Las formaciones yesíferas del Triásico Superior y Jurásico Inferior de Camarasa, en el frente Surpirenaico Catalán

Abstract

The present study describes the lithostratigraphic characteristics of the Canelles Gypsum Formation (lower Keuper) and the Lécera Gypsum Formation (Lower Jurassic) in the area of Camarasa, in the Catalan South Pyrenean front. The Lécera Formation forms a cyclic alternation of gypsum and carbonate layers of about 300 m thick. Gypsum displays gray laminated, white laminated, and white massive lithofacies. Carbonate forms minor layers of dolobreccia and thin bedded dolomicrite lithofacies. On the contrary, the Canelles Formation forms a 100 m thick massive sequence mainly composed of white and brown laminated gypsum, with carbonate layers restricted to the base of the formation and to its middle part. On the base, the carbonate layers consist of laminated dolomicrite lithofacies, while in the middle part they display laminated dolomarl, thin bedded dolomicrite and oolitic lithofacies, which are arranged in four carbonatic cycles of few meters thick. Both formations originated in similar evaporitic environments of very stable sulfate lagoons fed by sea water and away from the influence of detrital inputs. In such lagoons sedimentation mainly consisted of laminated gypsum with minor carbonate beds, representing sediments of relatively high and low concentration of the lagoon water respectively, but without precipitation of more soluble salts (halite).