BEDDING ASSOCIATED TO THE DYNAMICS OF STONE-BANKED SHEETS IN AN ALPINE ENVIRONMENT (LA MORTICE, SOUTHERN ALPES, FRANCE)

Bedding associated to the dynamics of stone-banked sheets in an alpine environment (La Mortice, southern Alpes, France). This paper emphasiz es the role of stone-banked sheets in bedding of slope deposits at La Mortice (3170 m). Coarse particles sorting due to frost heaving and ru noff occurs within sheets leading to the development of stone banks an d surface pavements in connection with matrix-rich beds. Burying of st ones at the sheet front by the frost creep induced movement of matrix- rich layers makes it possible the formation of coarse openwork beds. C ryoturbation, heaving of blocky materials and intense leaching of fine particles through the different beds disturb the stratification. A co mparison between deposits from the east and the northwest facing slope s of La Mortice and Andean examples clearly shows that bedding is bett er developped when superficial freeze-thaw cycles are frequent and the depth of seasonal freezing shallow.