The variability of Cr content is studied along a toposequence of soils deve
loped on amphibolite and gneiss. Amphibolites are Ca-rich, gneiss are K- an
d Cr-rich. A mineralogical study shows that biotite is the main bearer of C
r, and explains the relationship between K and Cr in the alterites. This re
lation still exists in pedological horizons. The nature of the parent mater
ial and the erosion are the main factors explaining the variability of Cr a
long the toposequence. (C) 2001 Academic des sciences / Editions scientifiq
ues et medicales Elsevier SAS.