<abstract xmlns="http://www.w3.org/1999/xhtml">In order to constrain tectonic models for the nature of the Eoalpine high pressure belt at the eastern end of the Alps, we investigate the formation pressure of metamorphic rocks along a profile between the Koralpe and the well-known UHP rocks of the southern Pohorje mountains. Rocks from three different regions are considered: (i) the rocks of the southernmost Koralpe to the north, (ii) the rocks of the Plankogel Unit between the Plankogel detachment and the Drava valley and (iii) the rocks between the Possruck range and the southern Pohorje mountains. In the Koralpe, pelitic rocks record a formation pressure around 15 – 18 kbar, as reported in the literature. For the Plankogel Unit, we derive pressures between 7.1 ± 1.95 kbar and 11.5 ± 3.42 kbar at 650 °C and recognize only a single Eoalpine metamorphic event. For the high grade rocks of the Pohorje mountains, we derive peak metamorphic pressures (explored with the garnet-muscovite-kyanite-quartz assemblage) that rise from 16.2 ± 3.45 kbar (at 700°C) in the north, to 23.9 ± 2.49 kbar (at 700 °C) in the south. There, we also recognize a later lower pressure event that is derived from pressure calculations with the full equilibrium assemblage. This lower pressure event yields similar conditions around 10 ± 2 kbar at 650 °C for the entire north-south transect within the Pohorje mountains. Peak metamorphic conditions in the Koralpe and Pohorje regions are matched by a continuous field gradient of about 1.3 kbar per 10 kilometers distance corresponding to a depth increase of about 0.5 km per kilometers distance assuming lithostatic conditions. We suggest that this supports that the two units may be interpreted together in terms of a 45° dipping subducting plate. Above this subducting plate, it is inferred that a slab was extracted that was located between the Plankogel Unit and the high pressure rocks, causing a first exhumation stage that is associated with buoyant upwards tilting of the subducted slab to mid crustal levels. Within this model, the Plankogel Unit was located in the hanging wall of the extracted slab and the Plankogel detachment forms the suture of the extracted slab. Exhumation from mid crustal levels to the surface during a 2nd stage occurred due to erosion and normal faulting. This normal faulting is responsible for some 10 km of upward displacement of the Pohorje mountains relative to the Koralpe and ultimately for the current distribution of lithologies on a map scale.</abstract>

Tectonic interpretation of the metamorphic field gradient south of the Koralpe in the Eastern Alps

<abstract xmlns="http://www.w3.org/1999/xhtml">The NW–trending Three Pagodas shear zone exposes a high–grade metamorphic complex named Thabsila gneiss in the Kanchanaburi region, western Thailand. The quartz mylonites within this strike–slip zone were selected for strain analysis. 2–dimensional strain analysis indicates that the averaged strain ratio (Rs) for the lower greenschist facies increment of XZ– plane is Rs = 1.60–1.97 by using the Fry’s method. Kinematic vorticity analysis of the quartz mylonites in the shear zone showed that the mean kinematic vorticity number of this increment is Wk = 0.75–0.99 with an average at 0.90 ±0.07. The results implied that the quartz mylonites within the Three Pagodas shear zone have a dominant simple shear component of about 72% with a small pure shear component. A sinistral shear sense is indicated by kinematic indicators from macro– to micro–scale. We conclude that the Three Pagodas shear zone deformed in the process of sinstral shear–dominated transpression, which is similar to the Mae Ping shear zone in the north.</abstract>

Department of Geology, Faculty of Science

Department of Geodynamics and Sedimentology

Department of Earth Sciences, Faculty of Science

Quantitative finite strain analysis of the quartz mylonites within the Three Pagodas shear zone, western Thailand

<abstract xmlns="http://www.w3.org/1999/xhtml">In intramontane landscapes shaped by glacial-interglacial cycles, the most rapid changes during the proglacial/paraglacial phases may be amplified by catastrophic mass-wasting. Herein, we describe the Last Glacial Maximum (LGM) to Holocene development of a catchment in the Northern Calcareous Alps wherein intense proglacial/paraglacial sedimentation and descend of a rock avalanche persistently modified drainage and sediment dispersal.During buildup of the LGM, the pre-last glacial Strassberg valley – the trunk valley of this study – was filled with a proglacial fluvio-lacustrine succession. Thereafter, the area became largely buried under the Inn ice stream. During deglacial ice melt, copious sediment was shed from glacially-conditioned mountain flanks. Alluvial fans cut off from their former supply area, and perched in isolated position, result from presumed sediment dispersal across dead ice. Shortly after deglaciation, a ~11 Mm3 rock avalanche detached from a high cliff, overran an opposing mountain ridge, and spread over a lower-positioned plateau. The rock avalanche blocked the Strassberg valley and set the base-level to an intramontane basin that persists until present. A quartz OSL age from a loess drape above the rock-avalanche deposit dates mass wasting prior to 18.77 ± 1.55 ka; so far, this is the oldest age-bracketed post-LGM catastrophic mass-wasting of the Eastern Alps.After mass wasting, the valley was barred by the rock-avalanche deposit. This, in turn, triggered a westward switch of drainage thalweg and stream incision. The present Strassberg valley is an epigenetic bedrock gorge 1.5 km in length and down to 100 m in depth. A 234U/230Th calcite disequilibrium age of 9 ± 1 ka from cemented talus indicates that most incision took place during the late-glacial to early Holocene. Aside of the large-scale morphology (valleys, ranges) the drainage, the smaller-scale morphology, and the sediment volumes of the study area are mainly coined by proglacial/paraglacial processes and by rock avalanching. Holocene landscape changes are modest and chiefly comprise aggradation of high-positioned scree slopes, colluvial/alluvial redeposition and stream incision, and slope stabilization by reforestation. Our results underscore that intramontane sceneries are mosaics with respect to the age of landforms and that large parts of the landscape still are off geomorphic equilibrium with interglacial conditions.</abstract>

