Resumen de Origen de las concreciones carbonatadas del Cerro de la Torre, Muel (Zaragoza)
Francisco Javier Torrijo Echarri, Juan Miguel A. Mandado Collado, F.J. Sanz, M. E. Bona Artazos, Patricia Acero Salazar
Carbonate concretions of the miocene deposits in the "Cerro de la Torre" hill (Muel-Zaragoza) were studied. The concretions are included in limestones and mudstones, and contain calcite, opaque minerals, monocristaline detrital quartz and organic matter; and corporal fossils of Planorbis. The cement is micritic calcite (<5 pm). Content in authigenic cement decreases outwards the concretions related to the supply rate of carbonate. The carbonate concretions are developed at certain horizons within the carbonate rocks, where the fossils shells provided nuclei. Thus, the nucleation and the distribution of concretions into the sediment depend on the shells distribution. The cement-forming component come from the dissolved of aragonitic shells that only its are preservated in the interior of carbonate concretions. They growth until the supersaturation range isn't suficiently raised to calcite precipitation. The negative tendency of Mn/Fe relation suggests a increase in subsurface depth. A postcompactacional model, and a replacive growth are proposed.
