Climate fluctuations, volcanism and geochemical transport between rain, soils, volcanic ash, and the fjords ecosystems at the end of the world

A research group led by Prof. Dr. G. Wörner of the Department of Geochemistry and Isotope Geology of the Geosciences Center has worked in a long-term collaboration with Prof. Dr. Rolf Kilian in the inaccessible fjord and island zone of the southernmost Patagonian Andes in Chile to reconstruct the climate history in this region. Rolf Kilian died in May 2019 in a tragic accident during fieldwork in Patagonia. Now, important work of a jointly supervised PhD student and an extended working group could be published in high-ranking international journals (Klaes et al., 2022a; Klaes et al., 2022b).

The work is based on extensive soil analyses and, most importantly, the detailed geochemical analyses on an approximately 4500-year-old stalagmite. This stalagmite is the southernmost limestone deposit of this type ever found and, based on its fine stratification, allows geochemical analyses with high temporal resolution and to reconstruct changing climate and chemical processes at the Earth’s surface. This is because the compositions of the sub-millimeter thick layers reflect environmental conditions and the climate-controlled input of chemical substances from the surrounding soils and rocks over thousands of years in the past.

As a completely new finding, remnants of volcanic dust from eruptions of nearby volcanoes were found in the soils and even in the stalagmite from the cave. The volcanic input can also be proven by geochemical anomalies in the stalagmite (e.g. incorporation of sulphur) and can even be assigned to individual explosive volcanic eruptions of the geological past by dating the stalagmite layers. These volcanic deposits are of fundamental importance for the chemical processes in the moors and have a particularly strong effect under the influence of the extreme precipitation in the region. Together with detailed studies of organic and mineral components embedded in the stalagmite, new insights into the effects of eruptions of different sizes on the Magellanic peatland ecosystem could thus be clearly documented and better placed in time.

Volcanic input provides nutrients and thus makes a critical contribution to aquatic bioproductivity in adjacent fjord ecosystems. This input, in turn, is directly related to the extreme climatic conditions prevailing in the region and their past fluctuations in a complex set of processes.