Laterites - Soils or Sedimentary Rocks?

Andrea Mindszenty - Eötvös University, Budapest

one-day compact course at Sediment 2006, Göttingen (June 6)

Content       Introduction by pictures (pdf)

  1. Soil versus regolith
The problem of the tropical scenario

organic matter quickly destroyed close to the surface
deep weathering (sometimes > 100 m) between top-soil and saprolite
extremely long-lasting pedogenesis

The approach of the geologist

"zone of pedogenesis = the zone of interaction between atmosphere and lithosphere"

2. Phenomenology

- macroscopic and microscopic features, chemistry, photographs of hand-sepcimens and thin sections
- simple tables showing major minerals and chem. components
- process oriented characterization of laterite
- the role of temperature, rainfall, surface relief, drainage, parent rock
- the "lateritic profile", terminology
- top-soil, cuirasse, laterite s.str., lithomarge, relative and absolute accumulation, the position of laterites in the landscape
- the lateritic "catena"
- pedogenic vs groundwater laterite
- isalterite/alloterite, pisolitic laterite
- duricrusts
- the evolution of lateritic profiles as related to the changing relief

3. Lateritization as a time-dependent process

- Age vs duration of lateritization
"old" laterites not in equilibrium with their present position
laterites occurring on young geomorphic surfaces
- The effect of changing environments
laterites occurring in the Sahel - testimonies of climate change
- The "inertia" of the well-developed lateritic profile
-Lateritization and landscape evolution
reorganization of chemical elements (eg. Fe, Al) during long periods of weathering
- Laterites throughout the Earth's history
periods of anomalous abundance of lateritic weathering crusts

4. Special laterites

Bauxites
Iron ores
Manganiferous-laterites
Nickel-laterites

5. Some classical examples

India (Maharashtra, Orissa, Goa)
West Africa (Nigeria)

6. Some less-classical examples

Remnants of Mesozoic-Tertiary laterites in the Tethyan realm