Resumen de Estimación de la profundidad de enterramiento y deformación compactacional asociada, existentes durante el crecimiento de concreciones carbonatadas de la FM. Rodanas, Tabuenca (Zaragoza)
Francisco Javier Torrijo Echarri, Juan Miguel A. Mandado Collado, F.J. Sanz, M. E. Bona Artazos, Patricia Acero Salazar
Carbonate concretions' subsurface depths and the compaction strain of the Rodanas Formation (Tabuenca) were studied. The concretions contain calcite, clay minerals, detrital quartz and feldespar, and mould of fossils. The cement is micritic-microsparitic calcite. Content in authigenic cement decreases outwards the concretions related to the supply rate of carbonate and the porosity of the rocks. The nucleation and the distribution of concretions into the sediment depend on the shells distribution. They growth until the source of carbonate is consumed.
Concretions' subsurface depths and the compaction strain of formation are deduced directly from estimated porosity values before cementation with calcite. It is concluded that the particular carbonate concretions studied started to grow within the pore space of a lutite-limolite sediment soon after deposition. We calculate a minimun burial depth of formation for concretions of about 500-1.200 m and a minimal compaction strain of about -0'02. These values, with the value of porosity, suggests that concretions are diagenetic and pre-syncompactacional with a mode of emplacement coplacive.
