 478 Ma), followed by (siliceous) phyllites which grade into turbiditic metasediments (Sommerauer Formation, Late Ordovician to Devonian?). Clastic sediments of the Stocker and Sommerauer Formations were sourced from northern Gondwana showing a prominent Pan-African detrital zircon peak at ca. 640 Ma. Middle to Upper Ordovician volcanics (ca. 462 Ma – 448 Ma) represent the second source. Tectonic reconstruction leads us to the arrangement of three facies domains. A shallow marine shelf facies is located in the present days southwest. A marginal basin with volcanic islands on a sloping continent, and a deep-water environment containing turbidites are situated further to the northwest. The present arrangement of these facies domains is explained by eo-Alpine and Variscan thrust tectonics.</p> </abstract>ARTICLE2022-03-12T00:00:00.000+00:00Petrological and geochronological investigations on the individual nappes of the Meran-Mauls nappe stack (Austroalpine unit/South Tyrol, Italy)<abstract> <title style='display:none'>Abstract</title> <p>The Meran-Mauls nappe stack is part of the Austroalpine unit in South Tyrol (Italy). There it holds a special position directly in front of the Southalpine Dolomites indenter and west of the Tauern Window. It is situated in the hanging wall of the Southalpine unit, above a NW dipping segment of the Periadriatic fault system, namely the Meran-Mauls fault. Also all other sides are defined by Oligocene-Miocene strike-slip and normal faults. Based on recent mapping the Meran-Mauls nappe stack consists of three nappes separated by NW to NNW dipping shear zones. The lowermost nappe in the southwest is represented by the Schenna (Scena) unit. It is overlain along the Masul shear zone by a nappe consisting of the Hirzer (Punta Cervina) unit and the Pens (Pennes) unit including Triassic (meta)sediments. Separated by the Fartleis fault the St. Leonhard (San Leonardo) unit forms the uppermost nappe. The aim of this study is to describe the individual units and the separating structural elements more properly, based on new structural, petrological, geothermobarometric and geochronological data and to compare these units to other Austroalpine elements in the vicinity. Sillimanite-bearing paragneiss, minor amphibolite and quartzite as well as a distinct marble layer close to its base characterise the Schenna unit. Further, it contains pegmatite dikes, presumably Permian in age. Amphibolite-facies P-T conditions of c. 0.55 ± 0.15 GPa and 600 ± 100°C are thus correlated with a Permian metamorphic imprint. The Masul shear zone mostly consists of mylonitic paragneiss of the Hirzer unit. It is pre-Alpine in age and probably formed during the Jurassic. For the paragneiss of the Hirzer unit upper greenschist- to amphibolite-facies metamorphic conditions of 0.4-0.50 ± 0.15 GPa and 550 ± 70°C are attributed to the Variscan tectonometamorphic imprint. The whole Pens unit represents a shear zone. Due to the occurrence of Permotriassic (meta)-sediments within this shear zone, it is an Alpine structure, as well as the bordering Fartleis fault. Rb/Sr biotite ages yield sometimes partly reset pre-Alpine age values in the whole Meran-Mauls nappe stack, indicating a pervasive anchizonal to lowermost greenschist-facies metamorphic overprint during the Eoalpine tectonometamorphic event. Tectonostratigraphically the Meran-Mauls nappe stack can be attributed to the Drauzug-Gurktal nappe system. The latter forms the uppermost structural element of the Austroalpine nappe stack and thus only shows a weak Eoalpine metamorphic overprint. With respect to its special lithologic composition the Schenna unit can be correlated with the Tonale unit in the southwest and the Strieden-Komplex in the east.</p> </abstract>ARTICLE2022-02-23T00:00:00.000+00:00Cretaceous biostratigraphy and lithostratigraphy of the Glinzendorf Syncline based on well Gänserndorf UeT3 (Vienna Basin, Austria)<abstract> <title style='display:none'>Abstract</title> <p>The 2200 m thick Cretaceous units of well Gänserndorf UeT3 have been biostratigraphically analyzed based on cuttings from 3210 m to 5140 m. The deposits from the Tirolic Glinzendorf Syncline (a part of the buried Northern Calcareous Alps) can be largely correlated with the Lower Gosau Subgroup of the Grünbach Syncline. An exception is the basal unit, which has no equivalent in the Grünbach Syncline. This lower unit is subdivided into a non-marine lower and a largely marine upper part. No age constraints are available for the lower part, whereas the upper part has a possible age range from middle Turonian to Coniacian. For this unit, which is documented for the first time from the Glinzendorf Syncline, we propose Glinzendorf Formation as new lithostratigraphic term.