My research focuses on the evolution of mountains and the complexities of the earth surface processes that it involves. Past climate has modulated the thickness and the extent of alpine glaciers and ice caps. Therefore quantifying the spatial and temporal fluctuations in ice extent provides insights into past climate.
My PhD is about the quantification of the glacier erosion in the Western Alps (Mer de Glace glacier, Mont Blanc massif, France) during the last glacial (since Last Glacial Maximum to present day). The main objective of this project is the reconstruction of paleo-ice extent of the Mer de Glace glacier using a multi-method approach: optically stimulated luminescence (OSL) surface exposure dating and terristrial cosmogenic nuclide dating (TCN).
OSL surface exposure dating is sensitive to light, based on the progressive bleaching of the OSL signal in a rock sample that depends on its exposure time, mineralogical properties and environmental conditions. The longer a surface is exposed to sunlight, the deeper the bleaching is occuring, showing in alpine glacier setting a positive correlation between exposure age and elevation. The main advantages of this dating technic is to be able to reconstruct exposure history from decade to millennium, while having a high spatial resolution (low cost in prepation time) .
Coming from a mountain environment I have always been fascinated by the complexity of the evolution of this landscape and by natural processes (geological, glaciological, hydrological) that control it. In this context, I focused my academic training in the fields of geosciences. Graduated of a MSc in Solid Earth geosciences (Joseph Fourier university, Grenoble, France), I decided to focus my career on cryosphere tematics. I thus engaged myself in the scientific cooperation of the Glacioclim Observatory of La Paz, in Bolivia (www.great-ice.ird.fr). Over two years, I was responsible of the glaciological, meteorological and hydrological monitoring of glaciated drainage basins (Zongo and Charquini Sur). After this professional experience, I decided to engage myself in research to understand the feedback mechanisms between climate and earth surface processes in mountain environment.
- Lehmann, B., Valla, P.G., King, G.E., Herman, F., Investigation of OSL surface exposure dating to reconstruct post-LIA glacier fluctuations in the French Alps (Mer de Glace, Mont Blanc massif), Quaternary Geochronology (2018), doi: 10.1016/j.quageo.2017.12.002.
- King, G.E., Valla, P.G. and Lehmann, B., Accepted. OSL Rock Surface and Rock Surface-Exposure Dating. Invited contribution to “Handbook of Luminescence Dating”, Eds: M. Bateman and I. Bailiff
- LED 2017 conference in Capetown (SA): The Ann Wintle Prize for Best oral for Applications – Benjamin Lehmann Using OSL and 10Be surface exposure dating to constrain ice-extent histories and post-glacial erosion (Abstract)
- EGU 2016 in Vienna (AUT): Outstanding Student Poster and PICO (OSPP) Awards 2016 – Benjamin Lehmann LGM using OSL surface exposure dating (Link & Poster) : Reconstruction of glacier fluctuations in the Western Alps since the
- UKLUM15 conference in Glasgow (UK): Student Poster Awards 2016 – Benjamin Lehmann Abstract) : Constraining post-LGM glacier fluctuations using OSL-surface exposure dating in the Western Alps (
- EGU 2018 – Talk: Benjamin Lehmann (Abstract) : Constraining past ice-extent and post-glacial erosion by combining OSL and 10Be surface exposure dating
- SGM 2017 – Talk: Benjamin Lehmann (Abstract) : Constraining paleo-glacier extent and local erosion using OSL and 10Be surface exposure dating
- LED 2017 – Talk: Benjamin Lehmann Using OSL and 10Be surface exposure dating to constrain ice-extent histories and post-glacial erosion (Abstract) :
- EGU 2017 – Talk: Benjamin Lehmann Reconstruction of glacier fluctuations in the Mont‐Blanc massif, western Alps: a multi‐method approach (Abstract) :
- SGM 2016 – Talk: Benjamin Lehmann Abstract) : Reconstruction of glacier fluctuations in the Mont-Blanc massif, western Alps: a multi-method approach (
- EGU 2016 – Poster: Benjamin Lehmann LGM using OSL surface exposure dating (Abstract) : Reconstruction of glacier fluctuations in the Western Alps since the
- SGM 2015 – Poster: Benjamin Lehmann Abstract) : OSL-surface exposure dating as a tool to constrain post-LGM glacier fluctuations in the Western Alps (
- UKLUM15 – Poster: Benjamin Lehmann Abstract) : Constraining post-LGM glacier fluctuations using OSL-surface exposure dating in the Western Alps (
SNSF Doctoral Student
Université de Lausanne
Institute of Earth Surface Dynamics (IDYST)
le Géopolis – Bureau 3151
1015 Lausanne, Switzerland
Tel: +41 (0)21 692 3543