Chrono-, litho- and conodont bio-stratigraphy of the Rauchkofel Boden Section (Upper Ordovician\u2013Lower Devonian), Carnic Alps, Austria

An updated stratigraphy of the Rauchkofel Boden Section, a classical reference section for the Carnic Alps that exposes rocks from the Katian (Upper Ordovician) to the Pragian (Lower Devonian) is here presented, following latest developments in conodont taxonomy and biostratigraphy, as well as in chrono - stratigraphy, and the recent introduction of a new lithostratigraphic outline of the Carnic Alps. The original conodont collection of the \u201970s and \u2bc80s was restudied and complemented by a detailed resampling in order to achieve a more precise conodont biostratigraphic assignment. Twenty-five conodont Zones are now documented. The lithostratigraphy is precisely fixed to the new lithostratigraphic scheme of the Pre-Variscan sequence by definition of seven distinct formations. Finally, the position of chronostratigraphic boundaries is discussed

Uppermost Ordovician to lowermost Devonian conodonts from the Valentint\uf6rl section and comments on the post Hirnantian hiatus in the Carnic Alps

A detailed biostratigraphic investigation has been carried out by means of conodonts in the uppermost Ordovician-lowermost Devonian sector of the Valentint\uf6rl cliff, located in the Austrian part of the Carnic Alps. Biostratigraphic data document in continuity all conodont biozones from the lowermost Ludlow to the upper P\u159\ueddol\ued, with such a limited thickness to suggest that the Valentint\uf6rl section exposes the most condensed upper Silurian section in the Carnic Alps documented so far. A general discussion on the extension of the hiatus between Ordovician and Silurian sequences in the Carnic Alps is presented. Three new conodont species belonging to genera Cuspigrandiosa, Wurmiella and Zieglerodina are described, but left in open nomenclature awaiting more specimens to be collected

Geological map and stratigraphic evolution of the central sector of the Carnic Alps (Austria-Italy).

The central sector of the Carnic Alps spans the border between Austria and Italy and consists of a succession ranging from the Upper Ordovician to the lowermost part of the upper Carboniferous that has been recently revised in order to formalize the stratigraphic units. Although this area was mapped both on the Austrian and Italian side, the presence of different units with different stratigraphic boundaries prevented from a complete representation of the stratigraphic relationships and the lateral geometrical variability within the basin. We focused mainly on the Devonian \u2018transitional facies\u2019 that indirectly reflect the establishment and the demise of a platform. The basin shows a transition from a ramp-type to a rimmed shelftype profile that occurred between the upper part of the Pragian to the lower Emsian that is constrained by the increasing abundance of reef-derived gravity-driven rudstone deposits. The platform system reached its maximum expansion around the end of the Eifelian and the beginning of the Givetian when the largest debris deposits have been shown to accumulate. Although less productive, the platform system appears to persist until roughly the lower part of the upper Frasnian when the rudstone deposits become depleted of platformderived clasts and interbedded with microbial limestone. This evolution might have been caused by a sea-level drop event

Geological map and stratigraphic evolution of the central sector of the Carnic Alps (Austria-Italy)

The central sector of the Carnic Alps spans the border between Austria and Italy and consists of a succession ranging from the Upper Ordovician to the lowermost part of the upper Carboniferous that has been recently revised in order to formalize the stratigraphic units. Although this area was mapped both on the Austrian and Italian side, the presence of different units with different stratigraphic boundaries prevented from a complete representation of the stratigraphic relationships and the lateral geometrical variability within the basin. We focused mainly on the Devonian \u2018transitional facies\u2019 that indirectly reflect the establishment and the demise of a platform. The basin shows a transition from a ramp-type to a rimmed shelftype profile that occurred between the upper part of the Pragian to the lower Emsian that is constrained by the increasing abundance of reef-derived gravity-driven rudstone deposits. The platform system reached its maximum expansion around the end of the Eifelian and the beginning of the Givetian when the largest debris deposits have been shown to accumulate. Although less productive, the platform system appears to persist until roughly the lower part of the upper Frasnian when the rudstone deposits become depleted of platformderived clasts and interbedded with microbial limestone. This evolution might have been caused by a sea-level drop event

Organism-substrate interactions and astrobiology: Potential, models and methods

Organism-substrate interactions and their products \u2013 biogenic structures \u2013 are important biosignatures on Earth. This study discusses the application of ichnology \u2013 the study of organism-substrate interactions \u2013 to the search for present and past life beyond Earth. Three main questions are addressed: (1) Why to look for biogenic structures (i.e. traces and ichnofabrics) beyond Earth? (2) What biogenic structures to expect on other planets, moons and asteroids? (3) How to study extraterrestrial biogenic structures? Review of terrestrial evidence highlights a set of properties that make traces and ichnofabrics important for the search of potential extraterrestrial life: trace fossils preserve the activity of soft-bodied organisms; biogenic structures are resilient to processes that obliterate other biosignatures (i.e. mechanical and chemical degradation, diagenesis, tectonism and metamorphism); traces are very visible biosignatures; traces indicate environment and behaviour; traces can be universal biosignatures, i.e., biosignatures ideally suited for detecting any type of life. A model of organism-substrate interactions beyond Earth is here proposed. Expected extraterrestrial traces are those that manifest behaviours that allow to maintain homeostasis: excavations, meandering traces and biodeposition structures. Most of the existing rovers and orbiters provide basic instruments for searching these traces. It is here suggested that the search for extraterrestrial biogenic structures by rovers would also benefit from artificial adjustable lighting, GPR, LiDAR, and drilling equipment with optical televiewer. In this study, open-access databases of rover and orbiter imagery have been searched for traces and ichnofabrics, but no unquestionable evidence of biogenic structures beyond Earth has been found besides those produced by humans. This sounds along the lines of the famous Fermi Paradox: if the universe is teeming with aliens, where are their traces? Results of this search show that habitable environments are not the only place to look for biogenic structures; non-habitable environments such as moons without atmosphere can favour the preservation of shallow-tier traces. The better preservation potential of traces compared to other biosignatures greatly widens the issue of planetary protection, including the interaction between astronauts or vehicles and the substrate may produce disturbances. Although this study highlights a new direction of study with the tools and concepts of ichnology, dialogue between the astrobiological and ichnological communities is needed to use its full potential and possibly answer one of the major questions of science: Does life exist beyond Earth

Stratigraphic correlations between the continental and marine Tethyan and Peri-Tethyan basins during the Late Carboniferous and the Early Permian

Volume: 20Start Page: 521End Page: 59