</p> <p>The Glinzendorf Fm. is overlain by the Grünbach Fm., which is intercalated by a thick unit of conglomerates. These are interpreted as equivalents of the Dreistetten Conglomerate Mb. The calcareous nannofossils of these units suggest a latest Santonian to early Campanian age. Non-marine conditions prevailed during deposition of the Grünbach Fm., but marine incursions are indicated for parts of the Dreistetten Conglomerate Mb. The top of the Grünbach Fm. is formed by an about 50-m-thick unit of coal, rich in Characeae oogonia, which, together with the Dreistetten conglomerates serve as marker layer for correlation with the outcrops in the Grünbach Syncline. The Grünbach Fm. is overlain by marls and silty shales of the Piesting Fm. for which a late Campanian and Maastrichtian age is documented. Marine conditions predominated during this interval. The topmost unit in well Gänserndorf UeT3 is overthrusted on the Maastrichtian Piesting Fm. and represents Campanian sandstones and conglomerates of the Grünbach Fm. This Gänserndorf Thrust is detected and biostratigraphically constrained for the first time.</p> </abstract>ARTICLE2022-02-04T00:00:00.000+00:00Sinemurian biostratigraphy of the Tannscharten section near Reichraming (Lower Jurassic, Schneeberg Syncline, Northern Calcareous Alps)<abstract><title style='display:none'>Abstract</title><p> Lower Jurassic ammonites were collected from deep-water limestones of the Tannscharten section, southwest of Reichraming (Northern Calcareous Alps, Upper Austria). The outcrop provides a rich Upper Sinemurian (Lower Jurassic) ammonite fauna of the Allgäu Formation. The area is situated in the westernmost part of the Schneeberg Syncline in the north of the Reichraming Nappe (High Bajuvaric Unit). The ammonite fauna consists of seven different genera, each apparently represented by 1-2 species. Echioceratids are the most frequent components (Echioceras, Leptechioceras, Paltechioceras), followed by the phylloceratids (Juraphyllites, Partschiceras) and oxynoticeratids (Gleviceras, Paroxynoticeras). Juraphyllites libertus, Partschiceras striatocostatum, Gleviceras paniceum, Echioceras quenstedti, Echioceras raricostatoides, Paltechioceras boehmi, Leptechioceras meigeni, Leptechioceras macdonnelli and Paltechioceras oosteri are new for the Schneeberg Syncline and allow for the first time a detailed biostratigraphy of the Echioceras raricostatum zone. The assemblage is correlated with other faunae from Austria, Germany, United Kingdom, France, Switzerland and Romania. The cephalopod fauna consists of a mix of elements from the Northwest European Province and the Mediterranean Province. The detailed biostratigraphy based on ammonites is presented here.</p></abstract>ARTICLE2018-09-06T00:00:00.000+00:00Late Glacial and Holocene sedimentary infill of Lake Mondsee (Eastern Alps, Austria) and historical rockfall activity revealed by reflection seismics and sediment core analysis<abstract><title style='display:none'>Abstract</title><p> Glacigenic perialpine lakes can constitute continuous post-last glacial maximum (LGM) geological archives which allow reconstruction of both lake-specific sedimentological processes and the paleoenvironmental setting of lakes. Lake Mondsee is one among several perialpine lakes in the Salzkammergut, Upper Austria, and has been previously studied in terms of paleoclimate, paleolimnology and (paleo)ecology. However, the full extent and environment of Late Glacial to Holocene sediment deposition had remained unknown, and it was not clear whether previously studied core sections were fully representative of 3D sediment accumulation patterns. In this study, the sedimentary infill of Lake Mondsee was examined via high-resolution seismic reflection survey over a 57-km extent (3.5 kHz pinger source) and a sediment core extracted from the deepest part of the lake, with a continuous length of 13.76 m. In the northern basin, seismic penetration is