Caracterización y origen de las estructuras prismáticas de paleosuelos dolomíticos. Paracuellos de Jarama. Mioceno, Cuenca de Madrid

Résumé

In this work, we discuss the origin of the prismatic structures of the dolocretes of Paracuellos de Jarama area. These structures are vertical nodules or peds, formed by smaller order peds. All the peds are delimited by intercalations of mudstones. The peds are dolomitic and have narrow and elongate cracks, which occasionally have dolomitic drusy cements. The intercalations of mudstone are mainly smectites with sepic fabrics and have important channel porosity. Agglutinated lutites, cutans, silicified plant remains, fragments of dolomicrite and equidimensional dolomite crystals are found in the porosity. The prismatic structures are the products of carbonate formation during the metabolic activity of rhizosphere ́s microorganisms and roots of the plants that colonized the original substrate during periods of low sedimentation. The fact that all the carbonate is only dolomite is due to the high availability of Mg in this alkaline environment, favoured by the presence of trioctahedral smectites and organic material.