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Geological contacts - central Northern Calcareous Alps (Eastern Alps, Austria)

Geological mapping in the central Northern Calcareous Alps (Eastern Alps, Austria) during the years 2021 to 2023 has been performed. The aim of mapping has been to revise the 1:50,000 scale geological maps published by the Austrian Geological Survey (GBA/Geosphere) for inconsistencies in lithostratigraphic identification and contact definition. Critically, maps in the area were completed at a time when the emplacement of thrust sheets through gliding tectonics was still the dominant paradigm and pre-date advances in salt tectonics (see Fernandez et al., 2024, for a complete discussion). In consequence, mapping has aimed to correctly identify contacts compatible with salt tectonics, units remobilized in mass-transport deposits, low-angle thrusting, and syn-orogenic extension. The focus has been on two key areas of the central Northern Calcareous Alps: the Traun River and the Lammertal River valleys (roughly between longitudes 13° and 14°E, latitudes 47°30' and 48°N). Revised geological contacts (stratigraphic contacts and faults) are provided as SHP files. Stratigraphic contacts contain attributes describing the stratigraphic unit above and below and the type of contact. Faults contain information relating to type and sense of throw. No polygons have been generated. Data are in WGS84 UTM33 coordinates.

Raw data and plots of 40Ar/39Ar age dating of polyhalite from the evaporitic Permian Haselgebirge Formation

The measurements were conducted at the University of Salzburg, Department of Geography and Geology, in the years 2007-2015. Polyhalite samples were manually reduced to small pieces with a hammer. They were washed with destilled water and dried with isopropanol to free them from dust and Cl-ions of halite. Chlorine produces Ar isotopes during irradiation, which may tamper the proportion of Ar isotopes from polyhalite. Grains of 200–250 µm size were selected under the microscope. A sufficient number of grains of each sample were packed into aluminium-foil and put into quartz vials. Details of the analytical 40Ar/39Ar technique is described in Leitner et al. (2014) and Cao et al. (2017). Irradiation was conducted for 16 hours in the Magyar Tudományos Akadémia (MTA) Központi Fizakai Kutato Intézet (KFKI) reactor (Debrecen, Hungary). Flux-monitors were placed between the samples for calculation of the J-values. The distance between adjacent flux-monitors was c. 5 mm. Corrections for interfering isotopes were the same as described earlier: Correction factors were calculated from 45 analyses of co-irradiated Ca-glass samples and 70 analyses of K-glass samples, and are: 36Ar/37Ar(Ca) = 0.000225, 37Ar/39Ar(Ca) = 0.000614, 38Ar/39Ar(K) = 0.0117, and 40Ar/39Ar(K) = 0.0266. Variation in the flux of neutrons were monitored with DRA1 sanidine standard for which a 40Ar/39Ar plateau age of 25.26 ± 0.05 Ma has been reported (van Hinsbergen et al. 2008). 40Ar/39Ar analyses were carried out at the Department of Geography and Geology at the University of Salzburg. The equipment used was the same as described earlier: 40Ar/39Ar analyses are carried out using a ultra high vacuum Ar-extraction line equipped with a combined MERCHANTEKTM UV/IR laser system, and a VG-ISOTECHTM VG-3600 noble gas mass spectrometer. Stepwise heating analyses of samples are performed using a defocused (~1.5 mm diameter) 25 W CO2-IR laser operating in Tem00 mode at wavelengths between 10.57 and 10.63 µm. The laser is controlled from a PC, and the position of the laser on the sample is monitored on the computer screen via a video camera in the optical axis of the laser beam through a double-vacuum window on the sample chamber. Gas clean-up is performed using one hot and one cold Zr-Al SAESTM getter. Gas admittance and pumping of the mass spectrometer and the Ar-extraction line are computer controlled using pneumatic valves. The VG-3600 is an 18 cm radius 60° extended geometry sector field mass analyzer instrument, equipped with a bright Nier-type source operated at 4.5 kV. Measurements are performed on an axial electron multiplier in static mode, peak-jumping and stability of the magnet is controlled by a Hall-probe. For each increment the intensities of 36Ar, 37Ar, 38Ar, 39Ar, and 40Ar are measured, the baseline readings on mass 35.5 are automatically subtracted. Intensities of the peaks are back-extrapolated over 16 measured intensities to the time of gas admittance either by a straight line or a curved fit, depending on intensity and type of pattern of the evolving gas. Inspection of intensities was applied with regard to background, system blanks, interfering isotopes and post-irradiation decay of 37Ar. Calculations of isotope ratios, errors, ages and plateau ages followed suggestions of McDougall and Harrison (1999), Scaillet (2000), Steiger and Jäger (1977) and Ludwig (2012).