strongly limited in most areas because of abundant shallow gas (causing acoustic blanking). In the deeper areas, the acoustic signal reaches depths of up to 80 ms TWT (two-way travel time), representing a postglacial sedimentary sequence of at least 60-m thickness. Holocene deposits constitute only the uppermost 11.5 m of the sedimentary succession. Postglacial seismic stratigraphy of Lake Mondsee closely resembles those of well-studied French and Swiss perialpine lakes, with our data showing that most of Lake Mondsee’s sedimentary basin infill was deposited within a short time period (between 19,000 BP and 14,500 BP) after the Traun Glacier retreated from the Mondsee area, indicating an average sedimentation rate of about 1.4 cm/yr. Compared to other perialpine lakes, the seismic data from Lake Mondsee reveal little indication of mass movement activities during the Holocene. One exception, however, is rockfalls that originate from a steep cliff, the Kienbergwand, situated on the southern shore of Lake Mondsee, where, in the adjacent part of the lake, seismic profiles show mass transport deposits (MTDs), which extend approximately 450 m from the shore and are mappable over an area of about 45,300 m<sup>2</sup>. Sediment cores targeting the MTDs show two separate rockfall events. The older event consists of clast-supported angular dolomitic gravels and sands, showing high amounts of fine fraction. The younger event exhibits dolomitic clasts of up to 1.5 cm in diameter, which is mixed within a lacustrine muddy matrix. Radiocarbon dating and correlations with varve-dated sediment cores hint at respective ages of AD 1484 ± 7 for Event 1 and AD 1639 ± 5 for Event 2. As our data show no evidence of larger-scale mass movements affecting Lake Mondsee and its surroundings, we infer that the current-day morphology of the Kienbergwand is the result of infrequent medium-scale rockfalls.</p></abstract>ARTICLE2018-09-06T00:00:00.000+00:00The Sarmatian/Pannonian boundary at the western margin of the Vienna Basin (City of Vienna, Austria)<abstract><title style='display:none'>Abstract</title><p> Sarmatian and Pannonian cores, drilled at the western margin of the Vienna Basin in the City of Vienna, reveal a complex succession of marine and lacustrine depositional environments during the middle to late Miocene transition. Two Sarmatian and two Pannonian transgressive-regressive sequences were studied in detail. Identical successions of benthic faunal assemblages and similar patterns in magnetic susceptibility logs characterise these sequences. This allows a correlation of the boreholes over a distance of ~3.5 km across one of the major marginal faults of the Vienna Basin. Biostratigraphic data, combined with rough estimates of sedimentation rates, reveal large gaps between these sequences, suggesting that only major transgressions reached this marginal area. In particular, during the Sarmatian-Pannonian transition, the basin margin completely emerged and turned into a terrestrial setting for at least 600 ka.</p></abstract>ARTICLE2018-09-06T00:00:00.000+00:00Mineralogy and facies variations of Devonian and Carboniferous shales in the Ukrainian Dniepr-Donets Basin<abstract><title style='display:none'>Abstract</title><p> The mineralogy of Devonian to Carboniferous shales from the Ukrainian Dniepr-Donets Basin (DDB) was investigated during this study. These shales show a high compositional variability in vertical and lateral directions. Furthermore, stratigraphic trends were found to be controlled both by climatic factors as well as by changing detrital input from the hinterland. High kaolinite contents and predominance of kaolinite over illite in the Tournaisian and partly in the lower Visean units are likely a result of intense chemical weathering related to the Hangenberg climatic event at the Devonian/ Tournaisian boundary. In contrast, abnormally high kaolinite contents in upper Visean and Serpukhovian samples at the basin center might be caused by different transport properties of kaolinite and illite, leading to selective concentration of small detrital kaolinite particles, which are often in the sub-micrometer range according to scanning electron microscopy observations. K/Al elemental ratios correlate well with illite/kaolinite ratios for samples in which significant amounts of both clay minerals are