Early late-glacial rock avalanche and its lasting effects on drainage and sediment dispersal (Strassberg valley catchment, Northern Calcareous Alps, Austria)

<abstract xmlns="http://www.w3.org/1999/xhtml">Two sections of the klippen zones in the Wienerwald area have been investigated for their stratigraphy: (1) The Gern section of the Main Klippen Zone, a part of the Gresten Klippen Zone, and (2) the St. Veit Klippen Zone in the Lainz Tunnel and the neighboring outcrops in western Vienna. New biostratigraphic data are based on radiolaria from siliceous intervals and a few findings of calcareous nannofossils from marlstones. In the Gresten Klippen Zone, radiolarian assemblages from limestones of the Gern locality indicate a middle Oxfordian to early Kimmeridgian age of the Scheibbsbach Formation.Radiolarian and nannofossil data from the St. Veit Klippen Zone in the Lainz railway tunnel locality, as well as correlated outcrops from the Lainzer Tiergarten and the Gemeindeberg in the southwest of Vienna, indicate the presence of mainly Bajocian to lower Oxfordian red radiolarites and cherts (Rotenberg Formation). Siliceous, grey limestones and cherts of the Fasselgraben Formation range from the upper Oxfordian–Kimmeridgian to the Valanginian–Barremian.The Main Klippen Zone was derived from the European margin to the north, and this zone is regarded as a Helvetic paleogeographic unit. The St. Veit Klippen Zone in the Lainz Tunnel section contains no ophiolitic material and shows a tectonic contact with the surrounding Rhenodanubian nappe system, which indicates no primary sedimentary contact of the St. Veit Klippen Zone with the Flysch units, as well as demonstrating the presence of two structurally separated Alpine tectonic units. Thus, a direct correlation with the Ybbsitz Zone is not supported, and an original paleogeographic position in the transition from the Penninic Ocean to the Austroalpine continental fragment is proposed.</abstract>

Faculty of Geography and Geology, Institute of Geological Sciences

Faculty of Geology, Geophysics and Environmental Protection

Institute of Geography, Faculty of Geography and Biology

Jurassic–Cretaceous radiolarian-bearing strata from the Gresten Klippen Zone and the St. Veit Klippen Zone (Wienerwald, Eastern Alps, Austria): Implications for stratigraphy and paleogeography

Institute of Rock Mechanics and Tunnelling

Department für Geodynamik und Sedimentologie

DiGeo: Introduction and a new tutorial to geological maps with QGIS 3.X

AHEAD OF PRINT

Volume 117 (2024): Issue 1 (January 2024)

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Austrian Journal of Earth Sciences

 AUSTRIAN JOURNAL OF EARTH SCIENCES is the official journal of the Austrian Geological (ÖGG), Mineralogical (ÖMG), Palaeontological (ÖPG) and Hydrogeological (ÖVH) Societies, hosted by a country that is famous for its spectacular mountains, sedimentary basins and classical fossil sites that were and are the birthplace for many geoscientific concepts in modern Earth science. Further information on the journal may also be obtained from the local website at: www.ajes.at     AUSTRIAN JOURNAL OF EARTH SCIENCE focuses on all aspects relevant to the geosciences of the Alpine realm including the Bohemian Massif, the surrounding sedimentary basins and related regions in Central Europe, for example the Tethyan and Paratethyan realms. As such, we invite contributions from the fields of mineralogy, geology, geophysics, petrology or hydrogeology, as well as all aspects of palaeontology, palaeobiogeography and biostratigraphy that are of relevance to the greater Alpine orogen and its surrounding oceans. Contributions on other regions are welcome if they embed their findings into a conceptual framework that relates the contribution to Alpine-type orogens and Alpine regions in general and are thus relevant to an international audience. Contributions are subject to peer review and editorial control according to SCI guidelines to ensure that the required standard of scientific excellence is maintained.     AUSTRIAN JOURNAL OF EARTH SCIENCES is a peer reviewed journal.   Why subscribe and read   The journal of the Austrian Geological Society is published for more than 100 years, starting in 1908 as ‘Mitteilungen der Geologischen Gesellschaft in Wien’. Traditionally, the main focus of the journal is on Alpine and Austrian geology and applied geosciences but contributions to all aspects of Earth Sciences are welcome. Austrian Journal of Earth Sciences is an Open Access Journal hosted as of 2018 by SCIENDO. For earlier back issues go to the Archive section at: ajes.at/index.php/archive   Why submit   The journal of the Austrian Geological Society is published for more than 100 years, starting in 1908 as ‘Mitteilungen der Geologischen Gesellschaft in Wien’. Traditionally, the main focus of the journal is on Alpine and Austrian geology and applied geosciences but contributions to all aspects of Earth Sciences are welcome. Austrian Journal of Earth Sciences is an Open Access Journal hosted as of 2018 by SCIENDO. As of 2021, AJES represents all Austrian Earth Science societies. For earlier back issues go to the Archive section at: ajes.at/index.php/archive     Archiving   Sciendo archives the contents of this journal in Portico - digital long-term preservation service of scholarly books, journals and collections.   Plagiarism Policy   The editorial board is participating in a growing community of Similarity Check System's users in order to ensure that the content published is original and trustworthy. Similarity Check is a medium that allows for comprehensive manuscripts screening, aimed to eliminate plagiarism and provide a high standard and quality peer-review process. 