Cosmogenic nuclide dating of cave deposits of Mount Granier (Hauts de Chartreuse Nature Reserve, France): morphogenic and palaeogeographical implications
Résumé
Mount Granier lies in the northeast corner of the Chartreuse Mountains. It contains a vast cave system, whose uppermost levels were thought to be of pre-Quaternary age. 10Be/26Al burial dating of two cave deposits in the oldest passages, widely spaced but belonging to a same gallery level which formed after the last folding phase, gave ages of 4.3 Ma and 3.4 Ma, indicating that these levels are of at least Pliocene age. In addition, the rates of denudation estimated according to the analytical data are unusually low in this alpine context but show an acceleration during the pre-Quaternary period of interest, ranging from 7 m/Ma to 14 m/Ma. Data from karst deposits serve as reference and comparison site for Alpine chronology as well as for cave genesis and palaeogeographical reconstructions, similar to that of the Siebenhengste massif in Switzerland.