rss_2.0Austrian Journal of Earth Sciences FeedSciendo RSS Feed for Austrian Journal of Earth Sciences Journal of Earth Sciences Feed role of the proto-Alpine Cenerian Orogen in the Avalonian- Cadomian belt<abstract> <title style='display:none'>Abstract</title> <p>The proto-Alpine Cenerian orogen (Ediacaran-Ordovician) and the Cadomian orogen (Ediacaran-Cambrian), remnants of which are exposed in the central European Variscides, should be defined as two distinct and spatially separated coastal orogens within the Avalonian-Cadomian belt. The Cadomian orogen originally lay in front of the Sahara metacraton. It underwent a change from an active to a passive margin setting during the Cambrian. The Cenerian orogen, represented by intra-Alpine rocks, was located farther east near the Arabian Nubian Shield, from where it inherited a characteristic Tonian/Stenian detrital zircon signal. Subduction persisted in the Cenerian Orogen until the Ordovician. The Cadomian orogen was akin to Andean type whereas the Cenerian orogen was more akin to Alaskan type. This paper explores why the two orogens have such different characteristics and tectonic evolutions despite their probable proximity in the Avalonian-Cadomian belt. One explanation could be that they were at nearly right-angles to each other due to a strong concave bending of the northern Gondwana margin ahead of the Arabian-Nubian Shield.</p> </abstract>ARTICLEtrue geochemistry and petrography of Miocene ombrotrophic coals in the tropical Asem-Asem Basin (Kalimantan, Indonesia): Comparison to coeval subtropical coals in the Eastern Alps<abstract> <title style='display:none'>Abstract</title> <p>The middle Miocene Warukin Formation in the Asem-Asem Basin (Kalimantan) contains a 20-m-thick coal seam (BL1) that is mined at the Jumbang mine. The seam, formed in a tropical peat, was studied to reconstruct the peat-forming environment and to compare its characteristics with those of similarly aged tropical coals from the Tutupan mine in the Barito Basin (Kalimantan) and similarly aged (<sup>~</sup>15 Ma) subtropical coal from the Leoben Basin in the Eastern Alps (Austria). Although all coals were formed in ombrotrophic peatlands, the comparison reveals differences in biomarker and maceral composition due to the different climate and flora.</p> <p>The study is based on 22 coal and three non–coal samples, each representing a stratigraphic interval of 0.2 to 1.0 m. The samples were analyzed for ash yield, carbon and sulphur contents, and maceral composition. Organic geochemical parameters were obtained on eight coal samples to obtain information on the peat-forming vegetation. The low-ash, low-sulphur BL1 seam was deposited in an ombrotrophic basinal (coastal) mire. Locally increased sulphur contents in the lower coal bench BL1L demonstrate brackish influence and a near-shore environment. The vegetation was dominated by angiosperms including abundant dammar resin producing <italic>Dipterocarpaceae</italic>, while the contribution of gymnosperms was negligible.</p> <p>The Tutupan seams T110 and T210, which were formed in kerapah (inland) ombrotrophic mires, have similar ash yields and sulphur contents but contain higher, although still low, concentrations of gymnosperm-derived diterpenoids. In addition, lower amounts of cadinane-type biomarkers and resinite suggest that <italic>Dipterocarpaceae</italic> were less dominant in kerapah peats. While differences between tropical coals from Kalimantan are minor, major differences exist between the tropical coals and the subtropical ombrotrophic Leoben coal. These include significantly higher concentrations of gymnosperm-derived biomarkers in subtropical peat, lower amounts of resinite due to the absence of <italic>Dipterocarpaceae</italic>, as wells as lower amounts of leaf- and rootlet-derived macerals. Apparently, fungal activity was also reduced in the sub-tropical Leoben peat. Surprisingly, the average amount of oxidized plant remains is also lower in the subtropical peat.</p> </abstract>ARTICLEtrue remote sensing prospection of Miocene limestone quarries in the hinterland of Roman Carnuntum and Vindobona (Vienna Basin, Austria)<abstract> <title style='display:none'>Abstract</title> <p>We have documented quarries in Miocene limestone in the Vienna Basin (Austria), Hundsheim Mountains, Leitha Mountains and Rust Hills in high-resolution airborne laser scanning data and orthophotos aiming for a diachronic quarry inventory since the Roman period. The study region was divided into 6 quarry regions and the quarries of the whole study area as well as each separate region were analyzed concerning different rock types, mean, minimum and maximum quarry area and development in the different maps. Age information have been sought from historical maps, historical photography and paintings as well as quarry face graffiti. In total, 658 quarries, possible quarries and shallow quarries have been outlined in the detailed digital terrain models, which were compared with 453 quarries indicated in four generations of historical maps between the years 1754 to 1872. The numbers of quarries are generally low in the Walter map (1754–1756), the First Military Survey (1773–1785) and Second Military Survey (1809–1846) but increase tremendously in the maps of the Third Military Survey (1872–1873).