Source: https://www.researchgate.net/profile/Hamid-El-Haddi/publication/278826802_The_silicification_of_phosphate_series_of_Ouled_Abdoun_Maastrichtian_Lutetian-Morocco_Sedimentology_Mineralogy_Geochemistry_and_Genetic_Context/links/567293f608ae3aa2fcf0c62a/The-silicification-of-phosphate-series-of-Ouled-Abdoun-Maastrichtian-Lutetian-Morocco-Sedimentology-Mineralogy-Geochemistry-and-Genetic-Context.pdf