The flint dissolution of the clay-with-flints of the western Paris basin

In NW Europe, chalk areas are generally covered with clay-with-flints (CWF) . These formations are made of flints with a clayey or silty-clayey matrix. In the literature devoted to CWF, the flint dissolution during the weather ing of chalk was poorly studied. In this study, we provide an estimation of this phenomenon in the western Paris Basin, by comparisons between the fli nts of CWF and those of chalks based on mineralogy, size, cortex and surfac e cavities of flints. Our results show that the mineralogy and thickness of flints have not been affected by the weathering. Only the volumes of cortex and surface cavities have increased. These two parametres allow us to quantify the flint dissol ution. Flint dissolution is low : the amount of dissolved silica in flints varies between 0.9 and 7.3 %. These low values show that weathering of chal k who has led to the creation of CWF has not reached the intensity of a lat eritic type weathering, as is the case in the ferralitic soil.