³⁶Cl and ¹⁰Be production rate calibrations in the Pleistocene Ardèche lava flow (eastern edge of the Massif Central, France)

Full text: In situ produced cosmogenic nuclides have revolutionized geomorphology by allowing quantification of surface processes operating at the Earth's surface. Numerous studies have been dedicated to the calibration of production rates in common target minerals (quartz for ¹⁰Be, CaCO₃ mainly for ³⁶Cl) because these minerals contain the main target elements (O, Si for ¹⁰Be, Ca for ³⁶Cl). Most of these calibrations have been performed on geomorphological features (moraines, glacially polished rocks, boulders from landslides) where accurate independent ages are available (mostly from ¹⁴C), most of them being younger than 20 ka, minimizing the effects of denudation. The aim of this project is to work on minerals from basaltic rocks collected in the Ardéche mountains (SE France) on sites already studied and dated by Ar/Ar by Sasco et al (2017). As these well preserved and well exposed lava flows cover a temporal range of 20 to 200 ka, they offer a unique opportunity to calibrate production rates over such a long period and to assess if these long term production rates are in agreement with the ones actually used.