Anthropogenic and climate signals in late-Holocene peat layers of an ombrotrophic bog in the Styrian Enns valley (Austrian Alps)

Using peat bogs as palaeoenvironmental archives is a well-established practice for reconstructing changing climate and anthropogenic activity in the past. In this paper, we present multi-proxy analyses (element geochemistry, pollen, non-pollen palynomorphs, stable Pb isotopes, humification, ash content) of a 500 cm long, C-14-dated peat core covering the past similar to 5000 years from the ombrotrophic Purgschachen Moor in the Styrian Enns valley (Austrian Alps). Early indications of low settlement and agricultural activity date to similar to 2900 cal BCE. An early enrichment of Cu was found in peat layers corresponding to the late Copper Age (similar to 2500 cal BCE). These enrichments are attributed to Cu mining activities in the Eisenerz Alps. More pronounced increases in cultural indicators (cultivated plants, shrubs, herbs, charcoal) in the pollen record and enrichments of trace metals suggest significant human impact in the vicinity of Purgschachen Moor in the middle Bronze Age (similar to 1450-1250 cal BCE), in the late Bronze Age (similar to 1050-800 cal BCE) and in the period of the late La Tene culture (similar to 300 cal BCE-1 cal CE). The greater part of the Iron Age and the Roman imperial period are each characterized by a general decline in anthropogenic indicators compared to previous periods. Distinct enrichments of Pb and Sb in the sample that corresponds to similar to 900 cal CE are attributed to medieval siderite mining activity in the immediate vicinity of Purgschachen Moor. The results of this interdisciplinary study provide evidence that strong, climate-controlled interrelations exist between the pollen record, the humification degree and the ash content in an ombrotrophic environment. Human activity, in contrast, is mainly reflected in the pollen record and by enrichments of heavy metals. The study indicates a dry period in the region of the bog around similar to 1950 cal BCE.