Event-Based Landslide Modeling in the Styrian Basin, Austria: Accounting for Time-Varying Rainfall and Land Cover

In June 2009 and September 2014, the Styrian Basin in Austria was affected by extreme events of heavy thunderstorms, triggering thousands of landslides. Since the relationship between intense rainfall, land cover/land use (LULC), and landslide occurrences is still not fully understood, our objective was to develop a model design that allows to assess landslide susceptibility specifically for past triggering events. We used generalized additive models (GAM) to link land surface, geology, meteorological, and LULC variables to observed slope failures. Accounting for the temporal variation in landslide triggering, we implemented an innovative spatio-temporal approach for landslide absence sampling. We assessed model performance using k-fold cross-validation in space and time to estimate the area under the receiver operating characteristic curve (AUROC). Furthermore, we analyzed the variable importance and its relationship to landslide occurrence. Our results showed that the models had on average acceptable to outstanding landslide discrimination capabilities (0.81–0.94 mAUROC in space and 0.72–0.95 mAUROC in time). Furthermore, meteorological and LULC variables were of great importance in explaining the landslide events (e.g., five-day rainfall 13.6–17.8% mean decrease in deviance explained), confirming their usefulness in landslide event analysis. Based on the present findings, future studies may assess the potential of this approach for developing future storylines of slope instability based on climate and LULC scenarios.

Life in the fluvial hinterland of the late Sarmatian Sea (middle Miocene): a rare terrestrial fossil site in the Styrian Basin (Austria)

This paper describes the section and fossil content of a former gravel pit in the Eastern Styrian Basin (SE Austria), which exposes sediments of a fluvial system, ranging from within channel to overbank environments. A predominately terrestrial gastropod fauna of 15 species so far, was recovered from a palaeosol formed in a moist and vegetated, floodplain or abandoned channel. Up-section, a shallow freshwater pond/lake developed within the floodplain, settled by fishes, molluscs and ostracods. By integrating regional geological and biostratigraphical data derived from the terrestrial gastropod fauna as well as from the other recovered biota, these strata are of late middle Miocene (late Sarmatian s.str.) age. Hence, this fossil site provides a rare insight into the terrestrial habitats in the hinterland of the Sarmatian Sea and their biota, which are otherwise barely known in Central Europe.

Geochemistry, environmental and provenance study of the Middle Miocene Leitha limestones (Central Paratethys)

Mineralogical, major, minor, REE and trace element analyses of rock samples were performed on Middle Miocene limestones (Leitha limestones, Badenian) collected from four localities from Austria (Mannersdorf, Wöllersdorf, Kummer and Rosenberg quarries) and the Fertőrákos quarry in Hungary. Impure to pure limestones (i.e. limited by Al2O3 contents above or below 0.43 wt. %) were tested to evaluate the applicability of various geochemical proxies and indices in regard to provenance and palaeoenvironmental interpretations. Pure and impure limestones from Mannersdorf and Wöllersdorf (southern Vienna Basin) show signs of detrital input (REEs = 27.6 ± 9.8 ppm, Ce anomaly = 0.95 ± 0.1 and the presence of quartz, muscovite and clay minerals in impure limestones) and diagenetic influence (low contents of, e.g., Sr = 221 ± 49 ppm, Na is not detected, Ba = 15.6 ± 8.8 ppm in pure limestones). Thus, in both limestones the reconstruction of original sedimentary palaeoenvironments by geochemistry is hampered. The Kummer and Fertőrákos (Eisenstadt–Sopron Basin) comprise pure limestones (e.g., averages Sr = 571 ± 139 ppm, Na = 213 ± 56 ppm, Ba = 21 ± 4 ppm, REEs = 16 ± 3 ppm and Ce anomaly = 0.62 ± 0.05 and composed predominantly of calcite) exhibiting negligible diagenesis. Deposition under a shallow-water, well oxygenated to intermittent dysoxic marine environment can be reconstructed. Pure to impure limestones at Rosenberg–Retznei (Styrian Basin) are affected to some extent by detrital input and volcano-siliciclastic admixture. The Leitha limestones at Rosenberg have the least diagenetic influence among the studied localities (i.e. averages Sr = 1271 ± 261 ppm, Na = 315 ± 195 ppm, Ba = 32 ± 15 ppm, REEs = 9.8 ± 4.2 ppm and Ce anomaly = 0.77 ± 0.1 and consist of calcite, minor dolomite and quartz). The siliciclastic sources are characterized by immobile elemental ratios (i.e. La/Sc and Th/Co) which apply not only for the siliciclastics, but also for marls and impure limestones. At Mannersdorf the detrital input source varies between intermediate to silicic igneous rocks, while in Kummer and Rosenberg the source is solely silicic igneous rocks. The Chemical Index of Alteration (CIA) is only applicable in the shale-contaminated impure limestones. CIA values of the Leitha limestones from Mannersdorf indicate a gradual transition from warm to temperate palaeoclimate within the limestone succession of the Badenian.

Loess caves of Austria – a preview

Loess caves account for a negligible amount of Austria's caves only – despite the fact that the areas covered by loess and loess-loam comprise several thousand square kilometres. Loess can be found in the northern and eastern foreland of the Alpine Mountain Range as well as in the Styrian Basin south of the Alps. Only a handful of caves have been mapped so far, concentrated at a few spots. This eye-catching fact documents a certain lack of exploration rather than a general lack of loess caves. According to Striebel (2005) and others most loess caves are formed by piping and gully erosion, initiated by inhomogeneities like disintegrating roots and animal burrows where the infiltrating water causes fast-growing pipe structures, subsequently enlarging to caves that can be entered by cavers.The rate of cave evolution is tremendous. In several cases – so far investigated – the earliest onset of cave formation lies within the early 20th Century. This can be dated as the required gradient was man-made at that time. On the other hand distinctive alterations of the caves took place within 30 years. This can be documented strikingly by comparing old and new cave maps. The crucial points – from a quantitative point of view – for the formation of loess caves are still under fundamental discussion as there are severe differences in local climatic parameters – some of the areas belong to the driest in Austria – lithologies, gradients and human interventions. Furthermore, the role of dissolution of calcitic components enhancing the subsequent erosion remains ambiguous.