Morgana Cave is located in
Val di Scerscen
, Central Italian Alps. The cave opens at an altitude of 2,600 m a.s.l. close to the retreating glacier
Vedretto di Scerscen
, and its entrance was ...discovered 30 years ago hidden underneath the glacier. A characteristic of this cave is the occurrence of vermiculation deposits on the walls and ceiling. In general, the composition of the microbial communities in cave vermiculations is relatively unknown and rarely investigated. Here we present the data of a geomicrobiological study of vermiculations from an Alpine cave subjected to extreme climate conditions. The microbial communities were dominated by 13 main phyla of
Bacteria
, and contained a negligible percentage (<1%) of
Archaea
. The two major bacterial classes were
Gammaproteobacteria
and
Betaproteobacteria
, whose metabolic traits were mainly associated with the nitrogen cycle. In addition, psychrophilic and methanotrophic bacterial groups were identified. The occurrence of a large number of uncultured members, at the lowest taxonomic ranks, indicated the presence of still unexplored microbial taxa in the vermiculations.
The Schönberg-Höhlensystem (SBH) is not only the longest cave system in the Eastern Alps (length 156 km, depth 1061 m), but a significant proportion of the passages have developed on or just below ...two surfaces that dip 1.7° to the NE. These so-called "speleogenetic phases" are rarely developed in caves of the Northern Calcareous Alps and have not yet been confirmed by detailed morphological mapping. Furthermore, the deep parts of the cave offer the possibility to study the active epiphreatic zone for a distance of 1.6 km. Detailed morphological mapping shows that the main level at about 1500 m a.s.l. and a second 140 m higher developed as distinct speleogenetic phases, and the dip of the planes to the NE is consistent with palaeo-flow. Isolated vadose trenches formed at saddle points are further evidence. Correlations with other caves at similar altitudes suggest an Upper Miocene to Lower Pliocene age. With few exceptions, a northeastern palaeo-flow can be observed down to about 1050 m a.s.l. However, 100 m above this there appears to have been a late phase with an opposite palaeo-flow direction, and below this altitude this SW palaeo-flow direction prevails. These morphological observations allow us to propose a complex model. During low and moderate flow there is drainage to the north. During floods, a restriction in the north causes backwater and an overflow threshold to the SW is exceeded, and then most of the water flows in this direction. This observation of dual flow behaviour can help to better understand the behaviour of the karst water table and to interpret complex results from tracer experiments. The almost ubiquitous paragenetic features in the SBH are due to sediments derived from the local Upper Jurassic Radiolarite Group. For the evolution of karst plateaus in the Northern Calcareous Alps, these observations support a local and rather radial palaeo-drainage of the Totes Gebirge, as opposed to a through-flow of allogenic waters as is likely for other karst massifs.
The 116 km-long and 1560 m-deep Hirlatzhöhle is one of the major cave systems in the Northern Calcareous Alps (NCA; Austria). It is located in the NW part of the Dachstein, an extensive karst massif ...encompassing 576 km² with its highest point at 2995 m a.s.l. In contrast to most other caves in the NCA, Hirlatzhöhle comprises old (epi)phreatic passages located up to 1 km above the base level as well as two modern major drainage systems. The aim of this study is to define the palaeo- and the active flow conditions in combination with speleogenesis, and the age of the cave levels of Hirlatzhöhle. We use morphological as well as sedimentological studies and correlations with other caves. Another difference from cave systems in the NCA is that the majority of passages in Hirlatzhöhle are not developed within the so-called Giant Cave Level between 1200 and 1800 m a.s.l., but deeper between 800 and 1300 m. Most parts of Hirlatzhöhle developed under epiphreatic conditions as indicated by rills and condensation corrosion cupolas, which is the case for much other cave systems in the NCA. In contrast, paragenetic features like canyons and ceiling channels are relatively rare as are insoluble sediments. Elongated scallops indicate that flow velocities were high and abrasive sediments were abundant. Opposite to the nearby Dachstein-Mammuthöhle and other caves east of it that show a west-directed palaeo-flow, scallops in Hirlatzhöhle indicate a NE-directed palaeo-flow and an autogenic recharge. Modern drainage is autogenic and N- to NE-directed as well. Even though burial age dating did not give reasonable results for Hirlatzhöhle yet, the correlation with other adjacent caves suggests a Late Pliocene to Early Pleistocene age of the main palaeo-phreatic level. This is supported by an infinite U-Th age (>0.6 Ma) of a flowstone.
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