Neoformaciones y reemplazamientos en depósitos palustres de la Unidad Intermedia (NE de la Cuenca de Madrid)

Abstract

The NE zone of the Madrid Basin contains palustrine deposits of the Miocene Intermediate Unit which have undergone silicification processes. These processes are conditioned by the type of palustrine deposit within they developed and occur at specific stratigraphic positions in the basin. In this paper we analyze three different sectors. In the Yesares section silicification produced quartz and took place in gypsum deposits which contain bioturbation channels that favoured silica fixation. In the Brihuega area silicification on bioturbated palustrine micrites also produced quartz. Both silicifications appear at the top of unit or sequence of the Intermediate Unit. In the Jadraque section the silicification of the micrites and dolomicrites was controlled by the presence of biosiliceous marls and sepiolite. This silicification was consequence of early diagenesis.