present, which enables a pre-evaluation of the relative kaolinite content based on bulk geochemical data. As kaolinite is suggested to decrease the fraccability of shales and to have a great influence on their wetting behaviour, this is useful information for explorational purposes. Higher feldspar contents in Devonian and Tournaisian samples, especially along the NE basin margin and in the shallow NW part of the DDB, are likely related to increased detrital input from magmatic precursors (e.g. in the Voronezh Massif ) during (and shortly after) the active rift stage of the DDB. In general, feldspar contents are higher in proximal positions compared to the basin center, which is likely a result of shorter transport distances of the comparably large feldspar grains. Finally, the presence of expandable clay minerals down to depths of 6 km and the fact that no thermal maturity trend is visible down to these depths, proves, that a low post-depositional heat flow was present in the DDB. This is in good agreement with vitrinite reflectance measurements and thermal modelling results from previous studies, which suggest a low Mesozoic heat flow.</p></abstract>ARTICLE2018-09-06T00:00:00.000+00:00Crustal geomagnetic field and secular variation by regional and global models for Austria<abstract><title style='display:none'>Abstract</title><p> Using 12-year-long series of data (2001-2012) from geomagnetic observatories and repeat stations in Austria and its neighboring countries, a regional spatial-temporal (ST) model is developed based on the polynomial expansion consisting of latitude, longitude, and time of the geomagnetic field components and total magnetic field F. Additionally, we have used three different global models (CHAOS-5, POMME-9, and EMM2015), which are built on spherical harmonics up to a maximum degree L<sub>max</sub> and give the core field and crustal field separately. The normal field provided by the ST model and its “model bias”, which comprise the residuals of the differences between measured and predicted values, are calculated and the respective maps are shown. The residuals are considered an estimate of the local crustal field. In the case of global models, we have applied for each of these three methods to calculate the “model bias”: residuals of the differences between observed values and predicted values of the model, residuals of the differences between observed values and core field values of the model, and the average bias for the period 2001-2012. The normal field of the region of Austria provided by each global model is also calculated. Generally, the regional and global models yield relatively similar crustal fields for the Austrian region, especially when the first method is used. The normal fields calculated by them are in good agreement with each other. Each of the global models directly provides the crustal field, and they are compared with the aeromagnetic data provided by aeromagnetic surveys over the Austrian region. The ST model is in better agreement with aeromagnetic data. We have also analyzed the secular variation over the region, which is calculated from the rate of change of normal field given by the ST and global models.</p></abstract>ARTICLE2018-09-06T00:00:00.000+00:00Stable isotope geochemistry and petrography of the Qorveh–Takab travertines in northwest Iran<abstract><title style='display:none'>Abstract</title><p> The Qorveh-Takab travertines, which are connected to thermal springs, are situated in the northwest of the Sanandaj- Sirjan metamorphic zone in Iran. In this study, the travertines were investigated applying petrography, mineralogy and isotope geochemistry. Oxygen and carbon isotope geochemistry, petrography, scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analysis were used to determine the source of the CO<sub>2</sub> and the lithofacies and to classify the travertines. Isotope studies, morphological and mineralogical observations and distribution of travertines revealed that the travertines of the Qorveh-Takab could be of thermal water origin and, therefore, belong to the thermogene travertine category. These travertines are usually massive with mound-type morphology and are essentially found in regions with recent volcanic or high tectonic activity. The measured δ<sup>13</sup>C values of the travertines indicate that the δ<sup>13</sup>C