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Light in the Cave: Opal coating detection by UV-light illumination and fluorescence in a rock art context. Methodological development and application in Points Cave (Gard, France) use asterix (*) to get italics
Marine Quiers, Claire Chanteraud, Andréa Maris-Froelich, Émilie Chalmin-Aljanabi, Stéphane Jaillet, Camille Noûs, Sébastien Pairis, Yves Perrette, Hélène Salomon, Julien Monney
<p style="text-align: justify;">Silica coatings development on rock art walls in Points Cave questions the analytical access to pictorial matter specificities (geochemistry and petrography) and the rock art conservation state in the context of pigment studies. However, classical in situ spectroscopic techniques appear unsuccessful to identify these coatings, which also prevent pigment characterization. In this study, we propose using a UV fluorescence method for opal coating detection based on the fluorescence specificities of uranyl-silica complexes composing these deposits. A coupling of spectral identification using UV laser-induced fluorescence spectroscopy with UV illumination was performed on samples and µ-samples from the Points Cave rock art site. The well-defined peaks observed in fluorescence emission spectra due to uranyl ions validate opal detection and its correspondence with green fluorescence observed under UV light at micro- and macroscopic scales. In situ optical measurements under UV illumination reveal the presence of opal coating, especially on rock art walls in Points Cave. Opal occurrence and repartition observations provide the first insights into Points Cave wall evolution and chronological constraints linked to opal coating development. Regarding the strong interactions with pigment suggested by multiscale observations of samples and µ-samples, the impact of the presence of opal coating on Points Cave rock art conservation quality is questioned. Thus, by developing a specific and non-destructive characterization method for opal coatings, this study opens up a new approach for the study of decorated wall taphonomy and proposes utilizing mineralization both as markers of the natural history of caves and as an indication for their uses by ancient human groups.</p>,,,,,,,,,,,,,,,,,,,,, should fill this box only if you chose 'All or part of the results presented in this preprint are based on data'. URL must start with http:// or https:// should fill this box only if you chose 'Scripts were used to obtain or analyze the results'. URL must start with http:// or https://
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Silica coating, uranyl, UV fluorescence, in situ detection, rock art cave, optical methods, Upper Palaeolithic
Archaeometry, Europe, Rock art, Taphonomy, Upper Palaeolithic
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2021-10-25 11:12:48
Aitor Ruiz-Redondo