Sedimentología y datos preliminares sobre la diagénesis de los niveles con fósiles de vertebrados de Huérmeces del Cerro y Viana de Jadraque (Cuenca del Tajo, Guadalajara)

Resumen

The sedimentologic features of the Palaeogene continental vertebrate-bearing deposits of Huérmeces del Cerro and Viana de Jadraque (Tajo Basin, Guadalajara) and the petrographic features of the fossils are here studied. The vertebrate fossils are preserved in distal alluvial channel infillings, which were deposited in littoral carbonate lacustrine paleoenvironments. The activation of the alluvial channels and the interplay between alluvial and lacustrine systems, which favoured the conservation of the fossil remains, were controlled by the alteration of dry/humid periods due to climate seasonal variations and or synsedimentary tectonic events. The histological structures of the fossil bones are well preserved in both sites, but there is evidence of an alteration of the primary phosphate, which is replaced by late phosphate (secondary francolite) through internal fractures. The fossil bones exhibit a complete carbonate filling. The cathodoluminiscence study suggests that the Huérmeces del Cerro bones were affected by an initial oxidizing diagenetic episode, whereas those of Viana de Jadraque were affected by more reducing conditions.