Cold environments dynamics documented with cosmogenic nuclides
Résumé
Cold environments dynamics documented with cosmogenic nuclides Cosmogenic nuclides are very rare isotopes that are produced when particles generated in supernovas in our galaxy hit the atmosphere and then the Earth's surface. When the rocks and soils in this thin, ever-changing surface layer are bombarded by such cosmic radiation, the nuclide clock begins to tick. The measurement of the concentrations of these cosmogenic nuclides can then provide dates and rates of geomorphic processes. The use of cosmogenic nuclides is currently revolutionizing our understanding of Earth-surface processes and has significant implications for many Earth science disciplines over timescales of several hundred years to several millions of years. The continual lowering of detection limits over the past decades as a result of technological and methodological advances has made possible measurements of the cosmogenic nuclide (10 Be, 26 Al and 36 Cl, mainly) concentrations produced directly in the Earth's crust (in-situ production) and has thus allowed quantitative investigations previously impossible. These investigations concern, more specifically, 1) superficial deformations, permitting the analysis of certain natural hazards such as seismic and gravitational events, 2) continental paleo-climatology and in particular, the chronology of the most recent deglaciations, 3) interactions between erosiontectonicsclimate, 4) processes of development and evolution of continental surfaces, 5) developments of alteration profiles, and 6) estimations of denudation rates on the scale of the watershed. After a brief historical review of the development of the technique we will see, with the help of few examples, how the use of this dating tool can inform us about glacial dynamics and its implications on climate and sea-level.