</p> <p>Most old quarries were quarried also in subsequent periods, commonly destroying virtually all pre-existing traces. According to our results two types of quarries represent highly interesting targets for more detailed studies in the search for Roman quarries: (i) areas in historical maps with suspicious uneven terrain, which have never been outlined as quarries and areas that have been mapped as “old quarries” – especially in the Third Military Survey; examples represent areas northwest and west of Pfaffenberg in Bad Deutsch-Altenburg (Lower Austria), “<italic>Gruibert</italic>” in Winden am See (Burgenland) and “<italic>Hoher Berg</italic>” in Stotzing (Burgenland); (ii) Shallow quarries, which neither appear in historical maps nor in the mining archive of the Geological Survey of Austria like the one from the saddle between Pfaffenberg and Hundsheimer Berg.</p> </abstract>ARTICLEtrue orogen – young topography: Evidence for relief rejuvenation in the Bohemian Massif<abstract> <title style='display:none'>Abstract</title> <p>The Bohemian Massif is the relic of a major Paleozoic mountain range that is known to have exhumed and its surface levelled in the Permian, but its Neogene landscape evolution is largely unconstrained. The landscape is characterized by rolling hills and extended planation surfaces above an elevation of about 500 m. However, at lower elevations deeply incised gorges confined by steep hillslopes are abundant and contrast impressively with the low relief landscapes above. Rivers with a bimodal morphology (i.e. steep at lower elevations and gentle at higher elevations) drain either to the north into the Vltava (Moldau) River or to the south into the Danube River. Hence, a continental drainage divide runs through the Bohemian Massif. Here, we quantify spatial characteristics of the Bohemian Massif landforms by computing landscape metrics like steepness index or geophysical relief derived from digital elevation models. From this we infer temporal change of the landscape in the past and predict them for the future evolution of the region.</p> <p>We show that the landscape is characterized by out-of-equilibrium river profiles with knickpoints abundantly at elevations between 450 m and 550 m separating steep channel segments at lower elevations from less steep channels at higher elevations. Hypsometric maxima at or close above knickpoint elevations, along with high and low values in geophysical relief as indicator for the degree of fluvial landscape dissection downstream and upstream of major knickpoints, support the idea of landscape bimodality. Furthermore, we find a distinct drainage divide asymmetry, which causes the reorganization of the drainage network of the region. Across-divide gradients in channel steepness predict the northward migration of the Danube-Vltava drainage divide including growth and shrinkage of tributary catchments, thus controlling changes in the Central European drainage pattern.</p> <p>All aspects suggest that the region experienced relief rejuvenation during the last few million years. We suggest that this relief rejuvenation is related to the inversion of the Molasse basin with a long wavelength rock uplift pattern and low uplift rates. Vertical motion of crustal blocks at discrete faults may locally affect the uplift pattern. However, the contrasting bedrock properties between the sedimentary cover (Molasse sediments) and the crystalline basement (Bohemian Massif) cause substantial differences in erosion rate and are thus the superior control on the topographic variations of the entire region.</p> </abstract>ARTICLEtrue temporal evolution of seismicity and variability of b-values along the Vienna Basin Transfer Fault System<abstract> <title style='display:none'>Abstract</title> <p>The Vienna Basin Transfer Fault System (VBTFS) is the most active fault system in the region between the Eastern Alps, the western Carpathians and the Pannonian Basin. The spatial and temporal distribution of earthquakes along the fault system shows a heterogeneous pattern including a long-time decay of seismicity at the northern part of the VBTFS, which was interpreted to result from a long aftershock sequence subsequent to the 1906 Dobrá Voda earthquake (M=5.7). In this paper we investigate if other segments of the VBTFS display similar long-term declines of seismicity that might indicate long aftershock sequences following strong, yet unrecorded, earthquakes in historical times.</p> <p>In order to analyse the distribution of seismicity, the VBTFS is divided into arbitrary segments of about 50 km length each. The segments are chosen to overlap each other to avoid missing information from neighbouring segments due to arbitrarily selected segment boundaries. For each segment we analyse the temporal evolution of seismicity and calculate the parameters of the corresponding Gutenberg-Richter (GR) relation.