viernes, septiembre 16, 2011

Nuevas aportaciones sobre la edad del saurópodo Aragosaurus


Aragosaurus es un dinosaurio saurópodo descrito por José Luis Sanz y colaboradores en 1987 en la localidad turolense de Galve. Tiene el honor de ser el primer dinosaurio definido en España, y además es el nombre de nuestro grupo de investigación. A pesar que lleva más de 30 años publicado quedan lagunas en cuanto a su posición estratigráfica, o dicho de otra manera la antigüedad de los sedimentos donde se encontró. Para dar solución a este problema acabamos de publicar un artículo en la prestigiosa revista Geological Magazine donde se pone al día todos los conocimientos estratigráficos y biocronológicos de los sedimentos donde se encontró Aragosaurus.

El resto de la noticia en Aragosaurus.

El resumen original del trabajo es:
The sauropod Aragosaurus ischiaticus Sanz, Buscalioni, Casanovas & Santafé, 1987 was the first dinosaur to be described in Spain. The holotype was recovered from the site of Las Zabacheras (Galve, Teruel province). This site has traditionally been situated in the El Castellar Formation (in the lower part of the Wealden facies). Recently, it has been proposed that the remains of Aragosaurus stem from the Villar del Arzobispo Formation (late Tithonian–upper part of the early Berriasian), which would mean that the sauropod was almost 15 million years older than previously thought. Detailed field work has been carried out, making it possible to pinpoint the position of the low-angle unconformity between the Villar del Arzobispo Formation and the El Castellar Formation. This unconformity originated as a result of block tilting that occurred during the early stages of the Early Cretaceous rifting episode. The upper levels of the Jurassic sequence (i.e. the Villar del Arzobispo Formation) were exposed to erosion and karstification, leading to the formation of a discontinuous conglomeratic level. This level has been locally preserved at the bottom of the Wealden syn-rift sequence (i.e. the El Castellar Formation). The results of our detailed mapping demonstrate that the Aragosaurus holotype was found in the lower part of the El Castellar Formation. Moreover, our revision of the existing datings suggests that the El Castellar Formation as a whole is Valanginian?–early Barremian in age. Given that Aragosaurus was located in its lower part, it is probably Valanginian?–Hauterivian in age.