[ES] En el NW de la Cuenca Terciaria del Tajo existe una potente sucesión carbonático-detrítica de edad paleógena que presenta una gran diversidad de facies carbonáticas. A partir del estudio detallado de 12 secciones estratigráficas (ARRIBAS, 1985), dichas facies han sido agrupadas en dos familias litológicas, carbonatos consolidados y carbonatos no consolidados. Dentro del grupo de carbonatos consolidados se han diferenciado: ca/izas homogéneas (calizas fosilíferas, calizas intraclásticas, calizas laminadas y calizas dolomíticas-dolomías) y calizas alteradas (calizas nodulosas, calizas nodulosas con terrígenos, calizas bioturbadas, calizas con estructuras prismáticas verticales, calizas oquerosas y calizas con laminación deformada y porosidad fenestral). A su vez, se han distinguido cuatro facies petrológicas dentro de los carbonatos no consolidados: margas, margas dolomíticas, ‘

[EN] In the NW sector of the Tertiary Tajo Basin (Fig. 1-2) a carbonate and detrital successíon of paleogene age, showing many carbonate facies is found. Starting from a detailed study of twelve stratigraphic sections (ARRIBAS, 1985 y 1986), these carbonate facies and been assembled in two principal groups: hard carbonates and powdery carbonates (Fig. 3). Within the hard carbonate facies two groups of limestones are distinguished: hornogeneaus limestones (fosiliferous Iimestones, intraclastic limestones, limestones with oncolites and/or algues, limestones with terrigenous, laminated limestones aud dolomitic limestones-dolostones) and disturbed Umestones (nodular limestones, nodular sandy limestones, bioturbated limestones, limestones with vertical prismatie structures, vuggy limestones, and limestones with deformed lamination and fenestral porosity). Within powdery carbonate facies four petrological facies are distinguished: marís, dolomitic marís, chalks and dolomitie chalks. I-lomogeneous limestones are generally interpreted as littoral lacustrine sediments and disturbed limestones are interpíeted as the result of several pedogenetic processes both in the palustrine zone (depositional lacustrine systems) and in the flood-plain zone (depositional aluvial and fluvial systems) (Fig. 4). Carbonate facies are related with other lithological facies (carbonate or detrital) in facies associations can show different sedimentological evolutions of the lacustrine basin as expansions or retraetions (Fig. 5). The sequencial analysis of these facies associations allow to establish an evolution of the sedimentation along the carbonate-detrital paleogene succession froni lacustrine carbonate facies at the bottom up to aluvial —fan terrigenous facies at the top.

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