</p> <p>The temporal seismicity patterns revealed from the segments covering the Dobrá Voda area confirm the protracted aftershock sequence following the 1906 earthquake. All but one of the other segments do not show temporal changes of seismicity comparable to the long-term Dobrá Voda aftershock sequence. Seismicity patterns, however, include short-term Omori-type aftershocks following moderate earthquakes such as the 2000 Ebreichsdorf earthquake (M=4.8). The segment covering the SW tip of the VBTFS revealed a 200 years long gradual decrease of the largest observed magnitudes starting with the 1794 Leoben (M=4.7) earthquake. The 1794 event is the oldest earthquake listed in the catalogue for the region under consideration. It therefore remains open if the recorded decay of seismicity results from the 1794 event, or a stronger earthquake before that time. The latter is corroborated by the low magnitude of the 1794 earthquake which would typically not be considered to cause long aftershock sequences.</p> <p>GR a- and b-values, calculated for the individual segments, vary significantly along the VBTFS. Values range from 0.47 to 0.86 (b-values) and 0.81 to 2.54 (a-values), respectively. Data show a significant positive correlation of a- and b-values and a coincidence of the lowest b-values with fault segments with large seismic slip deficits and very low seismicity in the last approximately 300 years. These parts of the VBTFS were previously interpreted as “locked” fault segments, which have a significant potential to release future strong earthquakes, in spite of the fact that historical and instrumentally recorded seismicity is very low. We find this interpretation corroborated by the low b-values that suggest high differential stresses for these fault segments.</p> </abstract>ARTICLEtrue of alpine lakes in the Northern Calcareous Alps: a comparative study on the role of groundwater in Filblingsee and Eibensee<abstract> <title style='display:none'>Abstract</title> <p>In the Northern Calcareous Alps (NCA) there are countless small lakes with small orographic catchments that are often located only slightly below the respective summit regions. On the one hand, the lakes are located in karstable aquifers and their existence is likely to be related to karstification. Then, they are expected to be directly connected to the karst water body. These lakes are classified as karst lakes. On the other hand, the alpine environment is also influenced by glacial processes and lakes might be related to glacial erosion and deposition. For these glacial lakes, the share of groundwater inflow and outflow is regarded as subordinate even within high permeable karst lithologies. Here we compare two alpine lakes of potentially different origin in the NCA in Salzburg with the aim to provide a basis for an aerial survey of the numerous small alpine lakes in the NCA region and their characterization using the guiding parameters elaborated here. We consider (a) the lake geometry, (b) potential inflow and outflow systems, and (c) physicochemical parameters and hydrochemistry of the Filblingsee and the Eibensee, both located in the Fuschlsee region. Filblingsee was initially considered as a typical karst lake and Eibensee as a moraine-dammed glacial lake. Some clear differences arise in lake geometry, which in the karst lake shows a nearly round surface and concentric depth profile, while the glacial lake is elongated in the direction of glacier flow and has the deepest areas just upstream of the moraine dam. Both lakes show very little to no surficial inflow. Inflow and outflow occur in groundwater in both cases but are not directly tied to a highly permeable karst system. The depth profiles of the field parameters of the two lakes differ only slightly and show a dominant groundwater inflow in mid-depth regions but no flow through at the lake bottom. Water chemistry in both lakes and their potential outflows correspond to the respective aquifer in terms of solution load. Filblingsee can be characterized as a hanging lake in a secondarily sealed doline, Eibensee lies in a glacially excavated depression sealed by glacial sediments. While the inflow and outflow conditions and the hydrochemistry of both lakes are very similar, the lake geometry is a clear distinguishing feature that can be attributed to the different genesis of the two lakes. This can therefore be used as a guiding parameter for the classification of the numerous small alpine lakes in the NCA.