Analyse hyperspectrale des carbonates jurassiques dans le Haut Atlas atlantique marocain : exemple du Lias inférieur de la formation d’Arigh Ouzla (bassin d’Essaouira)

Abstract

Nowadays, hyperspectral remote sensing is a powerful tool for discrimination and accurate and rapid identification of mineral surfaces, due to the new technique of ground spectrometry. The objective of this article is the spectral identification of carbonate facies that exist in the Moroccan Atlantic High Atlas mountains, to establish a regional spectral library in order to prepare the implementation of regional maps with high spatial resolution. The spectra acquired in the visible-infrared (0.4 to 2.5 μm) were used for characterizing and monitoring the evolution of diagenetic dolomite from the Lower Lias of the Arigh Ouzla formation that exists in the anticline Jbel Amsitten. The separation of facies, and the taking into account of the diversity in alteration phenomena, have imposed the normalization of the withdrawal of surface effects of dissolution and the restriction of the spectral window to avoid overlap of information. The characteristic absorption bands vary between 2.319 and 2.323 μm and do not change between patina surface and fresh fractures. These values reflect the character totally dolomitic of the facies and can be used to estimate the degree of diagenesis, which gives more details with respect to previous sedimentological and petrographic descriptions. Analysis of the spectra has shown a relationship between the degree of crystallinity and depth of the absorption band could be established.