Fossil cosmogenic 3He record from K-Ar dated basaltic flows of Mount Etna volcano (Sicily, 38°N):: Evaluation of a new paleoaltimeter

This study investigates the reliability of a paleoaltimeter based on the elevation dependency of the cosmogenic nuclides production rate. The proposed method relies on "fossil" cosmogenic record. Indeed, measuring the cosmogenic nuclide concentration in an exposed and then buried lava flow combined with an independent estimate (by K-Ar or 40Ar/39Ar dating) of the past exposure duration theoretically allows recording "fossil" cosmogenic production rates, which can thus be converted in paleoelevations. This approach was tested by measuring cosmogenic He-3 (He-3(c)) in olivines and clinopyroxenes of Quaternary K-Ar dated basaltic flows of Mount Etna volcano (Sicily, 38 degrees N). The agreement within uncertainties (1 sigma <= 500 m) between current and cosmogenic-derived elevations demonstrates the paleoaltimeter reliability. However, dating imprecision, Earth's paleomagnetic fluctuations and erosion contemporary to the flow exposure are parameters that may affect the accuracy and the precision of the method on older geological scales. Their respective influences were thus carefully evaluated and discussed to conclude that the paleoaltimeter can potentially reach resolutions better than 1000 m, even for Cenozoic records. (c) 2005 Elsevier B.V. All rights reserved.