</p> </abstract>ARTICLEtrue detachment mechanism of the rockslide causing the Chamoli February 7, 2021 debris flow disaster<abstract> <title style='display:none'>Abstract</title> <p>On February 7<sup>th</sup>, 2021, a rockslide of about 20 Mio m³ detached in a height of 5600 m asl. from the northern flank of Mount Ronti (Chamoli district, Uttarakhand state, India), turned into a rock mass fall and produced a debris flow. When the rock mass hit the Ronti Gad valley after a fall height of 1800 m the rock mass mixed with melting dead ice together with snow and ice avalanche material of previous debris flows. The debris flow destroyed hydroelectric infrastructure between 10 - 20 km down the valley killing 204 people either working at or visiting the power plants. By combining remote sensing, structural geology and kinematics/mechanical analysis of the rockslide, we demonstrate that a 600 m wide and almost 800 m long block of quartzite, bordered laterally by two joints and a newly formed tension crack on the top detached from an underlying layer of biotite-rich paragneisses. Assuming full hydrostatic heads in both joints and in the tension crack as well as 75% of the full hydrostatic head in the lower boundary surface between quartzites and paragneisses, the rock block analysis yields a friction angle of 32° for both joints, which is a plausible value of the friction angle of joints in quartzites. The detachment of the block has been the result of the widening of the tension crack on top, of a progressive propagation of the lateral joints together with a catastrophic failure of the detachment plane at the border between quartzites and paragneisses. At the time of the failure, all discontinuities must have been almost completely filled with water raising the question, if the frequency of rockslides in the Himalayas is increasing as temperatures rise and permafrost is thawing due to climate change.</p> </abstract>ARTICLEtrue of the Dachstein Limestone in the Dachstein thrust sheet (Eastern Alps, Austria)<abstract> <title style='display:none'>Abstract</title> <p>Deformation affecting the Upper Triassic Dachstein Limestone has been analyzed in the Dachstein thrust sheet, the uppermost thrust unit of the central Northern Calcareous Alps (Eastern Alps). Different scales of deformation are discussed, from kilometer-scale thrusting down to folds in the order of tens of meters to meters. Observations are based on both conventional outcrop observations and on digital fieldwork performed on drone-captured virtual outcrops and on GoogleMaps 3D terrain renderizations. The structures observed were formed at different times and document the following events: 1) Late Triassic syn-depositional instability and slumping; 2) Late Triassic syn-depositional growth of the Hallstatt diapir; 3) Late Triassic syn-depositional, salt-driven, extensional faulting; 4) Jurassic-age re-activation of extensional faults; 5) (presumably) Early Cretaceous shortening in both east-west and north-south directions; and 6) (presumably) Late Cretaceous extensional re-activation of faults. The structures and their origin have a bearing on the interpretation of the tectonic evolution of the Dachstein thrust sheet, highlighting the potential relevance of salt tectonics in controlling its structure.</p> </abstract>ARTICLEtrue tourmaline and its petrogenetic significance from the Maramureș Mountains (East Carpathians, Romania)<abstract> <title style='display:none'>Abstract</title> <p>This study describes mineralogical and crystallochemical characteristics of metamorphic tourmalines from an Alpine shear zone in a Variscan metamorphic rock sequence from the Maramures region in the northern part of the East Carpathians. We use this mineral to unravel aspects of the evolution of the tourmaline bearing host rocks and compare the crystallo-chemical characteristics to other tourmalines from Alps. Petrographic and microstructural observations, as well as electron microprobe analyses on several zoned tourmalines and associated minerals (mica, feldspar) from mylonitic schist of the Rebra terrane (Maramureș Mountains), indicate that the pre-kinematic tourmalines belong to the alkali group (Na dominant), hydroxyl dominated on the crystallographic W-site and can be assigned to the species dravite and schorl. The tourmaline-bearing rocks have a metasedimentary protolith. The analysed porphyroblasts, rotated by simple shear, show corroded rim that are interpreted to have formed due to pressure release. Three main compositional zones were evidenced on a tourmaline porphyroblast: a core zone and two asymmetrically arranged inclusion-poor/free rims, all formed in pre-alpine prograde metamorphic conditions. Based on mineral microstructural relations and geothermobarometry (tourmaline–muscovite, tourmaline–plagioclase geothermometry and phengite geobarometry), the metamorphic peak conditions of the investigated Rebra terrane were evaluated to have been at a temperature of ca. 590 to 620 ± 22 °C and P<sub>min</sub> = 5.5 - 6.0 ± 0.5 kbar. By observing dynamically recrystallized microstructures in quartz and feldspar in the shear zone a temperature of 350 - 400 °C was estimated and the quartz paleopiezometry outlined a differential stress of about 1.5 kbar that implied only minor chemical change in tourmaline outer zone.</p> </abstract>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue 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>ARTICLEtrue