Ciclos climáticos en un sistema lacustre marginal perenne carbonatado-evaporíticoformación Deza, Eoceno superior cuenca de Almazán

Resumen

The Deza Foramation shows a singular succesion in a southern outcrop between Cihuela and Embid. The lower two thirds of the unit are characteristed by the abundance of crbonate 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 levels and shapes of ancient gypsum. These cycles are probably caused by climatic oscillations between humid and dry conditions represented by exposures 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 consist of a repetition of carbonate palustrine cycles with some intercalated calcrete levels at the top of the succesion. The replacement of gypsum by calcite might occur both during burial or significantly later during uplift and exposure. The petrographic characteristics of the chert nodules an origin that postdates to the calcitization of gypsum.