Characterization and differentiation of rock varnish types from different environments by microanalytical techniques

Macholdt, Dorothea S.; Jochum, Klaus Peter; Pöhlker, Christopher; Arangio, Andrea M.; Förster, Jan‐David; Stoll, Brigitte; Weis, Ulrike; Weber, Bettina; Müller, Maren; Kappl, Michael; Shiraiwa, Manabu; Kilcoyne, A. L. D.; Weigand, Markus; Haug, Gerald H.; Alamri, Abdullah

doi:10.1016/j.chemgeo.2017.04.009

Cited by 36 publications

(86 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For comparison, the range of typical, worldwide collected Type I varnish plots (gray shaded field) and the data obtained from varnish from NW Saudi Arabia (yellow/gray symbols) are additionally plotted in Figure 2. The element composition obtained from the Hima varnish agrees well with that of usual Type I varnish, and thus with typical varnish from arid desert environments (Macholdt et al, 2017b), even though the Pb and Ce amounts are relatively low and Cu quite high (Figure 2a). This supports the hypothesized trace metal enrichment mechanism through leaching of dust and scavenging by the Mn oxyhydroxides in the varnish (Dorn, 2007;Goldsmith et al, 2014;Thiagarajan and Lee, 2004).…”

Section: Rock Varnish and Mineral Dust Chemical Compositionsupporting

confidence: 75%

“…Rock varnish samples from the Hima region were investigated by fs LA-ICP-MS, which confirmed that the varnish belongs to the group of Type I varnish (Macholdt et al, 2017b) typically found in arid desert environments. The relatively low Mn concentration and Mn/Fe ratio in our varnishes are also consistent with their formation under quite dry conditions (Broecker and Liu, 2001;Dorn and Oberlander, 1982;Liu, 2003;.…”

Section: Discussionmentioning

confidence: 67%

“…The gray shaded area identifies the typical range for Type I varnish (arid desert environment varnish). The mass fractions of the elements from the Ha'il region (AR-Y being Yatib, AR-J being Jubbah) are plotted in yellow; these ranges and values are adapted from the dataset published in Macholdt et al (2017b). In (a) the rock varnish LA-ICP-MS results are normalized to the UCC and in (b) to the composition of carbonaceous chondrites.…”

Section: Rock Varnish and Mineral Dust Chemical Compositionmentioning

confidence: 99%

“…On the contrary, there is a large body of evidence that suggests an involvement of microorganisms (bacteria or fungi) in the oxidation and precipitation of Mn (Dorn et al, 2013;Gadd, 2017;Jones, 1991;Krinsley et al, 2012Krinsley et al, , 2017Krumbein and Jens, 1981;Kuhlman et al, 2006Kuhlman et al, , 2008Laudermilk, 1931;Marnocha and Dixon, 2013;Wang et al, 2011). The lack of microfossils (Macholdt et al, 2015(Macholdt et al, , 2017b and of evidence for the presence of activated Mnoxidizing enzymes in varnish (Lang-Yona et al, 2018) does not rule out a bacterial role in Mn precipitation, considering the length of time involved in its formation (Dorn and Krinsley, 2011;Krinsley et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Rock varnish on petroglyphs from the Hima region, southwestern Saudi Arabia: Chemical composition, growth rates, and tentative ages

