Biocorrosion and Rock Art: A Mutual Exclusion at the Origin of Archaeological Voids. Biocorrosion et art pariétal : une exclusion mutuelle à l’origine de vides archéologiques. Biocorrosion and Rock Art: A Mutual Exclusion at the Origin of Archaeological Voids: Methodology, First Results and New Research Perspectives. Biocorrosion et art pariétal : une exclusion mutuelle à l’origine de vides archéologiques: Méthodologie, premiers résultats et nouvelles perspectives de recherche
Type de document : Archive ouverte
| Hiatus, lacunes et absences : identifier et interpréter les vides archéologiques. Actes du 29e Congrès préhistorique de France, 31 mai-4 juin 2021, Toulouse
Auteur(s) : Bruxelles, Laurent | Beauvillier, Manon | Barriquand, Lionel | Cailhol, Didier | Dardenne, Élodie | Develle, Anne-Lise | Frouin, Millena | Galant, Philippe | Galera, Jean-Louis | Genuite, Kim | Le Guillou, Yanik | Hoellinger, Sixtine | Jaillet, Stéphane | Kaniewski, David | Lartiges, Bruno | Le Roux, Gaël | Otto, Thierry | Pallier, Céline | Pisapia, Celine | Pfendler, Stéphane | Pons-Branchu, Edwige | Touron, Stéphanie | Vanara, Nathalie
Edité par CCSD ; Société préhistorique française
- Type de document
- info:eu-repo/semantics/bookPart ; Book sections
- Langue
- Français
- Date de publication
- 2024-04-01
- Résumé
- International audience.
For millennia, men and animals have frequented the caves. They are therefore known for their archaeological remains, including rock art, but also for sheltering sometimes exceptionally large colonies of bats.The impact of bats on the underground environment has been identified for a few years with for example the development of bell holes on the ceiling and for the localized weathering caused by guano leachates on the walls. It now appears that this impact had been greatly underrated. Indeed, in recent years, research in karst science has integrated and developed this aspect, revealing the extended impact of biocorrosion, even in temperate latitudes. Thus, it is now accepted that the walls of caves that have been occupied at different times by large colonies of bats have been greatly modified. They are not only weathered, but also sometimes very largely reshaped, to the point that the volume of the gallery has considerably increased. New wall features, hitherto unknown, have been identified and a whole new catalog invites the re-reading of parietal morphologies.Obviously, in the initially decorated caves, rock art was the first affected by this retreat since it is located at the interface between the rock and the cave atmosphere. We can easily imagine that where biocorrosion was active, these traces of prehistoric artists may have disap-peared. The identification of the impact of biocorrosion therefore makes it possible to explain certain “voids”, without rock art, and above all to put into perspective the absence of rock art in some parts of the caves or even in some caves. In return, given the generalization of this phenomenon, we can then even ask why there are still decorated cavities? The most outstanding examples show that these are nearly always caves or parts of caves that were no longer accessible to bats. In these specific cases, a localized or generalized plugging of the caves blocked access to the bats after the passage of the artists, allowing the conservation of these fragile remains until today.It is therefore important now to review all the decorated caves, but also the cavities occupied or accessible during the Palaeolithic, to assess in detail the impact of biocorrosion. This necessarily interdisciplinary approach brings together geomorphologists, archaeolo-gists, geochemists, as well as climatologists, ethologists and microbiologists. Several interdisciplinary research programs, including a Collective Research Program (PCR), have therefore just been launched. The results of course concern archaeology, but also other aspects such as paleoenvironments, anthropization, ethology and the evolution of bats, and can be helpful for the conservation of archaeological sites and historical monuments.During 2021, more than a hundred cavities were visited in South of France. The identification of many features of biocorrosion has enabled us to begin the construction of a catalog allowing users of the underground environment (speleologists, karstologists, archae-ologists, chiropterologists, etc.) to identify these forms and to know how to interpret them. Several high-resolution 3D scans of cavities were performed to quantify these features. They will serve as a basis for aerological modelling and in particular to better understand the dissemination of acid gases released from guanos decay. More than 200 samples were taken for geochemical analyses, dating, extraction of paleoenvironmental data or to try to find DNA from ancient bat colonies. Many of them are still in progress, but the first results overpass our expectations. Thus, we were able to identify many types of phosphates and the complex reactions that lead to their formation in caves. They do not origin from megafauna bones as it was claimed before, but rather from the mineralization and leaching of bat guanos. Regarding guano deposits, we have developed a pollen extraction protocol and the first analyzes show the full potential for paleoenvironmental reconstructions. Thus, in one cores, we observed the fairly fast passage from the mixed oak forest to an open environment marked by agro-pastoral activities. We therefore perceive the impact of Man on the landscape during the end of the Neo-lithic. In the same core, isotopic analyzes show the appearance of a copper peak. It is contemporary with the phase of anthropization shown by the pollens and reflects the beginning of copper metallurgy which signal has been concentrated in the guano of bats, via insects.. This single example therefore shows the potential of guano studies, which now constitute a new proxy in karst environments that usually provide limited paleoenvironmental information.An important series of dating was also conducted in order to constrain the paces of this evolution and to be able to correlate it with human activities. Several U/Th dating have been conducted on speleothems weathered by biocorrosion and then sealed by a new generation of calcite. This shows us that biocorrosion can be old and sometimes go back to the Eemian. By its action of smoothing the walls of the caves, it prepared the background for the Paleolithic artists as in the caves of Pech Merle (Lot) or Chauvet (Ardèche). 14C dating of guanos also held their share of surprises, since it yielded sequences covering both the contemporary period and the historical periods, but also the entire Holocene and even the Upper Pleistocene. Some of these guanos have been dated to 48 ka BP. We will therefore soon have the possibility of studying the paleoenvironments of ancient periods, covering the entire history of our species, Homo sapiens, since its arrival in Europe. Thanks to the support of the MSH-T within the framework of the APEX 2021 call for projects, we have been able to develop cross-ap-proaches, involving Toulouse laboratories, allowing both to better characterize the processes of biocorrosion and correlative features that can be detected on the walls, but also to develop paleoenvironmental approaches. This research, also conducted within the frame-work of a Collective Research Program (Ministry of Culture), with the support of Occitanie region and PyGar research program, has enabled significant progress in this innovative but very promising field.