of the CO<sub>2</sub> released from the water during travertine deposition, while the source of the CO<sub>2</sub> in the water springs seems to have been of crustal magmatic affinity. These travertines are divided into two lithofacies: (1) crystalline crust travertine and (2) pebbly (phytoclastic travertine with pebble- size extraclasts) travertine. δ<sup>18</sup>O and δ<sup>13</sup>C values of travertines are -0.6 to -11.9 (‰VPDB) and +6.08 to +9.84 (‰VPDB), respectively. A probable reason for the heavy carbon isotope content observed in these deposits is the presence of algae microorganisms, which was verified by SEM images. Fissure ridges, fluvial crusts with oncoids, and mound morphological features are observed in the study area. Based on the petrographic and SEM criteria, Qorveh-Takab travertines are classified into four groups: (1) compacted, (2) laminated, (3) iron-rich spring deposit and (4) aragonite-bearing travertines. Stable isotope compositions of Turkish travertines are largely similar to the travertines in the study area.</p></abstract>ARTICLE2018-09-06T00:00:00.000+00:00Palynology of the Cenomanian Raha Formation, Gulf of Suez, Egypt: Biostratigraphical, palaeoenvironmental and palaeobiogeographical implications<abstract><title style='display:none'>Abstract</title><p>The current study presents a fully qualitative palynological investigation carried out on the Raha Formation encountered from three wells in the Bakr Oil Field of the Gulf of Suez, Egypt. Around 30 species of pteridophytic spores, 26 species of angiosperm pollen, 24 species of gymnosperm pollen and 27 species of dinoflagellate cysts have been recorded. However, achritarchs, microforaminiferal test linings and freshwater algae are impoverished and sparsely documented throughout the Raha Formation. Two palynozones have been identified based on some stratigraphically significant pollen and spores, arranged from youngest to oldest: (1) Palynozone I (Classopollis brasiliensis–Tricolpites sagax Assemblage Zone) of late Cenomanian age; (2) Palynozone II (Afropollis jardinus–Crybelosporites pannuceus Assemblage Zone) of early-middle Cenomanian age. The distribution and ecological affiliation of specific palynomorph species, as well as various palynofacies parameters, are interpreted. A shallow marine environment from supratidal to distal inner neritic under proximal suboxic–anoxic to dysoxic–anoxic shelf conditions is reconstructed. Palaeobiogeographically, the absence of elaters from the recovered taxa is interpreted in terms of minor floral variation. This may be attributed to climatic and/or an environment-controlled niche establishment, which possibly was shaped by the existence of a physical barrier hindering the distribution of such type of elaterate parent plants.</p></abstract>ARTICLE2018-09-06T00:00:00.000+00:00Chemical denudation rates of a small torrential catchment in the Northern Calcareous Alps<abstract><title style='display:none'>Abstract</title><p> In this study, we present chemical denudation rates derived from measuring the dissolved load of an alpine catchment located in Salzburg, Austria. The catchment has a drainage area of about 7 km<sup>2</sup> and is predominantly covered by limestone- rich glacial deposits and carbonate rocks that are characteristic of the Northern Calcareous Alps. To obtain catchment-wide chemical denudation rates, we integrated discharge time series that were measured by a permanent water gauge of the Austrian Service for Torrent and Avalanche Control to compute the total discharge of the investigated catchment over a period of one year. During the same period, samples were taken during several campaigns to consider variations of the dissolved load. Samples were collected at high and low runoff conditions to study the effect of precipitation and at different locations along the tributaries to account for lithological variations of the river beds on the dissolved load. For the investigation period of one year, 2.97 ×10<sup>6</sup> m<sup>3</sup> of discharge was measured at the catchment outlet. The summed cation-concentration varies between about 85 mg/l for dry-conditions and 75 mg/l for rainy-conditions at the gauge and consists predominantly of Ca<sup>2+</sup>and Mg<sup>2+</sup> cations. Based on the total discharge of the river integrated over a period of one year, and the average dissolved load determined from water samples, we obtained a chemical denudation rate of 0.094 mm/a. The results imply that chemical denudation is a significant driver for redistributing mass in carbonate-dominated catchments and might be the dominant erosional process in such settings.