Nueva publicación sobre el paleoambiente de Lo Hueco

Un nuevo análisis (que está siendo publicado en la revista Facies) sobre los sedimentos depositados en el yacimiento del Cretácico Superior de “Lo Hueco” (Fuentes, Cuenca) permite ajustar un poco mejor la interpretación del medio en el que vivieron los dinosaurios que habitaban la zona hace 75 millones de años. La estructura del yacimiento apunta a un medio continental con influencia marina en el que es frecuente la presencia de aguas salobres.

Las capas del yacimiento en las que se depositaron yesos se formaron probablemente en una marisma salobre de un lago playa próximo a la costa. Estos datos confirman de forma independiente la interpretación paleoambiental que tanto la fauna como la flora habían facilitado.

El resumen es el siguiente:

“Lo Hueco” (Cuenca, Spain) is an upper Campanian–lower Maastrichtian Fossil-Lagerstätte that has provided more than 8,500 well-preserved macrofossils, including titanosaur sauropod dinosaurs. Although the facies and fossil record point to both fresh and brackish or marine water influences, a detailed study of the sulphate-bearing layers of the site through petrography, fluid inclusions, and isotopes has been undertaken to evaluate the possible marine influence. The two main sulphate units of the “Lo Hueco” site consist chiefly of bimodal micro- to meso- lenticular gypsum crystals that grew displacively in a clayey-carbonate sediment. The well-preserved lenticular gypsum crystals are primary, as demonstrated by the presence of the original twinning and the absence of hydration textures or anhydrite relicts. Primary fluid inclusions of the lenticular gypsum crystals indicate a vadose environment of formation, with salinities between 1,800 and 14,000 ppm, pointing to a brackish but non-marine environment. Furthermore, gypsum exhibits 87Sr/86Sr values between 0.708034 and 0.708120, which are higher than those from marine evaporites of Campanian–Maastrichtian age, indicating a clear influence of fresh water. Gypsum δ 34S VCDT values (18.1 to 19.0 ± 0.5 ‰) and δ 18OVSMOW values (11.0 to 15.2 ± 0.5 ‰), on the other hand, are typical isotopic values recorded in marine evaporites of this age. This apparent contradiction between fluid inclusion and Sr isotopic data is probably the result of some recycling from Upper Cretaceous evaporites. Based on all these observations, the sulphate-bearing layers are interpreted as probably formed in a near-coastal saline mudflat of a playa lake. As a whole, this study highlights the importance of combining different proxies when dealing with evaporites formed in brackish-water environments.

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Mas información:

• Referencia: González-Acebrón, L. et al., 2014. Environmental significance of gypsum-bearing layers at the “Lo Hueco” paleontological site (Upper Cretaceous, Cuenca, Spain): petrography, fluid inclusions, and isotopic relations. Facies.
• La imagen muestra una marisma actual en la se han empotrado algunos animales del Cretácico Superior como un rebaño de titanosaurios tomado de aquí