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<jats:title>Abstract</jats:title><jats:p>The Posidonia Shale in the basement of the North Alpine Foreland Basin of southwestern Germany represents an important archive for environmental changes during the Toarcian oceanic anoxic event and the associated carbon isotope excursion (T-CIE). It is also an important hydrocarbon source rock. In the Salem borehole, the Posidonia Shale is ~ 10 m thick. The lower 7.5 m (1763.5–1756.0 m) of the Posidonian Shale and the uppermost part of the underlying Amaltheenton Formation were cored and studied using a total of 62 samples. Rock–Eval, palynological, maceral, biomarker and carbon isotope data were collected to assess variations in environmental conditions and to quantify the source rock potential. In contrast to most other Toarcian sections in southwest Germany, TOC contents are high in sediments deposited during the T-CIE, but reach a peak in post-CIE sediments. Biomarker ratios suggest that this reflects strong oxygen-depletion during the T-CIE (<jats:italic>elegantulum</jats:italic> to lower <jats:italic>elegans</jats:italic> subzones), but also during the <jats:italic>falciferum</jats:italic> Subzone, which is also reflected by a prolonged dinoflagellate cyst blackout. While sediments of the <jats:italic>tenuicostatum</jats:italic> Zone to the <jats:italic>elegans</jats:italic> Subzone are thinner than in neighbouring sections (e.g., Dotternhausen), sediments of the <jats:italic>falciferum</jats:italic> Subzone are unusually thick, suggesting that increased subsidence might have contributed to anoxia. The T-CIE interval is very thin (0.75 m). δ<jats:sup>13</jats:sup>C values of <jats:italic>n</jats:italic>-alkanes show that the maximum negative isotope shift predates the strongest basin restriction during the T-CIE and that the carbon isotope shift is recorded earlier for aquatic than for terrigenous organisms. In Salem, the Posidonia Shale is thermally mature and highly oil-prone. The residual source petroleum potential is about 0.8 tHC/m<jats:sup>2</jats:sup>.</jats:p> <jats:p><jats:bold>Graphical Abstract</jats:bold></jats:p>

<jats:title>Abstract</jats:title><jats:p>Borehole image data and a 1D-stress model built on open hole logs, leak-off tests (LOT) and image logs are used to evaluate the potential of seismicity caused by fault triggering during geothermal heat production in the city of Vienna. Data were derived from a 4220 m deep geothermal exploration well that investigated the geothermal potential of fractured carbonates below the Miocene fill of the Vienna Basin. The well penetrated several normal faults of the Aderklaa Fault System (AFS) that offset Pleistocene terraces at the surface and hence are regarded as active. Stress-induced borehole failures and 1D geomechanical modeling proves that the potential reservoirs are in a normal fault stress regime with <jats:italic>S</jats:italic><jats:sub><jats:italic>v</jats:italic></jats:sub> &gt; <jats:italic>S</jats:italic><jats:sub>Hmax</jats:sub> &gt; <jats:italic>S</jats:italic><jats:sub>hmin</jats:sub>. While stress magnitudes in the upper part of the well (down to about 2000 m) are significantly below the magnitudes that would trigger the rupture of critically oriented faults including the AFS, stresses in the lower part of the drilled section in the pre-Neogene basement (below about 3300 m) are not. Data evidence a rotation of <jats:italic>S</jats:italic><jats:sub>Hmax</jats:sub> for about 45° at a fault of the AFS at 3694 m to fault-parallel below the fault suggesting that the fault is active. Critical or near-critical stressing of the fault is corroborated by the stress magnitudes calculated from the 1D geomechanical model. The safety case to exclude unintended triggering of seismic fault slip by developing geothermal reservoirs in close vicinity to one of the branch faults of the AFS may therefore be difficult or impossible to make.</jats:p> <jats:p><jats:bold>Graphical Abstract</jats:bold></jats:p>