Análisis secuencial del delta de Erts. Estratigrafía de un valle glacial obturado intermitentemente. Relación con el último ciclo glaciar. Valle de Arinsal, Pirineos Orientales

(SPA) En el valle de Arinsal se desarrolló una sedimentación flúvioglaciar y glaciolacustre durante la deglaciación del último ciclo glaciar en los Pirineos. El valle estuvo obturado de forma intermitente por el avance del glaciar del valle principal (Valira del Nord) generando subidas y bajadas del nivel de base local. Un afloramiento excepcional en las cercanías del pueblo de Erts ha permitido identificar facies turbidíticas, deltaicas y glaciares. El estudio detallado del afloramiento y la correlación de éste con otros 30 afloramientos a lo largo de 5 Km ha permitido efectuar un análisis de la cuenca utilizando la estratigrafía secuencial. Se presenta en esta comunicación las particularidades del medio sedimentario estudiado que se encuentra en un contexto glaciar continental confinado. (ENG) At the NW part of the Principality of Andorra we can distinguish two valleys, the Arinsal valley where is the highest mountain of Andorra (Coma Pedrosa peak, 2942 m a.s.l) and the Ordino valley, both valleys converge in La Massana village (1250 m a.s.l). The Pleistocene glaciolacustrine basin of La Massana has been studied by some authors. One of the most important outcrops of the Arinsal valley is situated near the Erts village (1300 m a.s.l), in which we find at the bottom turbiditic facies overlayered by deltaic deposits and glacial materials at the top of the outcrop, that shows a close relationship with an synsedimentary obturation of the valley by the advance of the principal glacier (from Ordino valley). The seismic stratigraphy depositional sequences has been used as a tool to realise a basin analysis of the Arinsal glaciolacustrine deposits. A new type 3 unconformity and a type 3 a epositional sequence has been defined for this kind of depositional environment, so a glaciolacustrine and glaciofluvial sedimentation in a continental place (Pyrenees Mountains) and in a confined site (glacial valley), and is characterised by an erosion-sedimentation of an subglacial till and the deposit of only an TST and a HST.