</p></abstract>ARTICLE2018-09-06T00:00:00.000+00:00Facies, palaeogeography and stratigraphy of the lower Miocene Traisen Formation and Wildendürnbach Formation (former “Oncophora Beds”) in the Molasse Zone of Lower Austria<abstract><title style='display:none'>Abstract</title><p> A detailed study of OMV wells throughout the Lower Austrian Molasse Basin demonstrates the existence of a distinct and synchronous upper Ottnangian (lower Miocene) stratigraphic signal, the Calcite Minimum Interval (CMI). It corresponds to the depositional phase of the Rzehakia Lake System. This signal is interpreted to be of chronostratigraphic importance as an expression of palaeoclimate and related sea-level change. It is represented by the brackish Traisen Formation, which crops out south of the Danube. The Traisen Formation correlates with sands and shales in OMV wells to the north, termed Wildendürnbach Formation. However, the CMI underlies a marine unit, the so-called “Oncophora Beds” (also known as Rzehakia Beds) as reported from OMV wells in the north at the border to the Czech Republic. We demonstrate that these former “Oncophora Beds” are younger, i.e. of Karpatian age, than originally assumed. Therefore, these deposits cannot be correlated to the late Ottnangian Traisen Formation. This may solve the problem of contradicting interpretations concerning the depositional environment of both units, which were correlated to each other in the past. As no Rzehakia bivalves (formerly Oncophora) are described from these former “Oncophora Beds”, we recommend to avoid using the term for these turbiditic sands. Instead, we attribute these deposits to the fully marine Karpatian Laa Formation. These new findings, which are in accordance with published data from the Czech Republic, indicate two (in time and space) independent sedimentary systems and sand deposition centres for the Traisen Formation and the massive sands attributed as “Oncophora Beds” around Wildendürnbach. A late Ottnangian system in the south delivered the material of the Traisen Formation from the Alps and a Karpatian system delivered the clastic material of the massive sands of the Laa Formation from the east.</p></abstract>ARTICLE2018-09-06T00:00:00.000+00:00The Osli Formation – a Holocene lithostratigraphic unit in the Danube/Kisalföld Basin, eastern Austria and northwestern Hungary<abstract> <title style='display:none'>Abstract</title> <p>In the course of field investigations and formalisation of Quaternary deposits in the Lake Neusiedl/Seewinkel and Hanság area the Osli Formation is designated as new formal lithostratigraphic unit. It covers an area of ~200 square kilometres and, in historic times, wetlands such as swamps and peat bogs extended from Waasen in the south-eastern Seewinkel Plain to the Hanság (Kisalföld). Due to missing stratigraphic data this formation cannot be formally divided into two members but into a lower and upper section instead. The lower section of the Osli Formation was cored in the Seewinkel Plain and consists of lacustrine deposits of up to 10 metres in thickness that were presumably deposited during Preboreal. Despite the draining of the Hanság over centuries and decades of peat mining, the upper section of the Osli Formation nowadays still consists of an at least one-meter-thick succession of peat intercalated with fluvio-lacustrine deposits. The investigated peat layers at Tétényi-Hany (~5 km north of Osli) were <sup>14</sup>C-dated, ranging in age from ~2,400 BC to 1,500 AD. <sup>14</sup>C ages of peat profiles at Osli-Tőzegbánya (Fövenyes-tó), located ~2,5 km northeast of Osli, even date back to ~4,000 BC. Hence the 10 to 12 m thick Osli Formation can be dated as Holocene. It is underlain by Quaternary deposits of the Illmitz Formation.