Philipp Häuselmann

Dating speleothems from the Silberen Cave System and surrounding areas

Inactive stalagmites from the Silberen cave system and its surroundings (Muota Valley, Central Switzerland) have been dated by the 230Th/U method (alpha spectrometry and TIMS). Several samples yielded ages of approximately 200 ka (MIS 7) and 320 ka (MIS 9), others were beyond the upper limit of the method (about >350 ka) or might have behaved as open systems with respect to uranium. The following complementary dating methods were applied: 234U/238U, paleomagnetism, palynology and electron spin resonance. Paleomagnetism yielded positive inclination of the natural remanent magnetization of two stalagmite samples, corresponding to the Brunhes-epoch ( The uplift rate of the mountains, the corrosion rate of the karstified surface and the incision of the valley bottom, suggest that karstification started 4 to 3 Ma (Middle to Upper Pliocene). The dated speleothems are therefore substantially younger than the beginning of speleogenesis. Inaktive Stalagmiten aus dem Silberen-Hohlensystem und dessen Umgebung (Zentralschweiz) sind mittels der 230Th/U-Methode (Alpha-Spektrometrie bzw. TIMS) datiert worden. Einige Proben ergaben 230Th/U-Alter zwischen von 320 ka (MIS 9) und 200 ka (MIS 7), andere lagen ausserhalb des Zeitfensters der 230Th/U-Methode (>350 ka), wieder andere konnten offene Uran-Systeme gebildet haben. Erganzend zu den numerischen Datierungen wurden versuchsweise weitere Datierungsmethoden eingesetzt: 234U/238U, Palaomagnetik, Palynologie und Elektronen-Spin-Resonanz. Die Palaomagnetik zeigte bei den zwei untersuchten Tropfsteinen eine positive Inklination der naturlichen remanenten Magnetisierung, was der Brunhes-Epoche ( Aus der bekannten Hebungsrate des Gebirges, dem korrosiven Abtrag der Karstoberflache sowie der Eintiefung des Muotatals wurde abgeleitet, dass die Verkarstung im Untersuchungsgebiet vor 4 bis 3 Ma (Mittleres bis Oberes Pliozan) begonnen hat. Die bislang datierten Karsthohlensedimente sind nach diesem Modell also wesentlich junger als der Anfang der Speleogenese.

Effect of Cave Ventilation on Karst Water Chemographs

The data briefly presented in this paper indicate that the degree of ventilation of underground flow paths, inducing more or less degassing of the CO2 dissolved in water, can induce a significant variation in the water mineralization of a karst spring. The presented data also provide indications about further conditions controlling time variations of carbonate dissolution parameters: (1) variations in the mixing ratio of two or several waters (from distinct subcatchment areas) with distinct chemistry; (2) land use with distinct soils (i.e. pCO2) in the catchment area, which is also often related to the elevation of the various parts of the catchment area; (3) localized and quick infiltration vs diffuse and slow infiltration through soils. It must be mentioned here that both concentrations and fluxes of CO2 within all parts of karst systems must be considered in order to understand water chemographs. Both are mainly controlled by soil CO2 production and by water-recharge flux. Further models and dedicated field data are required to better quantify CO2 concentration and fluxes in karst systems.