Ciclos climáticos en un sistema lacustre marginal perenne carbonato-evaporítico ( Formación Deza, Eoceno superior, Cuenca de Almazán)

The Deza Formation shows a singular succession in a southern outcrop between Cihuela and Embid. The lower two thirds of the unit are characterised by the abundance of carbonate lacustrine facies alternating with carbonate palustrine ones rich in calcite pseudomorphs after microcrystalline lenticular gypsum, and the presence of lignite in the lower levels of the unit. These facies are arranged in cycles with variable thickness (from 2 to 8 m) consisting of lacustrine fossiliferous marls/soft limestones alternating with palustrine limestone leveIs and shapes of ancient gypsum. These cycles are probably caused by climatic oscillations between humid and dry conditions represented by exposure facies and interstitial gypsum precipitation. The presence of perennial lacustrine facies in this location next to the carbonate Cretaceous paleorelief might be influenced by the abundance of water from springs on this paleorelief. The upper third of the unit consists of a repetition of carbonate palustrine cye/es with some intercalated calcrete levels at the top of the succession. The replacement of gypsum by calcite might occur both during burial and significantly later during uplift and exposure. The petrographic characteristics of the chert nodules indicate an origin that postdates to the calcitization of gypsum.Proyectos BTE2002-04017-C02-02 y CGL2005-05953-C02-01.Peer reviewe