Variación isotópica desde ambientes de llanura lutítico-evaporítica a lago salino efímero (Fm Bordalba, Paleógeno de la cuenca de Almazán)

Resumen

The Bordalba Formation of the Almazán basin is a Palaeogene unit characterised by evaporitic facies belonging to an alluvial fan-playa lake system largely rooted on Mesozoic and Palaeozoic rocks of the Iberian Chain (Aragonian Branch). It includes two main facies associations: dry/saline mud flat association and ephemeral saline lake (playa-lake) association. Gypsum values are consistent with derivation mainly from the dissolution of Upper Triassic evaporites, but a small contribution from oxydized sulphides derived from Palaeozoic metasediments slightly decreased the CDT values of the dry/saline mudflat samples. The ephemeral saline lake samples, on the other hand, have values that are heavier and on average more similar to the Triassic source area. This fact can be attributed to limited sulphate-reduction procceses on an originally similar sulphate reservoir values are much higher in the ephemeral saline lake (around 7%), which has been attributed to the reservoir effect, more enhanced in the evaporitic facies.