Artificial weathering of rock types bearing petroglyphs from Murujuga, Western Australia

Abstract

Murujuga in Western Australia has the largest concentration of ancient rock engravings (petroglyphs) in the world. However, the Murujuga rock art is potentially threatened by local industrial air pollution, in particular by acid rain, but unambiguous scientific evidence is still missing. Here, we report on results of an accelerated weathering experiment, simulating Murujuga weather and climate conditions that was designed and performed to test whether the expected small changes in chemical, mineralogical, and physical characteristics of the rock surface can be detected and reliably quantified by various analytical means. Locally acquired Murujuga granophyre and gabbro samples with natural varnish were artificially weathered for up to four months in a climate chamber under conditions that simulated 2 years of natural weathering. Mineralogical, chemical, and physical changes were qualitatively monitored by X-ray diffraction and confocal Raman spectroscopy, and quantified by colorimetry, portable X-ray fluorescence spectrometry, and micro-computed tomography. In addition, artificial rainwater that was sprinkled over the rock samples was collected and analysed by inductively-coupled plasma mass spectrometry. The results show significant chemical and physical changes of the surfaces of the rock varnish after 1 month of artificial weathering. The analytical results demonstrate that it is possible to quantitatively monitor small changes caused by the weathering of gabbro and granophyre. Therefore, such a semi-actualistic experimental approach, when carefully designed, potentially allows testing the hypothesis that the weathering rate of the Murujuga petroglyphs is increased by local industrial air pollution. Further experimental work is currently under way.

Rock Surface Strain In Situ Monitoring Affected by Temperature Changes at the Požáry Field Lab (Czechia)

“…Based on these considerations, a field laboratory test was developed in the new Požáry test site, to monitor the evolution of a controlled natural system. Similar controlled tests can be reproduced at a laboratory scale, simulating natural conditions in a climate chamber [ 30 , 31 , 32 ]. This instrument allows accounting for the complexity of nature, in which more variables such as humidity, temperature, and thermal cycles act on the evolution of stresses and strain, as shown on small rock samples [ 30 ].…”

A Multi-Analytical Approach to Infer Mineral–Microbial Interactions Applied to Petroglyph Sites in the Negev Desert of Israel

“…Rock art, in the form of petroglyphs and pictograms, is found worldwide and has an undoubtedly immense value as it is considered one of the first forms of expression of ancient societies and the prehistoric precursor to art [1][2][3][4]. As part of the natural landscape, petroglyphs are constantly exposed to anthropogenic and natural weathering processes [5][6][7], but despite this, knowledge regarding preservation and conservation of this valuable cultural heritage is limited.…”

“…Although there is considerable research and published work focusing on the physical state of rock art sites worldwide [7][8][9], research focusing on the role of biological agents in the deterioration of rock art is still minimal. Nevertheless, physical and chemical weathering processes initiated by stone-dwelling microorganism (biodeterioration) can play a significant role in the degradation patterns of the stone [10].…”