Formula units of polyhalite from the evaporitic Permian Haselgebirge Formation

Electron microprobe analyses were conducted at the University of Salzburg, Department of Geography and Geology, in the year 2011. Measurements were performed on a JEOL electron microprobe (JXA-8600), equipped with a wave-length dispersive system. An acceleration voltage of 15 kV and a low sample current of 20 nA were applied to prevent decomposition of polyhalite under the electron beam. Additionally, the spot was defocused to a diameter of 15 µm and after measurement of sulfur, the sample was moved one beam diameter to start measurement of potassium and calcium. Sulfur, potassium and calcium were all measured with the same analyzing crystal. Synthetic and natural mineral standards were used to analyse the emitted wave lengths of the sample and to quantify their amount. Standard ZAF correction calculation revealed the composition in oxide weight percent (doi:10.1594/PANGAEA.942486). The calculation method after Love/Scott1 revealed the formula units of polyhalite.

Electron microprobe analysis of polyhalite from the evaporitic Permian Haselgebirge Formation

Electron microprobe analyses were conducted at the University of Salzburg, Department of Geography and Geology, in the year 2011. Measurements were performed on a JEOL electron microprobe (JXA-8600), equipped with a wave-length dispersive system. An acceleration voltage of 15 kV and a low sample current of 20 nA were applied to prevent decomposition of polyhalite under the electron beam. Additionally, the spot was defocused to a diameter of 15 µm and after measurement of sulfur, the sample was moved one beam diameter to start measurement of potassium and calcium. Sulfur, potassium and calcium were all measured with the same analyzing crystal. Synthetic and natural mineral standards were used to analyse the emitted wave lengths of the sample and to quantify their amount. Standard ZAF correction calculation revealed the composition in oxide weight percent. The calculation method after Love/Scott1 revealed the formula units of polyhalite (doi:10.1594/PANGAEA.942485).

Electron microprobe analysis and Ar-Ar age dating of polyhalite from the evaporitic Permian Haselgebirge Formation

To test polyhalite age dating of the mineral polyhalite [K2Ca2Mg(SO4)4·2H2O], samples of the evaporitic Permian Haselgebirge Formation were collected in the Eastern Alps. Samples were taken from two salt bodies. The salt body of Altaussee (UTM 33T 405316 5278325) has a vertical thickness of >800 m. Samples were collected in the Altaussee mine (ALT). The salt body of Bad Dürrnberg-Berchtesgaden (UTM 33T 351091 5278007) is at least 1000 m thick. The salt body comprises two separate mines, where samples were collected, Bad Dürrnberg (DÜ) and Berchtesgaden (BGD) salt mines. The samples were collected during several field trips, and investigated at the University of Salzburg during the years 2007-2015. Electron microprobe analyses were conducted to determine possible chemical variations of polyhalite.

Seismicity catalogue for the Eastern Alps (Swath-D)

We present a new, consistently processed seismicity catalogue for the Eastern and Southern Alps, based on the temporary dense Swath-D monitoring network. The final catalogue includes 6,053 earthquakes for the time period 2017-2019 and has a magnitude of completeness of −1.0ML. The smallest detected and located events have a magnitude of −1.7ML. Aimed at the low to moderate seismicity in the study region, we generated a multi-level, mostly automatic workflow which combines a priori information from local catalogues and waveform-based event detection, subsequent efficient GPU-based event search by template matching, P & S arrival time pick refinement and location in a regional 3-D velocity model. The resulting seismicity distribution generally confirms the previously identified main seismically active domains, but provides increased resolution of the fault activity at depth. In particular, the high number of small events additionally detected by the template search contributes to a more dense catalogue, providing an important basis for future geological and tectonic studies in this complex part of the Alpine orogen.

High Resolution Moho Map of the Eastern Alps

This dataset contains a high resolution Moho map of the in the Eastern Alps focused on the SWATH-D network. The Moho map was produced by manually picking the Moho on narrow transects (CCP stacks) calculated with the receiver function method. These manual picks were then fit with a spline in 3-D. Three separate and sometimes overlapping maps are included corresponding to the European, Adriatic, and Pannonian Mohos. In addition to Moho depth, Ps travel time and crustal average Vp/Vs are also reported. Version history: 30 November 2021: release of version 1 13 March 2023: release of version 1.1. Changes: Performed manual adjustment of 1-D splines (before fitting 2-D spline) to avoid unphysical geometries

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