THE PROGRESSION FROM OPTICAL LIGHT-MICROSCOPY TO TRANSMISSION ELECTRON-MICROSCOPY IN THE STUDY OF SOILS

The use of electron microscopy to study clay microfabrics in thin-sect ions is discussed. A technique is described to isolate undisturbed mic roparts of pedofeatures from thin-sections, which are subsequently use d for TEM analysis. Re-embedding with a polyester resin of undisturbed , in situ, neoformed clay microfabrics, obtained by microdrilling and preparation of ultrathin sections by microtoming with a diamond knife are emphasized; these steps enable micromorphology, clay mineralogy, m icrochemical and HRTEM analysis to be performed on one unique microsam ple of clay fabrics, with conserved microorganization. Two examples on clay neoformation are presented to demonstrate that this technique ca n successfully be applied to unravel the impact of mineral alteration and clay neoformation in undisturbed soil samples on a micro- and a na nometer scale.