Casting light on past temperatures

Mouna El Mekki-Azouzi, Chandra Shekhar Pati Tripathi, Gaël Pallares and Frédéric Caupin (team Liquids and Interfaces), with Véronique Gardien from Laboratoire de Géologie de Lyon, have published an article entitled "Brillouin spectroscopy of fluid inclusions proposed as a paleothermometer for subsurface rocks" in the journal Scientific Reports. A press release was issued by UCBL/CNRS.

This collaboration between physicists and geologists provides a new tool for paleoclimate reconstruction. As the concern about global warming grows, it is crucial to improve our understanding of the past evolution of Earth’s climate. Modern climate archives date back from the nineteenth century. To trace temperatures back to geological times, scientists have developed a range of techniques. One of them is based on water droplets trapped during the formation of minerals. These droplets can be found for instance in stalagmites, or in salt deposits left by evaporation of salty water. In some of these trapped droplets, a small bubble is present; its study brings information about the ambient temperature at the time the droplet was trapped. But what to do when the bubble is absent? By shining a laser on one of these small drops, and analyzing the light after its interaction with the liquid (Raman and Brillouin spectroscopy), the authors explain how to obtain the temperature sought for without the need for a bubble.

09/09/2015