2019

View full text Add to dashboard Cite

We investigated rock varnish formed on sandstone and petroglyphs in the Hima area, southwestern Saudi Arabia. To characterize the rock varnish, we made in-situ measurements by portable x-ray fluorescence (pXRF) and analyzed samples by femtosecond laser-ablation inductively coupled–plasma mass spectrometry (fs LA-ICP-MS). Detailed chemical analysis of the rock varnish samples and adjacent soil or aeolian dust yielded information about the varnish’s geochemical context and formation mechanism. Untypically low positive Ce anomalies in the rock varnish samples correlated with negative Ce anomalies in the dust, supporting the hypothesis that the dust is the source of the varnish material. To study the varnish development, we made use of the fact that engraving the petroglyphs exposes a fresh bare sandstone surface without varnish, on which varnish regrows subsequently. We determined by pXRF the areal density of manganese (Mn) and iron (Fe) that had been deposited as rock varnish since the creation of the rock art. The rates of Mn deposition in the newly formed varnish were then estimated by correlating the areal density of Mn in Ancient Arabian and Old Arabic inscriptions with their known age ranges. The observed deposition rates showed substantial variability resulting from differences in exposure conditions of the rock surface, but were in a range comparable with that of our previous measurements in northwestern Arabia. This variability could be reduced significantly by referencing the measurements to the intact varnish adjacent to the individual petroglyphs. This normalization provided a much clearer relationship between varnish deposition and age, and enabled tentative ages to be assigned to rock art motifs without previously known ages. These tentative ages spanned most of the Holocene period and were consistent with the culturally or ecologically derived ages of the animal and human figures depicted in the rock art and the styles of scripts used in different periods.

show abstract

Section: Rock Varnish and Mineral Dust Chemical Compositionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 67%

Section: Rock Varnish and Mineral Dust Chemical Compositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Rock varnish on petroglyphs from the Hima region, southwestern Saudi Arabia: Chemical composition, growth rates, and tentative ages

2019

View full text Add to dashboard Cite

show abstract

“…Varnished rocks can be clustered into five groups, based on their elemental composition, formation rate and structure, implying possible differences in formation mechanisms (Macholdt et al, 2017). In this study, we focus on Type I varnish, found in arid environments and enriched in manganese and iron oxides.…”

Section: Introductionmentioning

confidence: 99%

Insights into microbial involvement in desert varnish formation retrieved from metagenomic analysis

Lang‐Yona

Maier

Macholdt

et al. 2018

Environ Microbiol Rep

View full text Add to dashboard Cite

Desert varnishes are dark rock coatings observed in arid environments and might resemble Mn-rich coatings found on Martian rocks. Their formation mechanism is not fully understood and the possible microbial involvement is under debate. In this study, we applied DNA metagenomic Shotgun sequencing of varnish and surrounding soil to evaluate the composition of the microbial community and its potential metabolic function. We found that the α diversity was lower in varnish compared to soil samples (p value < 0.05), suggesting distinct populations with significantly higher abundance of Actinobacteria, Proteobacteria and Cyanobacteria within the varnish. Additionally, we observed increased levels of transition metal metabolic processes in varnish compared to soil samples. Nevertheless, potentially relevant enzymes for varnish formation were detected at low to insignificant levels in both niches, indicating no current direct microbial involvement in Mn oxidation. This finding is supported by quantitative genomic analysis, elemental analysis, fluorescence imaging and scanning transmission X-ray microscopy. We thus conclude that the distinct microbial communities detected in desert varnish originate from settled Aeolian microbes, which colonized this nutrient-enriched niche, and discuss possible indirect contributions of microorganisms to the formation of desert varnish.

show abstract

“A Survey of Surveys” Revisited: Current Approaches to Landscape and Surface Archaeology in Southern Africa

Hallinan

2022

Afr Archaeol Rev

View full text Add to dashboard Cite

Characterization and differentiation of rock varnish types from different environments by microanalytical techniques

Cited by 36 publications

References 55 publications

Rock varnish on petroglyphs from the Hima region, southwestern Saudi Arabia: Chemical composition, growth rates, and tentative ages

Rock varnish on petroglyphs from the Hima region, southwestern Saudi Arabia: Chemical composition, growth rates, and tentative ages

Insights into microbial involvement in desert varnish formation retrieved from metagenomic analysis

“A Survey of Surveys” Revisited: Current Approaches to Landscape and Surface Archaeology in Southern Africa

Contact Info

Product

Resources

About