Les spéléothèmes de la grotte Chauvet-Pont-d'Arc : apports chronologiques et paléoclimatiques. Synthèse des travaux publiés

Abstract

The study of the Chauvet Cave (Ardèche, South-France) speleothems, initiated in 1999, brought results about the chronology of the history of the cave and allows paleoclimatic reconstructions of the last climatic cycle. We present here a synthesis of already published results that were obtained with the help of numerous collaborators. Fiveteen speleothems were analysed : 11 stalagmites, 3 flowstones and one stalactite. Thanks to 90 uranium-thorium ages, three main phases of speleothem growing have been defined : (i) 124.2-99.8 ka coinciding with M1S5 ; (ii) 32.8-22.3 ka that covers MIS3 and 2 and (iii) 15.2-0 ka covering the Lateglacial and Holocene periods and in which most speleothems developed. A growth hiatus that coincides with the climatic deterioration of the last glacial maximum was precisely dated on a single stalagmite between 22.1 ka ± 0.4 and 15.3 ka ±0.25. These U-Th datings also permitted to constrain the age of a collapse that happened far inside the cave (Salle Hillaire) after 7.7 ka ± 1. 6. Ln the same area, the first calcite layers that grew on the archaeological soil were dated at ~ 27.8 ka±1.9 confirming the old 14C ages made on prehistoric charcoals found on this soil (33. 7 to 35.3 cal. ka). Finally, the oldest ages found on the first calcite layers of several stalagmites that grew on the top part of the entrance collapse demonstrate that the Chauvet Cave entrance was closed before 13.1 ka ±0.1, which is in agreement with other dating methods that dated this collapse at about 22 ka. Parallel to the U-Th dating, more than 600 isotopic analyses, performed on the speleothem calcite (δ18O δ13C), permitted to reconstruct detailed paleoclimatic changes since 15.3 ka. These results highlight similarities but also differences with Greenland ice core records and gave precise ages to climatic events that occurred during the Bølling-Allerød and Younger-Dryas periods.