</p> </abstract>ARTICLE2021-12-23T00:00:00.000+00:00The Haidbach deposit in the Central Tauern Window, Eastern Alps, Austria: a metamorphosed orthomagmatic Ni-Cu-Co-PGE mineralization in the Polymetallic Ore District Venediger Nappe System – Hollersbach Complex<abstract> <title style='display:none'>Abstract</title> <p>Cu-Ni-Co-PGE mineralization occurs at Haidbachgraben in the Early Palaeozoic, Subpenninic Hollersbach Complex of the Central Tauern Window, Austria. Massive sulfide ore formed from sulfide melt segregated from silicate melt during intrusion of pyroxenite into magmatic rocks formed in an MORB-type environment. Relics of magmatic minerals include chromian spinel and polyphase sulfide droplets composed of pyrrhotite, chalcopyrite and pentlandite preserved in recrystallized pyrite. Both ore and host rocks were multiply deformed and metamorphosed, leading to hornblendite carrying the ore, enveloped by chlorite-epidote schist. Conditions of – likely Variscan – amphibolite facies metamorphism are documented by relict pargasitic cores in hornblende and actinolite-tremolite, and by ternary sulfarsenide compositions in the Co-Ni-Fe solid solution series that are the most common accessory minerals found in the sulfide ore. Pyrrhotite, pentlandite, chalcopyrite and pyrite are the major sulfide minerals. Chalcopyrite is Cd-rich and retains a high-temperature magmatic signature. High Co/Sb and moderate Se/As ratios in pyrite also point to a magmatic environment of mineralization. The accessory mineral assemblage of small grain size (mostly &lt;10 µm) comprises native Au-Ag alloy and petzite as Au-Ag minerals, sperrylite, a variety of Pd tellurides and bismuthotellurides with elevated Sb, irarsite, and Re sulfides such as tarkianite and a Pb-Re sulfide. In addition, minor molybdenite, bournonite, scheelite and selenides have been identified. Two precious metal assemblages are present in individual samples: (1) hessite associated with Pd tellurides, often accompanied by sphalerite and chalcopyrite; (2) tarkianite forming euhedral inclusions in pyrite. Sperrylite and Au-Ag native alloys are present throughout and were also detected in silicate matrix. Most of the precious metal-bearing phases must have formed during recrystallization of base metal sulfides after the magmatic, and probably during later metamorphic events terminating in the Neoalpine Tauern crystallization.</p> </abstract>ARTICLE2021-01-29T00:00:00.000+00:00Microfacies and C/O-isotopes in lacustrine dolomites reflect variable environmental conditions in the Germanic Basin (Arnstadt Formation, Upper Triassic)<abstract> <title style='display:none'>Abstract</title> <p>The conditions in ancient evaporative environments conducive to authigenic carbonate (especially dolomite [CaMg(CO<sub>3</sub>)<sub>2</sub>]) formation are still insufficiently understood. Insights from microfacies analysis can help to constrain the conditions in these environments. We provide a brief overview of the microfacies association and carbon and oxygen isotope compositions of dolomite beds intercalated in a claystone-rich succession from the Norian Arnstadt Formation in Thuringia and Lower Saxony (Germany) in order to gain further insight into the depositional conditions and processes leading to the formation of authigenic Mg/Ca-carbonates in the Germanic Basin. The studied intervals are ascribed to lacustrine, partially evaporitic conditions, while the sedimentary structures were not obliterated by recrystallization. The microfacies of the dolomites is diverse, showing homogeneous micrite, mudclasts, lamination, and peloidal structures, and reflects a shallow to deeper water (below wave base) and episodically evaporative environment. The dolomites exhibit oxygen isotope values (δ<sup>18</sup>O) in the range from −5.21 to −0.36‰ VPDB and, hence, only represent a weak meteoric influence, suggesting that the authigenic carbonate generally formed under evaporative conditions. Carbon isotope values (δ<sup>13</sup>C) in the range of −4.28 to 1.39‰ VPDB indicate a small contribution of remineralized organic carbon, mainly in sediments that were presumably deposited in deeper water or under brackish conditions. Sedimentary structures, such as lamination with graded silt layers, reworked mudclasts embedded in a fine dolomicrite matrix, and peloids showing plastic deformation, indicate that the sediment was still unlithified. These observations would be consistent with an authigenic formation of Mg/Ca-carbonates directly from the lake water, and their deposition under variable conditions in a large playa-lake/perennial lake system.