Detection and origin of different types of annual laminae in recent stalagmites from Zoolithencave, southern Germany: Evaluation of the potential for quantitative reconstruction of past precipitation variability

Abstract

An arrangement of three stalagmites from Zoolithencave (southern Germany) was analysed for different types of annual laminae using both microscopic and geochemical methods. The speleothems show visible laminae (consisting of a clear and a brownish, pigmented layer pair) as well as fluorescent and elemental laminae. The age of the speleothems was constrained to 1800 to 1970 AD by 14 C-dating of a charcoal piece below the speleothems, detection of the 14 C bomb peak, as well as counting of annual laminae. Dating by the 230 Th/U-method was impossible due to detrital contamination. On the annual time-scale, the variability of Mg, Ba, and Sr is controlled by Prior Calcite Precipitation (PCP) resulting in lower values during the wet season (autumn/winter) and vice versa. Yttrium and P are proxies for soil activity and are enriched in the brownish, pigmented layers. However, Y and P are also influenced by detrital content superimposing the soil activity signal. Aluminium and Mn are proxies for detrital content. Lamina thickness shows a significant correlation with the amount of precipitation of previous December and current January, February, March, April, May, and December (DJFMAMD) recorded at the nearby meteorological station Bamberg. Thus lamina thickness is a proxy for past precipitation, which is confirmed by the good agreement with a precipitation reconstruction based on tree-ring width from the Bavarian forest. This highlights the potential of these speleothems for climate reconstruction at annual resolution.