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Depuis des millénaires, les hommes et les animaux ont fréquenté le milieu souterrain. Les grottes sont donc réputées pour les vestiges archéologiques qu’elles contiennent, dont notamment des œuvres pariétales, mais aussi pour abriter des colonies de chauves-souris parfois très importantes.Si l’impact des chiroptères sur le milieu souterrain est connu depuis quelques années pour la formation de coupoles en bell holes au plafond et pour les altérations localisées provoquées par « les jus de guano » sur les parois et au sol, il apparaît désormais que cet impact avait été largement sous-évalué. En effet, ces dernières années, les recherches en karstologie ont intégré et développé cet aspect, révélant à quel point, même sous nos latitudes, l’impact de la biocorrosion est majeur. Ainsi, il est désormais acquis que les parois des grottes qui ont été occupées à différentes périodes par d’importantes colonies de chauves-souris ont été fortement modifiées. Elles sont non seulement altérées, mais aussi parfois très largement refaçonnées, au point que les sections de la galerie ont considérablement aug-menté. De nouvelles formes de parois, jusque-là interprétées différemment voire inconnues, ont été identifiées, procurant de nouvelles clés de lecture des morphologies pariétales.Dans les grottes initialement ornées, les œuvres pariétales ont été les premières touchées par ce recul puisqu’elles se situent à l’interface entre la roche et l’atmosphère de la cavité. On peut donc imaginer que là où la biocorrosion a agi, les traces des artistes de la Préhistoire ont disparu. L’identification de l’impact de la biocorrosion permet donc d’expliquer certains « vides » archéologiques, et surtout de rela-tiviser les absences d’œuvres dans certaines parties de cavité, voire dans certaines grottes. En retour, compte tenu de la généralisation de ce phénomène, on peut alors s’étonner qu’il reste encore des cavités ornées. Les exemples les plus célèbres (Mas d’Azil, Ariège ; Chauvet, Ardèche ; Cosquer, Bouche-du-Rhône ; Lascaux, Dordogne…) montrent qu’il s’agit la plupart du temps de grottes ou de parties de grottes qui n’étaient plus accessibles aux chiroptères ; c’est-à-dire qu’après le passage des artistes, une fermeture localisée ou généralisée de la cavité a bloqué l’accès aux chauves-souris, permettant la préservation de ces œuvres fragiles jusqu’à leur découverte. Il est donc important désormais de revoir l’ensemble des grottes ornées, mais aussi des cavités occupées au cours du Paléolithique pour évaluer en détail l’impact de la biocorrosion. Cette approche, nécessairement interdisciplinaire, regroupe des géomorphologues, des archéologues, des géochimistes, et également des climatologues, des éthologues et des microbiologistes. Plusieurs programmes de recherche interdisciplinaires, dont un programme collectif de recherche (PCR), viennent donc d’être lancés. Les résultats concernent bien entendu l’archéologie et aussi d’autres aspects comme les paléoenvironnements, l’anthropisation, l’éthologie et l’évolution des espèces de chiroptères, mais également la protection des sites archéologiques, du patrimoine bâti et des chauves-souris, elles aussi en danger.
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- Bruxelles, Laurent , Beauvillier, Manon , Barriquand, Lionel , Cailhol, Didier , Dardenne, Élodie , Develle, Anne-Lise , Frouin, Millena , Galant, Philippe , Galera, Jean-Louis , Genuite, Kim , Le Guillou, Yanik , Hoellinger, Sixtine , Jaillet, Stéphane , Kaniewski, David , Lartiges, Bruno , Le Roux, Gaël , Otto, Thierry , Pallier, Céline , Pisapia, Celine , Pfendler, Stéphane , Pons-Branchu, Edwige , Touron, Stéphanie , Vanara, Nathalie, Biocorrosion and Rock Art: A Mutual Exclusion at the Origin of Archaeological Voids. Biocorrosion et art pariétal : une exclusion mutuelle à l’origine de vides archéologiques. Biocorrosion and Rock Art: A Mutual Exclusion at the Origin of Archaeological Voids: Methodology, First Results and New Rese..., CCSD,