</p> </abstract>ARTICLE2021-12-17T00:00:00.000+00:00In search of the oldest rock of Austria: The Hauergraben Gneiss, a 1.40 Ga old mafic quartz-monzonitic inlayer in the Dobra Gneiss (Drosendorf Unit, Bohemian Massif) as a new candidate<abstract> <title style='display:none'>Abstract</title> <p>For a long time, the 1.38 Ga old Dobra Gneiss (Type A) from the Lower Austrian Drosendorf Unit (Moldanubian Zone, Bohemian Massif) was considered the oldest rock of Austria. We now have dated zircons from a local mafic inlayer in the Dobra Gneiss Type A, termed Hauergraben Gneiss. This small-scale amphibole-bearing orthogneiss has a magmatic formation age of 1.40 Ga, and is, thus, to the present state of knowledge, the oldest rock of Austria. Based on geochemical investigations, the protolith of the Hauergraben Gneiss was a quartz-monzonite. It probably originated in a volcanic arc setting like the Dobra Gneiss, but shows distinctively higher transitional metal contents (especially Cr and Co), higher Ba and Sr, and higher light rare earth element contents, which hint at a lithospheric mantle input. This 1.40 Ga old mafic arc material was then incorporated into the 1.38 Ga old intrusive protolith of the Dobra Gneiss, probably in the form of enclaves. Considering the model that the Drosendorf Unit was part of Amazonia until the late Neoproterozoic, we propose that both, Dobra Gneiss Type A and Hauergraben Gneiss, originated at the western margin of the Columbia super-continent, where several long-lived Mesoproterozoic volcanic arcs existed and accreted over time. During the Variscan orogeny, the Hauergraben Gneiss experienced peak metamorphic temperatures of ~620 °C at pressures of ~6 kbar, as can be deduced from amphibole thermobarometry. This is in line with published peak-<italic>PT</italic> estimates from other parts of the Drosendorf Unit. Formation of secondary low-Al magnesiohornblende at the expense of the earlier edenitic/pargasitic peak amphibole indicates a subsequent retrograde overprint.</p> </abstract>ARTICLE2021-04-22T00:00:00.000+00:00The Relic Landscapes of the Grazer Bergland: Revisiting the Piedmonttreppen Debate<abstract> <title style='display:none'>Abstract</title> <p>The Grazer Bergland is a mountainous region at the eastern end of the Alps that escaped glacial erosion in the Pleistocene and thus preserves low-relief landforms that are relics of the earlier uplift history. These relic landforms may reflect a Piedmonttreppe that formed during a series of stages of a wide-reaching Pliocene uplift event that interacts with the landscape evolution, but this model is not uniquely accepted for the region. In order to test this model and for a future better correlation of the paleosurfaces with those mapped in other regions, it is important to benchmark these relic landforms. We do so by presenting a geomorphic map of the Bergland region over some 600 km2. We describe the well-known levels Stadelberg/Zahrerberg- (at 540 – 700 m a.s.l.), Kalkleiten/Hochstraden- (at 700 – 850 m a.s.l.), Trahütten- (at 950 – 1100 m a.s.l.), Hubenhalt- (at 1200 m a.s.l.), as well as Wolschenegg- and Kor- (at 1200-1720 m a.s.l.) levels and correlate their distribution in space and time. Fluvial channels between segments of the relic surfaces have knickpoints that correlate with the planation surfaces, which is in strong support of the Piedmonttreppe model. Our analysis results in a model that interprets the course of the Mur river to be the product of a river piracy event near Peggau at the time of the planation of the Trahütten level (about 4 Ma), diverting the paleo-Mur from an eastwards course along the Mürz valley in direction Vienna, towards Graz. Thereafter, the Mur remained antecedent with respect to the uplift of the surrounding massifs resulting in massive base level drop for many tributaries, like the Mixnitzbach or Rötschbach. The resulting knickpoints have since migrated upstream to cause successive minor river capture events, for example the Rötschbach capture at Kesselfall. We also show that the presence of lower levels in the Passail Basin is best interpreted in terms of the more efficient erosion of basin sediments that filled a Miocene half graben north of the Schöckl ridge and analyze the two major drainages of the region, the Raab and the Weizbach.</p> </abstract>ARTICLE2021-09-25T00:00:00.000+00:00en-us-1