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On the importance of the number of freeze/thaw cycles in rock shelter walls' mechanical erosion processes

Authors
  • Vandevelde, Ségolène
  • Brochier, Jacques Élie
  • Camus, Hubert
  • Jeannet, Marcel
  • Petit, Christophe
  • Slimak, Ludovic
Publication Date
Mar 14, 2022
Source
HAL-CEA
Keywords
Language
English
License
Unknown
External links

Abstract

An archaeological site under a rockshelter is not only made up of its archaeological layers; it is also made up of vault and walls that evolve over time and can also be the place for archaeological and environmental recording. Research carried out at the Mandrin Cave (Drôme, France) has led us to study the relationships between these two sedimentary dynamics (on the walls and on the ground), in particular by analysing the disintegration of the walls.In this paper, we will focus on the rate of walls crumbling, how to estimate it and observe its evolution over time, the factors that control it and the palaeo-environmental information that its study can provide. To do this, the "Minimum Number of calcite Doublets" (MND) that formed on the wall before the fall of each clast is used as a proxy to assess the rate of wall disintegration. These data are also compared with the palaeo-environmental information provided by the analysis of the microfauna for each of the archaeological layers. This comparison of data highlights the variable importance of cryoclasticity as a factor of wall desquamation. Above all, it reveals that the association between cold phases and abundance of gelifracts is not necessarily the rule. On the contrary, the processes are much more complex and we show in this article that the number of freeze/thaw cycles, fundamental in the cryoclastic process, is increased in temperate periods.This study, based on field data rather than laboratory experiments, also allows us to characterise the evolution of the rate of wall disintegration and thus the relative importance of freeze-thaw alternations for the different Pleistocene sedimentary units of the Mandrin Cave, with contrasting climatic conditions.

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