Comunidades microbianas endoevaporíticas relacionadas con la precipitación de dolomita en ambiente lacustre salino: Mioceno de la Cuenca de Madrid

Abstract

Microbial endoevaporite comunities thrivied in a Miocene saline lake where gypsum crystals were precipitate. As a result of both the survival strategies and the metabolic activities carried out by those communities, the gypsum crystals embedding them were intensely corroded and became, in some cases almost totally, replaced by microbially mediated dolomite. Bore holes in gypsum crystals, either filled or not, with cyanobacteria! remains, and the isotopic composition of the dolomite are, among others, the evidences provided to support this interpretation. The evaporitic unit also comprises marl, mudstone and dolomite layers. The later mainly represent laminar, domal and pustular stromatolites formed by biomineralization of cyanobacteriaI mats. Those processes took place in the different subenvironments of a mudflat-saline lake complex spread out the easternmost part of the Madrid Basin during the Lower Miocene (Lower Aragonian).