Bauxitführende laterite auf dem trappbasalt indiens als fossile, polygenetisch veränderte bodenbildung

Abstract

Bauxite-bearing laterites from three regions of India are investigated: (1) Halar district (Gujerat); (2) Western Ghats near Kolhapur; (3) plateaux of the Bihar Mountains, with quantitative chemical analyses, X-rays, microscopically and as to macroscopic fabrics. These laterites have formed on trap basalts. This type of laterite originated on a low relief at low position in relation to the sea level during Early Tertiary time. Vertically, well-subdivided profiles have developed with a sharp, lower boundary preserving the macroscopic fabrics and the volume of the former basalt. In addition, the profiles show horizontal differentiation of facies into Fe- and Si-rich parts in the former center of the plateaux and Al-rich bauxites at the fossil drainage borders. This horizon which is wide-spread over large areas of India became dislocated by younger tectonics. Paleogeography and mineral paragenesis of the lateritic bauxites were preserved by marine sediments in tectonically low areas. In uplifted blocks, however, the younger erosion destroyed the primary facies pattern and the paragenesis of the deposits changed continually under the influence of later weathering processes. Thus polygenetic soils developed. A scheme of the younger history of the continent is sketched based on a combination of the facies pattern of the bauxite-bearing laterites with the morphogenesis and pedogenesis of the trap-basalt area. This scheme is compared with similar ones from Senegal and Australia.