Flusskorridore und Auenstrukturen im schweizerischen Mittelland (nördliches Alpenvorland) | River corridors and alluvial structures in Central Switzerland (northern sub-alpine area)
Long-term spatial variation of river channel distribution in this alluvial valley zone is described for two examples by analysing historical maps covering a period of over 300 years. Such a time series enables the identification of the occupied river corridor or «Pendelband». Two river sections in northern Switzerland were chosen, one of the Aare river and one of the Reuss river to analyse the spatial evolution of the river channels over time, as well as alluvial structures. Knowledge of the river corridor as an historical reference give us an important guideline when developing appropriate regional measures for river restoration projects.
Die Abflussregimes der Schweiz
Die Abflussregimetypisierung der Schweiz fuhrt zu 16 Regimetypen, welche sich quantitativ beschreiben und in ihrer raumlichen Verbreitung festhalten lassen. Dadurch ist es nun moglich, in Einzugsgebieten (10-500 km2) ohne Direktmessung eine Abschatzung des mittleren Abflussverhaltens und der damit verbundenen Richtwerte zu erhalten. Methodisch wurden konventionelle Typisierungsverfahren und Verfahren der Distanzgruppierung z.T. kombiniert angewendet. Die raumliche Umsetzung gelingt in den alpinen Gebieten mittels der arealen Vergletscherung und der mittleren Einzugsgebietshohe; uber den letzteren Parameter lassen sich auch die sudalpinen Regimetypen raumlich einordnen. Im Mittelland geschieht die raumliche Festlegung der Typen mittels FOURIER- und Trendflachenanalyse. Es wird die praktische Bedeutung dieser Abflussregimetypisierung aufgezeigt.
Preservation in microbial mats: mineralization by a talc-like phase of a fish embedded in a microbial sarcophagus
Microbial mats have been repeatedly suggested to promote early fossilization of macroorganisms. Yet, experimental simulations of this process remain scarce. Here, we report results of 5 year-long experiments performed onfish carcasses to document the influence of microbial mats on mineral precipitation during early fossilization. Carcasses were initially placed on top of microbial mats. After two weeks, fishes became coated by the mats forming a compact sarcophagus, which modified the microenvironment close to the corpses. Our results showed that these conditions favoured the precipitation of a poorly crystalline silicate phase rich in magnesium. This talc-like mineral phase has been detected in three different locations within the carcasses placed in microbial mats for more than 4 years: 1) within inner tissues, colonized by several bacillary cells; 2) at the surface of bones of the upper face of the corpse buried in the mat; and 3) at the surface of several bones such as the dorsal fin which appeared to be gradually replaced by the Mg-silicate phase. This mineral phase has been previously shown to promote bacteria fossilization. Here we provide first experimental evidence that such Mg-rich phase can also be involved in exceptional preservation of animals.