A. Beauvais et C. Roquin, PETROLOGICAL DIFFERENTIATION PATTERNS AND GEOMORPHIC DISTRIBUTION OF FERRICRETES IN CENTRAL-AFRICA, Geoderma, 73(1-2), 1996, pp. 63-82
Geomorphic distribution and petrological differentiation patterns of f
erricretes widespread on landsurfaces were studied in the Dembia-Zemio
area, southeastern Central African Republic. Four types of ferricrete
s are distributed on high plateaux, hillslopes and low plateaux. The m
ain contrast corresponds to the differentiation between ferricretes of
high plateaux rich in poorly hydrated minerals, hematite and kaolinit
e, and those covering hillslopes and low plateaux richer in hydrated m
inerals, goethite and gibbsite, A Principal Component Analysis of geoc
hemical and mineralogical data was used to characterize the main diffe
rentiation patterns of ferricretes in relation with their petrographic
facies and the geomorphic features of the landscape. The distribution
of secondary minerals and their relationships to trace elements withi
n and between the ferricrete types reflects differences in weathering
and erosion processes. Our results document that the petrological patt
erns and the distribution of ferricretes are related to geomorphic fea
tures depending on hydroclimatic variations that govern the landscape
evolution of many tropical shields.