Detection and mapping of shrink–swell clays in SW France, using ASTER imagery

Abstract

AbstractCurrent mapping methods for shrink–swell clays in France are based on the use of existing 1:50 000 geological maps. However, stratigraphy is the primary basis of current published geological mapping, which is detrimental to the accurate mapping of clay minerals, argillaceous lithologies and clayey soils. In the study region, Pyrenean forefront molasse deposits have been mapped in a stratigraphy-dominated way, grouped into a single mapping unit, even though they are made up of eight sequences of continental sands, gravels, clays and lacustrine limestones. Mapping shrink–swell clay hazardous terrain can be improved by spectral methods, allowing rapid delineation of argillaceous units and the identification of their mineralogy, especially with regard to illite, chlorite and kaolinite. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) allows a new approach to regional clay mineral mapping, via the six spectral bands in its short-wave infrared domain, particularly wavelengths between 2.145 and 2.43 µm.