A revised dating of the deepest part of the French Illimani ice core in Bolivian Andes reconciles ice and speleothems isotopic profiles from the last deglaciation to the mid-Holocene

The age of the deepest part of the French Illimani ice core drilled in 1999 in Bolivia (16.628°S, 67.778°W) was attributed to the Last Glacial Maximum. Large uncertainties remain on this initial dating as it relies on the overall similarity of the isotopic composition of the ice between the Illimani and the Huascarán (Peru, 9°06’S, 77°36’W) ice cores.

Here, we use seven measurements of the isotopic composition of atmospheric oxygen (d¹⁸O_atm) made over the last 5 meters of the core to propose a revised dating. The comparison with the West Antarctic Ice Sheet Divide (WAISD) d¹⁸O_atm profile leads to rejuvenate the initial dating. The age of the bottom of the Illimani core is now between 14.5 kyr and 15.2 kyr BP. The last meters of the Illimani core now covers a period from the end of the Heinrich stadial 1 to the mid-Holocene. The millennial and orbital variations of the Illimani dD over the deglaciation and from the early to the mid-Holocene are now consistent with other paleo-precipitation reconstructions such as the speleothems d¹⁸Ofrom the western pole of the east-west tropical South American precipitation dipole.

Authors: F. Vimeux, A. Landais

Quaternary Science Reviews, 347, 109098, https://doi.org/ 10.1016/j.quascirev.2024.109098, 2025