Stone cultural heritage in Austria and in Israel

Pictograms and petroglyphs are signs and paintings scratched, carved or painted into rock. They exist all over the world and belong to the earliest forms of expression of mankind. Because of their extraordinary universal value, several rock art sites have been included in the UNESCO World Heritage List (WHL). Therefore, there is a public interest in preserving this valuable cultural heritage. The main objective of the project is for the first time to analyse and compare the most important factors involved in the weathering of petroglyphs in the Alpine regions of Austria and in the Negev desert of Israel. A special focus is on the investigation of microorganisms contributing to weathering. Petroglyphs in Israel and Austria are analysed according to the glossary of rock decay patterns illustrated by the International Committee for Monuments and Cultural Sites (ICOMOS). Further analyses include petrographic and mineral studies (thin sections, X-ray diffraction) as well as microbiological methods (cultivation and molecular biology). One of the main objectives of the study is to develop a basic understanding of the weathering processes necessary to make recommendations to the competent authorities (IAA, BDA) for better protection or treatment of petroglyphs. After a joint on-site sampling (IL, AT), the samples are distributed to the laboratories and each team contributes its own expertise: Mineralogical, petrological and classical microbiological investigations are mainly carried out in Israel, while the NGS studies are carried out in the BOKU laboratory with bioinformatic support from Ben-Gurion University. The results will be openly exchanged between the teams and published in joint publications. A conceivable highlight at the end of the project would be the joint presentation of the results to the respective state authorities for monument preservation (IAA, BDA).

In our project, in collaboration with colleagues from Ben Gurion University in Israel, we investigated and compared the condition of rock carvings (petroglyphs) in two climatically very different areas of the world: (1) In the Negev desert in Israel, the drawings were carved by people into the black patina - the desert varnish - and (2) in the Nothgasse of the Dachstein mountains, Alpine people and salt traders left their markings on the surfaces of the limestone. The rock samples taken from the Negev and the Dachstein were examined microscopically, the upper layers of the rock were analysed in cross-section and the elemental composition of the layers was determined. The microbiological investigation was carried out by cultivating the fungi, cyanobacteria and algae present on and in the drawings, as well as molecular biology using metagenomics. All the data together show that although the drawings in both regions are in a process of biological weathering, a kind of climax has already been reached. From this we deduce that cleaning and removal of the biofilm would have no positive influence on the preservation of the drawings, because this would only initiate a new cycle of recolonisation, again associated with weathering. However, massive changes could take place if the climate in the two regions changes in the long term due to climate change and thus also the currently prevailing microbiological conditions.